3n4LmrMd

1deflector flowmeter
21.n. [Production Logging]
3A device for measuring in-situ the velocity of fluid flow in a production or injection well in which the total fluid flow is diverted to pass over an impeller, or spinner. Various techniques have been used to achieve this, one of the earliest being the packer flowmeter. In a typical modern device, the diverter consists of a fabric in a metal cage that is collapsed to pass through the tubing and other restrictions. Below the tubing, the cage is opened until an inflatable ring seals against the casing wall. At this point, the up-going production fluids are forced through the diverter and over an impeller. This ensures that the total casing flow is measured, but may also create an extra pressure drop and hence a change in multiphase flow structure.The diverter flowmeter is particularly suitable for low flow rates in vertical or moderately deviated wells. Readings are made with the tool stationary.
4flow-concentrating, injection well, multiphase flow, packer flowmeter, production log, spinner flowmeter, torque flowmeter
5diverter flowmeter
6None
7--
8deviated drilling
91.n. [Shale Gas, Drilling]
10The intentional deviation of a wellbore from the path it would naturally take. This is accomplished through the use of whipstocks, bottomhole assembly (BHA) configurations, instruments to measure the path of the wellbore in three-dimensional space, data links to communicate measurements taken downhole to the surface, mud motors and special BHA components and drill bits, including rotary steerable systems, and drill bits. The directional driller also exploits drilling parameters such as weight on bit and rotary speed to deflect the bit away from the axis of the existing wellbore. In some cases, such as drilling steeply dipping formations or unpredictable deviation in conventional drilling operations, directional-drilling techniques may be employed to ensure that the hole is drilled vertically. While many techniques can accomplish this, the general concept is simple: point the bit in the direction that one wants to drill. The most common way is through the use of a bend near the bit in a downhole steerable mud motor. The bend points the bit in a direction different from the axis of the wellbore when the entire drillstring is not rotating. By pumping mud through the mud motor, the bit turns while the drillstring does not rotate, allowing the bit to drill in the direction it points. When a particular wellbore direction is achieved, that direction may be maintained by rotating the entire drillstring (including the bent section) so that the bit does not drill in a single direction off the wellbore axis, but instead sweeps around and its net direction coincides with the existing wellbore. Rotary steerable tools allow steering while rotating, usually with higher rates of penetration and ultimately smoother boreholes.Directional drilling is common in shale reservoirs because it allows drillers to place the borehole in contact with the most productive reservoir rock.
11directional driller, directional well, geosteering, horizontal drilling, mud motor, slide, steerable motor
12directional drilling
13None
14--
15displacement fluid
161.n. [Drilling]
17The fluid, usually drilling mud, used to force a cement slurry out of the casing string and into the annulus.
18casing string, displacement, drilling mud
19None
20None
21--
22drilling rate
231.n. [Drilling]
24The speed at which the drill bit can break the rock under it and thus deepen the wellbore. This speed is usually reported in units of feet per hour or meters per hour.
25antiwhirl bit, drill bit
26None
27None
28--
29deflocculant
301.n. [Drilling Fluids]
31A thinning agent used to reduce viscosity or prevent flocculation; incorrectly called a "dispersant." Most deflocculants are low-molecular weight anionic polymers that neutralize positive charges on clay edges. Examples include polyphosphates, lignosulfonates, quebracho and various water-soluble synthetic polymers.
32acrylamide polymer, acrylate polymer, Bingham plastic model, bland coring fluid, carbonate ion, chrome lignosulfonate, chrome-free, clay-water interaction, conventional mud, deflocculated mud, direct-indicating viscometer, drill solids, gel strength, gyp mud, kill-weight fluid, lignin, lignite, lignosulfonate, phosphate salt, plastic viscosity, polar compound, polymer, red mud, rheology, SAPP, sulfonated polystyrene-maleic anhydride copolymer, tannic acid, tannin, yield point
33thinner
34Antonyms:flocculant
35--
36deviated hole
371.n. [Drilling]
38A wellbore that is not vertical. The term usually indicates a wellbore intentionally drilled away from vertical.
39casing centralizer, centralizer, crooked hole, hydrostatic head, inclination, jet, logging while drilling
40None
41None
42--
43disposal well
441.n. [Well Completions]
45A well, often a depleted oil or gas well, into which waste fluids can be injected for safe disposal. Disposal wells typically are subject to regulatory requirements to avoid the contamination of freshwater aquifers.
46aquifer
47None
48None
49--
50drilling rig
511.n. [Drilling]
52The machine used to drill a wellbore. In onshore operations, the rig includes virtually everything except living quarters. Major components of the rig include the mud tanks, the mud pumps, the derrick or mast, the drawworks, the rotary table or topdrive, the drillstring, the power generation equipment and auxiliary equipment. Offshore, the rig includes the same components as onshore, but not those of the vessel or drilling platform itself. The rig is sometimes referred to as the drilling package, particularly offshore.
53rig up
54rig
55None
56--
57deflocculated mud
581.n. [Drilling Fluids]
59A clay-based, water mud that has had its viscosity reduced with a chemical treatment; incorrectly, called a "dispersed" mud. The chemical used is a deflocculant, not a dispersant. A well-known and effective clay deflocculant is lignosulfonate. The mud, after being deflocculated, usually shows much improved filter-cake qualities with lower yield point and gel strengths. Filter-cake quality is improved because when clays are deflocculated, the platelets become detached from each other and can lie flat to form a thin, low-permeability filter cake. Lowering yield point and gel strength may not always be desired and can be adjusted by the amount of deflocculant added in each treatment. If yield point and gels are lowered too far, suspension and cutting capacity of the mud are impaired.
60acrylate polymer, calcium contamination, carbonate ion, chromate salt, clay-water interaction, filter cake, gel strength, lignite, quebracho, water mud, yield point
61None
62None
63--
64deviation survey
651.n. [Drilling]
66A completed measurement of the inclination and azimuth of a location in a well (typically the total depth at the time of measurement). In both directional and straight holes, the position of the well must be known with reasonable accuracy to ensure the correct wellbore path and to know its position in the event a relief well must be drilled. The measurements themselves include inclination from vertical, and the azimuth (or compass heading) of the wellbore if the direction of the path is critical. These measurements are made at discrete points in the well, and the approximate path of the wellbore computed from the discrete points. Measurement devices range from simple pendulum-like devices to complex electronic accelerometers and gyroscopes used more often as MWD becomes more popular. In simple pendulum measurements, the position of a freely hanging pendulum relative to a measurement grid (attached to the housing of the tool and assumed to represent the path of the wellbore) is captured on photographic film. The film is developed and examined when the tool is removed from the wellbore, either on wireline or the next time pipe is tripped out of the hole.
67survey
68directional survey
69None
70--
71dissolved solids
721.n. [Drilling Fluids]
73In water analysis, the soluble components in a sample or the residue left after evaporation of a sample. Dissolved solids are reported as ppm or mg/L. Dissolved solids are included in retort solids and can be calculated from chemical analysis results by assuming that all dissolved solids are either NaCl or CaCl2, or a mixture of the two.
74calcium test, chloride test, milligrams per liter, ppm, retort solids, suspended solids, water, oil and solids test
75None
76None
77--
78drill noise vertical seismic profile
791.n. [Geophysics]
80A technique for acquiring a verticalseismicprofile that uses the noise of the drill bitas a source and receivers laid out along the ground or seabed. In deep water, the receiver arrays can be deployed vertically. Acquisition andprocessingare typically more challenging than in the more conventional types of VSPs, but the technique can yield time-depth information and, less frequently, reflection information, while the well is being drilled. The information from a drill-noise VSP can be used to improve time-depth conversions while drilling, decide where to setcasingin a well and evaluate drilling hazards, such asanomalouspore pressure.
81acquisition, noise, receiver, reflection, source, vertical seismic profile
82None
83None
84--
85defoaming plates
861.n. [Production Facilities]
87In a separator, a series of inclined parallel plates or tubes to promote coalescence, or merging, of the foam bubbles liberated from the liquid.
88None
89None
90None
91--
92dew point
931.n. [Well Testing, Enhanced Oil Recovery]
94Thepressureat which the firstcondensateliquid comes out of solution in a gas condensate. Many gas condensate reservoirs are saturated at initial conditions, meaning that the dewpoint is equal to the initialreservoir pressure. Condensate dissolution is called retrograde condensation because this is counter to the behavior of pure substances, which vaporize when the pressure drops below thesaturationpressure under isothermal (constant temperature) conditions.
95gas condensate, initial reservoir pressure, retrograde condensation
96None
97None
98--
99distortion
1001.n. [Geophysics]
101The inability of a system to exactly match input and output, a general example being an electronic amplifier and the classic example being a home stereophonic amplifier.
102bias, dispersion, dynamic range, harmonic distortion, zero-phase
103amplitude distortion
104None
105--
106distortion
1072.n. [Geophysics]
108A change in a waveform that is generally undesirable, such as in seismic waves.
109seismic wave
110None
111None
112--
113drillpipe
1141.n. [Drilling]
115Tubular steel conduit fitted with special threaded ends called tool joints. The drillpipe connects the rig surface equipment with the bottomhole assembly and the bit, both to pump drilling fluid to the bit and to be able to raise, lower and rotate the bottomhole assembly and bit.
116bottomhole assembly, circulation system, drilling fluid, drillstem, drillstring, joint, tool joint
117None
118None
119--
120dehydrate
1211.vb. [Production Facilities]
122To remove water from a substance. The substance may be crude oil, natural gas or natural gas liquids (NGL).Fluid dehydration is needed to prevent corrosion and free-water accumulation in the low points of a pipeline. In the case of gas, it is especially important to avoid hydrate formation and also to meet pipeline requirements. Typical maximum allowable water vapor content is 7 pounds of water per million standard cubic feet. In colder climates, this threshold value could be 3 to 5 pounds per million standard cubic feet. Water vapor can also affect the sweetening and refining processes of a natural gas.Dehydration of crude oil is normally achieved using emulsion breakers, while gas dehydration is accomplished using various liquid desiccants such as glycols (ethylene, diethylene, triethylene and tetraethylene) or solid desiccants such as silica gel or calcium chloride [CaCl2].
123calcium chloride, crude oil, dehydrator, dry-bed dehydrator, free water, glycol, glycol dehydrator, natural gas, natural gas liquids
124None
125None
126--
127dewpoint
1281.n. [Enhanced Oil Recovery, Well Testing]
129The pressure at which the first condensate liquid comes out of solution in a gas condensate. Many gas condensate reservoirs are saturated at initial conditions, meaning that the dewpoint is equal to the initial reservoir pressure. Condensate dissolution is called retrograde condensation because this is counter to the behavior of pure substances, which vaporize when the pressure drops below the saturation pressure under isothermal (constant temperature) conditions.
130gas condensate, initial reservoir pressure, retrograde condensation
131None
132None
133--
134distributed temperature log
1351.n. [Production Logging]
136A record of the change in temperature along a well, normally recorded by a fiber-optic cable. The distributed temperature is measured by sending a pulse of laser light down the optical fiber. Molecular vibration, which is directly related to temperature, creates weak reflected signals. These signals are detected at the surface and converted to a log of temperature along the well, sampled approximately every 1 m [3.28 ft] with a resolution of 0.1oC. The fiber-optic cable is normally installed at the time of well completion, so that the distributed-temperature log can be recorded at any later time without well intervention.Introduced in the mid-1990s, the technique can also be used to measure flow rates by creating a temperature transient and observing its movement along the well.
137flowmeter, production log, temperature log, well flow rate
138None
139None
140--
141drillpipe conveyed
1421.adj. [Formation Evaluation]
143Describing sensors that are embedded in drill collars in order to record measurements-while-drilling.
144drill collar, logging tool, telemetry
145None
146None
147--
148drillpipe conveyed
1492.adj. [Formation Evaluation]
150Pertaining to the use of drillpipe to move wireline logging tools up and down a borehole. In difficult conditions--high well deviation, rough hole--wireline logging tools cannot reach the bottom of the hole under their own weight. In drillpipe-conveyed logging operations, the tools are moved mechanically by the drillpipe, while a wireline maintains the electrical connection.
151cable
152None
153None
154--
155dehydration
1561.n. [Drilling Fluids]
157The loss of water from cement slurry or drilling fluid by the process of filtration. Dehydration results in the deposition of a filter cake and loss of the slurrys internal fluid into a porous matrix. The cement is not completely dehydrated because sufficient water remains to allow setting of the cement.
158drilling fluid, filter cake
159None
160None
161--
162diagenesis
1631.n. [Geology]
164The physical, chemical or biological alteration of sediments into sedimentary rock at relatively low temperatures and pressures that can result in changes to the rock's original mineralogy and texture. After deposition, sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals that precipitate from solution. Grains of sediment, rock fragments and fossils can be replaced by other minerals during diagenesis. Porosity usually decreases during diagenesis, except in rare cases such as dissolution of minerals and dolomitization. Diagenesis does not include weathering processes. Hydrocarbon generation begins during diagenesis. There is not a clear, accepted distinction between diagenesis and metamorphism, although metamorphism occurs at pressures and temperatures higher than those of the outer crust, where diagenesis occurs.
165authigenic, cement, cementation, chlorite, compaction, diagenetic porosity, dolostone, lithification, overmature, post-mature, reef, secondary porosity, stylolite
166None
167None
168--
169diagenesis
1702.n. [Shale Gas, Geology]
171The initial stage of alteration of sediments and maturation of kerogen that occurs at temperatures less than 50°C [122°F]. The type of hydrocarbon generated depends on the type of organic matter in the kerogen, the amount of time that passes, and the ambient temperature and pressure. During early diagenesis, microbial activity is a key contributor to the breakdown of organic matter and generally results in production of biogenic gas. Longer exposure to higher temperatures during diagenesis, catagenesis, and metagenesis generally results in transformation of the kerogen into liquid hydrocarbons and hydrocarbon gases.
172None
173None
174None
175--
176distributed temperature log
1771.n. [Production Logging]
178A record of the change in temperature along a well, normally recorded by a fiber-optic cable. The distributed temperature is measured by sending a pulse of laser light down the optical fiber. Molecular vibration, which is directly related to temperature, creates weak reflected signals. These signals are detected at the surface and converted to a log of temperature along the well, sampled approximately every 1 m [3.28 ft] with a resolution of 0.1oC. The fiber-optic cable is normally installed at the time of well completion, so that the distributed-temperature log can be recorded at any later time without well intervention.Introduced in the mid-1990s, the technique can also be used to measure flow rates by creating a temperature transient and observing its movement along the well.
179flowmeter, production log, temperature log, well flow rate
180None
181None
182--
183drillship
1841.n. [Drilling]
185A maritime vessel modified to include a drilling rig and special station-keeping equipment. The vessel is typically capable of operating in deep water. A drillship must stay relatively stationary on location in the water for extended periods of time. This positioning may be accomplished with multiple anchors, dynamic propulsion (thrusters) or a combination of these. Drillships typically carry larger payloads than semisubmersible drilling vessels, but their motion characteristics are usually inferior.
186dynamic positioning, moon pool
187None
188None
189--
190delay rental
1911.n. [Oil and Gas Business]
192Consideration paid to the lessor by a lessee to extend the terms of an oil and gas lease in the absence of operations and/or production that is contractually required to hold the lease. This consideration is usually required to be paid on or before the anniversary date of the oil and gas lease during its primary term, and typically extends the lease for an additional year. Nonpayment of the delay rental in the absence of production or commencement of operations will result in abandonment of the lease after its primary term has expired.
193oil and gas lease, primary term, secondary term
194None
195None
196--
197diagenetic
1981.adj. [Geology]
199Pertaining to diagenesis, which is the physical, chemical or biological alteration of sediments into sedimentary rock at relatively low temperatures and pressures that can result in changes to the rock's original mineralogy and texture. After deposition, sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals that precipitate from solution. Grains of sediment, rock fragments and fossils can be replaced by other minerals during diagenesis. Porosity usually decreases during diagenesis, except in rare cases such as dissolution of minerals and dolomitization. Diagenesis does not include weathering processes. Hydrocarbon generation begins during diagenesis. There is not a clear, accepted distinction between diagenesis and metamorphism, although metamorphism occurs at pressures and temperatures higher than those of the outer crust, where diagenesis occurs
200authigenic, cement, compaction, diagenetic porosity, dolostone, lithification, secondary porosity, stylolite
201None
202None
203--
204diverter flowmeter
2051.n. [Production Logging]
206A device for measuring in-situ the velocity of fluid flow in a production or injection well in which the total fluid flow is diverted to pass over an impeller, or spinner. Various techniques have been used to achieve this, one of the earliest being the packer flowmeter. In a typical modern device, the diverter consists of a fabric in a metal cage that is collapsed to pass through the tubing and other restrictions. Below the tubing, the cage is opened until an inflatable ring seals against the casing wall. At this point, the up-going production fluids are forced through the diverter and over an impeller. This ensures that the total casing flow is measured, but may also create an extra pressure drop and hence a change in multiphase flow structure.The diverter flowmeter is particularly suitable for low flow rates in vertical or moderately deviated wells. Readings are made with the tool stationary.
207flow-concentrating, injection well, multiphase flow, packer flowmeter, production log, spinner flowmeter, torque flowmeter
208deflector flowmeter
209None
210--
211drillstem test
2121.n. [Drilling]
213A procedure to determine the productive capacity, pressure, permeability or extent (or a combination of these) of a hydrocarbon reservoir. While several different proprietary hardware sets are available to accomplish this, the common idea is to isolate the zone of interest with temporary packers. Next, one or more valves are opened to produce the reservoir fluids through the drillpipe and allow the well to flow for a time. Finally, the operator kills the well, closes the valves, removes the packers and trips the tools out of the hole. Depending on the requirements and goals for the test, it may be of short (one hour or less) or long (several days or weeks) duration and there might be more than one flow period and pressure buildup period.
214barefoot, flow period, kill, packer, pressure buildup, safety joint, trip out
215None
216DST
217--
218drillstem test
2192.n. [Well Testing]
220Well tests conducted with the drillstring still in the hole. Often referred to as DST, these tests are usually conducted with a downhole shut-in tool that allows the well to be opened and closed at the bottom of the hole with a surface-actuated valve. One or more pressure gauges are customarily mounted into the DST tool and are read and interpreted after the test is completed. The tool includes a surface-actuated packer that can isolate the formation from the annulus between the drillstring and the casing, thereby forcing any produced fluids to enter only the drillstring. By closing in the well at the bottom, afterflow is minimized and analysis is simplified, especially for formations with low flow rates. The drillstring is sometimes filled with an inert gas, usually nitrogen, for these tests. With low-permeability formations, or where the production is mostly water and the formation pressure is too low to lift water to the surface, surface production may never be observed. In these cases, the volume of fluids produced into the drillstring is calculated and an analysis can be made without obtaining surface production. Occasionally, operators may wish to avoid surface production entirely for safety or environmental reasons, and produce only that amount that can be contained in the drillstring. This is accomplished by closing the surface valve when the bottomhole valve is opened. These tests are called closed-chamber tests.Drillstem tests are typically performed on exploration wells, and are often the key to determining whether a well has found a commercial hydrocarbon reservoir. The formation often is not cased prior to these tests, and the contents of the reservoir are frequently unknown at this point, so obtaining fluid samples is usually a major consideration. Also, pressure is at its highest point, and the reservoir fluids may contain hydrogen sulfide, so these tests can carry considerable risk for rig personnel.The most common test sequence consists of a short flow period, perhaps five or ten minutes, followed by a buildup period of about an hour that is used to determine initial reservoir pressure. This is followed by a flow period of 4 to 24 hours to establish stable flow to the surface, if possible, and followed by the final shut-in or buildup test that is used to determine permeability thickness and flow potential.
221bottomhole shut-in, buildup test, closed-chamber testing, DST, final shut-in period, flow period, formation pressure, hydrogen sulfide, packer, permeability thickness, pressure gauge, produced fluid, reservoir pressure
222None
223None
224--
225deliverability test
2261.n. [Production Testing]
227Tests in an oil or gas well to determine its flow capacity at specific conditions of reservoir and flowing pressures. The absolute open flow potential (AOFP) can be obtained from these tests, and then the inflow performance relationship (IPR) can be generated. A deliverability test also is called a productivity test.
228absolute open flow potential, AOFP, flowing pressure, inflow performance relationship, IPR, reservoir pressure
229productivity test
230None
231--
232diagenetic porosity
2331.n. [Geology]
234A type of secondary porosity created during diagenesis, commonly through dissolution or dolomitization or both. Diagenesis usually destroys porosity, so diagenetic porosity is rare.
235diagenesis, dolomitization, porosity, secondary porosity
236None
237None
238--
239dix formula
2401.n. [Geophysics]
241An equation used to calculate the interval velocity within a series of flat, parallel layers, named for American geophysicist C. Hewitt Dix (1905 to 1984). Sheriff (1991) cautions that the equation is misused in situations that do not match Dix's assumptions. The equation is as follows:Vint = [(t2 VRMS22 − t1 VRMS12) / (t2 − t1)]1/2,whereVint = interval velocityt1 = traveltime to the first reflectort2 = traveltime to the second reflectorVRMS1 = root-mean-square velocity to the first reflectorVRMS2 = root-mean-square velocity to the second reflector.Reference: Dix CH: "Seismic Velocities from Surface Measurements," Geophysics 20, no. 1 (January 1955): 68–86.
242interval velocity, reflector, root-mean-square velocity, traveltime
243None
244None
245--
246drip
2471.n. [Production Facilities]
248A small vessel in a pipeline to receive water and heavy hydrocarbons that drop out of a gas stream. Drips are normally installed in the lower points of flow lines and must be blown periodically to remove liquids.
249blowing the drip, flowline
250None
251None
252--
253drip
2542.n. [Production Testing]
255The water and heavy hydrocarbons that condense from the gas stream and accumulate in the lower points of the flowlines.
256None
257None
258None
259--
260delta
2611.n. [Geology]
262An area of deposition or the deposit formed by a flowing sediment-laden current as it enters an open or standing body of water, such as a river spilling into a gulf. As a river enters a body of water, its velocity drops and its ability to carry sediment diminishes, leading to deposition. The term has origins in Greek because the shape of deltas in map view can be similar to the Greek letter delta. The shapes of deltas are subsequently modified by rivers, tides and waves. There is a characteristic coarsening upward of sediments in a delta. The three main classes of deltas are river-dominated (Mississippi River), wave-dominated (Nile River), and tide-dominated (Ganges River). Ancient deltas contain some of the largest and most productive petroleum systems.
263depositional environment, petroleum system, sediment
264None
265None
266--
267delta
2682.n. [Geophysics]
269An anisotropy parameter that describes near-vertical P-wave velocity anisotropy and the difference between the vertical and small-offset moveout velocity of P-waves.δ = ½{[(C13 + C44)2 − (C33 − C44)2] / [C33 (C33 − C44)]}Anisotropy parameter for near-vertical P-waves. Delta (δ) describes near-vertical P-wave velocity anisotropy and the difference between the vertical and small-offset moveout velocity of P-waves. C33 is the vertical P-wave modulus (parallel to the symmetry axis), C44 is the modulus for a vertically traveling and horizontally polarized S-wave (parallel to the symmetry axis) and C13 is the modulus of dilation in the vertical direction induced by compression in the horizontal direction.Reference: Thomsen L: “Weak Elastic Anisotropy,” Geophysics 51, no. 10 (October 1986): 1954–1966.
270epsilon (ε), gamma (γ), eta (η)
271None
272None
273--
274diameter of invasion
2751.n. [Formation Evaluation]
276The distance from the borehole wall into the formation that the mud filtrate has penetrated. The term assumes equal invasion on all sides of the borehole. It is the diameter of the circle thus formed, with the center being the center of the borehole. The diameter of invasion affects whether a log measures the invaded zone, the undisturbed zone, or part of each zone. The term is closely related to the depth of invasion, being twice the depth of invasion plus the borehole diameter. Diameter of invasion is a more appropriate parameter for describing the response of azimuthally symmetric measurements such as induction, laterolog and propagation resistivity.The term is well-defined in the case of a step profile of invasion. In the case of an annulus or a transition zone, two diameters must be defined, corresponding to the inner and outer limits of the annulus or transition zone. When the invasion model is not specified, the term usually refers to the outer limit of invasion.
277azimuthal, depth of invasion, filtrate slump, flushed zone, propagation resistivity, step profile, transition zone
278None
279None
280--
281dog house
2821.n. [Drilling]
283The steel-sided room adjacent to the rig floor, usually having an access door close to the driller's controls. This general-purpose shelter is a combination tool shed, office, communications center, coffee room, lunchroom and general meeting place for the driller and his crew. It is at the same elevation as the rig floor, usually cantilevered out from the main substructure supporting the rig.
284None
285None
286doghouse
287--
288drop ball
2891.n. [Perforating, Well Completions]
290A ball that is dropped or pumped through the wellbore tubulars to activate a downhole tool or device. When the ball is located on a landing seat, hydraulic pressure generally is applied to operate the tool mechanism.
291ball-operated
292None
293None
294--
295delta rho
2961.n. [Formation Evaluation]
297A log that shows the magnitude of the correction applied to the long-spacing detector of a density measurement. When delta rho is above a certain value, typically +/- 0.15 g/cm3, the correction may no longer be accurate, and needs to be examined in more detail. Delta rho is also used as a qualitative indicator of borehole rugosity.
298azimuthal density, compensated-density log, spine and ribs plot
299None
300None
301--
302diameter of investigation
3031.n. [Formation Evaluation]
304A distance that characterizes how far a logging tool measures into the formation from the axis of the tool or borehole. The term is similar to depth of investigation but is appropriate only for azimuthally symmetric measurements such as resistivity.
305azimuthal, depth of investigation, radial response, radius of investigation
306None
307None
308--
309dog leg
3101.n. [Drilling]
311A particularly crooked place in a wellbore where the trajectory of the wellbore in three-dimensional space changes rapidly. While a dogleg is sometimes created intentionally by directional drillers, the term more commonly refers to a section of the hole that changes direction faster than anticipated or desired, usually with harmful side effects. In surveying wellbore trajectories, a standard calculation of dogleg severity is made, usually expressed in two-dimensional degrees per 100 feet [degrees per 30 m] of wellbore length.There are several difficulties associated with doglegs. First, the wellbore is not located in the planned path. Second is the possibility that a planned casing string may no longer easily fit through the curved section. Third, repeated abrasion by the drillstring in a particular location of the dogleg results in a worn spot called a keyseat, in which the bottomhole assembly components may become stuck as they are pulled through the section. Fourth, casing successfully cemented through the dogleg may wear unusually quickly due to higher contact forces between the drillstring and the inner diameter (ID) of the casing through the dogleg. Fifth, a relatively stiff bottomhole assembly may not easily fit through the dogleg section drilled with a relatively limber BHA. Sixth, excessive doglegs increase the overall friction to the drillstring, increasing the likelihood of getting stuck or not reaching the planned total depth. Usually these problems are manageable. If the dogleg impairs the well, remedial action can be taken, such as reaming or underreaming through the dogleg, or even sidetracking in extreme situations.
312None
313None
314dogleg
315--
316dog leg
3172.n. [Geophysics]
318An abrupt turn, bend or change of direction in a survey line, a wellbore, or a piece of equipment. Dog-legs can be described in terms of their length and severity and quantified in degrees or degrees per unit of distance.
319None
320None
321None
322--
323drop bar
3241.n. [Perforating]
325A heavy steel bar that is dropped through the tubing or running string to fire the percussion detonator on a tubing-conveyed perforating (TCP) gun assembly. The drop bar must be capable of falling through the string with sufficient speed to impart the necessary force for detonation. Therefore, this method of firing is best suited to vertical or slightly deviated wellbores where there will be minimal drag or friction effect.
326friction effect, perforating gun, tubing-conveyed perforating
327None
328None
329--
330delta t
3311.n. [Geophysics, Formation Evaluation]
332Also called interval transit time, the amount of time for a wave to travel a certain distance, proportional to the reciprocal of velocity, typically measured in microseconds per foot by an acoustic log and symbolized by t or DT. P-wave interval transit times for common sedimentary rock types range from 43 (dolostone) to 160 (unconsolidated shales) microseconds per foot, and can be distinguished from measurements of steel casing, which has a consistent transit time of 57 microseconds per foot.
333acoustic, drift, P-wave
334interval transit time, slowness
335None
336--
337diamond bit
3381.n. [Drilling]
339A tool for drilling rock that works by scraping industrial grade diamonds against the bottom of the hole. The diamonds are embedded into the metal structure (usually a sintered or powdered carbide base matrix) during the manufacture of the bit. The bit designer has virtually unlimited combinations of bit shape, the placement of hydraulic jetting ports, the amount of diamonds and the size of the diamonds used (usually expressed as diamonds per carat). In general, a diamond bit that drills faster has a shorter lifetime. Similarly, a bit designed for extremely long life will typically drill at a slower rate. If a bit has a relatively high number of diamonds compared with other bits, it is said to be "heavy-set" and has higher durability. A "light-set" bit, on the other hand, drills more aggressively, but wears out faster because fewer diamonds do the work.
340None
341None
342None
343--
344doghouse
3451.n. [Drilling]
346The steel-sided room adjacent to the rig floor, usually having an access door close to the driller's controls. This general-purpose shelter is a combination tool shed, office, communications center, coffee room, lunchroom and general meeting place for the driller and his crew. It is at the same elevation as the rig floor, usually cantilevered out from the main substructure supporting the rig.
347driller, rig floor
348None
349None
350--
351dry forward combustion
3521.n. [Enhanced Oil Recovery, Heavy Oil]
353A type of in situ combustion in which the burning front moves in the same direction as the injected air. As air is continuously supplied at the injection well, the fire ignited at this location moves toward the production wells.During forward combustion, the temperature behind the burning front is high, indicating a great amount of heat stored in the formation matrix. The injected gas heats on contact with the matrix and recovers only a small amount of the heat, with considerable losses to the surrounding formations. Another drawback of dry forward combustion is the presence of a highly viscous oil zone surrounding the production well. The fluid in this zone remains at the original reservoir temperature and its forward displacement by the heated oil is normally difficult.
354dry combustion, enhanced oil recovery, liquid blocking, reverse combustion, thermal recovery, wet combustion
355None
356None
357--
358delta t stretch
3591.n. [Formation Evaluation]
360A feature on a sonic log caused by low signal amplitude that results in erroneously long traveltimes. Sonic logs that do not record waveforms measure the acoustic traveltime between transmitter and receiver by detecting the first signal at the receiver above a certain threshold (first motion detection). The threshold is small so that the signal is detected just after it crosses the zero signal baseline. However, if the threshold is set too high, or the signal is too small, the system will not trigger at the sharp zero crossing but at some later point on the waveform. This increases the apparent transmitter-receiver time. Delta-t stretch is more likely at the far receiver, where signals are weaker, so that the apparent traveltime calculated between receivers is too large. In the extreme case, the system triggers on the next cycle of the waveform, known as cycle skipping.
361acoustic traveltime, cycle skip, delta t, sonic measurement, zero crossing
362None
363None
364--
365diapir
3661.n. [Geology]
367A relatively mobile mass that intrudes into preexisting rocks. Diapirs commonly intrude vertically through more dense rocks because of buoyancy forces associated with relatively low-density rock types, such as salt, shale and hot magma, which form diapirs. The process is known as diapirism. By pushing upward and piercing overlying rock layers, diapirs can form anticlines, salt domes and other structures capable of trapping hydrocarbons. Igneous intrusions are typically too hot to allow the preservation of preexisting hydrocarbons.
368anticline, halite, preservation, salt dome, structure, trap
369None
370None
371--
372dogleg
3731.n. [Drilling]
374A particularly crooked place in a wellbore where the trajectory of the wellbore in three-dimensional space changes rapidly. While a dogleg is sometimes created intentionally by directional drillers, the term more commonly refers to a section of the hole that changes direction faster than anticipated or desired, usually with harmful side effects. In surveying wellbore trajectories, a standard calculation of dogleg severity is made, usually expressed in two-dimensional degrees per 100 feet [degrees per 30 m] of wellbore length.There are several difficulties associated with doglegs. First, the wellbore is not located in the planned path. Second is the possibility that a planned casing string may no longer easily fit through the curved section. Third, repeated abrasion by the drillstring in a particular location of the dogleg results in a worn spot called a keyseat, in which the bottomhole assembly components may become stuck as they are pulled through the section. Fourth, casing successfully cemented through the dogleg may wear unusually quickly due to higher contact forces between the drillstring and the inner diameter (ID) of the casing through the dogleg. Fifth, a relatively stiff bottomhole assembly may not easily fit through the dogleg section drilled with a relatively limber BHA. Sixth, excessive doglegs increase the overall friction to the drillstring, increasing the likelihood of getting stuck or not reaching the planned total depth. Usually these problems are manageable. If the dogleg impairs the well, remedial action can be taken, such as reaming or underreaming through the dogleg, or even sidetracking in extreme situations.
375bottomhole assembly, casing string, directional driller, inside diameter, ream, sidetrack, total depth, underream
376None
377None
378--
379dogleg
3802.n. [Geophysics]
381An abrupt turn, bend or change of direction in a survey line, a wellbore, or a piece of equipment. Dog-legs can be described in terms of their length and severity and quantified in degrees or degrees per unit of distance.
382wellbore
383None
384None
385--
386dry gas
3871.n. [Geology]
388Natural gas that occurs in the absence of condensate or liquid hydrocarbons, or gas that has had condensable hydrocarbons removed. Dry gas typically has a gas-to-oil ratio exceeding 100,000 scf/STB.
389gas/oil ratio (GOR), hydrocarbon, natural gas
390None
391Antonyms:wet gas
392--
393dry gas
3942.n. [Well Completions]
395Gas produced from a well that produces little or no condensate or reservoir liquids. The production of liquids from gas wells complicates the design and operation of surface process facilities required to handle and export the produced gas.
396gas well
397None
398Antonyms:wet gas
399--
400delta t stretch
4011.n. [Formation Evaluation]
402A feature on a sonic log caused by low signal amplitude that results in erroneously long traveltimes. Sonic logs that do not record waveforms measure the acoustic traveltime between transmitter and receiver by detecting the first signal at the receiver above a certain threshold (first motion detection). The threshold is small so that the signal is detected just after it crosses the zero signal baseline. However, if the threshold is set too high, or the signal is too small, the system will not trigger at the sharp zero crossing but at some later point on the waveform. This increases the apparent transmitter-receiver time. Delta-t stretch is more likely at the far receiver, where signals are weaker, so that the apparent traveltime calculated between receivers is too large. In the extreme case, the system triggers on the next cycle of the waveform, known as cycle skipping.
403acoustic traveltime, cycle skip, delta t, sonic measurement, traveltime, zero crossing
404None
405None
406--
407diatom
4081.n. [Geology]
409A microscopic, single-celled, freshwater or saltwater algae that has a silica-rich cell wall called a frustule. Diatoms are so abundant that they can form thick layers of sediment composed of the frustules of the organisms that died and sank to the bottom. Frustules have been an important component of deep-sea deposits since Cretaceous time. Diatomite is the sedimentary rock that forms from diatom frustules.
410diatomite, geologic time scale, plankton, sedimentary, silica
411None
412None
413--
414dolostone
4151.n. [Geology]
416A rock composed chiefly (> 90%) of dolomite. The rock is sometimes called dolomite, but dolostone is preferable to avoid ambiguity between the mineral and rock names. Replacement dolomite that forms soon after deposition is typically fine-grained and preserves original sedimentary structures. Recrystallization late in diagenesis produces coarser grained dolomite, destroys sedimentary structures and results in higher porosity.
417carbonate, diagenesis, dolomite, dolomitization, evaporite
418None
419None
420--
421dry hole
4221.n. [Drilling]
423A wellbore that has not encountered hydrocarbons in economically producible quantities. Most wells contain salt water in some zones. In addition, the wellbore usually encounters small amounts of crude oil and natural gas. Whether the well is a "duster" depends on many factors of the economic equation, including proximity to transport and processing infrastructures, local market conditions, expected completion costs, tax and investment recovery conditions of the jurisdiction and projected oil and gas prices during the productive life of the well.
424crude oil, duster, hydrocarbon, natural gas
425None
426None
427--
428densitometer
4291.n. [Well Workover and Intervention]
430A device installed on a mixing or pumping system manifold to measure the density of fluids. The density of fluids pumped into a well is frequently a key operating parameter, requiring constant monitoring and control. This is especially true when mixing slurries and transport fluids for solids, such as fracturing or gravel-pack fluids.
431gravel pack, pump manifold
432None
433densimeter
434--
435diatomaceous
4361.adj. [Geology]
437Pertaining to a diatom, which is a microscopic, single-celled, freshwater or saltwater algae that has a silica-rich cell wall called a frustule. Diatoms are so abundant that they can form thick layers of sediment composed of the frustules of the organisms that died and sank to the bottom. Frustules have been an important component of deep-sea deposits since Cretaceous time. Diatomite is the sedimentary rock that forms from diatom frustules.
438diatomite, geologic time scale, plankton, sedimentary, silica
439None
440None
441--
442domainal fabric
4431.n. [Reservoir Characterization]
444A structure made up of a number of superposed domains, usually of different size or wavelength. These are used in geostatistical work to describe statistical behaviors on small scales (such as porosity in thin sections) to large scales (such as porosity distributions in reservoirs).
445geostatistics, reservoir
446domainal structure
447None
448--
449dry oil
4501.n. [Production Facilities]
451A treated oil that contains small amounts of basic sediments and water (BS&W). Dry oil is also called clean oil.
452BS&W
453None
454Antonyms:wet oil
455--
456density
4571.n. [Geology]
458Mass per unit of volume. Density is typically reported in g/cm3 (for example, rocks) or pounds per barrel (drilling mud) in the oil field.
459density contrast, grain density, mud weight, seismic trace, specific gravity
460None
461None
462--
463dielectric propagation log
4641.n. [Formation Evaluation]
465A log of the high-frequency (on the order of 25 MHz) dielectric properties of the formation. The log usually includes two curves the relative dielectric permittivity, symbolized by epsilon which is unitless, and the resistivity in ohm-m. At the frequency used, water molecules have a strong effect on the dielectric properties, so that both relative dielectric permittivity and conductivity increase with the volume of water present. Relative dielectric permittivity can be used to distinguish hydrocarbons from water of any salinity. However, the effect of salinity is more important than the salinity effect with the high-frequency electromagnetic propagation log, and the interpretation is more complex. The advantage of the dielectric propagation log is that the lower frequency permits a larger depth of investigation and therefore an analysis of the undisturbed zone.
466electromagnetic propagation measurement
467None
468None
469--
470domainal structure
4711.n. [Reservoir Characterization]
472A structure made up of a number of superposed domains, usually of different size or wavelength. These are used in geostatistical work to describe statistical behaviors on small scales (such as porosity in thin sections) to large scales (such as porosity distributions in reservoirs).
473geostatistics, reservoir
474domainal fabric
475None
476--
477dss
4781.n. [Geophysics]
479A seismic profile recorded specifically to study the lower crust, the Mohorovicic discontinuity and the mantle of the Earth, typically using refraction methods. Most standard seismic reflection profiles record only a small fraction (typically, on the order of 10 km [6 miles]) of the Earth's crust, which is 5 to 75 km [3 to 45 miles] thick.
480None
481None
482deep seismic sounding
483--
484density current
4851.n. [Geology]
486An influx of rapidly moving, sediment-laden water down a slope into a larger body of water; the suspended sediment causes the current to have a higher density than the clearer water into which it flows, hence the name. Such currents can occur in lakes and oceans, in some cases as by-products of earthquakes or mass movements such as slumps. Thesedimentarydeposits that form as the current loses energy are called turbidites and can be preserved as Bouma sequences. Density currents are characteristic of trench slopes ofconvergentplate margins and continental slopes of passive margins.
487Bouma sequence, channel, convergence, lamination, passive margin, sediment, turbidite
488turbidity current
489None
490--
491dielectric resistivity
4921.n. [Formation Evaluation]
493The resistivity of the formation derived by combining the attenuation and phase shift of a propagation resistivity measurement. Common practice is to transform attenuation and phase shift independently to resistivity, assuming a certain transform between permittivity and resistivity. These relations lose accuracy at high resistivity. However, by combining the two measurements, both the dielectric permittivity and resistivity can be determined without need for a transform. The dielectric resistivity extends the range of measurement, typically up to 3000 ohm-m.
494attenuation resistivity, dielectric permittivity, phase shift, phase-shift resistivity, polarization horn, propagation resistivity
495None
496None
497--
498dome
4991.n. [Geology]
500A type of anticline that is circular or elliptical rather than elongate. The upward migration of salt diapirs can form domes, called salt domes.
501anticline, diapir, salt dome
502None
503None
504--
505dst
5061.n. [Well Testing]
507Well tests conducted with the drillstring still in the hole. Often referred to as DST, these tests are usually conducted with a downhole shut-in tool that allows the well to be opened and closed at the bottom of the hole with a surface-actuated valve. One or more pressure gauges are customarily mounted into the DST tool and are read and interpreted after the test is completed. The tool includes a surface-actuated packer that can isolate the formation from the annulus between the drillstring and the casing, thereby forcing any produced fluids to enter only the drillstring. By closing in the well at the bottom, afterflow is minimized and analysis is simplified, especially for formations with low flow rates. The drillstring is sometimes filled with an inert gas, usually nitrogen, for these tests. With low-permeability formations, or where the production is mostly water and the formation pressure is too low to lift water to the surface, surface production may never be observed. In these cases, the volume of fluids produced into the drillstring is calculated and an analysis can be made without obtaining surface production. Occasionally, operators may wish to avoid surface production entirely for safety or environmental reasons, and produce only that amount that can be contained in the drillstring. This is accomplished by closing the surface valve when the bottomhole valve is opened. These tests are called closed-chamber tests.Drillstem tests are typically performed on exploration wells, and are often the key to determining whether a well has found a commercial hydrocarbon reservoir. The formation often is not cased prior to these tests, and the contents of the reservoir are frequently unknown at this point, so obtaining fluid samples is usually a major consideration. Also, pressure is at its highest point, and the reservoir fluids may contain hydrogen sulfide, so these tests can carry considerable risk for rig personnel.The most common test sequence consists of a short flow period, perhaps five or ten minutes, followed by a buildup period of about an hour that is used to determine initial reservoir pressure. This is followed by a flow period of 4 to 24 hours to establish stable flow to the surface, if possible, and followed by the final shut-in or buildup test that is used to determine permeability thickness and flow potential
508None
509None
510drillstem test
511--
512density measurement
5131.n. [Formation Evaluation]
514A measurement of the bulk density of the formation, based on the reduction in gamma ray flux between a source and a detector due to Compton scattering. The gamma ray source, usually 137Cs (cesium), is chosen so that gamma ray energies are high enough to interact by Compton scattering but not by pair production. The detectors discriminate against low gamma ray energies that may have been influenced by photoelectric absorption. Although Compton scattering depends on electron density and not bulk density, density logs are calibrated to give the correct bulk density in the majority of sedimentary rocks. Due to the Z/A effect there are small differences in some formations.The measurement responds to the average density of the material between source and detector. In the wireline measurement, care is taken to minimize the mud between the sensors and the formation by pressing a pad against the borehole wall, with source and detector focused into the formation. In the logging-while-drilling measurement, a sleeve may be mounted on the collar around the sensors to exclude the mud. The detectors measure the gamma rays scattered from the formation. Even then, mudcake or borehole rugosity can affect the measurement. It is common practice to compensate for the mudcake by using two or more detectors at different spacings.
515azimuthal density, compensated-density log, Compton scattering, cross section, delta rho, logging while drilling, pair production, PEF, scintillation detector, spine and ribs plot, Z/A effect
516None
517None
518--
519density measurement
5202.n. [Formation Evaluation]
521A measurement of the bulk density of the formation based on borehole-gravity measurements. As the gravitational attraction between two bodies is dependent upon their masses and their separation, it follows that its measurement also can be used to make a direct determination of density. The density thus measured is highly accurate but averaged over a large volume.
522borehole gravity
523None
524None
525--
526diesel oil mud
5271.n. [Drilling Fluids]
528An oil-base mud with diesel oil as its external phase. Diesel-oil mud is the traditional oil mud and has a history of excellent performance for drilling difficult wells. It has been used because the base oil is low-cost and widely available motor fuel. In-gauge holes can be drilled through all types of shales, salt, gypsum and other difficult strata using diesel-oil mud systems. It is often the mud of choice for drilling high-pressure, high-temperature zones. Diesel-oil muds usually contain from 5 to 40 vol.% emulsified brine water (except those that are specially designed to have none). The water phase usually contains 20 to 40 wt.% dissolved calcium chloride for shale control. Diesel-oil muds have been replaced in land drilling by mineral-oil muds and offshore by synthetic-fluid muds. These newer muds have fewer health, safety and environmental concerns compared to diesel oil.
529None
530None
531diesel-oil mud
532--
533dope
5341.n. [Drilling]
535Pipe dope, a specially formulated blend of lubricating grease and fine metallic particles that prevents thread galling (a particular form of metal-to-metal damage) and seals the roots or void spaces of threads. The American Petroleum Institute (API) specifies properties of pipe dope, including its coefficient of friction. The rig crew applies copious amounts of pipe dope to the drillpipe tool joints every time a connection is made.
536drilling crew, tool joint
537None
538pipe dope
539--
540dope
5412.vb. [Drilling]
542To place lubricant on drillpipe, also known as "doping" the pipe.
543pipe dope
544None
545None
546--
547dual induction
5481.n. [Formation Evaluation]
549The combination of a deep-induction and a medium-induction array on the same sonde. In a typical implementation, the two arrays share the same transmitters but have different receivers. If the dual-induction log is combined with a shallow laterolog or microresistivity log, it is possible to correct for the effect on invasion on the deep log, assuming a step profile.
5506FF40, deep induction, induction, medium induction, receiver, step profile
551None
552None
553--
554density profile
5551.n. [Geophysics]
556A series of gravity measurements made along a line or over an area of a locally high topographic feature to remove or compensate for the effect of topography on deeper density readings.
557topographic map
558None
559None
560--
561diesel oil mud
5621.n. [Drilling Fluids]
563An oil-base mud with diesel oil as its external phase. Diesel-oil mud is the traditional oil mud and has a history of excellent performance for drilling difficult wells. It has been used because the base oil is low-cost and widely available motor fuel. In-gauge holes can be drilled through all types of shales, salt, gypsum and other difficult strata using diesel-oil mud systems. It is often the mud of choice for drilling high-pressure, high-temperature zones. Diesel-oil muds usually contain from 5 to 40 vol.% emulsified brine water (except those that are specially designed to have none). The water phase usually contains 20 to 40 wt.% dissolved calcium chloride for shale control. Diesel-oil muds have been replaced in land drilling by mineral-oil muds and offshore by synthetic-fluid muds. These newer muds have fewer health, safety and environmental concerns compared to diesel oil.
564aniline point test, balanced-activity oil mud, external phase, isomerized olefin, linear alphaolefin, oil content, oil mud, oil-base mud, polyalphaolefin, pour point, synthetic-base mud, water-in-oil emulsion
565None
566None
567--
568double block and bleed
5691.n. [Production]
570A valve arrangement that ensures no flow in a line, although the valve may leak. It consists of two block valves in the main line with a small bleeder valve draining the line between the block valves.
571None
572None
573None
574--
575dual porosity reservoir
5761.n. [Well Testing]
577A rock characterized by primary porosity from original deposition and secondary porosity from some other mechanism, and in which all flow to the well effectively occurs in one porosity system, and most of the fluid is stored in the other. Naturally fractured reservoirs and vugular carbonates are classified as dual-porosity reservoirs, as are layered reservoirs with extreme contrasts between high-permeability and low-permeability layers.
578dual-permeability reservoir, primary porosity, secondary porosity
579None
580None
581--
582deposit
5831.n. [Geology]
584Sediments that have accumulated, usually after being moved by wind, water or ice.
585sediment
586None
587None
588--
589deposit
5902.vt. [Geology]
591The action of moving sediments and laying them down.
592sediment
593None
594None
595--
596diesel oil plug
5971.n. [Drilling Fluids]
598Another term for gunk plug, a slurry that consists of bentonite, cement or polymers mixed into an oil; bentonite in diesel oil is commonly used as a gunk plug. A small batch of the slurry is pumped down a well that has lost circulation to seal the leaky zone. The gunk plug may or may not be squeezed by pressure into the zone. Water downhole interacts with the bentonite, cement or polymers to make a sticky gunk.
599gunk, pill, polymer
600gunk plug
601None
602--
603downhole gauge
6041.n. [Well Completions]
605A pressure gauge, typically run on slickline, used to measure and record downhole pressure. Downhole gauges are commonly used in assessing the downhole pressure under various flowing conditions, the basis of pressure transient analysis.
606pressure gauge, pressure transient test
607None
608None
609--
610dual porosity reservoir
6111.n. [Well Testing]
612A rock characterized by primary porosity from original deposition and secondary porosity from some other mechanism, and in which all flow to the well effectively occurs in one porosity system, and most of the fluid is stored in the other. Naturally fractured reservoirs and vugular carbonates are classified as dual-porosity reservoirs, as are layered reservoirs with extreme contrasts between high-permeability and low-permeability layers.
613dual-permeability reservoir, primary porosity, secondary porosity
614None
615None
616--
617depositional energy
6181.n. [Geology]
619The relative kinetic energy of the environment. A high-energy environment might consist of a rapidly flowing stream that is capable of carrying coarse-grained sediments, such as gravel and sand. Sedimentation in a low-energy environment, such as an abyssal plain, usually involves very fine-grained clay or mud. Depositional energy is not simply velocity. For example, although glaciers do not move quickly, they are capable of carrying large boulders.
620abyssal, depositional environment, sediment, sorting
621None
622None
623--
624differential pressure
6251.n. [Drilling]
626In general, a measurement of fluid force per unit area (measured in units such as pounds per square in.) subtracted from a higher measurement of fluid force per unit area. This comparison could be made between pressures outside and inside a pipe, a pressure vessel, before and after an obstruction in a flow path, or simply between two points along any fluid path, such as two points along the inside of a pipe or across a packer.
627packer
628None
629None
630--
631differential pressure
6322.n. [Drilling]
633The change in force per unit area measured before and after drilling fluid passes through small-diameter bit nozzles.
634bit nozzle
635None
636None
637--
638differential pressure
6393.n. [Drilling]
640The change in force per unit area measured across various downhole tools such as measurements-while-drilling (MWD) tools, downhole turbines and mud motors.
641measurements-while-drilling, mud motor
642None
643None
644--
645differential pressure
6464.n. [Drilling]
647The change in force per unit area between the reservoir pore pressure and the wellbore fluid pressure. If this measurement becomes negative in value (that is, the reservoir pressure exceeds the wellbore fluid pressure), then a flow of reservoir fluids into the wellbore can result.
648kick, pore pressure, reservoir pressure
649None
650None
651--
652differential pressure
6535.n. [Production Testing]
654The difference between two pressure measurements. For production wells, the differential pressure is the difference between average reservoir pressure and bottomhole pressure, and for injection wells, it is the difference between injection pressure and average reservoir pressure.
655average reservoir pressure, bottomhole pressure, injection pressure, injection well
656None
657None
658--
659downhole safety valve dsv
6601.n. [Well Completions]
661A downhole device that isolates wellbore pressure and fluids in the event of an emergency or catastrophic failure of surface equipment. The control systems associated with safety valves are generally set in a fail-safe mode, such that any interruption or malfunction of the system will result in the safety valve closing to render the well safe. Downhole safety valves are fitted in almost all wells and are typically subject to rigorous local or regional legislative requirements.
662subsurface safety valve (SSSV)
663None
664None
665--
666dump bailer
6671.n. [Well Workover and Intervention]
668A wireline or slickline tool used to place small volumes of cement slurry, or similar material, in a wellbore. Typically, the slurry is placed on a plug or similar device that provides a stable platform for the low-volume cement plug.
669cement plug
670None
671None
672--
673depositional system
6741.n. [Geology]
675The three-dimensional array of sediments or lithofacies that fills a basin. Depositional systems vary according to the types of sediments available for deposition as well as the depositional processes and environments in which they are deposited. The dominant depositional systems are alluvial, fluvial, deltaic, marine, lacustrine and eolian systems.
676depositional environment, lithofacies, sediment
677None
678None
679--
680differential pressure sticking
6811.n. [Drilling]
682A condition whereby the drillstring cannot be moved (rotated or reciprocated) along the axis of the wellbore. Differential sticking typically occurs when high-contact forces caused by low reservoir pressures, high wellbore pressures, or both, are exerted over a sufficiently large area of the drillstring. Differential sticking is, for most drilling organizations, the greatest drilling problem worldwide in terms of time and financial cost. It is important to note that the sticking force is a product of the differential pressure between the wellbore and the reservoir and the area that the differential pressure is acting upon. This means that a relatively low differential pressure (delta p) applied over a large working area can be just as effective in sticking the pipe as can a high differential pressure applied over a small area.
683low-colloid oil mud, mechanical sticking, overbalance, reservoir pressure, saltwater flow, stuck pipe
684differential sticking, wall sticking
685None
686--
687differential pressure sticking
6882.n. [Drilling Fluids]
689A situation in which the drilling assembly (pipe, drill collars and bottomhole assembly) is stuck in filter cake that was previously deposited on a permeable zone. The pipe is held in the cake by a difference in pressures between the hydrostatic pressure of the mud and the pore pressure in the permeable zone. The force required to pull the pipe free can exceed the strength of the pipe. Methods used to get the pipe free, in addition to pulling and torquing the pipe, include: (1) lowering hydrostatic pressure in the wellbore, (2) placing a spotting fluid next to the stuck zone and (3) applying shock force just above the stuck point by mechanical jarring, or (4) all the above. The most common approach, however, to getting free is to place a spot of oil, oil-base mud, or special spotting fluid.
690filter cake, filter-cake quality, low-colloid oil mud, spotting fluid
691None
692None
693--
694downward continuation
6951.n. [Geophysics]
696A technique used to estimate the value of a potential field or seismic data at a surface beneath a measured surface. The method is risky because it assumes continuity of the field, so anomalies affect predictions, especially if they occur beneath the measured surface. Noise can be exaggerated and affect calculations adversely.
697anomaly, gravity, magnetics, seismic
698None
699Antonyms:upward continuation
700--
701duplex pump
7021.n. [Well Workover and Intervention]
703A type of fluid pump, commonly used on workover rigs, that has two plungers or pistons. As a positive-reciprocating pump, the fluid flow rate is typically calculated from the number of strokes per minute that the pump makes and the displacement volume per stroke. Such a level of accuracy usually is sufficient for general workover purposes.
704fluid flow
705None
706None
707--
708depth control
7091.n. [Well Completions]
710The procedures and equipment used to measure and correlate depth to ensure that a treatment is applied at the correct position within the wellbore.
711None
712None
713None
714--
715depth control
7162.n. [Reservoir Characterization]
717The practice of ensuring that all measurements taken in a borehole are matched to the "base depth," normally the depth determined with the resistivity log.
718depth matching, resistivity log
719None
720None
721--
722differential spectrum
7231.n. [Formation Evaluation]
724A technique in nuclear magnetic resonance (NMR) logging that is based on the difference between the T2 distributions, or spectra, acquired at different polarization times. The technique often is used to detect gas or light oil. These fluids have long T1 that exceed 1 s. A measurement made with a long polarization time will polarize much of these fluids and give significant signal at the appropriate T2. A measurement made with a short polarization time will polarize little of these fluids and will give a much smaller signal. Other fluids, with shorter T1, will be polarized in both cases, so that a difference in signal at the appropriate T2 identifies gas or light oil.
725direct hydrocarbon typing, enhanced diffusion, longitudinal relaxation, nuclear magnetic resonance, nuclear magnetic resonance measurement, polarization time, shifted spectrum, transverse relaxation, wait time
726None
727None
728--
729draeger tube
7301.n. [Drilling Fluids]
731A type of gas detector tube that quantitatively measures a gas that is passed through the tube by the length of the stain it generates chemically in the tube. Dräger tubes are used in Garrett Gas Train tests for sulfides and carbonates.
732carbon dioxide, carbonate, carbonate test, Garrett Gas Train, hydrogen sulfide, sulfide, sulfide test
733None
734Dräger tube
735--
736dyke
7371.n. [Geology]
738An intrusive rock that invades preexisting rocks, commonly in a tabular shape that cuts vertically or nearly vertically across preexisting layers. Dikes form from igneous and sedimentary rocks.
739igneous, sedimentary
740dike
741None
742--
743depth conversion
7441.n. [Geophysics]
745The process of transforming seismic data from a scale of time (the domain in which they are acquired) to a scale of depth to provide a picture of the structure of the subsurface independent of velocity. Depth conversion, ideally, is an iterative process that begins with proper seismic processing, seismic velocity analysis and study of well data to refine the conversion. Acoustic logs, check-shot surveys and vertical seismic profiles can aid depth conversion efforts and improve correlation of well logs and drilling data with surface seismic data.
746acoustic log, check-shot survey, depth map, depth section, pull-up, push-down, seismic processing, seismic section, velocity, vertical seismic profile
747None
748None
749--
750differential sticking
7511.n. [Drilling]
752A condition whereby the drillstring cannot be moved (rotated or reciprocated) along the axis of the wellbore. Differential sticking typically occurs when high-contact forces caused by low reservoir pressures, high wellbore pressures, or both, are exerted over a sufficiently large area of the drillstring. Differential sticking is, for most drilling organizations, the greatest drilling problem worldwide in terms of time and financial cost. It is important to note that the sticking force is a product of the differential pressure between the wellbore and the reservoir and the area that the differential pressure is acting upon. This means that a relatively low differential pressure (delta p) applied over a large working area can be just as effective in sticking the pipe as can a high differential pressure applied over a small area.
753low-colloid oil mud, mechanical sticking, overbalance, pill, reservoir pressure, stuck pipe
754differential pressure sticking, wall sticking
755None
756--
757differential sticking
7582.n. [Drilling Fluids]
759A situation in which the drilling assembly (pipe, drill collars and bottomhole assembly) is stuck in filter cake that was previously deposited on a permeable zone. The pipe is held in the cake by a difference in pressures between the hydrostatic pressure of the mud and the pore pressure in the permeable zone. The force required to pull the pipe free can exceed the strength of the pipe. Methods used to get the pipe free, in addition to pulling and torquing the pipe, include: (1) lowering hydrostatic pressure in the wellbore, (2) placing a spotting fluid next to the stuck zone and (3) applying shock force just above the stuck point by mechanical jarring, or (4) all the above. The most common approach, however, to getting free is to place a spot of oil, oil-base mud, or special spotting fluid.
760bottomhole assembly, drill collar, filter-cake quality, filter-cake thickness, spotting fluid
761differential pressure sticking, wall sticking
762None
763--
764drag bag
7651.adj. [Production Logging]
766Pertaining to a technique in which a packer flowmeter is partially inflated and dragged up the hole to give a continuous flow log. This obsolete technique was introduced in the 1960s because the packer flowmeter could make only stationary measurements.
767packer flowmeter, spinner flowmeter
768None
769None
770--
771dynamic filter press
7721.n. [Drilling Fluids]
773Equipment used to measure filtration under dynamic conditions. Two commercial dynamic-filtration testers are available, one of which uses a thick-walled cylinder with rock-like characteristics as the filter medium to simulate radial flow into a wellbore. The other tester uses flat porous disks, such as paper or fused ceramic plates, as filter media. In a dynamic test, filter cake is continually eroded and deposited. Data from this test include a steady-state filtration rate measured during the test, and cake thickness, cake quality and return permeability of the filter medium measured at the conclusion of a test. There is no API standardized test equipment or procedure.
774dynamic filtration, filter medium, filter press, filter-cake quality, filter-cake thickness, filtrate, fluid-loss-control material
775None
776filtration tester
777--
778depth datum
7791.n. [Formation Evaluation]
780Also known as depth reference, the point in a well from which depth is measured. Alternatively, the depth reference is the point at which the depth is defined as being zero. It is typically the top of the kelly bushing or the level of the drill floor on the rig that is used to drill the well. The depth measured from that point is the measured depth (MD) for the well. Even when the drilling rig has been removed, all subsequent measurements and operations in the well are still tied in to the same depth reference. However, for multiwell studies, the depths are normally shifted to the permanent datum. The depth reference and its elevation above the permanent datum are recorded on the log heading. In some contexts, the term may refer to any point from which depth is measured.
781depth wheel, first reading, last reading
782depth reference
783None
784--
785differential temperature log
7861.n. [Production Logging]
787A record of the difference in temperature between two vertical points in a well. Most differential-temperature logs are obtained by differentiating a normal temperature log with respect to depth. Some are obtained by recording the difference in temperature between two vertically displaced sensors. Note that the differential-temperature log and the radial differential-temperature log are not the same.
788production log, radial differential-temperature log
789None
790None
791--
792drag bit
7931.n. [Drilling]
794A drilling tool that uses polycrystalline diamond compact (PDC) cutters to shear rock with a continuous scraping motion. These cutters are synthetic diamond disks about 1/8-in. thick and about 1/2 to 1 in. in diameter. PDC bits are effective at drilling shale formations, especially when used in combination with oil-base muds.
795antiwhirl bit, bit
796drag bit, PDC bit
797None
798--
799dynamic filtration
8001.n. [Drilling Fluids]
801A filtration process in which the slurry being filtered is being circulated over the filter cake, so that the cake is simultaneously eroded and deposited. The erosion rate depends on the shear rate of the fluid at the face of the cake. If the shear rate remains constant, cake thickness and filtration rate reach steady state, usually in a matter of hours. When the conditions change, a new steady state will be established.
802bland coring fluid, core, dynamic filter press, filter cake, filter medium, filter press, filter-cake quality, filter-cake thickness, filtrate, filtrate tracer, filtrate volume, fluid-loss-control material, relative filtrate volume, shear rate, slurry, spotting fluid
803None
804Antonyms:static filtration
805--
806depth derived
8071.adj. [Formation Evaluation]
808Referring to a borehole-compensation scheme for sonic logs that combines measurements taken when the logging tool is at two different depths in the borehole. In normal borehole-compensation schemes, the effects of caves and sonde tilt are minimized by combining measurements from a second transmitter (T2) above a pair of receivers with those from the first transmitter (T1) below the receivers. This arrangement makes the logging tool unacceptably long for the long-spacing sonic log. In the depth-derived system, T2 is located below T1, at a distance equal to the receiver spacing. T1 is fired and the transit time between the receivers at depth z (TT1z) is recorded as usual. Then when T1 and T2 are at depth z, both are fired sequentially and the difference in time for their signals to reach one of the receivers is recorded (TT2z). The average of TT1z and TT2z is borehole-compensated since the acoustic signals traveled in opposite directions for the two measurements.
809borehole compensation, logging tool, long-spacing sonic log, sonic log, sonic measurement
810None
811None
812--
813differential temperature log
8141.n. [Production Logging]
815A record of the difference in temperature between two vertical points in a well. Most differential-temperature logs are obtained by differentiating a normal temperature log with respect to depth. Some are obtained by recording the difference in temperature between two vertically displaced sensors. Note that the differential-temperature log and the radial differential-temperature log are not the same.
816production log, radial differential-temperature log
817None
818None
819--
820drag bag
8211.adj. [Production Logging]
822Pertaining to a technique in which a packer flowmeter is partially inflated and dragged up the hole to give a continuous flow log. This obsolete technique was introduced in the 1960s because the packer flowmeter could make only stationary measurements.
823packer flowmeter, spinner flowmeter
824None
825None
826--
827dynamic fluid level
8281.n. [Production Testing]
829The level to which the static fluid level drops in the tubing or casing when the well produced under pumping conditions. The dynamic fluid level is also called the pumping fluid level.
830static fluid level
831None
832None
833--
834depth mark
8351.n. [Formation Evaluation]
836A magnetic mark placed on a logging cable as a reference for depth measurements. The marks are placed on the cable at regular intervals, usually 100 ft [30 m] or 50 m [164 ft], under a certain tension in a workshop. The intervals may change slightly as a function of tension downhole, but this change can be corrected for. During logging operations, the marks are detected by a magnetic mark detector, and then used to check and correct the depth read by the depth wheel.
837depth wheel
838None
839None
840--
841diffraction stack
8421.n. [Geophysics]
843Also known as Kirchhoff migration, a method of seismic migration that uses the integral form (Kirchhoff equation) of the wave equation. All methods of seismic migration involve the backpropagation (or continuation) of the seismic wavefield from the region where it was measured (Earth's surface or along a borehole) into the region to be imaged. In Kirchhoff migration, this is done by using the Kirchhoff integral representation of a field at a given point as a (weighted) superposition of waves propagating from adjacent points and times. Continuation of the wavefield requires a background model of seismic velocity, which is usually a model of constant or smoothly varying velocity. Because of the integral form of Kirchhoff migration, its implementation reduces to stacking the data along curves that trace the arrival time of energy scattered by image points in the earth.
844diffraction, Kirchhoff equation, migration, ray tracing
845Kirchhoff migration
846None
847--
848drager tube
8491.n. [Drilling Fluids]
850A type of gas detector tube that quantitatively measures a gas that is passed through the tube by the length of the stain it generates chemically in the tube. Dräger tubes are used in Garrett Gas Train tests for sulfides and carbonates.
851carbon dioxide, carbonate, carbonate test, Garrett Gas Train, hydrogen sulfide, sulfide, sulfide test
852None
853Draeger tube
854--
855dynamic positioning
8561.n. [Drilling]
857The stationing of a vessel, especially a drillship or semisubmersible drilling rig, at a specific location in the sea by the use of computer-controlled propulsion units called thrusters. Though drilling vessels have varying sea and weather state design conditions, most remain relatively stable even under high wind, wave and current loading conditions. Inability to maintain stationkeeping, whether due to excessive natural forces or failure of one or more electromechanical systems, leads to a "drive off" condition that requires emergency procedures to disconnect the riser from the subsea BOP stack, or worse, drop the riser from the vessel altogether.
858BOP stack, drilling riser, drillship, semisubmersible
859None
860None
861--
862depth matched
8631.adj. [Formation Evaluation]
864Pertaining to two or more logging curves that have been aligned in depth. Logs recorded on different runs will not be exactly aligned at all depths because of the difficulty of perfect depth control. If the two logs are offset by the same amount throughout the log, then only a simple depth shift is required. If the offset varies, then the logs need to be depth matched.Depth matching is simplest if both runs contain the same type of log, such as a gamma ray. The two gamma rays can then be aligned, either manually or with software, and the other logs shifted by the same amount. Otherwise the alignment is based on two logs that respond in a similar fashion, such as a neutron porosity and a shallow laterolog.Depth matching also may be needed for logs recorded on the same run. Although there is a fixed distance between the measure points and the depth reference, the apparent distance will vary if the tool moves unevenly up the hole, due to stick and slip or yo-yo effects. Depth matching is then necessary.
865base log, curve, depth control, gamma ray log, neutron porosity, stick and slip
866None
867None
868--
869diffusion equation
8701.n. [Geophysics]
871A partial differential equation describing the variation in space and time of a physical quantity that is governed by diffusion. The diffusion equation provides a good mathematical model for the variation of temperature through conduction of heat and the propagation of electromagnetic waves in a highly conducting medium. The diffusion equation is a parabolic partial differential equation whose characteristic form relates the first partial derivative of a field with respect to time to its second partial derivatives with respect to spatial coordinates. It is closely related to the wave equation.∇2E = j ω μ σ E,whereE = electrical fieldω = angular frequencyμ = magnetic permeabilityσ = electrical conductivity∇ = vector differential operator.
872electromagnetic method, wave equation
873None
874None
875--
876diffusion equation
8772.n. [Well Testing]
878A fundamental differential equation obtained by combining the continuity equation, flow law and equation of state. Most of the mathematics of well testing were derived from solutions of this equation, which was originally developed for the study of heat transfer. Fluid flow through porous media is directly analogous to flow of heat through solids. Solutions used in well testing usually assume radial flow and homogenous, isotropic formations.
879continuity equation, equation of state, fluid flow, isotropic formation
880None
881None
882--
883drain hole
8841.n. [Well Completions]
885A hole or short conduit through which fluids can flow. In equipment applications, a drainhole is generally made to avoid the buildup of pressure within a nonpressure area, such as may occur in the event of a leak in a pressure housing within a tool assembly.
886pressure buildup
887None
888None
889--
890dynamic aging test
8911.n. [Drilling Fluids]
892A mud test in which the mud sample is mildly agitated by rolling (or tumbling) for the duration of the test, usually performed at a selected high temperature. Typically, the mud sample is sealed in a mud-aging cell and placed in an oven that will roll (or tumble) the mud cells continually for a given period of time (often 16 hours or overnight). The cooled mud is tested for properties. A rolled (or tumbled) mud sample simulates circulation in the hole by pumping.
893barrel equivalent, mud oven, mud-aging cell, pilot test, static-aging test, temperature stability
894rolling-aging test
895None
896--
897depth matching
8981.n. [Reservoir Characterization]
899The practice of shifting depths of various data sets to a measurement that is known to be on depth. The general standard that is usually used is the first resistivity logs run, because those logs usually underwent the most rigorous depth control.Depth matching is usually applied to all wireline data, cores, borehole seismic data, and any other data taken in a well. Depth matching is a vital process in any well evaluation or any reservoir characterization exercise, so much so that, in its absence, accuracy and validity of the exercise must be questioned.
900borehole seismic data, depth control, reservoir characterization
901None
902None
903--
904dike
9051.n. [Geology]
906An intrusive rock that invades preexisting rocks, commonly in a tabular shape that cuts vertically or nearly vertically across preexisting layers. Dikes form from igneous and sedimentary rocks.
907igneous, sedimentary
908dyke
909None
910--
911drainhole
9121.n. [Well Completions]
913A hole or short conduit through which fluids can flow. In equipment applications, a drainhole is generally made to avoid the buildup of pressure within a nonpressure area, such as may occur in the event of a leak in a pressure housing within a tool assembly.
914pressure buildup
915None
916None
917--
918dynamite
9191.n. [Geophysics]
920A type of explosive used as a source for seismic energy during data acquisition. Originally, dynamite referred specifically to a nitroglycerin-based explosive formulated in 1866 by Alfred Bernhard Nobel (1833 to 1896), the Swedish inventor who endowed the Nobel prizes. The term is incorrectly used to mean any explosive rather than the original formulation.
921air shooting, shot depth
922None
923None
924--
925depth of invasion
9261.n. [Formation Evaluation]
927The distance from the borehole wall that the mud filtrate has penetrated into the formation. The depth of invasion affects whether a log measures the invaded zone, the undisturbed zone or part of each zone. The term is closely related to the diameter of invasion, the latter being twice the depth of invasion plus the borehole diameter. Depth of invasion is a more appropriate parameter for describing the response of pad and azimuthally focused measurements such as density and microresistivity logs.The term is well-defined in the case of a step profile of invasion. In the case of an annulus or a transition zone, two depths must be defined, corresponding to the inner and outer limits of the annulus or transition zone. When the invasion model is not specified, the term usually refers to the outer limit of invasion.
928azimuthal, diameter of invasion, filtrate slump, flushed zone, step profile, transition zone
929None
930None
931--
932diluent
9331.n. [Heavy Oil]
934A hydrocarbon fluid that is used to dilute heavy oil and reduce its viscosity for easier transportation. Generally a distillation tower cut such as naphtha is used as for heavy oil dilution and transportation. The added diluent may be recovered at the destination using distillation and the diluent may be subsequently pumped back for blending.
935None
936None
937None
938--
939drawdown test
9401.n. [Well Testing]
941The measurement and analysis of pressure data taken after a well is put on production, either initially or following an extended shut-in period. Drawdown data are usually noisy, meaning that the pressure moves up and down as fluid flows past the gauges and minute variations in flow rate take place. This is especially true for new wells, in which well cleanup commonly occurs for days after production has begun. Such data are difficult to interpret, and the noise often obscures regions of interest to the analyst. Transient downhole flow rates measured while flowing can be used to correct pressure variations through convolution or deconvolution calculations that enable diagnosis and interpretation, analogous to that done for the pressure change and derivative.
942buildup test
943None
944None
945--
946dynamometer card
9471.n. [Production Testing]
948The record made by the dynamometer. An analysis of this survey may reveal a defective pump, leaky tubing, inadequate balance of the pumping unit, a partially plugged mud anchor, gas locking of the pump or an undersized pumping unit. The dynamometer card is also called a dynagraph.
949mud anchor
950None
951None
952--
953depth of investigation
9541.n. [Formation Evaluation]
955A distance that characterizes how far a logging tool measures into the formation from the face of the tool or the borehole wall. The depth of investigation summarizes the radial response of the measurement in one or more directions. For nuclear and resistivity measurements, the depth of investigation should be associated with the percentage of signal received from within that depth, typically either 50% or 90%. Most quoted depths of investigation assume a homogeneous formation with certain properties, such as a given resistivity or fluid content. The depths of investigation can vary considerably in inhomogeneous conditions, and at different values of the properties concerned. They should be considered only a qualitative guide to tool response.For other measurements, the depth of investigation is either well-defined by the tool physics (in the case of nuclear magnetic resonance), or else can be given only approximately, an accurate value being too dependent on formation properties (in the case of acoustic and electromagnetic propagation).The term is used for all measurements but is most appropriate for azimuthally focused devices such as nuclear logs. For azimuthally symmetric devices such as resistivity logs, the term radius of investigation is more appropriate.
956diameter of investigation, electromagnetic propagation, geometrical factor, logging tool, nuclear magnetic resonance, radial resolution, radial response, radius of investigation, resistivity log
957None
958None
959--
960dilution water
9611.n. [Drilling Fluids]
962Also called make-up water, which is water added to maintain or dilute a water-mudsystem. The added water may befresh water, seawater orsaltwater, as appropriate for the mud. Make-up water volume is an importantparameterin a material balancecheck on solids content and solids removal efficiency for a mud system. The amount of dilutionstrongly influences mud economics. If soft make-up water is needed, treatments to remove hardness ions should be done prior to adding the water to the mud to avoidclayflocculationand polymer precipitation.
963None
964make-up water
965None
966--
967eccentric
9681.adj. [Drilling]
969Off-center, as when a pipe is off-center within another pipe or the openhole. Eccentricity is usually expressed as a percentage. A pipe would be considered to be fully (100%) eccentricif it were lying against theinside diameterof the enclosing pipe or hole. A pipe would be said to be concentric (0% eccentric) if it were perfectly centered in the outer pipe or hole. Eccentricity becomes important to the well designer in estimatingcasingwear, wear and tear on the drillstring, and the removal ofcuttingsfrom the low side of an inclined hole. In the latter case, if thedrillpipelies on the low side of the hole (100% eccentric), the eccentricity results in low-velocityfluid flow on the low side.Gravitypulls cuttings to the low side of the hole, building a bed of smallrockchips on the low side of the hole known as a cuttings bed. This cuttings bed becomes difficult to clean out of theannulusand can lead to significant problems for the drilling operation if the pipe becomesstuckin the cuttings bed.
970centralizer, fluid flow
971None
972Antonyms:concentric
973--
974electrical coupon
9751.n. [Well Workover and Intervention]
976An instrument used in acorrosiontest to determine metal loss. It directly measures the increase in resistance of a metal as itscross-sectionalarea is reduced by corrosion. At suitable times, once the readings are obtained, these numbers are converted into corrosion rates (mpy).An electricalcoupon is also called an electrical resistance probe.
977None
978electrical resistance probe
979None
980--
981en echelon
9821.adj. [Geology]
983Describing parallel or subparallel, closely-spaced, overlapping or step-like minor structural features in rock, such as faults and tension fractures, that are oblique to the overall structural trend.
984fault, fracture, structure
985None
986None
987--
988erosion corrosion
9891.n. [Enhanced Oil Recovery]
990A type of corrosion produced when easily removed scales (such as iron carbonate) that were initially protecting the metals in the pipe are eroded and the underlying metals are corroded.Erosion-corrosion is a common cause of failure in oilfield equipment. The attack is normally localized at changes of pipe sections, bends or elbows where there is high velocity or turbulent flow.
991corrosion control, scale, turbulent flow
992None
993None
994--
995eccentricity
9961.n. [Drilling]
997The term used to describe how off-center a pipe is within another pipe or the openhole. It is usually expressed as a percentage. A pipe would be considered to be fully (100%) eccentric if it were lying against the inside diameter of the enclosing pipe or hole. A pipe would be said to be concentric (0% eccentric) if it were perfectly centered in the outer pipe or hole. Eccentricity becomes important to the well designer in estimating casing wear, wear and tear on the drillstring, and the removal of cuttings from the low side of an inclined hole. In the latter case, if the drillpipe lies on the low side of the hole (100% eccentric), the eccentricity results in low-velocity fluid flow on the low side. Gravity pulls cuttings to the low side of the hole, building a bed of small rock chips on the low side of the hole known as a cuttings bed. This cuttings bed becomes difficult to clean out of the annulus and can lead to significant problems for the drilling operation if the pipe becomes stuck in the cuttings bed.
998centralizer, fluid flow
999None
1000Antonyms:concentric
1001--
1002electrical double layer
10031.n. [Formation Evaluation, Enhanced Oil Recovery]
1004With reference to formation evaluation, the layer between a clay particle and the formation water that has a particular distribution of ions. Clays have an excess negative charge on their surface. When in contact with formation water, this charge attracts an excess of positive cations, normally Na+ together with their molecules of hydration water, into a region near the interface. The layer next to the clay surface, the Stern layer, has no anions, and is always present. Outside the Stern layer is the Gouy layer, through which the ion concentration gradually approaches that of free brine. The thickness of this layer increases as brine salinity decreases.
1005bound water, cation-exchange capacity, clay-bound water, dual water, effective porosity, electrical double layer, formation water, total porosity, wet-clay porosity
1006None
1007None
1008--
1009encapsulation
10101.n. [Drilling Fluids]
1011In drilling fluid parlance, the absorption of a polymer film onto cuttings and wellbore walls to form a coat or barrier. The term is usually applied to shale encapsulation by long-chain, acrylamide-acrylate (PHPA) polymers. Negative sites on PHPA may bond to positive sites on the clays in shales, although it is not well-defined how (or how well) encapsulation works. A viscous polymer film, according to some test results, slows diffusion of water molecules into the shale and thus slows hydration and disintegration. This does not prevent wellbore problems but can delay their onset.
1012acrylamide-acrylate polymer, clay, clay-water interaction, PHPA mud, potassium mud
1013None
1014None
1015--
1016es test
10171.n. [Drilling Fluids]
1018A test for oil-base and synthetic-base muds that indicates the emulsion and oil-wetting qualities of the sample. The test is performed by inserting the ES probe into a cup of 120°F [48.9°C] mud and pushing a test button. The ES meter automatically applies an increasing voltage (from 0 to 2000 volts) across an electrode gap in the probe. Maximum voltage that the mud will sustain across the gap before conducting current is displayed as the ES voltage. The modern ES meter has sine-wave circuitry, whereas older meters used square-wave circuits. (The older units should not be used because they do not correctly address the theory described in the reference below.) The ES sine-wave design and meaning of ES readings have been studied and were found to relate to an oil mud's oil-wetting of solids and to stability of the emulsion droplets in a complex fashion not yet understood.Reference:Growcock FB, Ellis CF and Schmidt DD: "Electrical Stability, Emulsion Stability, and Wettability of Invert Oil-Based Muds," SPE Drilling & Completion 9, no. 1 (March 1994): 39-46.
1019electrical stability test
1020None
1021None
1022--
1023eda
10241.n. [Geophysics]
1025A form of azimuthal anisotropy that occurs when fractures or microcracks are not horizontal. Waves that travel parallel to the fractures have a higher velocity than waves traveling perpendicular to fractures.
1026None
1027None
1028extensive dilatancy anisotropy
1029--
1030electrical impedance probe
10311.n. [Production Logging]
1032Another term for electric probe, a small sensor in a production logging tool that distinguishes between hydrocarbon and water in its vicinity as it is moved up and down a production well. The electric probe was the first type of local probe to be introduced, appearing initially in the early 1990s. Electric probes measure the local and average holdup of water and give an image of the flow structure across the well.Most electric probes emit a high-frequency current and measure the amplitude of the signal, and hence the impedance, of the fluid in a small sphere near the probe. The output is designed to be digital, indicating conductance when the probe is in front of water, and no conductance when it is in front of hydrocarbon. The water must have a certain minimum salinity, below which the device will not work.
1033bubble count, flow structure, local holdup, local probe, optical probe, production log, velocity image
1034electric probe, holdup image
1035None
1036--
1037endless tubing
10381.n. [Drilling]
1039Another term for coiled tubing, a long, continuous length of pipe wound on a spool. The pipe is straightened prior to pushing into a wellbore and rewound to coil the pipe back onto the transport and storage spool. Depending on the pipe diameter (1 in. to 4 1/2 in.) and the spool size, coiled tubing can range from 2,000 ft to 15,000 ft [610 to 4,570 m] or greater length.
1040coiled tubing drilling, packer
1041coiled tubing, CT, reeled tubing
1042None
1043--
1044endless tubing
10452.n. [Well Workover and Intervention]
1046A generic term relating to the use of a coiled tubing string and associated equipment. As a well-intervention method, coiled tubing techniques offer several key benefits over alternative well-intervention technologies. The ability to work safely under live well conditions, with a continuous string, enables fluids to be pumped at any time regardless of the position or direction of travel. This is a significant advantage in many applications. Installing an electrical conductor or hydraulic conduit further enhances the capability of a coiled tubing string and enables relatively complex intervention techniques to be applied safely.
1047None
1048coiled tubing, CT, reeled tubing
1049None
1050--
1051estimated ultimate recovery
10521.n. [Enhanced Oil Recovery, Formation Evaluation, Shale Gas]
1053The amount of oil and gas expected to be economically recovered from a reservoir or field by the end of its producing life. Estimated ultimate recovery can be referenced to a well, a field, or a basin.
1054None
1055None
1056None
1057--
1058eddy current measurement
10591.n. [Production Logging]
1060A technique for measuring the effect of pits and holes in the inner wall of a casing on a high-frequency electrical signal induced in the casing. The eddy-current measurement is used in conjunction with a flux-leakage measurement to determine casing corrosion, the latter being sensitive to the defects on both the inner and outer walls.The principle of measurement is similar to the openhole induction log, but at higher frequencies. A transmitter coil produces a magnetic field that induces eddy currents in the casing wall. These currents generate their own magnetic field that induces a signal in two closely spaced receiver coils. In smooth casing, these signals are the same, but if the inner wall is pitted, the signals are different. Transmitter-receiver combinations are placed on multiple pads applied against the casing at several azimuths to fully cover the casing wall.
1061azimuth, casing-inspection log, casing-potential profile, eddy current, flux leakage
1062None
1063None
1064--
1065electrical log
10661.n. [Formation Evaluation]
1067A log recorded using an electrical wireline. In this sense, the term refers to any log recorded on a wireline, whether it measures an electrical quantity or not. The term dates from the early days of logging when the only logs were the spontaneous potential and resistivity from conventional electrode devices.
1068electrode device, logging tool, resistivity log, spontaneous potential
1069None
1070None
1071--
1072electrical log
10732.n. [Formation Evaluation]
1074A wireline log of formation resistivity produced by a simple, unfocused arrangement of current emitting and measure electrodes. Conventional electrical devices have four electrodes-current emitting (A), current return (B), measure (M) and measure reference (N)-which may be placed in different configurations. The two most common configurations are the normal and lateral. The currents used are low frequency, typically less than 500 Hz. H.G. Doll recorded the first electrical log on September 5, 1927, in the Pechelbronn field, Alsace, France.
1075departure curve, electrode device, electrode resistivity, wireline log
1076None
1077electrical survey
1078--
1079enhanced diffusion
10801.adj. [Formation Evaluation]
1081A technique in nuclear magnetic resonance (NMR) logging based on a long echo spacing, specially chosen to enhance the diffusion of formation water. Echo spacings in standard NMR logs are too short to allow any significant diffusion relaxation from water. Long echo spacings, for example 3 s, cause diffusion relaxation to limit the maximum T2 from water. They also limit the maximum T2 from light hydrocarbons. However, there is a certain range of viscosity of medium oil that is less affected. The enhanced diffusion technique therefore permits the identification of some medium oils.
1082differential spectrum, diffusion relaxation, direct hydrocarbon typing, echo spacing, longitudinal relaxation, nuclear magnetic resonance measurement, shifted spectrum, transverse relaxation, wait time
1083None
1084None
1085--
1086euclidian dimension
10871.n. [Reservoir Characterization]
1088A dimension in Euclidian space. Euclidian dimensions are all orthogonal to each other (at right angles to each other) and refer to physical space with X, Y and Z components.
1089Euclidian distance
1090None
1091None
1092--
1093eddy current measurement
10941.n. [Production Logging]
1095A technique for measuring the effect of pits and holes in the inner wall of a casing on a high-frequency electrical signal induced in the casing. The eddy-current measurement is used in conjunction with a flux-leakage measurement to determine casing corrosion, the latter being sensitive to the defects on both the inner and outer walls.The principle of measurement is similar to the openhole induction log, but at higher frequencies. A transmitter coil produces a magnetic field that induces eddy currents in the casing wall. These currents generate their own magnetic field that induces a signal in two closely spaced receiver coils. In smooth casing, these signals are the same, but if the inner wall is pitted, the signals are different. Transmitter-receiver combinations are placed on multiple pads applied against the casing at several azimuths to fully cover the casing wall.
1096azimuth, casing-inspection log, casing-potential profile, eddy current, flux leakage
1097None
1098None
1099--
1100electrical resistance probe
11011.n. [Enhanced Oil Recovery]
1102An instrument used in a corrosion testing to determine metal loss. The probe directly measures the increase in resistance of a metal as its cross-sectional area is reduced by corrosion. At suitable times, once the readings are obtained, these numbers are converted into corrosion rates (mpy).An electrical resistance probe is also called an electrical coupon.
1103corrosion rate, metal loss
1104None
1105corrosion coupon
1106--
1107enhanced oil recovery
11081.n. [Enhanced Oil Recovery]
1109An oil recovery enhancement method using sophisticated techniques that alter the original properties of oil. Once ranked as a third stage of oil recovery that was carried out after secondary recovery, the techniques employed during enhanced oil recovery can actually be initiated at any time during the productive life of an oil reservoir. Its purpose is not only to restore formation pressure, but also to improve oil displacement or fluid flow in the reservoir.The three major types of enhanced oil recovery operations are chemical flooding (alkaline flooding or micellar-polymer flooding), miscible displacement (carbon dioxide [CO2] injection or hydrocarbon injection), and thermal recovery (steamflood or in-situ combustion). The optimal application of each type depends on reservoir temperature, pressure, depth, net pay, permeability, residual oil and water saturations, porosity and fluid properties such as oil API gravity and viscosity.Enhanced oil recovery is also known as improved oil recovery or tertiary recovery and it is abbreviated as EOR.
1110API gravity, chemical flooding, fluid flow, formation pressure, in-situ combustion, miscible displacement, primary recovery, residual oil, secondary recovery, steamflood, tertiary recovery, thermal recovery
1111None
1112EOR
1113--
1114euclidian distance
11151.n. [Reservoir Characterization]
1116The distance between two points in Euclidian space. Euclidian dimensions are all orthogonal to each other (they are all at right angles to each other) and refer to physical space.
1117Euclidian dimension
1118None
1119None
1120--
1121effective medium theory
11221.n. [Reservoir Characterization]
1123A method for determining the effective properties of random fields, commonly abbreviated EMT. Originally developed to estimate transport coefficients, this theory is based on the idea of replacing the inhomogeneous medium by an equivalent homogenous medium such that the fluctuations induced by restoring the heterogeneity average to zero.EMT is used to upscale parameters such as permeability for use in coarse-grained reservoir simulation studies. This use is controversial in reservoirs that are not homogeneous.ReferenceKilpatrick S: Percolation and conduction, Reviews of Modern Physics 45 (1973): 574-614.Mansoori J: "A Review of Basic Upscaling Procedures: Advantages and Disadvantages," in Yarus JM and Chambers RL (eds): Stochastic Modeling and Geostatistics, AAPG Computer Applications in Geology , no. 3. AAPG, Tulsa, Oklahoma, USA, 1994.
1124parameter, reservoir simulation
1125None
1126None
1127--
1128electrical stability test
11291.n. [Drilling Fluids]
1130A test for oil-base and synthetic-base muds that indicates the emulsion and oil-wetting qualities of the sample. The test is performed by inserting the ES probe into a cup of 120°F [48.9°C] mud and pushing a test button. The ES meter automatically applies an increasing voltage (from 0 to 2000 volts) across an electrode gap in the probe. Maximum voltage that the mud will sustain across the gap before conducting current is displayed as the ES voltage. The modern ES meter has sine-wave circuitry, whereas older meters used square-wave circuits. (The older units should not be used because they do not correctly address the theory described in the reference below.) The ES sine-wave design and meaning of ES readings have been studied and were found to relate to an oil mud's oil-wetting of solids and to stability of the emulsion droplets in a complex fashion not yet understood.Reference: Growcock FB, Ellis CF and Schmidt DD: "Electrical Stability, Emulsion Stability, and Wettability of Invert Oil-Based Muds," SPE Drilling & Completion 9, no. 1 (March 1994): 39-46.
1131high-pressure, high-temperature filtration test, jar test, oil mud, oil-base mud, stability meter, synthetic-base mud, wettability
1132None
1133ES test
1134--
1135entrance hole
11361.n. [Perforating]
1137The hole created in the internal surface of the casing or liner by the perforating charge or bullet. The entrance hole should be clean, free from burrs and round to create an efficient flow path between the reservoir and wellbore. Depending on gun size and standoff, the entrance hole is typically between 3/8" and 1/2" in diameter. The perforation charge design generally is optimized to provide maximum penetration while achieving a medium-size entrance hole. Special charge designs can be used when optimizing the entrance hole size is important, as in sand-control applications.
1138big-hole charge, sand control
1139None
1140None
1141--
1142evaporite
11431.n. [Geology]
1144A class of sedimentary minerals and sedimentary rocks that form by precipitation from evaporating aqueous fluid. Common evaporite minerals are halite, gypsum and anhydrite, which can form as seawater evaporates, and the rocks limestone and dolostone. Certain evaporite minerals, particularly halite, can form excellent cap rocks or seals for hydrocarbon traps because they have minimal porosity and they tend to deform plastically (as opposed to brittle fracturing that would facilitate leakage).
1145cap rock, carbonate, mineral, sabkha, salt dome, trap
1146None
1147None
1148--
1149effective permeability
11501.n. [Geology]
1151The ability to preferentially flow or transmit a particular fluid when other immiscible fluids are present in the reservoir (e.g., effective permeability of gas in a gas-water reservoir). The relative saturations of the fluids as well as the nature of the reservoir affect the effective permeability. In contrast, absolute permeability is the measurement of the permeability conducted when a single fluid or phase is present in the rock.
1152absolute permeability, immiscible, permeability, relative permeability, reservoir, saturation
1153None
1154None
1155--
1156electrical survey
11571.n. [Formation Evaluation]
1158A particular combination of a spontaneous potential log and three electrical logs consisting of a 16-in. [40-cm] short normal, a 64-in. [162-cm] long normal and an 18-ft, 8-in. [5.7-m] lateral. With this combination, it is possible to correct for the effects of invasion in many average logging environments. This combination is sometimes called a conventional electrical log or survey, or simply electrical log, and is also referred to as the ES.
1159departure curve, electrical log, electrode device, electrode resistivity, spontaneous potential
1160None
1161None
1162--
1163environmental corrections
11641.n. [Formation Evaluation]
1165The adjustments that must be made to log measurements to bring them back to the standard conditions for which the tool has been characterized. Different measurements require different corrections. For example resistivity measurements usually require correction for the borehole, invasion and shoulder beds, and may also be corrected for apparent dip, anisotropy and surrounding beds in horizontal wells. Density measurements require correction only for borehole size, while neutron porosity measurements require corrections for temperature, pressure and a large number of borehole and formation parameters. Not all corrections are significant in all cases. Corrections can be calculated manually, using charts, or applied through software. Conventionally, corrections are applied sequentially, as for example first borehole then invasion. In some situations, such as the combination of deep invasion and high apparent dip on a resistivity measurement, the corrections are too interdependent for sequential application to be accurate. The solution is iterative forward modeling.
1166apparent dip, borehole correction, iterative forward modeling, neutron porosity, shoulder bed, step profile
1167None
1168None
1169--
1170evaporitic
11711.adj. [Geology]
1172Pertaining to evaporite, a class of sedimentary minerals and sedimentary rocks that form by precipitation from evaporating aqueous fluid. Common evaporite minerals are halite, gypsum and anhydrite, which can form as seawater evaporates, and the rocks limestone and dolostone. Certain evaporite minerals, particularly halite, can form excellent cap rocks or seals for hydrocarbon traps because they have minimal porosity and they tend to deform plastically (as opposed to brittle fracturing that would facilitate leakage).
1173cap rock, carbonate, mineral, sabkha, salt dome, trap
1174None
1175None
1176--
1177effective porosity
11781.n. [Geology]
1179The interconnected pore volume or void space in a rock that contributes to fluid flow or permeability in a reservoir. Effective porosity excludes isolated pores and pore volume occupied by water adsorbed on clay minerals or other grains. Total porosity is the total void space in the rock whether or not it contributes to fluid flow. Effective porosity is typically less than total porosity.
1180fluid flow, total porosity
1181None
1182None
1183--
1184effective porosity
11852.n. [Formation Evaluation]
1186In the original definition of core analysts, the volume of connected pores in a unit volume of rock. Effective porosity in this sense is the total porosity less the isolated porosity. It is the porosity measured by most core analysis techniques that do not involve disaggregating the sample. In these techniques, the porosity is usually measured on totally dried core samples. Drying removes most of the clay-bound water.In log interpretation, effective porosity means the total porosity less the clay-bound water. The definition is based on the analysis of shaly formations, in which the clay-bound water is considered immobile and hence ineffective. Isolated porosity is rare in such formations and is ignored, being included in the effective porosity.Effective porosity on dried core samples is therefore greater than effective porosity from log analysis, and close to the total porosity from log analysis. In humidity-dried cores, part of the clay-bound water is not removed, and the difference is reduced.In some usage, the capillary-bound water is not considered part of the effective porosity. In this case effective porosity is synonymous with free fluid. Effective porosity is measured in volume/volume, percent or porosity units, p.u.
1187clay-bound water, free fluid, free water, isolated porosity, microporosity, small-pore water, total porosity
1188None
1189None
1190--
1191electrode device
11921.n. [Formation Evaluation]
1193A logging tool based on an arrangement of simple metallic electrodes working at low frequency (less than 500 Hz). The term includes conventional electrical logs, laterologs, micrologs and other microresistivity logs. Electrode devices are used for both wireline and measurements-while-drilling logs. In all electrode devices, a current (IO) and a voltage (VO) are measured on the appropriate electrodes or combinations of electrodes. The apparent formation resistivity is then determined by:	Ra = K VO / IO, where K is a system constant for the device concerned.
1194departure curve, electrical log, electrode resistivity, microlog, wireline log
1195None
1196None
1197--
1198eolian
11991.adj. [Geology]
1200Pertaining to the environment of deposition of sediments by wind, such as the sand dunes in a desert. Because fine-grained sediments such as clays are removed easily from wind-blown deposits, eolian sandstones are typically clean and well-sorted.
1201clay, depositional environment, depositional system, sabkha, sandstone, sediment
1202aeolian
1203None
1204--
1205evening tour
12061.n. [Drilling]
1207The work shift of a drilling crew that starts in the evening or late afternoon. Drilling operations usually occur around the clock because of the cost to rent arig. As a result, there are usually two separate crews working twelve-hour tours to keep the operation going. Some companies prefer three eight-hour tours: the evening tour starts at 4 PM; the graveyard tour is the overnight shift or the shift that begins at midnight. (Pronounced "tower" in many areas.)
1208tour
1209None
1210Antonyms:morning tour
1211--
1212effective shot density
12131.n. [Perforating]
1214A value that reflects the number of perforations per unit of length (usually feet) that are producing, or injecting, efficiently. Perforation efficiency may be compromised by gun failure or charge misfire, perforation debris, excessive standoff or poor orientation, or by combinations of these. The effective shot density may be used in treatment design models or to calculate likely productivity response.
1215perforation
1216None
1217None
1218--
1219electrohygrometer
12201.n. [Drilling Fluids]
1221A device for measuring the moisture in a gaseous atmosphere, such as the air, usually as percent relative humidity. Mechanical hygrometers detect moisture by elongation and shrinkage of a fiber or sheet or by a device attached to a needle on a dial. Electrohygrometers measure changes in an electrical property of a moisture-sensitive sensing probe and are more reliable. Determination of the aqueous-phase activity of oil muds by the Chenevert Method requires an electrohygrometer and a series of salt solutions for calibration.
1222activity of aqueous solutions, balanced-activity oil mud, Chenevert Method, oil mud, osmosis, relative humidity, zinc chloride
1223hygrometer
1224None
1225--
1226eor
12271.n. [Enhanced Oil Recovery]
1228Abbreviation for enhanced oil recovery, an oil recovery enhancement method using sophisticated techniques that alter the original properties of oil. Once ranked as a third stage of oil recovery that was carried out after secondary recovery, the techniques employed during enhanced oil recovery can actually be initiated at any time during the productive life of an oil reservoir. Its purpose is not only to restore formationpressure, but also to improve oil displacementor fluid flow in the reservoir. The three major types of enhanced oil recovery operations are chemical flooding (alkalineflooding or micellar-polymerflooding), miscibledisplacement (carbon dioxide[CO2] injection or hydrocarboninjection), and thermal recovery (steamflood or in-situcombustion). The optimal application of each type depends on reservoir temperature, pressure, depth, net pay, permeability, residual oil and water saturations, porosity and fluid properties such as oil APIgravity and viscosity. Enhanced oil recovery is also known as improved oil recoveryor tertiary recovery.
1229chemical flooding, miscible displacement, primary recovery, residual oil, secondary recovery, steamflood, thermal recovery
1230tertiary recovery
1231enhanced oil recovery
1232--
1233excess cement
12341.n. [Well Workover and Intervention]
1235The cement slurry remaining in the wellbore following a cement squeeze in which the objective is to squeeze slurry into the perforations and behind the casing or liner. The volume of slurry required to effect a successful squeeze is often difficult to estimate. In most cases, an excess allowance is made since a shortage of slurry would result in failure of the operation. Removal of the excess cement slurry before it sets has been a key objective in the development of modern cement-squeeze techniques.
1236cement squeeze
1237None
1238None
1239--
1240effective water saturation
12411.n. [Formation Evaluation]
1242The fraction of water in theporespace corresponding to the effective porosity. It is expressed in volume/volume, percent orsaturationunits. Unless otherwise stated, water saturation is the fraction offormation waterin theundisturbed zone. The saturation is known as the total water saturation if the pore space is thetotal porosity, but is called effective water saturation if the pore space is the effective porosity. If used without qualification, the term water saturation usually refers to the effective water saturation.
1243flushed-zone water saturation, moveable hydrocarbons, moved hydrocarbons, residual oil
1244water saturation
1245None
1246--
1247electrokinetic potential
12481.n. [Formation Evaluation]
1249The electromagnetic force, in millivolts, generated by an electrolyte flowing through a permeable medium. This potential is an unwanted contribution to the spontaneous potential (SP) log. In principle, there is no flow into a permeable reservoir at the time of logging, since the mudcake has isolated the reservoir from the borehole. However, it is possible for mudcakes and shales to produce an electrokinetic potential at the time of logging. In normal conditions, any potential is small and equal along the borehole, so that the effect on the SP is negligible. A significant electrokinetic potential can be generated in particular conditions, for example, high differential pressure or poor mudcakes.
1250bimetallism, differential pressure, shale baseline, spontaneous potential, static spontaneous potential
1251None
1252None
1253--
1254epithermal neutron porosity measurement
12551.adj. [Formation Evaluation]
1256A measurement based on the slowing down of neutrons between a source and one or more detectors that measure neutrons at the epithermal level, where their energy is above that of the surrounding matter, between approximately 0.4 and 10 eV. The slowing-down process is dominated by hydrogen, and is characterized by a slowing-down length. By measuring the neutrons at the epithermal level, rather than the thermal level, the response is a purer estimate of hydrogen index, unaffected by thermal absorbers. On the other hand, the count rate is smaller for the same source and source-detector spacing.Epithermal measurements have been made with both the compensated neutron technique and by using a pad pressed against the borehole wall with detectors focused into the formation.
1257chemical neutron source, compensated neutron log, excavation effect, hydrogen index, limestone porosity unit, limestone-compatible scale, neutron interactions, slowing-down length, thermal neutron porosity measurement
1258None
1259None
1260--
1261exit velocity
12621.n. [Drilling]
1263The speed the drilling fluid attains when accelerated through bit nozzles. The exit velocity is typically in the low-hundreds of feet per second. It has been reported that in certain shaly formations, an impingement velocity on the order of 250 feet per second is required to effectively remove newly created rock chips from the bottom of the hole. This impingement velocity is not, however, the same as the exit velocity, since the high-energy fluid jet loses velocity through viscous losses and conversions from kinetic energy to forms of potential energy occur once the fluid leaves the bit. For this reason, the well designer generally seeks to maximize the fluid velocity (or other measure of jet energy) to achieve maximum cleaning at the bottom of the hole.
1264bit nozzle, drilling fluid, jet velocity
1265None
1266None
1267--
1268effective wellbore radius
12691.n. [Well Testing]
1270The value of wellbore radius that produces equivalent results to those obtained using a skin factor of zero. It is possible to represent departures from ideal (zero skin) behavior by using the skin effect, or alternatively by changing the value of the effective wellbore radius. For a positive skin effect, effective wellbore radius is smaller than actual wellbore radius. For a negative skin effect, such as often obtained after well stimulation, effective wellbore radius is larger than actual well radius.
1271skin effect, skin factor
1272None
1273None
1274--
1275electromagnetic caliper
12761.n. [Production Logging]
1277An in-situ measurement of the inside diameter of a casing or tubing using an electromagnetic technique. As with the electromagnetic thickness measurement, and usually measured at the same time, a coil centered inside the casing generates an alternating magnetic field. Another coil farther up the tool measures the phase shift introduced by the casing. At high frequency, the signal penetrates less than a tenth of a millimeter into the casing, and the phase shift can be related to the casing internal diameter.Unlike a mechanical or ultrasonic caliper, the measurement does not respond to nonmagnetic scale. For the purpose of determining the true internal diameter, this is a disadvantage, but for the purpose of determining corrosion, it is an advantage.
1278casing-inspection log, casing-potential profile, electromagnetic thickness, inside diameter, multifinger caliper, phase shift, ultrasonic caliper
1279None
1280None
1281--
1282epsilon
12831.n. [Geophysics]
1284A P-wave parameter for a medium in which the elastic properties exhibit vertical transverse isotropy. Epsilon (ε) is the P-wave anisotropy parameter and equal to half the ratio of the difference between the horizontal and vertical P-wave velocities squared divided by the vertical P-wave velocity squared.ε ≡ ½ [(C11 − C33) / C33] = ½ [(VP⊥2 − VP∥2) / VP∥2]P-wave parameter (ε) for a medium in which the elastic properties exhibit vertical transverse isotropy, where C11 is the horizontal P-wave modulus (perpendicular to the symmetry axis), C33 is the vertical P-wave modulus (parallel to the symmetry axis), VP⊥ is the horizontal P-wave velocity and VP∥ is the vertical P-wave velocity.Reference: Thomsen L: “Weak Elastic Anisotropy,” Geophysics 51, no. 10 (October 1986): 1954–1966.
1285delta, gamma (γ), eta (η)
1286None
1287None
1288--
1289expendable gun
12901.n. [Perforating]
1291A perforating gun assembly that disintegrates upon firing, thereby reducing the volume and dimensions of retrieved components. Expendable guns are typically used where wellbore restrictions allow only limited access, as in through-tubing applications. The distortion caused to the gun assembly during firing would typically prevent recovery of a conventional gun design through the limited clearances. The expendable gun assembly breaks into small pieces that drop to the bottom of the well, leaving only a relatively small subassembly that is easily recovered to surface.
1292perforating gun
1293None
1294Antonyms:retrievable gun
1295--
1296elastic anisotropy
12971.n. [Geophysics]
1298The variation of elastic properties with direction. For example, elastic anisotropy occurs when seismic, or elastic, waves travel through rock at differing velocities in various directions. Elastic anisotropy occurs if there is a preferred alignment of a material’s fabric elements—crystals, grains, cracks, bedding planes, joints or fractures—on a scale smaller than the length of the wave. This alignment causes waves to propagate fastest in its direction.Elastic anisotropy is sometimes called seismic anisotropy, velocity anisotropy, traveltime anisotropy, acoustic anisotropy or slowness anisotropy.
1299None
1300None
1301None
1302--
1303electromagnetic method
13041.n. [Geophysics]
1305A group of techniques in which natural or artificially generated electric or magnetic fields are measured at the Earth's surface or in boreholes in order to map variations in the Earth's electrical properties (resistivity, permeability or permittivity). Most applications of surface electromagnetic methods today are for mineral and groundwater exploration or for shallow environmental mapping. Electromagnetic or electrical logging is, however, the main technique used in oil exploration to measure the amount of hydrocarbons in the pores of underground reservoirs. Inductive electromagnetic (EM) methods include a variety of low frequency (a few Hz to several kHz) techniques deploying large or small wire coils at or near the surface. In older usage, "electromagnetic method" tended to refer only to inductive methods. This term is now commonly used for any method employing electromagnetic fields, including methods that use direct current (electrical or resistivity methods) and induced polarization (IP), methods that use microwave frequencies (ground-penetrating radar), and methods that use natural electromagnetic fields (magnetotelluric methods).
1306array, cultural noise, diffusion equation, dipole, eddy current, electrical conductivity, electrical permittivity, fixed-source method, geometric, induced polarization, magnetics, magnetotelluric method, Maxwell's equations, moving-source method, Occam's inversion, parametric, perpendicular offset, probe, reflection, skin depth, survey, transient electromagnetic method, transverse electric mode, transverse magnetic mode
1307None
1308None
1309--
1310equalizing valve
13111.n. [Well Completions]
1312A device that is operated to equalize the pressure across a valve, plug or similar pressure or fluid isolation barrier. The operating mechanism on many pressure-sealing devices is rendered inoperable once the mechanism has been activated by pressure. In such cases, the pressure across the pressure barrier must be equalized before the barrier can be removed.
1313None
1314None
1315None
1316--
1317equalizing valve
13182.n. [Well Workover and Intervention]
1319A high-pressure valve, generally of small diameter, located on a conduit that runs between the two sides of an isolation valve or blowout preventer ram set. The forces acting on isolation devices such as blowout preventer rams can be extremely high, preventing the rams from being opened, or causing damage to the ram set seals during the opening process. The equalizing valve allows the pressure to be equalized across the ram set or isolation valve, enabling the device to be opened safely.
1320blowout preventer
1321None
1322None
1323--
1324expert system
13251.n. [Reservoir Characterization]
1326A computer system that uses a rule-based algorithm to provide expertise on a given subject. Many computer programs have been written for use in the oil field using rule-based approaches to provide expert systems. The rules are taken from an expert working in the field and are written in a way that attempts to reproduce the knowledge and approaches used by that expert to solve a range of actual problems. Most such programs are limited to specific disciplines such as dipmeter interpretation, electrofacies determination, reservoir characterization, blowout prevention or drilling fluid selection. Sometimes expert systems are written in computer languages such as LISP that easily handles rules, but once fully tested, expert systems are usually translated to BASIC, C or FORTRAN to be compiled into efficient applications or programs.
1327artificial intelligence, blowout, drilling fluid, reservoir characterization
1328None
1329None
1330--
1331elastic limit
13321.n. [Geology]
1333The yield point, or the point at which a material can no longer deform elastically. When the elastic limit is exceeded by an applied stress, permanent deformation occurs.
1334elastic deformation, plastic
1335yield point
1336None
1337--
1338electromagnetic propagation measurement
13391.n. [Formation Evaluation]
1340A measurement of the high frequency (about 1 GHz) dielectric properties of the formation. In a typical tool, a microwave transmitter is placed a few inches below two receivers separated by 4 cm [1.6 in.]. At this frequency, the response is best explained as the propagation of a wave. Thus the phase shift and attenuation of the wave between the receivers are measured and transformed to give the log measurements of propagation time and attenuation. Because of the short spacings, the measurement has excellent vertical resolution and reads within inches of the borehole wall except at high resistivity. Different transmitter and receiver spacings and orientations are used, leading to different arrays, such as the endfire array and the broadside array.An ideal measurement would give the plane wave properties of the formation. However, the geometry of the measurement precludes this, so that a correction, known as the spreading-loss correction, is needed for the attenuation and to a much smaller extent for the propagation time. The measurement is also affected by the dielectric properties and thickness of the mudcake. Borehole compensation is used to correct for sonde tilt or a rough borehole wall.
1341conductivity, electromagnetic propagation, filter cake, relative dielectric permittivity, spreading loss
1342None
1343None
1344--
1345equation of state
13461.n. [Enhanced Oil Recovery, Well Testing]
1347An equation that specifies fluid density as a function of pressure and temperature. A large body of scientific literature describes these functions for all kinds of hydrocarbons, and also for complex mixes of various hydrocarbons with other hydrocarbons and with other fluids. Once the components of a reservoir fluid are determined, the known hydrocarbon properties become a valuable tool in making further calculations of well-test results and predictions of future well and reservoir behavior.
1348constant composition expansion, hydrocarbon, pressure-composition diagram
1349None
1350None
1351--
1352exploration play
13531.n. [Geology, Shale Gas]
1354An area in which hydrocarbon accumulations or prospects of a given type occur.For example the shale gas plays in North America include the Barnett, Eagle Ford, Fayetteville, Haynesville, Marcellus, and Woodford, among many others. Outside North America, shale gas potential is being pursued in many parts of Europe, Africa, Asia, and South America.
1355accumulation, anomaly, basin, deep-water play, exploration, fairway, hydrocarbon, petroleum system, prospect, subsalt, trend
1356None
1357play
1358--
1359exploration play
13602.n. [Geology, Shale Gas]
1361A conceptual model for a style of hydrocarbon accumulation used by explorationists to develop prospects in a basin, region or trend and used by development personnel to continue exploiting a given trend. A play (or a group of interrelated plays) generally occurs in a single petroleum system.
1362accumulation, anomaly, basin, deep-water play, development, exploration play, fairway, hydrocarbon, petroleum system, prospect, reservoir, source rock, subsalt
1363None
1364play
1365--
1366electric gas lift valves
13671.n. [Production Testing]
1368A type of gas-lift valve that allows a gas-lift port size to be adjusted remotely from surface to positions from fully open to closed. These valves offer the possibility of changing gas-injection points without well intervention.
1369gas injection, gas lift, gas-lift valve
1370None
1371None
1372--
1373electromagnetic thickness
13741.n. [Production Logging]
1375An in-situ measurement of the thickness of a casing or tubing string using an electromagnetic technique. The result is presented as a type of casing-inspection log, giving an estimate of metal loss and detecting corrosion. In the usual method, a coil centered inside the casing generates an alternating magnetic field. Another coil farther up the tool measures the phase shift introduced by the casing. This phase shift depends on the casing-wall thickness and internal diameter, as well as the casing conductivity and magnetic permeability. The effects change at different frequencies, so that by varying the frequency, the thickness and internal diameter can be uniquely determined.Electromagnetic thickness can also be measured using other techniques, for example from a casing-potential profile or a flux-leakage measurement.
1376casing-inspection log, casing-potential profile, electromagnetic caliper, flux leakage, magnetic permeability, phase shift
1377None
1378None
1379--
1380equivalent sack
13811.n. [Drilling Fluids]
1382The weight of any cementitious material or blend based on the absolute volume of the cement. The term is normally used to define a sack of cement blend in which part of the cement has been replaced, on an absolute volume basis, by a pozzolanic material such as fly ash.
1383absolute volume, by weight of blend, fly ash, sack
1384None
1385None
1386--
1387extended reach drilling
13881.n. [Drilling]
1389Mobil Oil Company first used this term in the early 1980s for drilling directional wells in which the drilled horizontal reach (HR) attained at total depth (TD) exceeded the true vertical depth (TVD) by a factor greater than or equal to two. Extended-reach drilling (ERD) is particularly challenging for directional drilling and requires specialized planning to execute well construction.Since the term was coined, the scope of extended-reach drilling has broadened and the definition, which is now more flexible, includes deep wells with horizontal distance-to-depth, or H:V, ratios less than two. The drilling industry’s ERD database classifies wells, with increasing degree of well construction complexity, into low-, medium-, extended- and very extended-reach wells. Construction complexity depends on many factors, including water depth (for offshore wells), rig capability, geologic constraints and overall TVD. For example, a vertical well with TVD greater than 7,620 m [25,000 ft] is considered an extended-reach well. Also, depending on the conditions, drilling a well in deep water or through salt may be classified as ERD even if the well’s horizontal extent is not more than twice its TVD.
1390directional drilling, directional well, horizontal drilling
1391None
1392ERD, extended-reach drilling
1393--
1394electric gas lift valves
13951.n. [Production Testing]
1396A type of gas-lift valve that allows a gas-lift port size to be adjusted remotely from surface to positions from fully open to closed. These valves offer the possibility of changing gas-injection points without well intervention.
1397gas injection, gas lift, gas-lift valve
1398None
1399None
1400--
1401embrittlement
14021.n. [Drilling]
1403The process whereby steel components become less resistant to breakage and generally much weaker in tensile strength. While embrittlementhas many causes, in the oilfieldit is usually the result of exposure to gaseous or liquidhydrogen sulfide [H2S].On a molecular level, hydrogen ions work their way between the grain boundaries of the steel, where hydrogen ions recombine into molecular hydrogen [H2], taking up more space and weakening the bonds between the grains. The formation of molecular hydrogen can cause sudden metal failure due to cracking when the metal is subjected to tensile stress.This type of hydrogen-induced failure is produced when hydrogen atoms enter high strength steels. The failures due to hydrogen embrittlement normally have a period where no damage is observed, which is called incubation, followed by a sudden catastrophic failure.Hydrogen embrittlement is also called acid brittleness.
1404corrosion control, hydrogen embrittlement, hydrogen induced failures, tensile strength
1405None
1406None
1407--
1408erd
14091.n. [Drilling]
1410Abbreviation for extended-reach drilling. Mobil Oil Company first used this term in the early 1980s for drilling directional wells in which the drilled horizontal reach (HR) attained at total depth (TD) exceeded the true vertical depth (TVD) by a factor greater than or equal to two. Extended-reach drilling (ERD) is particularly challenging for directional drilling and requires specialized planning to execute well construction.Since the term was coined, the scope of extended-reach drilling has broadened and the definition, which is now more flexible, includes deep wells with horizontal distance-to-depth, or H:V, ratios less than two. The drilling industry’s ERD database classifies wells, with increasing degree of well construction complexity, into low-, medium-, extended- and very extended-reach wells. Construction complexity depends on many factors, including water depth (for offshore wells), rig capability, geologic constraints and overall TVD. For example, a vertical well with TVD greater than 7,620 m [25,000 ft] is considered an extended-reach well. Also, depending on the conditions, drilling a well in deep water or through salt may be classified as ERD even if the well’s horizontal extent is not more than twice its TVD.
1411directional drilling, directional well, horizontal drilling
1412None
1413extended-reach drilling
1414--
1415extended reach drilling
14161.n. [Drilling]
1417Mobil Oil Company first used this term in the early 1980s for drilling directional wells in which the drilled horizontal reach (HR) attained at total depth (TD) exceeded the true vertical depth (TVD) by a factor greater than or equal to two. Extended-reach drilling (ERD) is particularly challenging for directional drilling and requires specialized planning to execute well construction.Since the term was coined, the scope of extended-reach drilling has broadened and the definition, which is now more flexible, includes deep wells with horizontal distance-to-depth, or H:V, ratios less than two. The drilling industry’s ERD database classifies wells, with increasing degree of well construction complexity, into low-, medium-, extended- and very extended-reach wells. Construction complexity depends on many factors, including water depth (for offshore wells), rig capability, geologic constraints and overall TVD. For example, a vertical well with TVD greater than 7,620 m [25,000 ft] is considered an extended-reach well. Also, depending on the conditions, drilling a well in deep water or through salt may be classified as ERD even if the well’s horizontal extent is not more than twice its TVD.
1418directional drilling, directional well, horizontal drilling
1419None
1420ERD, extended reach drilling
1421--
1422electric probe
14231.n. [Production Logging]
1424A small sensor in a production logging tool that distinguishes between hydrocarbon and water in its vicinity as it is moved up and down a production well. The electric probe was the first type of local probe to be introduced, appearing initially in the early 1990s. Electric probes measure the local and average holdup of water and give an image of the flow structure across the well.Most electric probes emit a high-frequency current and measure the amplitude of the signal, and hence the impedance, of the fluid in a small sphere near the probe. The output is designed to be digital, indicating conductance when the probe is in front of water, and no conductance when it is in front of hydrocarbon. The water must have a certain minimum salinity, below which the device will not work.
1425bubble count, flow structure, holdup image, local holdup, local probe, optical probe, production log, velocity image
1426electrical impedance probe
1427None
1428--
1429emulsion
14301.n. [Drilling Fluids]
1431A dispersion of one immiscible liquid into another through the use of a chemical that reduces the interfacial tension between the two liquids to achieve stability. Two emulsion types are used as muds: (1) oil-in-water (or direct) emulsion, known as an "emulsion mud" and (2) water-in-oil (or invert) emulsion, known as an "invert emulsion mud." The former is classified as a water-base mud and the latter as an oil-base mud.
1432amides, amines, calcium chloride, coalescence, colloid, creaming, demulsifier, electrical stability test, emulsion mud, external phase, formation damage, HLB number, hydrophile-lipophile balance number, internal phase, invert-emulsion oil mud, invert-emulsion oil mud, oil-mud emulsifier, oil/water ratio, surface tension, water-base mud, water-in-oil emulsion, water-mud emulsifier
1433None
1434None
1435--
1436emulsion
14372.n. [Enhanced Oil Recovery]
1438A type of damage in which there is a combination of two or more immiscible fluids, including gas, that will not separate into individual components. Emulsions can form when fluid filtrates or injected fluids and reservoir fluids (for example oil or brine) mix, or when the pH of the producing fluid changes, such as after an acidizing treatment. Acidizing might change the pH from 6 or 7 to less than 4. Emulsions are normally found in gravel packs and perforations, or inside the formation.Most emulsions break easily when the source of the mixing energy is removed. However, some natural and artificial stabilizing agents, such as surfactants and small particle solids, keep fluids emulsified. Natural surfactants, created by bacteria or during the oil generation process, can be found in many waters and crude oils, while artificial surfactants are part of many drilling, completion or stimulation fluids. Among the most common solids that stabilize emulsions are iron sulfide, paraffin, sand, silt, clay, asphalt, scale and corrosion products.Emulsions are typically treated using mutual solvents.
1439asphaltenes, damage, fines migration
1440None
1441None
1442--
1443emulsion
14443.n. [Heavy Oil, Enhanced Oil Recovery]
1445A dispersion of droplets of one liquid in another liquid with which it is incompletely miscible. Emulsions can form in heavy oils that contain a significant amount of asphaltenes. The asphaltenes act as surfactants with treatment or formation water. The resulting emulsion droplets have high-energy bonds creating a very tight dispersion of droplets that is not easily separated. These surface-acting forces can create both oil-in-water and/or water-in-oil emulsions. Such emulsions require temperature and chemical treating in surface equipment in order to separate.
1446heavy oil, oil-in-water emulsion, surfactant, water-in-oil emulsion
1447None
1448None
1449--
1450erode
14511.vb. [Geology]
1452To cause or undergo erosion, the process of denudation of rocks, including physical, chemical and biological breakdown and transportation. The material from the rocks can be transported by wind, water, ice, or abrasive solid particles, or by mass-wasting, as in rock falls and landslides.
1453detrital, nonconformity, sequence boundary, unconformity, weathering
1454None
1455None
1456--
1457erode
14582.vb. [Drilling]
1459To cause or undergo erosion, the wearing away of material, usually rock or steel, by the continuous abrasive action of a solids-laden slurry. For erosion to occur usually requires a high fluid velocity, on the order of hundreds of feet per second, and some solids content, especially sand. Erosion may also occur in gas streams, again assuming the presence of sand particles. It is usually difficult to erode the wellbore wall significantly with drilling mud alone due to its relatively low velocity and high viscosity. There is also a dramatic "self-limiting" effect because even slight enlargement of the original gauge wellbore dramatically decreases fluid velocities.
1460gauge hole
1461None
1462None
1463--
1464extensive dilatancy anisotropy
14651.n. [Geophysics]
1466A form of azimuthal anisotropy that occurs when fractures or microcracks are not horizontal. Waves that travel parallel to the fractures have a higher velocity than waves traveling perpendicular to fractures.
1467azimuth, fracture, wave
1468None
1469EDA
1470--
1471electric submersible pump
14721.n. [Well Completions]
1473An artificial-lift system that utilizes a downhole pumping system that is electrically driven. The pump typically comprises several staged centrifugal pump sections that can be specifically configured to suit the production and wellbore characteristics of a given application. Electrical submersible pump systems are a common artificial-lift method, providing flexibility over a range of sizes and output flow capacities.
1474artificial lift, centrifugal pump
1475None
1476None
1477--
1478electric submersible pump
14792.n. [Heavy Oil]
1480An electric downhole pump used in heavy oil production that is designed with vane and fin configurations to accommodate frictional losses and pump efficiencies caused by heavy oil viscosity.
1481heavy oil
1482None
1483ESP
1484--
1485emulsion flow
14861.n. [Production Logging]
1487A multiphase-flow regime with oil as the continuous phase, in which water exists as small, approximately homogeneously distributed droplets. There may also be a thin film of water on the pipe wall.
1488bubble flow, flow structure, homogeneity, mist flow, multiphase flow
1489None
1490None
1491--
1492erosion
14931.n. [Geology]
1494The process of denudation of rocks, including physical, chemical and biological breakdown and transportation.
1495conformable, conformable, detrital, disconformity, filter-cake thickness, micrite, nonconformity, sequence boundary, unconformity, weathering
1496None
1497None
1498--
1499erosion
15002.n. [Geology]
1501The process by which material weathered from rocks is transported by wind, water, ice, or abrasive solid particles, or by mass-wasting, as in rock falls and landslides.
1502None
1503None
1504None
1505--
1506erosion
15073.n. [Drilling]
1508The wearing away of material, usually rock or steel, by the continuous abrasive action of a solids-laden slurry. For erosion to occur usually requires a high fluid velocity, on the order of hundreds of feet per second, and some solids content, especially sand. Erosion may also occur in gas streams, again assuming the presence of sand particles. It is usually difficult to erode the wellbore wall significantly with drilling mud alone due to its relatively low velocity and high viscosity. There is also a dramatic "self-limiting" effect because even slight enlargement of the original gauge wellbore dramatically decreases fluid velocities.
1509erode, gauge hole
1510None
1511None
1512--
1513external cutter
15141.n. [Well Workover and Intervention]
1515A downhole tool used to cut tubing or similar tubulars that have become stuck in the wellbore. The external cutter slips over the fish or tubing to be cut. Special hardened metal-cutters on the inside of the tool engage on the external surfaces of the fish. External cutters are generally used to remove the topmost, possibly damaged, portion of a fish to enable an overshot, or similar fishing tools, to engage on an undamaged surface.
1516None
1517None
1518None
1519--
1520electrical anisotropy
15211.n. [Formation Evaluation]
1522A difference in vertical and horizontal resistivity within a formation and at the scale of the resistivity measurement. Although there are several possible types of anisotropy, the term usually is used when the electrical properties are the same in all horizontal directions, but different in the vertical direction. For horizontal beds, this type of anisotropy is more fully known as transverse isotropy with a vertical axis of symmetry (TIV). The term may also refer to a difference in resistivities measured parallel and perpendicular to bedding.
1523bed, horizontal resistivity, parallel resistivity, perpendicular resistivity, vertical resistivity
1524None
1525None
1526--
1527emulsion mud
15281.n. [Drilling Fluids]
1529A water-base drilling fluid that contains dispersed oil or synthetic hydrocarbon as an internal phase. Early emulsion muds used diesel or crude oil dispersed into alkaline water-base muds. Synthetic liquids are now being substituted for oils in emulsion muds. Water-base muds containing certain synthetic liquids can be discharged in the Gulf of Mexico because they are environmentally safe and pass the EPA static sheen test and mysid shrimp toxicity tests.Reference: Rogers WF: "Oil-in-Water Emulsion Muds," in Composition and Properties of Oil Well Drilling Fluids, 3rd ed. Houston, Texas, USA: Gulf Publishing Company, 1963.
1530bioassay, carboxymethylcellulose, HLB number, hydrophile-lipophile balance number, interfacial tension, invert emulsion, lignin, lignosulfonate, milk emulsion mud, NPDES, oil-emulsion mud, oil-in-water emulsion, olefinic hydrocarbon, polyolefin, starch, surface tension, synthetic-base fluid, water-base drilling fluid, water-mud emulsifier
1531None
1532oil emulsion mud
1533--
1534erosion corrosion
15351.n. [Enhanced Oil Recovery]
1536A type of corrosion produced when easily removed scales (such as iron carbonate) that were initially protecting the metals in the pipe are eroded and the underlying metals are corroded.Erosion-corrosion is a common cause of failure in oilfield equipment. The attack is normally localized at changes of pipe sections, bends or elbows where there is high velocity or turbulent flow.
1537None
1538None
1539erosion-corrosion
1540--
1541external disturbance field
15421.n. [Geophysics]
1543A magnetic disturbance field generated by electric currents flowing in the ionosphere and magnetosphere and “mirror-currents” induced in the Earth and oceans by the external magnetic field time variations. The disturbance field, which is associated with diurnal field variations and magnetic storms, is affected by solar activity (solar wind), the interplanetary magnetic field and the Earth’s magnetic field.The external magnetic field exhibits variations on several time scales, which may affect the applicability of magnetic reference models. Very long-period variations are related to the solar cycle of about 11 years. Short-term variations result from daily changes in solar radiation, atmospheric tides and conductivity. Irregular time variations are influenced by the solar wind. Perturbed magnetic states, called magnetic storms, occur and show impulsive and unpredictable rapid time variations.
1544main magnetic field, crustal magnetic field, local magnetic interference
1545None
1546None
1547--
1548facies
15491.n. [Geology]
1550The overall characteristics of a rock unit that reflect its origin and differentiate the unit from others around it. Mineralogy and sedimentary source, fossil content, sedimentary structures and texture distinguish one facies from another.
1551depositional environment, lithofacies
1552None
1553None
1554--
1555facies
15562.n. [Reservoir Characterization]
1557The characteristics of a rock unit that reflect its origin and permit its differentiation from other rock units around it. Facies usually are characterized using all the geological characteristics known for that rock unit. In reservoir characterization and reservoir simulation, the facies properties that are most important are the petrophysical characteristics that control the fluid behavior in the facies. Electrofacies and other multivariate techniques are often used to determine these characteristics. Rock types rather than facies are more likely to be used in reservoir simulation.
1558None
1559None
1560None
1561--
1562final shut in period
15631.n. [Well Testing]
1564The final buildup sequence in a drillstem test. The initial shut-in period is usually followed immediately by an extended period of flow. The well is then shut in for the final buildup period. Data obtained during this period are analyzed to determine permeability thickness, kh, and skin effect, s. Final flow periods commonly range from 4 to 24 hours, and final buildup periods from 6 to 48 hours.
1565buildup test, drillstem test, final flow period, final flow rate, final flowing pressure, initial shut-in period, permeability thickness, skin effect
1566None
1567None
1568--
1569flow period
15701.n. [Well Testing]
1571Part of a well test when the well is flowing. It is usually specified prior to tests to ensure that a stable flow situation has been reached, or that the pressure disturbance has reached far enough into the formation to allow determination of a representative value for kh, or that any nearby boundaries could be recognized in a subsequent buildup.
1572final shut-in period, initial shut-in period, production period
1573None
1574None
1575--
1576formation evaluation while drilling
15771.n. [Drilling, Shale Gas]
1578Also known as logging while drilling or LWD, the measurement of formation properties during the excavation of the hole, or shortly thereafter, through the use of tools integrated into the bottomhole assembly. LWD, while sometimes risky and expensive, has the advantage of measuring properties of a formation before drilling fluids invade deeply. Further, many wellbores prove to be difficult or even impossible to measure with conventional wireline tools, especially highly deviated wells. In these situations, the LWD measurement ensures that some measurement of the subsurface is captured in the event that wireline operations are not possible.Timely LWD data can also be used to guide well placement so that the wellbore remains within the zone of interest or in the most productive portion of a reservoir, such as in highly variable shale reservoirs.
1579bottomhole assembly, deviated hole, measurements-while-drilling, wireline log
1580None
1581None
1582--
1583facies modeling
15841.n. [Reservoir Characterization]
1585The act of modeling a reservoir using knowledge of the facies that make up the reservoir and the depositional environments that the facies represent. The depositional characteristics will suggest rules concerning the geometries of the facies and the possible relationships between facies, especially where the facies have been related to each other within a stratigraphic sequence or a cyclothem. Facies modeling is often an important component of geostatistical reservoir characterization and facilitates construction of superior reservoir models for complex reservoirs.
1586None
1587None
1588None
1589--
1590fine
15911.adj. [Drilling Fluids]
1592A particle size term referring in the strict sense (API Bulletin 13C) to any particle in the size range 44 to 74 microns. More generally it is used to indicate any particle not removed by the shaker screens.
1593fines
1594None
1595None
1596--
1597flow profile
15981.n. [Production Logging]
1599A recording of the in-situ rate of fluid flow at different depths in a well, normally one completed for production or injection. The flow profile is a log recorded in a unit such as barrels per day, or as a percentage of the total flow from the reservoir in a production well or into the reservoir in an injection well. In single-phase flow, the profile can be determined from a flowmeter. In multiphase flow, it is desirable to show the flow rates of each of the phases, in which case a holdup log and either a flowmeter or a <a href="Display.cfm?Term=phase%20velocity%20log">phase <a href="Display.cfm?Term=velocity">velocity log are needed.
1600fluid flow, holdup log, injection well, multiphase flow, production log, single-phase flow, spinner flowmeter
1601None
1602None
1603--
1604formation factor
16051.n. [Formation Evaluation]
1606The ratio of the resistivity of a rock filled with water (Ro) to the resistivity of that water (Rw). G.E. Archie postulated that the formation factor (F) was a constant independent of Rwand solely a function of pore geometry (the Archie equation I). It has since been shown that F is independent of Rw only for a certain class of petrophysically simple rocks (Archie rocks). In rocks with conductive minerals, such as shaly sands, there is a more complex dependence. In such cases, the ratio Ro/Rw is known as the apparent formation factor and may vary with Rw , temperature and the type of ion in solution. The intrinsic formation factor is then defined as F corrected for the effect of shale, or else the value of Ro/Rw at the limit of high salinity (low Rw ). The correction for the effect of shale depends on the saturation equation used, for example Waxman-Smits, dual water, SGS or CRMM. Unless otherwise stated, the term formation factor usually refers to the apparent formation factor.F has been related to porosity (phi) by several formulae (Archie, Humble and others) that have the general expression F = a / phim, where a is a constant and m the porosity exponent.
1607Archie equation, Archie rock, dual water, Humble formula, laminated sand, porosity exponent, tortuosity
1608None
1609None
1610--
1611fairway
16121.n. [Geology]
1613The trend along which a particular geological feature is likely, such as a sand fairway or a hydrocarbon fairway. Prediction of conceptual fairways helps explorationists develop prospects. Along a sand fairway, for example, sand was transported and, presumably, was deposited, allowing an interpretation of the presence of reservoir rock in the fairway.
1614play, prospect, reservoir
1615None
1616None
1617--
1618fines
16191.n. [Drilling Fluids]
1620In a broad sense, very small particles, either in a mud or a mud additive sample.
1621bypass, colloidal solids, fine, formation damage, sand, silt
1622None
1623None
1624--
1625flow regime
16261.n. [Well Testing]
1627The predominant flow geometry reflected in a pressure-transient response that is most easily recognized in the log-log presentation of the pressure-change derivative. The most easily recognized flow regime is radial flow, which produces a constant or flat derivative. Spherical flow, which may result from a limited-entry completion, has a characteristic -1/2 slope in the derivative. Wellbore storage starts as a unit slope in pressure change and then the derivative bends over in a characteristic hump shape. Linear flow produced by flow to a fracture or a long horizontal well has a derivative slope of +1/2. Bilinear flow results when the fracture has finite conductivity and has a derivative slope of +1/4.
1628bilinear flow, finite-conductivity fracture, limited entry, linear flow, pressure-transient well tests, spherical flow
1629None
1630None
1631--
1632flow regime
16332.n. [Production Logging]
1634A description of the geometrical distribution of a multiphase fluid moving through a pipe. Many different terms are used to describe this distribution, the distinction between each one being qualitative and somewhat arbitrary. In vertical or moderately deviated pipes, the most common flow regimes for gas-liquid mixtures are bubble flow, dispersed bubble flow, plug flow, slug flow, froth flow, mist flow, churn flow and annular flow. For oil-water mixtures, the most common regimes are bubble flow, slug flow and emulsion flow. In horizontal wells, there may be stratified or wavy stratified flow in addition to many of the regimes observed in vertical wells.Two-phase flow regimes have often been presented as plots, or maps, with the phase velocities or functions of them on each axis. Earlier maps were named after their authors, for example Griffith-Wallis, Duns-Ros and Taitel-Dukler.
1635annular flow, bubble flow, churn flow, dispersed bubble flow, emulsion flow, flow structure, froth flow, mist flow, plug flow, slug flow, stratified flow, Taylor bubbles, two-phase flow
1636None
1637None
1638--
1639formation fracture pressure
16401.n. [Well Completions, Shale Gas, Well Testing, Well Workover and Intervention]
1641Pressure above which injection of fluids will cause the rock formation to fracture hydraulically.
1642fracture gradient, hydraulic fracturing
1643None
1644None
1645--
1646fall off test
16471.n. [Well Testing]
1648The measurement and analysis of pressure data taken after an injection well is shut in. These data are often the easiest transient well-test data to obtain. Wellhead pressure rises during injection, and if the well remains full of liquid after shut-in of an injector, the pressure can be measured at the surface, and bottomhole pressures can be calculated by adding the pressure from the hydrostatic column to the wellhead pressure. Since most water-injection wells are fractured during injection, and injection wells often go on vacuum, the fluid level can fall below the surface. Dealing with this complication requires reverting to bottomhole pressure gauges or sonic devices.
1649bottomhole pressure, injection well
1650None
1651None
1652--
1653fines migration
16541.n. [Well Completions]
1655The movement of fine clay, quartz particles or similar materials within the reservoir formation due to drag forces during production. Fines migration may result from an unconsolidated or inherently unstable formation, or from use of an incompatible treatment fluid that liberates fine particles. Unlike sand migration that is best stabilized, the material mobilized in fines migration should be produced to avoid near-wellbore damage.Fines migration causes particles suspended in the produced fluid to bridge the pore throats near the wellbore, reducing well productivity. Fines can include different materials such as clays (phyllosilicates smaller than 4 microns) and silts (silicates or aluminosilicates with sizes ranging from 4 to 64 microns). Kaolinite and illite are the most common migrating clays.Damage created by fines usually is located within a radius of 3 to 5 ft [1 to 2 m] of the wellbore, but can also occur in gravel-pack completions. In sandstone formations, hydrofluoric acid [HF] mixtures are used to dissolve fines. In carbonate formations, the goal is not to dissolve but rather to disperse fines in the wormholes, so hydrochloric [HCl] acid is used as the treatment fluid.
1656gravel pack, induced particle plugging, pore throat, treatment fluid, wormhole
1657None
1658None
1659--
1660flowback
16611.n. [Well Workover and Intervention]
1662The process of allowing fluids to flow from the well following a treatment, either in preparation for a subsequent phase of treatment or in preparation for cleanup and returning the well to production.
1663None
1664None
1665None
1666--
1667formation pressure
16681.n. [Geology]
1669The pressure of fluids within the pores of areservoir, usually hydrostatic pressure, or the pressure exerted by a column of water from theformation's depth to sea level. When impermeable rocks such as shales form as sediments are compacted, theirporefluids cannot always escape and must then support the total overlyingrockcolumn, leading to anomalously high formation pressures. Because reservoir pressure changes as fluids are produced from a reservoir, the pressure should be described as measured at a specific time, such as initial reservoir pressure.
1670abnormal pressure, absolute pressure, formation, geopressure, geostatic pressure, hydrostatic pressure, lithostatic pressure, normal pressure, overpressure, pressure gradient, shale, virgin pressure
1671None
1672pore pressure, reservoir pressure
1673--
1674formation pressure
16752.n. [Drilling]
1676The pressure of the subsurfaceformationfluids, commonly expressed as the density of fluid required in the wellbore to balance that pore pressure. A normal pressure gradient might require 9 lbm/galUS[1.08 kg/m3], while an extremely high gradient may need 18 lbm/galUS [2.16 kg/m3] or higher.
1677formation fluid, pore-pressure gradient, pressure gradient
1678None
1679None
1680--
1681formation pressure
16823.n. [Well Completions]
1683The pressure within the reservoir rock. The formation pressure value can be further categorized as relating to flowing well or shut-in conditions.
1684naturally flowing well, shut-in pressure
1685None
1686None
1687--
1688falloff test
16891.n. [Well Testing]
1690The measurement and analysis of pressure data taken after an injection well is shut in. These data are often the easiest transient well-test data to obtain. Wellhead pressure rises during injection, and if the well remains full of liquid after shut-in of an injector, the pressure can be measured at the surface, and bottomhole pressures can be calculated by adding the pressure from the hydrostatic column to the wellhead pressure. Since most water-injection wells are fractured during injection, and injection wells often go on vacuum, the fluid level can fall below the surface. Dealing with this complication requires reverting to bottomhole pressure gauges or sonic devices.
1691bottomhole pressure, injection well
1692None
1693None
1694--
1695fingerboard
16961.n. [Drilling]
1697The working platform approximately halfway up the derrick or mast in which the derrickman stores drillpipe and drill collars in an orderly fashion during trips out of the hole. The entire platform consists of a small section from which the derrickman works (called the monkeyboard), and several steel fingers with slots between them that keep the tops of the drillpipe in place.
1698drill collar, monkeyboard, racking back pipe, round trip, stand, trip out
1699None
1700None
1701--
1702flow concentrating
17031.adj. [Production Logging]
1704Referring to a type of spinner flowmeter in which most or all of the fluid flow in the well is diverted over the spinner by a device such as a basket or a packer.
1705basket flowmeter, deflector flowmeter, diverter flowmeter, flowmeter, fluid flow, packer flowmeter, petal basket flowmeter, production log, spinner flowmeter, torque flowmeter
1706None
1707None
1708--
1709formation water
17101.n. [Geology]
1711Water that occurs naturally within the pores of rock. Water from fluids introduced to a formation through drilling or other interference, such as mud and seawater, does not constitute formation water. Formation water, or interstitial water, might not have been the water present when the rock originally formed. In contrast, connate water is the water trapped in the pores of a rock during its formation, and may be called fossil water.
1712brine, connate water, fresh water, interstitial water, pore
1713None
1714None
1715--
1716formation water
17172.n. [Formation Evaluation]
1718Water in the undisturbed zone around a borehole. The resistivity and other properties of this water are used in the interpretation of measurements made in the borehole or from the surface. Although formation water normally is the same as the geological formation water, or interstitial water, it may be different because of the influx of injection water.
1719Archie equation, connate water, formation factor, injection water, interstitial water, true resistivity
1720None
1721None
1722--
1723fann viscometer
17241.n. [Drilling Fluids]
1725Also known as direct-indicating viscometer or V-G meter, an instrument used to measureviscosityand gel strength ofdrilling mud. The direct-indicating viscometer is a rotational cylinder and bob instrument. Two speeds of rotation, 300 and 600 rpm, are available in all instruments, but some are 6- or variable-speed. It is called "direct-indicating" because at a given speed, the dial reading is a truecentipoise viscosity. For example, at 300 rpm, the dial reading (511 sec-1) is a true viscosity. Binghamplasticrheologicalparameters are easily calculated from direct-indicating viscometer readings:PV(in units of cp) = 600 dial - 300 dial andYP(in units of lb/100 ft2) = 300 dial - PV. Gel strength is also directly read as dial readings inoilfieldunits of lb/100 ft2.
1726Bingham plastic model, deflocculant, gel strength, Herschel-Bulkley fluid, Newtonian fluid, non-Newtonian fluid, plastic viscosity, power-law fluid, rheological property, yield point
1727direct-indicating viscometer, V-G meter
1728None
1729--
1730fire flooding
17311.n. [Enhanced Oil Recovery, Heavy Oil]
1732A method of thermal recovery in which a flame front is generated in the reservoir by igniting a fire at the sandface of an injection well. Continuous injection of air or other gas mixture with high oxygen content will maintain the flame front. As the fire burns, it moves through the reservoir toward production wells. Heat from the fire reduces oil viscosity and helps vaporize reservoir water to steam. The steam, hot water, combustion gas and a bank of distilled solvent all act to drive oil in front of the fire toward production wells.
1733gas injection, in-situ combustion
1734None
1735None
1736--
1737flowing well
17381.n. [Well Testing]
1739A well in which the formation pressure is sufficient to produce oil at a commercial rate without requiring a pump. Most reservoirs are initially at pressures high enough to allow a well to flow naturally.
1740formation pressure
1741None
1742Antonyms:pumping well
1743--
1744formic acid
17451.n. [Well Workover and Intervention]
1746An organic acid used in the stimulation of high-temperature oil and gas wells in which conventional hydrochloric acid systems cannot be adequately inhibited, or where contact time with tubulars is likely to be extended.
1747gas well, hydrochloric acid, inhibit, oil well
1748None
1749None
1750--
1751formic acid
17522.n. [Enhanced Oil Recovery]
1753An organic acid [HCOOH] used in oil- and gas-well stimulation treatments. Formic acid has an advantage over HCl in that formic acid is easier to inhibit against pipe corrosion at temperatures as high as 400°F [204°C]. Formic acid is intermediate in strength between hydrochloric acid [HCl] and acetic acid. Additionally, formic acid corrodes steel more uniformly than does HCl and causes less pitting.
1754acetic acid, hydrochloric acid, organic acid
1755None
1756None
1757--
1758farmor
17591.n. [Oil and Gas Business]
1760The party that originally owns the leasehold interest and assigns the farmout.
1761farmee, farmout
1762None
1763None
1764--
1765fireflooding
17661.n. [Heavy Oil, Enhanced Oil Recovery]
1767A method of thermal recovery in which a flame front is generated in the reservoir by igniting a fire at the sandface of an injection well. Continuous injection of air or other gas mixture with high oxygen content will maintain the flame front. As the fire burns, it moves through the reservoir toward production wells. Heat from the fire reduces oil viscosity and helps vaporize reservoir water to steam. The steam, hot water, combustion gas and a bank of distilled solvent all act to drive oil in front of the fire toward production wells.
1768gas injection, in-situ combustion
1769None
1770None
1771--
1772flowline
17731.n. [Drilling]
1774The large-diameter metal pipe that connects the bell nipple under the rotary table to the possum belly at the mud tanks. The flowline is simply an inclined, gravity-flow conduit to direct mud coming out the top of the wellbore to the mud surface-treating equipment. When drilling certain highly reactive clays, called "gumbo," the flowline may become plugged and require considerable effort by the rig crew to keep it open and flowing. In addition, the flowline is usually fitted with a crude paddle-type flow-measuring device commonly called a "flow show" that may give the driller the first indication that the well is flowing.
1775bell nipple, circulation system, gumbo, rotary table
1776None
1777mud return line
1778--
1779flowline
17802.n. [Production Testing]
1781A surface pipeline carrying oil, gas or water that connects the wellhead to a manifold or to production facilities, such as heater-treaters and separators.
1782heater, separator
1783None
1784None
1785--
1786forward multiple contact test
17871.n. [Enhanced Oil Recovery]
1788A laboratory test to determine the phase envelope between lean gas and oil by equilibrating a gas sample several times with fresh samples of oil. In a forward-contact test, light and intermediate components are stripped from the oil by multiple contacts with the gas. The test also indicates how many contacts are required before the gas with added components becomes miscible with the oil. The molar ratios at each contact step are typically designed using PVT simulation software that incorporates the fluid composition at each contact.
1789backward multiple-contact test, vaporizing drive
1790None
1791None
1792--
1793farmout
17941.n. [Oil and Gas Business]
1795A contractual agreement with an owner who holds a working interest in an oil and gas lease to assign all or part of that interest to another party in exchange for fulfilling contractually specified conditions. The farmout agreement often stipulates that the other party must drill a well to a certain depth, at a specified location, within a certain time frame; furthermore, the well typically must be completed as a commercial producer to earn an assignment. The assignor of the interest usually reserves a specified overriding royalty interest, with the option to convert the overriding royalty interest to a specified working interest upon payout of drilling and production expenses, otherwise known as a back-in after payout (BIAPO).
1796back-in, farmee, farmor, overriding royalty interest, working interest
1797None
1798None
1799--
1800firing head
18011.n. [Perforating]
1802A mechanical or electronic device used to detonate perforating charges conveyed by tubing, drillpipe, coiled tubing or slickline. This term thus connotes any such device that is not initiated electrically from surface by wireline. A mechanical firing head consists of a percussion detonator that is struck by a firing pin. An electronic firing head is battery powered, to initiate an electric detonator. Electronic firing head systems are used with slickline, coiled tubing and TCP.
1803coiled tubing, perforating charge, tubing-conveyed perforating
1804None
1805None
1806--
1807flowmeter
18081.n. [Well Workover and Intervention]
1809A device installed in a pump manifold or treating line to measure the fluid flow rate. Flowmeters can be used to measure the flow rates of liquid or gas and are available in various configurations and with differing operating principles.
1810fluid flow, pump manifold
1811None
1812None
1813--
1814flowmeter
18152.n. [Production Logging]
1816A device for measuring in-situ the velocity of fluid flow in a well, usually one completed for production or injection. The most common device is the spinner flowmeter, but torque flowmeters and crosscorrelation flowmeters also are used. In the 1940s and 1950s, various other surface-metering techniques were tried, but spinner flowmeters emerged as the most suitable for measuring downhole velocities. Spinner and torque flowmeters measure the average velocity of the fluids crossing the device, while crosscorrelation flowmeters measure the velocity of a particular phase.Although not normally called flowmeters, various other techniques measure flow velocity, for example water-flow logs, phase-velocity logs, distributed-temperature logs and even audio measurements.
1817audio measurement, average velocity, crosscorrelation flowmeter, distributed-temperature log, fluid flow, phase-velocity log, production log, spinner flowmeter, torque flowmeter, water-flow log
1818None
1819None
1820--
1821flowmeter
18223.n. [Production Testing]
1823An instrument that measures the flow rate of fluids through a pipeline. There are several types of flowmeters, including the differential-pressure meter, orifice meter, positive-displacement meter, vortex meter and multiphase meters.
1824multiphase meter, orifice meter
1825None
1826None
1827--
1828four component seismic data
18291.n. [Geophysics]
1830Four-component (4C) borehole or marine seismic data are typically acquired using three orthogonally-oriented geophones and a hydrophone within an ocean-bottom sensor (deployed in node-type systems as well as cables). Provided the system is in contact with the seabed or the borehole wall, the addition of geophones allows measurement of shear (S) waves, whereas the hydrophone measures compressional (P) waves.
1831borehole seismic data, compressional wave, geophone, multicomponent seismic data, ocean-bottom cable, P-wave, shear wave
1832None
1833None
1834--
1835fast neutron reaction
18361.n. [Formation Evaluation]
1837A neutron interaction in which the neutron is absorbed by the target nuclei, which then emit nuclear particles such as alpha or beta particles, gamma rays, protons or additional neutrons. Fast neutron reactions have a small probability of occurrence relative to the other principal interactions, except at high neutron energy.
1838chemical neutron source, inelastic neutron scattering, neutron capture, neutron generator, neutron interactions
1839None
1840None
1841--
1842fish
18431.n. [Drilling]
1844Anything left in a wellbore. It does not matter whether the fish consists of junk metal, a hand tool, a length of drillpipe or drill collars, or an expensive MWD and directional drilling package. Once the component is lost, it is properly referred to as simply "the fish." Typically, anything put into the hole is accurately measured and sketched, so that appropriate fishing tools can be selected if the item must be fished out of the hole.
1845back off, drill collar, fishing tool, sidetrack, washover pipe
1846None
1847None
1848--
1849fish
18502.vb. [Drilling]
1851To attempt to retrieve a fish from a wellbore. Where available, specially skilled individuals, aptly called fishermen, are called onto location to direct and assist with the fishing operations. Depending on the type of fish, the manner in which it was lost, regulatory requirements (for example a fish that includes a nuclear source, such as certain well logging tools), and the value of the fish if recovered, fishing operations may be immediately successful or may be attempted unsuccessfully for several days or even weeks.
1852None
1853None
1854None
1855--
1856fish
18573.n. [Formation Evaluation]
1858The surface electrode used as the reference electrode for the spontaneous potential (SP) measurement. The metal electrode is attached to the end of a long electric cable and typically placed in the mud pit, or, in the case of an offshore rig, in the sea. The SP is a measurement of the natural electrical potential between an electrode in the well and the fixed reference electrode on surface.
1859mud pit, shale baseline, spontaneous potential
1860None
1861None
1862--
1863flue gas
18641.n. [Enhanced Oil Recovery]
1865A gas generated by burning hydrocarbons with air; it is sometimes used as an enhanced oil recovery (EOR) injectant. The composition consists mainly of nitrogen, carbon dioxide, water vapor and excess oxygen with some impurities, such as carbon monoxide, nitrogen oxides and sulfur oxides. Generally, more carbon dioxide in the flue gas results in a better recovery factor for EOR. By contrast, using more nitrogen results in a lower recovery factor for EOR. However, high concentration of impurities, such as oxygen, nitrous oxides and carbon monoxide, can cause corrosion in production tubulars and surface equipment.
1866None
1867None
1868None
1869--
1870four component seismic data
18711.n. [Geophysics]
1872Four-component (4C) borehole or marine seismic data are typically acquired using three orthogonally-oriented geophones and a hydrophone within an ocean-bottom sensor (deployed in node-type systems as well as cables). Provided the system is in contact with the seabed or the borehole wall, the addition of geophones allows measurement of shear (S) waves, whereas the hydrophone measures compressional (P) waves.
1873borehole seismic data, compressional wave, geophone, ocean-bottom cable, P-wave, shear wave
1874None
1875None
1876--
1877fast neutron reaction
18781.n. [Formation Evaluation]
1879A neutron interaction in which the neutron is absorbed by the target nuclei, which then emit nuclear particles such as alpha or beta particles, gamma rays, protons or additional neutrons. Fast neutron reactions have a small probability of occurrence relative to the other principal interactions, except at high neutron energy.
1880chemical neutron source, inelastic neutron scattering, neutron capture, neutron generator, neutron interactions
1881None
1882None
1883--
1884fish eye
18851.n. [Drilling Fluids]
1886A slang term for a globule of partly hydrated polymer caused by poor dispersion during the mixing process (commonly a result of adding the product too fast). Fish eyes are typically 0.2 to 0.5 inches in size and consist of a granule of unhydrated polymer surrounded by a gelatinous covering of hydrated polymer, which prevents water from entering to complete the hydration process. Thus, once formed, fish eyes do not disperse and the product is removed on the shaker screens and wasted.
1887microgel
1888None
1889None
1890--
1891fluid compressibility
18921.n. [Well Testing]
1893The relative change in fluid volume related to a unit change in pressure. This is usually expressed as volume change per unit volume of fluid per psi of pressure change. Gas has higher compressibility than liquid (oil or water).
1894None
1895None
1896None
1897--
1898fourier transform infrared spectroscopy
18991.n. [Formation Evaluation]
1900A technique for quantitative mineralogical analysis of a sample of rock by measuring the effect of midrange infrared radiation transmitted through the sample. This radiation excites vibrations in the chemical bonds within the mineral molecules at particular frequencies characteristic of each bond. The transmitted radiation is compared with the spectral standards for a wide variety of minerals to determine the abundance of each mineral in the sample. Typically, a core plug is ground finely and a small (approximately 1 g) representative sample selected and dispersed in a potassium bromide matrix for the measurement.
1901core plug, X-ray fluorescence (XRF)
1902None
1903FTIR
1904--
1905fatty acid
19061.n. [Drilling Fluids]
1907A type of organic acid derived from animal and vegetable fats and oils. Fatty acids are the raw materials used in the manufacture of many drilling-fluid additives, such as emulsifiers, oil-wetting agents and lubricants. Tall-oil fatty acids are distilled from conifer trees. Animal and vegetable fats and oils are triglycerides, which are hydrolyzed to give fatty acids (and glycerol). Fatty acids from animals are mostly saturated acids, having single bonds between carbon atoms. Tall oils and vegetable oils yield both saturated and unsaturated (double- and triple-bond) fatty acids.
1908aluminum stearate, amides, amines, bland coring fluid, drilling fluid, emulsifier, fatty-acid soap, greasing out, hydrolysis, oil mud, oil-mud emulsifier, quaternary amine, rheology modifier, soap, stearate, sulfate-reducing bacteria, synthetic-base fluid, tall oil, water mud
1909None
1910None
1911--
1912fishing bell
19131.n. [Formation Evaluation]
1914Also known as the head, the device that connects the end of theloggingcableor thebridleto the top of the logging tool. It contains theweak point, so that when the weak point is broken and the cable removed, the uppermost assembly left in the hole is the head. The top of the head is specially designed to easefishingof the logging tool.
1915logging tool
1916None
1917None
1918--
1919fluid contact
19201.n. [Geology]
1921The interface that separates fluids of different densities in a reservoir. Horizontal contacts are usually assumed, although tilted contacts occur in some reservoirs. The contact between fluids is usually gradual rather than sharp, forming a transition zone of mixed fluid. A mixed-fluid reservoir will stratify according to fluid density, with gas at the top, oil in the middle, and water below. Production of fluids often perturbs the fluid contacts in a reservoir.
1922condensate, gas-oil contact, gas-water contact, oil-water contact, stratified flow, transition zone, wet gas
1923None
1924None
1925--
1926frac balls
19271.n. [Well Completions, Well Workover and Intervention]
1928Another term for ball sealers, small spheres designed to seal perforations that are accepting the most fluid, thereby diverting reservoir treatments to other portions of the target zone. Ball sealers are incorporated into the treatment fluid and pumped with it. The effectiveness of this type of mechanical diversion to keep the balls in place is strongly dependent on the differential pressure across the perforation and the geometry of the perforation itself.
1929chemical diversion, mechanical diversion
1930None
1931None
1932--
1933fault
19341.n. [Geology]
1935A break or planar surface in brittle rock across which there is observable displacement. Depending on the relative direction of displacement between the rocks, or fault blocks, on either side of the fault, its movement is described as normal, reverse or strike-slip. According to terminology derived from the mining industry, the fault block above the fault surface is called the hanging wall, while the fault block below the fault is the footwall. Given the geological complexity of some faulted rocks and rocks that have undergone more than one episode of deformation, it can be difficult to distinguish between the various types of faults. Also, areas deformed more than once or that have undergone continual deformation might have fault surfaces that are rotated from their original orientations, so interpretation is not straightforward. In a normal fault, the hanging wall moves down relative to the footwall along the dip of the fault surface, which is steep, from 45o to 90o. A growth fault is a type of normal fault that forms during sedimentation and typically has thicker strata on the downthrown hanging wall than the footwall. A reverse fault forms when the hanging wall moves up relative to the footwall parallel to the dip of the fault surface. A thrust fault, sometimes called an overthrust, is a reverse fault in which the fault plane has a shallow dip, typically much less than 45o.Movement of normal and reverse faults can also be oblique as opposed to purely parallel to the dip direction of the fault plane. The motion along a strike-slip fault, also known as a transcurrent or wrench fault, is parallel to the strike of the fault surface, and the fault blocks move sideways past each other. The fault surfaces of strike-slip faults are usually nearly vertical. A strike-slip fault in which the block across the fault moves to the right is described as a dextral strike-slip fault. If it moves left, the relative motion is described as sinistral. A transform fault is a particular type of strike-slip fault that is a boundary of an oceanic tectonic plate. The actual movement of a transform fault is opposite to its apparent displacement.The presence of a fault can be detected by observing characteristics of rocks such as changes in lithology from one fault block to the next, breaks and offsets between strata or seismic events, and changes in formation pressure in wells that penetrate both sides of a fault. Some fault surfaces contain relatively coarse rubble that can act as a conduit for migrating oil or gas, whereas the surfaces of other faults are smeared with impermeable clays or broken grains that can act as a fault seal.
1936anomaly, antithetic fault, aulacogen, cataclastic, collision, competent, decollement, en echelon, fault trap, flower structure, fracture, Global Positioning System, graben, growth fault, horst, incompetent, inversion, lithologic contact, normal fault, offset, orogeny, plate tectonics, reverse fault, sinistral, strain, strike-slip fault, structural trap, structure, synthetic fault, thrust fault, transform fault, transpression, transtension, two-dimensional survey, wrench fault
1937None
1938None
1939--
1940fishing neck
19411.n. [Well Workover and Intervention]
1942The surface on which a fishing tool engages when retrieving tubing, tools or equipment stuck or lost in a wellbore. Tools and equipment that are temporarily installed in a wellbore are generally equipped with a specific fishing-neck profile to enable the running and retrieval tools to reliably engage and release.
1943fishing tool
1944None
1945None
1946--
1947fluid density log
19481.n. [Production Logging]
1949A record of the density, or changes in density, of fluids in a production or injection well. Since gas, oil and water all have different densities, the log can determine the percentage, or holdup, of the different fluids, directly in the case of biphasic flow, and in combination with other measurements for triphasic flow. Fluid density is measured by a gradiomanometer or a nuclear fluid densimeter, and can also be derived from the depth derivative of a pressure sensor.
1950holdup log, injection well, nuclear fluid densimeter, production log
1951None
1952None
1953--
1954frac fluid
19551.n. [Shale Gas, Well Completions]
1956An abbreviation for fracturing fluid, a fluid injected into a well as part of a stimulation operation. Fracturing fluids for shale reservoirs usually contain water, proppant, and a small amount of nonaqueous fluids designed to reduce friction pressure while pumping the fluid into the wellbore. These fluids typically include gels, friction reducers, crosslinkers, breakers and surfactants similar to household cosmetics and cleaning products; these additives are selected for their capability to improve the results of the stimulation operation and the productivity of the well.
1957None
1958None
1959None
1960--
1961feldspar
19621.n. [Geology]
1963[alkali feldspar (K,Na)AlSi3O8][plagioclase feldspar NaAlSi3O8 - CaAl2Si2O8]A group of rock-forming silicate minerals that are essential constituents of igneous rocks and are common in sandstones. Feldspar can weather to form clay minerals. Feldspar can occur in all three major rock types and forms approximately 60% of the crust of the Earth.
1964felsic, granite, illite, kaolinite, metamorphic, porosity, sandstone, sediment, sedimentary
1965None
1966None
1967--
1968fishing tool
19691.n. [Drilling]
1970A general term for special mechanical devices used to aid the recovery of equipment lost downhole. These devices generally fall into four classes: diagnostic, inside grappling, outside grappling, and force intensifiers or jars. Diagnostic devices may range from a simple impression block made in a soft metal, usually lead, that is dropped rapidly onto the top of the fish so that upon inspection at the surface, the fisherman may be able to custom design a tool to facilitate attachment to and removal of the fish. Other diagnostic tools may include electronic instruments and even downhole sonic or visual-bandwidth cameras. Inside grappling devices, usually called spears, generally have a tapered and threaded profile, enabling the fisherman to first guide the tool into the top of the fish, and then thread the fishing tool into the top of the fish so that recovery may be attempted. Outside grappling devices, usually called overshots, are fitted with threads or another shape that "swallows" the fish and does not release it as it is pulled out of the hole. Overshots are also fitted with a crude drilling surface at the bottom, so that the overshot may be lightly drilled over the fish, sometimes to remove rock or metallic junk that may be part of the sticking mechanism. Jars are mechanical downhole hammers, which enable the fisherman to deliver high-impact loads to the fish, far in excess of what could be applied in a quasi-static pull from the surface.
1971cut-and-thread fishing technique, intensifier, jar, mechanical sticking, overshot, safety joint, washover pipe
1972None
1973None
1974--
1975fluid flow
19761.n. [Reservoir Characterization]
1977The movement of fluid through pores and fractures within permeable rocks in a reservoir. Generally, the fluid flow is assumed to follow Darcy's law, so the fluid flow may be simulated with a model of the reservoir.
1978fracture
1979None
1980None
1981--
1982frac gel
19831.n. [Well Workover and Intervention]
1984The primary fluid used in hydraulic fracturing operations. Several chemical additives generally will be added to the frac gel to form a treatment fluid specifically designed for the anticipated wellbore, reservoir and operating conditions.
1985hydraulic fracturing, treatment fluid
1986None
1987None
1988--
1989ferrous sulfide
19901.n. [Enhanced Oil Recovery]
1991A corrosion by-product [FeS2] formed when hydrogen sulfide [H2S] contacts the iron [Fe] present in steel.Ferrous sulfide is a black crystalline material at bottomhole conditions. However, when it contacts air at surface, it will be converted into iron oxide, which is a red-brown compound.Ferrous sulfide is also called iron sulfide.
1992hydrogen sulfide
1993None
1994iron oxide
1995--
1996five spot
19971.n. [Enhanced Oil Recovery, Heavy Oil]
1998An injection pattern in which four input or injection wells are located at the corners of a square and the production well sits in the center. The injection fluid, which is normally water, steam or gas, is injected simultaneously through the four injection wells to displace the oil toward the central production well.
1999injection pattern, injection well, inverted five-spot
2000None
2001None
2002--
2003fluid interface log
20041.n. [Production Logging]
2005An in-situ measurement of the flow profile made by pumping different fluids down the tubing and casing and observing the interface between them. The fluids are normally both water, but one may be fresh and the other salty, or else one may contain some tracer, so that the interface can be detected by a production-logging tool. After the tubing is run to the bottom of the well, an interface is introduced by one of two methods. In the static method, the total flow rate is held constant and the relative flow rate of the two streams is changed. The location of the interface after each change is used to determine the flow profile. In the dynamic method, one fluid is pumped at different rates. The log was used in the 1950s and 1960s but is now used rarely, having been replaced by fluid-density logs and others.
2006None
2007None
2008None
2009--
2010frac gradient
20111.n. [Well Workover and Intervention]
2012The pressure gradient, generally stated in psi/ft [kPa/m], at which a specific formation interval breaks down and accepts fluid. Determining the frac gradient is a key requirement in designing and analyzing a hydraulic fracturing treatment.
2013hydraulic fracturing, pressure gradient
2014None
2015None
2016--
2017fiber lcm
20181.n. [Drilling Fluids]
2019A type of<a href="Display.cfm?Term=lost%20circulation%20material">lost <a href="Display.cfm?Term=circulation">circulation material(LCM) that is long, slender and flexible and occurs in various sizes and lengths of fiber. Fiber LCM is added tomudand placed downhole to help retard mud loss into fractures or highly permeablezones. Ideally, fiber LCM should be insoluble and inert to the mud system in which it is used. Examples are cedar bark, shredded cane stalks,mineralfiber and hair. Often, granular, flake and fiber LCMs are mixed together into an LCMpilland pumped into the well next to the zone offluid lossto seal the formationthat is taking mud from the system.
2020flake lost-circulation material, fluid loss, granular lost-circulation material, LCM, lost circulation, lost-circulation material
2021None
2022None
2023--
2024five spot
20251.n. [Enhanced Oil Recovery, Heavy Oil]
2026An injection pattern in which four input or injection wells are located at the corners of a square and the production well sits in the center. The injection fluid, which is normally water, steam or gas, is injected simultaneously through the four injection wells to displace the oil toward the central production well.
2027injection pattern, injection well, inverted five-spot
2028None
2029None
2030--
2031fluid loss control
20321.n. [Drilling Fluids]
2033The act or means of controlling (usually lowering) the volume of filtrate that passes through a filter medium. Control of fluid loss for a mud is achieved by several means, one of which is by addition of fluid-loss-control materials to the mud system. Another is to change the mud chemistry to make the materials already present work better. Adding a clay deflocculant to freshwater mud typically improves fluid-loss control.
2034None
2035None
2036fluid-loss control
2037--
2038frac head
20391.n. [Shale Gas, Well Completions, Well Workover and Intervention]
2040A flow cross installed on top of a frac tree where treating iron is connected and treatment fluid enters the frac tree.
2041None
2042None
2043buffalo head, goat head
2044--
2045fiber lost circulation material
20461.n. [Drilling Fluids]
2047A type of <a href="Display.cfm?Term=lost%20circulation%20material">lost <a href="Display.cfm?Term=circulation">circulation material that is long, slender and flexible and occurs in various sizes and lengths of fiber. Fiber LCM is added to mud and placed downhole to help retard mud loss into fractures or highly permeable zones. Ideally, fiber LCM should be insoluble and inert to the mud system in which it is used. Examples are cedar bark, shredded cane stalks, mineral fiber and hair. Often, granular, flake and fiber LCM are mixed together into an LCM pill and pumped into the well next to the zone of fluid loss to seal the formation that is taking mud from the system.
2048None
2049LCM
2050fiber LCM, fiber lost-circulation material
2051--
2052fixed cutter bit
20531.n. [Drilling]
2054A drilling tool that uses polycrystalline diamond compact (PDC) cutters to shear rock with a continuous scraping motion. These cutters are synthetic diamond disks about 1/8-in. thick and about 1/2 to 1 in. in diameter. PDC bits are effective at drilling shale formations, especially when used in combination with oil-base muds.
2055antiwhirl bit, bit
2056PDC bit, polycrystalline diamond compact bit
2057None
2058--
2059fluid loss control material
20601.n. [Drilling Fluids]
2061A group of mud additives specifically designed to lower the volume of filtrate that passes through a filter medium. Specific materials are available for all types of water- and oil-base mud systems and are evaluated in static filtration tests or in various dynamic filtration tests.
2062None
2063None
2064fluid-loss-control material
2065--
2066frac job
20671.n. [Well Completions, Shale Gas, Well Workover and Intervention]
2068Another term for hydraulic fracturing, a stimulation treatment routinely performed on oil and gas wells in low-permeability reservoirs. Specially engineered fluids are pumped at high pressure and rate into the reservoir interval to be treated, causing a vertical fracture to open. The wings of the fracture extend away from the wellbore in opposing directions according to the natural stresses within the formation. Proppant, such as grains of sand of a particular size, is mixed with the treatment fluid to keep the fracture open when the treatment is complete. Hydraulic fracturing creates high-conductivity communication with a large area of formation and bypasses any damage that may exist in the near-wellbore area.
2069treatment fluid
2070None
2071None
2072--
2073fiber lost circulation material
20741.n. [Drilling Fluids]
2075A type oflost circulation material(LCM) that is long, slender and flexible and occurs in various sizes and lengths of fiber. Fiber LCM is added tomudand placed downhole to help retard mud loss into fractures or highly permeablezones. Ideally, fiber LCM should be insoluble and inert to the mud system in which it is used. Examples are cedar bark, shredded cane stalks,mineralfiber and hair. Often, granular, flake and fiber LCMs are mixed together into an LCMpilland pumped into the well next to the zone offluid lossto seal the formationthat is taking mud from the system.
2076flake lost-circulation material, fluid loss, granular lost-circulation material, LCM, lost circulation, lost-circulation material
2077None
2078None
2079--
2080flange
20811.n. [Well Completions]
2082A connection profile used in pipe work and associated equipment to provide a means of assembling and disassembling components. Most oilfield flanges feature a bolt-hole pattern to allow the joint to be secured and a gasket profile to ensure a pressure-tight seal. The design and specification of a flange relates to the size and pressure capacity of the equipment to which it is fitted.
2083None
2084None
2085None
2086--
2087flange
20882.n. [Production]
2089A formed pipe fitting consisting of a projecting radial collar with bolt holes to provide a means of attachment to piping components having a similar fitting. The end piece of flanged-end valves.
2090fitting
2091None
2092None
2093--
2094fluid pound
20951.n. [Production Testing]
2096A phenomenon that occurs when the downhole pump rate exceeds the production rate of the formation. It can also be due to the accumulation of low-pressure gas between the valves. On the downstroke of the pump, the gas is compressed, but the pressure inside the barrel does not open the traveling valve until the traveling valve strikes the liquid. Finally when the traveling valve opens, the weight on the rod string can suddenly drop thousands of pounds in a fraction of a second. This condition should be avoided because it causes extreme stresses, which can result in premature equipment failure. Slowing down the pumping unit, shortening the stroke length or installing a smaller bottom hole pump can correct this problem.
2097rod string, stress, sucker rod pump, traveling valve
2098None
2099None
2100--
2101frac stack
21021.n. [Shale Gas, Well Completions, Well Workover and Intervention]
2103A Christmas tree installed specifically for the fracturing process. A frac stack typically consists of upper and lower master valves, flow cross, wing valves, goat head, and swab valve. Frac stacks generally have larger bores and higher pressure ratings than production trees to accommodate the high flow rates and pressures necessary for hydraulic fracturing.
2104None
2105None
2106frac tree
2107--
2108field
21091.n. [Geology]
2110An accumulation, pool, or group of pools of hydrocarbons or other mineral resources in the subsurface. A hydrocarbon field consists of a reservoir in a shape that will trap hydrocarbons and that is covered by an impermeable, sealing rock. Typically, the term implies an economic size.
2111accumulation, condensate, reservoir
2112None
2113oil field
2114--
2115field
21162.n. [Geology]
2117The surface area above a subsurface hydrocarbon accumulation.
2118accumulation
2119None
2120oil field
2121--
2122flapper valve
21231.n. [Drilling]
2124A check valve that has a spring-loaded plate (or flapper) that may be pumped through, generally in the downhole direction, but closes if the fluid attempts to flow back through the drillstring to the surface. This reverse flow might be encountered either due to a U-tube effect when the bulk density of the mud in the annulus is higher than that inside the drillpipe, or a well control event.
2125check valve, float collar, U-tube effect, well control
2126None
2127None
2128--
2129fluid tester
21301.n. [Production Testing]
2131A tool run on wireline to obtain fluid samples and measure formation pressures. This device is also called a wireline formation tester.
2132formation pressure
2133wireline formation tester
2134None
2135--
2136frac tree
21371.n. [Shale Gas, Well Completions, Well Workover and Intervention]
2138A Christmas tree installed specifically for the fracturing process. A frac tree typically consists of upper and lower master valves, flow cross, wing valves, goat head, and swab valve. Frac trees generally have larger bores and higher pressure ratings than production trees to accommodate the high flow rates and pressures necessary for hydraulic fracturing.
2139composite frac tree
2140None
2141frac stack
2142--
2143field weld
21441.n. [Well Workover and Intervention]
2145A welding technique used to join two tubes in which the squared and prepared ends are butted together in preparation for welding. The resulting circumferential weld has relatively good strength characteristics but has limitations where the tube is to be plastically deformed or bent, such as occurs on a coiled tubing string. Consequently, butt welds performed on a coiled tubing string should be checked carefully using hardness and radiographic testing methods and their locations detailed in the string record. The anticipated fatigue life in the butt-weld area must also be reduced to compensate for the weakness of the weld.
2146bias weld
2147None
2148None
2149--
2150flare
21511.n. [Production Facilities]
2152The burning of unwanted gas through a pipe (also called a flare). Flaring is a means of disposal used when there is no way to transport the gas to market and the operator cannot use the gas for another purpose. Flaring generally is not allowed because of the high value of gas and environmental concerns.
2153flare gas
2154None
2155None
2156--
2157flare
21582.n. [Production Facilities]
2159An arrangement consisting of a vertical tower and burners used to burn combustible vapors. A flare is usually situated near a producing well or at a gas plant or refinery. A flare is also called a flare stack.
2160flare gas, gas processing plant, producing well
2161None
2162None
2163--
2164fluid density log
21651.n. [Production Logging]
2166A record of the density, or changes in density, of fluids in a production or injection well. Since gas, oil and water all have different densities, the log can determine the percentage, or holdup, of the different fluids, directly in the case of biphasic flow, and in combination with other measurements for triphasic flow. Fluid density is measured by a gradiomanometer or a nuclear fluid densimeter, and can also be derived from the depth derivative of a pressure sensor.
2167holdup log, injection well, nuclear fluid densimeter, production log
2168None
2169None
2170--
2171frac valve
21721.n. [Well Workover and Intervention]
2173A high-pressure isolation valve fitted to the top of the wellhead on a well that is about to be hydraulically fractured. The frac valve can be closed to isolate the treating equipment from the wellbore.
2174hydraulic fracturing
2175None
2176None
2177--
2178fill cement
21791.n. [Drilling Fluids]
2180A cement system used to provide zonal isolation across generally nonproductive zones located above the zones of interest. The fill cement is also called the lead cement.
2181None
2182None
2183lead cement
2184--
2185float collar
21861.n. [Well Completions]
2187A component installed near the bottom of the casing string on which cement plugs land during the primary cementing operation. It typically consists of a short length of casing fitted with a check valve. This device may be a flapper-valve type, a spring-loaded ball valve or other type.The check-valve assembly fixed within the float collar prevents flowback of the cement slurry when pumping is stopped. Without a float collar, the cement slurry placed in the annulus could U-tube, or reverse flow back into the casing. The greater density of cement slurries than the displacement mud inside the casing causes the U-tube effect.
2188casing string, cement plug, check valve, displacement fluid, flapper valve, float joint, flow back, primary cementing, U-tube effect
2189None
2190None
2191--
2192fluid friction reducer
21931.n. [Well Workover and Intervention]
2194A chemical additive that alters fluid rheological properties to reduce friction created within the fluid as it flows through small-diameter tubulars or similar restrictions. Generally polymers, or similar friction reducing agents, add viscosity to the fluid, which reduces the turbulence induced as the fluid flows. Reductions in fluid friction of 50 to 60% are possible.
2195polymer
2196None
2197None
2198--
2199fracture
22001.n. [Shale Gas, Geology]
2201A crack or surface of breakage within rock not related to foliation or cleavage in metamorphic rock along which there has been no movement. A fracture along which there has been displacement is a fault. When walls of a fracture have moved only normal to each other, the fracture is called a joint. Fractures can enhance permeability of rocks greatly by connecting pores together, and for that reason, fractures are induced mechanically in some reservoirs in order to boost hydrocarbon flow.Fractures may also be referred to as natural fractures to distinguish them from fractures induced as part of a reservoir stimulation or drilling operation. In some shale reservoirs, natural fractures improve production by enhancing effective permeability. In other cases, natural fractures can complicate reservoir stimulation.
2202competent, dilatancy, en echelon, fracture gradient, halite, incompetent, permeability, pore, S-wave, strain, structure
2203None
2204None
2205--
2206fracture
22072.vb. [Shale Gas, Well Completions]
2208To perform astimulationtreatment, which is routine for oil and gas wells in low-permeabilityreservoirs. Specially engineered fluids are pumped at highpressureand rate into thereservoirinterval to be treated, causing a verticalfractureto open. The wings of the fracture extend away from the wellbore in opposing directions according to the natural stresses within theformation.Proppant, such as grains ofsandof a particular size, is mixed with the treatment fluid to keep the fracture open when the treatment is complete. Hydraulic fracturing creates high-conductivitycommunication with a large area of formation and bypasses any damagethat may exist in the near-wellbore area.
2209hydraulic fracturing, treatment fluid
2210None
2211None
2212--
2213fill sub
22141.n. [Perforating]
2215A pipe-shaped housing that protects the firing head of a tubing-conveyed perforating gun. It is used to accommodate or deflect debris that might fall toward the firing head while running into the hole or while on depth before shooting.
2216firing head, perforating gun, tubing-conveyed perforating
2217None
2218None
2219--
2220float joint
22211.n. [Drilling]
2222A full-sized length of casing placed at the bottom of the casing string that is usually left full of cement on the inside to ensure that good cement remains on the outside of the bottom of the casing. If cement were not left inside the casing in this manner, the risk of overdisplacing the cement (due to improper casing volume calculations, displacement mud volume measurements, or both) would be significantly higher. Hence, the well designer plans on a safety margin of cement left inside the casing to guarantee that the fluid left outside the casing is good-quality cement. A float collar is placed at the top of the float joint and a float shoe placed at the bottom to prevent reverse flow of cement back into the casing after placement. There can be one, two or three joints of casing used for this purpose.
2223casing string, displacement fluid, float collar, float shoe
2224shoe joint
2225None
2226--
2227fluid interface log
22281.n. [Production Logging]
2229An in-situ measurement of the flow profile made by pumping different fluids down the tubing and casing and observing the interface between them. The fluids are normally both water, but one may be fresh and the other salty, or else one may contain some tracer, so that the interface can be detected by a production-logging tool. After the tubing is run to the bottom of the well, an interface is introduced by one of two methods. In the static method, the total flow rate is held constant and the relative flow rate of the two streams is changed. The location of the interface after each change is used to determine the flow profile. In the dynamic method, one fluid is pumped at different rates. The log was used in the 1950s and 1960s but is now used rarely, having been replaced by fluid-density logs and others.
2230flow profile, flowing neutron log, fluid-density log, fresh water, production log
2231None
2232None
2233--
2234fracture acidizing
22351.n. [Enhanced Oil Recovery]
2236A well-stimulation operation in which acid, usually hydrochloric [HCl], is injected into a carbonate formation at a pressure above the formation-fracturing pressure. Flowing acid tends to etch the fracture faces in a nonuniform pattern, forming conductive channels that remain open without a propping agent after the fracture closes.The length of the etched fracture limits the effectiveness of an acid-fracture treatment. The fracture length depends on acid leakoff and acid spending. If acid fluid-loss characteristics are poor, excessive leakoff will terminate fracture extension. Similarly, if the acid spends too rapidly, the etched portion of the fracture will be too short. The major problem in fracture acidizing is the development of wormholes in the fracture face; these wormholes increase the reactive surface area and cause excessive leakoff and rapid spending of the acid. To some extent, this problem can be overcome by using inert fluid-loss additives to bridge wormholes or by using viscosified acids. Fracture acidizing is also called acid fracturing or acid-fracture treatment.
2237acid frac, fluid loss, formation fracture pressure, hydraulic fracturing, matrix stimulation
2238None
2239None
2240--
2241filter cake
22421.n. [Drilling Fluids]
2243The residue deposited on a permeable medium when a slurry, such as a drilling fluid, is forced against the medium under a pressure. Filtrate is the liquid that passes through the medium, leaving the cake on the medium. Drilling muds are tested to determine filtration rate and filter-cake properties. Cake properties such as cake thickness, toughness, slickness and permeability are important because the cake that forms on permeable zones in the wellbore can cause stuck pipe and other drilling problems. Reduced oil and gas production can result from reservoir damage when a poor filter cake allows deep filtrate invasion. A certain degree of cake buildup is desirable to isolate formations from drilling fluids. In openhole completions in high-angle or horizontal holes, the formation of an external filter cake is preferable to a cake that forms partly inside the formation. The latter has a higher potential for formation damage.
2244deflocculated mud, drilling fluid, dynamic filtration, filter-cake quality, filter-cake thickness, filtrate volume, openhole completion, relative filtrate volume, resin, static filtration
2245cake, mudcake, wall cake
2246filtercake
2247--
2248float shoe
22491.n. [Well Completions]
2250A rounded profile component attached to the downhole end of a casing string. An integral check valve in the float shoe prevents reverse flow, or U-tubing, of cement slurry from the annulus into the casing or flow of wellbore fluids into the casing string as it is run. The float shoe also guides the casing toward the center of the hole to minimize hitting rock ledges or washouts as the casing is run into the wellbore. The float shoe reduces hook weight. With controlled or partial fill-up as the string is run, the casing string can be floated into position, avoiding the need for the rig to carry the entire weight of the casing string. The outer portions of the float shoe are made of steel and generally match the casing size and threads, although not necessarily the casing grade. The inside (including the taper) is usually made of cement or thermoplastic, since this material must be drilled out if the well is to be deepened beyond the casing point.
2251casing, casing shoe, check valve, float joint, guide shoe, washout
2252None
2253None
2254--
2255fluid loss additive
22561.n. [Drilling Fluids]
2257A group of mud additives specifically designed to lower the volume of filtrate that passes through a filter medium. Specific materials are available for all types of water- and oil-base mud systems and are evaluated in static filtration tests or in various dynamic filtration tests.
2258dynamic filter press, dynamic filtration, filter medium, filtrate volume, fluid-loss control, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, oil-base mud, static filtration, water-base drilling fluid
2259None
2260None
2261--
2262fluid loss additive
22632.n. [Well Completions]
2264A chemical additive used to control the loss of fluid to the formation through filtration. In cementing operations, loss of the aqueous phase can severely affect the performance of the slurry and set cement. In almost any operation, loss of fluid to the reservoir formation carries a high risk of permeability damage.
2265None
2266None
2267None
2268--
2269fracture porosity
22701.n. [Geology]
2271A type of secondary porosity produced by the tectonic fracturing of rock. Fractures themselves typically do not have much volume, but by joining preexisting pores, they enhance permeability significantly. In exceedingly rare cases, nonreservoir rocks such as granite can become reservoir rocks if sufficient fracturing occurs.
2272fracture, plate tectonics, pore, secondary porosity
2273None
2274None
2275--
2276filter cake quality
22771.n. [Drilling Fluids]
2278A subjective description of a filter cake, especially its toughness, slickness and hardness. A mud engineer makes these observations, which are recorded on the mud report along with filtrate volume and cake thickness. With increasing experience, the engineer's observations can become less subjective.
2279None
2280None
2281filtercake quality, filter-cake quality
2282--
2283floc
22841.n. [Drilling Fluids]
2285A coagulated mass of particles in a liquid. Flocs can occur naturally but often are generated from a dispersed colloidal system to which a flocculant chemical has been added. Clay particles and polymers in water can be flocculated to form flocs.
2286clay-water interaction, flocculation, polymer
2287None
2288None
2289--
2290fluid loss control
22911.n. [Drilling Fluids]
2292The act or means of controlling (usually lowering) the volume of filtrate that passes through a filter medium. Control of fluid loss for a mud is achieved by several means, one of which is by addition of fluid-loss-control materials to the mud system. Another is to change the mud chemistry to make the materials already present work better. Adding a clay deflocculant to freshwater mud typically improves fluid-loss control.
2293carboxymethyl starch, carboxymethylcellulose, filter medium, filtrate volume, fluid-loss-control material, gilsonite, gyp mud, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, plugging material, saltwater mud, spurt loss, static filtration
2294None
2295None
2296--
2297fractured well analysis
22981.n. [Well Testing]
2299Analysis of a well that passes through a natural fracture or that has been hydraulically fractured. The fracture is treated as a slab of high permeability that is an effective extension of the actual wellbore. Flow is from the reservoir to the fracture and through the fracture to the well. The pressure-transient analysis for a fractured well can determine the fracture half-length and the fracture conductivity, as well as a fracture-face skin. The skin factor for the fracture is negative and usually ranges from -1.5 to -5, with an absolute minimum of -6 in rare cases. For effectively infinite-conductivity fractures, the apparent wellbore radius is half the fracture half-length, or xf/2.
2300fracture conductivity, fracture half-length, hydraulic fracturing, infinite-conductivity fracture, pressure-transient analysis, skin effect
2301None
2302None
2303--
2304filter cake thickness
23051.n. [Drilling Fluids]
2306A measurement of the thickness of the filter cake, usually recorded in 32nds-inch. Under dynamic conditions, filter-cake thickness depends on rate of deposition versus erosion caused by fluid circulation and mechanical abrasion by the rotating drillstring. Typically, the filter cake will reach an equilibrium thickness in the wellbore. In laboratory tests, however, filter cake is built under static conditions with no erosion.
2307differential sticking, dynamic filter press, dynamic filtration, filter cake, filter medium, filter press, filter-cake quality, filtrate volume, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, static filtration
2308None
2309filtercake thickness, filter-cake thickness
2310--
2311flocculate
23121.vb. [Drilling Fluids]
2313The term used to describe what clays, polymers or other small charged particles do when they become attached and form a fragile structure, afloc. Indispersed clayslurries, flocculation occurs after mechanical agitation ceases and the dispersedclayplatelets spontaneously form flocs because of attractions between negative face charges and positive edge charges.
2314aggregation, flocculation, wastewater cleanup
2315None
2316Antonyms:deflocculate
2317--
2318flocculate
23192.vb. [Heavy Oil]
2320The term used to describe what small particles do when they aggregate into larger particles. In the context of heavy oil,asphaltenesare known to flocculateat the molecular level (beforeprecipitation) and in the precipitated state. The extent of asphaltene flocculation changes with fluid composition, temperature andpressure. For precipitated asphaltenes, flocculation is also affected by the shear environment.
2321aggregate, heavy oil
2322None
2323None
2324--
2325fluid loss control material
23261.n. [Drilling Fluids]
2327A group of mud additives specifically designed to lower the volume of filtrate that passes through a filter medium. Specific materials are available for all types of water- and oil-base mud systems and are evaluated in static filtration tests or in various dynamic filtration tests.
2328dynamic filter press, dynamic filtration, filter medium, filtrate volume, fluid-loss control, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, oil-base mud, static filtration, water-base drilling fluid
2329None
2330None
2331--
2332fractured well analysis
23331.n. [Well Testing]
2334Analysis of a well that passes through a natural fracture or that has been hydraulically fractured. The fracture is treated as a slab of high permeability that is an effective extension of the actual wellbore. Flow is from the reservoir to the fracture and through the fracture to the well. The pressure-transient analysis for a fractured well can determine the fracture half-length and the fracture conductivity, as well as a fracture-face skin. The skin factor for the fracture is negative and usually ranges from -1.5 to -5, with an absolute minimum of -6 in rare cases. For effectively infinite-conductivity fractures, the apparent wellbore radius is half the fracture half-length, or xf/2.
2335fracture conductivity, fracture half-length, hydraulic fracturing, infinite-conductivity fracture, pressure-transient analysis, skin effect
2336None
2337None
2338--
2339filter cell
23401.n. [Drilling Fluids]
2341A pressurized cell, fitted with a filter medium, used for evaluating filtration characteristics of a drilling fluid while it is either static or stirred (to simulate circulation) in the test cell. Generally, either low-pressure, low-temperature or high-pressure, high-temperature devices are used.
2342drilling fluid, dynamic filter press, dynamic filtration, filter medium, filter press, filter-cake quality, filter-cake thickness, filtrate, fluid-loss control, fluid-loss-control material, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, spurt loss, static filtration
2343None
2344None
2345--
2346flocculation
23471.n. [Drilling Fluids]
2348A condition in which clays, polymers or other small charged particles become attached and form a fragile structure, a floc. In dispersed clay slurries, flocculation occurs after mechanical agitation ceases and the dispersed clay platelets spontaneously form flocs because of attractions between negative face charges and positive edge charges.
2349aggregation, clay-water interaction, deflocculant, flocculant, polymer, saltwater flow, spud mud, wastewater cleanup
2350flocculate
2351Antonyms:deflocculation
2352--
2353flocculation
23542.n. [Heavy Oil]
2355The aggregation of small particles into larger particles. In the context of heavy oil, asphaltenes are known to flocculate at the molecular level (before precipitation) and in the precipitated state. The extent of asphaltene flocculation changes with fluid composition, temperature and pressure. For precipitated asphaltenes, flocculation is also affected by the shear environment.
2356heavy oil
2357None
2358None
2359--
2360fluoboric acid
23611.n. [Enhanced Oil Recovery]
2362An acid mixture that generates more hydrofluoric [HF] acid as the HF is consumed. In the field, fluoboric acid [HBF4] is easily prepared by mixing boric acid [H3BO3], ammonium bifluoride [NH3F.HF] and hydrochloric acid. Fluoboric acid was developed to counteract the shortcomings associated with mud-acid treatments. It is a retarded fluid that can penetrate deep into the reservoir before spending, especially at high temperatures, and does not contain high HF at any given time. Thus, it is less reactive than mud acid, but its total dissolving power is comparable:HBF4 + H3O --&gt; HBF3OH + HF.The limited amount of HF at any given time decreases the probability of forming precipitates of fluosilicates, fluoaluminates or silica. Fluoboric acid provides permanent stabilization of clays and fines through reactions related to borate and fluoborate ions. For example, borosilicates coat and bind undissolved clays and fines, preventing further mobility of these particles that might plug the formation and impair production. Mud acid does not provide this coating feature. Fluoboric acid also eliminates water sensitivity and is especially recommended in formations containing potassium minerals.Fluoboric acid can be used as a preflush, an overflush or as a main stage in a sandstone matrix acidizing. As a main fluid, a fluoboric acid treatment requires a preflush (weak HCl acid or brine) and should not be overflushed to obtain the maximum stabilization effect in the critical matrix area. Fluoboric acid treatments are the only acid formulations that require long shut-in times because of their long reaction times.
2363hydrofluoric acid, matrix acidizing, mud acid, organic acid, retarder
2364None
2365None
2366--
2367fracturing fluid
23681.n. [Well Completions, Shale Gas]
2369A fluid injected into a well as part of a stimulation operation. Fracturing fluids for shale reservoirs usually contain water, proppant, and a small amount of nonaqueous fluids designed to reduce friction pressure while pumping the fluid into the wellbore. These fluids typically include gels, friction reducers, crosslinkers, breakers and surfactants similar to household cosmetics and cleaning products; these additives are selected for their capability to improve the results of the stimulation operation and the productivity of the well.
2370None
2371None
2372frac fluid
2373--
2374filter medium
23751.n. [Drilling Fluids]
2376A permeable material used in a filtration device through which filtrate passes and on which the filter cake is deposited, commonly a specifically designed filter paper or permeable disk used in a static filter press that meets API standards. The filter medium can be the cylindrical, permeable core or disk used in a dynamic filtration test or permeable rock downhole on which a filter cake is deposited in a wellbore.
2377capillary-suction-time test, dynamic filter press, filter press, fluid-loss control, fluid-loss-control material, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, particle-plugging apparatus, relative filtrate volume, static filtration, wastewater cleanup, water clarification
2378filter media
2379None
2380--
2381flooding pattern
23821.n. [Enhanced Oil Recovery]
2383Also known as injection pattern, the particular arrangement of production and injection wells. The injection pattern for an individual field or part of a field is based on the location of existing wells, reservoir size and shape, cost of new wells and the recovery increase associated with various injection patterns. The flood pattern can be altered during the life of a field to change the direction of flow in a reservoir with the intent of contacting unswept oil. It is common to reduce the pattern size by infill drilling, which improves oil recovery by increasing reservoir continuity between injectors and producers. Common injection patterns are direct line drive, staggered line drive, two-spot, three-spot, four-spot, five-spot, seven-spot and nine-spot. Normally, the two-spot and three-spot patterns are used for pilot testing purposes. The patterns are called normal or regular when they include only one production well per pattern. Patterns are described as inverted when they include only one injection well per pattern.
2384enhanced oil recovery, injection well, off-pattern well, waterflooding
2385None
2386None
2387--
2388flush joint
23891.n. [Well Completions]
2390A type of tubing connection in which the internal or external surfaces are the same diameter throughout the tubing joint. Internal flush joints are most common, offering no restriction to fluid flow. Externally flush joints are typically used in more specialized applications, such as washover pipe for fishing operations, to allow adequate outer diameter (OD) clearance.
2391outside diameter, tubing joint, washover pipe
2392None
2393None
2394--
2395fracturing mandrel
23961.n. [Well Completions, Well Workover and Intervention]
2397A sleeve with a flanged top connection upon which a frac tree is installed. The sleeve is inserted into a wellhead to isolate its low-pressure connections from the higher fracturing pressures. The fracturing mandrel enables the use of low-pressure wellheads that could not normally withstand the higher pressures necessary for hydraulic fracturing.
2398fracturing sleeve, mandrel
2399None
2400None
2401--
2402filter press
24031.n. [Drilling Fluids]
2404A pressurized cell, fitted with a filter medium, used for evaluating filtration characteristics of a drilling fluid while it is either static or stirred (to simulate circulation) in the test cell. Generally, either low-pressure, low-temperature or high-pressure, high-temperature devices are used.
2405drilling fluid, dynamic filter press, dynamic filtration, filter medium, filter-cake quality, filter-cake thickness, filtrate, fluid-loss control, fluid-loss-control material, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, spurt loss, static filter press, static filtration
2406None
2407None
2408--
2409flooding surface
24101.n. [Reservoir Characterization]
2411A surface exhibiting evidence of an abrupt increase in water depth, separating younger from older strata. The surface may also display evidence of minor submarine erosion. It forms in response to an increase in water depth and typically bounds parasequences. In sequence stratigraphic terminology, it replaces the older, more generic term "trangressive surface," although it is not a strict equivalent.
2412maximum flooding surface, parasequence, sequence stratigraphy, transgressive surface
2413None
2414None
2415--
2416flushed zone
24171.n. [Formation Evaluation]
2418The volume close to the borehole wall in which all of the moveable fluids have been displaced by mud filtrate. The flushed zone contains filtrate and the remaining hydrocarbons, the percentage of the former being the flushed-zone water saturation, Sxo. In simple models, the flushed zone and the invaded zone are synonymous.
2419diameter of invasion, flushed-zone water saturation, formation water, hydrocarbon, invasion, water saturation
2420invaded zone
2421None
2422--
2423fracturing pressure
24241.n. [Well Testing, Well Workover and Intervention, Shale Gas]
2425Pressure above which injection of fluids will cause the rock formation to fracture hydraulically.
2426fracture gradient, hydraulic fracturing
2427None
2428None
2429--
2430filtercake
24311.n. [Drilling Fluids]
2432The residue deposited on a permeable medium when a slurry, such as a drilling fluid, is forced against the medium under a pressure. Filtrate is the liquid that passes through the medium, leaving the cake on the medium. Drilling muds are tested to determine filtration rate and filtercake properties. Cake properties such as cake thickness, toughness, slickness and permeability are important because the cake that forms on permeable zones in the wellbore can cause stuck pipe and other drilling problems. Reduced oil and gas production can result from reservoir damage when a poor filtercake allows deep filtrate invasion. A certain degree of cake buildup is desirable to isolate formations from drilling fluids. In openhole completions in high-angle or horizontal holes, the formation of an external filtercake is preferable to a cake that forms partly inside the formation. The latter has a higher potential for formation damage.
2433deflocculated mud, drilling fluid, dynamic filtration, filter-cake quality, filter-cake thickness, filtrate volume, openhole completion, relative filtrate volume, resin, static filtration
2434cake, mudcake, wall cake
2435filter cake
2436--
2437flow after flow
24381.n. [Production Testing]
2439A type of deliverability test conducted in gas wells to generate a stabilized gas deliverability curve (IPR). In a flow-after-flow test, a well flows under a constant rate until it reaches stabilized conditions (pseudosteady state). After the stabilized rate and pressure are recorded, the rate is changed and the well flows until pressure stabilizes again. The same procedure is repeated three or four times. The stabilization requirement is an important limitation of this type of test, especially in low-permeability formations, which require longer stabilization times. This test is also known as a backpressure or four-point test.
2440deliverability test, flow-after-flow tests, gas well, inflow performance relationship, IPR, pseudosteady state
2441None
2442None
2443--
2444flushed zone water saturation
24451.n. [Formation Evaluation]
2446The fraction of water in a given pore space in the flushed zone. It is expressed in volume/volume, percent or saturation units and is given the symbol Sxo. Unless otherwise stated, the pore space concerned is usually the effective porosity. If the pore space concerned is the total porosity, the saturation is more correctly known as the total flushed-zone water saturation; or if it is the effective porosity, the effective flushed-zone water saturation.
2447effective porosity, flushed zone, moveable hydrocarbons, residual oil, total porosity, water saturation
2448None
2449None
2450--
2451fracturing sleeve
24521.n. [Well Completions, Well Workover and Intervention]
2453Similar to a fracturing mandrel, a fracturing sleeve is temporarily inserted into a wellhead before the fracturing process begins to isolate low-pressure connections from the higher fracturing pressures. Fracturing sleeves differ from fracturing mandrels in that the fracturing sleeve is fully contained within the wellhead, and the frac tree is installed on the wellhead, not the sleeve.
2454mandrel
2455None
2456None
2457--
2458filtercake quality
24591.n. [Drilling Fluids]
2460A subjective description of a filtercake, especially its toughness, slickness and hardness. A mud engineer makes these observations, which are recorded on the mud report along with filtrate volume and filtercake thickness. With increasing experience, the engineer's observations can become less subjective.
2461acrylamido-methyl-propane sulfonate polymer, differential sticking, dynamic filter press, dynamic filtration, filter cake, filter press, filter-cake thickness, low-pressure, low-temperature filtration test, mud engineer, static filtration
2462None
2463filter cake quality, filter-cake quality
2464--
2465flow assurance
24661.n. [Well Workover and Intervention]
2467The design, strategies and principles for ensuring that there is uninterrupted hydrocarbon production flowing from the reservoir to the point of sale. Impediments to hydrocarbon flow in wellbores and flowlines may arise from an interrelated combination of effects involving flow dynamics—single and multiphase fluid flow—and production chemistry. At reservoir pressure and temperature conditions, fluids are single phase. As they travel toward the production facility, the fluids experience changes in pressure and temperature that result in multiple fluid phases and the formation, accumulation and dispersal of inorganic and organic solids that may become impediments to production. Multiphase flow may cause phenomena such as slugging in subsea flowlines and risers. Solids deposition may cause flowline plugging anywhere in the system.Historically, production impediments in wellbores and flowlines are well-known in onshore and shallow water environments, where they have been managed using thermal, mechanical and chemical means. The long flowlines connecting a wellhead or manifold to a production facility are exposed to low temperatures and high pressures. In these deepwater environments, intervention technologies and operations are expensive because they typically require deepwater vessels or a rig. Personnel responsible for flow assurance should have advanced knowledge of flow dynamics and production chemistry.
2468None
2469None
2470None
2471--
2472flushed zone water saturation
24731.n. [Formation Evaluation]
2474The fraction of water in a given pore space in the flushed zone. It is expressed in volume/volume, percent or saturation units and is given the symbol Sxo. Unless otherwise stated, the pore space concerned is usually the effective porosity. If the pore space concerned is the total porosity, the saturation is more correctly known as the total flushed-zone water saturation; or if it is the effective porosity, the effective flushed-zone water saturation.
2475effective porosity, flushed zone, moveable hydrocarbons, moved hydrocarbons, residual oil, total porosity, water saturation
2476None
2477None
2478--
2479free fluid
24801.n. [Formation Evaluation]
2481Fluid in the pore space that can flow under normal reservoir conditions. This fluid may include water, oil or gas, and will flow on production, injection or invasion. When the term is used in connection with nuclear magnetic resonance measurements, it refers to the signal that occurs above a certain cutoff, typically 33 ms in sandstones and 100 ms in carbonates. The source of this signal is free water and oil with a viscosity below about 60 cp in sandstones, and 30 cp in carbonates. Note that, contrary to the sense of "free," this oil may or may not be residual under normal reservoir conditions.
2482bound fluid, clay-bound water, effective porosity, magnetic resonance, total porosity
2483None
2484free water
2485--
2486free fluid
24872.n. [Drilling Fluids]
2488The volume of fluid (expressed in percent) that separates from a cement slurry when the slurry is left static. The free fluid can be measured as specified in API Recommended Practice 10B. Free fluid is also known as free water.
2489None
2490None
2491free water
2492--
2493filter cake quality
24941.n. [Drilling Fluids]
2495A subjective description of a filter cake, especially its toughness, slickness and hardness. A mud engineer makes these observations, which are recorded on the mud report along with filtrate volume and cake thickness. With increasing experience, the engineer's observations can become less subjective.
2496acrylamido-methyl-propane sulfonate polymer, differential sticking, dynamic filter press, dynamic filtration, filter cake, filter press, filter-cake thickness, low-pressure, low-temperature filtration test, mud engineer, static filtration
2497None
2498filter cake quality, filtercake quality
2499--
2500flow back
25011.n. [Well Workover and Intervention]
2502The process of allowing fluids to flow from the well following a treatment, either in preparation for a subsequent phase of treatment or in preparation for cleanup and returning the well to production.
2503None
2504None
2505None
2506--
2507fluvial
25081.adj. [Geology]
2509Pertaining to an environment of deposition by a river or running water. Fluvial deposits tend to be well sorted, especially in comparison with alluvial deposits, because of the relatively steady transport provided by rivers.
2510alluvial, depositional environment, depositional system
2511None
2512None
2513--
2514free water
25151.n. [Geology]
2516Water that is mobile, available to flow, and not bound to surfaces of grains or minerals in rock.
2517None
2518None
2519None
2520--
2521free water
25222.n. [Drilling]
2523In cementing, any water in the slurry that is in excess of what is required to fully hydrate the Portland cement and other additives. Free water can physically separate as a cement slurry sets. This separation tendency, especially in the presence of a high-pressure gas-bearing formation, can impair zonal isolation, the primary job of the cement. For that reason, the well designer usually specifies a maximum free-water content for the slurry.
2524cementing, portland cement
2525None
2526None
2527--
2528free water
25293.n. [Well Completions]
2530The aqueous phase that separates from a slurry or mixture of fluids. In cementing operations, free water is undesirable since channels tend to form through the set cement, providing potential gas migration paths. When processing reservoir fluids, the water that separates easily under gravity separation is known as free water. In some cases, additional water may be locked in an emulsion, contributing to the aqueous phase but not available as free water.
2531gas migration
2532None
2533None
2534--
2535free water
25364.n. [Formation Evaluation]
2537Water in the pore space that can flow under normal reservoir conditions. When used in connection with nuclear magnetic resonance (NMR) measurements, free water is all the water that is not clay bound, capillary bound or in mineral hydrates. The latter is in any case excluded as it relaxes too fast to be measured by NMR. When used in connection with the dual-water model, the term means the far water.
2538bound water, clay-bound water, dual water, effective porosity, free fluid, magnetic resonance, total porosity
2539None
2540far water
2541--
2542filtercake thickness
25431.n. [Drilling Fluids]
2544A measurement of the thickness of the filtercake, usually recorded in 32nds-inch. Under dynamic conditions, filtercake thickness depends on rate of deposition versus erosion caused by fluid circulation and mechanical abrasion by the rotating drillstring. Typically, the filtercake will reach an equilibrium thickness in the wellbore. In laboratory tests, however, filtercake is built under static conditions with no erosion.
2545differential sticking, dynamic filter press, dynamic filtration, filter cake, filter medium, filter press, filter-cake quality, filtrate volume, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, static filtration
2546None
2547filter cake thickness, filter-cake thickness
2548--
2549flow coefficient Cv
25501.n. [Production]
2551The number of gallons of water per minute that will flow through a valve with a pressure drop of 1 psi, abbreviated Cv. Kv is the cubic meters of water per hour that cause a pressure drop of 1 bar.
2552capacity factor (of a valve), Cv, Kv
2553None
2554None
2555--
2556flux leakage
25571.n. [Production Logging]
2558A distortion of the magnetic flux that has been introduced into a casing by a low-frequency electromagnet or permanent magnet. The principle of flux leakage is used to detect casing corrosion, since flux leakage is caused by rapid changes in the thickness of the casing and by pits and holes in either the internal or external wall. Flux leakage distorts the magnetic-flux lines and induces a signal into an electric coil moving past it. In-situ flux-leakage measurements make use of this effect by placing coils on or close to the casing wall, azimuthally distributed to cover the entire wall. The results are often combined with a high-frequency, eddy-current measurement, designed to detect flaws only on the inner wall.
2559azimuthal, casing-inspection log, casing-potential profile, eddy current, eddy-current measurement, pitting
2560None
2561None
2562--
2563free water knockout
25641.n. [Production Facilities]
2565A vertical or horizontal separator used mainly to remove any free water that can cause problems such as corrosion and formation of hydrates or tight emulsions, which are difficult to break.A free-water knockout is commonly called a three-phase separator because it can separate gas, oil and free water. The liquids that are discharged from the free-water knockout are further treated in vessels called treaters. Free-water knockout is abbreviated as FWKO.
2566free water, treater, vertical separator
2567None
2568None
2569--
2570filter cake thickness
25711.n. [Drilling Fluids]
2572A measurement of the thickness of the filter cake, usually recorded in 32nds-inch. Under dynamic conditions, filter-cake thickness depends on rate of deposition versus erosion caused by fluid circulation and mechanical abrasion by the rotating drillstring. Typically, the filter cake will reach an equilibrium thickness in the wellbore. In laboratory tests, however, filter cake is built under static conditions with no erosion.
2573differential sticking, dynamic filter press, dynamic filtration, filter cake, filter medium, filter press, filter-cake quality, filtrate volume, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, static filtration
2574None
2575filter cake thickness, filtercake thickness
2576--
2577flow concentrating
25781.adj. [Production Logging]
2579Referring to a type of spinner flowmeter in which most or all of the fluid flow in the well is diverted over the spinner by a device such as a basket or a packer.
2580basket flowmeter, deflector flowmeter, diverter flowmeter, flowmeter, fluid flow, packer flowmeter, petal basket flowmeter, production log, spinner flowmeter, torque flowmeter
2581None
2582None
2583--
2584foamed cement
25851.n. [Drilling Fluids]
2586A homogeneous, ultralightweight cement system consisting of base cement slurry, gas (usually nitrogen) and surfactants. Foamed cements are commonly used to cement wells that penetrate weak rocks or formations with low formation-fracture gradients.
2587fracture gradient, surfactant
2588None
2589None
2590--
2591free water knockout
25921.n. [Production Facilities]
2593A vertical or horizontal separator used mainly to remove any free water that can cause problems such as corrosion and formation of hydrates or tight emulsions, which are difficult to break.A free-water knockout is commonly called a three-phase separator because it can separate gas, oil and free water. The liquids that are discharged from the free-water knockout are further treated in vessels called treaters. Free-water knockout is abbreviated as FWKO.
2594free water, treater, vertical separator
2595None
2596Antonyms:three phase separator
2597--
2598filtered brine
25991.n. [Well Completions]
2600A completion or workover fluid that has been treated to remove debris and fine particles that may cause near-wellbore damage if allowed to enter the reservoir formation.
2601completion fluid, workover fluid
2602None
2603None
2604--
2605flow coupling
26061.n. [Well Completions]
2607A relatively short, heavy-walled completion component installed in areas where turbulence is anticipated. The additional wall thickness prevents early failures due to erosion in the turbulent flow area. Flow couplings are typically installed above and below completion components, such as landing nipples, that may affect the flow.
2608nipple
2609None
2610None
2611--
2612foaming agent
26131.n. [Drilling Fluids, Enhanced Oil Recovery]
2614An additive used in preparation of foam used as a drilling fluid. Drilling foam is water containing air or gas bubbles, much like shaving foam, and it must withstand high salinity, hard water, solids, entrained oil and high temperature. Foaming agents are usually nonionic surfactants and contain polymeric materials.
2615drilling fluid, HLB number, polymer, surfactant
2616None
2617Antonyms:defoamer
2618--
2619fresh water
26201.n. [Formation Evaluation]
2621Formation water with low salinity. Water is considered fresh when its low conductivity makes the interpretation of resistivity logs difficult. The salinity at which this becomes important depends on temperature and clay content, among other factors, but is generally somewhere less than 10 ppk.
2622formation water, resistivity log
2623None
2624None
2625--
2626fresh water
26272.n. [Geology]
2628Water that is low in dissolved salt (&lt; 2000 ppm).
2629brine, connate water, hydrostatic head, hydrostatic pressure, interstitial water
2630None
2631None
2632--
2633filtrate tracer
26341.n. [Drilling Fluids]
2635A chemical or isotopic marker that is uniformly distributed in the continuous phase of a drilling, coring, drill-in or completion fluid and used to later identify the filtrate in cores or in fluids sampled from permeable strata. A tracer must become a part of the filtrate, remaining in true solution and moving with the filtrate into permeable zones. It must not be a component in the strata that is expected to migrate, be adsorbed on clays, or degraded. It should be measurable in trace amounts and safe to handle. Examples of filtrate tracers include: (1) Radioactively tagged compounds (isotopes of elements). Tritium, a weakly-emitting radioisotope of hydrogen, can be a safe and effective tracer in both oil and water (as T2O) muds. It is measured by scintillation counts. (2) Bromide or iodide compounds are practical to use because they do not occur naturally in most muds or reservoirs. They are detectable in small amounts by electron-capture gas chromatography. (3) Fatty acids (or their derivatives) normally present in an oil-mud emulsifier can serve as oil-filtrate tracers and are analyzed by gas chromatography. (4) Nitrate (NO3-) anion, added as sodium, potassium or calcium nitrate, is one of the earliest tracers used. It is limited by being difficult to analyze and lost by degradation.
2636bland coring fluid, completion fluid, continuous phase, core, coring fluid, drill-in fluid, dynamic filtration, low-pressure, low-temperature filtration test, mud tracer, static filtration
2637None
2638None
2639--
2640flow cross
26411.n. [Well Completions, Well Workover and Intervention]
2642Pressure-containing equipment consisting of four or more flanged or studded connections used to control and direct fluid flow. A flow cross is typically a component of Christmas trees, where it connects the master valve, wing valves, and swab valve.
2643buffalo head, frac head, goat head
2644None
2645None
2646--
2647foamy oil
26481.n. [Heavy Oil]
2649An oil-continuous foam that contains dispersed gas bubbles produced at the wellhead from heavy oil reservoirs under solution gas drive. The nature of the gas dispersions in oil distinguishes foamy oil behavior from conventional heavy oil. The gas that comes out of solution in the reservoir does not coalesce into large gas bubbles nor into a continuous flowing gas phase. Instead it remains as small bubbles entrained in the crude oil, keeping the effective oil viscosity low while providing expansive energy that helps drive the oil toward the producing well. Foamy oil accounts for unusually high production in heavy oil reservoirs under solution-gas drive.
2650None
2651None
2652None
2653--
2654fresnel zone
26551.n. [Geophysics]
2656A frequency- and range-dependent area of a reflector from which most of the energy of a reflection is returned and arrival times differ by less than half a period from the first break, named for French physicist Augustin-Jean Fresnel (1788 to 1827). Waves with such arrival times will interfere constructively and so be detected as a single arrival. Subsurface features smaller than the Fresnel zone usually cannot be detected using seismic waves.
2657attenuation, first break, resolution, wave
2658None
2659None
2660--
2661filtration test cell
26621.n. [Drilling Fluids]
2663A pressurized cell, fitted with a filter medium, used for evaluating filtration characteristics of a drilling fluid while it is either static or stirred (to simulate circulation) in the test cell. Generally, either low-pressure, low-temperature or high-pressure, high-temperature devices are used.
2664drilling fluid, dynamic filter press, dynamic filtration, filter medium, filter press, filter-cake quality, filter-cake thickness, filtrate, fluid-loss control, fluid-loss-control material, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, spurt loss, static filtration
2665None
2666None
2667--
2668flow line
26691.n. [Drilling]
2670The large-diameter metal pipe that connects the bell nipple under the rotary table to the possum belly at the mud tanks. The flowline is simply an inclined, gravity-flow conduit to direct mud coming out the top of the wellbore to the mud surface-treating equipment. When drilling certain highly reactive clays, called "gumbo," the flowline may become plugged and require considerable effort by the rig crew to keep it open and flowing. In addition, the flowline is usually fitted with a crude paddle-type flow-measuring device commonly called a "flow show" that may give the driller the first indication that the well is flowing.
2671None
2672mud return line
2673flowline
2674--
2675flow line
26762.n. [Production Testing]
2677A surface pipeline carrying oil, gas or water that connects the wellhead to a manifold or to production facilities, such as heater-treaters and separators.
2678None
2679None
2680flowline
2681--
2682fold
26831.n. [Geology]
2684A wave-like geologic structure that forms when rocks deform by bending instead of breaking under compressional stress. Anticlines are arch-shaped folds in which rock layers are upwardly convex. The oldest rock layers form the core of the fold, and outward from the core progressively younger rocks occur. A syncline is the opposite type of fold, having downwardly convex layers with young rocks in the core. Folds typically occur in anticline-syncline pairs. The hinge is the point of maximum curvature in a fold. The limbs occur on either side of the fold hinge. The imaginary surface bisecting the limbs of the fold is called the axial surface. The axial surface is called the axial plane in cases where the fold is symmetrical and the lines containing the points of maximum curvature of the folded layers, or hinge lines, are coplanar. Concentric folding preserves the thickness of each bed as measured perpendicular to original bedding. Similar folds have the same wave shape, but bed thickness changes throughout each layer, with thicker hinges and thinner limbs.
2685anomaly, axial surface, collision, competent, competent, competent, competent, competent, competent, concentric fold, crest, disharmonic, drape, flower structure, harmonic, orogeny, parallel fold, plunge, similar fold, strain, structural trap, trend
2686None
2687None
2688--
2689fold
26902.n. [Geophysics]
2691A measure of the redundancy of common midpoint seismic data, equal to the number of offset receivers that record a given data point or in a given bin and are added during stacking to produce a single trace. Typical values of fold for modern seismic data range from 60 to 240 for 2D seismic data, and 10 to 120 for 3D seismic data. The fold of 2D seismic data can be calculated by dividing the number of seismometer groups by twice the number of group intervals between shotpoints.
2692common depth point, common midpoint, common midpoint method, common reflection point, quicklook, receiver, shotpoint, stack, trace, two-dimensional survey
2693None
2694None
2695--
2696friction reducer
26971.n. [Well Workover and Intervention]
2698An additive, generally in slurry or liquid form, used to reduce the friction forces experienced by tools and tubulars in the wellbore. Friction reducers are routinely used in horizontal and highly deviated wellbores where the friction forces limit the passage of tools along the wellbore.
2699None
2700None
2701None
2702--
2703filtration tester
27041.n. [Drilling Fluids]
2705Equipment used to measure filtration under dynamic conditions. Two commercial dynamic-filtration testers are available, one of which uses a thick-walled cylinder with rock-like characteristics as the filter medium to simulate radial flow into a wellbore. The other tester uses flat porous disks, such as paper or fused ceramic plates, as filter media. In a dynamic test, filter cake is continually eroded and deposited. Data from this test include a steady-state filtration rate measured during the test, and cake thickness, cake quality and return permeability of the filter medium measured at the conclusion of a test. There is no API standardized test equipment or procedure.
2706dynamic filtration, filter medium, filter press, filter-cake quality, filter-cake thickness, filtrate, fluid-loss-control material
2707None
2708None
2709--
2710flow loop
27111.n. [Production Logging]
2712A laboratory instrument for investigating the characteristics of fluid flow in pipes and for studying the response of production logging instruments to this flow. The fluids are circulated continuously in a loop, passing through one main measurement section that can be placed at different deviations from vertical through horizontal. Fluid properties, holdups and velocities can all be varied. Flow loops are essential for the study of multiphase flow and the development of new production logging measurements.
2713flow regime, flow structure, fluid flow, holdup, multiphase flow, production log, velocity
2714None
2715None
2716--
2717footprint
27181.n. [Geophysics]
2719The area covered by an array of towed streamers in marine seismic acquisition.
2720acquisition, array, streamer
2721None
2722None
2723--
2724footprint
27252.n. [Geophysics]
2726Variations in the properties of seismic data, encountered during processing, that are related to the acquisition geometry and distort the amplitude and phase of reflections. Also called acquisition footprint.
2727acquisition, amplitude, phase, reflection
2728None
2729None
2730--
2731froth flow
27321.n. [Well Completions, Production Logging]
2733A multiphase flow regime in near-vertical pipes in which large, irregular slugs of gas move up the center of the pipe, usually carrying droplets of oil or water with them. Most of the remaining oil or water flows up along the pipe walls. The flow is relatively chaotic, producing a frothy mixture. Unlike slug flow, neither phase is continuous. The gas slugs are relatively unstable, and take on large, elongated shapes. Also known as transition flow, this flow is an intermediate flow condition between slug flow and mist flow, and occurs at relatively high gas velocity. As the gas velocity increases, it changes into annular flow.
2734annular flow, bubble flow, churn flow, flow regime, flow structure, mist flow, slug, slug flow
2735None
2736None
2737--
2738final flow period
27391.n. [Well Testing]
2740The final flow sequence in a drillstem test. The initial shut-in period is usually followed immediately by an extended period of flow. The well is then shut in for the final buildup period. Data obtained during the final buildup period are analyzed to determine permeability thickness, kh, and skin effect, s. Final flow periods commonly range from 4 to 24 hours, and final buildup periods from 6 to 48 hours.
2741drillstem test, final shut-in period, flow period, initial shut-in period, permeability thickness, skin effect
2742None
2743Antonyms:initial flow period
2744--
2745flow meter
27461.n. [Well Workover and Intervention]
2747A device installed in a pump manifold or treating line to measure the fluid flow rate. Flowmeters can be used to measure the flow rates of liquid or gas and are available in various configurations and with differing operating principles.
2748flowmeter, fluid flow, pump manifold
2749None
2750None
2751--
2752flow meter
27532.n. [Production Logging]
2754A device for measuring in-situ the velocity of fluid flow in a well, usually one completed for production or injection. The most common device is the spinner flowmeter, but torque flowmeters and crosscorrelation flowmeters also are used. In the 1940s and 1950s, various other surface-metering techniques were tried, but spinner flowmeters emerged as the most suitable for measuring downhole velocities. Spinner and torque flowmeters measure the average velocity of the fluids crossing the device, while crosscorrelation flowmeters measure the velocity of a particular phase.Although not normally called flowmeters, various other techniques measure flow velocity, for example water-flow logs, phase-velocity logs, distributed-temperature logs and even audio measurements.
2755audio measurement, average velocity, crosscorrelation flowmeter, distributed-temperature log, fluid flow, phase-velocity log, production log, spinner flowmeter, torque flowmeter, water-flow log
2756None
2757None
2758--
2759flow meter
27603.n. [Production Testing]
2761An instrument that measures the flow rate of fluids through a pipeline. There are several types of flowmeters, including the differential-pressure meter, orifice meter, positive-displacement meter, vortex meter and multiphase meters.
2762multiphase meter, orifice meter
2763None
2764None
2765--
2766formate
27671.n. [Drilling Fluids]
2768A class of salts made from neutralization of formic acid with a metal hydroxide or oxide. Three alkali-metal formates are used in drilling, drill-in and completion fluids, (1) sodium formate, HCOO-Na+, (2) potassium formate, HCOO-K+ and (3) cesium formate, HCOO-Cs+. Clear solutions of each can reach densities of 1.32, 1.58 and 2.4 g/cm3, respectively. They are near neutral pH and meet HSE standards. Most formates can be mixed together over broad ranges of concentration or temperature without solubility or crystallization problems.
2769brine, cesium acetate, cesium formate, completion fluid, drill-in fluid, drilling fluid, formic acid, mud weight
2770None
2771None
2772--
2773fullbore
27741.adj. [Well Completions]
2775A description of the internal area and surfaces of a tool or tubular assembly through which there is an unimpeded internal diameter. In some cases, fullbore is used to describe the form of a nominal internal diameter that extends over the length of the tool or interval without any variation. In other applications, the term simply implies an ability to pass a ball or similar item of a stated drift diameter through the assembly.
2776None
2777None
2778None
2779--
2780final shut in period
27811.n. [Well Testing]
2782The final buildup sequence in a drillstem test. The initial shut-in period is usually followed immediately by an extended period of flow. The well is then shut in for the final buildup period. Data obtained during this period are analyzed to determine permeability thickness, kh, and skin effect, s. Final flow periods commonly range from 4 to 24 hours, and final buildup periods from 6 to 48 hours.
2783buildup test, drillstem test, final flow period, final flow rate, final flowing pressure, initial shut in period, permeability thickness, skin effect
2784None
2785None
2786--
2787flow model
27881.n. [Reservoir Characterization]
2789A model of a reservoir in which the steady-state flow and the advective transport are described in two or three dimensions by a computer program. A flow model is an essential component of a reservoir simulator. Flow models are often derived from the petrophysical characteristics of a reservoir (especially porosities and permeabilities) and then the model is adjusted and refined until it correctly predicts the reservoir's past behavior and can match the historical pressure and production data.
2790advective transport modeling, flow simulation, history matching, reservoir simulation, steady state
2791None
2792None
2793--
2794formation damage
27951.n. [Drilling]
2796Alteration of the far-field or virgin characteristics of a producing formation, usually by exposure to drilling fluids. The water or solid particles in the drilling fluids, or both, tend to decrease the pore volume and effective permeability of the producible formation in the near-wellbore region. At least two mechanisms are at work. First, solid particles from the drilling fluid physically plug or bridge across flowpaths in the porous formation. Second, when water contacts certain clay minerals in the formation, the clay typically swells, increasing in volume and decreasing the pore volume. Third, chemical reactions between the drilling fluid and the formation rock and fluids can precipitate solids or semisolids that plug pore spaces. One approach to minimize formation damage is to use drill-in or completion fluids that are specially formulated to avoid damage to the formation when drilling pay zones, rather than ordinary drilling fluids.
2797bridge, completion fluid, drill-in fluid, drilling fluid
2798None
2799None
2800--
2801formation damage
28022.n. [Drilling Fluids]
2803A reduction in the natural capability of a reservoir to produce its fluids, such as a decrease in porosity or permeability, or both. Damage can occur near the wellbore face (easier to repair) or deep into the rock (harder to repair). Damage is caused by several mechanisms: (1) physical plugging of pores by mud solids, (2) alteration of reservoir rock wettability, (3) precipitation of insoluble materials in pore spaces, (4) clay swelling in pore spaces, (5) migration of fines into pore throats, (6) introduction of an immobile phase, and (7) emulsion formation and blockage. Damage can occur when sensitive formations are exposed to drilling fluids.
2804bridging material, completion fluid, drill-in fluid, drilling fluid, emulsion, fines, pore throat, scale
2805None
2806None
2807--
2808formation damage
28093.n. [Well Completions]
2810A general term to describe the reduction in permeability to the near-wellbore area of a reservoir formation. There are several recognized damage mechanisms, such as the invasion of incompatible fluids swelling the formation clays, or fine solids from dirty fluids plugging the formation matrix. Because formation damage can significantly affect the productivity of any well, adequate precautions should be exercised to avoid damage during all phases in the life of a well.
2811None
2812None
2813None
2814--
2815formation damage
28164.n. [Enhanced Oil Recovery]
2817Natural or inducedproductionimpairments that can develop in thereservoir, the near-wellbore area or the perforations. Natural damage occurs as produced reservoir fluids move through the reservoir, while induced damage is the result of external operations and fluids in the well, such as drilling, well completion,workoveroperations or stimulation treatments. Some induced damage triggers natural damage mechanisms.Natural damage includes phenomena such asfinesmigration,clayswelling,scaleformation, organic deposition, including paraffins orasphaltenes, and mixed organic and inorganic deposition. Induced damage includes plugging caused by foreign particles in the injected fluid,wettabilitychanges, emulsions, precipitates or sludges caused byacidreactions, bacterial activity and water blocks.Wellborecleanup or matrix stimulation treatments are two different operations that can remove natural or induced damage. Selecting the proper operation depends on the location and nature of the damage.
2818clay swelling, damage, emulsion, fines migration, matrix stimulation, paraffin control, scale removal, water block
2819None
2820None
2821--
2822fwko
28231.n. [Production Facilities]
2824A vertical or horizontal separator used mainly to remove any free water that can cause problems such as corrosion and formation of hydrates or tight emulsions, which are difficult to break.A free-water knockout is commonly called a three-phase separator because it can separate gas, oil and free water. The liquids that are discharged from the free-water knockout are further treated in vessels called treaters. Free-water knockout is abbreviated as FWKO.
2825free water, treater, vertical separator
2826None
2827Antonyms:three phase separator
2828--
2829Galling
28301.n. [Production]
2831The tearing of metal when two elements rub against each other. Usually caused by lack of lubrication or extreme contact pressure.
2832None
2833None
2834None
2835--
2836gas holdup log
28371.n. [Production Logging]
2838A record of the fraction of gas present at different depths in the borehole. Although several techniques may be used for this purpose, the term usually refers to logs based on one of two principles. In the first, four or more optical probes are used to detect the passage of gas bubbles at different points across the borehole. As with other local probes, holdup is determined by the fraction of time the probe detects gas. In the second technique, a 57Co (cobalt) source emits low-energy gamma rays that undergo backscattering and photoelectric absorption in the borehole fluid before being counted in a detector. The number of counts is related to the fluid density, and can be calibrated in terms of gas holdup.The first technique produces an image of gas holdup along and around the borehole, while the second technique produces a log of the average holdup along the well.
2839backscatter, holdup log, optical probe, production log
2840None
2841None
2842--
2843geopressured
28441.adj. [Geology]
2845Subject to the pressure within the Earth, or formation pressure. The common oilfield usage, however, is to indicate anomalous subsurface pore pressure that is higher or lower than the normal, predicted hydrostatic pressure for a given depth, or the pressure exerted per unit area by a column of fresh water from sea level to a given depth. Abnormally low pore pressure might occur in areas where fluids have been drained, such as a depleted hydrocarbon reservoir. Abnormally high pore pressure might occur in areas where burial of water-filled sediments by an impermeable sediment such as clay was so rapid that fluids could not escape and the pore pressure increased with deeper burial.
2846abnormal pressure, compaction, formation pressure, geopressure, geopressure gradient, geostatic pressure, hydrostatic pressure, overpressure, pore pressure
2847None
2848None
2849--
2850gravel pack gun
28511.n. [Perforating]
2852A perforating-gun system containing big-hole or gravel-pack charges. A gravel-pack gun usually has a large outside diameter to minimize standoff between the gun and casing. It is loaded to achieve a high shot density while producing large holes in the casing.
2853big-hole charge, outside diameter, perforating gun
2854None
2855None
2856--
2857galvanic anodes
28581.n. [Enhanced Oil Recovery]
2859Materials used to provide cathodic protection. Galvanic anodes are made of metals such as zinc, magnesium or aluminum, which corrode more easily than the structure, thus developing enough electric current flow through the electrolyte (such as soils or water).Galvanic anodes, also called sacrificial anodes, are commonly used when the current required for cathodic protection is small.
2860cathodic protection, impressed current anodes
2861None
2862sacrificial anode
2863--
2864gas water contact
28651.n. [Geology]
2866A bounding surface in a reservoir above which predominantly gas occurs and below which predominantly water occurs. Gas and water are somewhat miscible, so the contact between gas and water is not necessarily sharp and there is typically a transition zone between 100% gas and 100% water in reservoirs.
2867fluid contact, gas-oil contact, immiscible, oil-water contact, reservoir
2868None
2869GWC
2870--
2871geostatic pressure
28721.n. [Geology]
2873The pressure of the weight of overburden, or overlying rock, on a formation; also called lithostatic pressure.
2874abnormal pressure, formation pressure, geopressure, normal pressure, overpressure
2875None
2876lithostatic pressure
2877--
2878gravel pack gun
28791.n. [Perforating]
2880A perforating-gun system containing big-hole or gravel-pack charges. A gravel-pack gun usually has a large outside diameter to minimize standoff between the gun and casing. It is loaded to achieve a high shot density while producing large holes in the casing.
2881big-hole charge, outside diameter, perforating gun
2882None
2883None
2884--
2885gamma
28861.n. [Geophysics]
2887An S-wave parameter for a medium in which the elastic properties exhibit vertical transverse isotropy. Gamma (γ) is the S-wave anisotropy parameter and is equal to half the ratio of the difference between the horizontally and vertically traveling SH-wave velocities squared divided by the vertically traveling SH-wave velocity squared; an SH-wave is a shear wave that is horizontally polarized.γ ≡ ½ [(C66 − C44) / C44] = ½ [(VSH⊥2 − VSH∥2) / VSH∥2]S-wave parameter (γ) for a medium in which the elastic properties exhibit vertical transverse isotropy, where C66 is the modulus for a horizontally polarized and horizontally traveling S-wave (perpendicular to the symmetry axis), C44 is the modulus for a horizontally polarized and vertically traveling S-wave (parallel to the symmetry axis), VSH⊥ is the velocity for a horizontally polarized and horizontally traveling S-wave and VSH∥ is the velocity for a horizontally polarized and vertically traveling S-wave.
2888None
2889None
2890None
2891--
2892gate valve
28931.n. [Well Completions]
2894A type of valve that incorporates a sliding gate to block fluid flow. The design of the valve operating and sealing systems typically requires that gate valves should be operated either fully open or fully closed.
2895fluid flow
2896None
2897None
2898--
2899gate valve
29002.n. [Production]
2901A straight-through pattern valve whose closure element is a wedge or parallel-sided slab, situated between two fixed seating surfaces with means to move it in or out of the flow stream in a direction perpendicular to the pipeline axis.
2902None
2903None
2904None
2905--
2906geostatistical modeling
29071.n. [Reservoir Characterization]
2908The process of generating models of the subsurface using geostatistical methods. The methods derive a detailed model using only sparse data (such as logs and cores from a few wells in a large area) and a knowledge of the depositional systems and structural settings to estimate the subsurface characteristics between the wells. These methods were originally developed in the mining industry, where boreholes are generally much closer, and later were adapted for use in the oil and gas industry. Geostatistical models are used for reservoir simulation and reservoir management.
2909depositional system, geostatistical methods, geostatistics, kriging, reservoir simulation
2910None
2911None
2912--
2913graveyard tour
29141.n. [Drilling]
2915The overnight work shift of a drilling crew. Drilling operations usually occur around the clock because of the cost to rent arig.As a result, there are usually two separate crews working twelve-hour tours to keep the operation going. Some companies prefer three eight-hour tours. The graveyard tour is the shift that begins at midnight. (Pronounced "tower" in many areas.)
2916daylight tour, drilling crew, evening tour, morning tour, tour
2917None
2918None
2919--
2920gamma ray densitometer
29211.n. [Production Logging]
2922A device for measuring the density of fluids in a completed well, using a radioactive source of gamma rays and a detector. In most instruments, a 137Cs (cesium) or 241Am (americium) source is used to induce Compton scattering, as in the openhole density measurement, except that the device is unfocused. The count rate at the detector then depends primarily on the density of the fluids in the well. In some devices, the fluids pass through an open space in the body of the tool within which the measurement is made. The results then reflect the density of the fluids passing through the tool. In other devices, the source and detector are isolated so that the gamma rays pass outside the tool. The results then reflect some average density of all the fluids within the well. In smaller casings, some formation signal may contaminate the measurement.Compared with a gradiomanometer, the nuclear fluid densimeter is a less direct measurement of density, and has a statistical uncertainty and less resolution. On the other hand, it is not affected by well deviation, friction or kinetic effects.
2923fluid-density log, holdup log, photon log, production log
2924None
2925None
2926--
2927gathering system
29281.n. [Production Facilities]
2929The flowline network and process facilities that transport and control the flow of oil or gas from the wells to a main storage facility, processing plant or shipping point. A gathering system includes pumps, headers, separators, emulsion treaters, tanks, regulators, compressors, dehydrators, valves and associated equipment.There are two types of gathering systems, radial and trunk line. The radial type brings all the flowlines to a central header, while the trunk-line type uses several remote headers to collect fluid. The latter is mainly used in large fields.The gathering system is also called the collecting system or gathering facility.
2930compressor, dehydrator, gas processing plant, separator, tank, treater
2931None
2932None
2933--
2934geostatistics
29351.n. [Reservoir Characterization]
2936The study of samples of data from a complete data set (or population) to attempt to estimate the behavior of the population. Typically, geostatistics is applied during the creation of high-resolution subsurface models of mineral deposits or oil reservoirs. The data are available only from well cores and logs (high vertical resolution but laterally infrequent data samples) and from surface seismic (low vertical resolution) data. Geostatistically derived reservoir models, when successful, are used in reservoir simulations and for reservoir management.
2937geostatistical modeling, kriging, log, reservoir modeling, reservoir simulation, vertical resolution
2938None
2939None
2940--
2941gravimeter
29421.n. [Geophysics]
2943A device used to measure the acceleration due to gravity, or, more specifically, variations in the gravitational field between two or more points.
2944detector, gravimetry
2945None
2946None
2947--
2948gamma ray interactions
29491.n. [Formation Evaluation]
2950Phenomena resulting from the transfer of energy from a gamma ray to matter, usually to an electron. The probability of a specific interaction occurring depends on the atomic number of the material and the energy of the gamma ray. In formation evaluation, there are two types of interactions of interest: the photoelectric effect, which indicates lithology, and Compton scattering, which depends on formation density. The third type of interaction, pair production, occurs at energies above those used for logging.
2951Compton scattering, pair production, photoelectric effect, scintillation detector
2952None
2953None
2954--
2955gauge hole
29561.n. [Drilling]
2957A wellbore that is essentially the same diameter as the bit that was used to drill it. It is common to find well-consolidated sandstones and carbonate rocks that remain gauge after being drilled. For clays, it is common for the hole to slowly enlarge with the passing of time, especially if water-base muds are being used. Bit gauges, rings of defined circumference, are slipped around drill bits to detect and measure wear, which reduces the circumference of the bit during drilling.
2958drill bit, erosion, water-base drilling fluid
2959None
2960None
2961--
2962geosteer
29631.vb. [Drilling]
2964To control the direction of a well based on the results of downholegeologicallogging measurements rather than three-dimensional targets in space, usually to keep a directional wellbore within apayzone. In mature areas, geosteering may be used to keep a wellbore in a particular section of areservoirto minimize gas or waterbreakthroughand maximize economicproductionfrom the well.
2965directional drilling, geosteering
2966None
2967None
2968--
2969gravity anomaly
29701.n. [Geophysics]
2971The difference between the actual value of gravity measured at a location and the value predicted by a particular Earth model. Gravity anomalies are usually determined by adjusting the known value of (absolute) gravity at a reference station by Bouguer, free-air or other corrections and subtracting the final predicted value from the measurement. (A different description is that the various corrections are subtracted from the data to reduce it to the reference level. Both interpretations are valid provided it is remembered that the resulting gravity anomaly can be caused by density anomalies-i.e., differences in density between Earth and the theoretical model-that can lie anywhere either above or below the reference level.)
2972anomaly, Bouguer correction, free-air correction, gravity
2973None
2974None
2975--
2976gamma ray log
29771.n. [Drilling]
2978A common and inexpensive measurement of the natural emission of gamma rays by a formation. Gamma ray logs are particularly helpful because shales and sandstones typically have different gamma ray signatures that can be correlated readily between wells.
2979signature
2980None
2981None
2982--
2983gamma ray log
29842.n. [Formation Evaluation]
2985A log of the total natural radioactivity, measured in API units. The measurement can be made in both openhole and through casing. The depth of investigation is a few inches, so that the log normally measures the flushed zone.Shales and clays are responsible for most natural radioactivity, so the gamma ray log often is a good indicator of such rocks. However, other rocks are also radioactive, notably some carbonates and feldspar-rich rocks. The log is also used for correlation between wells, for depth correlation between open and cased hole, and for depth correlation between logging runs. The gamma ray log was the first nuclear well log and was introduced in the late 1930s.
2986cased hole, corrected gamma ray, depth correlation, depth of investigation, flushed zone, logging run, natural gamma ray spectroscopy, openhole, potassium, scintillation detector, thorium, uranium
2987None
2988None
2989--
2990gauge ring
29911.n. [Well Completions]
2992A precisely machined test device, typically fabricated from steel or similar durable material, having a specified internal or external diameter. The gauge ring is used to confirm the dimensional compatibility of tools and equipment that must pass through restrictions of a certain diameter.
2993inside diameter, outside diameter
2994None
2995None
2996--
2997geosteering
29981.n. [Drilling]
2999The intentional directional control of a well based on the results of downhole geological logging measurements rather than three-dimensional targets in space, usually to keep a directional wellbore within a pay zone. In mature areas, geosteering may be used to keep a wellbore in a particular section of a reservoir to minimize gas or water breakthrough and maximize economic production from the well.
3000directional drilling, geosteer
3001None
3002None
3003--
3004gravity drainage
30051.n. [Enhanced Oil Recovery]
3006The least common primary recovery mechanism in which the force of gravity pushes hydrocarbons out of the reservoir, into the wellbore and up to surface.Gravity force is always present in the reservoir, but its effect is greater in thick gas-condensate reservoirs and in shallow, highly permeable, steeply dipping reservoirs.
3007gas condensate, gasdrive, hydrocarbon, primary recovery, waterdrive
3008None
3009None
3010--
3011gas anchor
30121.n. [Production Testing]
3013A perforated tubular attached to the subsurface sucker-rod pump that controls the entrance of gas. Since it is the only way for formation fluid to enter the pump, its use increases the efficiency of the subsurface sucker-rod pump. It also helps to prevent the phenomenon called gas lock. A gas anchor is similar to a bottomhole gas separator.
3014formation fluid, gas lock, rod pump, sucker rod
3015bottomhole gas separator
3016None
3017--
3018gauge tank
30191.n. [Well Workover and Intervention]
3020A small tank with accurate volume markings used to measure flow into or out of a well. Treatments that require accurate volume tracking of fluids, such as squeeze cementing, generally use a gauge tank to measure fluid volumes.
3021squeeze cementing
3022None
3023None
3024--
3025geothermal gradient
30261.n. [Geology, Drilling Fluids]
3027The rate of increase in temperature per unit depth in the Earth. Although the geothermal gradient varies from place to place, it averages 25 to 30°C/km [15°F/1000 ft].Temperature gradients sometimes increase dramatically aroundvolcanic areas. It is particularly important for drilling fluids engineers to know the geothermal gradient in an area when they are designing a deep well. The downhole temperature can be calculated by adding the surface temperature to the product of the depth and the geothermal gradient.
3028high-pressure, high-temperature filtration test, mud engineer
3029temperature gradient, thermal gradient
3030None
3031--
3032gravity override
30331.n. [Enhanced Oil Recovery]
3034A phenomenon of multiphase flow in a reservoir in which a less dense fluid flows preferentially on the top of a reservoir unit and a more dense fluid flows at the bottom. For example, in a steamflood, steam flows on the top and condensed liquid flows at the bottom of the zone. Gravity override causes sweep inhomogeneities that can be mitigated through foam flooding.
3035vertical displacement efficiency
3036None
3037None
3038--
3039gas bearing
30401.adj. [Well Completions]
3041Relating to a formation or interval containing gas, either dissolved in the formation fluid or as free gas. The term is occasionally used to describe wellbore fluids containing dissolved gas.
3042formation fluid, free gas, gas-lift mandrel
3043None
3044None
3045--
3046gaussian collocated cosimulation
30471.n. [Reservoir Characterization]
3048An algorithm built on a Markov-type hypothesis, whereby collocated secondary information is assumed to screen out secondary data from farther away. The method allows the direct cosimulation of several interdependent variables, integrating several different sources of soft information.Reference:Almeida AS and Frykman P: "Geostatistical Modeling of Chalk Reservoir Properties in the Dan Field, Danish North Sea," in Yarus JM and Chambers RL (eds): Stochastic Modeling and Geostatistics, AAPG Computer Applications in Geology, no. 3. AAPG, Tulsa, Oklahoma, USA, 1994.
3049None
3050None
3051None
3052--
3053ghost
30541.n. [Geophysics]
3055A short-path multiple, or a spurious reflection that occurs when seismic energy initially reverberates upward from the shallow subsurface and then is reflected downward, such as at the base of weathering or between sources and receivers and the sea surface.
3056base of weathering, multiple reflection, receiver, short-path multiple, source
3057None
3058None
3059--
3060gravity survey
30611.n. [Geophysics]
3062The measurement of gravitational acceleration over an area, usually presented as a map or profile of Bouguer or free-air anomalies.
3063Bouguer anomaly, free-air correction, survey
3064None
3065None
3066--
3067gas buster
30681.n. [Well Workover and Intervention]
3069A simple separator vessel used to remove free or entrained gas from fluids circulated in the wellbore, such as mud used during drilling operations. The gas buster typically comprises a vessel containing a series of baffles with a liquid exit on the bottom and a gas-vent line at the top of the vessel.
3070entrained gas, free gas
3071None
3072None
3073--
3074gaussian techniques
30751.n. [Reservoir Characterization]
3076A parametric approach to stochastic imaging or simulation of a reservoir. Simpler than the indicator (nonparametric) approach, Gaussian techniques include a normal score transform of the data to produce a new variable that is, by construction, univariate and normally distributed.
3077indicator methods, stochastic modeling
3078None
3079None
3080--
3081giip
30821.n. [General Terms, Shale Gas]
3083Abbreviation for gas initially in place, the volume of gas in a reservoir before production.
3084None
3085None
3086None
3087--
3088gray list
30891.n. [Drilling Fluids]
3090Products 'requiring strong regulatory control,' as determined by the Oslo and Paris Commission (OSPAR).The list includes heavy metals such as zinc, lead and chromium. OSPAR, formerly known as PARCOM, is a group of experts who advise North Sea countries on environmental policy and legislation. The group has been influential in establishing North Sea legislation on drilling fluids that has served as the modelfor other operating areas. The Commission has published lists of environmentally acceptable and unacceptable products, referred to as the "green," "grey" and "black" lists.
3091bioaccumulation, black list, green list, HSE, OSPAR, PARCOM
3092None
3093None
3094--
3095gas cut mud
30961.n. [Drilling]
3097Drilling fluid whose bulk, unpressurized density is reduced as a small volume of gas displaces an equivalent volume of liquid. The derrickman periodically measures mud density and communicates the results to the rig team via an intercom. He usually reports something like "9.6 heavy," "10.4," or "13.2 light," indicating more than 9.6 pounds per gallon, 10.4 pounds per gallon, or less than 13.2 pounds per gallon, respectively. Each tenth of a pound per gallon is referred to as a "point" of mud weight. Note that for this low-accuracy measurement, no direct mention of gas cut is made. A gas cut is inferred only if the mud returning to the surface is significantly less dense than it should be. In the case of the mud logger's measurement, "units" of gas (having virtually no absolute meaning) are reported. For the mud logger's measurement, a direct indication of combustible gases is made, with no direct correlation to mud weight.
3098None
3099None
3100gas-cut mud
3101--
3102gelled mud
31031.n. [Drilling Fluids]
3104A mud that is excessively viscous, having high gel strengths and high yield point. A gelled-up mud may not be pumpable without exceeding limits on pump pressure. Often caused by excessive solids content, especially colloidal solids, or, in the case of oil or synthetic muds, by low temperature.
3105colloidal solids, gel strength, oil mud, progressive gels, shear-strength measurement test, yield point
3106None
3107None
3108--
3109gilsonite
31101.n. [Drilling Fluids]
3111A generic name widely used for a black, lustrous, carbonaceous resin classified as an asphaltite. Its proper name is uintaite, and it is found in Utah, USA. An important characteristic of gilsonite is its softening-point temperature. In oil-base muds, it is used as a fluid-loss control agent. Being a hydrocarbon, it is naturally wetted by the oil. In water-base muds, it is used as a shale-stabilizing additive and is difficult to evaluate unless tested at or above its softening point. As a hydrocarbon, the powder must be coupled to water by using a glycol or similar water-wetter.
3112fluid-loss control, low-colloid oil mud, oil-base mud, water-base drilling fluid, water-wet, wettability
3113None
3114None
3115--
3116gilsonite
31172.n. [Drilling Fluids]
3118A trademarked product of American Gilsonite Co.
3119None
3120None
3121None
3122--
3123green list
31241.n. [Drilling Fluids]
3125Products posing relatively little harm to the environment (specifically themarineenvironment), as determined by the Oslo and Paris Commission (OSPAR). Examples of products that comprise the Green or A list include inert minerals such asbentonite, inorganic salts that are common constituents of seawater such as sodium andpotassiumchloride, and simple organic products such asstarchandcarboxymethylcellulose(CMC). OSPAR, formerly known as PARCOM, is a group of experts who advise North Sea countries on environmental policy and legislation. The group has been influential in establishing North Sea legislation on drilling fluids that has served as the modelfor other operating areas. The Commission has published lists of environmentally acceptable and unacceptable products, referred to as the "green," "grey" and "black" lists.
3126black list, gray list, grey list, OSPAR, PARCOM
3127None
3128None
3129--
3130gas holdup log
31311.n. [Production Logging]
3132A record of the fraction of gas present at different depths in the borehole. Although several techniques may be used for this purpose, the term usually refers to logs based on one of two principles. In the first, four or more optical probes are used to detect the passage of gas bubbles at different points across the borehole. As with other local probes, holdup is determined by the fraction of time the probe detects gas. In the second technique, a 57Co (cobalt) source emits low-energy gamma rays that undergo backscattering and photoelectric absorption in the borehole fluid before being counted in a detector. The number of counts is related to the fluid density, and can be calibrated in terms of gas holdup.The first technique produces an image of gas holdup along and around the borehole, while the second technique produces a log of the average holdup along the well.
3133backscatter, holdup log, optical probe, production log
3134None
3135None
3136--
3137gelled up mud
31381.n. [Drilling Fluids]
3139A mud that is excessively viscous, having high gel strengths and high yield point. A gelled-up mud may not be pumpable without exceeding limits on pump pressure. Often caused by excessive solids content, especially colloidal solids, or, in the case of oil or synthetic muds, by low temperature.
3140None
3141None
3142gelled-up mud
3143--
3144globe valve
31451.n. [Production]
3146A valve whose closure element is a flat disc or conical plug sealing on a seat that is usually parallel to the flow axis. The tortuous flow path produces a relatively high pressure loss.
3147gate valve
3148None
3149None
3150--
3151grey list
31521.n. [Drilling Fluids]
3153Products 'requiring strong regulatory control,' as determined by the Oslo and Paris Commission (OSPAR).The list includes heavy metals such as zinc, lead and chromium. OSPAR, formerly known as PARCOM, is a group of experts who advise North Sea countries on environmental policy and legislation. The group has been influential in establishing North Sea legislation on drilling fluids that has served as the modelfor other operating areas. The Commission has published lists of environmentally acceptable and unacceptable products, referred to as the "green," "grey" and "black" lists.
3154black list, green list, grey list, OSPAR, PARCOM
3155None
3156None
3157--
3158gas hydrate
31591.n. [Geology]
3160An unusual occurrence of hydrocarbon in which molecules of natural gas, typically methane, are trapped in ice molecules. More generally, hydrates are compounds in which gas molecules are trapped within a crystal structure. Hydrates form in cold climates, such as permafrost zones and in deep water. To date, economic liberation of hydrocarbon gases from hydrates has not occurred, but hydrates contain quantities of hydrocarbons that could be of great economic significance. Hydrates can affect seismic data by creating a reflection or multiple.
3161methane hydrate, natural gas
3162None
3163None
3164--
3165gas hydrate
31662.n. [Drilling Fluids]
3167A crystalline solid consisting of water with gas molecules in an ice-like cage structure. The general term for this type of solid is clathrate. Water molecules form a lattice structure into which many types of gas molecules can fit. Most gases, except hydrogen and helium, can form hydrates. C1 to nC5 hydrocarbons, H2S and CO2 readily form hydrates at low temperature and high pressure. Heavier hydrocarbons may also enter the structure but do not form hydrates by themselves. Gas-cut muds can form hydrates in deepwater drilling operations, plugging BOP lines, risers and subsea wellheads, causing a well-control risk. Gas hydrates are thermodynamically suppressed by adding antifreeze materials such as salts or glycols. A common practice is to use 20 to 23 wt.% NaCl. Nucleation and growth of hydrates can be dynamically inhibited by certain polymers or surfactants. Gas hydrates are found in nature, on the bottom of cold seas and in arctic permafrost regions. Drilling into these can be hazardous, but they offer another source of hydrocarbons for future exploitation.Reference:Ebeltoft H, Yousif M and Soergaard E: "Hydrate Control During Deep-water Drilling: Overview and New Drilling Fluids Formulations," paper SPE 38567, presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, October 5-8, 1997.
3168clathrate, drilling riser, gas-cut mud, glycol, polymer, surfactant
3169None
3170None
3171--
3172gelled up mud
31731.n. [Drilling Fluids]
3174A mud that is excessively viscous, having high gel strengths and high yield point. A gelled-up mud may not be pumpable without exceeding limits on pump pressure. Often caused by excessive solids content, especially colloidal solids, or, in the case of oil or synthetic muds, by low temperature.
3175colloidal solids, gel strength, oil mud, progressive gels, shear-strength measurement test, yield point
3176None
3177None
3178--
3179glycol dehydrator
31801.n. [Production Facilities]
3181A unit used to remove minute water particles from natural gas if dehydration was not attained using separators. A glycol dehydrator unit is usually composed of an absorber and a reboiler.The wet gas enters at the bottom of the absorber. As the wet gas percolates upward, it releases its water into the glycol solution and dry gas is obtained at the top of the absorber.When the glycol solution becomes saturated with water, the glycol solution is pumped through a reboiler, also called a reconcentrator, which boils the glycol-water mixture and separates the glycol from the water. After separation, the glycol can return to the absorber to contact additional wet gas.
3182dehydrate, desiccant, dry gas, natural gas, separator, wet gas
3183None
3184None
3185--
3186gridding
31871.n. [Reservoir Characterization]
3188The act of determining values for grid elements on a map. The grid element values are chosen from nearby data points. Methods are deterministic and use linear and nonlinear interpolation methods, or may be statistical and use geostatistical approaches such as kriging. Gridding is usually applied to one characteristic per map, such as structure, thickness, porosity, permeability or saturation.
3189geostatistical methods
3190None
3191grid
3192--
3193gas lift
31941.n. [Well Completions]
3195An artificial-lift method in which gas is injected into the production tubing to reduce the hydrostatic pressure of the fluid column. The resulting reduction in bottomhole pressure allows the reservoir liquids to enter the wellbore at a higher flow rate. The injection gas is typically conveyed down the tubing-casing annulus and enters the production train through a series of gas-lift valves. The gas-lift valve position, operating pressures and gas injection rate are determined by specific well conditions.
3196artificial lift, bottomhole pressure, gas injection, hydrostatic pressure
3197None
3198None
3199--
3200geochemical log
32011.n. [Formation Evaluation]
3202A log of elemental concentrations from which the geochemistry of the formation may be derived. Several logs provide information on elemental weight concentrations: natural gamma ray spectroscopy, elemental capture spectroscopy or pulsed neutron spectroscopy and aluminum activation. The combination of some or all of their outputs is known as a geochemical log, since it provides information on most of the principal elements found in sedimentary rocks. Pulsed neutron spectroscopy provides relative elemental yields, whereas absolute concentrations are needed for quantitative results. Absolute concentrations can be derived by calibration to core or by using a model such as the oxide-closure model. The absolute elemental concentrations can then be converted into mineral concentrations using a model that defines what minerals are present. The first complete geochemical logs were run in the mid 1980s.
3203aluminum activation log, elemental capture spectroscopy, natural gamma ray spectroscopy, oxide-closure model, pulsed neutron spectroscopy log
3204None
3205None
3206--
3207goat head
32081.n. [Shale Gas, Well Completions, Well Workover and Intervention]
3209A flow cross installed on top of a frac tree where treating iron is connected and treatment fluid enters the frac tree.
3210None
3211None
3212buffalo head, frac head
3213--
3214ground roll
32151.n. [Geophysics]
3216A type of coherent noise generated by a surface wave, typically a low-velocity, low-frequency, high-amplitude Rayleigh wave. Ground roll can obscure signal and degrade overall data quality, but can be alleviated through careful selection of source and geophone arrays, filters and stacking parameters.
3217acquisition, array, coherent noise, mute, random noise, Rayleigh wave, stack, surface wave, tail mute, water-bottom roll
3218None
3219None
3220--
3221gas lock
32221.n. [Well Completions]
3223A condition in pumping and processing equipment caused by the induction of free gas. The compressible gas interferes with the proper operation of valves and other pump components, preventing the intake of fluid.
3224free gas
3225None
3226None
3227--
3228gas lock
32292.n. [Production Testing]
3230A condition sometimes encountered in a pumping well when dissolved gas, released from solution during the upstroke of the plunger, appears as free gas between the valves. On the downstroke, pressure inside a barrel completely filled with gas may never reach the pressure needed to open the traveling valve. In the upstroke, the pressure inside the barrel never decreases enough for the standing valve to open and allow liquid to enter the pump. Thus no fluid enters or leaves the pump, and the pump is locked. It does not cause equipment failure, but with a nonfunctional pump, the pumping system is useless.A decrease in pumping rate is accompanied by an increase of bottomhole pressure (or fluid level in the annulus). In many cases of gas lock, this increase in bottomhole pressure can exceed the pressure in the barrel and liquid can enter through the standing valve. After a few strokes, enough liquid enters the pump that the gas lock in broken, and the pump functions normally.
3231bottomhole pressure, free gas, pumping well, standing valve, traveling valve
3232None
3233None
3234--
3235geochronology
32361.n. [Geology]
3237The study of the relative or absolute age of rocks, minerals and fossils. Absolute age is the measurement of age in years, but "absolute" ages typically have some amount of error and are inexact. Relative age, in contrast, is the approximate age of rocks, fossils or minerals made by determining the age of the material relative to other surrounding material.
3238absolute age, geologic time scale, geomagnetic polarity reversal, geomagnetic polarity time scale, paleontology, relative age, stratigraphy, superposition, varve
3239None
3240None
3241--
3242goose neck
32431.n. [Drilling]
3244An inverted "U" shaped section of rigid piping normally used as a conduit for high-pressure drilling fluid. In particular, the term is applied to a structure that connects the top of a vertical standpipe running up the side of a derrick or mast to a flexible kelly hose that in turn is connected to another gooseneck between the flexible line and the swivel.
3245None
3246None
3247gooseneck
3248--
3249goose neck
32502.n. [Well Workover and Intervention]
3251The assembly mounted on a coiled tubing injector head that guides the tubing string as it passes through an arc from the reel into a vertical alignment with the injector-head chains and wellbore. The radius of the guide arch is generally designed to be as large as practicable since the plastic deformation created in the coiled tubing string induces material fatigue in the tube.
3252None
3253None
3254gooseneck
3255--
3256growth fault
32571.n. [Geology]
3258A type of normal fault that develops and continues to move during sedimentation and typically has thicker strata on the downthrown, hanging wall side of the fault than in the footwall. Growth faults are common in the Gulf of Mexico and in other areas where the crust is subsiding rapidly or being pulled apart.
3259differential compaction, normal fault, listric fault, subsidence
3260None
3261None
3262--
3263gas migration
32641.n. [Drilling Fluids]
3265A generic term referring to all possible routes for annular gas entry and propagation through and around the cement sheath. Gas migration is also known as annular gas flow.
3266None
3267None
3268annular gas flow
3269--
3270geologist
32711.n. [Geology]
3272A scientist trained in the study of the Earth. In the petroleum industry, geologists perform a wide variety of functions, but typically generate prospects and interpret data such as maps, well logs, outcrops, cuttings, core samples and seismic data.
3273geology, map, outcrop, prospect, well log
3274None
3275None
3276--
3277gooseneck
32781.n. [Drilling]
3279An inverted "U" shaped section of rigid piping normally used as a conduit for high-pressure drilling fluid. In particular, the term is applied to a structure that connects the top of a vertical standpipe running up the side of a derrick or mast to a flexible kelly hose that in turn is connected to another gooseneck between the flexible line and the swivel.
3280drilling fluid, kelly hose, standpipe
3281None
3282None
3283--
3284gooseneck
32852.n. [Well Workover and Intervention]
3286The assembly mounted on a coiled tubing injector head that guides the tubing string as it passes through an arc from the reel into a vertical alignment with the injector-head chains and wellbore. The radius of the guide arch is generally designed to be as large as practicable since the plastic deformation created in the coiled tubing string induces material fatigue in the tube.
3287coiled tubing, injector head
3288None
3289None
3290--
3291guard log
32921.n. [Formation Evaluation]
3293A measurement made by a type of electrode device in which the current flow and hence the measurement is focused in a disk that is concentric with and perpendicular to the sonde. The term usually refers to a Laterolog-3 device. Guard logs may be recorded by either wireline or measurements-while-drilling tools.
3294electrode resistivity
3295None
3296None
3297--
3298gas processing plant
32991.n. [Production Facilities]
3300An installation that processes natural gas to recover natural gas liquids (condensate, natural gasoline and liquefied petroleum gas) and sometimes other substances such as sulfur. A gas processing plant is also known as a natural gas processing plant.
3301condensate liquids, liquefied petroleum gas, natural gas, natural gas liquids, natural gasoline
3302None
3303None
3304--
3305geomagnetic polarity reversal
33061.n. [Geology]
3307The periodic switching of the magnetic north and south poles of the Earth throughout time, probably as a result of movement of fluid within the Earth's core. The onset and duration of the many episodes of reversed polarity have been documented by examining the polarity of magnetic minerals within rocks of different ages from around the world, particularly in basalts or igneous rocks of the oceanic crust. Oceanic basalts record the Earth's magnetic field as they solidify from molten lava symmetrically on each side of the midoceanic ridges. These data have been compiled to create a time scale known as the geomagnetic polarity time scale (GPTS). In the oil field, borehole recordings allow direct correlation to GPTS and well-to-well correlations.
3308geochronology, geologic time scale, geomagnetic polarity time scale, midoceanic ridge, natural remanent magnetism
3309None
3310None
3311--
3312gpts
33131.n. [Geology]
3314A record of the onset and duration of the multitude of episodes of reversal of the Earth's magnetic polarity, or geomagnetic polarity reversals. The GPTS was developed by thorough study of rocks from around the world, during which it was observed that rocks from specific time periods contained magnetic minerals whose orientation was opposite to that of the current magnetic field. By comparing the patterns of magnetic reversals with those of rocks of known age, the approximate ages of rocks can be established. This is particularly useful for basalts of the oceanic crust, which record the Earth's magnetic field as they solidify from molten lava symmetrically about the midocean ridges. The time scale has been accurately extended back to the Upper Jurassic, the age of oldest existing oceanic crust.
3315None
3316None
3317geomagnetic polarity time scale
3318--
3319guide shoe
33201.n. [Drilling]
3321A tapered, often bullet-nosed piece of equipment often found on the bottom of a casing string. The device guides the casing toward the center of the hole and minimizes problems associated with hitting rock ledges or washouts in the wellbore as the casing is lowered into the well. The outer portions of the guide shoe are made from steel, generally matching the casing in size and threads, if not steel grade. The inside (including the taper) is generally made of cement or thermoplastic, since this material must be drilled out if the well is to be deepened beyond the casing point. It differs from a float shoe in that it lacks a check valve.
3322casing point, casing string, check valve, float shoe, washout
3323shoe
3324None
3325--
3326gas separator
33271.n. [Well Completions]
3328A device used to separate entrained gas from production liquids. Surface processing facilities generally use gas separators to render the liquids safe for further processing or disposal. Gas-separation equipment is also used in downhole applications, such as the protection of pumping equipment against gas lock by separating and redirecting free gas at the pump suction or inlet.
3329entrained gas, free gas, gas lock
3330None
3331None
3332--
3333geomagnetic polarity time scale
33341.n. [Geology]
3335A record of the onset and duration of the multitude of episodes of reversal of the Earth's magnetic polarity, or geomagnetic polarity reversals. The GPTS was developed by thorough study of rocks from around the world, during which it was observed that rocks from specific time periods contained magnetic minerals whose orientation was opposite to that of the current magnetic field. By comparing the patterns of magnetic reversals with those of rocks of known age, the approximate ages of rocks can be established. This is particularly useful for basalts of the oceanic crust, which record the Earth's magnetic field as they solidify from molten lava symmetrically about the midocean ridges. The time scale has been accurately extended back to the Upper Jurassic, the age of oldest existing oceanic crust.
3336geochronology, geologic time scale, geomagnetic polarity reversal, midoceanic ridge
3337None
3338GPTS
3339--
3340gr
33411.n. [Formation Evaluation]
3342An abbreviation for gamma ray, usually with reference to the gamma ray log.
3343carbonate gamma ray, gamma ray log, natural gamma ray spectroscopy, potassium, thorium, uranium
3344None
3345None
3346--
3347gumbo
33481.n. [Drilling]
3349A generic term for soft, sticky, swelling clay formations that are frequently encountered in surface holes offshore or in sedimentary basins onshore near seas. This clay fouls drilling tools and plugs piping, both severe problems for drilling crews.
3350native clay
3351None
3352None
3353--
3354gumbo
33552.n. [Drilling Fluids]
3356A nonspecific type of shale that becomes sticky when wet and adheres aggressively to surfaces. It forms mud rings and balls that can plug the annulus, the flowline and shale-shaker screens. Gumbo is likely to contain appreciable amounts of Ca+2 smectite clays. It is dispersed in a water mud, causing rapid accumulations of colloidal solids.
3357colloidal solids, drilling detergent, montmorillonite, shale shaker, smectite clay, water mud
3358None
3359None
3360--
3361gas shale
33621.n. [Shale Gas]
3363Shale that produces natural gas. A shale that is thermally mature enough and has sufficient gas content to produce economic quantities of natural gas.
3364shale gas, unconventional resource
3365None
3366None
3367--
3368geomagnetic secular variation
33691.n. [Geophysics]
3370How Earth’s magnetic field varies with time. These time variations, called secular variations, necessitate periodic updating of magnetic field maps and models. Two types of processes in the Earth’s core produce these variations. One process is related to variations in Earth’s main dipole field, which operate on time scales of hundreds or thousands of years. The other process is related to variations in Earth’s nondipole field, which operate on time scales on the order of tens of years.
3371main magnetic field, dipole field, nondipole field
3372None
3373None
3374--
3375graben
33761.n. [Geology]
3377A relatively low-standing fault block bounded by opposing normal faults. Graben (used as both singular and plural) can form in areas of rifting or extension, where normal faults are the most common type of fault. Between graben are relatively high-standing blocks called horsts. A half-graben is a downdropped block bounded by a normal fault on only one side.
3378aulacogen, horst, normal fault, rift, strike-slip fault
3379None
3380None
3381--
3382gun
33831.n. [Geophysics]
3384Abbreviation for air gun or water gun.An air gun is a source of seismic energy used in acquisition of marine seismic data. This gun releases highly compressed air into water. Air guns are also used in water-filled pits on land as an energy source during acquisition of vertical seismic profiles.A water gun is a source of energy for acquisition of marine seismic data that shoots water from a chamber in the tool into a larger body of water, creating cavitation. The cavity is a vacuum and implodes without creating secondary bubbles. This provides a short time signature and higher resolution than an air-gun source.
3385acquisition, air gun, bubble effect, cavitation, impulsive seismic data, resolution, source, vertical seismic profile, water gun
3386None
3387None
3388--
3389gun
33902.n. [Perforating]
3391A device used to perforate oil and gas wells in preparation for production. Containing several shaped explosive charges, perforating guns are available in a range of sizes and configurations. The diameter of the gun used is typically determined by the presence of wellbore restrictions or limitations imposed by the surface equipment.
3392casing gun, expendable gun, high-shot density gun
3393None
3394None
3395--
3396gas show
33971.n. [Drilling]
3398Gas that rises to the surface, usually detected because it reduces the density of the drilling mud. Gas detectors, which the mud logger monitors, measure combustible gases (methane, ethane, butane and others). The mud logger reports total gas, individual gas components, or both, on the mud log. In extreme cases, gas visibly bubbles out of the mud as it returns to the surface. Because the mud does not circulate to the surface for a considerable time, sometimes lagging several hours after a formation is drilled, a gas show may be representative of what happened in the wellbore hours (or many feet) prior to the current total depth of the well.
3399drilling fluid, total depth
3400None
3401None
3402--
3403geomechanics
34041.n. [Shale Gas]
3405The geologic specialty that deals with understanding how rocks, stresses, pressures, and temperatures interact. This understanding is used to solve oilfield problems, such as optimizing hydraulic fracturing treatments of shale reservoirs. Geomechanics specialists typically work with experts in geophysics, geology, petrophysics, reservoir engineering, drilling engineering, and rock physics to solve geomechanical problems and address production challenges in shale reservoirs.
3406None
3407None
3408None
3409--
3410gradiomanometer
34111.n. [Production Logging]
3412A device for measuring the average density of the fluid at different depths in a completed production or injection well to produce a fluid-density log. Knowing the density of the individual phases allows their holdups to be determined, directly in the case of biphasic flow, and in combination with other measurements for triphasic flow. Introduced in the late 1950s, the gradiomanometer measures the pressure difference between two pressure sensors, placed approximately 2 ft [0.6 m] apart. The pressure difference reflects the average fluid density across the well within that depth interval.The resolution is high, around 0.005 g/cm3, but the accuracy can be affected by a friction effect, a kinetic effect and well deviation. The effect of deviation can be corrected, but the sensitivity to holdup is reduced as the deviation increases until it is zero in a horizontal well.Note: Gradiomanometer is a mark of Schlumberger. It is now a commonly accepted term for a certain tool that measures differential pressure.
3413holdup log, nuclear fluid densimeter, production log
3414None
3415None
3416--
3417gun barrel
34181.n. [Production Facilities]
3419A settling tank used for treating oil. Oil and brine are separated only by gravity segregation forces. The clean oil floats to the top and brine is removed from the bottom of the tank. Gun barrels are found predominantly in older or marginal fields. A gun barrel is also called a wash tank.
3420None
3421None
3422None
3423--
3424gas volume fraction GVF
34251.n. [Production]
3426The ratio of the gas volumetric flow rate to the total volumetric flow rate of all fluids.
3427gas/liquid ratio (GLR), gas/oil ratio (GOR)
3428None
3429None
3430--
3431geometrical factor
34321.n. [Formation Evaluation]
3433The response of a logging measurement as a function of distance from the tool. The geometrical factor can be radial, reflecting the response perpendicular to the tool; vertical, reflecting the response along the tool axis; or two-dimensional, reflecting both. It can also be a differential geometrical factor, which is the contribution to the signal at a particular distance; or integrated, which is the sum of all signals from the tool to a particular distance. The term geometrical factor was introduced for induction logging since it gave a convenient method for computing the reading in a heterogeneous environment. For example, in an invaded formation the log reading, Clog, can be written as:Clog = Gi * Cxo + (1 - Gi) * Ctwhere Gi is the geometrical factor for a diameter of invasion Di, and Cxo and Ct are the conductivities of the invaded zone and the undisturbed zone. A true geometrical factor depends only on the geometry of the volume concerned, which in practice is only true for induction logs at zero conductivity. However, the term has come to be used for other cases and for other measurements even though the geometrical factor depends significantly on formation properties. The correct term for these cases is the pseudogeometrical factor.
3434pseudogeometrical factor, radial response, vertical response
3435None
3436None
3437--
3438grain density
34391.n. [Geology]
3440The density of a rock or mineral with no porosity, also known as matrix density, commonly in units of g/cm3.
3441specific gravity
3442None
3443None
3444--
3445grain density
34462.n. [Formation Evaluation]
3447The density of the grains in a formation or core sample. As used in log and core analysis, the term 'grain' refers to all the solid material in the rock, since, when interpreting the measurements, no effort is made to distinguish grains from other solid material. The grain density of core samples is calculated from the measured dry weight divided by the grain volume. In logs, grain density is calculated from the density log, using an estimate of porosity and knowledge of the fluid content.
3448core plug, porosimeter, routine core analysis, whole core
3449None
3450None
3451--
3452gun clearance
34531.n. [Perforating]
3454The distance between the external surface of the gun assembly and the internal surface of the casing or liner. The gun clearance depends on the position of the gun within the tubular and will vary between phases of shots on any gun unless the gun assembly is centralized. This variation in clearance contributes to variable performance of the perforations. The greater the gun clearance, the smaller the entrance hole-with the effect increasing with depth (pressure).
3455None
3456None
3457None
3458--
3459gas water contact
34601.n. [Geology]
3461A bounding surface in a reservoir above which predominantly gas occurs and below which predominantly water occurs. Gas and water are somewhat miscible, so the contact between gas and water is not necessarily sharp and there is typically a transition zone between 100% gas and 100% water in reservoirs.
3462fluid contact, gas-oil contact, immiscible, oil-water contact, reservoir
3463None
3464GWC
3465--
3466geophone
34671.n. [Geophysics]
3468A device used in surface seismic acquisition, both onshore and on the seabed offshore, that detects ground velocity produced by seismic waves and transforms the motion into electrical impulses. Geophones detect motion in only one direction. Conventional seismic surveys on land use one geophone per receiver location to detect motion in the vertical direction. Three mutually orthogonal geophones are typically used in combination to collect 3C seismic data. Hydrophones, unlike geophones, detect changes in pressure rather than motion.
3469accelerometer, array, cable, channel, check-shot survey, coupling, damping, datum correction, detector, displacement, downhole receiver, dropout, fan shooting, first break, four-component seismic data, geophone interval, ground roll, group interval, hodogram, hydrophone, image, jug hustler, multicomponent seismic data, nest, ocean-bottom cable, random noise, seismograph, spread, three-component seismic data, velocity analysis
3470jug, receiver, seismometer
3471None
3472--
3473granular lcm
34741.n. [Drilling Fluids]
3475A type of lost-circulation material (LCM) that is chunky in shape and prepared in a range of particle sizes. GranularLCMis added tomudand placed downhole to help retard the loss of mud into fractures or highly permeableformations. Ideally, granular LCM should be insoluble and inert to the mud system in which it is used. Examples are ground and sizedlimestoneor marble, wood, nut hulls, Formica, corncobs and cotton hulls. Often, granular, flake and fiber LCMs are mixed together into an LCMpilland pumped into the well next to the loss zone to seal theformationinto which circulation is lost.
3476fiber lost-circulation material, flake lost-circulation material, fluid loss, LCM, lost circulation
3477None
3478None
3479--
3480gunk plug
34811.n. [Drilling Fluids]
3482A slurry that consists of bentonite, cement or polymers mixed into an oil; bentonite in diesel oil is commonly used as a gunk plug. A small batch of the slurry is pumped down a well that has lost circulation to seal the leaky zone. The gunk plug may or may not be squeezed by pressure into the zone. Water downhole interacts with the bentonite, cement or polymers to make a sticky gunk.
3483gunk, gunk squeeze, pill, polymer, slurry
3484diesel-oil plug
3485None
3486--
3487gas well
34881.n. [Well Completions]
3489A well that primarily produces natural gas.
3490natural gas
3491None
3492None
3493--
3494gas well
34952.n. [Well Testing]
3496A producing well with natural gas as the primary commercial product. Most gas wells frequently produce some condensate (natural gas liquids such as propane and butane) and occasionally produce some water.
3497natural gas, natural gas liquids
3498None
3499None
3500--
3501geophysics
35021.n. [Geophysics]
3503The study of the physics of the Earth, especially its electrical, gravitational and magnetic fields and propagation of elastic (seismic) waves within it. Geophysics plays a critical role in the petroleum industry because geophysical data are used by exploration and development personnel to make predictions about the presence, nature and size of subsurface hydrocarbon accumulations.
3504acoustic, gravity, magnetics, seismic, seismic wave
3505None
3506None
3507--
3508granular lost circulation material
35091.n. [Drilling Fluids]
3510A type of lost-circulation material that is chunky in shape and prepared in a range of particle sizes. Granular LCM is added to mud and placed downhole to help retard the loss of mud into fractures or highly permeable formations. Ideally, granular LCM should be insoluble and inert to the mud system in which it is used. Examples are ground and sized limestone or marble, wood, nut hulls, Formica, corncobs and cotton hulls. Often, granular, flake and fiber LCMs are mixed together into an LCM pill and pumped into the well next to the loss zone to seal the formation into which circulation is lost.
3511None
3512None
3513granular LCM, granular lost-circulation material
3514--
3515gwc
35161.n. [Geology]
3517Abbreviation for gas-water contact, abounding surface in a reservoir above which predominantly gas occurs and below which predominantly water occurs. Gas and water are somewhat miscible, so the contact between gas and water is not necessarily sharp and there is typically a transition zone between 100% gas and 100% water in reservoirs.
3518fluid contact, gas-oil contact, immiscible, oil-water contact, reservoir
3519None
3520gas-water contact
3521--
3522gas bearing
35231.adj. [Well Completions]
3524Relating to a formation or interval containing gas, either dissolved in the formation fluid or as free gas. The term is occasionally used to describe wellbore fluids containing dissolved gas.
3525formation fluid, free gas, gas-lift mandrel
3526None
3527None
3528--
3529geopressure
35301.n. [Geology]
3531The pressure within the Earth, or formation pressure. The common oilfield usage, however, is to indicate anomalous subsurface pore pressure that is higher or lower than the normal, predicted hydrostatic pressure for a given depth, or the pressure exerted per unit area by a column of fresh water from sea level to a given depth. Abnormally low pore pressure might occur in areas where fluids have been drained, such as a depleted hydrocarbon reservoir. Abnormally high pore pressure might occur in areas where burial of water-filled sediments by an impermeable sediment such as clay was so rapid that fluids could not escape and the pore pressure increased with deeper burial.
3532abnormal pressure, compaction, formation pressure, geopressure gradient, geopressured, geostatic pressure, hydrostatic pressure, overpressure, pore pressure, reservoir pressure
3533None
3534None
3535--
3536granular lost circulation material
35371.n. [Drilling Fluids]
3538A type of lost-circulation material that is chunky in shape and prepared in a range of particle sizes. Granular LCM is added to mud and placed downhole to help retard the loss of mud into fractures or highly permeable formations. Ideally, granular LCM should be insoluble and inert to the mud system in which it is used. Examples are ground and sized limestone or marble, wood, nut hulls, Formica, corncobs and cotton hulls. Often, granular, flake and fiber LCMs are mixed together into an LCM pill and pumped into the well next to the loss zone to seal the formation into which circulation is lost.
3539fiber lost-circulation material, flake lost-circulation material, fluid loss, LCM, lost circulation
3540None
3541None
3542--
3543gyp mud
35441.n. [Drilling Fluids]
3545A calcium-based water mud system containing gypsum. Gyp mud can be used for drilling shales, but it is also well-suited for drilling gypsum, anhydrite and salt stringers. An advantage of gyp over lime muds is that the pH of gyp mud need not be so high because it contains more soluble Ca+2 to inhibit shale swelling. Gypsum, CaSO4·2H2O, content is measured by an API test, and more can be added as needed. A calcium-tolerant clay deflocculant may be needed to control viscosity. Carboxymethylcellulose (CMC) and starch are used for fluid loss control along with a small amount of prehydrated bentonite.
3546aggregation, API, calcium contamination, calcium mud, calcium sulfate, carboxymethylcellulose, clay-water interaction, drilling fluid, fluid-loss control, lime mud, prehydrated bentonite
3547None
3548None
3549--
3550gas cut mud
35511.n. [Drilling, Drilling Fluids]
3552A drilling fluid (or mud) that has gas (air or natural gas) bubbles in it, resulting in a lower bulk, unpressurized density compared with a mud not cut by gas. The density of gas-cut mud can be measured accurately using a pressurized mud balance. Defoamer chemicals added to the mud or a mechanical vacuum pump degasser can liberate the trapped gas.The derrickman periodically measures mud density and communicates the results to the drilling crew via an intercom, typically reporting something like "9.6 heavy," "10.4," or "13.2 light," indicating more than 9.6 pounds per gallon, 10.4 pounds per gallon, or less than 13.2 pounds per gallon, respectively. Each tenth of a pound per gallon is referred to as a "point" of mud weight. Note that for this low-accuracy measurement, no direct mention of gas cut is made. A gas cut is inferred only if the mud returning to the surface is significantly less dense than it should be. In the case of the mud logger's measurement, "units" of gas (having virtually no absolute meaning) are reported. For the mud logger's measurement, a direct indication of combustible gases is made, with no direct correlation to mud weight.
3553derrickman, drilling fluid
3554air cut mud
3555None
3556--
3557geopressure gradient
35581.n. [Geology]
3559The change in pore pressure per unit depth, typically in units of pounds per square inch per foot (psi/ft) or kilopascals per meter (kPa/m). The geopressure gradient might be described as high or low if it deviates from the normal hydrostatic pressure gradient of 0.433 psi/ft [9.8 kPa/m].
3560abnormal pressure, geopressure, hydrostatic pressure, pore pressure, pressure gradient
3561None
3562None
3563--
3564grapple
35651.n. [Well Workover and Intervention]
3566A generic name given to tools that engage on the outer surface of a tubing string or tool assembly, generally for fishing purposes.
3567None
3568None
3569None
3570--
3571gypsum
35721.n. [Geology]
3573[CaSO472H2O]A highly insoluble sulfate mineral that is the first to precipitate from evaporating seawater. Dehydration of gypsum can produce anhydrite. Fine-grained gypsum is called alabaster.
3574calcium mud, carbon dioxide, evaporite, halite, hydrate, scale, sedimentary
3575None
3576None
3577--
3578h2s
35791.n. [Drilling]
3580[H2S]An extraordinarily poisonous gas with a molecular formula of H2S. At low concentrations, H2S has the odor of rotten eggs, but at higher, lethal concentrations, it is odorless. H2S is hazardous to workers and a few seconds of exposure at relatively low concentrations can be lethal, but exposure to lower concentrations can also be harmful. The effect of H2S depends on duration, frequency and intensity of exposure as well as the susceptibility of the individual. Hydrogen sulfide is a serious and potentially lethal hazard, so awareness, detection and monitoring of H2S is essential. Since hydrogen sulfide gas is present in some subsurface formations, drilling and other operational crews must be prepared to use detection equipment, personal protective equipment, proper training and contingency procedures in H2S-prone areas.Hydrogen sulfide is produced during the decomposition of organic matter and occurs with hydrocarbons in some areas. It enters drilling mud from subsurface formations and can also be generated by sulfate-reducing bacteria in stored muds. H2S can cause sulfide-stress-corrosion cracking of metals. Because it is corrosive, H2S production may require costly special production equipment such as stainless steel tubing.Sulfides can be precipitated harmlessly from water muds or oil muds by treatments with the proper sulfide scavenger. H2S is a weak acid, donating two hydrogen ions in neutralization reactions, forming HS- and S-2 ions. In water or water-base muds, the three sulfide species, H2S and HS- and S-2 ions, are in dynamic equilibrium with water and H+ and OH- ions. The percent distribution among the three sulfide species depends on pH. H2S is dominant at low pH, the HS- ion is dominant at mid-range pH and S2 ions dominate at high pH. In this equilibrium situation, sulfide ions revert to H2S if pH falls. Sulfides in water mud and oil mud can be quantitatively measured with the Garrett Gas Train according to procedures set by API.
3581None
3582None
3583hydrogen sulfide
3584--
3585high pressure air injection
35861.n. [Enhanced Oil Recovery]
3587An enhanced oil recovery process utilizing compressed air that is injected into a reservoir. Oxygen in the gas reacts exothermically with some of the oil, producing highly mobile flue gas. The flue gas advances ahead of the reaction front and achieves an efficient displacement of the in situ oil. Scientists believe that the high displacement efficiency of high-pressure air injection is due to a combination of processes that include immiscible gas displacement, improved miscibility caused by the presence of CO2 in the flue gas, reduction in interfacial tension, oil swelling and reservoir repressurization. The process is typically used for deep, tight, relatively light-oil reservoirs where water injectivity is low.
3588fireflooding
3589None
3590None
3591--
3592horst
35931.n. [Geology]
3594A relatively high-standing area formed by the movement of normal faults that dip away from each other. Horsts occur between low-standing fault blocks called graben. Horsts can form in areas of rifting or extension, where normal faults are the most abundant variety of fault.
3595dip, graben, normal fault, rift
3596None
3597None
3598--
3599hydraulic pumping
36001.n. [Production Testing]
3601An artificial-lift system that operates using a downhole pump. A surface hydraulic pump pressurizes crude oil called power oil, which drives the bottom pump. When a single production string is used, the power oil is pumped down the tubing and a mixture of the formation crude oil and power oil are produced through the casing-tubing annulus. If two production strings are used, the power oil is pumped through one of the pipes, and the mixture of formation crude oil and power oil are produced in the other, parallel pipe.
3602artificial lift, crude oil, power oil, production string
3603None
3604None
3605--
3606haematite
36071.n. [Drilling Fluids]
3608The mineral form of ferric oxide [Fe2O3]. The hematite ore used as a weighting material in drilling muds has a mica-like crystal structure that grinds to particle size suitable for use in drilling fluids. To check for potential wear, an abrasion test is usually run on hematite as a quality control pilot test.
3609high-gravity solids, iron oxide, mud additive, siderite, unweighted mud, water, oil and solids test, weighted mud
3610None
3611None
3612--
3613high pressure high temperature
36141.adj. [Drilling]
3615Pertaining to wells that are hotter or higher pressure than most. The term came into use upon the release of the Cullen report on the Piper Alpha platform disaster in the UK sector of the North Sea, along with the contemporaneous loss of the Ocean Odyssey semisubmersible drilling vessel in Scottish jurisdictional waters. In the UK, HPHT is formally defined as a well having an undisturbed bottomhole temperature of greater than 300oF [149oC] and a pore pressure of at least 0.8 psi/ft (~15.3 lbm/gal) or requiring a BOP with a rating in excess of 10,000 psi [68.95 MPa]. Although the term was coined relatively recently, wells meeting the definition have been safely drilled and completed around the world for decades.
3616HPHT, pore pressure
3617None
3618None
3619--
3620hostile environment
36211.n. [Drilling]
3622A particularly difficult set of well conditions that may detrimentally affect steel, elastomers, mud additives, electronics, or tools and tool components. Such conditions typically include excessive temperatures, the presence of acid gases (H2S, CO2), chlorides, high pressures and, more recently, extreme measured depths.
3623hydrogen sulfide, wireline log
3624None
3625None
3626--
3627hydraulic release tool
36281.n. [Well Workover and Intervention]
3629A downhole tool designed to allow the lower and upper tool string sections to be parted to enable retrieval of the running string. Hydraulic disconnects rely on the application of a predefined pressure through the running string to activate a release mechanism. In some cases, a ball or dart is plugged to block circulation through the tool string and enable the application of the release pressure.
3630hydraulic disconnect, tool string
3631None
3632None
3633--
3634hard rock
36351.n. [Geology]
3636A term applied to hard rocks, or igneous and metamorphic rocks that are distinguished from sedimentary rocks because they are typically more difficult to disaggregate. Well cemented sedimentary rocks are sometimes described as being hard, but are usually called soft rock. The term can be used to differentiate between rocks of interest to the petroleum industry (soft rocks) and rocks of interest to the mining industry (hard rocks).
3637igneous, metamorphic
3638None
3639Antonyms:soft rock
3640--
3641high pressure high temperature filtration test
36421.n. [Drilling Fluids]
3643A test to measure static filtration behavior of water mud or oil mud at elevated temperature, up to about 380°F [193°C] maximum (450°F [227°C] maximum if a special cell is used), usually according to the specifications of API. Although the test can simulate downhole temperature conditions, it does not simulate downhole pressure. Total pressure in a cell should not exceed 700 psi [4900 kPa], and the differential pressure across the filter medium is specified as 500 psi [3500 kPa]. Because these cells are half the size of the ambient filtration area, HPHT filtrate volumes after 30 minutes are doubled.
3644electrical stability test, filter cake, filter press, filter-cake thickness, filtrate volume, fluid-loss control, fluid-loss-control material, geothermal gradient, high-pressure, high-temperature, jar test, particle-plugging apparatus, sintered
3645static filter press
3646Antonyms:low-pressure, low-temperature filtration test
3647--
3648hot lime
36491.n. [Drilling Fluids]
3650A chemical with formula CaO, commonly called quick lime or hot lime. When hydrated with one mole of water, it forms slaked lime, Ca(OH)2. Quick lime is used in preference to slaked lime at oil mud mixing plants because it generates heat when it becomes slaked with water and therefore speeds up emulsification by the reaction to form calcium fatty-acid soap.
3651calcium hydroxide, quick lime
3652None
3653None
3654--
3655hydraulic set
36561.n. [Well Completions]
3657A setting or operating method that uses hydraulic force applied through the tubing or running string to activate a downhole tool. In many cases a drop ball, which lands in a profiled seat, will be used to shift the setting or activation mechanism at predetermined pressures.
3658drop ball
3659None
3660None
3661--
3662hardbanding
36631.n. [Drilling]
3664A process in which a wear-resistant alloy is applied to the tool joints of drillpipe or drill collars to prolong the life of oilfield tubulars. Hardbanding is applied where rotational and axial friction associated with drilling and tripping create excessive abrasive wear between drillstring and casing, or between drillstring and rock.Hard alloy overlays are applied to the points of greatest contact, typically using advanced welding techniques. Typical alloys used in this process range from ultra-wear resistant tungsten carbide, to less abrasive chromium carbide, titanium carbide and borides. Some hardbanding processes take a different approach to reducing wear in tubulars, using materials that achieve a low coefficient of friction used to protect the drillstring from abrasion.
3665tool joint, upset, hardfacing
3666None
3667None
3668--
3669high pressure high temperature viscometer
36701.n. [Drilling Fluids]
3671A type of viscometer generally used in laboratories to test drilling fluids at simulated downhole conditions.
3672API, drilling fluid, oil mud, rheology, shear rate, shear stress, viscosity
3673None
3674HPHT viscometer
3675--
3676hot oiling
36771.n. [Well Completions]
3678Circulation of heated fluid, typically oil, to dissolve or dislodge paraffin deposits from the production tubing. Such deposits tend to occur where a large variation in temperature exists across the producing system.
3679production tubing
3680None
3681None
3682--
3683hydraulic set
36841.n. [Well Completions]
3685A setting or operating method that uses hydraulic force applied through the tubing or running string to activate a downhole tool. In many cases a drop ball, which lands in a profiled seat, will be used to shift the setting or activation mechanism at predetermined pressures.
3686drop ball
3687None
3688None
3689--
3690hardfacing
36911.n. [Production]
3692A metalworking process where harder or tougher material is applied to a weaker base metal. A surface preparation, such as detonation gun or high-velocity oxygen flow, in which an alloy is deposited on a metal surface, usually by weld overlay, to increase abrasion or corrosion resistance.
3693hardbanding
3694None
3695None
3696--
3697high specific gravity solids
36981.n. [Drilling Fluids]
3699Dense solids, such as barite or hematite, which are added to a mud to increase its density, also known as weighting material. The concentration of high-gravity solids in a weighted mud is measured by the mud engineer daily using mud weight, retort data, chloride titration data and other information. Solids are reported as lbm/bbl or vol.%. The specific gravity of water is 1.00, barite is 4.20, and hematite 5.505 g/cm3. Drill solids and other low-gravity solids are normally assumed to be 2.60 g/cm3.
3700material-balance equation, mud report, retort solids, weighting material
3701None
3702Antonyms:LGS, low specific gravity solids, low-specific-gravity solids
3703--
3704hot waterflooding
37051.n. [Heavy Oil, Enhanced Oil Recovery]
3706A method of thermal recovery in which hot water is injected into a reservoir through specially distributed injection wells. Hot waterflooding reduces the viscosity of the crude oil, allowing it to move more easily toward production wells.Hot waterflooding, also known as hot water injection, is typically less effective than a steam-injection process because water has lower heat content than steam. Nevertheless, it is preferable under certain conditions such as formation sensitivity to fresh water.
3707cyclic steam injection, enhanced oil recovery, in-situ combustion, injection well, steamflood
3708None
3709None
3710--
3711hydrocarbon
37121.n. [Geology]
3713A naturally occurring organic compound comprising hydrogen and carbon. Hydrocarbons can be as simple as methane [CH4], but many are highly complex molecules, and can occur as gases, liquids or solids. The molecules can have the shape of chains, branching chains, rings or other structures. Petroleum is a complex mixture of hydrocarbons. The most common hydrocarbons are natural gas, oil and coal.
3714asphalt, bitumen, crude oil, dry gas, field, gas-prone, generation, geochemistry, hydrocarbon kitchen, kerogen, maturity, natural gas, oil field, oil-prone, overmature, pay, play, post-mature, preservation, prospect, reservoir, retrograde condensation, secondary migration, sedimentary basin, source rock, stratigraphic trap, tar sand, wet gas
3715None
3716None
3717--
3718hardness ion
37191.n. [Drilling Fluids]
3720One of three divalent cations that can be present in water, including calcium (Ca+2), magnesium (Mg+2) and ferrous (Fe+2, a form of iron). Hardness ions develop from dissolved minerals, bicarbonate, carbonate, sulfate and chloride. Bicarbonate salts cause temporary hardness, which can be removed by boiling the water and leaving behind a calcium carbonate solid. Mg+2 and Fe+2 ions can be removed by raising the pH (with NaOH or KOH) and then allowing the precipitated Fe(OH)2 and Mg(OH)2 to settle out. Calcium hardness can be removed by adding excess sodium carbonate to precipitate Ca+2 as CaCO3. Hard water can be passed through an ion exchange column where hardness ions are captured on the resin. Removal of hardness is the process called water softening.
3721acrylamide-acrylate polymer, acrylate polymer, calcium carbonate, calcium contamination, calcium mud, calcium test, cation, caustic potash, caustic soda, clay extender, EDTA, hard water, hydration, hydroxyethylcellulose, ion exchange, magnesium test, make-up water, peptized clay, peptizing agent, phosphate salt, PHPA mud, prehydrated bentonite, prehydration, SAPP, sequestering agent, sodium bicarbonate, sodium carbonate, soft water, total hardness test
3722None
3723None
3724--
3725hlb number
37261.n. [Drilling Fluids]
3727A number on the scale of one to 40 according to the HLB system, introduced by Griffin (1949 and 1954). The HLB system is a semi-empirical method to predict what type of surfactant properties a molecular structure will provide. The HLB system is based on the concept that some molecules have hydrophilic groups, other molecules have lipophilic groups, and some have both. Weight percentage of each type of group on a molecule or in a mixture predicts what behavior the molecular structure will exhibit. Water-in-oil emulsifiers have a low HLB numbers, typically around 4. Solubilizing agents have high HLB numbers. Oil-in-water emulsifiers have intermediate to high HLB numbers.Reference:Griffin WC: "Classification of Surface-Active Agents by 'HLB,'" Journal of the Society of Cosmetic Chemists 1 (1949): 311.Reference:Griffin WC: "Calculation of HLB Values of Non-Ionic Surfactants," Journal of the Society of Cosmetic Chemists 5 (1954): 259.
3728coalescence, dispersant, drilling detergent, emulsion, emulsion mud, foaming agent, interfacial tension, lipophilic, oil-in-water emulsion, oil-mud emulsifier, surface tension, surfactant, water-in-oil emulsion, water-mud emulsifier
3729None
3730hydrophile-lipophile balance number
3731--
3732hpht
37331.adj. [Drilling]
3734Pertaining to wells that are hotter or higher pressure than most. The term came into use upon the release of the Cullen report on the Piper Alpha platform disaster in the UK sector of the North Sea, along with the contemporaneous loss of the Ocean Odyssey semisubmersible drilling vessel in Scottish jurisdictional waters. In the UK, HPHT is formally defined as a well having an undisturbed bottomhole temperature of greater than 300oF [149oC] and a pore pressure of at least 0.8 psi/ft (~15.3 lbm/gal) or requiring a BOP with a rating in excess of 10,000 psi [68.95 MPa]. Although the term was coined relatively recently, wells meeting the definition have been safely drilled and completed around the world for decades.
3735None
3736None
3737high-pressure, high-temperature
3738--
3739hydrocarbon indicator
37401.n. [Geophysics]
3741A type of seismic amplitude anomaly, seismic event, or characteristic of seismic data that can occur in a hydrocarbon-bearing reservoir. Although "bright spots," as hydrocarbon indicators are loosely called, can originate in numerous ways, they are not all indicative of the presence of hydrocarbons. Criteria to distinguish true hydrocarbon indicators (sometimes called HCIs) from other types of amplitude anomalies include:amplitude variation with offsetbright or dim spot(s) in amplitude as a result of variations in lithology and pore fluids, sometimes occurring in groups of stacked reservoirschange or reversal in polarity because of velocity changes, also called phasingconformity with local structuresdiffractions that emanate from fluid contactsflat spot that represents a fluid (gas-oil or gas-water) contact, which can also show the downdip limit of the reservoir in some casesgas chimneys above leaking reservoirsshadow zones below the accumulationvelocity push-down because of lower velocities of hydrocarbons than rocksdifference in response between reflected pressure and shear energy.Hydrocarbon indicators are most common in relatively young, unconsolidated siliciclastic sediments with large impedance contrasts across lithologic boundaries, such as those in the Gulf of Mexico and offshore western Africa. An ongoing issue in exploration for hydrocarbon indicators is the difficulty in distinguishing between gas accumulations and water with a low degree of gas saturation ("fizz water").
3742amplitude anomaly, amplitude variation with offset, attribute, diffraction, dim spot, gas chimney, phase, push-down, velocity
3743None
3744bright spot
3745--
3746head
37471.n. [Formation Evaluation]
3748The device that connects the end of the logging cable or the bridle to the top of the logging tool. It contains the weak point, so that when the weak point is broken and the cable removed, the uppermost assembly left in the hole is the head. The top of the head is specially designed to ease fishing of the logging tool, and is also known as the fishing bell.
3749logging tool
3750None
3751fishing bell
3752--
3753holdup
37541.n. [Production Logging]
3755With reference to multiphase flow in pipes, the fraction of a particular fluid present in an interval of pipe. In multiphase flow, each fluid moves at a different speed due to different gravitational forces and other factors, with the heavier phase moving slower, or being more held up, than the lighter phase. The holdup of a particular fluid is not the same as the proportion of the total flow rate due to that fluid, also known as its cut. To determine in-situ flow rates, it is necessary to measure the holdup and velocity of each fluid. Holdup is usually given the symbol y, with the suffixes g, o or w for gas, oil or water.The sum of the holdups of the fluids present is unity. The holdup ratio is the ratio of the holdups of two fluids, and is sometimes used as a parameter to express the phenomenon.
3756flow regime, flow structure, gas-holdup log, holdup log, multiphase flow
3757None
3758None
3759--
3760hpht filtration test
37611.n. [Drilling Fluids]
3762A test to measure static filtration behavior of water mud or oil mud at elevated temperature, up to about 380°F [193°C] maximum (450°F [227°C] maximum if a special cell is used), usually according to the specifications of API. Although the test can simulate downhole temperature conditions, it does not simulate downhole pressure. Total pressure in a cell should not exceed 700 psi [4900 kPa], and the differential pressure across the filter medium is specified as 500 psi [3500 kPa]. Because these cells are half the size of the ambient filtration area, HPHT filtrate volumes after 30 minutes are doubled.
3763None
3764static filter press
3765high-pressure, high-temperature filtration test
3766--
3767hydrochloric acid
37681.n. [Well Workover and Intervention]
3769An acid type commonly used in oil- and gas- well stimulation, especially in carbonate formations. The reaction characteristics of hydrochloric acid enable it to be used in a wide range of treatments, often with chemical additives that enhance its performance or allow greater control of the treatment. Treatments are most commonly conducted with 15% or 28% solutions of hydrochloric acid.
3770None
3771None
3772None
3773--
3774header box
37751.n. [Drilling Fluids]
3776A small box mounted on a shaker screen that takes drilling fluid from the return flow line and distributes it across the surface of the screens via adjustable weirs.
3777drilling fluid, flowline
3778None
3779None
3780--
3781holdup image
37821.n. [Production Logging]
3783A two-dimensional display, using colors or different grey scales, of the holdup around the borehole versus depth. The x-axis of the image shows different segments of the borehole, normally inside a casing, displayed from the top of the hole clockwise around through the bottom and back to the top again. Depth is in the z-axis, while the values of holdup are represented by different colors or changes from black to white.The holdup image is constructed from between four and eight local probe measurements using interpolation within constraints. Images, sometimes called maps, are also made for bubble count and bubble velocity.
3784bubble count, electric probe, local holdup, optical probe, production log, velocity image
3785None
3786None
3787--
3788hpht viscometer
37891.n. [Drilling Fluids]
3790A type of viscometer generally used in laboratories to test drilling fluids at simulated downhole conditions.
3791None
3792None
3793high-pressure, high-temperature viscometer
3794--
3795hydrocyclone
37961.n. [Drilling Fluids]
3797An item of solids-control equipment consisting of an inverted cone, the mud being fed tangentially into the upper (larger diameter) part. The resulting spinning effect forces solids to the wall of the device and they exit from the bottom (apex) of the cone, while the cleaned liquid exits at the top. Hydrocyclones are classified by the size of the cone as either desanders (typically 12 inches in diameter) or desilters (4 to 6 inches in diameter) and will separate particles in the medium-, fine- and ultrafine-size ranges. The efficiency of hydrocyclones is poor in viscous weighted muds and many units are being replaced by more efficient, high-speed shakers.
3798bypass, centrifuge, closed mud system, hydrocycloning
3799None
3800None
3801--
3802heater
38031.n. [Production Facilities]
3804Equipment that transfers heat to the produced gas stream.Heaters are especially used when producing natural gas or condensate to avoid the formation of ice and gas hydrates. These solids can plug the wellhead, chokes and flowlines.The production of natural gas is usually accompanied by water vapor. As this mixture is produced, it cools down on its way to the surface and also when the mixture passes through a surface production choke. This reduction of fluid temperature can favor the formation of gas hydrates if heaters are not used.Heaters may also be used to heat emulsions before further treating procedures or when producing crude oil in cold weather to prevent freezing of oil or formation of paraffin accumulations.
3805choke, emulsion, flowline, hydrate, natural gas
3806None
3807None
3808--
3809holdup log
38101.n. [Production Logging]
3811A record of the fractions of different fluids present at different depths in the borehole. Various techniques are used to measure these fractions. The earliest techniques measured the fluid density, using a gradiomanometer or a nuclear fluid densimeter, or the dielectric properties, as in the capacitance or water-cut meter.While these techniques were satisfactory in near-vertical wells with two-phase flow, they were often found to be inadequate in highly deviated and horizontal wells, where flow structures are complex. More recent developments are based on the use of multiple local probes to detect bubbles of gas, oil or water, and on a combination of nuclear techniques usually known as three-phase holdup.
3812flow structure, gas-holdup log, nuclear fluid densimeter, production log, two-phase flow, water-cut meter
3813None
3814None
3815--
3816hpu
38171.n. [Production, Well Workover and Intervention]
3818A device used in a hydraulic system to store energy or, in some applications, dampen pressure fluctuations. Energy is stored by compressing a precharged gas bladder with hydraulic fluid from the operating or charging system. Depending on the fluid volume and precharge pressure of the accumulator, a limited amount of hydraulic energy is then available independent of any other power source. Well pressure-control systems typically incorporate sufficient accumulator capacity to enable the blowout preventer to be operated with all other power shut down.
3819None
3820None
3821hydraulic power unit
3822--
3823hydrocycloning
38241.vb. [Drilling Fluids]
3825Using a hydrocyclone, an item of solids-control equipment consisting of an inverted cone, the mud being fed tangentially into the upper (larger diameter) part. The resulting spinning effect forces solids to the wall of the device and they exit from the bottom (apex) of the cone, while the cleaned liquid exits at the top. Hydrocyclones are classified by the size of the cone as either desanders (typically 12 inches in diameter) or desilters (4 to 6 inches in diameter) and will separate particles in the medium-, fine- and ultrafine-size ranges. The efficiency of hydrocyclones is poor in viscous weighted muds and many units are being replaced by more efficient, high-speed shakers.
3826bypass, centrifuge, closed mud system
3827None
3828None
3829--
3830heavy oil
38311.n. [Heavy Oil, Enhanced Oil Recovery]
3832Crude oil with high viscosity (typically above 10 cp), and high specific gravity. The API classifies heavy oil as crudes with a gravity below 22.3° API. In addition to high viscosity and high specific gravity, heavy oils typically have low hydrogen-to-carbon ratios, high asphaltene, sulfur, nitrogen, and heavy-metal content, as well as higher acid numbers.
3833crude oil
3834viscous oil
3835None
3836--
3837holdup map
38381.n. [Production Logging]
3839A two-dimensional display, using colors or different grey scales, of the holdup around the borehole versus depth. The x-axis of the image shows different segments of the borehole, normally inside a casing, displayed from the top of the hole clockwise around through the bottom and back to the top again. Depth is in the z-axis, while the values of holdup are represented by different colors or changes from black to white.The holdup image is constructed from between four and eight local probe measurements using interpolation within constraints. Images, sometimes called maps, are also made for bubble count and bubble velocity.
3840electric probe, local holdup, optical probe, production log, velocity image
3841None
3842None
3843--
3844hti
38451.n. [Geophysics]
3846Abbreviation for horizontal transverse isotropy. Transverse isotropy that has a horizontal axis of rotational symmetry. In vertically fractured rocks, properties are uniform in vertical planes parallel to the fractures, but vary in the direction perpendicular to the fractures and across the fractures.
3847None
3848None
3849horizontal transverse isotropy, TIH
3850--
3851hydrofluoric acid
38521.n. [Enhanced Oil Recovery]
3853A poisonous liquid acid composed of hydrogen and fluorine. Hydrofluoric acid [HF] is used primarily because it is the only common, inexpensive mineral acid that can dissolve siliceous minerals. HF is typically mixed with hydrochloric acid [HCl] or organic acid to keep the pH low when it spends, thereby preventing detrimental precipitates. These mixtures, also called mud acids, are considered the main fluid in a sandstone acid treatment because they remove formation damage.Hydrofluoric acid should not be used in sandstone formations with high carbonate content because of the high risk of calcium fluoride precipitation [CaF2].
3854fluoboric acid, matrix stimulation, precipitate
3855None
3856None
3857--
3858heavyweight drillpipe
38591.n. [Drilling]
3860A type of drillpipe whose walls are thicker and collars are longer than conventional drillpipe. HWDP tends to be stronger and has higher tensile strength than conventional drillpipe, so it is placed near the top of a long drillstring for additional support.
3861collar, drillstring
3862None
3863HWDP
3864--
3865holdup meter
38661.n. [Production Logging]
3867A device for determining the water holdup in a producing well by measuring the capacitance or impedance of the fluid. The holdup meter is used to produce a capacitance log. Since water has a high dielectric constant, and hence capacitance, it can be distinguished from oil or gas. The meter is a coaxial capacitor, with fluid flowing between a central probe and an external cage that act as electrodes. The meter has often been combined with a packer flowmeter or a diverter flowmeter, so that all the fluids in the well pass through the meter.
3868capacitance log, dielectric constant, diverter flowmeter, holdup log, packer flowmeter, production log
3869capacitance meter
3870None
3871--
3872hwdp
38731.n. [Drilling]
3874A type of drillpipe whose walls are thicker and collars are longer than conventional drillpipe. HWDP tends to be stronger and has higher tensile strength than conventional drillpipe, so it is placed near the top of a long drillstring for additional support.
3875None
3876None
3877heavyweight drillpipe
3878--
3879hydrofluoric hydrochloric acid
38801.n. [Well Completions, Well Workover and Intervention]
3881A mixture of hydrofluoric acid [HF] and hydrochloric acid [HCl] or organic acid used as the main fluid in a sandstone matrix treatment. Hydrochloric acid or organic acid is mixed with HF to keep the pH low when it spends, thereby preventing detrimental precipitates. The name mud acid was given to these mixtures because they were originally developed to treat damage from siliceous drilling muds.
3882fluoboric acid, hydrofluoric acid, organic acid
3883None
3884None
3885--
3886hec
38871.n. [Drilling Fluids]
3888A nonionic cellulose derivative with hydroxyethyl groups attached to the polymer structure. HEC is used as a viscosifier in brines and saline fracturing fluids, workover fluids, completion fluids and drill-in fluids. It gives pseudoplastic rheology but essentially no gel strength development. HEC offers little fluid-loss control, other than its rheological effects. HEC is seldom used in drilling fluids. Cellulose fibers are reacted with caustic soda and ethylene oxide to form HEC. Hydroxyethyl groups attach to the OH groups of the polysaccharide structure by ether linkages. A high degree of substitution (from 1.5 to 2.5 out of 3 maximum) gives HEC superior solubility in water and various brines. Being nonionic, it is not precipitated by hardness ions and disperses well at high salinity. HEC is not degraded by common bacteria.
3889None
3890None
3891hydroxyethylcellulose
3892--
3893hole cleaning
38941.n. [Drilling Fluids]
3895The ability of a circulating drilling fluid to transport rock fragments out of a wellbore. Carrying capacity is an essential function of a drilling fluid, synonymous with hole-cleaning capacity and cuttings lifting. Carrying capacity is determined principally by the annular velocity, hole angle and flow profile of the drilling fluid, but is also affected by mud weight, cuttings size and pipe position and movement.
3896Brookfield viscometer, cuttings, rheology, XC polymer
3897carrying capacity, cuttings lifting
3898None
3899--
3900hybrid scale
39011.n. [Formation Evaluation]
3902An early scale used for the presentation of resistivity logs. The scale has two parts, equally divided about a midpoint. The left part is linear in resistivity, for example 0 on the left edge to 50 ohm-m at the midpoint. The right part is linear in conductivity, from 0 on the right to 1/50 = 20 mS/m at the midpoint. In this way, it was possible to display the complete range of resistivity in one track. It was subsequently replaced by the logarithmic scale.
3903resistivity log
3904None
3905None
3906--
3907hydrofluoric hydrochloric acid
39081.n. [Well Completions, Well Workover and Intervention]
3909A mixture of hydrofluoric acid [HF] and hydrochloric acid [HCl] or organic acid used as the main fluid in a sandstone matrix treatment. Hydrochloric acid or organic acid is mixed with HF to keep the pH low when it spends, thereby preventing detrimental precipitates. The name mud acid was given to these mixtures because they were originally developed to treat damage from siliceous drilling muds.
3910fluoboric acid, hydrofluoric acid, organic acid
3911None
3912None
3913--
3914hematite
39151.n. [Drilling Fluids]
3916The mineral form of ferric oxide [Fe2O3]. The hematite ore used as a weighting material in drilling muds has a mica-like crystal structure that grinds to particle size suitable for use in drilling fluids. To check for potential wear, an abrasion test is usually run on hematite as a quality control pilot test.
3917high-gravity solids, iron oxide, mud additive, siderite, unweighted mud, water, oil and solids test, weighted mud
3918None
3919None
3920--
3921homogeneous formation
39221.n. [Well Testing]
3923Formation with rock properties that do not change with location in the reservoir. This ideal never actually occurs, but many formations are close enough to this situation that they can be considered homogeneous. Most of the models used for pressure-transient analysis assume the reservoir is homogeneous.
3924isotropic formation, pressure-transient analysis
3925None
3926Antonyms:heterogeneous formation
3927--
3928hydrate
39291.vb. [Drilling Fluids]
3930For ahygroscopicmaterial such as aclayorpolymer to absorb water. Hydration is the first stage of clay-water (or polymer-water) interaction. When drybentoniteis stirred into water, hydration is observed as swelling.
3931clay-water interaction, colloid, hardness ion, hydration, hydrophilic, inhibit, inhibitive mud, montmorillonite, prehydrated bentonite, prehydration, seawater mud, soft water, XC polymer
3932None
3933None
3934--
3935hydrate
39362.n. [Geology]
3937An unusual occurrence of hydrocarbon in which molecules of natural gas, typically methane, are trapped in ice molecules. More generally, hydrates are compounds in which gas molecules are trapped within a crystal structure. Hydrates form in cold climates, such as permafrost zones and in deep water. To date, economic liberation of hydrocarbon gases from hydrates has not occurred, but hydrates contain quantities of hydrocarbons that could be of great economic significance. Hydrates can affect seismic data by creating a reflection or multiple.
3938methane hydrate, natural gas
3939clathrate, gas hydrate
3940None
3941--
3942hydrate
39433.vt. [Geology]
3944To cause the incorporation of water into the atomic structure of a mineral.
3945None
3946None
3947None
3948--
3949hydrate
39504.n. [Production Testing]
3951Compounds or complex ions that are formed by the union of water with other substances. Hydrates can form in pipelines and in gas gathering, compression and transmission facilities at reduced temperatures and high pressures. Once hydrates are formed, they can plug the pipelines and significantly affect production operations.
3952None
3953clathrate
3954None
3955--
3956hydrate
39575.n. [Geology]
3958A chemical combination of water and another substance. Gypsum is a hydrate mineral. Its anhydrous equivalent is anhydrite.
3959gypsum, hydration, mineral
3960None
3961None
3962--
3963hydrogen embrittlement
39641.n. [Enhanced Oil Recovery]
3965The process whereby hydrogen causes steel components to become less resistant to breakage and generally much weaker in tensile strength. Whileembrittlementhas many causes, in the oilfieldit is usually the result of exposure to gaseous or liquidhydrogen sulfide[H2S].On a molecular level, hydrogen ions work their way between the grain boundaries of the steel, where hydrogen ions recombine into molecular hydrogen [H2], taking up more space and weakening the bonds between the grains. The formation of molecular hydrogen can cause sudden metal failure due to cracking when the metal is subjected to tensile stress.This type of hydrogen-induced failure is produced when hydrogen atoms enter high strength steels. The failures due to hydrogen embrittlement normally have a period where no damage is observed, which is called incubation, followed by a sudden catastrophic failure.Hydrogen embrittlement is also called acid brittleness.
3966corrosion control, hydrogen induced failures, tensile strength
3967None
3968None
3969--
3970herschel bulkley fluid
39711.n. [Drilling Fluids]
3972A fluid described by a three-parameter rheological model. A Herschel-Bulkley fluid can be described mathematically as follows:τ = τ0 + k(γ)n,whereτ = shear stressτ0 = yield stressk = consistency factorγ = shear raten = flow index, a power law exponent.The Herschel-Bulkley equation is preferred to power law or Bingham relationships because it results in more accurate models of rheological behavior when adequate experimental data are available. The yield stress is normally taken as the 3 rpm reading, with the n and K values then calculated from the 600 or 300 rpm values or graphically.Reference: Hemphill T, Campos W and Pilehvari A: "Yield-Power Law Model More Accurately Predicts Mud Rheology," Oil &amp; Gas Journal 91, no. 34 (August 23, 1993): 45–50.
3973None
3974None
3975Herschel-Bulkley fluid
3976--
3977hook load
39781.n. [Drilling]
3979The total force pulling down on the hook. This total force includes the weight of the drillstring in air, the drill collars and any ancillary equipment, reduced by any force that tends to reduce that weight. Some forces that might reduce the weight include friction along the wellbore wall (especially in deviated wells) and, importantly, buoyant forces on the drillstring caused by its immersion in drilling fluid. If the BOPs are closed, any pressure in the wellbore acting on the cross-sectional area of the drillstring in the BOPs will also exert an upward force.
3980blowout preventer, deviated hole, drilling fluid
3981None
3982None
3983--
3984hydraulic bypass
39851.n. [Well Workover and Intervention]
3986A design feature on packers and similar downhole tools that occupy a large proportion of the drift diameter of the wellbore. When running and retrieving such tools, the hydraulic bypass allows the wellbore fluid to flow through part of the tool assembly to reduce the forces applied to the tool and reduce any damaging swab or surge effect on the reservoir formation.
3987packer
3988None
3989None
3990--
3991hydrogen probe
39921.n. [Enhanced Oil Recovery]
3993A corrosion test instrument mainly used in sour systems (for example, hydrogen sulfide or other sulfide rich environments) to determine qualitatively or semiquantitatively the corrosion of a structure.A hydrogen probe is also called a hydrogen patch probe.
3994sour corrosion
3995None
3996None
3997--
3998herschel bulkley fluid
39991.n. [Drilling Fluids]
4000A fluid described by a three-parameter rheological model. A Herschel-Bulkley fluid can be described mathematically as follows:τ = τ0 + k(γ)n,whereτ = shear stressτ0 = yield stressk = consistency factorγ = shear raten = flow index, a power law exponent.The Herschel-Bulkley equation is preferred to power law or Bingham relationships because it results in more accurate models of rheological behavior when adequate experimental data are available. The yield stress is normally taken as the 3 rpm reading, with the n and K values then calculated from the 600 or 300 rpm values or graphically.Reference: Hemphill T, Campos W and Pilehvari A: "Yield-Power Law Model More Accurately Predicts Mud Rheology," Oil &amp; Gas Journal 91, no. 34 (August 23, 1993): 45–50.
4001Bingham plastic model, direct-indicating viscometer, gel strength, Newtonian fluid, non-Newtonian fluid, plastic fluid, power-law fluid, pseudoplastic, rheological property, rheology, shear rate, shear stress, viscosity, yield stress
4002None
4003None
4004--
4005hookwall packer
40061.n. [Well Completions]
4007A type of packer than utilizes an assembly of friction blocks and slips to set and anchor the packer on the casing or liner wall. Hookwall packers generally are run on tubing or drillpipe and typically require some rotation of the packer assembly to activate or set the packer slips. Subsequent application of tension or compression, depending on packer design, will set the packer elements.
4008block, packer
4009None
4010None
4011--
4012hydraulic centralizer
40131.n. [Well Workover and Intervention]
4014A type of tool-string centralizer, generally used in through-tubing applications, that employs hydraulic force to energize the centralizer arms or bows. Through-tubing operations sometimes require the tool string to be centralized within the casing or liner below the tubing. The relatively large expansion required for this is not generally within the operating range of conventional centralizer models.
4015tool string
4016None
4017None
4018--
4019hydrogen sulfide
40201.n. [Drilling, Drilling Fluids, Production Facilities, Well Testing, Well Workover and Intervention, Well Completions]
4021[H2S]An extraordinarily poisonous gas with a molecular formula of H2S. At low concentrations, H2S has the odor of rotten eggs, but at higher, lethal concentrations, it is odorless. H2S is hazardous to workers and a few seconds of exposure at relatively low concentrations can be lethal, but exposure to lower concentrations can also be harmful. The effect of H2S depends on duration, frequency and intensity of exposure as well as the susceptibility of the individual.Hydrogen sulfide is a serious and potentially lethal hazard, so awareness, detection and monitoring of H2S is essential. Since hydrogen sulfide gas is present in some subsurface formations, drilling and other operational crews must be prepared to use detection equipment, personal protective equipment, proper training and contingency procedures in H2S-prone areas.Hydrogen sulfide is produced during the decomposition of organic matter and occurs with hydrocarbons in some areas. It enters drilling mud from subsurface formations and can also be generated by sulfate-reducing bacteria in stored muds. H2S can cause sulfide-stress-corrosion cracking of metals. Because it is corrosive, H2S production may require costly special production equipment such as stainless steel tubing.Sulfides can be precipitated harmlessly from water muds or oil muds by treatments with the proper sulfide scavenger. H2S is a weak acid, donating two hydrogen ions in neutralization reactions, forming HS- and S-2 ions. In water or water-base muds, the three sulfide species, H2S and HS- and S-2 ions, are in dynamic equilibrium with water and H+ and OH- ions. The percent distribution among the three sulfide species depends on pH. H2S is dominant at low pH, the HS- ion is dominant at mid-range pH and S2 ions dominate at high pH. In this equilibrium situation, sulfide ions revert to H2S if pH falls. Sulfides in water mud and oil mud can be quantitatively measured with the Garrett Gas Train according to procedures set by API.
4022corrosion coupon, Garrett Gas Train, hydrocarbon, natural gas, sour, sweet
4023None
4024H2S
4025--
4026hesitation squeeze
40271.n. [Well Workover and Intervention]
4028A technique used in squeeze cementing whereby a portion of the slurry is pumped, then pumping stops to expose the slurry to differential pressure against the zone of interest in stages over a period from several minutes to several hours. This pressure, higher than necessary for fluid movement, is applied to force the cement slurry into the area requiring repair. This staged procedure is repeated until all the slurry has been pumped or until no further slurry can be placed into the treatment zone. The cement remaining in the zone forms an effective hydraulic seal with a high compressive strength.
4029None
4030None
4031None
4032--
4033hopper
40341.n. [Drilling]
4035In general, a funnel-shaped device used to transfer products. The hopper is often at the bottom of any container for holding or using bulk products, especially drilling fluid additives and cementing material.
4036None
4037None
4038None
4039--
4040hopper
40412.n. [Drilling]
4042The device used to facilitate the addition of drilling fluid additives to the whole mud system. While several types of hoppers exist, they generally have a high velocity stream of mud going through them and a means of mixing either dry or liquid mud additives into the whole mud stream. The resultant mixed mud is then circulated back into the surface mud system. A hopper is generally used to introduce relatively small quantities of additives to the mud system.
4043None
4044None
4045None
4046--
4047hydraulic disconnect
40481.n. [Well Workover and Intervention]
4049A downhole tool designed to allow the lower and upper tool string sections to be parted to enable retrieval of the running string. Hydraulic disconnects rely on the application of a predefined pressure through the running string to activate a release mechanism. In some cases, a ball or dart is plugged to block circulation through the tool string and enable the application of the release pressure.
4050hydraulic release tool, tool string
4051None
4052None
4053--
4054hydrophile lipophile balance number
40551.n. [Enhanced Oil Recovery, Drilling Fluids]
4056A number on the scale of one to 40 according to the HLB system, introduced by Griffin (1949 and 1954). The HLB system is a semi-empirical method to predict what type of surfactant properties a molecular structure will provide. The HLB system is based on the concept that some molecules have hydrophilic groups, other molecules have lipophilic groups, and some have both. Weight percentage of each type of group on a molecule or in a mixture predicts what behavior the molecular structure will exhibit. Water-in-oil emulsifiers have a low HLB numbers, typically around 4. Solubilizing agents have high HLB numbers. Oil-in-water emulsifiers have intermediate to high HLB numbers.Reference:Griffin WC: "Classification of Surface-Active Agents by 'HLB,'" Journal of the Society of Cosmetic Chemists 1 (1949): 311.Reference:Griffin WC: "Calculation of HLB Values of Non-Ionic Surfactants," Journal of the Society of Cosmetic Chemists 5 (1954): 259.
4057emulsion, emulsion mud, oil mud, oil-mud emulsifier, water-in-oil emulsion, water-mud emulsifier
4058None
4059HLB number
4060--
4061heterogeneous formation
40621.n. [Well Testing]
4063Formation with rock properties changing with location in the reservoir. Some naturally fractured reservoirs are heterogeneous formations.
4064None
4065None
4066Antonyms:homogeneous formation
4067--
4068horizon
40691.n. [Geology]
4070An informal term used to denote a surface in or of rock, or a distinctive layer of rock that might be represented by a reflection in seismic data. The term is often used incorrectly to describe a zone from which hydrocarbons are produced.
4071hardground
4072None
4073None
4074--
4075horizon
40762.n. [Geophysics]
4077An interface that might be represented by a seismic reflection, such as the contact between two bodies of rock having different seismic velocity, density, porosity, fluid content or all of those.
4078fluid contact, lithologic contact, reflection
4079None
4080None
4081--
4082hydraulic fracture monitoring
40831.n. [Shale Gas, Well Completions]
4084A technique to track the propagation of a hydraulic fracture as it advances through a formation. Microseisms are detected, located, and displayed in time for scientists and engineers to approximate the location and propagation of the hydraulic fracture. Software provides modeling, survey design, microseismic detection and location, uncertainty analysis, data integration, and visualization for interpretation. Computer imagery is used to monitor the activity in 3D space relative to the location of the fracturing treatment. The monitored activities are animated to show progressive fracture growth and the subsurface response to pumping variations. When displayed in real time, the microseismic activity allows one to make changes to the stimulation design to ensure optimal reservoir contact. Also known as microseismic monitoring, this technique delivers information about the effectiveness of the stimulation of a reservoir that can be used to enhance reservoir development in shale gas completions.
4085None
4086None
4087None
4088--
4089hydrostatic bailer
40901.n. [Well Workover and Intervention]
4091A slickline tool generally used for the removal of sand or similar small particles around the fishing necks of downhole tools or equipment. The hydrostatic bailer incorporates a sealed atmospheric chamber and a shear pin, or similar activation mechanism, to allow communication with the wellbore. When the tool is activated, there is a fluid surge into the atmosphere as the pressure is equalized. A shroud arrangement at the base of the tool contains and directs the fluid surge to dislodge and capture any debris in the area.
4092fishing neck, shear pin
4093sand bailer
4094None
4095--
4096hf
40971.n. [Well Workover and Intervention, Well Completions]
4098A poisonous liquid acid composed of hydrogen and fluorine. Hydrofluoric acid [HF] is used primarily because it is the only common, inexpensive mineral acid that can dissolve siliceous minerals. HF is typically mixed with hydrochloric acid [HCl] or organic acid to keep the pH low when it spends, thereby preventing detrimental precipitates. These mixtures, also called mud acids, are considered the main fluid in a sandstone acid treatment because they remove formation damage.Hydrofluoric acid should not be used in sandstone formations with high carbonate content because of the high risk of calcium fluoride precipitation [CaF2].
4099fluoboric acid, matrix stimulation, precipitate
4100None
4101None
4102--
4103horizon slice
41041.n. [Geophysics]
4105A map view of a particular reflection in a 3D seismic survey, as opposed to a horizontal (depth) slice or at a given time (a time slice). Slices are convenient displays for visual inspection of seismic attributes, especially amplitude.
4106attribute, three-dimensional survey, time slice
4107None
4108None
4109--
4110hydraulic fracturing
41111.n. [Shale Gas, Well Completions, Well Workover and Intervention]
4112A stimulation treatment routinely performed on oil and gas wells in low-permeability reservoirs. Specially engineered fluids are pumped at high pressure and rate into the reservoir interval to be treated, causing a vertical fracture to open. The wings of the fracture extend away from the wellbore in opposing directions according to the natural stresses within the formation. Proppant, such as grains of sand of a particular size, is mixed with the treatment fluid to keep the fracture open when the treatment is complete. Hydraulic fracturing creates high-conductivity communication with a large area of formation and bypasses any damage that may exist in the near-wellbore area.
4113treatment fluid
4114None
4115None
4116--
4117hydrostatic head
41181.n. [Geology]
4119The height of a column of freshwater that exerts pressure at a given depth. Some authors use the term synonymously with hydrostatic pressure.
4120fresh water, hydraulic head, hydrostatic pressure, sag
4121None
4122None
4123--
4124hydrostatic head
41252.n. [Drilling]
4126The vertical height of a fluid column, regardless of the length or other dimensions of that fluid column. For example, a deviated wellbore has a longer length than vertical depth. The hydrostatic head at any point in that wellbore is not a function of its measured depth (MD) along the wellbore axis, but rather its vertical distance or true vertical depth (TVD) to the surface. The term "head" or "hydrostatic head" is also commonly used as a measure of the output of centrifugal pumps, usually expressed in "feet of head" or psi. Since this type of pump is a centrifugal (or "velocity") device, the capability of the pump as expressed in feet of head is independent of the density of the fluid being pumped. For example, if a pump is rated as producing "sixty feet of head," it will pump a column of fluid up an open-ended vertical pipe until the top of the liquid is 60 ft [18 m] above the discharge of the pump, regardless of the density of the liquid being pumped.
4127circulation loss, deviated hole, hydrostatic pressure, measured depth, true vertical depth
4128None
4129None
4130--
4131hgs
41321.n. [Drilling Fluids]
4133Dense solids, such as barite or hematite, which are added to a mud to increase its density, also known as weighting material. The concentration of high-gravity solids in a weighted mud is measured by the mud engineer daily using mud weight, retort data, chloride titration data and other information. Solids are reported as lbm/bbl or vol.%. The specific gravity of water is 1.00, barite is 4.20, and hematite 5.505 g/cm3. Drill solids and other low-gravity solids are normally assumed to be 2.60 g/cm3.
4134material-balance equation, mud report, retort solids, weighting material
4135None
4136Antonyms:LGS, low specific gravity solids, low-specific-gravity solids
4137--
4138horizontal drilling
41391.n. [Drilling]
4140A subset of the more general term "directional drilling," used where the departure of the wellbore from vertical exceeds about 80 degrees. Note that some horizontal wells are designed such that after reaching true 90-degree horizontal, the wellbore may actually start drilling upward. In such cases, the angle past 90 degrees is continued, as in 95 degrees, rather than reporting it as deviation from vertical, which would then be 85 degrees. Because a horizontal well typically penetrates a greater length of the reservoir, it can offer significant production improvement over a vertical well.
4141directional drilling, directional well
4142None
4143None
4144--
4145horizontal drilling
41462.n. [Shale Gas]
4147The intentional deviation of a wellbore from the path it would naturally take to a horizontal trajectory. Horizontal lateral sections can be designed to intersect natural fractures or simply to contact more of the productive formation. Horizontal drilling is accomplished through the use of whipstocks, bottomhole assembly (BHA) configurations, instruments to measure the path of the wellbore in three-dimensional space, data links to communicate measurements taken downhole to the surface, mud motors and special BHA components, including rotary steerable systems and drill bits. While many techniques can accomplish this, the general concept is simple: Direct the bit in the direction that one wants to drill. By placing a bend near the bit in a downhole steerable mud motor, the bend points the bit in a direction different from the axis of the wellbore when the entire drillstring is not rotating. By pumping mud through the mud motor, the bit turns while the drillstring does not rotate, allowing the bit to drill in the direction it points. When a particular wellbore direction is achieved, that direction may be maintained by rotating the entire drillstring (including the bent section) such that the bit does not drill in a single direction off the wellbore axis. Instead, the bit sweeps around and its net direction coincides with the existing wellbore. Rotary steerable tools allow steering while rotating, usually with higher rates of penetration and ultimately smoother boreholes. Horizontal drilling is common in shale reservoirs because it allows drillers to place the borehole in contact with the most productive reservoir rock.
4148None
4149None
4150None
4151--
4152hydraulic horsepower
41531.n. [Drilling]
4154A measure of the energy per unit of time that is being expended across the bit nozzles. It is commonly calculated with the equation HHP=P*Q/1714, where P stands for pressure in pounds per square in., Q stands for flow rate in gallons per minute, and 1714 is a conversion factor necessary to yield HHP in terms of horsepower. Bit manufacturers often recommend that fluid hydraulics energy across the bit nozzles be in a particular HHP range, for example 2.0 to 7.0 HHP, to ensure adequate bit tooth and bottom-of-hole cleaning (the minimum HHP) and to avoid premature erosion of the bit itself (the maximum HHP).
4155bit nozzle, mud motor, positive-displacement pump
4156None
4157HHP
4158--
4159hydraulic horsepower
41602.n. [Drilling]
4161The power of a <a href="Display.cfm?Term=positive%20displacement%20pump">positive <a href="Display.cfm?Term=displacement">displacement pump. HHP is important for mud pumps and cement pumps.
4162None
4163None
4164None
4165--
4166hydrostatic pressure
41671.n. [Geology]
4168The normal, predicted pressure for a given depth, or the pressure exerted per unit area by a column of freshwater from sea level to a given depth. Abnormally low pressure might occur in areas where fluids have been drained, such as a depleted hydrocarbon reservoir. Abnormally high pressure might occur in areas where burial of water-filled sediments by an impermeable sediment such as clay was so rapid that fluids could not escape and the pore pressure increased with deeper burial.
4169abnormal pressure, absolute pressure, formation pressure, fresh water, geopressure, geopressure gradient, hydraulic head, hydrostatic head, normal pressure, overpressure, pore pressure, reservoir pressure, underpressure
4170None
4171None
4172--
4173hydrostatic pressure
41742.n. [Drilling]
4175The force per unit area caused by a column of fluid. In US oilfield units, this is calculated using the equation: P=MW*Depth*0.052, where MW is the drilling fluid density in pounds per gallon, Depth is the true vertical depth or "head" in feet, and 0.052 is a unit conversion factor chosen such that P results in units of pounds per square in. (psi).
4176circulation loss, hydrostatic head, kick, shut-in bottomhole pressure, shut-in pressure, true vertical depth
4177None
4178None
4179--
4180hydrostatic pressure
41813.n. [Drilling Fluids]
4182The pressure at any point in a column of fluid caused by the weight of fluid above that point. Controlling the hydrostatic pressure of a mud column is a critical part of mud engineering. Mud weight must be monitored and adjusted to always stay within the limits imposed by the drilling situation. Sufficient hydrostatic pressure (mud weight) is necessary to prevent an influx of fluids from downhole, but excessive pressure must also be avoided to prevent creation of hydraulic fractures in the formation, which would cause lost circulation. Hydrostatic pressure is calculated from mud weight and true vertical depth as follows:Hydrostatic pressure, psi = 0.052 x Mud Weight, lbm/gal x True Vertical Depth, ft. (To convert to SI units, 1.0 psi = 6.9 kPa.)
4183equivalent circulating density, kill-weight fluid, lost circulation, mud balance, mud program, mud weight, pressurized mud balance, spotting fluid
4184None
4185None
4186--
4187hhp
41881.n. [Drilling]
4189A measure of the energy per unit of time that is being expended across the bit nozzles. It is commonly calculated with the equation HHP=P*Q/1714, where P stands for pressure in pounds per square in., Q stands for flow rate in gallons per minute, and 1714 is a conversion factor necessary to yield HHP in terms of horsepower. Bit manufacturers often recommend that fluid hydraulics energy across the bit nozzles be in a particular HHP range, for example 2.0 to 7.0 HHP, to ensure adequate bit tooth and bottom-of-hole cleaning (the minimum HHP) and to avoid premature erosion of the bit itself (the maximum HHP).
4190None
4191None
4192hydraulic horsepower
4193--
4194horizontal resistivity
41951.n. [Formation Evaluation]
4196The resistivity of a formation measured by flowing current in a horizontal plane. In anisotropic formations the horizontal and vertical resistivities are different. In a vertical well, wireline induction logs and measurements-while-drilling propagation logs measure the horizontal resistivity, whereas laterologs measure the horizontal resistivity with some component of the vertical. In deviated and horizontal wells, all these logs measure some mixture of both vertical and horizontal resistivity.
4197deviated hole, electrical anisotropy, parallel resistivity, perpendicular resistivity
4198None
4199None
4200--
4201hydraulic packer
42021.n. [Well Completions]
4203A type of packer used predominantly in production applications. A hydraulic packer typically is set using hydraulic pressure applied through the tubing string rather than mechanical force applied by manipulating the tubing string.
4204packer, production packer
4205None
4206None
4207--
4208hydroxyethylcellulose
42091.n. [Drilling Fluids]
4210A nonionic cellulose derivative with hydroxyethyl groups attached to the polymer structure. HEC is used as a viscosifier in brines and saline fracturing fluids, workover fluids, completion fluids and drill-in fluids. It gives pseudoplastic rheology but essentially no gel strength development. HEC offers little fluid-loss control, other than its rheological effects. HEC is seldom used in drilling fluids. Cellulose fibers are reacted with caustic soda and ethylene oxide to form HEC. Hydroxyethyl groups attach to the OH groups of the polysaccharide structure by ether linkages. A high degree of substitution (from 1.5 to 2.5 out of 3 maximum) gives HEC superior solubility in water and various brines. Being nonionic, it is not precipitated by hardness ions and disperses well at high salinity. HEC is not degraded by common bacteria.
4211brine, calcium carbonate, carboxymethyl hydroxyethylcellulose, carboxymethylcellulose, hardness ion, hydroxyethyl starch, pseudoplastic, thixotropy
4212None
4213HEC
4214--
4215hierarchical cluster analysis
42161.n. [Reservoir Characterization]
4217A method of cluster analysis in which the distance between every pair of data points is determined and the relative distances displayed on a dendogram. This method is completely accurate but is very CPU intensive when the data set has a large number of data points. For large numbers of data points, the k-means method is usually preferred.This method is sometimes used after the data have first been transformed into their principal components. The method is one possible approach to electrofacies calculations.
4218k-means cluster analysis
4219None
4220None
4221--
4222horizontal separator
42231.n. [Production Facilities]
4224A vessel, with its cylindrical axes parallel to the ground, that is used to separate oil, gas and water from the produced stream. The horizontal separator can be a two-phase or three-phase separator.
4225stage separation, three-phase separator, two-phase separator, vertical separator
4226None
4227None
4228--
4229hydraulic power pack
42301.n. [Well Workover and Intervention]
4231An assembly of components and controls necessary to provide a hydraulic power supply. In modern oilfield activities, many systems are hydraulically powered, including the majority of mobile systems such as slickline units, coiled tubing units and snubbing units. In most cases, a diesel engine is the prime mover, providing an independent power supply that is harnessed to the necessary hydraulic pump and control systems.
4232coiled tubing unit, hydraulic pumping
4233None
4234None
4235--
4236hygrometer
42371.n. [Drilling Fluids]
4238A device for measuring the moisture in a gaseous atmosphere, such as the air, usually as percent relative humidity. Mechanical hygrometers detect moisture by elongation and shrinkage of a fiber or sheet or by a device attached to a needle on a dial. Electrohygrometers measure changes in an electrical property of a moisture-sensitive sensing probe and are more reliable. Determination of the aqueous-phase activity of oil muds by the Chenevert Method requires an electrohygrometer and a series of salt solutions for calibration.
4239activity of aqueous solutions, balanced-activity oil mud, Chenevert Method, oil mud, osmosis, relative humidity, zinc chloride
4240electrohygrometer
4241None
4242--
4243high explosive
42441.n. [Perforating]
4245Chemical explosive material having an extremely high reaction rate that creates very high combustion pressures, unlike low explosives that have a much lower reaction rate and are commonly used as propellants. High explosives are further categorized as primary- and secondary-high explosive. Primary-high explosives are very sensitive, can be detonated easily and are generally used only in percussion and electrical detonators. Secondary-high explosives are less sensitive, require a high-energy shock wave to achieve detonation and are safer to handle. Secondary-high explosives are used in almost all elements of a ballistic chain, other than the detonator, such as in detonating cord and shaped charges.
4246detonating cord, shaped charge
4247None
4248None
4249--
4250horizontal transverse isotropy
42511.n. [Geophysics]
4252Transverse isotropy that has a horizontal axis of rotational symmetry. In vertically fractured rocks, properties are uniform in vertical planes parallel to the fractures, but vary in the direction perpendicular to the fractures and across the fractures.
4253None
4254None
4255TIH, HTI
4256--
4257hydraulic power unit
42581.n. [Production, Well Workover and Intervention]
4259A device used in a hydraulic system to store energy or, in some applications, dampen pressure fluctuations. Energy is stored by compressing a precharged gas bladder with hydraulic fluid from the operating or charging system. Depending on the fluid volume and precharge pressure of the accumulator, a limited amount of hydraulic energy is then available independent of any other power source. Well pressure-control systems typically incorporate sufficient accumulator capacity to enable the blowout preventer to be operated with all other power shut down.
4260None
4261None
4262HPU
4263--
4264hygroscopic
42651.adj. [Drilling Fluids]
4266Pertaining to a property of a substance that allows the substance to take up water from the surrounding atmosphere. Many materials used in drilling muds are hygroscopic, for example, high-purity grades of calcium chloride. Bentonite clay is also hygroscopic and absorbs water from the atmosphere. Care must be taken in packaging and handling such materials to avoid waste by premature hydration.
4267calcium chloride, clay, clay-water interaction, humidity, hydration, prehydration
4268None
4269None
4270--
4271high gravity solids
42721.n. [Drilling Fluids]
4273Dense solids, such as barite or hematite, which are added to a mud to increase its density, also known as weighting material. The concentration of high-gravity solids in a weighted mud is measured by the mud engineer daily using mud weight, retort data, chloride titration data and other information. Solids are reported as lbm/bbl or vol.%. The specific gravity of water is 1.00, barite is 4.20, and hematite 5.505 g/cm3. Drill solids and other low-gravity solids are normally assumed to be 2.60 g/cm3.
4274material-balance equation, mud report, retort solids, weighting material
4275None
4276Antonyms:LGS, low specific gravity solids, low-specific-gravity solids
4277--
4278icd
42791.n. [Well Completions]
4280Abbreviation for inflow control device, a passive component installed as part of a well completion to help optimize production by equalizing reservoir inflow along the length of the wellbore. Multiple inflow control devices can be installed along the reservoir section of the completion, with each device employinga specificsetting to partially choke flow. The resulting arrangement can be used to delay water or gas breakthrough by reducing annular velocity across a selected interval such as the heel of a horizontal well. ICDs are frequently used with sand screens on openhole completions.
4281None
4282None
4283None
4284--
4285induction
42861.adj. [Formation Evaluation]
4287Related to a wireline log of formation resistivity based on the principle of inducing alternating current loops in the formation and measuring the resultant signal in a receiver. In the simplest device, an alternating current of medium frequency (10?s of kHz) is passed through a transmitter coil, thereby inducing an alternating magnetic field in the formation. This field creates current loops in the formation. The loops produce their own magnetic field, which induce a current when they cross the receiver coil. This signal is proportional to the conductivity of the formation, with contributions from different regions of the formation summing approximately in conductivity. As a result, the induction log is most accurate at high conductivities and with resistive invasion. However, below about 1 ohm-m skin effect becomes important. Practical induction-logging tools use arrays of several coils, designed to achieve a specific focusing and depth of investigation. These arrays are either hardwired, such as the 6FF40, 5FF40 and others, or consist of several simple arrays that are combined in software (an array induction). For many years, the most common induction log was the 6FF40. This was often combined with the medium induction and a shallow laterolog or microresistivity log so as to correct for the effect of invasion, assuming a step profile. Induction logs also need borehole correction and shoulder-bed correction. In older tools, this was accomplished through multiple correction charts, while modern tools include software for this purpose.H.G. Doll introduced the first practical induction-logging technique in 1949. See Doll HG: Introduction to Induction logging and Application to Logging of Wells Drilled with Oil Base Mud Journal of Petroleum Technology 1, no. 6 (June 1949): 148-162.
4288array induction, cave effect, dual induction, electrical anisotropy, polarization horn, R-signal, resistivity log, skin effect, X-signal
4289None
4290None
4291--
4292injection well testing
42931.n. [Well Testing]
4294The testing of wells in which fluid is being injected into thereservoir. The most common type of test is a falloff test, in which injection is halted and thepressuredecline is measured as a function of time. The most common situation is awaterflood. In many reservoirs, theformationpressure is high enough to maintain a full column of fluid in the wellbore and the pressure can be monitored at the surface. The bottomhole pressure is then calculated by adding the weight of the fluid column to thesurface pressure. Gas-injection wells, although less common, lend themselves to similar testing. The rise in fluid pressure as a function of time while injection is taking place could theoretically be used also, but this type of approach is rarely used. The equations and theory for these tests are an exact mirror image of those for buildup anddrawdowntesting. Calculated results for these wells are usually good because the formations are commonly liquid-filled. Frequently water-injection wells are inadvertently fractured at some time in their life and consequently have a negative skin effect.
4295bottomhole pressure, buildup test, drawdown test, falloff test, formation pressure, gas injection, skin effect
4296None
4297None
4298--
4299interval velocity
43001.n. [Geophysics]
4301The velocity, typically P-wave velocity, of a specific layer or layers of rock, symbolized by vint and commonly calculated from acoustic logs or from the change in stacking velocity between seismic events on a common midpoint gather.
4302acoustic log, Dix formula, P-wave, velocity
4303None
4304None
4305--
4306icv
43071.n. [Well Completions]
4308Abbreviation for inflow control valve, an active component installed as part of a well completion to partially or completely choke flow into a well. Inflow control valves can be installed along the reservoir section of the completion, with each device typically separated from the next via a packer. Each ICV can be controlled from the surface to maintain flow conformance and, as the reservoir depletes, to stop unwanted fluids from entering the wellbore. A permanent downhole cable provides electric and hydraulic conduits to relay commands from the surface to the ICV.
4309None
4310None
4311None
4312--
4313inelastic neutron scattering
43141.n. [Formation Evaluation]
4315A neutron interaction in which part of the kinetic energy lost by a neutron in a nuclear collision excites the nucleus. The excited nucleus will usually emit characteristic gamma rays upon de-excitation. Inelastic neutron scattering is possible only if the neutron energy exceeds a characteristic threshold for the element. Inelastic neutron scattering is the principle behind the carbon-oxygen log, which is used to determine water saturation behind casing.
4316chemical neutron source, fast-neutron reaction, neutron capture, neutron generator, neutron interactions, water saturation
4317None
4318None
4319--
4320injectionpulsed neutron log
43211.n. [Production Logging]
4322An in-situ recording in which a material with high neutron-capture cross section is injected into the flowstream of a production or injection well to determine fluid paths and velocities. The material used is normally borax or water with high salinity, both of which cause a significant increase in the capture cross section measured by a pulsed-neutron log. In the most common application, the material is injected across the producing intervals of a production well. By comparing pulsed neutron logs recorded before and after injection, the injectivity, and hence productivity, of each interval can be estimated. Any cement channels or leaks will also be observed.
4323injection well, neutron capture, production log, tracer measurement, tracer-loss measurement
4324None
4325None
4326--
4327invaded zone
43281.n. [Formation Evaluation]
4329The volume close to the borehole wall in which some or all of the moveable fluids have been displaced by mud filtrate. It consists of the flushed zone and the transition zone or annulus. In simple models, the invaded zone and the flushed zone are considered synonymous.
4330diameter of invasion, flushed zone, invasion, transition zone
4331None
4332Antonyms:undisturbed zone, virgin zone
4333--
4334id
43351.n. [Drilling]
4336Inside or inner diameter. Casing, tubing and drillpipe are commonly described in terms of inside diameter and outside diameter (OD).
4337None
4338None
4339Antonyms:outside diameter
4340--
4341id
43422.n. [Formation Evaluation]
4343A particular type of induction log that was designed to read deep into the formation while maintaining reasonable vertical resolution. The deep induction log (ID) is based on the measurement of a 6FF40 array and was combined with a medium induction array to form the dual induction tool. Versions built after 1968 had a small extra transmitter coil to reduce the borehole effect on the medium induction while changing the deep response very little. The midpoint of the ID integrated radial geometrical factor is at 62 in. [157 cm] radius for high resistivities, reducing to 45 in. [114 cm] at 1 ohm-m. ID receives very little signal from within 20 in. [50 cm] of the tool. The vertical resolution is about 8 ft [2.4 m] but varies with local conditions.
4344None
4345None
4346deep induction
4347--
4348infinite acting radial flow
43491.n. [Well Testing]
4350Flow into the wellbore during a well test, from areservoirwith no apparent outer boundary limit affecting fluid flow during the test period, the direction of flow being perpendicular to the axis of the well.Unless an outer boundary, such as a nearbyfault, is close to the wellbore, it usually takes a day or more for outer boundaries to affect well-test results. Since most tests are of relatively short duration, outer boundaries usually do not affect test results.
4351fluid flow
4352None
4353None
4354--
4355injection well testing
43561.n. [Well Testing]
4357The testing of wells in which fluid is being injected into thereservoir. The most common type of test is a falloff test, in which injection is halted and thepressuredecline is measured as a function of time. The most common situation is awaterflood. In many reservoirs, theformationpressure is high enough to maintain a full column of fluid in the wellbore and the pressure can be monitored at the surface. The bottomhole pressure is then calculated by adding the weight of the fluid column to thesurface pressure. Gas-injection wells, although less common, lend themselves to similar testing. The rise in fluid pressure as a function of time while injection is taking place could theoretically be used also, but this type of approach is rarely used. The equations and theory for these tests are an exact mirror image of those for buildup anddrawdowntesting. Calculated results for these wells are usually good because the formations are commonly liquid-filled. Frequently water-injection wells are inadvertently fractured at some time in their life and consequently have a negative skin effect.
4358bottomhole pressure, buildup test, drawdown test, falloff test, formation pressure, gas injection, skin effect
4359None
4360None
4361--
4362invasion
43631.n. [Formation Evaluation]
4364The process by which mud filtrate, and sometimes whole mud, enters a permeable formation. The mud filtrate displaces some or all of the moveable fluids in the formation, leaving an invaded zone. The invasion process is complex. It is generally considered to start with a short initial spurt loss when the bit penetrates the rock. During this period, invasion depends on formation permeability, among other factors. A mudcake is soon formed, after which invasion is either described as dynamic, when mud is being circulated, or static, when it is not. In both cases, the volume of invasion depends little on formation properties and strongly on other factors such as mudcake permeability and differential pressure.However, the profile of the invasion front within the formation, both vertically and radially, does depend on formation properties. With high permeability and with different densities of filtrate and formation fluid, gravity can cause vertical movement of the filtrate, leading to different depths of invasion at the top and bottom of a zone. With two moveable phases (oil and water) and differing permeabilities, an annulus can be formed. The radial profile from the wellbore out to the undisturbed zone depends on permeability, with lower permeabilities leading to sharper transitions.
4365filtrate slump, flushed zone, formation fluid, invaded zone, moved hydrocarbons, transition zone, undisturbed zone
4366None
4367None
4368--
4369invasion
43702.adj. [Formation Evaluation]
4371Pertaining to the influence of invasion on the response of logging measurements. For example, an invasion correction is the correction made to a deep-reading measurement such as an induction log for the effect of the invaded zone. The correction is based on a suitable invasion model, such as a step profile or transition zone model.
4372annulus
4373None
4374None
4375--
4376ieom
43771.n. [Drilling Fluids]
4378An outdated distinction between two types of oil muds. In the past, invert-emulsion oil muds were those with more than 5 vol.% emulsified water, and oil-base muds were those with less than 5 vol.% water. Today, this distinction is not pertinent because the general term oil mud covers all water concentrations.
4379None
4380None
4381invert-emulsion oil mud
4382--
4383infinite acting reservoir
43841.n. [Well Testing]
4385Areservoirwith no apparent outer boundary limit affecting fluid flow during a test period. Unless an outer boundary, such as a nearbyfault, is close to the wellbore, it usually takes a day or more for outer boundaries to affect well-test results. Since most tests are of relatively short duration, outer boundaries usually do not affect test results.
4386fluid flow
4387None
4388None
4389--
4390injectite
43911.n. [Geology]
4392Structures formed by sediment injection. Because they resemble intrusive and extrusive igneous features, much of the vocabulary for describing injectites, or clastic intrusions, comes from igneous geology. Sills are emplaced parallel to bedding, whereas dikes cut through bedding. The strata containing the intrusion are called host strata and the layers that feed the intrusion are the parent beds. Sand-injection features exhibit size scales from millimeters to kilometers, and have been seen in cores, borehole image logs, seismic sections, outcrops, aerial photographs and satellite images.
4393seismite
4394None
4395clastic intrusion
4396--
4397inverse filter
43981.n. [Formation Evaluation]
4399Generally, a finite impulse response (FIR) filter that has been designed to transform the usually irregular vertical response functions of raw measurements into a smooth, well-behaved response function such as a Gaussian response or a Kaiser window function. The criteria for designing inverse filters can include vertical response, depth of investigation and near-field (cave effect) response. Inverse filters have been used for many years to improve the response of induction arrays.
4400deconvolution, response matched
4401None
4402None
4403--
4404igneous
44051.adj. [Geology]
4406Pertaining to one of three main classes of rocks (igneous, metamorphic and sedimentary). Igneous rocks crystallize from molten rock, or magma, with interlocking mineral crystals. Igneous rocks that crystallize slowly, typically below the surface of the Earth, are plutonic igneous rocks and have large crystals (large enough to see with the naked eye). Volcanic igneous rocks crystallize quickly at the Earth's surface and have small crystals (usually too small to see without magnification). Common examples include granite (plutonic) and rhyolite (volcanic), diorite (plutonic) and andesite (volcanic), and gabbro (plutonic) and basalt (volcanic). Igneous rocks typically comprise the minerals quartz, mica, feldspar, amphibole, pyroxene and olivine.
4407basement, diapir, dike, felsic, geomagnetic polarity reversal, groundwater, hard rock, hydrothermal, hydrothermal alteration, mafic, mantle, marker bed, massif, midoceanic ridge, montmorillonite, nonconformity, orogeny, plate tectonics, reservoir, sedimentary, soft rock, unconformity, vesicle, vesicular porosity, volcano
4408None
4409None
4410--
4411infinite acting reservoir
44121.n. [Well Testing]
4413Areservoirwith no apparent outer boundary limit affecting fluid flow during a test period. Unless an outer boundary, such as a nearbyfault, is close to the wellbore, it usually takes a day or more for outer boundaries to affect well-test results. Since most tests are of relatively short duration, outer boundaries usually do not affect test results.
4414fluid flow
4415None
4416None
4417--
4418in line
44191.n. [Geophysics]
4420A seismic line within a 3D survey parallel to the direction in which the data were acquired. In marine seismic data, the in-line direction is that in which the recording vessel tows the streamers.
4421acquisition, crossline, extended spread, spread, streamer, three-dimensional seismic data
4422None
4423None
4424--
4425inversion
44261.n. [Geology]
4427The reversal of features, particularly structural features such as faults, by reactivation. For example, a normal fault might move in a direction opposite to its initial movement.
4428fault, normal fault, structure
4429None
4430None
4431--
4432inversion
44332.n. [Geology]
4434The atypical appearance of structural and topographic features, such as an anticline being exposed in a valley instead of as a hill; also called inverted relief.
4435anticline, structure, topographic map
4436None
4437None
4438--
4439inversion
44403.n. [Geophysics]
4441A mathematical process by which data are used to generate a model that is consistent with the data, the process of solving the inverse problem. In seismology, surface seismic data, vertical seismic profiles and well log data can be used to perform inversion, the result of which is a model of Earth layers and their thickness, density and P- and S-wave velocities. Successful seismic inversion usually requires a high signal-to-noise ratio and a large bandwidth.
4442convergence, layer stripping, lithostratigraphic inversion, noise, Occam's inversion, parametric, processing, seismic modeling, signal, signal-to-noise ratio
4443None
4444None
4445--
4446im
44471.n. [Formation Evaluation]
4448A particular type of induction log designed to read an intermediate distance into the formation while maintaining good vertical resolution. The medium-induction array of eight coils (IM) is produced by three transmitters and five receivers running at 20 kHz. A small fourth transmitter coil was added in tools built since 1968. The midpoint of the integrated radial geometrical factor is 30 in. [76 cm] in radius. The vertical resolution is about 4 ft [1.2 m] but varies with conditions. The IM is combined with a deep-induction log on the same sonde to produce a dual induction log.
4449None
4450None
4451medium induction
4452--
4453inflatable packer
44541.n. [Well Completions]
4455A type of packer that uses an inflatable bladder to expand the packer element against the casing or wellbore. In preparation for setting the packer, a drop ball or series of tubing movements are generally required, with the hydraulic pressure required to inflate the packer provided by carefully applying surface pump pressure. Inflatable packers are capable of relatively large expansion ratios, an important factor in through-tubing work where the tubing size or completion components can impose a significant size restriction on devices designed to set in the casing or liner below the tubing.
4456drop ball
4457None
4458None
4459--
4460insert
44611.n. [Formation Evaluation]
4462A section on a log print that gives the scales of the curves displayed and the depth scale. There usually is an insert at the beginning and end of each interval surveyed.
4463heading, repeat section, tail, track
4464None
4465None
4466--
4467invert emulsion
44681.n. [Drilling Fluids]
4469An emulsion in which oil is the continuous or external phase and water is the internal phase. Invert emulsion usually refers to an oil-base mud, and the terms are considered synonyms. Invert-emulsion muds can be run with 5 to 50% water in the liquid phase, although there are systems that are 100% oil.
4470emulsion mud, interfacial tension, invert-emulsion oil mud, oil-base mud, surface tension
4471None
4472None
4473--
4474image well
44751.n. [Well Testing]
4476A virtual well used to mathematically create the effect of a flow barrier. The pressure transient behavior both at the well and in the reservoir is identical for the following two cases: 1) a well near a barrier represented by a plane normal to the bedding, or 2) a well producing or injecting at the same rate as the tested well. In the second case, the effect is of a barrier bisecting the space between the two wells.
4477bed, injection well, producing well
4478None
4479None
4480--
4481inflow control device
44821.n. [Well Completions]
4483A passive component installed as part of a well completion to help optimize production by equalizing reservoir inflow along the length of the wellbore. Multiple inflow control devices can be installed along the reservoir section of the completion, with each device employinga specificsetting to partially choke flow. The resulting arrangement can be used to delay water or gas breakthrough by reducing annular velocity across a selected interval such as the heel of a horizontal well. Inflow control devices are frequently used with sand screens on openhole completions.
4484None
4485None
4486ICD
4487--
4488inside out air seat test
44891.n. [Production]
4490A pressure test that can be performed only on a trunnion mounted ball valve with double piston effectseats. By closing the valves and pressurizing the body cavity, all of the seals in an independent seating ball valve can be pressure tested.
4491None
4492None
4493None
4494--
4495invert emulsion oil mud
44961.n. [Drilling Fluids]
4497An outdated distinction between two types of oil muds. In the past, invert-emulsion oil muds were those with more than 5 vol.% emulsified water, and oil-base muds were those with less than 5 vol.% water. Today, this distinction is not pertinent because the general term oil mud covers all water concentrations.
4498None
4499None
4500invert-emulsion oil mud
4501--
4502impedance
45031.n. [Geophysics]
4504In acoustics, the product of velocity times density, also called acoustic impedance and symbolized by Z. The reflection coefficient of an interface depends on the contrast in acoustic impedance of the rock on either side of the interface.
4505acoustic impedance, reflection coefficient
4506None
4507None
4508--
4509impedance
45102.n. [Geophysics]
4511In electromagnetics or electrical circuit theory, the ratio of voltage to current when these are represented by phasor quantities in alternating current circuits. (A phasor is a complex number that represents the amplitude and phase of a quantity that varies sinusoidally in time.) Electrical impedance, also symbolized by Z, is a complex number that has the same units (ohms) as resistivity.
4512None
4513None
4514None
4515--
4516inflow control valve
45171.n. [Well Completions]
4518An active component installed as part of a well completion to partially or completely choke flow into a well. Inflow control valves can be installed along the reservoir section of the completion, with each device typically separated from the next via a packer. Each valve can be controlled from the surface to maintain flow conformance and, as the reservoir depletes, to stop unwanted fluids from entering the wellbore. A permanent downhole cable provides electric and hydraulic conduits to relay commands from the surface to each valve.
4519None
4520None
4521ICV
4522--
4523in situ combustion
45241.n. [Enhanced Oil Recovery, Heavy Oil]
4525A method of thermal recovery in which fire is generated inside the reservoir by injecting a gas containing oxygen, such as air. A special heater in the well ignites the oil in the reservoir and starts a fire.The heat generated by burning the heavy hydrocarbons in place produces hydrocarbon cracking, vaporization of light hydrocarbons and reservoir water in addition to the deposition of heavier hydrocarbons known as coke. As the fire moves, the burning front pushes ahead a mixture of hot combustion gases, steam and hot water, which in turn reduces oil viscosity and displaces oil toward production wells.Additionally, the light hydrocarbons and the steam move ahead of the burning front, condensing into liquids, which adds the advantages of miscible displacement and hot waterflooding.In situ combustion is also known as fire flooding or fireflood.
4526cyclic steam injection, dry combustion, dry forward combustion, enhanced oil recovery, hydrocarbon, reverse combustion, steamflood, wet combustion
4527None
4528None
4529--
4530invert emulsion oil mud
45311.n. [Drilling Fluids]
4532An outdated distinction between two types of oil muds. In the past, invert-emulsion oil muds were those with more than 5 vol.% emulsified water, and oil-base muds were those with less than 5 vol.% water. Today, this distinction is not pertinent because the general term oil mud covers all water concentrations.
4533asphalt, emulsion, fatty-acid soap, hectorite, interfacial tension, invert emulsion, mud, oil content, oil mud, oil-base mud, oil-in-water emulsion, oil-mud emulsifier, organophilic clay, organophilic lignite, rheology modifier, surface tension, synthetic-base fluid, synthetic-base mud, water-in-oil emulsion
4534None
4535None
4536--
4537impermeable
45381.adj. [Geology]
4539Pertaining to a rock that is incapable of transmitting fluids because of low permeability. Shale has a high porosity, but its pores are small and disconnected, so it is relatively impermeable. Impermeable rocks are desirable sealing rocks or cap rocks for reservoirs because hydrocarbons cannot pass through them readily.
4540pore pressure, reservoir, seal, tight, trap
4541None
4542Antonyms:permeable
4543--
4544information theory
45451.n. [Reservoir Characterization]
4546The study, collection and management of information, especially with respect to computer technology. Information theory is an important component in the construction and efficient usage of databases.
4547None
4548None
4549None
4550--
4551in situ viscosity evaluation
45521.n. [Heavy Oil]
4553Downhole measurement of fluid viscosity, typically performed either with logging tools based on nuclear magnetic resonance (NMR) or with sampling tools such as formation testers.
4554None
4555None
4556None
4557--
4558io
45591.n. [Drilling Fluids]
4560A synthetic hydrocarbon liquid made by the polymerization of ethylene, H2C=CH2. IOs are one of several synthetic fluids that have recently been used as base for synthetic-base muds and in other applications where refined oils might otherwise be used except for HSE concerns. IOs are linear structures that have their olefin double bond in the center of the chain length. They are made by isomerization of linear alphaolefins (LAO), which have their double bond at the end of the chain. Because the olefin bond is in the central area of the chain, the physical properties of IOs are different (for example, they are generally lower viscosity) compared with the LAOs from which they are made.
4561diesel-oil mud, emulsion mud, linear alphaolefin, olefinic hydrocarbon, oligomer, polyalphaolefin, polymer, synthetic-base fluid, synthetic-base mud
4562None
4563isomerized olefin, polyolefin
4564--
4565impermeable barrier
45661.n. [Well Testing]
4567A single, impenetrable barrier to fluid flow in a reservoir that causes a change of a factor of two in the slope of buildup or drawdown curves. These are often observed in a normal test if the barrier is close (a few hundred feet or less) to the tested well. Most tests are not long enough to detect the presence of distant barriers. Two perpendicular barriers cause a change in the slope of a factor of four, and so forth, and models exist for a variety of geometries, typically for up to four barriers.
4568fluid flow
4569None
4570None
4571--
4572inhibited acid
45731.n. [Well Workover and Intervention]
4574An acid treatment fluid that has been mixed with chemical additives to control the corrosive effect on the mixing and pumping equipment, as well as on any wellbore tubulars and completion equipment that the fluid may contact. Almost all acid treatments require the addition of an inhibitor to protect against undesirable reactions.
4575treatment fluid
4576None
4577None
4578--
4579instrumented pig
45801.n. [Production Testing]
4581A device made of rubber or polyurethane that has electronic devices. An instrumented pig is run through a pipeline to record irregularities that could represent corrosion. An instrumented pig is also called a smart pig.
4582None
4583None
4584None
4585--
4586iron oxide
45871.n. [Drilling Fluids]
4588A group of minerals and inorganic compounds made up of iron that is in +2 (ferrous) and +3 (ferric) valence states and oxygen in the -2 valence state, such as ferrous oxide, FeO, and ferric oxide, Fe2O3. Fe3O4 is a mixture of ferric oxide and ferrous oxide that commonly occurs in a fine-grained, magnetic crystalline form. Hematite, Fe2O3, the most common iron oxide, exists in several crystalline forms. Other forms of hematite are too abrasive to use as weighting material in drilling fluids.
4589abrasion test, barite, hematite, scavenger, sulfide, weighting material
4590None
4591None
4592--
4593impulse activation
45941.n. [Production Logging]
4595A type of oxygen activation technique for measuring water flow in which a short neutron burst is followed by a long observation period, during which the activated flowing oxygen is recognized at the detector by its signature. Stationary oxygen gives a gradually decaying signal, whereas flowing oxygen can be distinguished by a peak at a time after the neutron pulse that is related to its velocity. To cover a wide range in water velocity, several detectors at different spacings are needed. The flow volume can be estimated from the area under the peak. While recordings are typically made with the tool stationary, continuous logs are also possible.In an alternative type of impulse method, the neutrons are emitted in regular bursts until the count rate from the activated oxygen reaches a constant level. Then, after terminating the bursts, the time for the count rate to decrease by one half is measured. This time can be related to the water velocity.
4596activation log, neutron capture, neutron generator, pulsed neutron spectroscopy measurement
4597None
4598None
4599--
4600initial flow period
46011.n. [Well Testing]
4602A short flow period at the beginning of a drillstem test. This period is followed immediately by a longer shut-in period to allow the pressure to closely approach initial reservoir pressure. The initial flow period is commonly 5 to 10 minutes, and the initial shut-in period is commonly 30 minutes to one hour. When plotted on a pressure buildup plot, extrapolation of the best straight line gives what is usually accepted as the best obtainable value of initial formation pressure.
4603final flow period
4604None
4605None
4606--
4607intelligent well
46081.n. [Well Completions]
4609A well equipped with monitoring equipment and completion components that can be adjusted to optimize production, either automatically or with some operator intervention.
4610None
4611None
4612None
4613--
4614irreducible water
46151.n. [Formation Evaluation]
4616The lowest water saturation, Swi, that can be achieved in a core plug by displacing the water by oil or gas. The state is usually achieved by flowing oil or gas through a water-saturated sample, or spinning it in a centrifuge to displace the water with oil or gas. The term is somewhat imprecise because the irreducible water saturation is dependent on the final drive pressure (when flowing oil or gas) or the maximum speed of rotation (in a centrifuge). The related term connate water saturation is the lowest water saturation found in situ.
4617centrifuge
4618None
4619None
4620--
4621in line
46221.n. [Geophysics]
4623A seismic line within a 3D survey parallel to the direction in which the data were acquired. In marine seismic data, the in-line direction is that in which the recording vessel tows the streamers.
4624acquisition, crossline, extended spread, spread, streamer, three-dimensional seismic data
4625None
4626None
4627--
4628initial reservoir pressure
46291.n. [Well Testing]
4630The reservoir pressure measured in a discovery well, usually referred to as pi. This value is necessary for many reservoir engineering calculations, such as reserve determination.
4631None
4632None
4633None
4634--
4635intensifier
46361.n. [Well Workover and Intervention]
4637A downhole tool used with a jar to increase the impact force imparted as the jar is fired. Similar in function to an accelerator, intensifiers typically use compressed gas rather than a mechanical spring to store the energy released during operation.
4638None
4639None
4640None
4641--
4642isochronal test
46431.n. [Well Testing]
4644A multirate test designed as a series of drawdown and buildup sequences at different drawdown flow rates, with each drawdown of the same duration and each buildup reaching stabilization at the same pressure as at the start of the test. The purpose of the test is to determine well deliverability. This type of test is most commonly done in gas wells.
4645modified isochronal test
4646None
4647None
4648--
4649isochronal test
46502.n. [Production Testing]
4651A type of deliverability test conducted in gas wells. This test is used to generate a stabilized gas deliverability curve (IPR) without actually flowing the well for the time required to achieve stabilized conditions (pseudosteady state). This type of test is especially useful for low-permeability reservoirs.In an isochronal test, the well flows at a constant rate and then is shut in, allowing the pressure to build up to the <a href="Display.cfm?Term=average%20reservoir%20pressure">average <a href="Display.cfm?Term=reservoir">reservoir pressure. The same procedure typically is repeated four times. It is called isochronal because the flow periods are of the same length. A stabilized point (pseudosteady state) is usually obtained at the end of the test.
4652None
4653None
4654None
4655--
4656in situ combustion
46571.n. [Heavy Oil, Enhanced Oil Recovery]
4658A method of thermal recovery in which fire is generated inside the reservoir by injecting a gas containing oxygen, such as air. A special heater in the well ignites the oil in the reservoir and starts a fire.The heat generated by burning the heavy hydrocarbons in place produces hydrocarbon cracking, vaporization of light hydrocarbons and reservoir water in addition to the deposition of heavier hydrocarbons known as coke. As the fire moves, the burning front pushes ahead a mixture of hot combustion gases, steam and hot water, which in turn reduces oil viscosity and displaces oil toward production wells.Additionally, the light hydrocarbons and the steam move ahead of the burning front, condensing into liquids, which adds the advantages of miscible displacement and hot waterflooding.In situ combustion is also known as fire flooding or fireflood.
4659cyclic steam injection, dry combustion, dry forward combustion, enhanced oil recovery, hydrocarbon, reverse combustion, steamflood, wet combustion
4660None
4661None
4662--
4663initial shut in period
46641.n. [Well Testing]
4665The comparatively short shut-in period following the initial flow period of a drillstem test. This period is followed immediately by much longer flow and shut-in periods to allow the pressure to closely approach initial reservoir pressure. The initial flow period is commonly 5 to 10 minutes, and the initial shut-in period is commonly 30 minutes to one hour. When plotted on a pressure buildup plot, extrapolation of the best straight line gives what is usually accepted as the best obtainable value of initial formation pressure.
4666drillstem test, final shut-in period, formation pressure, initial flow period, initial reservoir pressure
4667None
4668None
4669--
4670interfacial tension
46711.n. [Enhanced Oil Recovery, Drilling Fluids]
4672A property of the interface between two immiscible phases. When the phases are both liquid, it is termed interfacial tension; when one of the phases is air, it is termed surface tension. Interfacial tension is the Gibbs free energy per unit area of interface at fixed temperature and pressure. Interfacial tension occurs because a molecule near an interface has different molecular interactions than an equivalent molecule within the bulk fluid. Surfactant molecules preferentially position themselves at the interface and thereby lower the interfacial tension.
4673surface tension
4674None
4675None
4676--
4677isomerized olefin
46781.n. [Drilling Fluids]
4679A synthetic hydrocarbon liquid made by the polymerization of ethylene, H2C=CH2. IOs are one of several synthetic fluids that have recently been used as base for synthetic-base muds and in other applications where refined oils might otherwise be used except for HSE concerns. IOs are linear structures that have their olefin double bond in the center of the chain length. They are made by isomerization of linear alphaolefins (LAO), which have their double bond at the end of the chain. Because the olefin bond is in the central area of the chain, the physical properties of IOs are different (for example, they are generally lower viscosity) compared with the LAOs from which they are made.
4680diesel-oil mud, emulsion mud, linear alphaolefin, olefinic hydrocarbon, oligomer, polyalphaolefin, polymer, synthetic-base fluid, synthetic-base mud
4681polyolefin
4682IO
4683--
4684in situ viscosity evaluation
46851.n. [Formation Evaluation]
4686Downhole measurement of fluid viscosity, typically performed either with logging tools based on nuclear magnetic resonance (NMR) or with sampling tools such as formation testers.
4687in-situ viscosity evaluation
4688None
4689None
4690--
4691initial shut in period
46921.n. [Well Testing]
4693The comparatively short shut-in period following the initial flow period of a drillstem test. This period is followed immediately by much longer flow and shut-in periods to allow the pressure to closely approach initial reservoir pressure. The initial flow period is commonly 5 to 10 minutes, and the initial shut-in period is commonly 30 minutes to one hour. When plotted on a pressure buildup plot, extrapolation of the best straight line gives what is usually accepted as the best obtainable value of initial formation pressure.
4694drillstem test, final shut-in period, formation pressure, initial flow period, initial reservoir pressure
4695None
4696None
4697--
4698interference testing
46991.n. [Well Testing]
4700The pressure variation with time recorded in observation wells resulting from changes in rates in production or injection wells. In commercially viable reservoirs, it usually takes considerable time for production at one well to measurably affect the pressure at an adjacent well. Consequently, interference testing has been uncommon because of the cost and the difficulty in maintaining fixed flow rates over an extended time period. With the increasing number of permanent gauge installations, interference testing may become more common than in the past.
4701injection well
4702well interference testing
4703None
4704--
4705isotropic
47061.adj. [Geology]
4707Directionally uniform, such that the physical properties of the material do not vary in different directions. In rocks, changes in physical properties in different directions, such as the alignment ofmineralgrains or theseismicvelocity measured parallel or perpendicular to bedding surfaces, are forms of anisotropy. (Compare with homogeneity).
4708anisotropy, isotropic formation, isotropic permeability, isotropy
4709None
4710None
4711--
4712incident angle
47131.n. [Geophysics]
4714The acute angle at which a raypath impinges upon a line normal to an interface, such as a seismic wave impinging upon strata. Normal incidence is the case in which the angle of incidence is zero, the wavefront is parallel to the surface and its raypath is perpendicular, or normal, to the interface. Snell's law describes the relationship between the angle of incidence and the angle of refraction of a wave.
4715angle of approach, critical reflection, head wave, raypath, refraction, refractive index, refractor, Zoeppritz equations
4716None
4717None
4718--
4719injection line
47201.n. [Well Completions]
4721A small-diameter conduit that is run alongside production tubulars to enable injection of inhibitors or similar treatments during production. Conditions such as high hydrogen sulfide [H2S] concentrations or severe scale deposition can be counteracted by injection of treatment chemicals and inhibitors during production.
4722inhibitor
4723None
4724None
4725--
4726intermediate casing
47271.n. [Well Completions]
4728A casing string that is generally set in place after the surface casing and before the production casing. The intermediate casing string provides protection against caving of weak or abnormally pressured formations and enables the use of drilling fluids of different density necessary for the control of lower formations.
4729casing string, drilling fluid, intermediate casing string, surface casing
4730None
4731None
4732--
4733isotropic formation
47341.n. [Well Testing]
4735A type of formation whose rock properties are the same in all directions. Although this never actually occurs, fluid flow in rocks approximates this situation closely enough to consider certain formations isotropic.
4736homogeneous formation
4737None
4738Antonyms:anisotropic formation
4739--
4740inclination
47411.n. [Drilling]
4742The deviation from vertical, irrespective of compass direction, expressed in degrees. Inclination is measured initially with a pendulum mechanism, and confirmed with MWD accelerometers or gyroscopes. For most vertical wellbores, inclination is the only measurement of the path of the wellbore. For intentionally deviated wellbores, or wells close to legal boundaries, directional information is usually also measured.
4743accelerometer, azimuth, deviated hole, survey
4744None
4745None
4746--
4747injection pattern
47481.n. [Enhanced Oil Recovery]
4749The particular arrangement of production and injection wells. The injection pattern for an individual field or part of a field is based on the location of existing wells, reservoir size and shape, cost of new wells and the recovery increase associated with various injection patterns. The flood pattern can be altered during the life of a field to change the direction of flow in a reservoir with the intent of contacting unswept oil. It is common to reduce the pattern size by infill drilling, which improves oil recovery by increasing reservoir continuity between injectors and producers. Common injection patterns are direct line drive, staggered line drive, two-spot, three-spot, four-spot, five-spot, seven-spot and nine-spot. Normally, the two-spot and three-spot patterns are used for pilot testing purposes. The patterns are called normal or regular when they include only one production well per pattern. Patterns are described as inverted when they include only one injection well per pattern.
4750enhanced oil recovery, injection well, off-pattern well, waterflooding
4751None
4752None
4753--
4754intermediate casing string
47551.n. [Drilling]
4756A length of pipe used below the surface casing string, but before the production casing is run, to isolate one or more zones of the openhole to enable deepening of the well. There may be several intermediate casing strings. Depending on well conditions, these strings may have higher pressure integrity than the prior casing strings, especially when abnormally pressured formations are expected during the drilling of the next openhole section.
4757casing string, production casing
4758None
4759None
4760--
4761isotropic permeability
47621.n. [Well Testing]
4763Permeability that is the same in all directions. This never really occurs, but permeability along various directions of a formation is often close enough for calculation purposes.
4764directional permeability
4765None
4766None
4767--
4768indicator methods
47691.n. [Reservoir Characterization]
4770An approach to stochastic imaging or simulation of a reservoir that is nonparametric. The Gaussian approach is a simpler approach that includes a normal score transform of the data to produce a new variable that is univariate and normally distributed.
4771Gaussian techniques, parametric, stochastic analysis
4772None
4773None
4774--
4775injection pulsed neutron log
47761.n. [Production Logging]
4777An in-situ recording in which a material with high neutron-capture cross section is injected into the flowstream of a production or injection well to determine fluid paths and velocities. The material used is normally borax or water with high salinity, both of which cause a significant increase in the capture cross section measured by a pulsed-neutron log. In the most common application, the material is injected across the producing intervals of a production well. By comparing pulsed neutron logs recorded before and after injection, the injectivity, and hence productivity, of each interval can be estimated. Any cement channels or leaks will also be observed.
4778injection well, neutron capture, production log, tracer measurement, tracer-loss measurement
4779None
4780None
4781--
4782interstitial gas
47831.n. [Reservoir Characterization, Shale Gas]
4784The gas stored in the pore space of a reservoir rock. Measurement of interstitial gas and adsorbed gas, which is the gas accumulated on the surface of another solid material, such as a grain of reservoir rock, allows calculation of gas in place in a reservoir.
4785None
4786pore gas
4787None
4788--
4789isotropy
47901.n. [Geology]
4791A quality of directional uniformity in material such that physical properties do not vary in different directions. In rocks, changes in physical properties in different directions, such as the alignment of mineral grains or the seismic velocity measured parallel or perpendicular to bedding surfaces, are forms of anisotropy. (Compare with homogeneity.)
4792anisotropy, homogeneity, isotropic, isotropic formation, isotropic permeability
4793None
4794None
4795--
4796induced gamma ray spectroscopy
47971.n. [Formation Evaluation]
4798The principle of an activation log, which is a log of elemental concentrations derived from the characteristic energy levels of gamma rays emitted by a nucleus that has been activated by neutron bombardment. The term is often used to refer specifically to the pulsed neutron spectroscopy measurement.
4799activation log, elemental capture spectroscopy, geochemical log, neutron interactions, pulsed neutron spectroscopy log, spectrum
4800None
4801None
4802--
4803injection pump
48041.n. [Well Completions]
4805Any pump used to inject fluid into the reservoir or production system. Injection pumps vary in volume and pressure capacity, from the large injection pumps used in water-injection wells, to much smaller low-volume injection pumps used in continuous scale-inhibitor treatments.
4806scale inhibitor
4807None
4808None
4809--
4810interstitial water
48111.n. [Geology]
4812Water that occurs naturally within the pores of rock. Water from fluids introduced to a formation through drilling or other interference, such as mud and seawater, does not constitute interstitial water. Interstitial water, or formation water, might not have been the water present when the rock originally formed. In contrast, connate water is the water trapped in the pores of a rock during its formation, also called fossil water.
4813brine, fresh water, pore
4814None
4815Antonyms:connate water
4816--
4817iterative forward modeling
48181.n. [Formation Evaluation]
4819The use of repeated forward modeling of a logging tool response to produce modeled logs that very closely match the measured logs. The final model is then the log analyst?s best estimate of the formation properties. Iterative forward modeling is a hand-operated inversion. The technique is used mainly for laterologs and induction logs when the formation or the environment are complex, so that the environmental effects cannot be separated and treated individually by automatic inversion. Iterative forward modeling allows the log analyst to use local knowledge and petrophysics to select between the many possible solutions that are mathematically correct. These cases occur most often in horizontal wells, or vertical wells with the combined effects of invasion and large resistivity contrast between beds.
4820forward modeling
4821None
4822None
4823--
4824induced particle plugging
48251.n. [Enhanced Oil Recovery]
4826A type of damage in which foreign particles injected during normal well operations, such as drilling, completion, workover, stimulation or enhanced recovery, block the near-wellbore formation, reducing well productivity.Potentially damaging particles in drilling fluids include clays, cuttings, weighting agents and fluid-loss control materials. In workover and stimulation fluids, suspended solids include bacteria and polymer residues. Foreign plugging particles can also be introduced as a result of poor water-handling practices. These foreign particles include debris from tanks and tubing.
4827fines migration, fluid-loss-control material
4828None
4829None
4830--
4831injection well
48321.n. [Well Completions]
4833A well in which fluids are injected rather than produced, the primary objective typically being to maintain reservoir pressure. Two main types of injection are common: gas and water. Separated gas from production wells or possibly imported gas may be reinjected into the upper gas section of the reservoir. Water-injection wells are common offshore, where filtered and treated seawater is injected into a lower water-bearing section of the reservoir.
4834gas injection, reservoir pressure
4835None
4836None
4837--
4838interval transit time
48391.n. [Geophysics]
4840The amount of time for a wave to travel a certain distance, proportional to the reciprocal of velocity, typically measured in microseconds per foot by an acoustic log and symbolized by t or DT. P-wave interval transit times for common sedimentary rock types range from 43 (dolostone) to 160 (unconsolidated shales) microseconds per foot, and can be distinguished from measurements of steel casing, which has a consistent transit time of 57 microseconds per foot.
4841drift, wave
4842delta t, slowness, transit time
4843None
4844--
4845iterative methods
48461.n. [Reservoir Characterization]
4847Mathematical techniques that require an algorithm or equation to be repeated until a condition is met. These methods usually require the convergence of a result to a value. Computers are excellent tools for performing iterative techniques quickly and efficiently.
4848None
4849None
4850None
4851--
4852j factor
48531.n. [Formation Evaluation]
4854Another term for pseudogeometrical factor, the response of a logging measurement as a function of distance from the tool. The pseudogeometrical factor is normally radial, reflecting the response perpendicular to the tool. It can be a differential factor, which is the contribution to the signal at a particular distance, but is more normally integrated, which is the sum of all signals from the tool to a particular distance.The pseudogeometrical factor developed from the concept of the geometrical factor, and is expressed in the same way. For example, for a radial distance x from the tool, the integrated radial pseudogeometrical factor, Jx, can be written as:Jx = (Ux - Ut) / (Uxo - Ut)where Ut is the log reading of the undisturbed zone (or, alternatively, the reading with no invasion), Uxo is the log reading of the flushed zone (or, alternatively, the reading with infinite invasion), and Ux is the log reading with a step profile invasion to depth x. Unlike the geometrical factor, Jx depends on the values of both Uxo and Ut. Pseudogeometrical factors are a useful way to express the radial response (or vertical response) in typical conditions. The physics of each measurement determines how much Jx varies with Uxo and Ut.Pseudogeometrical factors are often used to express the response of nuclear and resistivity logs, but are not appropriate for acoustic and electromagnetic propagation logs (where the response is too dependent on the contrast in properties), or nuclear magnetic resonance logs (where the response is too localized).
4855pseudogeometrical factor
4856None
4857None
4858--
4859jar
48601.n. [Drilling]
4861A mechanical device used downhole to deliver an impact load to another downhole component, especially when that component is stuck. There are two primary types, hydraulic and mechanical jars. While their respective designs are quite different, their operation is similar. Energy is stored in the drillstring and suddenly released by the jar when it fires. The principle is similar to that of a carpenter using a hammer. Kinetic energy is stored in the hammer as it is swung, and suddenly released to the nail and board when the hammer strikes the nail. Jars can be designed to strike up, down, or both. In the case of jarring up above a stuck bottomhole assembly, the driller slowly pulls up on the drillstring but the BHA does not move. Since the top of the drillstring is moving up, this means that the drillstring itself is stretching and storing energy. When the jars reach their firing point, they suddenly allow one section of the jar to move axially relative to a second, being pulled up rapidly in much the same way that one end of a stretched spring moves when released. After a few inches of movement, this moving section slams into a steel shoulder, imparting an impact load. In addition to the mechanical and hydraulic versions, jars are classified as drilling jars or fishing jars. The operation of the two types is similar, and both deliver approximately the same impact blow, but the drilling jar is built such that it can better withstand the rotary and vibrational loading associated with drilling.
4862bottomhole assembly, fishing tool
4863None
4864None
4865--
4866jar
48672.n. [Well Completions]
4868A downhole tool that is used to impart a heavy blow or impact load to a downhole tool assembly. Commonly used in fishing operations to free stuck objects, jars are available in a range of sizes and capacities to deliver upward or downward impact loads. Some slickline tool assemblies use jars to operate tools that contain shear pins or spring profiles in their operating method.
4869None
4870None
4871None
4872--
4873jar
48743.n. [Well Workover and Intervention]
4875A downhole tool used to deliver an impact force to the tool string, usually to operate downhole tools or to dislodge a stuck tool string. Jars of different designs and operating principles are commonly included on slickline, coiled tubing and workover tool strings. Simple slickline jars incorporate an assembly that allows some free travel within the tool to gain momentum for the impact that occurs at the end of the stroke. Larger, more complex jars for coiled tubing or workover strings incorporate a trip or firing mechanism that prevents the jar from operating until the desired tension is applied to the string, thus optimizing the impact delivered. Jars are designed to be reset by simple string manipulation and are capable of repeated operation or firing before being recovered from the well.
4876None
4877None
4878None
4879--
4880jet hopper
48811.n. [Drilling Fluids]
4882A mud-flow device, also called a mud hopper, through which materials are put into the circulating mud system. The mud hopper is powered by acentrifugal pumpthat flows the mud at highvelocitythrough a venturi nozzle (jet) below the conical-shaped hopper. Dry materials are added through the mud hopper to provide dispersion, rapidhydrationand uniform mixing. Liquids are sometimes fed into the mud by a hose placed in the hopper.
4883mud hopper
4884None
4885None
4886--
4887junk
48881.n. [Drilling]
4889Anything in the wellbore that is not supposed to be there. The term is usually reserved for small pieces of steel such as hand tools, small parts, bit nozzles, pieces of bits or other downhole tools, and remnants of milling operations.
4890bridge, fish, junk basket, junk basket, mechanical sticking, mill, rathole, reverse circulation, sidetrack
4891None
4892None
4893--
4894jacking frame
48951.n. [Well Workover and Intervention]
4896A support structure used to stabilize the injector head and pressure-control equipment on some offshore, or special onshore, coiled tubing units. The jacking frame is hydraulically controlled to enable the injector head to be located at a safe and secure working height. Additional features, such as the ability to skid the injector head to the side for access to the wellbore are included in some of the more complex designs of jacking frame.
4897None
4898None
4899None
4900--
4901jet
49021.n. [Drilling]
4903A small-diameter tungsten carbide nozzle used in drill bits to produce a high-velocity drilling fluid stream exiting the bit.
4904bit
4905jet mixer
4906None
4907--
4908jet
49092.n. [Drilling]
4910The high-velocity fluid stream produced by the nozzles in the bit.
4911bit, bit nozzle
4912None
4913None
4914--
4915jet
49163.vb. [Drilling]
4917To drill soft, unconsolidated, usually shallow formations by eroding the "rock" below the bit by hydraulic impact loading alone. Though not as common as in the past, a bit may be fitted with asymmetric nozzles, one large and two or more small nozzles. If drillstring rotation is prevented during this jetting operation, the different nozzles tend to cause greater erosion on one side than the other, allowing the well to be intentionally deviated.
4918bit, bit nozzle, deviated hole
4919None
4920None
4921--
4922jet
49234.n. [Drilling]
4924A small-diameter nozzle used to mix cement.
4925None
4926jet mixer
4927None
4928--
4929jet nozzle
49301.n. [Drilling]
4931The part of the bit that includes a hole or opening for drilling fluid to exit. The hole is usually small (around 0.25 in. in diameter) and the pressure of the fluid inside the bit is usually high, leading to a high exit velocity through the nozzles that creates a high-velocity jet below the nozzles. This high-velocity jet of fluid cleans both the bit teeth and the bottom of the hole. The sizes of the nozzles are usually measured in 1/32-in. increments (although some are recorded in millimeters), are always reported in "thirty-seconds" of size (i.e., fractional denominators are not reduced), and usually range from 6/32 to 32/32.
4932circulation system, crossflow, differential pressure, exit velocity, hydraulic horsepower, jet, jet velocity
4933None
4934None
4935--
4936junk basket
49371.n. [Drilling]
4938A tool run into the wellbore to retrieve junk from the bottom of the hole.
4939junk
4940junk sub
4941basket sub
4942--
4943junk basket
49442.n. [Drilling]
4945A large, rectangular steel box, usually with sides made of expanded metal to facilitate seeing what is inside. The junk basket is used by the rig crew to store an assortment of relatively small parts of the drilling rig, ranging from drill bits to crossover subs to lifting subs to spare kellys. Dimensions vary, but a typical junk basket on a land rig is 8 ft wide [2.5 m] by 3 ft [1 m] deep by 30 ft [9 m] long.
4946junk, kelly, sub
4947None
4948None
4949--
4950jackup
49511.n. [Drilling]
4952A self-contained combination drilling rig and floating barge, fitted with long support legs that can be raised or lowered independently of each other. The jackup, as it is known informally, is towed onto location with its legs up and the barge section floating on the water. Upon arrival at the drilling location, the legs are jacked down onto the seafloor, preloaded to securely drive them into the seabottom, and then all three legs are jacked further down. Since the legs have been preloaded and will not penetrate the seafloor further, this jacking down of the legs has the effect of raising the jacking mechanism, which is attached to the barge and drilling package. In this manner, the entire barge and drilling structure are slowly raised above the water to a predetermined height above the water, so that wave, tidal and current loading acts only on the relatively small legs and not the bulky barge and drilling package.
4953bridge, mobile offshore drilling unit, Texas deck
4954None
4955None
4956--
4957jet cutter
49581.n. [Well Workover and Intervention]
4959A downhole tool, generally run on wireline or coiled tubing, that uses the detonation of a shaped explosive charge to cut the surrounding tubing or casing wall. The cutting action leaves a relatively clean cut surface, although the explosive action tends to flare the cut ends, making retrieval of cut tubular difficult if the fishing tool engages on the external surfaces.
4960None
4961None
4962None
4963--
4964joint
49651.n. [Geology]
4966A surface of breakage, cracking or separation within a rock along which there has been no movement parallel to the defining plane. The usage by some authors can be more specific: When walls of a fracture have moved only normal to each other, the fracture is called a joint.
4967fault, fracture
4968None
4969None
4970--
4971joint
49722.n. [Drilling]
4973A length of pipe, usually referring to drillpipe, casing or tubing. While there are different standard lengths, the most common drillpipe joint length is around 30 ft [9 m]. For casing, the most common length of a joint is 40 ft [12 m].
4974casing, casing string, connection, drillpipe, kelly down, make a connection
4975None
4976None
4977--
4978junk sub
49791.n. [Well Workover and Intervention]
4980A downhole tool with a profiled external surface designed to catch and retrieve junk or debris from the wellbore. The debris is carried up the tool-string annulus in the circulation fluid. An indented profile creating a larger annular area causes the fluid flow rate to drop and allows debris to drop into a basket or receptacle located at the base of the tool.
4981None
4982junk basket
4983None
4984--
4985jackup rig
49861.n. [Drilling]
4987A self-contained combination drilling rig and floating barge, fitted with long support legs that can be raised or lowered independently of each other. The jackup, as it is known informally, is towed onto location with its legs up and the barge section floating on the water. Upon arrival at the drilling location, the legs are jacked down onto the seafloor, preloaded to securely drive them into the seabottom, and then all three legs are jacked further down. Since the legs have been preloaded and will not penetrate the seafloor further, this jacking down of the legs has the effect of raising the jacking mechanism, which is attached to the barge and drilling package. In this manner, the entire barge and drilling structure are slowly raised above the water to a predetermined height above the water, so that wave, tidal and current loading acts only on the relatively small legs and not the bulky barge and drilling package.
4988bridge, mobile offshore drilling unit, Texas deck
4989None
4990None
4991--
4992kaolinite
49931.n. [Geology]
4994[Al4Si4O10(OH)8]A type of clay mineral from the kaolin group that forms through the weathering of feldspar and mica group minerals. Unlike some clay minerals like montmorillonite, kaolinite is not prone to shrinking or swelling with changes in water content.
4995clay, feldspar, mica, weathering
4996None
4997None
4998--
4999kaolinite
50002.n. [Drilling Fluids]
5001A common two-layer clay that does not swell when exposed to water. Kaolinite is used to make paper, pottery and bricks. It occurs naturally in shale and claystone, and therefore is a common component of drill solids in muds.
5002clay, clay-water interaction, methylene blue test
5003None
5004None
5005--
5006kerogen
50071.n. [Geology, Geochemistry, Shale Gas]
5008The naturally occurring, solid, insoluble organic matter that occurs in source rocks and can yield oil upon heating. Kerogen is the portion of naturally occurring organic matter that is nonextractable using organic solvents. Typical organic constituents of kerogen are algae and woody plant material. Kerogens have a high molecular weight relative to bitumen, or soluble organic matter. Bitumen forms from kerogen during petroleum generation. Kerogens are described as Type I, consisting of mainly algal and amorphous (but presumably algal) kerogen and highly likely to generate oil; Type II, mixed terrestrial and marine source material that can generate waxy oil; and Type III, woody terrestrial source material that typically generates gas.
5009gas-prone, geochemistry, hydrocarbon, oil-prone, petroleum system, source rock, vitrinite, vitrinite reflectance
5010None
5011None
5012--
5013kickoff
50141.n. [Drilling]
5015The point at which a vertical well is intentionally deviated.
5016None
5017None
5018None
5019--
5020kilogram per cubic meter
50211.n. [Drilling Fluids]
5022The SI unit of measurement for density. Mud weights are typically expressed in kg/m3. The conversion factor from lbm/gal to kg/m3 is 120. For example, 12 lbm/gal = 1440 kg/m3.
5023mud weight
5024None
5025None
5026--
5027kb
50281.n. [Drilling]
5029An adapter that serves to connect the rotary table to the kelly. The kelly bushing has an inside diameter profile that matches that of the kelly, usually square or hexagonal. It is connected to the rotary table by four large steel pins that fit into mating holes in the rotary table. The rotary motion from the rotary table is transmitted to the bushing through the pins, and then to the kelly itself through the square or hexagonal flat surfaces between the kelly and the kelly bushing. The kelly then turns the entire drillstring because it is screwed into the top of the drillstring itself. Depth measurements are commonly referenced to the KB, such as 8327 ft KB, meaning 8327 feet below the kelly bushing.
5030None
5031kelly bushing, rotary bushing
5032None
5033--
5034key stop
50351.n. [Production]
5036A method of restricting the travel of a ball valve from fully open to fully closed. The stem key bears against the ends of an arc machined in the adapter plate.
5037None
5038None
5039None
5040--
5041kill
50421.vb. [Drilling]
5043To stop a well from flowing or having the ability to flow into the wellbore. Kill procedures typically involve circulating reservoir fluids out of the wellbore or pumping higher density mud into the wellbore, or both. In the case of an induced kick, where the mud density is sufficient to kill the well but the reservoir has flowed as a result of pipe movement, the driller must circulate the influx out of the wellbore. In the case of an underbalanced kick, the driller must circulate the influx out and increase the density of the drilling fluid. In the case of a producing well, a kill fluid with sufficient density to overcome production of formation fluid is pumped into the well to stop the flow of reservoir fluids.
5044drillstem test, kick, mud, mud density, shear ram, snubbing, underbalanced, underground blowout
5045density
5046None
5047--
5048kinetic effect
50491.n. [Production Logging]
5050In a gradiomanometer tool, the pressure difference observed when the fluid velocity opposite the upper pressure sensor differs from that across the lower pressure sensor. This difference usually occurs opposite points of fluid entry or exit, and at sudden changes in diameter, such as at the tubing shoe. The result is a sharp deflection on the log that may be misinterpreted as a local change in fluid density.
5051fluid-density log, friction effect, holdup log
5052None
5053None
5054--