58YQFDXY

1a
21.n. [Formation Evaluation]
3The value a in the relation of formation factor (F) to porosity (phi): F = a / phim. The value a is derived empirically from best fits of measured values of F and phi on a group of rock samples. It has no clear physical significance, although it has been related to grain shape and tortuosity. In the saturation equation, it always occurs associated with the water resistivity as (a * Rw). It is sometimes claimed that a must be 1 since at phi = 1, F must be 1. However, a material with phi = 1 is not a rock: a is essentially an empirical factor for rocks and as such can take any value. A wide range of values has been found, from 0.5 to 5.
4Archie equation, porosity exponent
5None
6None
7--
82d survey
91.n. [Geophysics]
10Seismic data or a group of seismic lines acquired individually such that there typically are significant gaps (commonly 1 km or more) between adjacent lines. A 2D survey typically contains numerous lines acquired orthogonally to the strike of geological structures (such as faults and folds) with a minimum of lines acquired parallel to geological structures to allow line-to-line tying of the seismic data and interpretation and mapping of structures.
11acquisition, correlate, correlation, fault, fold, strike
12None
13None
14--
153d seismic data
161.n. [Geophysics]
17A set of numerous closely-spaced seismic lines that provide a high spatially sampled measure of subsurface reflectivity. Typical receiver line spacing can range from 300 m [1000 ft] to over 600 m [2000 ft], and typical distances between shotpoints and receiver groups is 25 m [82 ft] (offshore and internationally) and 110 ft or 220 ft [34 to 67 m] (onshore USA, using values that are even factors of the 5280 feet in a mile). Bin sizes are commonly 25 m, 110 ft or 220 ft. The resultant data set can be "cut" in any direction but still display a well sampled seismic section. The original seismic lines are called in-lines. Lines displayed perpendicular to in-lines are called crosslines. In a properly migrated 3D seismic data set, events are placed in their proper vertical and horizontal positions, providing more accurate subsurface maps than can be constructed on the basis of more widely spaced 2D seismic lines, between which significant interpolation might be necessary. In particular, 3D seismic data provide detailed information about fault distribution and subsurface structures. Computer-based interpretation and display of 3D seismic data allow for more thorough analysis than 2D seismic data.
18acquisition, bin, crossline, in-line, migration, two-dimensional seismic data
19None
20None
21--
224c seismic data
231.n. [Geophysics]
24Four-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.
25borehole seismic data, compressional wave, geophone, multicomponent seismic data, ocean-bottom cable, P-wave, shear wave
26None
27None
28--
29n
301.n. [Formation Evaluation]
31The exponent, n, in the relation of water saturation, Sw, to resistivity index, I (I = Sw-n) for a sample of rock. It expresses the effect on theresistivity of desaturating the sample, or replacing water with a non-conductive fluid. In petrophysically simple,water-wet rocks (Archie rocks), n is constant for different values of Sw, and a single average n can be found for a particularreservoir or formation. A typical value is 2. In more complex rocks, n changes with Sw, although often being about 2 near Sw = 1. In rocks with conductive minerals, such asshaly sands, n becomes increasingly lower as Sw is reduced. This change is negligible for high-salinity waters, but increases as the salinity is reduced. In shaly-sand saturation equations, such as Waxman-Smits, dual water, SGS and CRMM, n is the intrinsic n, determined with high-salinity water or with theclay effects removed. The variation of I with Sw is then predicted, with varying success, by the different equations. In carbonates with multiplepore types, such as fractures, vugs, interparticleporosity and microporosity, n may change as each pore type is desaturated. A different n may be used for a different range of Sw. In all cases, n increases if any pores are oil-wet. Values up to 8 have been reported in very oil-wet rocks.
32None
33None
34None
35--
363c seismic data
371.n. [Geophysics]
38A type of multicomponent seismic data acquired in a land, marine, or borehole environment by using three orthogonally oriented geophones or accelerometers. 3C is particularly appropriate when the addition of a hydrophone (the basis for 4C seismic data) adds no value to the measurement, as for example, on land. This technique allows determination of both the type of wave and its direction of propagation.
39accelerometer, geophone, hydrophone, multicomponent seismic data
40None
41None
42--
433d survey
441.n. [Geophysics]
45The acquisition of seismic data as closely spaced receiver and shot lines such that there typically are no significant gaps in the subsurface coverage. A 2D survey commonly contains numerous widely spaced lines acquired orthogonally to the strike of geological structures and a minimum of lines acquired parallel to geological structures to allow line-to-line correlation of the seismic data and interpretation and mapping of structures.
46acquisition, processing
47None
48None
49--
506ff40
511.adj. [Formation Evaluation]
52Referring to an induction log made with a particular array of transmitter and receiver coils. The array was introduced in 1960 and became the industry standard for 30 years. The 6FF40 array has six coils with the main transmitter-receiver pair spaced 40 in. [102 cm] apart. The design of the array includes the spacing between the coils, the number of turns and the polarity of each coil. The three transmitter and the three receiver coils are each connected in series to produce one signal output.FF means focused both radially and vertically. Unlike in an array tool, the focusing is fixed by the hardware design. The 6FF40 was designed to read deep into the formation while minimizing the signal close to the tool and maintaining reasonable vertical resolution. The 6FF40 was combined with a shallow electrode device to form the induction electrical survey. The use of both tools gave a qualitative indication of invasion.Both the deep induction and the 6FF40 had deconvolution and a skin effect correction applied. The deconvolution was designed to reduce the effect of shoulder beds on the readings in high-resistivity beds. It was not effective in high-contrast formations. The skin effect correction was a simple exponential fit that would work on an analog computer.
53array induction, deep induction, invasion, resistivity log, sonde error
54None
55None
56--
572d seismic data
581.n. [Geophysics]
59A vertical section of seismic data consisting of numerous adjacent traces acquired sequentially.
60trace
61None
62None
63--
642d seismic data
652.n. [Geophysics]
66A group of 2D seismic lines acquired individually, as opposed to the multiple closely spaced lines acquired together that constitute 3D seismic data.
67acquisition, three-dimensional seismic data, trace
68None
69None
70--
71a
721.n. [Formation Evaluation]
73The value a in the relation of formation factor (F) to porosity (phi): F = a / phim. The value a is derived empirically from best fits of measured values of F and phi on a group of rock samples. It has no clear physical significance, although it has been related to grain shape and tortuosity. In the saturation equation, it always occurs associated with the water resistivity as (a * Rw). It is sometimes claimed that a must be 1 since at phi = 1, F must be 1. However, a material with phi = 1 is not a rock: a is essentially an empirical factor for rocks and as such can take any value. A wide range of values has been found, from 0.5 to 5.
74Archie equation, porosity exponent
75None
76None
77--
78activity of aqueous solutions
791.n. [Drilling Fluids]
80The escaping tendency, or vapor pressure, of water molecules in an aqueous solution compared with that of pure water, typically abbreviated aw. Activity is expressed mathematically as the ratio of two vapor pressures: aw = p/po, where p is vapor pressure of the solution and po is vapor pressure of pure water. The ratio ranges from near 0 to 1.0 and corresponds to percent relative humidity (% RH) of air in equilibrium with the aqueous solution. For pure water, aw = po/po = 1.00 and RH = 100%. By increasing the concentration of salt (or other solutes) in the solution, aw decreases, because vapor pressure of the solution decreases. However, aw never reaches zero. Known-activity, saturated-salt solutions are used to calibrate RH meters. Measuring RH of air above an oil mud is a simple way to measure the activity (salinity) of its water phase. Adjusting the salinity of the water phase is a way to control movement of water into or out of shales that are being drilled with an oil mud. Chenevert related aw in oil mud to RH above the mud sample and devised a practical test using an electrohygrometer to measure RH, called the "Chenevert Method."
81balanced-activity oil mud, calcium chloride, humidity meter, hygrometer, inhibit, osmosis, osmotic pressure, shale, zinc chloride
82None
83None
84--
85amplitude distortion
861.n. [Geophysics]
87The inability of a system to exactly match input and output amplitude, a general example being an electronic amplifier and the classic example being a home stereophonic amplifier.
88bias, dispersion, distortion, dynamic range, harmonic distortion, zero-phase
89None
90None
91--
92amplitude distortion
932.n. [Geophysics]
94A change in the amplitude of awaveformthat is generally undesirable, such as inseismicwaves.
95distortion, seismic wave
96None
97None
98--
99array
1001.n. [Geophysics]
101Generally, a geometrical configuration of transducers (sources or receivers) used to generate or record a physical field, such as an acoustic or electromagnetic wavefield or the Earth's gravity field.
102fan shooting, footprint, ground roll, radial array, receiver, seismic trace, source, spread
103nest
104geophone array, geophone pattern, source pattern
105--
106array
1072.n. [Geophysics]
108A geometrical arrangement of seismic sources (a source array, with each individual source being activated in some fixed sequence in time) or receivers (a hydrophone or geophone array) that is recorded by one channel.
109geophone, hydrophone, receiver, source
110None
111None
112--
113array
1143.n. [Geophysics]
115An arrangement or configuration of electrodes or antennas used for resistivity, induced polarization (IP), or other types of electromagnetic surveying. Resistivity arrays typically consist of two current electrodes and two potential electrodes and are distinguished by the relative separations between the electrodes. Examples are the dipole-dipole, Schlumberger and Wenner arrays.
116dipole, electromagnetic method
117None
118None
119--
120array
1214.n. [Geophysics]
122In computing, code written to access data in more than one dimension according to a name and subscripts that correspond to each dimension.
123None
124None
125None
126--
127abandonment costs
1281.n. [Oil and Gas Business]
129The costs associated with abandoning a well or production facility. Such costs are specified in the authority for expenditure (AFE), and typically cover the plugging of wells; removal of well equipment, production tanks and associated installations; and surface remediation.
130authority for expenditure, plug and abandon
131None
132None
133--
134acyclic compound
1351.n. [Drilling Fluids]
136One of a group of organic compounds of carbon (C) and hydrogen (H) in which the carbon atoms have linear, branched chain (open), or both types of structures. Aliphatics, as they are informally called, can be divided into paraffinic (saturated) and olefinic (unsaturated) chain types. The simplest paraffinic aliphatic is methane, CH4. The simplest olefinic aliphatic is ethylene, C2H6. In drilling fluids, particularly oil-base muds, the amounts and types of hydrocarbon in the mud can be an important parameter in overall performance of the mud.
137aromatic hydrocarbon, naphthenic hydrocarbon, oil-base mud, soap
138aliphatic compound
139None
140--
141amplitude variation with offset
1421.n. [Geophysics]
143Variation in seismic reflection amplitude with change in distance between shotpoint and receiver that indicates differences in lithology and fluid content in rocks above and below the reflector. AVO analysis is a technique by which geophysicists attempt to determine thickness, porosity, density, velocity, lithology and fluid content of rocks. Successful AVO analysis requires special processing of seismic data and seismic modeling to determine rock properties with a known fluid content. With that knowledge, it is possible to model other types of fluid content. A gas-filled sandstone might show increasing amplitude with offset, whereas a coal might show decreasing amplitude with offset. A limitation of AVO analysis using only P-energy is its failure to yield a unique solution, so AVO results are prone to misinterpretation. One common misinterpretation is the failure to distinguish a gas-filled reservoir from a reservoir having only partial gas saturation ("fizz water"). However, AVO analysis using source-generated or mode-converted shear wave energy allows differentiation of degrees of gas saturation. AVO analysis is more successful in young, poorly consolidated rocks, such as those in the Gulf of Mexico, than in older, well-cemented sediments.
144attribute, cementation, converted wave, hydrocarbon indicator, lithostratigraphic inversion, P-wave, processing, seismic modeling
145None
146AVO
147--
148array induction
1491.n. [Formation Evaluation]
150An induction tool or log that consists of several mutually balanced arrays whose signals are recorded separately and combined in software to produce the response desired. Typically, there is one transmitter and five to ten pairs of receivers and bucking coils that are balanced to remove direct coupling. The signals are combined in a wide variety of ways to produce the responses desired, as for example, deep-reading, high vertical resolution or some combination of both. There are trade-offs in any response. For example, a deep-reading log typically will not have high vertical resolution. If it does, it will be more sensitive to the invasion condition and cave effect.
1516FF40, borehole correction, cave effect, forward modeling, induction, inversion, radial processing, resistivity log
152None
153None
154--
155abnormal pressure
1561.n. [Geology]
157A subsurface condition in which the pore pressure of a geologic formation exceeds or is less than the expected, or normal, formation pressure. When impermeable rocks such as shales are compacted rapidly, their pore fluids cannot always escape and must then support the total overlying rock column, leading to abnormally high formation pressures. Excess pressure, called overpressure or geopressure, can cause a well to blowout or become uncontrollable during drilling. Severe underpressure can cause the drillpipe to stick to the underpressured formation.
158compaction, geopressure gradient, geostatic pressure, hydrostatic pressure, normal pressure, pressure gradient
159None
160None
161--
162abnormal pressure
1632.n. [Drilling]
164Reservoir pore fluid pressure that is not similar to normal saltwater gradient pressure. The term is usually associated with higher than normal pressure, increased complexity for the well designer and an increased risk of well control problems. Pressure gradients in excess of around 10 pounds per gallon equivalent fluid density (0.52 psi/foot of depth) are considered abnormal. Gradients below normal are commonly called subnormal.
165barite, blowout, well control
166None
167None
168--
169adapter spool
1701.n. [Production]
171An extension added to a short face-to-face valve to conform to standard API 6D (or ISO 14313: 1999) face-to-face dimensions. API 6D specifies requirements and gives recommendations for the design, manufacturing, testing and documentation of ball, check, gate and plug valves for application in pipeline systems.
172API 6D: Specification for Pipeline Valves
173None
174None
175--
176anchor pin
1771.n. [Production]
178A pin welded to the body of a ball valve. This pin aligns the adapter plate and keeps the plate and gear operator from moving while the valve is being operated.
179ball valve
180None
181None
182--
183array laterolog
1841.n. [Formation Evaluation]
185An electrode device with multiple current electrodes configured in several different ways to produce several different responses. A typical array consists of a central electrode emitting survey current, with multiple guard electrodes above and below it. Current is sent between different guard electrodes to achieve greater or less focusing. The greater the focusing, the greater the depth of investigation. About five basic measurements are obtained in this way. This hardware focusing may be further improved by software focusing, in which the signals from the basic measurements are superimposed mathematically to ensure proper focusing in a wide range of conditions.
186electrode resistivity
187None
188None
189--
190abrasion test
1911.n. [Drilling Fluids]
192A laboratory test to evaluate drilling-grade weighting material for potential abrasiveness. The test measures weight loss of a specially shaped, stainless-steel mixer blade after 20 minutes at 11,000 rpm running in a laboratory-prepared mud sample. Abrasiveness is quantified by the rate of weight loss, reported in units of mg/min. Mineral hardness, particle size and shape are the main parameters that affect abrasiveness of weighting materials. Some crystalline forms of hematite grind to a higher percentage of large particles than do other forms and are therefore more abrasive. Hematites are harder than barites, grind courser and are more abrasive. Thus, a hematite that is proposed as a weighting material for mud is typically a candidate for abrasion testing.
193barite, ilmenite, iron oxide, particle-size distribution, sand test
194None
195None
196--
197additivity
1981.n. [Reservoir Characterization]
199A property of semivariogram models. Any linear combination of admissible models with positive coefficients can be nested or added together. Generally, single models are used for modeling experimental semivariograms that are close in shape to one of the basic admissible models, or for the approximate fitting of complex structural functions. Nested models are used to better fit complex structural functions.Reference:Olea RA: "Fundamentals of Semivariogram Estimation, Modeling, and Usage," in Yarus JM and Chambers RL (eds): Stochastic Modeling and Geostatistics, AAPG Computer Applications in Geology, no. 3. AAPG, Tulsa, Oklahoma, USA, 1994.
200None
201None
202None
203--
204angle of approach
2051.n. [Geophysics]
206The acute angle at which a wavefront impinges upon 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.
207refraction
208None
209None
210--
211array sonic
2121.n. [Formation Evaluation]
213A type of acoustic logging tool that uses a large number of receivers, typically 4 to 12. Modern acoustic logging tools are designed to measure not only the compressional wave but also the shear and other acoustic waves generated by the transmitter. The separation and identification of these waves are facilitated by the use of an array of receivers placed about 6 in. [15 cm] apart, which is close enough to avoid aliasing but far enough to sample a significant moveout in the wave. The waveforms at each receiver are recorded and processed by signal processing techniques, such as slowness-time coherence, to measure the velocities of the different waves.
214long-spacing sonic log, sonic log, sonic measurement
215None
216None
217--
218absolute age
2191.n. [Geology]
220The measurement of age in years. The determination of the absolute age of rocks, minerals and fossils, in years before the present, is the basis for the field of geochronology. The measurement of the decay of radioactive isotopes, especially uranium, strontium, rubidium, argon and carbon, has allowed geologists to more precisely determine the age of rock formations. Tree rings and seasonal sedimentary deposits called varves can be counted to determine absolute age. Although the term implies otherwise, "absolute" ages typically have some amount of potential error and are inexact. Relative age, in contrast, is the determination of whether a given material is younger or older than other surrounding material on the basis of stratigraphic and structural relationships, such as superposition, or by interpretation of fossil content.
221chronostratigraphy, geologic time scale, stratigraphy, varve
222None
223None
224--
225adjustable choke
2261.n. [Drilling]
227A valve usually used in well control operations to reduce the pressure of a fluid from high pressure in the closed wellbore to atmospheric pressure. It may be adjusted (opened or closed) to closely control the pressure drop. Adjustable choke valves are constructed to resist wear while high-velocity, solids-laden fluids are flowing by the restricting or sealing elements.
228choke, choke line, choke manifold, well control
229None
230None
231--
232adjustable choke
2332.n. [Well Completions]
234A valve, located on or near the Christmas tree that is used to control the production of fluid from a well. Opening or closing the variable valve influences the rate and pressure at which production fluids progress through the pipeline or process facilities. The adjustable choke is commonly linked to an automated control system to enable the production parameters of individual wells to be closely controlled.
235choke
236None
237None
238--
239angle of incidence
2401.n. [Geophysics]
241The 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.
242angle of approach, critical reflection, head wave, raypath, refraction, refractive index, refractor, Zoeppritz equations
243None
244None
245--
246artificial intelligence
2471.n. [Reservoir Characterization]
248The study of ideas that enable computers to do the things that make people seem intelligent. The term is commonly abbreviated as A.I. Many computer programs written for use in the oil field utilize "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 real problems. Most such programs are limited to specific areas such as dipmeter interpretation, electrofacies determination, reservoir characterization, blowout prevention, drilling fluid selection, etc. Sometimes expert systems are written in computer languages that easily handle "rules" such as LISP, but once fully tested are usually translated to BASIC, C or FORTRAN to be compiled into efficient applications or programs..
249neural networks
250None
251None
252--
253absolute filter
2541.n. [Well Workover and Intervention]
255A type of high-specification fluid filter frequently used to remove small solid particles from workover or treatment fluids that may be injected into, or placed adjacent to, the reservoir formation. In using absolute filters, all particles larger than the micron rating of the filter element in use will be removed from the treated fluid.
256filtration, nominal filter
257None
258None
259--
260adsorbed gas
2611.n. [Shale Gas]
262The gas accumulated on the surface of a solid material, such as a grain of a reservoir rock, or more particularly the organic particles in a shale reservoir. Measurement of adsorbed gas and interstitial gas, which is the gas contained in pore spaces, allows calculation of gas in place in a reservoir.
263None
264None
265None
266--
267aniline point test
2681.n. [Drilling Fluids]
269A test to evaluate base oils that are used in oil mud. The test indicates if an oil is likely to damage elastomers (rubber compounds) that come in contact with the oil. The aniline point is called the "aniline point temperature," which is the lowest temperature (°F or °C) at which equal volumes of aniline (C6H5NH2) and the oil form a single phase. The aniline point (AP) correlates roughly with the amount and type of aromatic hydrocarbons in an oil sample. A low AP is indicative of higher aromatics, while a high AP is indicative of lower aromatics content. Diesel oil with AP below 120°F [49°C] is probably risky to use in oil-base mud. The API has developed test procedures that are the standard for the industry.
270amines, aromatic hydrocarbon, diesel-oil mud, oil-base mud, synthetic-base fluid
271None
272None
273--
274asme
2751.n. [Production]
276Abbreviation for the American Society of Mechanical Engineers, a professional association that was founded in 1880.It "promotes the art, science, and practice of multidisciplinary engineering and allied sciences around the globe" via "continuing education, training and professional development, codes and standards, research, conferences and publications, government relations, and other forms of outreach.” The ASME develops codes and standards associated with the art, science, and practice of mechanical engineering that are accepted in more than 100 countries.
277None
278None
279None
280--
281absolute open flow potential
2821.n. [Production Testing]
283The maximum flow rate a well could theoretically deliver with zero pressure at the middle of the perforations. The term is commonly abbreviated as AOFP or OFP.
284None
285None
286AOFP
287--
288aeolian
2891.adj. [Geology]
290Pertaining 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.
291clay, depositional environment, depositional system, sabkha, sandstone, sediment
292eolian
293None
294--
295anion
2961.n. [Drilling Fluids]
297A negatively charged ion. Clay surfaces, groups on polymer chains, colloids and other materials have distinct, negatively charged areas or ions. Anionic characteristics affect performance of additives and contaminants in drilling fluids, especially water muds, in which clays and polymers are used extensively.
298acrylate polymer, calcium contamination, carbonate ion, cation-exchange capacity, clay, colloid, mixed-metal hydroxide, polar compound, potassium ion
299anionic, water mud
300Antonyms:cation
301--
302asphalt
3031.n. [Geology]
304A solid or nearly solid form of bitumen that can melt upon heating and contains impurities such as nitrogen, oxygen and sulfur. Asphalt forms naturally when the light components or volatiles of petroleum have been removed or evaporated.
305hydrocarbon, invert-emulsion oil mud, tar sand
306None
307None
308--
309absolute volume
3101.n. [Drilling Fluids]
311The volume a solid occupies or displaces when added to water divided by its weight, or the volume per unit mass. In the oil field, absolute volume is typically given in units of gallons per pound (gal/lbm) or cubic meters per kilogram (m3/kg).
312None
313None
314None
315--
316aeolotropy
3171.n. [Geology, Geophysics, Shale Gas]
318Predictable variation of a property of a material with the direction in which it is measured, which can occur at all scales. For a crystal of a mineral, variation in physical properties observed in different directions is aeolotropy (also known as anisotropy). In rocks, variation in seismic velocity measured parallel or perpendicular to bedding surfaces is a form of aeolotropy.Often found where platy minerals such as micas and clays align parallel to depositional bedding as sediments are compacted, aeolotropy is common in shales.
319birefringence, extensive dilatancy anisotropy, heterogeneous formation, raypath, seismic velocity, velocity
320anisotropy
321Antonyms:isotropy
322--
323anionic
3241.adj. [Drilling Fluids]
325Related to negatively charged ions. Clay surfaces, groups onpolymer chains, colloids and other materials have distinct, negatively charged areas or ions. Anionic characteristics affect performance of additives and contaminants in drilling fluids, especially water muds, in which clays and polymers are used extensively.
326acrylate polymer, anion, calcium contamination, carbonate ion, cation-exchange capacity, clay, colloid, mixed-metal hydroxide, polar compound, potassium ion, sulfonated asphalt, water mud
327None
328Antonyms:cationic
329--
330asphaltene precipitation
3311.n. [Enhanced Oil Recovery]
332The flocculation of asphaltene particles from reservoir fluid. The precipitation is typically measured at specific conditions of temperature and pressure, such as at reservoir or flowline conditions.
333asphaltenes
334None
335None
336--
337absorbing boundary conditions
3381.n. [Geophysics]
339An algorithm used in numerical simulation along the boundary of a computational domain to absorb all energy incident upon that boundary and to suppress reflection artifacts.
340domain
341None
342None
343--
344aerated layer
3451.n. [Geology, Geophysics]
346The surface or near-surface, unconsolidated sedimentary layer that has been subject to weathering and whose pores are air-filled instead of liquid-filled. An aerated layer typically has a low seismic velocity.
347pore, static correction, weathering, weathering correction
348None
349None
350--
351anisotropic
3521.adj. [Geophysics, Geology, Shale Gas]
353Having directionally dependent properties. For a crystal of amineral, variation in physical properties observed in different directions is anisotropy. In rocks, variation in seismic velocity measured parallel or perpendicular to bedding surfaces is a form of anisotropy.Often found where platy minerals such as micas and clays align parallel to depositional bedding as sediments are compacted, anisotropy is common in shales.
354aeolotropy, anisotropic formation, anisotropy, birefringence, extensive dilatancy anisotropy, heterogeneous formation, raypath, seismic velocity, velocity
355None
356Antonyms:isotropic
357--
358asphaltic mud additive
3591.n. [Drilling Fluids]
360A group of high-viscosity or solid hydrocarbons obtained from naturally occurring deposits or from the residue of petroleum refining, commonly used as additives for oil-base and water-base muds. Molten asphalt can be further processed by heating and passing air through the melt to oxidize and polymerize its components. Cooled, air-blown asphalt is glassy and can be ground. It has a high softening point and polar sites that offer emulsion-stabilizing qualities and affinity for clays and shales.
361polar compound, sulfonated asphalt
362None
363None
364--
365absorption
3661.n. [Geophysics]
367The conversion of one form of energy into another as the energy passes through a medium. For example, seismic waves are partially converted to heat as they pass through rock.
368absorption band, attenuation, Q, wave
369None
370None
371--
372absorption
3732.n. [Production Facilities]
374The property of some liquids or solids to soak up water or other fluids. The natural gas dehydration process uses glycols (liquids) that absorb the water vapor to finally obtain dehydrated gas. In the same way, light oil, also called absorption oil, is used to remove the heavier liquid hydrocarbons from a wet gas stream to obtain dry gas.
375adsorption, dehydrate, desiccant, glycol, glycol dehydrator, natural gas
376None
377None
378--
379afe
3801.n. [Oil and Gas Business]
381A budgetary document, usually prepared by the operator, to list estimated expenses of drilling a well to a specified depth, casing point or geological objective, and then either completing or abandoning the well. Such expenses may include excavation and surface site preparation, the daily rental rate of a drilling rig, costs of fuel, drillpipe, bits, casing, cement and logging, and coring and testing of the well, among others. This estimate of expenses is provided to partners for approval prior to commencement of drilling or subsequent operations. Failure to approve an authority for expenditure (AFE) may result in delay or cancellation of the proposed drilling project or subsequent operation.
382None
383None
384authority for expenditure
385--
386anisotropic formation
3871.n. [Well Testing]
388A formation with directionally dependent properties. The most common directionally dependent properties are permeability and stress. Most formations have vertical to horizontal permeability anisotropy with vertical permeability being much less (often an order of magnitude less) than horizontal permeability. Bedding plane permeability anisotropy is common in the presence of natural fractures. Stress anisotropy is frequently greatest between overburden stress and horizontal stress in the bedding plane. Bedding plane stress contrasts are common in tectonically active regions. Permeability anisotropy can sometimes be related to stress anisotropy.
389directional permeability, rock mechanics
390None
391Antonyms:isotropic formation
392--
393assignment
3941.n. [Oil and Gas Business]
395The sale, transfer or conveyance of all or a fraction of ownership interest or rights owned in real estate or other such property. The term is commonly used in the oil and gas business to convey working interest, leases, royalty, overriding royalty interest and net profits interest.
396conveyance
397None
398None
399--
400absorption oil
4011.n. [Production Facilities]
402A light liquid hydrocarbon used to absorb or remove the heavier liquid hydrocarbons from a wet gas stream. Absorption oil is also called wash oil.
403None
404None
405None
406--
407agc
4081.n. [Geophysics]
409Abbreviation for automatic gain control. A system to automatically control the gain, or the increase in the amplitude of an electrical signal from the original input to the amplified output. AGC is commonly used in seismic processing to improve visibility of late-arriving events in which attenuation or wavefront divergence has caused amplitude decay.
410None
411None
412automatic gain control
413--
414anisotropy
4151.n. [Geophysics, Shale Gas, Geology]
416Predictable variation of a property of a material with the direction in which it is measured, which can occur at all scales. For a crystal of a mineral, variation in physical properties observed in different directions is anisotropy. In rocks, variation in seismic velocity measured parallel or perpendicular to bedding surfaces is a form of anisotropy.Often found where platy minerals such as micas and clays align parallel to depositional bedding as sediments are compacted, anisotropy is common in shales.
417anisotropic, anisotropic formation, birefringence, extensive dilatancy anisotropy, heterogeneous formation, raypath, seismic velocity, velocity
418aeolotropy
419Antonyms:isotropy
420--
421atmospheric corrosion
4221.n. [Well Completions]
423Corrosion (oxidization) resulting from exposure of susceptible materials to oxygen and moisture. Atmospheric corrosion is generally associated with surface storage conditions, or with upper wellbore annuli that may not be fluid-filled.
424None
425None
426None
427--
428accretion
4291.n. [Drilling Fluids]
430The mechanism by which partially hydrated cuttings stick to parts of the bottomhole assembly and accumulate as a compacted, layered deposit.
431None
432None
433None
434--
435agc time constant
4361.n. [Geophysics]
437The exponential rate constant (τ) that determines how quickly the output amplitude of an electrical signal that is under automatic gain control (AGC) responds to a sudden increase or decrease in input signal amplitude. Mathematically,Af(t) = Ai(t) + ΔAi (1 − e−t/τ) where Af is the output signal amplitude, Ai is the input signal amplitude (Ai), ΔAi is the change in input signal amplitude and t is time. When t equals τ, the function (1−e−t/τ) equals (1−1/e) equals 0.63. Therefore, the AGC time constant (τ) is the amount of time that elapses for the output signal of AGC to reflect 63% of the change in the input signal amplitude.
438automatic gain control, AGC
439None
440None
441--
442annular blowout preventer
4431.n. [Drilling]
444A large valve used to control wellbore fluids. In this type of valve, the sealing element resembles a large rubber doughnut that is mechanically squeezed inward to seal on either pipe (drill collar, drillpipe, casing, or tubing) or the openhole. The ability to seal on a variety of pipe sizes is one advantage the annular blowout preventer has over the ram blowout preventer. Most blowout preventer (BOP) stacks contain at least one annular BOP at the top of the BOP stack, and one or more ram-type preventers below. While not considered as reliable in sealing over the openhole as around tubulars, the elastomeric sealing doughnut is required by API specifications to seal adequately over the openhole as part of its certification process.
445blowout preventer, snubbing, stripping
446annular BOP
447None
448--
449attapulgite
4501.n. [Drilling Fluids]
451A needle-like clay mineral composed of magnesium-aluminum silicate. Major deposits occur naturally in Georgia, USA. Attapulgite and sepiolite have similar structures and both can be used in saltwater mud to provide low-shear rate viscosity for lifting cuttings out of the annulus and for barite suspension. Attapulgite and sepiolite are sometimes called "salt gel." Attapulgite has no capability to control the filtration properties of the mud. For use as an oil mud additive, the clay is coated with quaternary amine, which makes it oil-dispersible and provides gel structure but does not improve the filter cake, unlike organophilic bentonite clay.
452barite, clay, cuttings, gel, oil mud, organophilic clay, quaternary amine, shear rate
453None
454None
455--
456accumulator
4571.n. [Production, Well Workover and Intervention]
458A 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.
459hydraulic power unit
460None
461None
462--
463agglomeration
4641.n. [Drilling Fluids]
465The formation of groups or clusters of particles (aggregates) in a fluid. In water or in water-base drilling fluid, clay particles form aggregates in a dehydrated, face-to-face configuration. This occurs after a massive influx of hardness ions into freshwater mud or during changeover to a lime mud or gyp mud. Agglomeration results in drastic reductions in plastic viscosity, yield point and gel strength. It is part of wastewater cleanup and water clarification. Alum or polymers cause colloidal particles to aggregate, allowing easier separation.
466clay, clay-water interaction, colloidal solids, dewatering, dispersion, flocculation, greasing out, wastewater cleanup
467aggregation
468None
469--
470annular bop
4711.n. [Drilling]
472A large valve used to control wellbore fluids. In this type of valve, the sealing element resembles a large rubber doughnut that is mechanically squeezed inward to seal on either pipe (drill collar, drillpipe, casing, or tubing) or the openhole. The ability to seal on a variety of pipe sizes is one advantage the annular blowout preventer has over the ram blowout preventer. Most blowout preventer (BOP) stacks contain at least one annular BOP at the top of the BOP stack, and one or more ram-type preventers below. While not considered as reliable in sealing over the openhole as around tubulars, the elastomeric sealing doughnut is required by API specifications to seal adequately over the openhole as part of its certification process.
473blowout preventer, snubbing, stripping
474annular blowout preventer
475None
476--
477attenuation
4781.n. [Geophysics]
479The loss of energy or amplitude of waves as they pass through media. Seismic waves lose energy through absorption, reflection and refraction at interfaces, mode conversion and spherical divergence, or spreading of the wave.
480amplitude, converted wave, Fresnel zone, Q, suppression, true-amplitude recovery, wave
481None
482attenuate
483--
484attenuation
4852.n. [Formation Evaluation]
486The reduction in amplitude of an electromagnetic wave passing through the formation, usually measured in decibels/meter, dB/m. The term is used in particular with reference to the propagation resistivity log and the electromagnetic propagation log.
487attenuation resistivity, decibel, electromagnetic propagation measurement, propagation resistivity measurement
488None
489None
490--
491acetic acid
4921.n. [Well Completions, Drilling Fluids, Well Workover and Intervention]
493An organic acid used in oil- and gas-well stimulation treatments. Less corrosive than the commonly used hydrochloric acid, acetic acid treatments can be more easily inhibited or retarded for treatments of long duration. This is necessary particularly in applications requiring the protection of exotic alloys or in high-temperature wells. In most cases, acetic acid is used in conjunction with hydrochloric acid and other acid additives. It can also be used as a chelating agent.
494inhibit, retarder
495None
496None
497--
498aggregate
4991.n. [Drilling Fluids]
500Group or cluster of particles in a fluid. In water or in water-base drilling fluid, clay particles form aggregates in a dehydrated, face-to-face configuration. This occurs after a massive influx of hardness ions into freshwater mud or during changeover to a lime mud or gyp mud. Aggregation results in drastic reductions in plastic viscosity, yield point and gel strength. It is part of wastewater cleanup and water clarification. Alum or polymers cause colloidal particles to aggregate, allowing easier separation.
501agglomeration, aggregation, clay, clay-water interaction, colloidal solids, dewatering, dispersion, flocculation, greasing out, wastewater cleanup
502None
503None
504--
505annular flow
5061.n. [Production Logging]
507A multiphase flow regime in which the lighter fluid flows in the center of the pipe, and the heavier fluid is contained in a thin film on the pipe wall. The lighter fluid may be a mist or an emulsion. Annular flow occurs at high velocities of the lighter fluid, and is observed in both vertical and horizontal wells. As the velocity increases, the film may disappear, leading to mist flow or emulsion flow. When the interface between the fluids is irregular, the term wavy annular flow may be used.
508churn flow, flow structure, froth flow
509None
510None
511--
512attenuation resistivity
5131.n. [Formation Evaluation]
514The ability of a formation to resist electrical conduction, as derived from the reduction in amplitude of the electromagnetic wave generated in a propagation resistivity measurement. At the frequencies used and within the range of measurement, the attenuation depends almost solely on the resistivity, so that the former can be transformed to the latter with a simple algorithm. The transform also depends on transmitter/receiver spacings and tool design. For a 2-MHz measurement, a typical measurement range is 0.2 to 50 ohm-m. Above 50 ohm-m, the dependence of attenuation on resistivity is too small to measure accurately.
515dielectric resistivity, phase-shift resistivity, polarization horn, propagation resistivity, resistivity log
516None
517None
518--
519acid
5201.adj. [Drilling Fluids]
521Pertaining to an aqueous solution, such as a water-base drilling fluid, which has more hydrogen ions (H+) than hydroxyl ions (OH-) and pH less than 7.
522acidity
523None
524Antonyms:alkaline
525--
526acid
5272.n. [Well Workover and Intervention]
528A generic term used to describe a treatment fluid typically comprising hydrochloric acid and a blend of acid additives. Acid treatments are commonly designed to include a range of acid types or blends, such as acetic, formic, hydrochloric, hydrofluoric and fluroboric acids. Applications for the various acid types or blends are based on the reaction characteristics of the prepared treatment fluid.
529acetic acid, acidity, formic acid, hydrofluoric acid
530None
531None
532--
533aggregation
5341.n. [Drilling Fluids]
535The formation of groups or clusters of particles (aggregates) in a fluid. In water or in water-base drilling fluid, clay particles form aggregates in a dehydrated, face-to-face configuration. This occurs after a massive influx of hardness ions into freshwater mud or during changeover to a lime mud or gyp mud. Aggregation results in drastic reductions in plastic viscosity, yield point and gel strength. It is part of wastewater cleanup and water clarification. Alum or polymers cause colloidal particles to aggregate, allowing easier separation.
536aggregate, clay, clay-water interaction, colloidal solids, dewatering, dispersion, flocculation, greasing out, wastewater cleanup
537agglomeration
538None
539--
540annular gas flow
5411.n. [Drilling]
542A flow of formation gas in the annulus between a casing string and the borehole wall. Annular gas flows occur when there is insufficient hydrostatic pressure to restrain the gas. They can occur in uncemented intervals and even in cemented sections if the cement bond is poor. After cementing, as the cement begins to harden, a gel-like structure forms that effectively supports the solid material in the cement slurry. However, during this initial gelling period, the cement has no appreciable strength. Hence, with the solid (weighting) material now supported by the gel structure, the effective density of the slurry that the reservoir experiences falls rather suddenly to the density of the mix water of the cement, which is usually fresh water, whose density is 8.34 lbm/gal, or a gradient of 0.434 psi/ft of vertical column height. Various chemical additives have been developed to reduce annular gas flow.
543cement
544None
545None
546--
547audio measurement
5481.n. [Production Logging]
549A technique for recording sound at different positions in the borehole to generate a noise log. The measurement technique uses a microphone to record signals in the audible range approximately 20 to 20,000 Hz . In some circumstances, the frequency of the signal can be related to the source of noise and the flow regime, while the amplitude of the signal can be related to the flow rate. The useful signal lies approximately between 100 and 5000 Hz, with lower frequencies generally representing background and mechanical noise. The measurement may record the total signal over all frequencies, the signal at a single frequency, or consist of a set of measurements over different frequency ranges.
550flowmeter, production log
551None
552None
553--
554acid job
5551.n. [Well Workover and Intervention, Well Completions]
556The treatment of a reservoir formation with a stimulation fluid containing a reactive acid. In sandstone formations, the acid reacts with the soluble substances in the formation matrix to enlarge the pore spaces. In carbonate formations, the acid dissolves the entire formation matrix. In each case, the matrix acidizing treatment improves the formation permeability to enable enhanced production of reservoir fluids. Matrix acidizing operations are ideally performed at high rate, but at treatment pressures below the fracture pressure of the formation. This enables the acid to penetrate the formation and extend the depth of treatment while avoiding damage to the reservoir formation.
557matrix, stimulation fluid
558acid stimulation, acidize, acidizing, matrix acidizing, matrix stimulation
559None
560--
561air cut mud
5621.n. [Drilling Fluids, Drilling]
563A 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 driller 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.
564derrickman, drilling fluid
565gas-cut mud
566None
567--
568annular velocity
5691.n. [Drilling]
570The speed at which drilling fluid or cement moves in the annulus. It is important to monitor annular velocity to ensure that the hole is being properly cleaned of cuttings, cavings and other debris while avoiding erosion of the borehole wall. The annular velocity is commonly expressed in units of feet per minute or, less commonly, meters per minute. The term is distinct from volumetric flow.
571None
572None
573AV
574--
575annular velocity
5762.n. [Well Completions]
577The linear velocity of a fluid passing through an annular space. The term critical annular velocity is often used to describe the flow rate or velocity at which entrained solids will be efficiently transported by the annular fluid. If the fluid velocity falls below the critical rate, there will be a risk of particles settling, forming beds or bridges that may obstruct the wellbore.
578None
579None
580None
581--
582aulacogen
5831.n. [Geology]
584In plate tectonics, a failed rift arm. At the junctions of tectonic plates, three intersecting lithospheric plates typically are separated by "arms." Arms might be areas of rifting, convergence or transform faults (similar to a strike-slip fault). The arm along which the motion that spreads the plates apart ceases is termed the failed arm, or aulacogen. Spreading or rifting along the other arms of the triple junction can form new oceanic basins, whereas the aulacogen can become a sediment-filled graben.
585fault, lithosphere, plate tectonics, transform fault
586None
587None
588--
589acid stimulation
5901.n. [Well Completions, Well Workover and Intervention]
591The treatment of a reservoir formation with a stimulation fluid containing a reactive acid. In sandstone formations, the acid reacts with the soluble substances in the formation matrix to enlarge the pore spaces. In carbonate formations, the acid dissolves the entire formation matrix. In each case, the matrix acidizing treatment improves the formation permeability to enable enhanced production of reservoir fluids. Matrix acidizing operations are ideally performed at high rate, but at treatment pressures below the fracture pressure of the formation. This enables the acid to penetrate the formation and extend the depth of treatment while avoiding damage to the reservoir formation.
592matrix, stimulation fluid
593acid job, acidize, acidizing, matrix acidizing, matrix stimulation
594None
595--
596air drill
5971.vb. [Drilling]
598To drill using gases (typically compressed air or nitrogen) to cool the drill bit and lift cuttings out of the wellbore, instead of the more conventional use of liquids. The advantages of air drilling are that it is usually much faster than drilling with liquids and it may eliminate lost circulation problems. The disadvantages are the inability to control the influx of formation fluid into the wellbore and the destabilization of the borehole wall in the absence of the wellbore pressure typically provided by liquids.
599lost circulation, mist drilling
600None
601None
602--
603annulus
6041.n. [Drilling]
605The space between two concentric objects, such as between the wellbore and casing or between casing and tubing, where fluid can flow. Pipe may consist of drill collars, drillpipe, casing or tubing.
606annular velocity, bridge, casing centralizer, cement, cementing, crossflow, displacement, drill collar, eccentricity, flapper valve, pack off
607None
608annuli
609--
610annulus
6112.n. [Formation Evaluation]
612With reference to invasion, a region between the flushed zone and the undisturbed zone containing a buildup of formation water. The annulus forms during invasion and is caused by the different mobilities of oil and water. It only occurs in the presence of both, but is unstable and will dissipate vertically or horizontally with time. The annulus has approximately the same water saturation as the flushed zone but contains formation water. When the formation water is much more saline than the mud filtrate, the annulus forms a conductive ring around the borehole.This conductivity will cause an induction log to read too low a resistivity, by an amount that depends on its depth of investigation and the radius of the annulus. (Laterologs are little affected since they respond to resistivity, not conductivity.) Often a medium log will be more affected than a deep log so that an annulus can be detected by out-of-order curves (medium curves reading less than either shallow or deep). Array induction logs contain enough information to solve and correct for the effect of the annulus.
613depth of invasion, transition zone, undisturbed zone
614None
615None
616--
617annulus
6183.n. [Well Testing]
619The space between two concentric pipe strings, such as between the production tubing and casing in a well. The term may also refer to the space between a pipe string and the borehole wall in an openhole completion or openhole drillstem test (DST).
620None
621None
622None
623--
624authority for expenditure
6251.n. [Oil and Gas Business]
626A budgetary document, usually prepared by the operator, to list estimated expenses of drilling a well to a specified depth, casing point or geological objective, and then either completing or abandoning the well. Such expenses may include excavation and surface site preparation, the daily rental rate of a drilling rig, costs of fuel, drillpipe, bits, casing, cement and logging, and coring and testing of the well, among others. This estimate of expenses is provided to partners for approval prior to commencement of drilling or subsequent operations. Failure to approve an authority for expenditure (AFE) may result in delay or cancellation of the proposed drilling project or subsequent operation.
627casing point
628None
629AFE
630--
631acid tank
6321.n. [Well Workover and Intervention]
633The rubber-lined vessel used to transport raw or concentrated acid to the wellsite. Some acid additives attack or degrade rubber. Consequently, acid treatment fluids are not generally mixed or transported in acid tanks, but are instead mixed in special batch tanks or continuously mixed as the treatment is pumped.
634treatment fluid
635None
636None
637--
638air drilling
6391.n. [Drilling]
640A drilling technique whereby gases (typically compressed air or nitrogen) are used to cool the drill bit and lift cuttings out of the wellbore, instead of the more conventional use of liquids. The advantages of air drilling are that it is usually much faster than drilling with liquids and it may eliminate lost circulation problems. The disadvantages are the inability to control the influx of formation fluid into the wellbore and the destabilization of the borehole wall in the absence of the wellbore pressure typically provided by liquids.
641lost circulation, mist drilling
642None
643None
644--
645anode
6461.n. [Drilling Fluids]
647The half of a battery that is positively charged and to which anions migrate by electrostatic attraction. Half of an electrolytic corrosion cell in metal is called the "anode," from which metal dissolves, often leaving pits. The anode is the part of a corrosion cell in which oxidation occurs.
648sacrificial anode
649None
650Antonyms:cathode
651--
652anode
6532.n. [Drilling Fluids]
654A protective device to prevent electrolytic corrosion. Anodes (often made of Mg or Al metal) are sacrificed intentionally to protect a steel system, such as a buried pipeline or offshore platform.
655corrosion coupon
656sacrificial anode
657None
658--
659autochthon
6601.n. [Geology]
661Materials, especially rock masses, that formed in their present location and have not been transported. Fault surfaces can separate indigenous rocks from allochthonous rocks, although some allochthonous rocks are clearly delineated by their differing composition.
662autochthonous
663None
664Antonyms:allochthon
665--
666acid wash
6671.n. [Well Workover and Intervention]
668A wellbore acid treatment designed to remove scale or similar deposits from perforations and well-completion components. Acid-wash treatments generally do not include injection of treatment fluid into the reservoir formation.
669perforation
670None
671None
672--
673air shooting
6741.n. [Geophysics]
675A method of seismic acquisition using charges detonated in the air or on poles above the ground as the source. Air shooting is also called the Poulter method after American geophysicist Thomas Poulter.
676dynamite, shot depth, source
677None
678None
679--
680antithetic fault
6811.n. [Geology]
682A minor, secondary fault, usually one of a set, whose sense of displacement is opposite to its associated major and synthetic faults. Antithetic-synthetic fault sets are typical in areas of normal faulting.
683normal fault
684None
685Antonyms:synthetic fault
686--
687autochthonous
6881.adj. [Geology]
689Materials, especially rock masses, that formed in their present location and have not been transported. Fault surfaces can separate indigenous rocks from allochthonous rocks, although some allochthonous rocks are clearly delineated by their differing composition.
690autochthon
691None
692Antonyms:allochthonous
693--
694acoustic
6951.adj. [Geophysics]
696Pertaining to sound. Generally, acoustic describes sound or vibrational events, regardless of frequency. The term sonic is limited to frequencies and tools operated in the frequency range of 1 to 25 kilohertz.
697acoustic coupler, acoustic log, bel, decibel, elastic wave, hertz, side-scan sonar, synthetic seismogram, transit time, velocity
698None
699None
700--
701acoustic
7022.adj. [Geophysics]
703In geophysics, acoustic refers specifically to P-waves in the absence of S-waves (i.e., in fluids, which do not support S-waves, or in cases in which S-waves in solids are ignored).
704P-wave, S-wave
705None
706None
707--
708air cut mud
7091.n. [Drilling, Drilling Fluids]
710A 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 driller 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.
711derrickman, drilling fluid
712gas-cut mud
713None
714--
715antiwhirl bit
7161.n. [Drilling]
717A drill bit, usually polycrystalline diamond compact bit (PDC) type, designed such that the individual cutting elements on the bit create a net imbalance force. This imbalance force pushes the bit against the side of the borehole, which in turn creates a stable rotating condition that resists backwards whirling, wobbling and downhole vibration. Antiwhirl bits allow faster rates of penetration, yet achieve longer bit life than more conventional bits, which are not dynamically biased to run smoothly, are inherently unstable, are vibration-prone and thus have shorter lives. No bit is whirl-proof, however.
718bit, bottomhole assembly, drilling rate, PDC bit, roller-cone bit
719None
720None
721--
722automatic gain control
7231.n. [Geophysics]
724A system to control the gain, or the increase in the amplitude of an electrical signal from the original input to the amplified output, automatically. AGC is commonly used in seismic processing to improve visibility of late-arriving events in which attenuation or wavefront divergence has caused amplitude decay.
725event, processing, Q
726None
727AGC, AGC time constant
728--
729acoustic log
7301.n. [Geophysics]
731A display of traveltime of acoustic waves versus depth in a well. The term is commonly used as a synonym for a sonic log. Some acoustic logs display velocity.
732acoustic wave, depth conversion, interval transit time, interval velocity, velocity survey
733acoustic velocity log
734None
735--
736acoustic log
7372.n. [Formation Evaluation]
738A record of some acoustic property of the formation or borehole. The term is sometimes used to refer specifically to the sonic log, in the sense of the formation compressional slowness. However, it may also refer to any other sonic measurement, for example shear, flexural and Stoneley slownesses or amplitudes, or to ultrasonic measurements such as the borehole televiewer and other pulse-echo devices, and even to noise logs.
739acoustic mode, flexural mode, interval transit time, noise log, Stoneley wave
740None
741None
742--
743alford rotation
7441.n. [Formation Evaluation]
745A processing technique to project formation shear data recorded in any two orthogonal directions into the fast and slow shear directions in the presence of shear-wave anisotropy. In the sonic logging application, a dipole transmitter excites a flexural mode that is recorded at one set of receivers that is in-line with the dipole and other receivers that are 90o out of line (the cross-dipole component). A similar recording is made of the wave from a second dipole transmitter, mounted orthogonally to the first. The flexural-wave velocity is closely related to the formation shear velocity, particularly at low frequencies and in hard formations. Using all four waveforms, the Alford rotation is used to determine the speed and direction of the fast and the slow shear wave. Reference: Alford RM: "Shear Data in the Presence of Azimuthal Anisotropy: Dilley, Texas," Expanded Abstracts, 56th SEG Annual International Meeting and Exposition, Houston, Texas, USA, November 2-6, 1986, Paper S9.6
746anisotropy, stress-induced anisotropy
747None
748None
749--
750api
7511.n. [General Terms]
752Abbreviation for American Petroleum Institute, a trade association founded in 1919 with offices in Washington, DC, USA. The API is sponsored by the oil and gas industry and is recognized worldwide. Among its long-term endeavors is the development of standardized testing procedures for drilling equipment, drilling fluids and cements, called API Recommended Practices ("RPs"). The API licenses the use of its monogram (logo), monitors supplier quality assurance methods and sets minimum standards for materials used in drilling and completion operations, called API Specifications ("Specs"). The API works in conjunction with the International Organization of Standards (ISO).Note: "API Publications, Programs and Services Catalogue" can be ordered from the API in electronic form at: http://www.api.org.Reference: Recommended Practice on the Rheology and Hydraulics of Oil-Well Drilling Fluids, 3rd ed. Washington, DC, USA: American Petroleum Institute, 1995.Recommended Practice Standard Procedure for Laboratory Testing of Drilling Fluids, 5th ed. Washington, DC, USA: American Petroleum Institute, 1995.
753apparent viscosity, ASTM, barite, beneficiation, calcium sulfate, filtrate volume, flash point, Garrett Gas Train, gel strength, gyp mud, high-pressure, high-temperature filtration test, high-pressure, high-temperature viscometer, IP, ISO, medium, milligrams per liter, montmorillonite, peptized clay, quality assurance, RP, titration, ultrafine, water, oil and solids test
754None
755None
756--
757autotrack
7581.vb. [Geophysics]
759To use computer software to pick a particular reflection or attribute in seismic data automatically. Autotracking can speed interpretation of three-dimensional seismic data, but must be checked for errors, especially in areas of faulting and stratigraphic changes.
760interpretation
761None
762None
763--
764acoustic transducer
7651.n. [Formation Evaluation]
766A device for transforming electrical energy into sound, or vice versa. In sonic logging applications, acoustic transducers are usually made of piezoelectric ceramic or magnetostrictive materials, and may be used as either receivers or transmitters in a frequency range between about 1 and 30 kHz. The transducers are excited as either monopoles, emitting or receiving sound in all directions, or dipoles, emitting or receiving in one plane. In ultrasonic logging applications, acoustic transducers are made of piezoelectric ceramic materials, and often are used in alternating transmitter/receiver (pulse-echo) mode, in a frequency range from a few hundred kilohertz to a few megahertz.
767monopole, sonic log, sonic measurement, ultrasonic measurement
768None
769None
770--
771aliphatic compound
7721.n. [Drilling Fluids]
773One of a group of organic compounds of carbon (C) and hydrogen (H) in which the carbon atoms have linear, branched chain (open), or both types of structures. Aliphatics, as they are informally called, can be divided into paraffinic (saturated) and olefinic (unsaturated) chain types. The simplest aliphatic, paraffinic hydrocarbon is methane, CH4. The simplest aliphatic, olefinic hydrocarbon is ethylene, C2H6. In drilling fluids, particularly oil-base muds, the amounts and types of hydrocarbon in the mud can be an important parameter in overall performance of the mud.
774aromatic hydrocarbon, naphthenic hydrocarbon, oil-base mud, soap
775acyclic compound
776None
777--
778api 6d
7791.n. [Production]
780API 6D specifies requirements and gives recommendations for the design, manufacturing, testing and documentation of ball, check, gate and plug valves for application in pipeline systems.
781None
782None
783None
784--
785autotracking
7861.n. [Geophysics]
787Use of computer software to pick a particularreflectionorattributeinseismicdata automatically. Autotracking can speed interpretation ofthree-dimensional seismic data, but must be checked for errors, especially in areas of faulting and stratigraphic changes.
788interpretation
789None
790None
791--
792acoustic transparency
7931.n. [Geophysics]
794The quality of a medium whose acoustic impedance is constant throughout, such that it contains no seismic reflections. An example of an acoustically transparent medium is water.
795reflection
796None
797None
798--
799alkaline flooding
8001.n. [Enhanced Oil Recovery, Enhanced Oil Recovery]
801An enhanced oil recovery technique in which an alkaline chemical such as sodium hydroxide, sodium orthosilicate or sodium carbonate is injected during polymer flooding or waterflooding operations. The alkaline chemical reacts with certain types of oils, forming surfactants inside the reservoir. Eventually, the surfactants reduce the interfacial tension between oil and water and trigger an increase in oil production.Alkaline flooding is not recommended for carbonate reservoirs because of the abundance of calcium: the mixture between the alkaline chemical and the calcium ions can produce hydroxide precipitation that may damage the formation.Alkaline flooding is also known as caustic flooding.
802alkaline-surfactant-polymer flooding, chemical flooding, micellar-polymer flooding
803None
804None
805--
806api fluid loss test
8071.n. [Drilling Fluids]
808A test to measure static filtration behavior of water mud at ambient (room) temperature and 100-psi differential pressure, usually performed according to specifications set by API, using a static filter press. The filter medium is filter paper with 7.1 sq. in. filtering area. A half-size cell is sometimes used, in which case the filtrate volume is doubled.
809filter cake, filter medium, filter press, filter-cake quality, filter-cake thickness, filtrate, filtrate tracer, filtrate volume, filtration, fluid-loss control, fluid-loss-control material, relative filtrate volume, spurt loss, static filtration
810API fluid-loss test
811Antonyms:high-pressure, high-temperature filtration test
812--
813average reservoir pressure
8141.n. [Well Testing]
815The pressure that would be obtained if all fluid motion ceases in a given volume of reservoir. It also is the pressure to which a well will ultimately rise if shut in for an infinite period.
816static pressure
817None
818None
819--
820average reservoir pressure
8212.n. [Production Testing]
822A volumetric average of the pressure exerted by the fluids inside the reservoir at a specific depletion stage. Average reservoir pressure can be measured only when the well is shut in.
823None
824None
825None
826--
827acoustic traveltime
8281.n. [Geophysics]
829The duration of the passage of a signal from the source through the Earth and back to the receiver. A time seismic section typically shows the two-way traveltime of the wave.
830acoustic log, average velocity, depth map, depth migration, isochron map, receiver, signal, sonic log, source, two-way traveltime, wave
831traveltime
832None
833--
834allochthon
8351.n. [Geology]
836A rock mass formed somewhere other than its present location, which was transported by fault movements, large-scale gravity sliding, or similar processes.
837allochthonous
838None
839Antonyms:autochthon
840--
841api fluid loss test
8421.n. [Drilling Fluids]
843A test to measure static filtration behavior of water mud at ambient (room) temperature and 100-psi differential pressure, usually performed according to specifications set by API, using a static filter press. The filter medium is filter paper with 7.1 sq. in. filtering area. A half-size cell is sometimes used, in which case the filtrate volume is doubled.
844filter cake, filter medium, filtrate, low-pressure, low-temperature filtration test, relative filtrate volume, spurt loss
845None
846None
847--
848average velocity
8491.n. [Geophysics]
850In geophysics, the depth divided by the traveltime of a wave to that depth. Average velocity is commonly calculated by assuming a vertical path, parallel layers and straight raypaths, conditions that are quite idealized compared to those actually found in the Earth.
851raypath, velocity
852None
853None
854--
855acoustic velocity
8561.n. [Geophysics]
857The rate at which a sound wave travels through a medium. Unlike the physicist's definition of velocity as a vector, its usage in geophysics is as a property of a medium: distance divided by traveltime. Velocity can be determined from laboratory measurements, acoustic logs, vertical seismic profiles or from velocity analysis of seismic data. It can vary vertically, laterally and azimuthally in anisotropic media such as rocks, and tends to increase with depth in the Earth because compaction reduces porosity. Velocity also varies as a function of how it is derived from the data. For example, the stacking velocity derived from normal moveout measurements of common depth point gathers differs from the average velocity measured vertically from a check-shot or vertical seismic profile (VSP). Velocity would be the same only in a constant-velocity (homogeneous) medium.
858acoustic, acoustic impedance, angular dispersion, anisotropy, apparent velocity, attribute, average velocity, base of weathering, birefringence, channel wave, check-shot survey, depth conversion, depth migration, discontinuity, dispersion, extensive dilatancy anisotropy, gas chimney, horizon, hydrocarbon indicator, interval velocity, processing, pull-up, push-down, ray tracing, reflection coefficient, reflection tomography, refraction, refractor, root-mean-square velocity, seismic trace, sonic log, stacking velocity, static correction, synthetic seismogram, time migration, tomography, velocity, velocity analysis, velocity anomaly, velocity correction, velocity layering, velocity survey, vertical seismic profile, wave, wave equation, wavelength, weathering correction
859None
860None
861--
862allochthonous
8631.adj. [Geology]
864Pertaining to materials, particularly rock masses, that formed somewhere other than their present location, and were transported by fault movements, large-scale gravity sliding, or similar processes. Autochthonous material, in contrast, formed in its present location. Landslides can result in large masses of allochthonous rock, which typically can be distinguished from autochthonous rocks on the basis of their difference in composition. Faults and folds can also separate allochthons from autochthons.
865fold
866None
867Antonyms:autochthonous
868--
869api gravity
8701.n. [Enhanced Oil Recovery, Heavy Oil]
871A specific gravity scale developed by the American Petroleum Institute (API) for measuring the relative density of various petroleum liquids, expressed in degrees. API gravity is gradated in degrees on a hydrometer instrument and was designed so that most values would fall between 10° and 70° API gravity. The arbitrary formula used to obtain this effect is: API gravity = (141.5/SG at 60°F) - 131.5, where SG is the specific gravity of the fluid.
872None
873None
874None
875--
876avo
8771.n. [Geophysics]
878Abbreviation for amplitude variation with offset. Variation in seismic reflection amplitude with change in distance between shotpoint and receiver that indicates differences in lithology and fluid content in rocks above and below the reflector. AVO analysis is a technique by which geophysicists attempt to determine thickness, porosity, density, velocity, lithology and fluid content of rocks. Successful AVO analysis requires special processing of seismic data and seismic modeling to determine rock properties with a known fluid content. With that knowledge, it is possible to model other types of fluid content. A gas-filled sandstone might show increasing amplitude with offset, whereas a coal might show decreasing amplitude with offset. A limitation of AVO analysis using only P-energy is its failure to yield a unique solution, so AVO results are prone to misinterpretation. One common misinterpretation is the failure to distinguish a gas-filled reservoir from a reservoir having only partial gas saturation ("fizz water"). However, AVO analysis using source-generated or mode-converted shear wave energy allows differentiation of degrees of gas saturation. AVO analysis is more successful in young, poorly consolidated rocks, such as those in the Gulf of Mexico, than in older, well-cemented sediments.
879None
880None
881amplitude variation with offset
882--
883acquisition
8841.n. [Geophysics]
885The generation and recording of seismic data. Acquisition involves many different receiver configurations, including laying geophones or seismometers on the surface of the Earth or seafloor, towing hydrophones behind a marine seismic vessel, suspending hydrophones vertically in the sea or placing geophones in a wellbore (as in a vertical seismic profile) to record the seismic signal. A source, such as a vibrator unit, dynamite shot, or an air gun, generates acoustic or elastic vibrations that travel into the Earth, pass through strata with different seismic responses and filtering effects, and return to the surface to be recorded as seismic data. Optimal acquisition varies according to local conditions and involves employing the appropriate source (both type and intensity), optimal configuration of receivers, and orientation of receiver lines with respect to geological features. This ensures that the highest signal-to-noise ratio can be recorded, resolution is appropriate, and extraneous effects such as air waves, ground roll, multiples and diffractions can be minimized or distinguished, and removed through processing.
886acoustic positioning, air wave, aperture, bubble effect, circle shooting, common midpoint method, crossline, deep tow, depth controller, eel, explosive seismic data, four-dimensional seismic data, gather, geophone, header, hydrophone, impulsive seismic data, in-line, offset vertical seismic profile, seismic modeling, seismic-while-drilling vertical seismic profile, seismometer, shot depth, shotpoint, skid, spread, streamer feathering, suppression, tail buoy, three-dimensional seismic data, time-lapse seismic data, transition zone, two-dimensional seismic data, undershooting, vibratory seismic data, water gun
887None
888None
889--
890allogenic
8911.adj. [Geology]
892Pertaining to minerals or rock fragments that formed in one location but were transported to another location and deposited. Clastic sediments in a rock such as sandstone are allogenic, or formed elsewhere.
893clastic sediment
894None
895Antonyms:authigenic
896--
897api unit
8981.n. [Formation Evaluation]
899The unit of radioactivity used for natural gamma ray logs. This unit is based on an artificially radioactive concrete block at the University of Houston, Texas, USA, that is defined to have a radioactivity of 200 American Petroleum Institute (API) units. This was chosen because it was considered to be twice the radioactivity of a typical shale. The formation is the primary standard for calibrating gamma ray logs. However, even when properly calibrated, different gamma ray tools will not necessarily have identical readings downhole because their detectors can have different spectral sensitivities. They will read the same only if the downhole formation contains the same proportions of thorium, potassium and uranium as the Houston standard. For example, logging while drilling (LWD) tools have thicker housings than wireline tools, causing a different spectral response to the three sources of radioactivity, and therefore a different total gamma ray reading in some formations.The nuclear well log calibration facility at the University of Houston, known as the API pits, was opened in 1959 for the calibration of natural gamma ray and neutron logs. A facility for calibrating natural gamma ray spectroscopy logs was added later.
900neutron log
901None
902None
903--
904axial loading
9051.n. [Well Completions]
906The force acting along the axis of an object. In wellbore tubulars, axial loading is typically expressed as tension or compression and may result from applied conditions such as set-down-weight, or be induced by operating conditions or variations such as changes in temperature that cause expansion or contraction of components.
907None
908None
909None
910--
911acquisition log
9121.n. [Formation Evaluation]
913The log that is actually recorded while taking the measurements. It is distinct from a playback, which is produced later on from digital data.
914base log, composite log, correlation log, detail log
915None
916None
917--
918alluvial
9191.adj. [Geology]
920Pertaining to the subaerial (as opposed to submarine) environment, action and products of a stream or river on its floodplain, usually consisting of detrital clastic sediments, and distinct from subaqueous deposition such as in lakes or oceans and lower energy fluvial deposition. Sediments deposited in an alluvial environment can be subject to high depositional energy, such as fast-moving flood waters, and may be poorly sorted or chaotic.
921alluvium, clastic sediment, depositional system, sediment
922None
923None
924--
925apparent anisotropy
9261.n. [Geophysics]
927In seismic data, the ratio of the velocity determined from normal moveout (i.e., primarily a horizontal measurement) to velocity measured vertically in a vertical seismic profile or similar survey. Apparent anisotropy is of particular importance when migrating long-offset seismic data and analyzing AVO data accurately. The normal moveout velocity involves the horizontal component of the velocity field, which affects sources and receivers that are offset, but the horizontal velocity field is not involved in velocity calculations from vertically measured time-depth pairs.
928amplitude variation with offset
929None
930None
931--
932axial surface
9331.n. [Geology]
934In folded rocks, the imaginary surface bisecting the limbs of the fold. The axial surface is called the axial plane when the fold is symmetrical and the lines defined by the points of maximum curvature of each folded layer, or hinge lines, are coplanar.
935None
936None
937None
938--
939acrylamide acrylate polymer
9401.n. [Drilling Fluids]
941A linear copolymer of acrylate (anionic) and acrylamide (nonionic) monomers, also called partially-hydrolyzed polyacrylamide (PHPA). The ratio of acrylic acid to acrylamide groups on the polymer chain can be varied in manufacturing, as can molecular weight. Another variable is the base used to neutralize the acrylic acid groups, usually NaOH or KOH, or sometimes NH4OH. A concentration of approximately 10 to 30% acrylate groups provides optimal anionic characteristics for most drilling applications. High-molecular weight PHPA is used as a shale-stabilizing polymer in PHPA mud systems. It is also used as clay extender, either dry-mixed into clay or added at the rig to a low-bentonite mud. PHPA can also be used to flocculate colloidal solids during clear-water drilling and for wastewater cleanup. Low molecular-weight PHPA is a clay deflocculant.
942None
943None
944acrylamide-acrylate polymer
945--
946alluvium
9471.n. [Geology]
948Material deposited in an alluvial environment, typically detrital sediments that are poorly sorted.
949sediment
950None
951None
952--
953apparent matrix
9541.n. [Formation Evaluation]
955A calculation of the properties of the solid fraction of a rock from the combination of two logs. For example, by combining the density and neutron porosity measurements, it is possible to compute an apparent matrix density; by combining neutron porosity and sonic measurement, it is possible to compute an apparent matrix traveltime. The computations assume a particular fluid, usually fresh water, and particular response equations. The results are often displayed as quicklook logs for lithology identification. The word matrix is used here in the formation evaluation sense of the term rather than the geological one.
956crossplot porosity
957None
958None
959--
960azimuth
9611.n. [Geology]
962The angle between the vertical projection of a line of interest onto a horizontal surface and true north or magnetic north measured in a horizontal plane, typically measured clockwise from north.
963attitude, dip, strike, trend
964None
965None
966--
967azimuth
9682.n. [Drilling]
969The compass direction of a directional survey or of the wellbore as planned or measured by a directional survey. The azimuth is usually specified in degrees with respect to the geographic or magnetic north pole.
970directional drilling, inclination, survey
971None
972None
973--
974azimuth
9753.n. [Reservoir Characterization]
976The angle that characterizes a direction or vector relative to a reference direction (usually True North) on a horizontal plane. The azimuth is usually quoted in degrees from 0 to 359.
977None
978None
979None
980--
981azimuth
9824.n. [Drilling, Shale Gas]
983The direction in which a deviated or horizontal well is drilled relative to magnetic north. Most horizontal wells in shale reservoirs are drilled in the direction of the minimum horizontal stress. This allows for the creation of multiple hydraulic fractures that are normal to the wellbore.
984None
985None
986None
987--
988acrylamide polymer
9891.n. [Drilling Fluids]
990A linear, nonionic polymer made of acrylamide monomers, CH2=CHCONH2 . High molecular-weight polyacrylamides are used as selective flocculants in clear-water drilling, low-solids muds and wastewater cleanup. Polymers made of smaller molecules are used as clay deflocculants in water muds, which can contain hardness ions. Polyacrylamides are not nearly as sensitive to salinity and hardness as the anionic polyacrylates (SPA). Also, being nonionic, they are not as powerful for flocculation or deflocculation applications. Acrylamide polymers are, however, susceptible to hydrolysis and release ammonia under hot, alkaline conditions.
991acrylamide-acrylate polymer, acrylamido-methyl-propane sulfonate polymer, acrylate polymer, clay extender, clear-water drilling, colloidal solids, deflocculant, flocculant, low-solids mud, PHPA mud, vinyl polymer, water clarification
992None
993None
994--
995all welded construction
9961.adj. [Production]
997As it pertains to a valve construction, a valve body that is completely welded and cannot be disassembled and repaired in the field.
998None
999None
1000None
1001--
1002apparent velocity
10031.n. [Geophysics]
1004In geophysics, the velocity of a wavefront in a certain direction, typically measured along a line of receivers and symbolized by va. Apparent velocity and velocity are related by the cosine of the angle at which the wavefront approaches the receivers:va = v cos θ,whereva = apparent velocityv = velocity of wavefrontθ = angle at which a wavefront approaches the geophone array.
1005receiver, velocity, wave
1006None
1007None
1008--
1009azimuthal
10101.adj. [Formation Evaluation]
1011Pertaining to being focused in one direction. An azimuthal, or azimuthally focused, measurement has one or more directions perpendicular to the surface of a logging tool from which it receives most of its signal. Examples are the density, laterolog and microresistivity logs. A nonazimuthal, or azimuthally symmetric measurement is one which measures equally in all directions around the tool. Examples are the induction, propagation resistivity log and gamma ray.
1012azimuthal density, azimuthal laterolog, logging tool
1013None
1014None
1015--
1016azimuthal
10172.adj. [Geology]
1018Pertaining to the angle between the vertical projection of a line of interest onto a horizontal surface and true north or magnetic north measured in a horizontal plane, typically measured clockwise from north.
1019attitude, dip, strike, trend
1020None
1021None
1022--
1023acrylamide acrylate polymer
10241.n. [Drilling Fluids]
1025A linear copolymer of acrylate (anionic) and acrylamide (nonionic) monomers, also called partially-hydrolyzed polyacrylamide (PHPA). The ratio of acrylic acid to acrylamide groups on the polymer chain can be varied in manufacturing, as can molecular weight. Another variable is the base used to neutralize the acrylic acid groups, usually NaOH or KOH, or sometimes NH4OH. A concentration of approximately 10 to 30% acrylate groups provides optimal anionic characteristics for most drilling applications. High-molecular weight PHPA is used as a shale-stabilizing polymer in PHPA mud systems. It is also used as clay extender, either dry-mixed into clay or added at the rig to a low-bentonite mud. PHPA can also be used to flocculate colloidal solids during clear-water drilling and for wastewater cleanup. Low molecular-weight PHPA is a clay deflocculant.
1026acrylamide polymer, acrylate polymer, beneficiation, clay-water interaction, copolymer, encapsulation, flocculant, hardness ion, hydrolysis, low-solids mud, potassium mud, seawater mud, vinyl polymer
1027None
1028None
1029--
1030alpha processing
10311.n. [Formation Evaluation]
1032A technique for combining a measurement that has a high accuracy but low precision with another measurement of the same quantity that has a high precision but low accuracy in order to produce a result that is better than either alone. Alpha processing is used to improve the vertical resolution of neutron porosity and other dual-detector nuclear logs. The detector near the source has better precision than the far detector in the sense that it responds more precisely to vertical changes. However, the near detector is less accurate because it is more affected by the borehole environment. Alpha processing mathematically superimposes the rapid changes of the near detector on the slowly changing but accurate far detector to produce an accurate log with high vertical resolution.The technique is also used to improve results from the carbon-oxygen log and other pulsed neutron spectroscopy measurements. Two methods are used to determine the carbon/oxygen ratio. The windows method counts the number of gamma rays within energy windows placed at the main peaks for carbon and oxygen. This method has good statistical precision but poor accuracy, as gamma rays from other elements contaminate these windows. The other method, spectral stripping, compares the total spectrum against standards for many elements, inverting the spectrum to obtain the yield for each element. This method is more accurate but has less statistical precision. Averaging over a number of measurements, alpha processing adjusts the windows result with the more accurate spectral stripping in order to obtain a precise and accurate result.
1033compensated neutron log, pulsed neutron spectroscopy measurement, response matched, vertical response
1034None
1035None
1036--
1037apparent wavelength
10381.n. [Geophysics]
1039The wavelength measured by receivers when a wave approaches at an angle. The relationship between true and apparent wavelength can be shown mathematically as follows:λ = λa sin θ,whereλ = wavelengthλa = apparent wavelengthθ = angle at which a wavefront approaches the geophone array.
1040receiver, wavelength
1041None
1042None
1043--
1044azimuthal density
10451.n. [Formation Evaluation]
1046A type of logging while drilling density log in which the density is measured at different azimuths around the drill collar. The density measurement is focused, so that when the collar rotates, the measurement sees different azimuths around the borehole. An average density can be calculated by summing all the azimuthal data. Alternatively, the data can be summed over different segments, for example in four quadrants, to give an azimuthal density in four directions. When the hole is overgauge, certain quadrants will be firmly pressed against the borehole wall, while others may have a significant standoff and too high a delta rho. The good quadrants can then be chosen for formation evaluation.
1047azimuthal resolution, compensated-density log, density measurement, quadrant density, spine and ribs plot
1048None
1049None
1050--
1051acrylate polymer
10521.n. [Drilling Fluids]
1053Linear, anionic polymer made from the monomer acrylic acid, CH2=CHCOO- H+. The acrylic acid groups are evenly spaced along the chain. Acrylic acid polymer neutralized with NaOH is sodium polyacrylate (SPA). Polyacrylates are best utilized in soft water with low salinity to achieve the best dispersion and full chain elongation. Even low concentrations of hardness ions, for example, Ca+2, precipitate polyacrylates. Low molecular-weight polyacrylates are used as clay deflocculants. High molecular weight polymers are used for fluid-loss control and as a clay extender. As an extender, SPA is added to bentonite at the grinding plant. It is also used at the rig in low-solids mud. Divalent cations can negate its benefits as a clay extender. SPA is highly efficient when used to flocculate colloids in native-solids muds, clear-water muds and wastewater cleanup. The polymer chain links together colloidal solids that can be removed by gravity settling in shallow pits or by applying hydrocyclone, centrifuge or filtration techniques.
1054acrylamide polymer, acrylamide-acrylate polymer, anion, calcium contamination, clear-water drilling, deflocculant, deflocculated mud, flocculant, hardness ion, low-solids, nondispersed mud, native-solids mud, PHPA mud, sodium bicarbonate, sodium carbonate, sodium polyacrylate, soft water, water clarification
1055polyacrylate
1056None
1057--
1058altered zone
10591.n. [Formation Evaluation]
1060A near-wellbore formation zone, a few inches thick, whose acoustic velocity has been affected by impregnation with drilling fluids, stress relief, or both. The acoustic velocity of the rock in the immediate vicinity of the borehole wall can be much slower than that in the virgin formation. To measure the formation velocity, it may be necessary to use a sonic logging tool that has a greater spacing between transmitter and receiver array (about 10 to 15 ft [3 to 4.5 m]) than the standard sonic tool (about 3 to 5 ft [0.9 to 1.5 m]). The altered zone may also give rise to different acoustic modes, for example the hybrid mode or a second Stoneley wave.
1061long-spacing sonic log
1062None
1063None
1064--
1065archie rock
10661.n. [Formation Evaluation]
1067A rock whose petrophysical properties are well described by the Archie equation with constant values for the porosity exponent and the saturation exponent. Such rocks typically have very little clay, a regular pore structure and high-salinity water. The term often is used to describe a rock that is petrophysically simple.
1068formation factor, formation water, resistivity index, water saturation
1069None
1070None
1071--
1072azimuthal laterolog
10731.n. [Formation Evaluation]
1074A type of electrode device that is able to measure resistivity in different directions around the sonde. In most laterologs, the electrodes are cylinders that average the resistivity azimuthally around the sonde. In azimuthal laterologs, the electrode is segmented radially in several portions, each of which responds to the resistivity in the direction it is facing.
1075button resistivity, electrode resistivity
1076None
1077None
1078--
1079activation log
10801.n. [Formation Evaluation]
1081A 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 carbon-oxygen log, elemental capture spectroscopy log, pulsed neutron spectroscopy log, aluminum activation log and oxygen activation log are all examples of activation logs. However, the term is most commonly used to refer to the aluminum and oxygen activation logs, the latter also being known as a water-flow log.
1082geochemical log, induced gamma ray spectroscopy, oxygen activation
1083None
1084None
1085--
1086ambient temperature
10871.n. [Well Completions]
1088The temperature at a point or area expressed as an average of the surrounding areas or materials. Ambient surface temperature is generally given to be 70 to 80oF [21 to 27oC]-an average of daily and seasonal variations.
1089None
1090None
1091None
1092--
1093arithmetic mean
10941.n. [Reservoir Characterization]
1095A mathematical method of finding a central value for a group of data. It is most often referred to as the average but also as the mean. The arithmetic mean is the sum of all the observed values divided by the number of observations.
1096None
1097mean
1098None
1099--
1100azimuthal resolution
11011.n. [Formation Evaluation]
1102An angle that characterizes the ability of an azimuthal logging measurement to resolve changes in different directions around the tool; alternatively, the smallest angle for which a significant change can be detected.
1103None
1104None
1105None
1106--
1107back flow
11081.n. [Well Testing]
1109Fluid flow in the borehole from one zone into another in response to pressure differences between the zones. Any time the wellbore pressure rises above the average pressure in any zone, backflow will occur. Analysis of buildup tests involving backflow is either impossible or extremely difficult and usually requires expert input to determine useful information from such tests.
1110buildup test, crossflow
1111backflow
1112None
1113--
1114basement
11151.n. [Geology]
1116The rock layer below which economic hydrocarbon reservoirs are not expected to be found, sometimes called economic basement. Basement is usually older, deformed igneous or metamorphic rocks, which seldom develops the porosity and permeability necessary to serve as a hydrocarbon reservoir, and below which sedimentary rocks are not common. Basement rocks typically have different density, acoustic velocity, and magnetic properties from overlying rocks.
1117acoustic basement, craton, geologic time scale, igneous, metamorphic, nonconformity, platform, reservoir, unconformity
1118None
1119None
1120--
1121blaine fineness
11221.n. [Drilling Fluids]
1123The particle size or fineness of a cement in cm2/g or m2/kg, usually determined from air permeability tests using a device known as a Blaine permeameter. Fineness affects the hydration rate (setting) and the requirements for the amounts of water, retarder and dispersant.
1124None
1125None
1126None
1127--
1128bottomhole static temperature
11291.n. [Drilling, Well Completions]
1130The temperature of the undisturbed formation at the final depth in a well. The formation cools during drilling and most of the cooling dissipates after about 24 hours of static conditions, although it is theoretically impossible for the temperature to return to undisturbed conditions. This temperature is measured under static conditions after sufficient time has elapsed to negate any effects from circulating fluids. Tables, charts and computer routines are used to predict BHST as functions of depth, geographic area and various time functions. The BHST is generally higher than the bottomhole circulating temperature, and can be an important factor when using temperature-sensitive tools or treatments.
1131total depth
1132None
1133BHST
1134--
1135bottomhole static temperature
11362.n. [Drilling Fluids]
1137The undisturbed temperature at the bottom of a well, abbreviated as BHST. After circulation and after the well is shut in, the temperature approaches the BHST after about 24 to 36 hours, depending on the well conditions. The BHST is the temperature used in most tests in which the cement slurry is required to set or is set.
1138None
1139None
1140BHST
1141--
1142back in
11431.n. [Oil and Gas Business]
1144The right to receive a reversionary interest at some future time, upon fulfillment of contractually specified conditions. This clause allows alease-owner, lessee or a nonparticipating partner to reserve the option to participate in a well after it has produced enough to pay the operators expenses of drilling and completing that well. This clause is typically used infarmoutagreements to convert theoverriding royalty interestof a lease-owner, lessee or nonparticipating partner into aworking interestuponpayoutof the well. When the election to convert the overriding royalty to working interest takes place, it is known as a back-in after payout(BIAPO).
1145None
1146None
1147back-in
1148--
1149basket
11501.n. [Well Workover and Intervention]
1151A downhole device or tool component designed to catch debris or objects, such as balls, darts or plugs dropped to actuate downhole equipment or tools.
1152None
1153None
1154None
1155--
1156bland coring fluid
11571.n. [Drilling Fluids]
1158A coring fluid formulated with components that are not likely to alter the wettability in the pores of the rock sample and that has low dynamic filtration characteristics. These qualities help retain the core's native properties and can retain some (or all) of the reservoir's fluids [water, oil and gas (gas only if kept under pressure)]. Bland water-base fluid is formulated to make the filtrate resemble the connate water in the reservoir. Keeping ionic composition and especially the pH matched to the reservoir water is most important. Thus, strong alkaline agents and clay deflocculants are avoided when designing bland coring fluids. Bland oil-base fluids should contain no water phase, and the base oil should resemble the reservoir oil. (Reservoir crude is used in some cases.) Amine, amide, phosphonated and sulfonated emulsifiers and the powerful oil-wetting agents are also avoided. Fatty acid soaps are chosen to emulsify the trace of water that is likely to be encountered. Additives that minimize dynamic filtration rate must be chosen. Setting mud density and bit hydraulics to give equivalent circulating density close to the reservoir pressure helps avoid filtrate invasion into the core. Designing core bits to core as fast as possible also limits filtrate invasion ahead of the bit.
1159alkaline, amides, amines, core, coring fluid, deflocculant, drill-in fluid, emulsifier, filtrate tracer, mud weight, pH, reservoir pressure
1160None
1161None
1162--
1163bottomhole temperature
11641.n. [Formation Evaluation]
1165The temperature in the borehole at total depth at the time it is measured. In log interpretation, the bottom hole temperature (BHT) is taken as the maximum recorded temperature during a logging run, or preferably the last of series of runs during the same operation. BHT is the temperature used for the interpretation of logs at total depth. Farther up the hole, the correct temperature is calculated by assuming a certain temperature gradient. The BHT lies between the bottomhole circulating temperature (BHCT) and the bottomhole static temperature (BHST).
1166None
1167None
1168BHT
1169--
1170bottomhole temperature
11712.n. [Well Completions]
1172The downhole temperature measured or calculated at a point of interest. The BHT, without reference to circulating or static conditions, is typically associated with producing conditions.
1173None
1174None
1175BHT
1176--
1177back off
11781.vb. [Drilling]
1179To unscrew drillstring components downhole. The drillstring, including drillpipe and the bottomhole assembly, are coupled by various threadforms known as connections, or tool joints. Often when a drillstring becomes stuck it is necessary to "back off" the string as deep as possible to recover as much of the string as possible. To facilitate the fishing or recovery operation, the backoff is usually accomplished by applying reverse torque and detonating an explosive charge inside a selected threaded connection. The force of the explosion enlarges the female (outer) thread enough that the threaded connection unscrews instantly. A torqueless backoff may be performed as well. In that case, tension is applied, and the threads slide by each other without turning when the explosive detonates. Backing off can also occur unintentionally.
1180box, connection, fish, pin, threadform, tool joint
1181break out
1182backoff
1183--
1184basket flowmeter
11851.n. [Production Logging]
1186A device for measuring in situ the velocity of fluid flow in a production or injection well in which the flow is diverted through the spinner by a set of metal vanes, or petals. The vanes are closed while running in the hole, and then opened with the tool stationary at the measurement depth. The petals do not seal completely against each other or against the side of the hole, so that not all the fluid is diverted. A type of diverter flowmeter, the petal basket design has generally been replaced since the late 1980s by the inflatable diverter and other designs.
1187in situ, packer flowmeter, spinner flowmeter
1188petal basket flowmeter
1189None
1190--
1191blast joint
11921.n. [Perforating, Well Completions]
1193A section of heavy walled tubing that is placed across any perforated interval through which the production tubing must pass, such as may be required in multiple zone completions. In addition to being heavier than normal completion components, the wall of a blast joint is often treated to resist the jetting action that may result in the proximity of the perforations.
1194production tubing
1195None
1196None
1197--
1198bouguer correction
11991.n. [Geophysics]
1200The adjustment to a measurement of gravitational acceleration to account for elevation and the density of rock between the measurement station and a reference level. It can be expressed mathematically as the product of the density of the rock, the height relative to sea level or another reference, and a constant, in units of mGal:δgB = 2 π G ρ h = 0.4193 ρ hwhereδgB = Bouguer correctionρ = rock density in kg/m3h = height difference between two locations in mG = gravitational constant = 6.67384 × 10−11 m3 kg−1 s−2Strictly interpreted, the Bouguer correction is added to the known value of gravity at the reference station to predict the value of gravity at the measurement level. The difference between the actual value and the predicted value is the gravity anomaly, which results from differences in density between the actual Earth and reference model anywhere below the measurement station.
1201Bouguer anomaly, elevation correction, gravity anomaly
1202None
1203None
1204--
1205back pressure
12061.n. [Well Completions]
1207The pressure within a system caused by fluid friction or an induced resistance to flow through the system. Most process facilities require a minimum system pressure to operate efficiently. The necessary back-pressure is often created and controlled by a valve that is set to operate under the desired range of conditions.
1208None
1209None
1210back-pressure
1211--
1212back pressure
12132.n. [Production]
1214Pressure opposing the desired flow of a fluid in a pipe. Usually results from obstructions and tight bends in confinement vessels.
1215None
1216None
1217None
1218--
1219batch mixer
12201.n. [Well Workover and Intervention]
1221A vessel and mixing system used to prepare treatment fluids. A batch mixer is generally equipped with a means of adding dry and liquid chemicals, an agitation or circulation system and a manifold system to deliver the prepared fluid to storage tanks or treating pumps.
1222treatment fluid
1223None
1224None
1225--
1226blast sleeve
12271.n. [Well Completions, Well Workover and Intervention]
1228A sleeve installed in flow control equipment to protect sensitive equipment from abrasive fluid flow. A blast sleeve is commonly inserted in flow crosses where wireline, coiled tubing, or fiber-optic cables are being passed through.
1229None
1230None
1231None
1232--
1233bouma sequence
12341.n. [Geology]
1235A characteristic sequence of sedimentary structures occurring in sedimentary rocks deposited in areas of deep water sedimentation by turbidity currents, which form deposits called turbidites. In theory, a complete Bouma sequence comprises sediments that fine upwards, consisting of a lowermost layer of coarse, chaotic clastic sediments deposited under conditions of high depositional energy overlain by successively finer grained and better stratified sediments like sands and muds deposited under calmer conditions that are labeled as Units A though E. In practice, however, the chaotic, high-energy nature of turbidite deposition can alter or remove underlying sediments so that incomplete sequences of sediments typically remain preserved.
1236clastic sediment, depositional energy, sediment, turbidity current
1237None
1238None
1239--
1240back pressure valve
12411.n. [Well Completions]
1242A type of check valve, typically installed in the tubing hanger, to isolate the production tubing. The back-pressure valve is designed to hold pressure from below yet enable fluids to be pumped from above, as may be required for well-control purposes.
1243None
1244None
1245back-pressure valve
1246--
1247battery
12481.n. [Production Facilities]
1249The installation of similar or identical units of equipment in a group, such as a separator battery, header battery, filter battery or tank battery.
1250battery site
1251None
1252None
1253--
1254blasting cap
12551.n. [Well Completions, Geophysics]
1256A small, electrically activated explosive charge that explodes a larger charge. Detonators, also called caps,seismiccaps or blasting caps, are used for seismicacquisitionwith an explosivesourceto achieve consistent timing of detonation.
1257cap, detonator
1258None
1259None
1260--
1261blasting cap
12622.n. [Well Completions, Geophysics]
1263A device containing primary high-explosive material that is used to initiate an explosive sequence. The two common types of detonators are electrical detonators (also known as blasting caps) and percussion detonators. Electrical detonators have a fuse material that burns when high voltage is applied to initiate the primaryhigh explosive. Percussion detonators contain abrasive grit and primary high explosive in a sealed container that is activated by a firing pin. The impact force of the firing pin is sufficient to initiate the ballistic sequence that is then transmitted to the detonating cord. Several safety systems are used in conjunction with detonators to avoid accidental firing duringrig-up or rig-down. Safety systems also are used to disarm the gun or ballistic assembly if downhole conditions are unsafe for firing.
1264None
1265None
1266None
1267--
1268bound fluid
12691.n. [Formation Evaluation]
1270Fluid in the pore space that does not flow under normal reservoir conditions. This fluid may include water, oil or gas, but most often refers just to bound water. Bound fluid does not flow on primary or secondary production, injection or invasion unless the rock wettability is altered.When used in connection with a nuclear magnetic resonance measurement, the term refers to the signal that occurs below a certain cutoff, typically 33 ms in sandstones and 100 ms in carbonates. The source of this signal is bound water, but may also include oil with a viscosity above about 60 cp in sandstones or 30 cp in carbonates. Note that, contrary to the sense of "bound," this oil may or may not be moveable under normal reservoir conditions.
1271nuclear magnetic resonance, primary production, secondary production
1272None
1273None
1274--
1275back stripping
12761.n. [Geophysics]
1277A modeling technique to assess the geologic history of rock layers through the use of geologic cross sections or seismic sections. Removal of the youngest layers of rock at the top of the section allows restoration of the underlying layers to their initial, undisturbed configurations. Successively older layers can be removed sequentially to further assess the effects of compaction, development of geologic structures and other processes on an area.
1278None
1279None
1280back-stripping
1281--
1282bbl or bbl
12831.n. [Drilling Fluids]
1284An abbreviation for oilfield barrel, a volume of 42 US gallons [0.16 m3].
1285None
1286None
1287None
1288--
1289blended crude
12901.n. [Heavy Oil]
1291A mixture of crude oils, blended in the pipeline to create a crude with specific physical properties. Because heavy and extra-heavy crudes or bitumens cannot flow from the field to the refinery in their original state and at normal surface temperatures, they are blended with lighter crude oils primarily to reduce viscosity, thereby enabling transportation to a refinery. A secondary objective may be to provide a blended crude oil that has significantly higher value than the raw heavy crude. The blend is usually constructed so that the value of the overall blended volume is greater than the summed value of the initial volumes of individual heavy and light crudes.
1292bitumen, heavy oil, light crude oil, raw crude oil
1293None
1294None
1295--
1296bound water
12971.n. [Formation Evaluation]
1298Water in the pore space that does not flow under normal reservoir conditions. Bound water does not flow on primary or secondary production, injection or invasion unless the rock wettability is altered.When used in connection with a nuclear magnetic resonance measurement, the term refers to all the water that is not free to move. This includes capillary-bound water and clay-bound water. However, water in mineral hydrates is not included as it relaxes too fast to be measured by nuclear magnetic resonance (NMR). In practice, bound water is defined as the water signal below a certain cutoff, typically 33 ms in sandstones and 100 ms in carbonates.When used in connection with the dual water model, the term refers to the clay-bound water only. In the Hill-Shirley-Klein model, the term is known as the hydration water.
1299bound fluid, nuclear magnetic resonance, primary production, secondary production
1300None
1301None
1302--
1303backflow
13041.n. [Well Testing]
1305Fluid flow in the borehole from one zone into another in response to pressure differences between the zones. Any time the wellbore pressure rises above the average pressure in any zone, backflow will occur. Analysis of buildup tests involving backflow is either impossible or extremely difficult and usually requires expert input to determine useful information from such tests.
1306buildup test, crossflow
1307None
1308None
1309--
1310bead tracer
13111.n. [Production Logging]
1312A small, radioactive plastic sphere that is insoluble and used to make a tracer-loss measurement. The bead is designed to have the same density as the injection fluid so that it travels with the fluid when it is placed in the flow stream of an injection well. However, the bead does not enter the formation. It remains on the rock face in openhole, or within the perforation channel in cased hole, where it can be detected by a gamma ray log. A high radioactivity opposite a perforation indicates a large number of beads and hence a high injectivity. The technique was used mainly in the 1960s and 1970s.
1313plate out, production log, radioactive-tracer log, tracer measurement
1314None
1315None
1316--
1317blender
13181.n. [Well Workover and Intervention]
1319The equipment used to prepare the slurries and gels commonly used in stimulation treatments. The blender should be capable of providing a supply of adequately mixed ingredients at the desired treatment rate. Modern blenders are computer controlled, enabling the flow of chemicals and ingredients to be efficiently metered and requiring a relatively small residence volume to achieve good control over the blend quality and delivery rate.
1320gel, slurry
1321None
1322None
1323--
1324bound fluid log
13251.n. [Formation Evaluation]
1326A type of nuclear magnetic resonance (NMR) log that is designed to record properly only the bound fluid. Bound fluid is characterized by a fast relaxation time, typically less than 33 ms in sandstones and 100 ms in carbonate rocks. Therefore, the wait time for a bound fluid log can be much shorter than for standard NMR logs, with the result that logging speeds are much faster.
1327nuclear magnetic resonance measurement
1328None
1329None
1330--
1331background gas
13321.n. [Drilling]
1333An average or baseline measure of gas entrained in circulating mud. This baseline trend pertains to gas that is liberated downhole while drilling through a uniform lithologic interval at a constant rate of penetration. The gas is typically obtained from a suction line above the gas trap located immediately upstream of the shale shaker screens, where the gas evolves out of the mud.Oil-base mud systems tend to produce higher background gas values than do water-base muds. Deviations from the background gas trend likely indicate changes in porosity or permeability, or changes in drilling conditions; any of which merits further investigation. A drift or gradual shift of the background gas trend toward higher values may indicate a slow gas influx into the mud column, which can eventually lead to a kick or blowout. When annotated on mud logs, background gas is usually abbreviated as BGG.
1334contamination gas, entrained gas, gas show
1335None
1336BGG
1337--
1338bean choke
13391.n. [Well Completions]
1340A fixed choke used to control the flow of fluids, usually mounted on or close to the Christmas tree. A bean choke contains a replaceable insert, or bean, made from hardened steel or similar durable material. The insert is manufactured with a precise diameter hole that forms the choke through which all fluids must pass. Choke inserts are available in a complete range of sizes, generally identified by choke diameter stated in 64ths of an inch; for example, a "32 bean" is equivalent to a 1/2-in. choke diameter.
1341bean
1342None
1343None
1344--
1345blind box
13461.n. [Well Workover and Intervention]
1347A simple slickline tool used to dislodge or push tools or equipment down the wellbore. The blind box is generally of heavy construction and is hardened to reduce damage when jarring is required.
1348borehole
1349None
1350None
1351--
1352box
13531.n. [Drilling]
1354A female threadform (internally threaded) for tubular goods and drillstring components.
1355back off, break out, casing, casing string, mousehole, pin
1356None
1357None
1358--
1359box
13602.adj. [Drilling]
1361Relating to the female threadform, as in "box end of the pipe."
1362pin
1363None
1364None
1365--
1366back in
13671.n. [Oil and Gas Business]
1368The right to receive a reversionary interest at some future time, upon fulfillment of contractually specified conditions. This clause allows a lease-owner, lessee or a nonparticipating partner to reserve the option to participate in a well after it has produced enough to pay the operators expenses of drilling and completing that well. This clause is typically used in farmout agreements to convert the overriding royalty interest of a lease-owner, lessee or nonparticipating partner into a working interest upon payout of the well. When the election to convert the overriding royalty to working interest takes place, it is known as a back-in after payout (BIAPO).
1369None
1370None
1371None
1372--
1373bed
13741.n. [Geology]
1375A layer of sediment or sedimentary rock, or stratum. A bed is the smallest stratigraphic unit, generally a centimeter or more in thickness. To be labeled a bed, the stratum must be distinguishable from adjacent beds.
1376bed thickness, competent, dipping bed, lamination, progradation, retrogradation, sediment, strike, superposition, true stratigraphic thickness, true vertical thickness
1377None
1378None
1379--
1380blind shear ram
13811.n. [Well Workover and Intervention, Drilling]
1382Ablowoutpreventer (BOP) closing element fitted with hardened tool steel blades designed to cut the drillpipeor tubing when the BOP is closed, and then fully close to provide isolation or sealing of the wellbore. Ashearram is normally used as a last resort to regainpressurecontrol of a well that is flowing. Once the pipe is cut (or sheared) by the shear rams, it is usually left hanging in the BOP stack, and kill operations become more difficult. Thejointof drillpipe or tubing is destroyed in the process, but the rest of the stringis unharmed by the operation of shear rams.
1383blind ram, blow out preventer, BOP stack, kill, shear-seal BOP
1384shear ram
1385None
1386--
1387boyles law double cell
13881.n. [Formation Evaluation]
1389A technique for measuring the grain volume of a core sample by observing the change in pressure of helium introduced into a chamber containing the sample. The rock sample is placed in a chamber of known volume. Helium is held in a reference chamber at known volume and pressure, typically 100 to 200 psi [689 to 1379 kPa]. The two chambers are connected, causing the helium to drop in pressure as it fills the sample chamber and the pores in the sample. The only volume not filled is the grain volume and the isolated pores. Neglecting the latter, the grain volume can then be calculated from Boyle's Law using the pressure before and after connecting the chambers and the chamber volumes.
1390Boyle's Law Single Cell, buoyancy, core plug, liquid saturation method, mercury displacement method, porosimeter, routine core analysis, summation of fluids method
1391None
1392None
1393--
1394backoff
13951.vb. [Drilling]
1396To unscrew drillstring components downhole. The drillstring, including drillpipe and the bottomhole assembly, are coupled by various threadforms known as connections, or tool joints. Often when a drillstring becomes stuck it is necessary to "back off" the string as deep as possible to recover as much of the string as possible. To facilitate the fishing or recovery operation, the backoff is usually accomplished by applying reverse torque and detonating an explosive charge inside a selected threaded connection. The force of the explosion enlarges the female (outer) thread enough that the threaded connection unscrews instantly. A torqueless backoff may be performed as well. In that case, tension is applied, and the threads slide by each other without turning when the explosive detonates. Backing off can also occur unintentionally.break out
1397None
1398break out
1399back off
1400--
1401bed wrap
14021.n. [Well Workover and Intervention]
1403The first layer of coiled tubing, slickline or wireline to be wound on the core of a reel drum or spool. The bed wrap helps secure the tubing string or slickline to the reel core and provides the foundation upon which subsequent wraps are laid as the drum is filled. A neat and secure bed wrap is necessary for proper spooling that will allow the drum to hold the maximum capacity without damaging the string.
1404coiled tubing
1405None
1406None
1407--
1408blind zone
14091.n. [Geophysics]
1410A layer or body of rock that cannot be detected by seismic refraction, typically because its velocity is lower than that of the overlying rocks; also known as a hidden layer.
1411refraction
1412None
1413None
1414--
1415blind zone
14162.n. [Geophysics]
1417A shadow zone, or a zone through which waves do not pass, or cannot be recorded, or in which reflections do not occur.
1418shadow zone
1419None
1420None
1421--
1422boyles law single cell
14231.n. [Formation Evaluation]
1424A technique for measuring the pore volume of a core sample by observing the change in pressure of helium introduced into the pore space. The rock sample is held in a core holder whose internal walls are elastomers, so that the only void space is the internal pore volume. With a suitable holder, the sample can be held under a confining stress. Helium is held in a reference cell at known volume and pressure, typically 100 to 200 psi [689 to 1379 kPa]. The helium is introduced to the core sample, dropping in pressure as it fills the connected pore space. The effective pore volume is obtained from Boyle's Law using the pressure before and after introduction of helium, and the reference volume.
1425Boyle's Law Double Cell, buoyancy, core plug, liquid saturation method, mercury displacement method, porosimeter, routine core analysis, summation of fluids method
1426None
1427None
1428--
1429back pressure valve
14301.n. [Well Completions]
1431A type of check valve, typically installed in the tubing hanger, to isolate the production tubing. The back-pressure valve is designed to hold pressure from below yet enable fluids to be pumped from above, as may be required for well-control purposes.
1432None
1433None
1434None
1435--
1436bel
14371.n. [Geophysics]
1438The unit of measurement to describe or compare the intensity of acoustic or electrical signal, named for American inventor Alexander Graham Bell (1847 to 1922). Measurements are typically given in tenths of a bel, or decibels. The logarithm of the ratio of the sound or signal to a standard provides the decibel measurement. Sounds on the order of one decibel are barely audible to humans but can cause pain when on the order of 1012 decibels. The symbol for the unit is B, but dB is the standard unit.
1439acoustic, decibel, signal
1440None
1441None
1442--
1443blind shear ram
14441.n. [Well Workover and Intervention]
1445A blowout preventer (BOP) closing element fitted with hardened tool steel blades designed to cut the drillpipe or tubing when the BOP is closed, and then fully close to provide isolation or sealing of the wellbore. A shear ram is normally used as a last resort to regain pressure control of a well that is flowing. Once the pipe is cut (or sheared) by the shear rams, it is usually left hanging in the BOP stack, and kill operations become more difficult. The joint of drillpipe or tubing is destroyed in the process, but the rest of the string is unharmed by the operation of shear rams.
1446blind ram, blow out preventer, BOP stack, kill, shear-seal BOP
1447blind shear ram, shear ram
1448None
1449--
1450brachistochrone
14511.n. [Geophysics]
1452The fastest route that a seismic ray can travel between two points, generally dictated by Fermat's principle.
1453Fermat's principle, minimum-time path, Snell's law
1454least-time path
1455None
1456--
1457backscatter
14581.n. [Geophysics]
1459A reflection phenomenon of energy in which a nonreflective surface, which is a surface that does not reflect energy coherently, randomly scatters energy. No coherent reflected energy can be identified and the energy is scattered in all directions, including back in the direction from which it came. For example, light can be scattered or redistributed by rough, nonreflective surfaces.
1460deconvolution, filter, wave
1461None
1462None
1463--
1464bell nipple
14651.n. [Drilling]
1466An enlarged pipe at the top of a casing string that serves as a funnel to guide drilling tools into the top of a well. The bell nipple is usually fitted with a side outlet to permit drilling fluids to flow back to the surface mud treating equipment through another inclined pipe called a flowline.
1467circulation system
1468None
1469None
1470--
1471blockage
14721.n. [Production Testing]
1473An obstruction in the pipeline, composed of asphaltenes, hydrates, waxes, scale and sand deposited on the internal wall of the pipeline forming a barrier to the normal flow of fluids. The conditions for blockage formation are mainly encountered in deepwater operations (low temperature and high pressure).
1474hydrate
1475None
1476None
1477--
1478breakdown pressure
14791.n. [Well Completions]
1480The pressure at which the rock matrix of an exposed formation fractures and allows fluid to be injected. The breakdown pressure is established before determining reservoir treatment parameters. Hydraulic fracturing operations are conducted above the breakdown pressure, while matrix stimulation treatments are performed with the treatment pressure safely below the breakdown pressure.
1481None
1482None
1483None
1484--
1485back stripping
14861.n. [Geophysics]
1487A modeling technique to assess the geologic history of rock layers through the use of geologic cross sections or seismic sections. Removal of the youngest layers of rock at the top of the section allows restoration of the underlying layers to their initial, undisturbed configurations. Successively older layers can be removed sequentially to further assess the effects of compaction, development of geologic structures and other processes on an area.
1488cross section
1489None
1490None
1491--
1492benthic
14931.adj. [Geology]
1494Pertaining to the environment and conditions of organisms living at the water bottom, or benthos. Also called benthonic.
1495abyssal, bathyal, littoral, neritic
1496None
1497None
1498--
1499blow out
15001.n. [Drilling]
1501An uncontrolled flow of reservoir fluids into the wellbore, and sometimes catastrophically to the surface. A blowout may consist of salt water, oil, gas or a mixture of these. Blowouts occur in all types of exploration and production operations, not just during drilling operations. If reservoir fluids flow into another formation and do not flow to the surface, the result is called an underground blowout. If the well experiencing a blowout has significant openhole intervals, it is possible that the well will bridge over (or seal itself with rock fragments from collapsing formations) downhole and intervention efforts will be averted.
1502None
1503None
1504blowout
1505--
1506breaker
15071.n. [Drilling Fluids]
1508A chemical that reduces the viscosity of a fluid by breaking long-chain molecules into shorter segments. Drilling fluids are commonly emulsified or contain long-chain molecules that have sufficient viscosity to carry cuttings to surface. After the drilling fluid has done its job, a breaker may be added to reduce the viscosity of the fluid by breaking down the long chain molecules into shorter molecules. A surfactant may be added to an emulsion to reduce its viscosity.
1509None
1510None
1511None
1512--
1513breaker
15142.n. [Well Workover and Intervention]
1515A chemical used to reduce the viscosity of specialized treatment fluids such as gels and foams. Breaking down the fluid viscosity may be desirable either as part of a treatment, such as allowing flow back of the spent treatment fluid, or following a treatment as part of the fluid-disposal process. Depending on the application, a breaker of predictable performance may be incorporated into the treatment fluid for downhole activation, or be added directly to the returned fluid for immediate effect at surface.
1516gel
1517None
1518None
1519--
1520backup curve
15211.n. [Formation Evaluation]
1522An extra curve on a log, designed to appear when the standard curve goes off track. For example, if the standard gamma ray curve is presented on a scale of 0 to 200 gAPI units, the backup curve may be scaled from 200 to 400 gAPI units. Alternatively, if the standard resistivity log is presented on a scale of 0 to 50 ohm-m, the backup curve might be presented on a scale of 0 to 500 ohm-m in the same track but be blanked off for readings below 50 ohm-m. The backup curve usually has the same coding as the standard curve but a different line weight.
1523track
1524None
1525None
1526--
1527bentonite
15281.n. [Geology]
1529A material composed of clay minerals, predominantly montmorillonite with minor amounts of other smectite group minerals, commonly used in drilling mud. Bentonite swells considerably when exposed to water, making it ideal for protecting formations from invasion by drilling fluids. Montmorillonite forms when basic rocks such as volcanic ash in marine basins are altered.
1530clay, mineral, montmorillonite, smectite
1531None
1532None
1533--
1534bentonite
15352.n. [Drilling Fluids]
1536A clay mineral that is composed principally of three-layer clays, such as montmorillonite, and widely used as a mud additive for viscosity and filtration control. Commercial bentonite ores vary widely in amount and quality of the swelling clay, sodium montmorillonite. Ores of lower quality, those with more calcium-type montmorillonite, are treated during grinding by adding one or more of the following: sodium carbonate, long-chain synthetic polymers, carboxymethylcellulose (CMC), starch or polyphosphates. These help make the final product meet quality specifications. Unfortunately, the additives may not remain effective in "the real mud world" when in use at the rig due to hardness ions in the water, high temperature, bacterial attack, mechanical shear-degradation and other factors that can render these additives ineffective.
1537cation-exchange capacity, clay extender, conventional mud, hectorite, low-solids mud, low-yield clay, native clay, organophilic clay, peptized clay, phosphate salt, prehydrated bentonite, seawater mud, smectite, smectite clay, sulfonated polystyrene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, water, oil and solids test
1538None
1539None
1540--
1541blow out preventer
15421.n. [Drilling]
1543A large valve at the top of a well that may be closed if the drilling crew loses control of formation fluids. By closing this valve (usually operated remotely via hydraulic actuators), the drilling crew usually regains control of the reservoir, and procedures can then be initiated to increase the mud density until it is possible to open the BOP and retain pressure control of the formation. BOPs come in a variety of styles, sizes and pressure ratings. Some can effectively close over an open wellbore, some are designed to seal around tubular components in the well (drillpipe, casing or tubing) and others are fitted with hardened steel shearing surfaces that can actually cut through drillpipe. Since BOPs are critically important to the safety of the crew, the rig and the wellbore itself, BOPs are inspected, tested and refurbished at regular intervals determined by a combination of risk assessment, local practice, well type and legal requirements. BOP tests vary from daily function testing on critical wells to monthly or less frequent testing on wells thought to have low probability of well control problems.
1544None
1545None
1546blowout preventer
1547--
1548bridge
15491.n. [Drilling]
1550The gangplank or stairway connecting a jackup rig to a fixed platform.
1551None
1552None
1553None
1554--
1555bridge
15562.vb. [Drilling]
1557To intentionally or accidentally plug off pore spaces or fluid paths in a rock formation, or to make a restriction in a wellbore or annulus. A bridge may be partial or total, and is usually caused by solids (drilled solids, cuttings, cavings or junk) becoming lodged together in a narrow spot or geometry change in the wellbore.
1558blowout, drill solids, formation damage
1559None
1560None
1561--
1562bridge
15633.n. [Well Completions]
1564A wellbore obstruction caused by a buildup of material such as scale, wellbore fill or cuttings that can restrict wellbore access or, in severe cases, eventually close the wellbore.
1565None
1566None
1567None
1568--
1569backward multiple contact test
15701.n. [Enhanced Oil Recovery]
1571A laboratory test to determine the phase envelope between oil and enriched gas. The test is conducted by equilibrating an oil sample several times with fresh samples of gas. Intermediate components are stripped from the gas by multiple contacts with the oil. The test also indicates how many contacts are required before the oil with added intermediate components becomes miscible with the gas. The molar ratios at each contact step are typically designed using PVT simulation software that incorporates the fluid composition from the previous contact.
1572condensing drive, forward multiple-contact test, miscible
1573None
1574None
1575--
1576bgg
15771.n. [Drilling]
1578An average or baseline measure of gas entrained in circulating mud. This baseline trend pertains to gas that is liberated downhole while drilling through a uniform lithologic interval at a constant rate of penetration. The gas is typically obtained from a suction line above the gas trap located immediately upstream of the shale shaker screens, where the gas evolves out of the mud.Oil-base mud systems tend to produce higher background gas values than do water-base muds. Deviations from the background gas trend likely indicate changes in porosity or permeability, or changes in drilling conditions; any of which merits further investigation. A drift or gradual shift of the background gas trend toward higher values may indicate a slow gas influx into the mud column, which can eventually lead to a kick or blowout. When annotated on mud logs, background gas is usually abbreviated as BGG.
1579None
1580None
1581background gas
1582--
1583blowing the drip
15841.n. [Production Facilities]
1585Opening the valve on a drip to allow natural gas to blow or clear the pipe of all liquids.
1586None
1587None
1588None
1589--
1590brine
15911.n. [Geology]
1592Water containing more dissolved inorganic salt than typical seawater.
1593connate water, formation water, fresh water, interstitial water
1594None
1595None
1596--
1597brine
15982.n. [Drilling]
1599Saline liquid usually used in completion operations and, increasingly, when penetrating a pay zone. Brines are preferred because they have higher densities than fresh water but lack solid particles that might damage producible formations. Classes of brines include chloride brines (calcium and sodium), bromides and formates.
1600aquifer, completion fluid, producing formation
1601None
1602None
1603--
1604brine
16053.n. [Drilling Fluids]
1606A general term that refers to various salts and salt mixtures dissolved in an aqueous solution. Brine can be used more strictly, however, to refer to solutions of sodium chloride. We prefer to use brine as a general term. The emulsified calcium chloride [CaCl2] solution (or any other saline phase) in an oil mud is referred to as "brine" or "brine phase." The oil/brine ratio, abbreviated OBR, is used to compare solids content and salinities of oil muds. Clear brines are salt solutions that have few or no suspended solids.
1607balanced-activity oil mud, bromide brine, calcium bromide, calcium carbonate, calcium chloride, carboxymethyl hydroxyethylcellulose, cesium acetate, drill-in fluid, formate, guar gum, hydrometer, hydroxyethylcellulose, hydroxypropyl starch, PVT, synthetic/brine ratio, undersaturated fluid
1608clear brine
1609None
1610--
1611brine
16124.n. [Well Completions]
1613A water-based solution of inorganic salts used as a well-control fluid during the completion and workover phases of well operations. Brines are solids free, containing no particles that might plug or damage a producing formation. In addition, the salts in brine can inhibit undesirable formation reactions such as clay swelling. Brines are typically formulated and prepared for specific conditions, with a range of salts available to achieve densities ranging from 8.4 to over 20 lbm/gal (ppg) [1.0 to 2.4 g/cmo]. Common salts used in the preparation of simple brine systems include sodium chloride, calcium chloride and potassium chloride. More complex brine systems may contain zinc, bromide or iodine salts. These brines are generally corrosive and costly.
1614producing formation
1615None
1616None
1617--
1618brine
16195.n. [Production Facilities]
1620Water containing salts in solution, such as sodium, calcium or bromides. Brine is commonly produced along with oil. The disposal of oilfield brine is usually accomplished by underground injection into salt-water saturated formations or by evaporation in surface pits.
1621None
1622None
1623None
1624--
1625bactericide
16261.n. [Drilling Fluids]
1627An additive that kills bacteria. Bactericides are commonly used in water muds containing natural starches and gums that are especially vulnerable to bacterial attack. Bactericide choices are limited and care must be taken to find those that are effective yet approved by governments and by company policy.Bactericides, also called biocides, can be used to control sulfate-reducing bacteria, slime-forming bacteria, iron-oxidizing bacteria and bacteria that attacks polymers in fracture and secondary recovery fluids. In polymers, the degradation of the fluid is controlled, thus avoiding the formation of a large biomass, which could plug the formation and reduce permeability.
1628anaerobic, bioassay, formaldehyde, guar gum, LC50, paraformaldehyde, polymer, starch, XC polymer
1629preservative
1630biocide
1631--
1632bhct
16331.n. [Drilling]
1634The temperature of the circulating fluid (air, mud, cement or water) at the bottom of the wellbore after several hours of circulation. This temperature is lower than the bottomhole static temperature. Therefore, in extremely harsh environments, a component or fluid that would not ordinarily be suitable under bottomhole static conditions may be used with great care in circulating conditions. Similarly, a high-temperature well may be cooled down in an attempt to allow logging tools to function. The BHCT is also important in the design of operations to cement casing because the setting time for cement is temperature-dependent. The BHCT and bottomhole static temperature (BHST) are important parameters when placing large volumes of temperature-sensitive treatment fluids.
1635None
1636None
1637bottomhole circulating temperature
1638--
1639blowout
16401.n. [Drilling]
1641Uncontrolled flow of formation fluids from a well. An uncontrolled flow of formation fluids from the wellbore or into lower pressured subsurface zones (underground blowout). Uncontrolled flows cannot be contained using previously installed barriers and require specialized services intervention.A blowout may consist of water, oil, gas or a mixture of these. Blowouts may occur during all types of well activities and are not limited to drilling operations. In some circumstances, it is possible that the well will bridge over, or seal itself with rock fragments from collapsing formations downhole.
1642abnormal pressure, blowout preventer, openhole, pressure hunt, turnkey
1643None
1644None
1645--
1646broach
16471.n. [Well Workover and Intervention]
1648A downhole tool used to repair the internal diameter of the production tubing where a slight collapse or a dent has occurred. Cutting profiles on a broach removes the tubing-wall material to allow subsequent passage of tools and equipment of a prescribed diameter.
1649None
1650None
1651None
1652--
1653bad hole
16541.n. [Formation Evaluation]
1655A borehole that is not to gauge or is rugose. The term usually refers to the detrimental effect that such a borehole has on the response of logging measurements, in particular pad tools like the density or micro-resistivity. The existence of bad hole is usually determined by a caliper log and on various secondary measurements such as delta rho.
1656cave effect, corkscrew hole, rugosity
1657None
1658None
1659--
1660bhp
16611.n. [Drilling]
1662The pressure, usually measured in pounds per square inch (psi), at the bottom of the hole. This pressure may be calculated in a static, fluid-filled wellbore with the equation:BHP = MW * Depth * 0.052where BHP is the bottomhole pressure in pounds per square inch, MW is the mud weight in pounds per gallon, Depth is the true vertical depth in feet, and 0.052 is a conversion factor if these units of measure are used. For circulating wellbores, the BHP increases by the amount of fluid friction in the annulus. The BHP gradient should exceed the formation pressure gradient to avoid an influx of formation fluid into the wellbore.On the other hand, if BHP (including the added fluid friction pressure of a flowing fluid) is too high, a weak formation may fracture and cause a loss of wellbore fluids. The loss of fluid to one formation may be followed by the influx of fluid from another formation.
1663None
1664None
1665bottomhole pressure
1666--
1667blowout preventer
16681.n. [Drilling]
1669A large valve at the top of a well that may be closed if the drilling crew loses control of formation fluids. By closing this valve (usually operated remotely via hydraulic actuators), the drilling crew usually regains control of the reservoir, and procedures can then be initiated to increase the mud density until it is possible to open the BOP and retain pressure control of the formation. BOPs come in a variety of styles, sizes and pressure ratings. Some can effectively close over an open wellbore, some are designed to seal around tubular components in the well (drillpipe, casing or tubing) and others are fitted with hardened steel shearing surfaces that can actually cut through drillpipe. Since BOPs are critically important to the safety of the crew, the rig and the wellbore itself, BOPs are inspected, tested and refurbished at regular intervals determined by a combination of risk assessment, local practice, well type and legal requirements. BOP tests vary from daily function testing on critical wells to monthly or less frequent testing on wells thought to have low probability of well control problems.
1670annular blowout preventer, blowout, BOP stack, casing string, drilling break, hook load, inside blowout preventer, kill line, mud density, nipple down, pipe ram, ram blowout preventer, shear ram, surface casing, underground blowout, wildcat
1671None
1672BOP
1673--
1674brownfield
16751.n. [Enhanced Oil Recovery]
1676An oil or gas accumulation that has matured to a production plateau or even progressed to a stage of declining production. Operating companies seek to extend the economic producing life of the field using cost-effective, low-risk technologies. Stimulation or refracturing operations, completing additional zones, and installing artificial lift equipment are a few technologies commonly applied in brownfields before any drilling options are attempted.
1677None
1678None
1679None
1680--
1681balanced activity oil mud
16821.n. [Drilling Fluids]
1683An oil-base mud in which the activity, or vapor pressure, of the brine phase is balanced with that of the formations drilled. Although long shale sections may not have a constant value for vapor pressure, aw, the oil mud will adjust osmotically to achieve an "average" aw value. Dynamic (autopilot) balance of mud salinity and drilled shales is maintained because as water moves into or out of the mud, it also moves out of or into the shale. As water transfer continues during drilling, the mud's water phase will be either diluted or concentrated in CaCl2 as needed to match the average aw value of the shale section and cuttings exposed to the mud.Reference:Chenevert ME: "Shale Control With Balanced-Activity Oil-Continuous Muds," Journal of Petroleum Technology 33, no. 11 (November 1970): 1370-1378.
1684None
1685None
1686balanced-activity oil mud
1687--
1688bhst
16891.n. [Drilling]
1690The temperature of the undisturbed formation at the final depth in a well. The formation cools during drilling and most of the cooling dissipates after about 24 hours of static conditions, although it is theoretically impossible for the temperature to return to undisturbed conditions. This temperature is measured under static conditions after sufficient time has elapsed to negate any effects from circulating fluids. Tables, charts and computer routines are used to predict BHST as functions of depth, geographic area and various time functions. The BHST is generally higher than the bottomhole circulating temperature, and can be an important factor when using temperature-sensitive tools or treatments.
1691bottomhole static temperature
1692None
1693None
1694--
1695blpd
16961.n. [Production Testing]
1697Abbreviation for barrels of liquid per day, usually used in reference to total production of oil and water from a well. The volume of a barrel is equivalent to 42 US gallons.
1698barrel equivalent
1699None
1700barrels of liquid per day
1701--
1702brute stack
17031.n. [Geophysics]
1704A processed seismic record that contains traces from a common midpoint that have been added together but has undergone only cursory velocity analysis, so the normal-moveout correction is a first attempt. Typically, no static corrections are made before the brute stack.
1705processing, static correction, trace
1706None
1707None
1708--
1709balanced activity oil mud
17101.n. [Drilling Fluids]
1711An oil-base mud in which the activity, or vapor pressure, of the brine phase is balanced with that of the formations drilled. Although long shale sections may not have a constant value for vapor pressure, aw, the oil mud will adjust osmotically to achieve an "average" aw value. Dynamic (autopilot) balance of mud salinity and drilled shales is maintained because as water moves into or out of the mud, it also moves out of or into the shale. As water transfer continues during drilling, the mud's water phase will be either diluted or concentrated in CaCl2 as needed to match the average aw value of the shale section and cuttings exposed to the mud.Reference:Chenevert ME: "Shale Control With Balanced-Activity Oil-Continuous Muds," Journal of Petroleum Technology 33, no. 11 (November 1970): 1370-1378.
1712activity of aqueous solutions, calcium chloride, Chenevert Method, diesel-oil mud, humidity, hygrometer, inhibitive mud, methylglucoside drilling fluid, oil-mud emulsifier, osmosis, silicate mud
1713None
1714None
1715--
1716big hole charge
17171.n. [Perforating]
1718A perforating charge designed to create perforations with a large-diameter entrance hole. These charges typically are used in sand control completions, in which efficient placement of the gravel pack treatment within the perforation tunnel is crucial. Altering the explosive charge design and materials creates a larger diameter entrance hole on the perforation while reducing the depth of penetration. However, gravel-pack treatments generally are applied in high-permeability formations where perforation tunnel length is less important. Wells that are to be hydraulically fractured also can benefit from larger perforations since the effective penetration is significantly increased by a high-conductivity fracture.
1719None
1720None
1721big-hole charge
1722--
1723bod
17241.n. [Drilling Fluids]
1725The amount of oxygen consumed by biodegradation processes during a standardized test. The test usually involves degradation of organic matter in a discarded waste or an effluent.
1726None
1727None
1728biochemical oxygen demand
1729--
1730bubble count
17311.n. [Production Logging]
1732The frequency with which a local probe detects a change from one type of fluid to another. For example, if water is the continuous phase, the probe will respond digitally each time a bubble of oil or gas passes it. The average frequency of change is the bubble count rate, or bubble count. In this example, an increasing bubble count means an increasing oil or gas velocity. Bubble velocity can be calculated from bubble count and bubble size, the latter being estimated from an empirical correlation with water holdup. The depth at which the first bubbles are counted is a sensitive indicator of the lowest hydrocarbon entry.Since the bubble count is based on local probe measurements, both bubble count and bubble velocity can be presented as images, similar to the holdup image.
1733electric probe, local holdup, optical probe, production log, velocity image
1734None
1735None
1736--
1737ball catcher
17381.n. [Well Completions]
1739A downhole device or assembly used to catch and retain balls used to actuate ball-operated tools or equipment. Following activation, some ball-operated tools incorporate a means of ejecting the activation ball to regain a fullbore flow path. In such cases, the ball can be retained in a ball catcher.
1740drop ball
1741None
1742None
1743--
1744big hole charge
17451.n. [Perforating]
1746A perforating charge designed to create perforations with a large-diameter entrance hole. These charges typically are used in sand control completions, in which efficient placement of the gravel pack treatment within the perforation tunnel is crucial. Altering the explosive charge design and materials creates a larger diameter entrance hole on the perforation while reducing the depth of penetration. However, gravel-pack treatments generally are applied in high-permeability formations where perforation tunnel length is less important. Wells that are to be hydraulically fractured also can benefit from larger perforations since the effective penetration is significantly increased by a high-conductivity fracture.
1747hydraulic fracturing
1748None
1749big hole charge
1750--
1751body relief valve
17521.n. [Production]
1753An optional relief valve installed on ball valves used in liquid service to provide for the relief of excess body pressure caused by thermal expansion.
1754ball valve, relief valve
1755None
1756None
1757--
1758bubble effect
17591.n. [Geophysics]
1760Bubble pulses or bubble noise that affect data quality. In marine seismic acquisition, the gas bubble produced by an air gun oscillates and generates subsequent pulses that cause source-generated noise. Careful use of multiple air guns can cause destructive interference of bubble pulses and alleviate the bubble effect. A cage, or a steel enclosure surrounding a seismic source, can be used to dissipate energy and reduce the bubble effect.
1761cavitation
1762None
1763None
1764--
1765ball diverter
17661.n. [Well Workover and Intervention]
1767Small 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.
1768chemical diversion, mechanical diversion
1769None
1770None
1771--
1772bilinear flow
17731.n. [Well Testing]
1774A flow regime resulting from combined simultaneous linear flow in perpendicular directions. This flow regime is seen most commonly in tests of hydraulically fractured wells and occurs for finite-conductivity fracture where linear flow exists both in the fracture and to the fracture plane. This flow regime is recognized as a 1/4 slope in the pressure derivative on the log-log diagnostic plot. Its presence enables determination of the fracture conductivity.
1775hydraulic fracturing
1776None
1777None
1778--
1779boltzmann probability distribution
17801.n. [Reservoir Characterization]
1781One of a number of possible distributions that may occur when the results of events are plotted. Boltzmann distributions were originally described from theoretical consideration on the probable interactions of molecules. It has been used in simulation of annealing and can be used for studying perturbations in geostatistical models.
1782distribution, geostatistical modeling, probability
1783None
1784None
1785--
1786bubble flow
17871.n. [Well Completions]
1788A multiphase fluid flow regime characterized by the gas phase being distributed as bubbles through the liquid phase. In a producing wellbore where the bubbles are uniformly distributed, there is little relative motion between the phases. Where the bubbles congregate and combine to form a less uniform distribution of the gas phase, some slippage will occur between the phases with the gas tending to cut through the liquid phase.
1789flow regime, slip
1790None
1791None
1792--
1793bubble flow
17942.n. [Production Logging]
1795A multiphase flow regime in pipes in which one fluid moves as small dispersed bubbles through a continuous fluid. The relative velocity of the bubbles depends mainly on the difference in density between the two fluids. Bubble flow normally occurs at low flow rate and low holdup of the bubbly fluid. As the velocity of the continuous fluid increases, the bubbles are dispersed into smaller, more widely separated bubbles. This is known as a dispersed or finely dispersed bubble flow, or sometimes dispersed flow.
1796flow structure, plug flow, slug flow
1797dispersed bubble flow
1798None
1799--
1800ball dropper
18011.n. [Well Workover and Intervention]
1802The device used to inject ball sealers into the treatment fluid as it is pumped through the surface treating lines.
1803None
1804None
1805None
1806--
1807bimetallic corrosion
18081.n. [Enhanced Oil Recovery]
1809A type of corrosion in which two different metals are placed in contact in a corrosive environment. A small electric current flows from one piece of metal to the other, accelerating the corrosion rate of the more reactive of the two metals. Bimetallic corrosion is sometimes found when new pipe is added to old pipelines. The old pipeline covered by oxide and rust is cathodic to the new pipe, thus accelerating the corrosion rate in the new pipe. Another type of bimetallic corrosion is ringworm corrosion.
1810corrosion control
1811None
1812None
1813--
1814bond log
18151.n. [Drilling Fluids]
1816A log that uses the variations inamplitudeof anacousticsignaltraveling down thecasingwall between a transmitter and receiverto determine the quality ofcementbond on the exterior casing wall.
1817cement bond log
1818None
1819None
1820--
1821bubble point
18221.n. [Well Testing, Enhanced Oil Recovery]
1823The pressure and temperature conditions at which the first bubble of gas comes out of solution in oil. At discovery, all petroleum reservoir oils contain some natural gas in solution. Often the oil is saturated with gas when discovered, meaning that the oil is holding all the gas it can at the reservoir temperature and pressure, and that it is at its bubblepoint. Occasionally, the oil will be undersaturated. In this case, as the pressure is lowered, the pressure at which the first gas begins to evolve from the oil is defined as the bubblepoint.
1824None
1825None
1826bubblepoint
1827--
1828ball launcher
18291.n. [Well Workover and Intervention]
1830The device used to inject ball sealers into the treatment fluid as it is pumped through the surface treating lines.
1831None
1832None
1833ball dropper
1834--
1835bimetallism
18361.n. [Formation Evaluation]
1837The electromagnetic force created by two different metals in contact with each other. If two such metals are in contact in a logging tool, and also communicate along a conductive borehole, then a potential drop is generated in the borehole. This potential drop will appear on the spontaneous potential (SP) log, where it can be confused with the electrochemical potential. Since the magnitude of the drop depends on the formation resistivity, the effect of bimetallism is often seen as a resistivity log superimposed on the normal SP. Under usual circumstances, the effect of bimetallism on the SP is small, and care is taken to avoid it.
1838shale baseline, static spontaneous potential
1839None
1840None
1841--
1842bond number
18431.n. [Enhanced Oil Recovery]
1844A dimensionless group used in analysis of fluid flow that characterizes the ratio of gravitational forces to surface or interfacial tension forces. It is usually denoted Nb in the oil field and Bo in chemical engineering. A value of Nb <<1 implies the flow in question is only weakly dependent on gravitational forces, whereas Nb >>1 implies gravitational forces dominate over interfacial forces.Bond number equation:Nb = Bo = (Δρ g b2) / σ,whereNb = Bo = Bond numberΔρ = density difference between the two phasesg = acceleration due to gravityb = a characteristic length scale of the flow geometryσ = surface or interfacial tension.
1845None
1846Eötvös number
1847None
1848--
1849bubblepoint
18501.n. [Enhanced Oil Recovery, Well Testing]
1851The pressure and temperature conditions at which the first bubble of gas comes out of solution in oil. At discovery, all petroleum reservoir oils contain some natural gas in solution. Often the oil is saturated with gas when discovered, meaning that the oil is holding all the gas it can at the reservoir temperature and pressure, and that it is at its bubblepoint. Occasionally, the oil will be undersaturated. In this case, as the pressure is lowered, the pressure at which the first gas begins to evolve from the oil is defined as the bubblepoint.
1852reservoir pressure
1853None
1854bubble point
1855--
1856ball operated
18571.adj. [Well Completions]
1858Describing a mechanism or system that is actuated by a ball that is dropped or pumped through the tubing string. Once located on a landing seat, the tool mechanism is generally actuated by hydraulic pressure.
1859None
1860None
1861ball-operated
1862--
1863bin
18641.n. [Geophysics]
1865A subdivision of a seismic survey. The area of a three-dimensional survey is divided into bins, which are commonly on the order of 25 m [82 ft] long and 25 m wide; traces are assigned to specific bins according to the midpoint between the source and the receiver, reflection point or conversion point. Bins are commonly assigned according to common midpoint (CMP), but more sophisticated seismic processing allows for other types of binning. Traces within a bin are stacked to generate the output trace for that bin. Data quality depends in part on the number of traces per bin, or the fold.
1866fold, stack, three-dimensional seismic data, trace
1867None
1868None
1869--
1870bin
18712.vb. [Geophysics]
1872To sort seismic data into small areas according to the midpoint between the source and the receiver, reflection point or conversion point prior to stacking.
1873stack
1874None
1875None
1876--
1877boolean simulation
18781.n. [Reservoir Characterization]
1879The development of a reservoir model by the use of objects. Reservoir models may be developed by adding together a series of objects (such as channel belts) in a fashion that honors the well data (logs, cores, etc.) and satisfies all the geostatistical requirements of the model. Such models may be used to simulate the behavior of the fluids in a reservoir.
1880core, geostatistics, log, reservoir modeling
1881None
1882None
1883--
1884bucking coil
18851.n. [Formation Evaluation]
1886A coil in an induction logging tool designed to buck out, or reduce, the direct coupling between transmitter and receiver coils. The direct coupling signal is far larger than the formation signal. The bucking coil is wound with the opposite polarity to the main receiver coil, and placed in series with it at a location that minimizes the direct coupling. The combination of transmitter, main receiver and bucking coils is known as a mutually balanced array.
18876FF40, array induction
1888None
1889None
1890--
1891ball out
18921.n. [Well Workover and Intervention]
1893A condition that may occur during ball diversion treatments in which all open perforations capable of receiving fluid are sealed. Ballout is signified by a rapid increase in treating pressure. Maintaining the treatment pressure may result in the breakdown and subsequent treatment of plugged perforations. If no further injection is possible, the pressure must be released to unseat the ball sealers, at which time the treatment will be terminated.
1894None
1895None
1896None
1897--
1898bingham plastic model
18991.n. [Drilling Fluids]
1900A two-parameter rheological model widely used in the drilling fluids industry to describe flow characteristics of many types of muds. It can be described mathematically as follows:τ = YP + PV(γ),whereτ = shear stressγ = shear rateYP = yield pointPV = plastic viscosity.Fluids obeying this model are called Bingham plastic fluids and exhibit a linear shear-stress, shear-rate behavior after an initial shear stress threshold has been reached. Plastic viscosity (PV) is the slope of the line and yield point (YP) is the threshold stress. PV should be as low as possible for fast drilling and is best achieved by minimizing colloidal solids. YP must be high enough to carry cuttings out of the hole, but not so large as to create excessive pump pressure when starting mud flow. YP is adjusted by judicious choices of mud treatments. The direct-indicating rotational rheometer was specifically designed to apply the Bingham plastic fluid model.
1901apparent viscosity, clay-water interaction, deflocculant, direct-indicating viscometer, Herschel-Bulkley fluid, non-Newtonian fluid, plastic fluid, power-law fluid, pseudoplastic, rheological property, V-G meter, viscosity
1902None
1903None
1904--
1905booster
19061.n. [Perforating]
1907A small metal tube containing secondary high explosive that is crimped onto the end of the detonating cord. This explosive component is designed to provide reliable detonation transfer between perforating guns or other explosive devices, and often serves as an auxiliary explosive charge to ensure detonation.
1908perforating gun
1909None
1910None
1911--
1912buffalo head
19131.n. [Shale Gas, Well Completions, Well Workover and Intervention]
1914A flow cross installed on top of a frac tree where treating iron is connected and treatment fluid enters the frac tree.
1915None
1916None
1917frac head, goat head
1918--
1919ball sealers
19201.n. [Well Workover and Intervention, Well Completions]
1921Small 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.
1922chemical diversion, mechanical diversion
1923None
1924None
1925--
1926bioaccumulation
19271.n. [Drilling Fluids]
1928The concentration of a particular substance in a living organism, possibly with harmful effects. The likelihood of this occurring is expressed as the bioaccumulation potential and can be estimated by the octanol/water partition coefficient, expressed as logPOW. This test is commonly required on drilling fluid additives in the North Sea area and other countries following the Oslo and Paris Commission (OSPAR) regulations. Values of logPOW below 3 indicate no bioaccumulation tendency; values between 3 and 6 indicate that bioaccumulation is possible, providing the substance is small enough to pass through the cell wall (mol. wt. < 600). This may be confirmed by a bioconcentration test in which a population of animals is exposed to the product.
1929OSPAR
1930bioconcentration
1931None
1932--
1933bop
19341.n. [Drilling]
1935A large valve at the top of a well that may be closed if the drilling crew loses control of formation fluids. By closing this valve (usually operated remotely via hydraulic actuators), the drilling crew usually regains control of the reservoir, and procedures can then be initiated to increase the mud density until it is possible to open the BOP and retain pressure control of the formation. BOPs come in a variety of styles, sizes and pressure ratings. Some can effectively close over an open wellbore, some are designed to seal around tubular components in the well (drillpipe, casing or tubing) and others are fitted with hardened steel shearing surfaces that can actually cut through drillpipe. Since BOPs are critically important to the safety of the crew, the rig and the wellbore itself, BOPs are inspected, tested and refurbished at regular intervals determined by a combination of risk assessment, local practice, well type and legal requirements. BOP tests vary from daily function testing on critical wells to monthly or less frequent testing on wells thought to have low probability of well control problems.
1936choke line
1937None
1938blowout preventer
1939--
1940buffer
19411.n. [Drilling Fluids]
1942A chemical system that resists a change in pH. It comprises three components: water, weak acid (or weak base) and salt of the weak acid (or salt of weak base). In a buffered system, the concentration of H+ and OH- ions remain relatively constant because they are in equilibrium with one or more of the other two components, even with the addition of acids or bases.
1943buffer solution, buffered mud, hydrolysis, pH test, phosphate salt, total hardness test
1944None
1945None
1946--
1947buffer
19482.n. [Well Workover and Intervention]
1949A chemical used to adjust and control the pH of stimulation fluids. Gels and complex polymer fluids are sensitive to pH changes, especially during the mixing phase when the dispersion and hydration of some polymers require specific pH conditions. In addition, the performance of crosslinked fluids is optimized over a relatively narrow pH range. Buffers, added to the aqueous phase before mixing, adjust the base-fluid pH to achieve a stable treatment fluid with the desired characteristics and predictable performance.
1950gel
1951None
1952None
1953--
1954ball valve
19551.n. [Production]
1956A valve using a spherical closure element (ball) which is rotated through 90° to open and close the valve.
1957None
1958None
1959None
1960--
1961bioassay
19621.n. [Drilling Fluids]
1963A laboratory test or other assessment utilizing a living organism, such as mysid shrimp, to determine the effect of a condition to which the organism is exposed. Such tests are performed under controlled environmental conditions and duration. Bioassay tests of drilling fluids are required by governmental agencies throughout the world prior to discharge of mud or cuttings. The organisms used in bioassays are those found in the area that would be most affected by contact with the proposed drilling fluid. The dosage of interest is typically the lethal concentration, known as LC50, that will kill 50% of the population of organisms in a given period of time. Chronic bioassay tests indicate sublethal effects, such as changes in growth or reproduction of the organism over a longer period of time.
1964bactericide, emulsion mud, EPA, LC50, Minerals Management Service, NPDES, potassium mud
1965None
1966None
1967--
1968bop stack
19691.n. [Drilling]
1970A set of two or more BOPs used to ensure pressure control of a well. A typical stack might consist of one to six ram-type preventers and, optionally, one or two annular-type preventers. A typical stack configuration has the ram preventers on the bottom and the annular preventers at the top. The configuration of the stack preventers is optimized to provide maximum pressure integrity, safety and flexibility in the event of a well control incident. For example, in a multiple ram configuration, one set of rams might be fitted to close on 5-in. diameter drillpipe, another set configured for 4 1/2-in. drillpipe, a third fitted with blind rams to close on the openhole and a fourth fitted with a shear ram that can cut and hang-off the drillpipe as a last resort. It is common to have an annular preventer or two on the top of the stack since annulars can be closed over a wide range of tubular sizes and the openhole, but are typically not rated for pressures as high as ram preventers. The BOP stack also includes various spools, adapters and piping outlets to permit the circulation of wellbore fluids under pressure in the event of a well control incident.
1971annular blowout preventer, blind ram, blowout preventer, casinghead, cellar, drilling riser, dynamic positioning, kill line, nipple up, ram blowout preventer, ram preventer, shut-in bottomhole pressure, shut-in pressure, Texas deck
1972None
1973None
1974--
1975buggy vibro
19761.n. [Geophysics]
1977A vibrator truck equipped with wide tires to allow access to rugged or soggy terrain while causing less damage to the environment.
1978None
1979None
1980None
1981--
1982ball operated
19831.adj. [Well Completions]
1984Describing a mechanism or system that is actuated by a ball that is dropped or pumped through the tubing string. Once located on a landing seat, the tool mechanism is generally actuated by hydraulic pressure.
1985drop ball
1986None
1987None
1988--
1989biochemical oxygen demand
19901.n. [Drilling Fluids]
1991The amount of oxygen consumed by biodegradation processes during a standardized test. The test usually involves degradation of organic matter in a discarded waste or an effluent.
1992chemical oxygen demand
1993None
1994BOD
1995--
1996bopd
19971.n. [Production Testing]
1998Abbreviation for barrels of oil per day, a common unit of measurement for volume of crude oil. The volume of a barrel is equivalent to 42 US gallons.
1999None
2000None
2001barrels of oil per day
2002--
2003buildup test
20041.n. [Well Testing]
2005The measurement and analysis of (usually) bottomhole pressure data acquired after a producing well is shut in. Buildup tests are the preferred means to determine well flow capacity, permeability thickness, skin effect and other information. Soon after a well is shut in, the fluid in the wellbore usually reaches a somewhat quiescent state in which bottomhole pressure rises smoothly and is easily measured. This allows interpretable test results.
2006drawdown test
2007None
2008None
2009--
2010ballout
20111.n. [Well Workover and Intervention]
2012A condition that may occur during ball diversion treatments in which all open perforations capable of receiving fluid are sealed. Ballout is signified by a rapid increase in treating pressure. Maintaining the treatment pressure may result in the breakdown and subsequent treatment of plugged perforations. If no further injection is possible, the pressure must be released to unseat the ball sealers, at which time the treatment will be terminated.
2013None
2014None
2015None
2016--
2017biocide
20181.n. [Drilling Fluids]
2019An additive that kills bacteria. Bactericides are commonly used in water muds containing natural starches and gums that are especially vulnerable to bacterial attack. Bactericide choices are limited and care must be taken to find those that are effective yet approved by governments and by company policy.Bactericides, also called biocides, can be used to control sulfate-reducing bacteria, slime-forming bacteria, iron-oxidizing bacteria and bacteria that attacks polymers in fracture and secondary recovery fluids. In polymers, the degradation of the fluid is controlled, thus avoiding the formation of a large biomass, which could plug the formation and reduce permeability.
2020anaerobic, bactericide, formaldehyde, preservative
2021None
2022None
2023--
2024borehole
20251.n. [Drilling]
2026The wellbore itself, including the openhole or uncased portion of the well. Borehole may refer to the inside diameter of the wellbore wall, the rock face that bounds the drilled hole.
2027inside diameter, openhole
2028wellbore
2029None
2030--
2031bulk relaxation
20321.n. [Formation Evaluation]
2033In a nuclear magnetic resonance measurement, the loss of coherent energy by hydrogen atoms as they interact with each other in bulk fluids. Bulk relaxation in fluids is caused primarily by fluctuating local magnetic fields arising from the random tumbling motion of neighboring molecules. Local field fluctuations may be high, but the fast movement of molecules tends to average these out. Thus the bulk relaxation depends strongly on the rate of movement and is affected by temperature and viscosity.In water-wet rocks, hydrocarbons do not touch the pore walls and are not affected by surface relaxation. Thus the T1 and T2 of hydrocarbons are the result only of bulk and diffusion relaxation. This is an important feature of NMR logging. Based on this feature, direct hydrocarbon-typing techniques have been developed for the detection and characterization of hydrocarbons.
2034longitudinal relaxation, nuclear magnetic resonance, relaxation time, transverse relaxation
2035None
2036None
2037--
2038bank firing
20391.n. [Perforating]
2040A technique in which several perforating guns are run on a single trip into the well, and then all are fired simultaneously.
2041perforating gun, selective firing
2042None
2043None
2044--
2045bioconcentration
20461.n. [Drilling Fluids]
2047The concentration of a particular substance in a living organism, possibly with harmful effects. The likelihood of this occurring is expressed as the bioaccumulation potential and can be estimated by the octanol/water partition coefficient, expressed as logPOW. This test is commonly required on drilling fluid additives in the North Sea area and other countries following the Oslo and Paris Commission (OSPAR) regulations. Values of logPOW below 3 indicate no bioaccumulation tendency; values between 3 and 6 indicate that bioaccumulation is possible, providing the substance is small enough to pass through the cell wall (mol. wt. < 600). This may be confirmed by a bioconcentration test in which a population of animals is exposed to the product.
2048OSPAR
2049bioaccumulation
2050None
2051--
2052borehole compensation
20531.n. [Formation Evaluation]
2054An upgoing and downgoing arrangement of transducers in a logging tool, largely to offset spurious changes in reading caused by variations in borehole size or sonde tilt. The technique is used for measurements that rely on the propagation of a wave, such as sonic, propagation resistivity and electromagnetic propagation measurement.Propagation logs rely on measuring the difference in properties of a wave at two receivers. The borehole influences this difference if the tool is tilted or if there is a cave opposite one of the receivers. The effect can be compensated for by using two transmitters that radiate sequentially in opposite directions. In ideal conditions, the effect of a tilt or a cave is exactly opposite for the two transmitters, so that an average gives the correct result. Borehole compensation is different from borehole correction.
2055attenuation resistivity, dielectric resistivity, logging tool, phase-shift resistivity, propagation resistivity measurement
2056None
2057None
2058--
2059bullhead
20601.vb. [Drilling]
2061To forcibly pump fluids into a formation, usually formation fluids that have entered the wellbore during a well control event. Though bullheading is intrinsically risky, it is performed if the formation fluids are suspected to contain hydrogen sulfide gas to prevent the toxic gas from reaching the surface. Bullheading is also performed if normal circulation cannot occur, such as after a borehole collapse. The primary risk in bullheading is that the drilling crew has no control over where the fluid goes and the fluid being pumped downhole usually enters the weakest formation. In addition, if only shallow casing is cemented in the well, the bullheading operation can cause wellbore fluids to broach around the casing shoe and reach the surface. This broaching to the surface has the effect of fluidizing and destabilizing the soil (or the subsea floor), and can lead to the formation of a crater and loss of equipment and life.
2062casing shoe, formation fluid, lost circulation
2063None
2064None
2065--
2066barefoot completion
20671.n. [Well Completions]
2068A well completion that has no casing or liner set across the reservoir formation, allowing the produced fluids to flow directly into the wellbore. This type of completion suffers the major disadvantage that the sandface is unsupported and may collapse. Also, without any casing or liner installed, selective treatments or remedial work within the reservoir section are more difficult.
2069None
2070openhole completion
2071None
2072--
2073biodegradation
20741.n. [Drilling Fluids]
2075The process by which complex molecules are broken down by micro-organisms to produce simpler compounds. Biodegradation can be either aerobic (with oxygen) or anaerobic (without oxygen). The potential for biodegradation is commonly measured on drilling-fluid products to ensure that they do not persist in the environment. A variety of tests exist to assess biodegradation.
2076None
2077None
2078None
2079--
2080biodegradation
20812.n. [Heavy Oil]
2082The breakdown of medium-weight crude oil by microbial organisms into heavy and light components. When the light components, typically methane, escape to the surface, the heavy ends are left behind. Biodegradation gradually raises oil viscosity, reduces API gravity, increases asphaltene content and increases concentration of certain metals and sulfur.
2083None
2084None
2085None
2086--
2087borehole correction
20881.n. [Formation Evaluation]
2089The amount by which a log measurement must be adjusted in order to remove the contribution of the borehole. Although most log measurements are designed to pick up a minimum of signal from the borehole, some contribution usually remains. This contribution may be removed by software or by manual entry into correction charts. In resistivity logging, the correction replaces the borehole with a resistivity equal to that of the formation. In nuclear logging, the correction adjusts the reading to that which would be found in a standard condition, such as an 8-in. [20-cm] borehole filled with fresh water.
2090borehole compensation, cave effect, standoff
2091None
2092None
2093--
2094buoyancy
20951.n. [Well Completions]
2096The upward force acting on an object placed in a fluid. The buoyancy force is equal to the weight of fluid displaced by the object. Buoyancy can have significant effects over a wide range of completion and workover activities, especially in cases in which the wellbore and tubing string contain liquid and gas. Any change in the relative volumes or fluid levels will change the buoyancy forces.
2097None
2098None
2099None
2100--
2101barite
21021.n. [Geology]
2103[BaSO4]A dense sulfate mineral that can occur in a variety of rocks, including limestone and sandstone, with a range of accessory minerals, such as quartz, chert, dolomite, calcite, siderite and metal sulfides. Barite is commonly used to add weight to drilling fluid. Barite is of significance to petrophysicists because excess barite can require a correction factor in some well log measurements.
2104None
2105None
2106baryte
2107--
2108barite
21092.n. [Drilling Fluids]
2110A dense mineral comprising barium sulfate [BaSO4]. Commonly used as a weighting agent for all types of drilling fluids, barites are mined in many areas worldwide and shipped as ore to grinding plants in strategic locations, where API specifies grinding to a particle size of 3 to74 microns. Pure barium sulfate has a specific gravity of 4.50 g/cm3, but drilling-grade barite is expected to have a specific gravity of at least 4.20 g/cm3 to meet API specifications. Contaminants in barite, such as cement, siderite, pyrrhotite, gypsum and anhydrite, can cause problems in certain mud systems and should be evaluated in any quality assurance program for drilling-mud additives.
2111abrasion test, attapulgite, caustic extraction test, conventional mud, greasing out, gunning the pits, heavy metal, high-gravity solids, jar test, kill-weight fluid, pilot test, settling pit, slug, unweighted mud, water, oil and solids test, weighted mud, weighting material
2112None
2113None
2114--
2115biot theory
21161.n. [Formation Evaluation]
2117A theory for acoustic propagation in a porous and elastic medium developed by M.A. Biot. Compressional and shear velocities can be calculated by standard elastic theory from the composite density, shear and bulk modulus of the total rock. The problem is how to determine these from the properties of the constituent parts. Biot showed that the composite properties could be determined from the porosity and the elastic properties (density and moduli) of the fluid, the solid material, and the empty rock skeleton, or framework. To account for different frequencies of propagation, it is also necessary to know the frequency, the permeability of the rock, the viscosity of the fluid and a coefficient for the inertial drag between skeleton and fluid.Unlike the Gassmann model, the Biot theory takes into account frequency variations, and allows for relative motion between fluid and rock framework. As a result, it predicts some of the observed changes in velocity with frequency, as well as the critical frequency below which the Gassmann model is valid. It also predicts the existence of a so-called slow wave in addition to the shear wave and the compressional, or fast wave. The slow wave arises when the fluid and the skeleton move 1800 out-of-phase with each other. Its velocity is related to fluid mobility, but unfortunately has been observed only in the laboratory, not on logs. At logging frequencies, it degenerates into a diffusion phenomenon rather than a wave, and is apparently too highly attenuated to be observed in real rocks. However, in permeable formations, the Stoneley wave couples into the slow wave, causing the attenuation and dispersion that allow the measurement of Stoneley permeability.The full Biot theory is used mainly to analyze laboratory data. For practical log interpretation, it is more common to use the simpler Gassmann model.Reference:See Biot MA: Theory of Propagation of Elastic Waves in a Fluid-Saturated Porous Solid: I Low Frequency Range, Journal of the Acoustical Society of America 28, (1956):168-178. Biot MA: Theory of Propagation of Elastic Waves in a Fluid-Saturated Porous Solid: II Higher Frequency Range,Journal of the Acoustical Society of America 28, (1956): 179-191.
2118sonic log
2119None
2120None
2121--
2122borehole gravity
21231.adj. [Formation Evaluation]
2124Pertaining to the detection of the Earth's gravitational field within a wellbore. Subtle vertical variations of the Earth's gravity field may be detected over the length of a borehole. These depend on the variations in the formation density not only above and below the sensor, but also laterally away from the borehole. Thus, borehole gravity measurements may be used to detect the following phenomena:- overburden pressure- lateral formation density changes arising from porosity changes away from the borehole (fracture fields, vugs)- lateral proximity to lithology changes, such as major faulting or salt intrusions- time-lapse density measurements to monitor fluid saturation changes during the life of a reservoir.In borehole gravity measurements, highly accurate formation density measurements, averaged over a large volume, may be made by comparing changes of gravity between measurement stations.
2125borehole gravity meter
2126None
2127None
2128--
2129burn shoe
21301.n. [Well Workover and Intervention]
2131A downhole tool routinely used in fishing operations to prepare the top and outside surface of a fish, generally to allow an overshot or similar fishing tool to engage cleanly on the fish. In some cases, the outer portion of a fish may be milled out to allow the body and remaining debris to be pushed to the bottom of the wellbore.
2132None
2133mill shoe
2134None
2135--
2136barrel equivalent
21371.n. [Drilling Fluids]
2138A volume of 350 cm3. In mud laboratory experiments, 350 cm3 is the volume chosen to represent 42 US gallons (1 oilfield barrel) [0.159 m3], so that 1.0 gram mass represents 1.0 lbm. This is a convenient concept for mud technicians to use when mixing or pilot-testing mud samples. For example, in preparing a mud formulation or for pilot-testing purposes, adding 1.0 gram to 350 cm3 of fluid is the experimental equivalent of adding 1.0 lbm to 42 US gallons (1.0 bbl) of fluid.
2139lbm/bbl, mud cup, mud-aging cell, pilot test, rolling-aging test, static-aging test
2140None
2141None
2142--
2143bit
21441.n. [Drilling]
2145The tool used to crush or cut rock. Everything on a drilling rig directly or indirectly assists the bit in crushing or cutting the rock. The bit is on the bottom of the drillstring and must be changed when it becomes excessively dull or stops making progress. Most bits work by scraping or crushing the rock, or both, usually as part of a rotational motion. Some bits, known as hammer bits, pound the rock vertically in much the same fashion as a construction site air hammer.
2146antiwhirl bit, bit breaker, bottomhole assembly, drill collar, jet, make hole, PDC bit, roller-cone bit
2147None
2148None
2149--
2150borehole seismic data
21511.n. [Geophysics]
2152Seismic data measured with receivers, sources or both in a well, such as a check-shot survey, vertical seismic profile (VSP), crosswell seismic data or single-well imaging. By directly measuring the acoustic velocity of each formation encountered in a well, the well logs and borehole seismic data can be correlated to surface seismic data more easily. Borehole seismic data, including both S- and P-waves, can be gathered in a cased or openhole. This term is commonly used to distinguish between borehole sonic data (with frequencies typically greater than 1000 Hz) and borehole seismic data (with frequencies typically less than 1000 Hz).
2153hodogram, log, P-wave, quicklook, radial refraction, S-wave
2154None
2155None
2156--
2157butt weld
21581.n. [Well Workover and Intervention]
2159A 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.
2160bias weld
2161None
2162None
2163--
2164barrel pump
21651.n. [Well Workover and Intervention]
2166A small pump with an extended suction duct that is designed to pump fluid from barrels. Barrel pumps are commonly used to decant liquid additives during the preparation of treatment fluids at the wellsite.
2167treatment fluid
2168None
2169None
2170--
2171bit box
21721.n. [Drilling]
2173A container, usually made of steel and fitted with a sturdy lock, to store drill bits, especially higher cost PDC and diamond bits. These bits are extremely costly but often small in size, so they are prone to theft.
2174bit, diamond bit, PDC bit
2175None
2176None
2177--
2178borehole televiewer
21791.n. [Formation Evaluation]
2180An ultrasonic logging device with a radially mounted rotating transducer that is used to scan the borehole wall. The transducer (in transmit mode) emits a high-frequency pulse that is reflected by the borehole wall back to the transducer (in receive mode). In openhole applications, it can be used to measure the borehole diameter (by measuring the acoustic transit time between transducer and borehole wall) and the amplitude of acoustic signals reflected by the borehole wall. The transducer is rotated to produce a cross section of the borehole size and images of the borehole wall. These are used to identify fractures, breakouts and other borehole features. In cased hole, they are used to identify internal corrosion.
2181pulse-echo, ultrasonic measurement
2182None
2183None
2184--
2185butterfly chart
21861.n. [Formation Evaluation]
2187A plot representing the effect of invasion on resistivity measurements that have different depths of investigation. The plot assumes a step profile model of invasion and determines true resistivity, flushed zone resistivity and diameter of invasion from ratios of deep-, medium- and shallow-resistivity measurements. Strictly speaking, when both resistive and conductive invasion are plotted, the chart is called a butterfly chart. When only one is plotted it is known as a tornado chart.
2188conductive invasion, depth of investigation, resistive invasion
2189None
2190None
2191--
2192barrels of liquid per day
21931.n. [Production Testing]
2194A volume of fluid that refers to the daily total production of oil and water from a well. The volume of a barrel is equivalent to 42 US gallons, abbreviated BLPD.
2195None
2196None
2197BLPD
2198--
2199bit nozzle
22001.n. [Drilling]
2201The 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.
2202circulation system, crossflow, differential pressure, exit velocity, hydraulic horsepower, jet, jet velocity
2203None
2204jet nozzle
2205--
2206bottomhole choke
22071.n. [Well Completions]
2208A downhole device used to control fluid flow under downhole conditions. Downhole chokes are generally removable with slickline intervention and are located in a landing nipple in the tubing string.
2209choke, nipple
2210None
2211None
2212--
2213button resistivity
22141.n. [Formation Evaluation]
2215The resistivity measured by the buttons of a measurements-while-drilling (MWD) toroid device. Typically three buttons, each with a different depth of investigation, are mounted on a sleeve attached to the drillstring, and by their nature are azimuthally focused. The measurement is similar to a wireline microresistivity log, except that toroids are used instead of electrodes for transmitting and monitoring. The button resistivities are focused measurements with vertical resolutions and depths of investigation of a few inches. With three button measurements, it is possible to correct for the presence of invasion, assuming a step profile.
2216azimuth, bit resistivity, electrode resistivity, ring resistivity
2217None
2218None
2219--
2220barrels of oil per day
22211.n. [Production Testing]
2222A common unit of measurement for the daily volume of crude oil produced by a well or from a field. The volume of a barrel is equivalent to 42 US gallons, abbreviated BOPD.
2223None
2224None
2225BOPD
2226--
2227bit record
22281.n. [Drilling]
2229A historical record of how a bit performed in a particular wellbore. The bit record includes such data as the depth the bit was put into the well, the distance the bit drilled, the hours the bit was being used "on bottom" or "rotating", the mud type and weight, the nozzle sizes, the weight placed on the bit, the rotating speed and hydraulic flow information. The data are usually updated daily. When the bit is pulled at the end of its use, the condition of the bit and the reason it was pulled out of the hole are also recorded. Bit records are often shared among operators and bit companies and are one of many valuable sources of data from offset wells for well design engineers.
2230offset well
2231None
2232None
2233--
2234bottomhole circulating temperature
22351.n. [Drilling]
2236The temperature of the circulating fluid (air, mud, cement or water) at the bottom of the wellbore after several hours of circulation. This temperature is lower than the bottomhole static temperature. Therefore, in extremely harsh environments, a component or fluid that would not ordinarily be suitable under bottomhole static conditions may be used with great care in circulating conditions. Similarly, a high-temperature well may be cooled down in an attempt to allow logging tools to function. The BHCT is also important in the design of operations to cement casing because the setting time for cement is temperature-dependent. The BHCT and bottomhole static temperature (BHST) are important parameters when placing large volumes of temperature-sensitive treatment fluids.
2237cementing, circulate, logging tool, treatment fluid
2238None
2239BHCT
2240--
2241bottomhole circulating temperature
22422.n. [Drilling Fluids]
2243The temperature at the bottom of a well while fluid is being circulated, abbreviated BHCT. This is the temperature used for most tests of cement slurry in a liquid state (such as thickening time and fluid loss). In most cases, the BHCT is lower than the bottomhole static temperature (BHST), but in some cases, such as in deep water or in the arctic, the BHCT may be higher than the BHST.
2244None
2245None
2246BHCT
2247--
2248bwow
22491.adj. [Drilling Fluids]
2250Describing the amount (in percent) of a material added to a cement slurry based on the weight of water used to mix the slurry. Commonly abbreviated as BWOW, this convention normally is used only for salt [NaCl].
2251None
2252None
2253by weight of water
2254--
2255barrels of water per day
22561.n. [Production Testing]
2257A common unit of measurement for the volume of water produced each day by a well or in a field. The volume of a barrel is equivalent to 42 US gallons, abbreviated BWPD.
2258None
2259None
2260BWPD
2261--
2262bit resistivity
22631.n. [Formation Evaluation]
2264The resistivity measured at the drill bit by a measurements-while-drilling (MWD) tool. The bit resistivity measurement responds to resistivity changes as the bit penetrates the formation, or when the time after bit is zero. It is thus an early indication of formation change.The measurement is similar to a wireline electrode device except that toroids are used instead of electrodes. A transmitter toroid induces a low-frequency current in the drillstring, which flows out of the bit and returns farther up the string. The magnitude of the current depends on the resistivity near the bit, and is measured by another toroid. The vertical resolution and depth of investigation depend on the distances between the toroids and the bit, which, in turn, depend on the type of bottomhole assembly (BHA) used. The depth of investigation is sufficient that the effect of the borehole is normally small.The measurement is unfocused and usually not borehole-corrected. Since both bit and drillstring are in physical contact with the formation, it is possible to make the measurement in oil-base muds.
2265button resistivity, electrode device, geosteering, oil-base mud, ring resistivity
2266None
2267None
2268--
2269bottomhole gas separator
22701.n. [Production Testing]
2271A 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.
2272formation fluid, gas lock, rod pump, sucker rod
2273gas anchor
2274None
2275--
2276bwpd
22771.n. [Production Testing]
2278Abbreviation for barrels of water per day, a common unit of measurement for the daily volume of produced water. The volume of a barrel is equivalent to 42 US gallons.
2279None
2280None
2281barrels of water per day
2282--
2283base exchange
22841.n. [Formation Evaluation]
2285The quantity of positively charged ions (cations) that a clay mineral or similar material can accommodate on its negatively charged surface, expressed as milli-ion equivalent per 100 g, or more commonly as milliequivalent (meq) per 100 g. Clays are aluminosilicates in which some of the aluminum and silicon ions have been replaced by elements with different valence, or charge. For example, aluminum (Al+++) may be replaced by iron (Fe++) or magnesium (Mg++), leading to a net negative charge. This charge attracts cations when the clay is immersed in an electrolyte such as salty water and causes an electrical double layer. The cation-exchange capacity (CEC) is often expressed in terms of its contribution per unit pore volume, Qv.In formation evaluation, it is the contribution of cation-exchange sites to the formation electrical properties that is important. Various techniques are used to measure CEC in the laboratory, such as wet chemistry, multiple salinity and membrane potential. Wet chemistry methods, such as conductometric titration, usually involve destruction or alteration of the rock. Although quicker and simpler to perform, they are less representative of electrical properties in situ. The multiple salinity and membrane potential methods are more direct measurements of the effect of CEC on formation resistivity and spontaneous potential.
2286clay-bound water, dual water
2287None
2288Antonyms:cation-exchange capacity
2289--
2290base exchange
22912.n. [Drilling Fluids]
2292Quantity of positively charged ions (cations) that a clay mineral (or similar material) can accommodate on its negative charged surface, expressed as milliequivalents per 100 grams. CEC of solids in drilling muds is measured on a whole mud sample by a methylene blue capacity (MBC) test, which is typically performed to specifications established by API. CEC for a mud sample is reported as MBC, methylene blue test (MBT) or bentonite equivalent, lbm/bbl or kg/m3.
2293anion, cation, equivalent weight, ion exchange, methylene blue dye, mixed-metal hydroxide, montmorillonite, peptized clay, peptizing agent
2294None
2295None
2296--
2297bit trip
22981.n. [Drilling]
2299The process of pulling the drillstring out of the wellbore for the purpose of changing a worn or underperforming drill bit. Upon reaching the surface, the bit is usually inspected and graded on the basis of how worn the teeth are, whether it is still in gauge and whether its components are still intact. On drilling reports, this trip may be abbreviated as TFNB (trip for new bit).
2300bit record, tripping pipe
2301None
2302None
2303--
2304bottomhole heater
23051.n. [Production Facilities]
2306A device installed at the bottom of a well to increase the temperature of the fluid coming from the reservoir. Bottomhole heaters are used in low API gravity crude oils to reduce the fluid viscosity, thus reducing the high friction forces normally associated with these types of fluids
2307crude oil
2308None
2309None
2310--
2311by weight of water
23121.adj. [Drilling Fluids]
2313Describing the amount (in percent) of a material added to a cement slurry based on the weight of water used to mix the slurry. Commonly abbreviated as BWOW, this convention normally is used only for salt [NaCl].
2314None
2315None
2316BWOW
2317--
2318base map
23191.n. [Geology]
2320A map on which primary data and interpretations can be plotted. A base map typically includes locations of lease or concession boundaries, wells, seismic survey points and other cultural data such as buildings and roads, with a geographic reference such as latitude and longitude or Universal Transverse Mercator (UTM) grid information. Geologists use topographic maps as base maps for construction of surface geologic maps. Geophysicists typically use shot point maps, which show the orientations of seismic lines and the specific points at which seismic data were acquired, to display interpretations of seismic data. In the field, geologists can use a plane table and alidade to construct a base map.
2321alidade, Global Positioning System, plane table, topographic map, Universal Transverse Mercator grid (UTM)
2322None
2323None
2324--
2325bitumen
23261.n. [Geology]
2327Naturally-occurring, inflammable organic matter formed from kerogen in the process of petroleum generation that is soluble in carbon bisulfide. Bitumen includes hydrocarbons such as asphalt and mineral wax. Typically solid or nearly so, brown or black, bitumen has a distinctive petroliferous odor. Laboratory dissolution with organic solvents allows determination of the amount of bitumen in samples, an assessment of source rock richness.
2328asphalt, generation, geochemistry, hydrocarbon, kerogen, petroleum, petroleum system, source rock, tar sand
2329None
2330None
2331--
2332bitumen
23332.n. [Heavy Oil]
2334A designation for a hydrocarbon fluid with a gravity of 10° API or lower, based upon the classification of the US Department of Energy.
2335None
2336ultra heavy oil
2337None
2338--
2339bitumen
23403.n. [Shale Gas]
2341The fraction of naturally occurring, inflammable organic matter that is extractable from rock using organic solvents. Many petroleum precursors are composed of bitumen, but most are formed from kerogen in the process of petroleum generation. Bitumen includes hydrocarbons such as asphalt and mineral wax. Typically solid or nearly so, brown or black, bitumen has a distinctive petroliferous odor. Laboratory dissolution with organic solvents allows determination of the amount of bitumen in samples, an assessment of source rock richness. Burial and heating of kerogen yield bitumen, then liquid hydrocarbons, and then hydrocarbon gas. Understanding organic content is especially important in shale reservoirs because the shale is both the source rock and the reservoir rock in the petroleum system.
2342None
2343None
2344None
2345--
2346bottomhole injection pressure bhip
23471.n. [Well Completions]
2348The downhole pressure at which a treatment fluid can be injected into a zone of interest. The bottomhole injection pressure is typically calculated by adding the hydrostatic pressure of the fluid column to the surface pump pressure measured during an injection test.
2349None
2350None
2351None
2352--
2353bypass
23541.vb. [Drilling Fluids]
2355The act of passing the mud around a piece of equipment, such as passing mud returns around the shale shaker screens or going around a hydrocyclone device. From a mud-engineering viewpoint, this can be a bad practice because it can allow drill solids to degrade and accumulate as fines to the degree that they might cause mud problems.
2356drill solids, mud engineer
2357None
2358None
2359--
2360bypass
23612.n. [Production]
2362A system of pipes and valves permitting the diversion of flow or pressure around a line valve.
2363None
2364None
2365None
2366--
2367base of weathering
23681.n. [Geophysics]
2369The lower boundary of the near-surface, low-velocity zone in which rocks are physically, chemically or biologically broken down, in some cases coincident with a water table. Static corrections to seismic data can compensate for the low velocity of the weathered layer in comparison with the higher-velocity strata below.
2370first break, ghost, static correction, velocity, weathering
2371None
2372None
2373--
2374black list
23751.n. [Drilling Fluids]
2376List of products considered unsuitable by the Oslo and Paris Commission (OSPAR) for discharge, including mercury, cadmium and 'persistent oils and hydrocarbons of apetroleumorigin.' 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.The inclusion of hydrocarbons in the black list has been the driving force behind the reduction of oil discharges in the North Sea and elsewhere and has serious implications for the use of oil and synthetic fluids.
2377bioaccumulation, gray list, green list, HSE, OSPAR, PARCOM
2378None
2379None
2380--
2381bottomhole pressure
23821.n. [Drilling]
2383The pressure, usually measured in pounds per square inch (psi), at the bottom of the hole. This pressure may be calculated in a static, fluid-filled wellbore with the equation:BHP = MW * Depth * 0.052where BHP is the bottomhole pressure in pounds per square inch, MW is the mud weight in pounds per gallon, Depth is the true vertical depth in feet, and 0.052 is a conversion factor if these units of measure are used. For circulating wellbores, the BHP increases by the amount of fluid friction in the annulus. The BHP gradient should exceed the formation pressure gradient to avoid an influx of formation fluid into the wellbore.On the other hand, if BHP (including the added fluid friction pressure of a flowing fluid) is too high, a weak formation may fracture and cause a loss of wellbore fluids. The loss of fluid to one formation may be followed by the influx of fluid from another formation.
2384formation pressure
2385None
2386BHP
2387--
2388bottomhole pressure
23892.n. [Well Testing]
2390The pressure measured in a well at or near the depth of the producing formation. For well-test purposes, it is often desirable to refer the pressure to a datum level chosen at a reference depth by calculating the pressure that would occur if the pressure measurement were made at the datum level rather than at the actual depth of the gauge.
2391depth reference
2392None
2393BHP
2394--
2395bottomhole pressure
23963.n. [Well Completions]
2397The downhole pressure, measured or calculated at a point of interest, generally the top of the perforated interval.
2398None
2399None
2400BHP
2401--
2402c pump
24031.n. [Well Workover and Intervention]
2404A type of pump commonly used in the handling and mixing of oilfield fluids. The rotary motion of a profiled impeller in combination with a shaped pump housing or volute applies centrifugal force to discharge fluids from the pump. Centrifugal pumps generally operate most efficiently in high-volume, low-output-pressure conditions. Unlike a positive-displacement pump, the flow from centrifugal pumps can be controlled easily, even allowing flow to be completely closed off using valves on the pump discharge manifold while the pump is running. This pump isknown as a "centrifugal pump."
2405None
2406None
2407centrifugal pump
2408--
2409cdp
24101.n. [Geophysics]
2411In multichannel seismic acquisition where beds do not dip, the common reflection point at depth on a reflector, or the halfway point when a wave travels from a source to a reflector to a receiver. In the case of flat layers, the common depth point is vertically below the common midpoint. In the case of dipping beds, there is no common depth point shared by multiple sources and receivers, so dip moveout processing is necessary to reduce smearing, or inappropriate mixing, of the data.
2412None
2413None
2414common depth point
2415--
2416cloud point
24171.n. [Drilling Fluids]
2418The temperature at which a solution of a surfactant or glycol starts to form micelles (molecular agglomerates), thus becoming cloudy. This behavior is characteristic of nonionic surfactants, which are often soluble at low temperatures but "cloud out" at some point as the temperature is raised. Glycols demonstrating this behavior are known as "cloud-point glycols" and are used as shale inhibitors. The cloud point is affected by salinity, being generally lower in more saline fluids.
2419glycol, inhibitor, micelle, polyalkalene glycol, surfactant, thermally activated mud emulsion
2420None
2421None
2422--
2423cloud point
24242.n. [Heavy Oil]
2425The temperature at which wax crystals first start to form in a crude oil. Wax appearance temperature (WAT) and wax precipitation temperature (WPT) are other synonyms.
2426None
2427None
2428None
2429--
2430conformity
24311.n. [Geology]
2432A bedding surface separating younger from older strata, along which there is no evidence of subaerial or submarine erosion or of nondeposition, and along which there is no evidence of a significant hiatus. Unconformities (sequence boundaries) and flooding surfaces (parasequence boundaries) pass laterally into correlative conformities, or correlative surfaces.
2433flooding surface, unconformity
2434None
2435conformable
2436--
2437cable
24381.n. [Geophysics]
2439A bundle of electrical wires that connects geophones, or the entire carrier system for marine hydrophones, which includes the hydrophones, the electrical wires, the stress member, spacers, the outer skin of the cable, and the streamer filler, which is typically kerosene or a buoyant plastic. The cable relays data to the seismic recording truck or seismic vessel.
2440channel, eel, geophone, geophone cable, hydrophone, jug hustler, ocean-bottom cable, spacer, streamer
2441None
2442None
2443--
2444cable
24452.n. [Formation Evaluation]
2446The cable on which wireline logging tools are lowered into the well and through which signals from the measurements are passed. The cable consists of a central section with conductors surrounded by a metal, load-bearing armor.
2447bridle, head, logging tool, torpedo
2448None
2449None
2450--
2451cec
24521.n. [Drilling Fluids]
2453Quantity of positively charged ions (cations) that a clay mineral (or similar material) can accommodate on its negative charged surface, expressed as milliequivalents per 100 grams. CEC of solids in drilling muds is measured on a whole mud sample by a methylene blue capacity (MBC) test, which is typically performed to specifications established by API. CEC for a mud sample is reported as MBC, methylene blue test (MBT) or bentonite equivalent, lbm/bbl or kg/m3.
2454None
2455base exchange
2456cation-exchange capacity
2457--
2458cloud point glycol
24591.n. [Drilling Fluids]
2460A glycol that is soluble at low temperatures but starts to form micelles (molecular agglomerates), thus becoming cloudy, as the temperature is raised. The temperature at which this phenomenon occursthe cloud pointis affected by salinity, being generally lower in more saline fluids. Cloud point glycols are used as shale inhibitors. The purported mechanism is that the glycol clouds out at higher downhole temperatures,coatingthe surface of clays and preventinghydration.
2461cloud point, glycol, inhibitor, micelle, polyalkalene glycol, thermally activated mud emulsion
2462None
2463None
2464--
2465connection gas
24661.n. [Drilling]
2467A brief influx of gas that is introduced into the drilling fluid when a pipe connection is made. Before making a connection, the driller stops the mud pumps, thereby allowing gas to enter the wellbore at depth. Gas may also be drawn into the wellbore by minor swabbing effects resulting from short movements of the drillstring that occur during the connection. Connection gas usually occurs after one lag interval following the connection. On a mud log, it will appear as a short peak above background levels. This peak often appears at 30-foot intervals, depending on the lengths of drillpipe being connected as the well is drilled.
2468equivalent circulating density, trip gas
2469None
2470None
2471--
2472cable head
24731.n. [Drilling]
2474An electromechanical device used to connect an electrical tool string to a logging cable, electrical wireline or coiled tubing string equipped with an electrical conductor. It provides attachments to both the mechanical armor wires (which give logging cable its tensile strength) and the outer mechanical housing of a logging tool, usually by means of threads. This connection to the logging tool results in a good electrical path from the electrical conductors of the logging cable to the electrical contacts of the logging tool, and shields this electrical path from contact with conductive fluids, such as certain drilling muds. The basic requirements of most cable heads include providing reliable electrical and mechanical connectivity between the running string and tool string. Another attribute of cable heads is that they serve as a "weak link," so that if a logging tool becomes irretrievably stuck in a well, the operator may intentionally pull in excess of the breaking strength of the logging cable head, causing the cable to pull out of the cable head in a controlled fashion.
2475None
2476None
2477None
2478--
2479cellar
24801.n. [Drilling]
2481A dug-out area, possibly lined with wood, cement or very large diameter (6 ft [1.8 m]) thin-wall pipe, located below the rig. The cellar serves as a cavity in which the casing spool and casinghead reside. The depth of the cellar is such that the master valve of the Christmas tree are easy to reach from ground level. On smaller rigs, the cellar also serves as the place where the lower part of the BOP stack resides, which reduces the rig height necessary to clear the BOP stack on the top. Prior to setting surface casing, the cellar also takes mud returns from the well, which are pumped back to the surface mud equipment.
2482None
2483None
2484None
2485--
2486cluster
24871.n. [Reservoir Characterization]
2488A group of data points having similar characteristics. These points are usually found by cluster analysis, and are sometimes used to determine electrofacies from wireline data.
2489None
2490None
2491None
2492--
2493cluster
24942.vb. [Reservoir Characterization]
2495The act of determining clusters from data sets.
2496cluster analysis
2497None
2498None
2499--
2500constant composition expansion
25011.n. [Enhanced Oil Recovery]
2502A laboratory test usually performed as part of a routine PVT analysis that measures the change in volume of a reservoir fluid as a function of pressure. This change is determined by measuring the total volume of a sample of reservoir fluid at various pressures above and below the saturation pressure. The pressure-dependent volumes are normalized to the volume of the sample at the saturation pressure.
2503PVT
2504None
2505None
2506--
2507cable tool drilling
25081.n. [Drilling]
2509A method of drilling whereby an impact tool or bit, suspended in the well from a steel cable, is dropped repeatedly on the bottom of the hole to crush the rock. The tool is usually fitted with some sort of cuttings basket to trap the cuttings along the side of the tool. After a few impacts on the bottom of the hole, the cable is reeled in and the cuttings basket emptied, or a bailer is used to remove cuttings from the well. The tool is reeled back to the bottom of the hole and the process repeated. Due to the increasing time required to retrieve and deploy the bit as the well is deepened, the cable-tool method is limited to shallow depths. Though largely obsolete, cable-tool operations are still used to drill holes for explosive charge placement (such as for acquisition of surface seismic data) and water wells.
2510rotary drilling
2511None
2512basket sub
2513--
2514cellulosic polymer
25151.n. [Drilling Fluids]
2516A drilling-fluid additive used primarily for fluid-loss control, manufactured by reacting natural cellulose with monochloroacetic acid and sodium hydroxide [NaOH] to form CMC sodium salt. Up to 20 wt % of CMC may be NaCl, a by-product of manufacture, but purified grades of CMC contain only small amounts of NaCl. To make CMC, OH groups on the glucose rings of cellulose are ether-linked to carboxymethyl (-OCH2-COO-) groups. (Note the negative charge.) Each glucose ring has three OH groups capable of reaction, degree-of-substitution = 3. Degree of substitution determines water solubility and negativity of the polymer, which influences a CMC's effectiveness as a mud additive. Drilling grade CMCs used in muds typically have degree-of-substitution around 0.80 to 0.96. Carboxymethylcellulose is commonly supplied either as low-viscosity ("CMC-Lo Vis") or high-viscosity ("CMC-Hi Vis") grades, both of which have API specifications. The viscosity depends largely on the molecular weight of the starting cellulose material.Reference:Hughes TL, Jones TG and Houwen OW: "The Chemical Characterization of CMC and Its Relationship to Drilling-Mud Rheology and Fluid Loss," SPE Drilling & Completion 8, no. 3 (September 1993): 157-164.
2517carboxymethyl starch, carboxymethyl hydroxyethylcellulose, carboxymethylcellulose, emulsion mud, gyp mud, hydroxyethylcellulose, lime mud, polyanionic cellulose, potassium mud, seawater mud
2518None
2519None
2520--
2521cluster analysis
25221.n. [Reservoir Characterization]
2523Mathematical techniques for summarizing large amounts of multidimensional data into groups. The two most popular techniques are: hierarchicalk-means.The hierarchical system calculates as many clusters as there are data points and displays their relative closeness by means of a dendogram. This system is preferred when there are few data points but the user wishes to see the dendogram to chose an appropriate number of clusters for analysis. Principal Component Analysis (PCA) is a form of hierarchical cluster analysis.The k-means system requires the user to choose the number of cluster to be determined. The computation scatters the centers of the clusters among the data and then moves them until they are "gravitationally bound" to the larger groups of data and no longer move. The points determined in this way represent the central points of the clusters. This technique is very fast and appropriate for very large data sets. It is most commonly used in electrofacies calculations.Cluster analysis is often used to provide electrofacies from wireline data where each curve is set to be a dimension.
2524cluster, k-means cluster analysis
2525None
2526None
2527--
2528contact
25291.n. [Geology]
2530The interface, also called fluid contact, that separates fluids of different densities in areservoir. 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.Productionof fluids often perturbs the fluid contacts in a reservoir.
2531condensate, gas-oil contact, gas-water contact, lithologic contact, oil-water contact, stratified flow, transition zone, wet gas
2532fluid contact
2533None
2534--
2535contact
25362.n. [Geology]
2537The surface, also called lithologic contact, that separatesrockbodies of different lithologies, orrock types. A contact can beconformableor unconformable depending upon the types of rock, their relative ages and their attitudes.
2538attitude, horizon, lithology, unconformity
2539lithologic contact
2540None
2541--
2542cake
25431.n. [Drilling Fluids, Formation Evaluation]
2544The 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.
2545deflocculated mud, drilling fluid, dynamic filtration, filter-cake quality, filter-cake thickness, filtrate, filtrate volume, openhole completion, relative filtrate volume, resin, static filtration
2546filter cake
2547None
2548--
2549cement
25501.n. [Geology]
2551The binding material in sedimentary rocks that precipitates between grains from pore fluids. Calcite and quartz are common cement-forming minerals.
2552authigenic, cased hole, cementation, chlorite, diagenesis, hardground, lithification, sandstone
2553None
2554None
2555--
2556cement
25572.n. [Drilling]
2558The material used to permanently seal annular spaces between casing and borehole walls. Cement is also used to seal formations to prevent loss of drilling fluid and for operations ranging from setting kick-off plugs to plug and abandonment. The most common type by far is API Oilwell Cement, known informally as Portland cement. Generally speaking, oilfield cement is thinner and exhibits far less strength than cement or concrete used for construction due to the requirement that it be highly pumpable in relatively narrow annulus over long distances. Various additives are used to control density, setting time, strength and flow properties. Additionally, special additives are often used to reduce the occurrence of annular gas flow. The cement slurry, commonly formed by mixing Portland cement, water and assorted dry and liquid additives, is pumped into place and allowed to solidify (typically for 12 to 24 hours) before additional drilling activity can resume. The cement usually must reach a strength of 5000 psi [34,474 KPa] before drilling or perforating. More advanced oilfield cements achieve higher set-cement compressive strengths by blending a variety of particle types and sizes with less water than conventional mixtures of Portland cement, water and chemical additives.
2559free water, kick, neat cement, plug and abandon, wait on cement
2560None
2561None
2562--
2563cement
25643.n. [Well Completions]
2565A generic term used to describe Portland cement used in oil- and gas-well applications. In its simplest form, cement powder is ground from kiln-fired limestone and clay. However, modern oilfield cements are precise blends of quality assured materials to achieve consistent and predictable performance. Cement sets as the water in the slurry reacts chemically with the active ingredients, the most significant of which is tricalcium silicate reacting to create calcium silicate hydrate. Cement additives are used to control the setting process of the cement slurry and enhance the performance of the set cement. The API has developed a classification system for oilwell cement specification and performance.
2566cement additive
2567None
2568None
2569--
2570cmc
25711.n. [Drilling Fluids]
2572A drilling-fluid additive used primarily for fluid-loss control, manufactured by reacting natural cellulose with monochloroacetic acid and sodium hydroxide [NaOH] to form CMC sodium salt. Up to 20 wt % of CMC may be NaCl, a by-product of manufacture, but purified grades of CMC contain only small amounts of NaCl. To make CMC, OH groups on the glucose rings of cellulose are ether-linked to carboxymethyl (-OCH2-COO-) groups. (Note the negative charge.) Each glucose ring has three OH groups capable of reaction, degree-of-substitution = 3. Degree of substitution determines water solubility and negativity of the polymer, which influences a CMC's effectiveness as a mud additive. Drilling grade CMCs used in muds typically have degree-of-substitution around 0.80 to 0.96. Carboxymethylcellulose is commonly supplied either as low-viscosity ("CMC-Lo Vis") or high-viscosity ("CMC-Hi Vis") grades, both of which have API specifications. The viscosity depends largely on the molecular weight of the starting cellulose material.Reference: Hughes TL, Jones TG and Houwen OW: "The Chemical Characterization of CMC and Its Relationship to Drilling-Mud Rheology and Fluid Loss," SPE Drilling & Completion 8, no. 3 (September 1993): 157-164.
2573carboxymethyl starch, carboxymethyl hydroxyethylcellulose, cellulosic polymer, emulsion mud, gyp mud, lime mud, polyanionic cellulose, potassium mud, seawater mud
2574None
2575carboxymethylcellulose
2576--
2577contact angle
25781.n. [Enhanced Oil Recovery]
2579The angle of intersection of the interface between two fluids at a solid surface. The angle is measured from the solid surface through the aqueous phase, or in an oil and gas test through the oil phase. The contact angle displays hysteresis based on direction of motion of the interface. Surface roughness affects the equilibrium contact angle, so measurements are typically made on smooth, flat surfaces.A contact-angle test uses carefully captured and preserved samples of reservoir oil to determine the wetting preference. A droplet of the crude oil is suspended between two parallel plates of quartz or calcite inside a simulated formation water bath at reservoir temperature and sometimes at reservoir pressure. By periodically displacing one of the plates sideways, a contact angle is determined at the side of the droplet where water is forcing the oil from the solid. A small angle indicates water-wetting preference, while a large angle indicates oil-wetting. Angles near 90 degrees are intermediate-wetting. Different minerals display different wetting preferences, although most are more likely to be water-wet.
2580imbibition, oil-wet, water-wet, wettability
2581None
2582None
2583--
2584cake thickness
25851.n. [Drilling Fluids]
2586A 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.
2587filter cake, filter medium, filter press, filtrate volume, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, static filtration
2588filter-cake thickness
2589None
2590--
2591cement accelerator
25921.n. [Well Completions]
2593A chemical additive mixed with cement slurry to reduce the time required for the set cement to develop sufficient compressive strength to enable drilling operations to continue. Accelerators are generally used in near-surface applications in which the temperature is relatively low.
2594None
2595None
2596None
2597--
2598cmc hi vis
25991.n. [Drilling Fluids]
2600A high viscosity grade of drilling-fluid additive used primarily forfluid-loss control, manufactured by reacting natural cellulose with monochloroaceticacidandsodium hydroxide[NaOH] to form CMC sodiumsalt. Up to 20 wt % of CMC may be NaCl, a by-product of manufacture, but purified grades of CMC contain only small amounts of NaCl. To make CMC, OH groups on the glucose rings of cellulose are ether-linked to carboxymethyl (-OCH2-COO-) groups. (Note the negative charge.) Each glucose ring has three OH groups capable of reaction, degree-of-substitution = 3. Degree of substitution determines watersolubilityand negativity of thepolymer, which influences a CMC's effectiveness as amud additive. Drilling grade CMCs used in muds typically have degree-of-substitution around 0.80 to 0.96. Carboxymethylcellulose is commonly supplied either as low-viscosity ("CMC-Lo Vis") or high-viscosity ("CMC-Hi Vis") grades, both of which haveAPIspecifications. The viscosity depends largely on the molecular weight of the starting cellulose material.Reference: Hughes TL, Jones TG and Houwen OW: "The Chemical Characterization of CMC and Its Relationship to Drilling-Mud Rheology and Fluid Loss,"SPE Drilling & Completion8, no. 3 (September 1993): 157-164.
2601carboxymethyl starch, carboxymethylcellulose, cellulosic polymer, CMC, emulsion mud
2602CMC-HVT
2603None
2604--
2605contact time
26061.n. [Drilling Fluids]
2607The elapsed time required for a specific fluid to pass a designated depth or point in the annulus during pumping operations. Contact time is normally used as a design criterion for mud removal in turbulent flow.
2608None
2609None
2610None
2611--
2612calcite
26131.n. [Geology]
2614[CaCO3]The crystalline form of calcium carbonate and chief constituent of limestone and chalk. Calcite reacts readily with dilute hydrochloric acid [HCl], so the presence of calcite can be tested by simply placing a drop of acid on a rock specimen.
2615caliche
2616None
2617None
2618--
2619cement bond log
26201.n. [Drilling]
2621A representation of the integrity of the cement job, especially whether the cement is adhering solidly to the outside of the casing. The log is typically obtained from one of a variety of sonic-type tools. The newer versions, called cement evaluation logs, along with their processing software, can give detailed, 360-degree representations of the integrity of the cement job, whereas older versions may display a single line representing the integrated integrity around the casing.
2622None
2623None
2624cement evaluation log
2625--
2626cement bond log
26272.n. [Formation Evaluation]
2628A log that uses the variations in amplitude of an acoustic signaltraveling down the casing wall between a transmitter and receiver to determine the quality of cement bond on the exterior casing wall. The fundamental principle is that the acoustic signal will be more attenuated in the presence of cement than if the casing were uncemented. The measurement is largely qualitative, as there is no indication of azimuthal cement variations such as channeling, and as it is sensitive to the effect of a microannulus.
2629pulse-echo
2630None
2631None
2632--
2633cmc hvt
26341.n. [Drilling Fluids]
2635A high viscosity grade of drilling-fluid additive used primarily forfluid-loss control, manufactured by reacting natural cellulose with monochloroaceticacidandsodium hydroxide[NaOH] to form CMC sodiumsalt. Up to 20 wt % of CMC may be NaCl, a by-product of manufacture, but purified grades of CMC contain only small amounts of NaCl. To make CMC, OH groups on the glucose rings of cellulose are ether-linked to carboxymethyl (-OCH2-COO-) groups. (Note the negative charge.) Each glucose ring has three OH groups capable of reaction, degree-of-substitution = 3. Degree of substitution determines watersolubilityand negativity of thepolymer, which influences a CMC's effectiveness as amud additive. Drilling grade CMCs used in muds typically have degree-of-substitution around 0.80 to 0.96. Carboxymethylcellulose is commonly supplied either as low-viscosity ("CMC-Lo Vis") or high-viscosity ("CMC-Hi Vis") grades, both of which haveAPIspecifications. The viscosity depends largely on the molecular weight of the starting cellulose material.Reference: Hughes TL, Jones TG and Houwen OW: "The Chemical Characterization of CMC and Its Relationship to Drilling-Mud Rheology and Fluid Loss,"SPE Drilling & Completion8, no. 3 (September 1993): 157-164.
2636carboxymethyl starch, carboxymethyl hydroxyethylcellulose, carboxymethylcellulose, cellulosic polymer, polyanionic cellulose
2637CMC, CMC-Hi Vis
2638None
2639--
2640contaminant
26411.n. [Well Workover and Intervention]
2642A chemical or fluid that alters the performance of an engineered slurry or treatment fluid. Some remedial cementing treatments require unpredictable volumes of cement slurry to achieve the desired results. When excess slurry is left in the wellbore, it may not be possible to remove the excess slurry by conventional means, such as reverse circulation, before the slurry thickens and becomes immovable. Mixing the contaminant with the slurry in the correct proportions increases the thickening time of the slurry, allowing it to be safely removed from the wellbore.
2643squeeze cementing
2644None
2645None
2646--
2647calcium carbonate
26481.n. [Drilling Fluids]
2649A compound with formula CaCO3 that occurs naturally as limestone. Ground and sized calcium carbonate is used to increase mud density to about 12 lbm/gal [1.44 kg/m3], and is preferable to barite because it is acid-soluble and can be dissolved with hydrochloric acid to clean up production zones. Its primary use today is as a bridging material in drill-in, completion and workover fluids. Sized calcium carbonate particles, along with polymers, control fluid loss in brines or drill-in, completion and workover fluids. Insoluble calcium carbonate is the precipitated byproduct of mud treatments used for removal of either Ca+2 or CO3-2 by addition of the other ion.
2650alkalinity, bicarbonate, carbonate ion, carboxymethylcellulose, completion fluid, drill-in fluid, Garrett Gas Train, hardness ion, hydroxyethylcellulose, polyanionic cellulose, polymer, sized calcium carbonate, weighting material, workover fluid
2651None
2652None
2653--
2654cement evaluation log
26551.n. [Drilling]
2656A representation of the integrity of thecementjob, especially whether the cement is adhering solidly to the outside of thecasing. The log is typically obtained from one of a variety ofsonic-type tools. The newer versions, called cement evaluation logs, along with their processing software, can give detailed, 360-degree representations of the integrity of the cement job, whereas older versions may display a single line representing the integrated integrity around the casing.
2657cement bond log
2658None
2659None
2660--
2661cmc lo vis
26621.n. [Drilling Fluids]
2663A low viscosity grade of drilling-fluid additive used primarily forfluid-loss control, manufactured by reacting natural cellulose with monochloroaceticacidandsodium hydroxide[NaOH] to form CMC sodiumsalt. Up to 20 wt % of CMC may be NaCl, a by-product of manufacture, but purified grades of CMC contain only small amounts of NaCl. To make CMC, OH groups on the glucose rings of cellulose are ether-linked to carboxymethyl (-OCH2-COO-) groups. (Note the negative charge.) Each glucose ring has three OH groups capable of reaction, degree-of-substitution = 3. Degree of substitution determines watersolubilityand negativity of thepolymer, which influences a CMC's effectiveness as amud additive. Drilling grade CMCs used in muds typically have degree-of-substitution around 0.80 to 0.96. Carboxymethylcellulose is commonly supplied either as low-viscosity (""CMC-Lo Vis"") or high-viscosity (""CMC-Hi Vis"") grades, both of which haveAPIspecifications. The viscosity depends largely on the molecular weight of the starting cellulose material.Reference: Hughes TL, Jones TG and Houwen OW: ""The Chemical Characterization of CMC and Its Relationship to Drilling-Mud Rheology and Fluid Loss,""SPE Drilling & Completion8, no. 3 (September 1993): 157-164.
2664carboxymethyl starch, carboxymethyl hydroxyethylcellulose, carboxymethylcellulose, cellulosic polymer, emulsion mud, hydroxyethylcellulose, polyanionic cellulose
2665CMC, CMC-LVT
2666None
2667--
2668contamination gas
26691.n. [Drilling]
2670Gas that is introduced into the drilling mud from a source other than the formation. Contamination gas normally evolves as a by-product of oil-base mud systems and those using volatile additives such as diesel fuel or other lubricants.
2671oil-base mud
2672None
2673None
2674--
2675calcium carbonate plug
26761.n. [Well Completions]
2677A temporary plug formulated with graded granules or flakes of calcium carbonate that are generally circulated into place as a slurry and allowed to settle out. Calcium carbonate plugs commonly are used to isolate lower production zones, either to enable a column of well control fluid to be placed, or to provide some protection for a lower zone while treating upper zones. Because of their high reaction rate with hydrochloric acid, calcium carbonate plugs are easily removed using common acidizing materials and equipment.
2678None
2679None
2680None
2681--
2682cement extender
26831.n. [Well Completions]
2684A chemical additive or inert material used to decrease the density or increase the yield of a cement slurry. The slurry yield is typically expressed in cubic feet of slurry per sack of cement. Increasing the yield reduces the cost per volume of cement slurry, while reducing the slurry density reduces the hydrostatic pressure of the cement column, enabling weak zones to be successfully cemented and isolated.
2685None
2686None
2687None
2688--
2689cmc lvt
26901.n. [Drilling Fluids]
2691A low viscosity grade of drilling-fluid additive used primarily forfluid-loss control, manufactured by reacting natural cellulose with monochloroaceticacidandsodium hydroxide[NaOH] to form CMC sodiumsalt. Up to 20 wt % of CMC may be NaCl, a by-product of manufacture, but purified grades of CMC contain only small amounts of NaCl. To make CMC, OH groups on the glucose rings of cellulose are ether-linked to carboxymethyl (-OCH2-COO-) groups. (Note the negative charge.) Each glucose ring has three OH groups capable of reaction, degree-of-substitution = 3. Degree of substitution determines watersolubilityand negativity of thepolymer, which influences a CMC's effectiveness as amud additive. Drilling grade CMCs used in muds typically have degree-of-substitution around 0.80 to 0.96. Carboxymethylcellulose is commonly supplied either as low-viscosity (""CMC-Lo Vis"") or high-viscosity (""CMC-Hi Vis"") grades, both of which haveAPIspecifications. The viscosity depends largely on the molecular weight of the starting cellulose material.Reference: Hughes TL, Jones TG and Houwen OW: ""The Chemical Characterization of CMC and Its Relationship to Drilling-Mud Rheology and Fluid Loss,""SPE Drilling & Completion8, no. 3 (September 1993): 157-164.
2692carboxymethyl starch, carboxymethyl hydroxyethylcellulose, carboxymethylcellulose, cellulosic polymer, CMC, emulsion mud, hydroxyethylcellulose, polyanionic cellulose
2693CMC-Lo Vis
2694None
2695--
2696continuous reservoir
26971.n. [Shale Gas]
2698A type of areally extensive reservoir that contains hydrocarbon throughout, rather than containing a water contact or being significantly affected by a water column or a defined structural closure. The areal extent of a continuous reservoir, such as a shale reservoir, can be as large as the extent of the sedimentary basin in which the shale was deposited.
2699None
2700None
2701None
2702--
2703calcium contamination
27041.n. [Drilling Fluids]
2705A contamination problem caused by Ca+2 ions, usually occurring in fresh water, seawater and other low-salinity and low-hardness mud systems. Soluble calcium comes into a mud from various sources: gypsum- or anhydrite-bearing strata, unset cement and hardness ions in make-up water or from an influx of formation water. Ca+2 can flocculate colloidal clays and precipitate large anionic polymers that contain carboxylate groups, such as an acrylate polymer. On the other hand, some mud types tolerate calcium, in which case calcium is not considered a contaminant.
2706anion, calcium mud, clay-water interaction, colloid, deflocculated mud, flocculation, formation water, gyp mud, hardness ion, lime mud, seawater mud
2707None
2708None
2709--
2710cement head
27111.n. [Drilling]
2712A device fitted to the top joint of a casing string to hold a cement plug before it is pumped down the casing during the cementing operation. In most operations, a bottom plug is launched before the spacer or cement slurry. The top plug is released from the cement head after the spacer fluid. Most cement heads can hold both the top and bottom plugs. A manifold incorporated into the cement head assembly allows connection of a fluid circulation line.
2713cement head
2714None
2715None
2716--
2717cmp
27181.n. [Geophysics]
2719In multichannel seismic acquisition, the point on the surface halfway between the source and receiver that is shared by numerous source-receiver pairs. Such redundancy among source-receiver pairs enhances the quality of seismic data when the data are stacked. The common midpoint is vertically above the common depth point, or common reflection point. Common midpoint is not the same as common depth point, but the terms are often incorrectly used as synonyms.
2720None
2721None
2722common midpoint
2723--
2724contour map
27251.n. [Geology]
2726A map displaying lines that include points of equal value and separate points of higher value from points of lower value. Common types of contour maps include topographic contour maps, which show the elevation of the Earth's surface; structure contour maps, which show the elevation or depth of a formation; and gross or net sand or pay maps, which show variations in the thickness of a stratigraphic unit, also called isopachs.
2727contour, isochore, isochron map, isopach, spill point, structure map, topographic map
2728None
2729None
2730--
2731calcium hydroxide
27321.n. [Drilling Fluids]
2733A chemical with formula Ca(OH)2, commonly called slaked lime. Lime is used in lime muds and as a treatment to remove carbonate ions. It is used as a stabilizing ingredient in oil- and synthetic-base mud, essential to formation of fatty-acid soap emulsifiers. It is an alkaline material that can be carried in excess to neutralize hydrogen sulfide [H2S] and carbon dioxide [CO2].
2734alkalinity, calcium mud, calcium oxide, carbonate ion, equivalent weight, lime mud, low-colloid oil mud, oil-base mud
2735None
2736slaked lime
2737--
2738cement retainer
27391.n. [Well Completions]
2740An isolation tool set in the casing or liner that enables treatments to be applied to a lower interval while providing isolation from the annulus above. Cement retainers are typically used in cement squeeze or similar remedial treatments. A specially profiled probe, known as a stinger, is attached to the bottom of the tubing string to engage in the retainer during operation. When the stinger is removed, the valve assembly isolates the wellbore below the cement retainer.
2741None
2742None
2743None
2744--
2745co2 injection
27461.n. [Heavy Oil, Enhanced Oil Recovery]
2747An enhanced oil recovery method in which carbon dioxide (CO2) is injected into a reservoir to increase production by reducing oil viscosity and providing miscible or partially miscible displacement of the oil.
2748None
2749None
2750None
2751--
2752control line
27531.n. [Well Completions]
2754A small-diameter hydraulic line used to operate downhole completion equipment such as the surface controlled subsurface safety valve (SCSSV). Most systems operated by control line operate on a fail-safe basis. In this mode, the control line remains pressurized at all times. Any leak or failure results in loss of control line pressure, acting to close the safety valve and render the well safe.
2755surface-controlled subsurface safety valve (SCSSV)
2756None
2757None
2758--
2759calcium oxide
27601.n. [Drilling Fluids]
2761A 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.
2762calcium hydroxide, slaked lime
2763None
2764None
2765--
2766cementing plug
27671.n. [Drilling]
2768A rubber plug used to separate the cement slurry from other fluids, reducing contamination and maintaining predictable slurry performance. Two types of cementing plug are typically used on a cementing operation. The bottom plug is launched ahead of the cement slurry to minimize contamination by fluids inside the casing prior to cementing. A diaphragm in the plug body ruptures to allow the cement slurry to pass through after the plug reaches the landing collar. The top plug has a solid body that provides positive indication of contact with the landing collar and bottom plug through an increase in pump pressure.
2769None
2770wiper plug
2771None
2772--
2773coal
27741.n. [Geology]
2775A carbon-rich sedimentary rock that forms from the remains of plants deposited as peat in swampy environments. Burial and increase in temperature bring about physical and chemical changes called coalification. Because of the organic origin of coal, it cannot be classified as a mineral. The main types of coal, anthracite, bituminous coal and lignite, can be distinguished by their hardness and energy content, which are affected by their organic content as well as their conditions of formation. Natural gas associated with coal, called coal gas or coalbed methane, can be produced economically from coal beds in some areas. In some basins coals form source rocks.
2776hydrocarbon, source rock, swamp
2777None
2778None
2779--
2780convection
27811.n. [Geology]
2782The density- and heat-driven cycling, transfer or circulation of energy through which material initially warms up and becomes relatively less dense, then rises, cools and becomes relatively more dense, and finally sinks. As a consequence of convection, material can turn over repeatedly in a convection cell. Within the Earth, radiogenic heating results in convection appearing in the mantle and might drive plate tectonic motions. Convection also occurs in the ocean waters and in the Earth's atmosphere.
2783mantle, plate tectonics
2784None
2785None
2786--
2787calcium sulfate
27881.n. [Drilling Fluids]
2789The chemical CaSO4, which occurs naturally as the mineral anhydrite. Gypsum is the dihydrate mineral form, CaSO4·2H2O. Anhydrite and gypsum (commonly called gyp) are found in the subsurface and drilling even small stringers of these minerals can upset a freshwater or seawater mud. Gyp muds, lime muds and oil muds tolerate these salts best. CaSO4 is used as a mud treatment when no pH increase is needed to remove carbonate ion contamination in freshwater and seawater muds. (Lime increases pH when added for this purpose.) Gypsum and lime treatments are often used together to keep pH in the proper range. The test for determining the dissolved and undissolved calcium sulfate in a gyp mud requires two titrations with the strong EDTA reagent and Calver II® indicator when performed to API standards. It also requires a retort analysis for water content in the mud in order to calculate CaSO4 content, lbm/bbl.
2790calcium mud, calcium test, lime mud, oil mud, retort, scale, titration, water, oil and solids test
2791None
2792None
2793--
2794centralizer
27951.n. [Well Completions]
2796A device fitted with a hinged collar and bowsprings to keep the casing or liner in the center of the wellbore to help ensure efficient placement of a cement sheath around the casing string. If casing strings are cemented off-center, there is a high risk that a channel of drilling fluid or contaminated cement will be left where the casing contacts the formation, creating an imperfect seal.
2797bow-spring centralizer, cementing, deviated hole, eccentricity
2798None
2799None
2800--
2801centralizer
28022.n. [Well Completions]
2803A device used to keep a tool string in the center of the tubing, casing or wellbore. Tool centralization may be required for several reasons: to prevent the tool from hanging up on obstructions on the wellbore wall, to place fluid efficiently and to avoid excessive standoff.
2804None
2805None
2806None
2807--
2808centralizer
28093.n. [Formation Evaluation]
2810A device that helps to maintain the logging tool in the center of the borehole. On wireline tools such devices typically have three or more flexible bow springs. They may be mounted on the outside surface of the logging tool or else mounted in-line, between two cartridges or sondes. Some measurements, such as acoustic logs, respond better when the tool is centralized, while others, including induction logs, are better when eccentralized.
2811bow-spring centralizer, sonde
2812None
2813Antonyms:eccentralizer
2814--
2815coal bed methane
28161.n. [Geology]
2817Natural gas, predominantly methane [CH4], generated during coal formation and adsorbed in coal. Natural gas adsorbs to the surfaces of matrix pores within the coal and natural fractures, or cleats, as reservoir pressure increases.Production of natural gas from coal requires decreasing the pore pressure below the coal’s desorption pressure so that methane will desorb from surfaces, diffuse through the coal matrix and become free gas. Because the diffusivity and permeability of the coal matrix are ultralow, coal must have an extensive cleat system to ensure adequate permeability and flow of methane to wellbores at economic production rates.Coal seams are typically saturated with water. Consequently, the coal must be dewatered for efficient gas production. Dewatering reduces the hydrostatic pressure and promotes gas desorption from coal. As dewatering progresses, gas production often increases at a rate governed by how quickly gas desorbs from coal, the permeability of the cleat and the relative permeability of the gas-water system in the cleat. Eventually, the rate and amount of gas desorption decreases as the coal seam is depleted of its gas, and production declines.Coal seams with no water (dry coal) have been discovered and commercially exploited. In these reservoirs, the adsorbed gas is held in place by free gas in the cleats. Consequently, gas production consists of both free gas from the cleat system and desorbed gas from the matrix.
2818unconventional resource
2819coal seam gas, coal-seam gas, CSG
2820coalbed methane, coal-bed methane, CBM
2821--
2822conventional mud
28231.n. [Drilling Fluids]
2824A term that, in the past, referred to a mud containing bentonite clay, water, caustic soda and perhaps barite (as needed for density) usually with lignite or lignosulfonate present. Modern drilling does not necessarily recognize this as a conventional mud because polymer muds, special drill-in fluids and synthetic-base muds are now in common use. There may not be a "conventional mud" today.
2825chrome lignosulfonate, clay, deflocculant, drill-in fluid, low-solids mud, mud, synthetic-base mud
2826None
2827None
2828--
2829calibration
28301.n. [Geophysics]
2831A method of adjusting a data set against a control that has properties to which the data set should conform.
2832fan shooting
2833None
2834None
2835--
2836calibration
28372.n. [Formation Evaluation]
2838The process of adjusting a measurement to a standard, so that copies of the same type of logging tool or laboratory instrument will read the same. The tool or instrument is placed in the presence of a calibrator or calibrating environment, for example, a source of gamma rays for a gamma ray tool, or the air, far from the ground, for an induction tool. Calibration coefficients, typically a gain and an offset, are calculated so that the tool or instrument reads correctly in the calibrator. The coefficients are then applied during subsequent measurements.The term master calibration is used for the regular, as for example quarterly, calibration of a logging tool in the workshop. For most wireline tools, a secondary calibrator is adjusted during the master calibration and taken to the wellsite so that a wellsite calibration can be done just prior to the logging job. Some tools, such as the gamma ray, are calibrated only at the wellsite. For most measurements-while-drilling tools, the environment requires that the calibration be performed at the workshop and only a verification made at the wellsite.For some measurements, there is a primary worldwide standard against which calibrators are calibrated, as for example, the radioactive formations at the University of Houston used to define gamma ray API units.
2839None
2840None
2841None
2842--
2843centrifugal pump
28441.n. [Well Workover and Intervention]
2845A type of pump commonly used in the handling and mixing of oilfield fluids. The rotary motion of a profiled impeller in combination with a shaped pump housing or volute applies centrifugal force to discharge fluids from the pump. Centrifugal pumps generally operate most efficiently in high-volume, low-output-pressure conditions. Unlike a positive-displacement pump, the flow from centrifugal pumps can be controlled easily, even allowing flow to be completely closed off using valves on the pump discharge manifold while the pump is running. This pump is sometimes known as a "C pump."
2846pump manifold
2847None
2848C pump
2849--
2850coal seam gas
28511.n. [Geology]
2852Natural gas, predominantly methane [CH4], generated during coal formation and adsorbed in coal. Natural gas adsorbs to the surfaces of matrix pores within the coal and natural fractures, or cleats, as reservoir pressure increases.Production of natural gas from coal requires decreasing the pore pressure below the coal’s desorption pressure so that methane will desorb from surfaces, diffuse through the coal matrix and become free gas. Because the diffusivity and permeability of the coal matrix are ultralow, coal must have an extensive cleat system to ensure adequate permeability and flow of methane to wellbores at economic production rates.Coal seams are typically saturated with water. Consequently, the coal must be dewatered for efficient gas production. Dewatering reduces the hydrostatic pressure and promotes gas desorption from coal. As dewatering progresses, gas production often increases at a rate governed by how quickly gas desorbs from coal, the permeability of the cleat and the relative permeability of the gas-water system in the cleat. Eventually, the rate and amount of gas desorption decreases as the coal seam is depleted of its gas, and production declines.Coal seams with no water (dry coal) have been discovered and commercially exploited. In these reservoirs, the adsorbed gas is held in place by free gas in the cleats. Consequently, gas production consists of both free gas from the cleat system and desorbed gas from the matrix.
2853unconventional resource
2854coalbed methane, coal bed methane, coal-bed methane, CBM
2855coal-seam gas, CSG
2856--
2857conventional reservoir
28581.n. [Shale Gas, Geology]
2859A reservoir in which buoyant forces keep hydrocarbons in place below a sealing caprock. Reservoir and fluid characteristics of conventional reservoirs typically permit oil or natural gas to flow readily into wellbores. The term is used to make a distinction from shale and other unconventional reservoirs, in which gas might be distributed throughout the reservoir at the basin scale, and in which buoyant forces or the influence of a water column on the location of hydrocarbons within the reservoir are not significant.
2860None
2861None
2862None
2863--
2864caliche
28651.n. [Geology]
2866A crust of coarse sediments or weathered soil rich in calcium carbonate. It forms when lime-rich groundwater rises to the surface by capillary action and evaporates into a crumbly powder, forming a tough, indurated sheet called calcrete. Caliche typically occurs in desert or semi-arid areas. Of particular concern to geophysicists is the difficulty in acquiring good seismic data when shooting through a layer of caliche.
2867calcite, sediment
2868None
2869None
2870--
2871caliche
28722.n. [Geology]
2873A deposit of sodium nitrate that is mined and used for fertilizer in parts of South America.
2874None
2875None
2876None
2877--
2878centrifuge
28791.n. [Drilling Fluids]
2880An item of solids-removal equipment that removes fine and ultrafine solids. It consists of a conical drum that rotates at 2000 to 4000 rpm. Drilling fluid is fed into one end and the separated solids are moved up the bowl by a rotating scroll to exit at the other end. Centrifuges generally have limited processing capacity (50 to 250 gpm) but are useful for processing weighted drilling fluids and can remove finer solids than can a hydrocyclone or shaker screens. They can also be used for water clarification or for processing oily cuttings.
2881closed mud system, dewatering
2882None
2883None
2884--
2885centrifuge
28862.n. [Formation Evaluation]
2887A rapidly rotating flywheel on a vertical axle to whose rim is attached a series of tubes at one end, the other end being free to tilt upwards and outwards. At high speeds, the centrifugal force in the tubes is far greater than gravity. The centrifuge is used to expel fluids from core samples, either to clean them or to desaturate them for measurements of irreducible water saturation, resistivity index or nuclear magnetic resonance properties. It can be used at multiple speeds to obtain a capillary pressure curve. Centrifuges are also used in studies of clay mineralogy, where micron-scale fractions are extracted from suspension and subjected to analysis by X-ray diffraction (XRD).
2888distillation extraction, porous plate technique
2889None
2890None
2891--
2892coalbed methane
28931.n. [Geology]
2894Natural gas, predominantly methane [CH4], generated during coal formation and adsorbed in coal. Natural gas adsorbs to the surfaces of matrix pores within the coal and natural fractures, or cleats, as reservoir pressure increases.Production of natural gas from coal requires decreasing the pore pressure below the coal’s desorption pressure so that methane will desorb from surfaces, diffuse through the coal matrix and become free gas. Because the diffusivity and permeability of the coal matrix are ultralow, coal must have an extensive cleat system to ensure adequate permeability and flow of methane to wellbores at economic production rates.Coal seams are typically saturated with water. Consequently, the coal must be dewatered for efficient gas production. Dewatering reduces the hydrostatic pressure and promotes gas desorption from coal. As dewatering progresses, gas production often increases at a rate governed by how quickly gas desorbs from coal, the permeability of the cleat and the relative permeability of the gas-water system in the cleat. Eventually, the rate and amount of gas desorption decreases as the coal seam is depleted of its gas, and production declines.Coal seams with no water (dry coal) have been discovered and commercially exploited. In these reservoirs, the adsorbed gas is held in place by free gas in the cleats. Consequently, gas production consists of both free gas from the cleat system and desorbed gas from the matrix.
2895unconventional resource
2896coal seam gas, coal-seam gas, CSG
2897coal bed methane, coal-bed methane, CBM
2898--
2899convergence
29001.n. [Geology]
2901The movement of tectonic plates toward each other, generating compressional forces and ultimately resulting in collision, and in some cases subduction, of tectonic plates. The boundary where tectonic plates converge is called a convergent margin.
2902lithosphere, plate tectonics, transpression, turbidity current
2903None
2904None
2905--
2906convergence
29072.n. [Geophysics]
2908In mathematics, the process in which a sequence of numbers approaches a fixed value called the "limit" of the sequence. This term is often used in modeling or inversion to describe the situation in which a sequence of calculated values approach, or converge with, measured values.
2909model
2910None
2911Antonyms:divergence
2912--
2913caliper log
29141.n. [Drilling]
2915A representation of the measured diameter of a borehole along its depth. Caliper logs are usually measured mechanically, with only a few using sonic devices. The tools measure diameter at a specific chord across the well. Since wellbores are usually irregular (rugose), it is important to have a tool that measures diameter at several different locations simultaneously. Such a tool is called a multifinger caliper. Drilling engineers or rigsite personnel use caliper measurement as a qualitative indication of both the condition of the wellbore and the degree to which the mud system has maintained hole stability. Caliper data are integrated to determine the volume of the openhole, which is then used in planning cementing operations.
2916cementing, openhole
2917None
2918None
2919--
2920channeling
29211.n. [Formation Evaluation]
2922The condition in which cement flows in a channel only on some sides of the casing or borehole annulus, and thus does not provide adequate hydraulic isolation in all radial azimuths. The channel frequently manifests itself as an intermediate amplitude signal on a cement bond log. Pulse-echo tools are able to detect a channel because they measure the cement bond at different azimuths.
2923azimuth
2924None
2925None
2926--
2927coal bed methane
29281.n. [Geology]
2929Natural gas, predominantly methane [CH4], generated during coal formation and adsorbed in coal. Natural gas adsorbs to the surfaces of matrix pores within the coal and natural fractures, or cleats, as reservoir pressure increases.Production of natural gas from coal requires decreasing the pore pressure below the coal’s desorption pressure so that methane will desorb from surfaces, diffuse through the coal matrix and become free gas. Because the diffusivity and permeability of the coal matrix are ultralow, coal must have an extensive cleat system to ensure adequate permeability and flow of methane to wellbores at economic production rates.Coal seams are typically saturated with water. Consequently, the coal must be dewatered for efficient gas production. Dewatering reduces the hydrostatic pressure and promotes gas desorption from coal. As dewatering progresses, gas production often increases at a rate governed by how quickly gas desorbs from coal, the permeability of the cleat and the relative permeability of the gas-water system in the cleat. Eventually, the rate and amount of gas desorption decreases as the coal seam is depleted of its gas, and production declines.Coal seams with no water (dry coal) have been discovered and commercially exploited. In these reservoirs, the adsorbed gas is held in place by free gas in the cleats. Consequently, gas production consists of both free gas from the cleat system and desorbed gas from the matrix.
2930unconventional resource
2931coal seam gas, coal-seam gas, CSG
2932coalbed methane, coal bed methane, CBM
2933--
2934convergent
29351.adj. [Geology]
2936Pertaining to the movement of tectonic plates toward each other, generating compressional forces and ultimately resulting in collision, and in some cases subduction, of tectonic plates. The boundary where tectonic plates converge is called a convergent margin.
2937lithosphere, plate tectonics, transpression, turbidity current
2938None
2939None
2940--
2941convergent
29422.adj. [Geophysics]
2943In mathematics, pertaining to the process in which a sequence of numbers approaches a fixed value called the "limit" of the sequence. This term is often used inmodelingorinversionto describe the situation in which a sequence of calculated values approach, or converge with, measured values.
2944model
2945None
2946None
2947--
2948cap
29491.n. [Geophysics]
2950A small, electrically activated explosive charge that detonates a larger charge. Caps, also called seismic caps or blasting caps, are used for seismic acquisition with an explosive source to achieve consistent timing of detonation.
2951detonator
2952None
2953blasting cap
2954--
2955check shot survey
29561.n. [Geophysics]
2957A type of borehole seismic data designed to measure the seismic traveltime from the surface to a known depth. P-wave velocity of the formations encountered in a wellbore can be measured directly by lowering a geophone to each formation of interest, sending out a source of energy from the surface of the Earth, and recording the resultant signal. The data can then be correlated to surface seismic data by correcting the sonic log and generating a synthetic seismogram to confirm or modify seismic interpretations. It differs from a vertical seismic profile in the number and density of receiver depths recorded; geophone positions may be widely and irregularly located in the wellbore, whereas a vertical seismic profile usually has numerous geophones positioned at closely and regularly spaced intervals in the wellbore.
2958drift, first break, one-dimensional seismic data, one-way time
2959velocity survey
2960check-shot survey
2961--
2962coalesce
29631.vb. [Drilling Fluids]
2964To grow, as in the process of droplet growth, through small drops mergingwhen they come in contact. If this occurs repeatedly, a continuous liquid phase forms. Through this phenomenon, emulsions break and form two distinct liquid phases that tend to separate. Inoil-base mud, the water phase is dispersed as small droplets, with oil as the continuous (external) phase. A stableoil mudwill remain dispersed under normal drilling conditions because when droplets contact each other, they do not coalesce due to the strong emulsifierfilm around each droplet. However, when the emulsion film around each droplet becomes weakened, droplets will begin to coalesce. If not corrected, this can lead to total emulsion breakdown with solids becoming water-wetted.
2965creaming, emulsion, HLB number, water-wet
2966None
2967None
2968--
2969convolution
29701.n. [Geophysics]
2971A mathematical operation on two functions that is the most general representation of the process of linear (invariant) filtering. Convolution can be applied to any two functions of time or space (or other variables) to yield a third function, the output of the convolution. Although the mathematical definition is symmetric with respect to the two input functions, it is common in signal processing to say that one of the functions is a filter acting on the other function. The response of many physical systems can be represented mathematically by a convolution. For example, a convolution can be used to model the filtering of seismic energy by the various rock layers in the Earth; deconvolution is used extensively in seismic processing to counteract that filtering.The mathematical form of the convolution of two functions, a filter f(t) and a time-series x(t), isy(t) = ∫ f(t−τ)x(τ)dτ,where y(t) is the output of the convolution.In the frequency domain, convolution is simply the product of the Fourier transforms (FT) of the two functions:Y(ω) = F(ω)*X(ω),whereX(ω) = FT of the time series x(t)F(ω) = FT of the filter f(t)Y(ω) = FT of the output y(t)ω = angular frequency.
2972embedded wavelet, synthetic seismogram, wavelet
2973None
2974None
2975--
2976convolution
29772.n. [Well Testing]
2978A mathematical operation that uses downhole flow-rate measurements to transform bottomhole pressure measurements distorted by variable rates to an interpretable transient. Convolution also can use surface rates to transform wellhead pressures to an interpretable form. Convolution assumes a particular model for the pressure-transient response, usually infinite-acting radial flow. This operation is similar to what is done to account for the flow history in rigorous pressure-transient analysis.
2979transient-rate and pressure-test analysis
2980None
2981None
2982--
2983cap the well
29841.vb. [Well Completions]
2985To regain control of a blowout well by installing and closing a valve on the wellhead.
2986None
2987None
2988None
2989--
2990check valve
29911.n. [Well Completions]
2992A mechanical device that permits fluid to flow or pressure to act in one direction only. Check valves are used in a variety of oil and gas industry applications as control or safety devices. Check valve designs are tailored to specific fluid types and operating conditions. Some designs are less tolerant of debris, while others may obstruct the bore of the conduit or tubing in which the check valve is fitted.
2993cementing, flapper valve, float shoe, well control
2994None
2995None
2996--
2997check valve
29982.n. [Production]
2999A one-directional valve that is opened by the fluid flow in one direction and closes automatically when the flow stops or reverses direction.
3000None
3001None
3002None
3003--
3004coalescence
30051.n. [Drilling Fluids]
3006The process of droplet growth as small drops merge together when they come in contact. If this occurs repeatedly, a continuous liquid phase forms. Through this phenomenon, emulsions break and form two distinct liquid phases that tend to separate. In oil-base mud, the water phase is dispersed as small droplets, with oil as the continuous (external) phase. A stable oil mud will remain dispersed under normal drilling conditions because when droplets contact each other, they do not coalesce due to the strong emulsifier film around each droplet. However, when the emulsion film around each droplet becomes weakened, droplets will begin to coalesce. If not corrected, this can lead to total emulsion breakdown with solids becoming water-wetted.
3007creaming, emulsion, HLB number, water-wet
3008None
3009coalesce
3010--
3011convolve
30121.vb. [Geophysics]
3013To perform a convolution, which is a mathematical operation on two functions that is the most general representation of the process of linear (invariant) filtering. Convolution can be applied to any two functions of time or space (or other variables) to yield a third function, the output of the convolution. Although the mathematical definition is symmetric with respect to the two input functions, it is common in signal processing to say that one of the functions is a filter acting on the other function. The response of many physical systems can be represented mathematically by a convolution. For example, a convolution can be used to model the filtering of seismic energy by the various rock layers in the Earth; deconvolution is used extensively in seismic processing to counteract that filtering.
3014embedded wavelet, synthetic seismogram, wavelet
3015None
3016None
3017--
3018convolve
30192.vb. [Well Testing]
3020To perform a convolution, which is a mathematical operation that uses downhole flow-rate measurements to transform bottomhole pressure measurements distorted by variable rates to an interpretable transient. Convolution also can use surface rates to transform wellhead pressures to an interpretable form. Convolution assumes a particular model for the pressure-transient response, usually infinite-acting radial flow. This operation is similar to what is done to account for the flow history in rigorous pressure-transient analysis.
3021transient-rate and pressure-test analysis
3022None
3023None
3024--
3025capacitance log
30261.n. [Production Logging]
3027An in situ record of the capability of the fluid passing through a sensor to store electrical charge. Since water has a high dielectric constant, and hence capacitance, it can be distinguished from oil or gas. The capacitance, or fluid capacitance log, can therefore identify water and be scaled in terms of water holdup. However, the relation between capacitance and holdup depends strongly on whether the water is the continuous phase, complicating quantitative evaluation.The log was introduced in the 1960s with the so-called holdup meter. It was mainly used in three-phase flow, or when fluid-density measurements were insufficiently sensitive to water at low holdup, or with heavy oils. Since the late 1980s, other holdup measurements have been preferred.
3028fluid-density log, holdup log, multi-capacitance flowmeter, production log
3029None
3030None
3031--
3032check shot survey
30331.n. [Geophysics]
3034A type of borehole seismic data designed to measure the seismic traveltime from the surface to a known depth. P-wave velocity of the formations encountered in a wellbore can be measured directly by lowering a geophone to each formation of interest, sending out a source of energy from the surface of the Earth, and recording the resultant signal. The data can then be correlated to surface seismic data by correcting the sonic log and generating a synthetic seismogram to confirm or modify seismic interpretations. It differs from a vertical seismic profile in the number and density of receiver depths recorded; geophone positions may be widely and irregularly located in the wellbore, whereas a vertical seismic profile usually has numerous geophones positioned at closely and regularly spaced intervals in the wellbore.
3035correlate, correlation, depth conversion, drift, first break, interpretation, one-dimensional seismic data, one-way time
3036velocity survey, well shoot
3037None
3038--
3039coal seam gas
30401.n. [Geology]
3041Natural gas, predominantly methane [CH4], generated during coal formation and adsorbed in coal. Natural gas adsorbs to the surfaces of matrix pores within the coal and natural fractures, or cleats, as reservoir pressure increases.Production of natural gas from coal requires decreasing the pore pressure below the coal’s desorption pressure so that methane will desorb from surfaces, diffuse through the coal matrix and become free gas. Because the diffusivity and permeability of the coal matrix are ultralow, coal must have an extensive cleat system to ensure adequate permeability and flow of methane to wellbores at economic production rates.Coal seams are typically saturated with water. Consequently, the coal must be dewatered for efficient gas production. Dewatering reduces the hydrostatic pressure and promotes gas desorption from coal. As dewatering progresses, gas production often increases at a rate governed by how quickly gas desorbs from coal, the permeability of the cleat and the relative permeability of the gas-water system in the cleat. Eventually, the rate and amount of gas desorption decreases as the coal seam is depleted of its gas, and production declines.Coal seams with no water (dry coal) have been discovered and commercially exploited. In these reservoirs, the adsorbed gas is held in place by free gas in the cleats. Consequently, gas production consists of both free gas from the cleat system and desorbed gas from the matrix.
3042unconventional resource
3043coalbed methane, coal bed methane, coal-bed methane, CBM
3044coal seam gas, CSG
3045--
3046copper carbonate
30471.n. [Drilling Fluids]
3048A compound, CuCO3, that was used as a sulfide scavenger for water-base muds. However, it was found to be corrosive due to spontaneous plating of metallic copper onto metal surfaces, causing pitting corrosion; it has largely been replaced by zinc compounds.Reference:Perricone AC and Chesser BG: "Corrosive Aspects of Copper Carbonate in Drilling Fluids," Oil & Gas Journal 68, no. 37 (September 14, 1970): 82-85.
3049Garrett Gas Train, water-base mud, zinc basic carbonate, zinc carbonate
3050None
3051None
3052--
3053capacitance meter
30541.n. [Production Logging]
3055Another term for holdup meter, a device for determining the waterholdupin aproducing wellby measuring the capacitance or impedanceof the fluid. The holdupmeteris used to produce a capacitance log. Since water has a high dielectricconstant, and hence capacitance, it can be distinguished from oil or gas. The meter is a coaxial capacitor, with fluid flowing between a centralprobeand an external cage that act as electrodes. The meter has often been combined with apackerflowmeteror adiverterflowmeter, so that all the fluids in the wellpassthrough the meter.
3056dielectric constant, holdup log, production log
3057diverter flowmeter, holdup meter, water-cut meter
3058None
3059--
3060chemical barrel
30611.n. [Drilling Fluids]
3062A 20- to 50-gallon [3.2- to 7.9 m3] container for liquid mud additives, usually located above the suction pit on a drilling rig. The chemical barrel is used to slowly dispense various types of liquids into the active mud system. It has traditionally been used to add caustic (NaOH or KOH) solution at a slow and steady rate in order to maintain a uniform pH throughout a circulating mud system. Adding caustic solution is an especially risky operation and the proper design and use of the chemical barrel for safety is vitally important. Derrickmen must be informed of the dangers, proper protective clothing and safety rules to follow when using the chemical barrel.
3063caustic potash, caustic soda, defoamer, derrickman, suction pit
3064None
3065None
3066--
3067coating
30681.n. [Enhanced Oil Recovery]
3069Any thin material, liquid or powder, which, applied over a structure, forms a continuous film to protect against corrosion.Corrosion coatings should possess flexibility, resistance against impact and moisture, good adhesion and cohesion, and chemical resistance to the exposure conditions (such as temperature, hydrogen sulfide).Organic coatings such as polyethylenes (plastic) are normally used for external protection of pipelines while asphalt and coal tar enamels are used to protect buried pipes or undersides of oilfield tanks. Inorganic coating such as zinc-silicate is used to protect drilling and production platforms above the splash zone and nickel phosphate coating is used to protect packer body parts.
3070coating flaw
3071None
3072None
3073--
3074core
30751.vb. [Drilling]
3076To deepen the wellbore by way of collecting a cylindrical sample of rock. A core bit is used to accomplish this, in conjunction with a core barrel and core catcher. The bit is usually a drag bit fitted with either PDC or natural diamond cutting structures, but the core bit is unusual in that it has a hole in its center. This allows the bit to drill around a central cylinder of rock, which is taken in through the bit and into the core barrel. The core barrel itself may be thought of as a special storage chamber for holding the rock core. The core catcher serves to grip the bottom of the core and, as tension is applied to the drillstring, the rock under the core breaks away from the undrilled formation below it. The core catcher also retains the core so that it does not fall out the bottom of the drillstring, which is open in the middle at that point.
3077diamond bit, drag bit, PDC bit
3078None
3079None
3080--
3081core
30822.n. [Geology]
3083Innermost layer of the Earth. Studies of compressional and shear waves indicate that the core makes up nearly 3500 km [2170 miles] of the Earth's radius of 6370 km [3950 miles]. Such studies also demonstrate that because shear waves do not pass through the outer part of the core (2250 km [1400 miles] thick), it is liquid (only solids can shear). The inner core is solid and 1220 km [750 miles] thick. The core's iron and nickel composition was inferred through studies of the Earth's gravitational field and average density. The relatively low density of the outer layers of the Earth suggests a dense inner layer.
3084asthenosphere, crust, lithosphere, mantle, plate tectonics, S-wave
3085None
3086None
3087--
3088core
30893.n. [Formation Evaluation]
3090A cylindrical sample of geologic formation, usually reservoir rock, taken during or after drilling a well. Cores can be full-diameter cores (that is, they are nearly as large in diameter as the drill bit) taken at the time of drilling the zone, or sidewall cores (generally less than 1 in. [2.5 cm] in diameter) taken after a hole has been drilled. Cores samples are used for many studies, some of which relate to drilling fluids and damage done by them.
3091bland coring fluid, core, coring fluid, drill-in fluid, drilling fluid, dynamic filtration, filtrate, filtrate tracer, filtration
3092None
3093None
3094--
3095capacity factor
30961.n. [Production]
3097The number of gallons of water per minute that will flow through a valve with a pressure drop of 1 psi. Also expressed as Kv in m3/hr∙bar.
3098None
3099None
3100None
3101--
3102chemical cutter
31031.n. [Perforating]
3104A downhole tool run on wireline to sever tubing at a predetermined point when the tubing string becomes stuck. When activated, the chemical cutter use a small explosive charge to forcefully direct high-pressure jets of highly corrosive material in a circumferential pattern against the tubular wall. The nearly instantaneous massive corrosion of the surrounding tubing wall creates a relatively even cut with minimal distortion of the tubing, aiding subsequent fishing operations.
3105None
3106None
3107None
3108--
3109coating flaw
31101.n. [Enhanced Oil Recovery]
3111A void in the pipe coating. Coating flaws are detected by either mechanical or visual inspections and must be repaired to avoid significant corrosion problems.A coating flaw is also called a holiday.
3112None
3113None
3114None
3115--
3116core analysis
31171.n. [Formation Evaluation, Shale Gas]
3118Laboratory study of a sample of a geologic formation, usually reservoir rock, taken during or after drilling a well. Economic and efficient oil and gas production is highly dependent on understanding key properties of reservoir rock, such as porosity, permeability, and wettability. Geoscientists have developed a variety of approaches, including log and core analysis techniques, to measure these properties. Core analysis is especially important in shale reservoirs because of the vertical and lateral heterogeneity of the rocks. Core analysis can include evaluation of rock properties and anisotropy; organic matter content, maturity, and type; fluid content; fluid sensitivity; and geomechanical properties. This information can be used to calibrate log and seismic measurements and to help in well and completion design, well placement, and other aspects of reservoir production.
3119None
3120None
3121None
3122--
3123capillary number
31241.n. [Enhanced Oil Recovery]
3125A dimensionless group used in analysis of fluid flow that characterizes the ratio of viscous forces to surface or interfacial tension forces. It is usually denoted NC in the oil field and Ca in chemical engineering. For a flowing liquid, if NC >>1, then viscous forces dominate over interfacial forces; however if NC <<1, then viscous forces are negligible compared with interfacial forces. Capillary numbers are usually large for high-speed flows and low for low-speed flows; thus, typically for flow through pores in the reservoir NC is ~10−6, and for flow in production tubulars NC is ~1.Capillary number equation:NC = Ca = (μU) / σwhereNC = Ca = capillary numberμ = fluid viscosityU = fluid velocityσ = surface or interfacial tension.
3126interfacial tension
3127None
3128None
3129--
3130chemical flooding
31311.n. [Enhanced Oil Recovery, Enhanced Oil Recovery]
3132A general term for injection processes that use special chemical solutions. Micellar, alkaline and soap-like substances are used to reduce surface tension between oil and water in the reservoir, whereas polymers such as polyacrylamide or polysaccharide are employed to improve sweep efficiency. The chemical solutions are pumped through specially distributed injection wells to mobilize oil left behind after primary or secondary recovery. Chemical flooding is a major component of enhanced oil recovery processes and can be subdivided into micellar-polymer flooding and alkaline flooding.The general procedure of a chemical flooding includes a preflush (low-salinity water), a chemical solution (micellar or alkaline), a mobility buffer and, finally, a driving fluid (water), which displaces the chemicals and the resulting oil bank to production wells. The preflush and the mobility buffer are optional fluids.
3133micelle, miscible displacement, soap, surface tension, thermal recovery
3134None
3135None
3136--
3137cod
31381.n. [Drilling Fluids]
3139The amount of oxygen needed to oxidize reactive chemicals in a water system, typically determined by a standardized test procedure. COD is used to estimate the amount of a pollutant in an effluent. Compare to biochemical oxygen demand, BOD.
3140None
3141None
3142chemical oxygen demand
3143--
3144core plug
31451.n. [Formation Evaluation]
3146A plug, or sample, taken from a conventional core for analysis. Core plugs are typically 1 in. to 1 1/2 in. [2.5 to 3.8 cm] in diameter and 1 in. to 2 in. [5 cm] long. Core plugs are ordinarily cut perpendicular to the axis of the core or parallel to the axis, called horizontal and vertical plugs, respectively, when cut from a vertical wellbore. The terms horizontal and vertical are often applied for cores cut from a deviated or horizontal wellbore, even though they are not strictly correct unless core orientation is measured and plugs are cut to the true in-situ orientation.
3147routine core analysis, sidewall core, whole core
3148None
3149None
3150--
3151capillary pressure curve
31521.n. [Formation Evaluation]
3153The relationship describing the capillary pressure required to obtain a given nonwetting phase saturation in a rock. Rocks have a distribution of pore throat sizes, so as more pressure is applied to the nonwetting phase, increasingly smaller pore openings are invaded. The capillary pressure curve is important for understanding saturation distribution in the reservoir and affects imbibition and multiphase fluid flow through the rock.
3154wettability
3155None
3156None
3157--
3158chemical marker injection
31591.n. [Production Logging]
3160A technique in which a slug of material is introduced into the flowstream of a producing well to determine the flow rate of one or more of the fluids. The marker has specific properties, such as high neutron capture cross section, that allow it to be detected by sensors of a production logging tool. Some markers are specifically designed to be soluble in only one fluid phase, so that they can be used to produce a phase-velocity log. The term refers to nonradioactive markers, in contrast to the more traditional radioactive markers, or tracers.
3161production log, tracer, tracer measurement
3162None
3163None
3164--
3165cofcaw
31661.n. [Enhanced Oil Recovery]
3167Abbreviation for a combination of forward combustion and waterflooding, also called wet combustion or in situsteamgeneration. COFCAW is an in situcombustion technique in which water is injected simultaneously or alternately with air intoa formation. Wet combustion actually refers to wet forward combustion and was developed to use the great amount of heat that would otherwise be lost in the formation. The injected water recovers the heat from behind the burning front and transfers it to theoil bankahead. Because of this additional energy, the oil displacementis more efficient and requires less air. In spite of these advantages, a wet combustion process cannot avoid liquid-blocking problems and use of wet combustion is limited by the oilviscosity.
3168wet combustion
3169None
3170None
3171--
3172coreflooding
31731.n. [Enhanced Oil Recovery]
3174A laboratory test in which a fluid or combination of fluids is injected into a sample of rock. Objectives include measurement of permeability, relative permeability, saturation change, formation damage caused by the fluid injection, or interactions between the fluid and the rock. The core material often comes from an oil reservoir, but some tests use outcrop rock. The fluid in place at the start of the test is typically either a simulated formation brine, oil (either crude oil or refined oil), or a combination of brine and oil. Injected fluids may include crude oil, simulated reservoir brine, refined fluids, drilling mud filtrate, acids, foam or other chemicals used in the oil field. Depending on the purpose of the test, conditions may be either ambient temperature and low confining pressure or high temperature and pressure of a subject reservoir. Pressures and flow rates at both ends of the core are measured, and the core can also be investigated using other measurements such as nuclear magnetic resonance (NMR) during the test. A coreflood is typically used to determine the optimum development option for an oil reservoir and often helps evaluate the effect of injecting fluids specially designed to improve or enhance oil recovery.
3175None
3176None
3177None
3178--
3179carbide lag test
31801.n. [Drilling]
3181A test performed by the mudlogger or wellsite geologist, used to calculate sample lag. The lag period can be measured as a function of time or pump strokes. Acetylene is commonly used as a tracer gas for this purpose. This gas is generated by calcium carbide, a man-made product that reacts with water. Usually, a small paper packet containing calcium carbide is inserted into the drillstring when the kelly is unscrewed from the pipe to make a connection, and the time is noted, along with the pump-stroke count on the mud pump. Once the connection is made and drilling resumes, the packet is pumped downhole with the drilling fluid. Along the way, the drilling fluid breaks down the paper and reacts with the calcium carbide. The resulting acetylene gas circulates with the drilling fluid until it reaches the surface, where it is detected at the gas trap, causing a rapid increase or spike in gas readings. The time and pump-stroke count are again noted, and the cuttings sample lag interval is calculated.
3182cycle time, lag gas, lag time
3183None
3184None
3185--
3186chemical oxygen demand
31871.n. [Drilling Fluids]
3188The amount of oxygen needed to oxidize reactive chemicals in a water system, typically determined by a standardized test procedure. COD is used to estimate the amount of a pollutant in an effluent. Compare to biochemical oxygen demand, BOD.
3189None
3190None
3191COD
3192--
3193coherence
31941.n. [Geophysics]
3195A measure of the similarity of two seismic traces.
3196correlation, phantom, seismic trace, semblance
3197None
3198None
3199--
3200coherence
32012.n. [Geophysics]
3202The quality of two wave trains, or waves consisting of several cycles, being in phase.
3203wave
3204None
3205None
3206--
3207coherence
32083.n. [Geophysics]
3209The similarity of two mathematical functions as evaluated in the frequency domain.
3210correlation
3211None
3212None
3213--
3214coherence
32154.n. [Geophysics]
3216A quantitative assessment of the similarity of three or more functions, also called semblance.
3217None
3218None
3219None
3220--
3221coring fluid
32221.n. [Drilling Fluids]
3223A specially designed fluid that is used for cutting cores with a core barrel and core bit. Sometimes the fluid used is the drilling mud, but if cores are for special studies, the coring fluid must be carefully designed to avoid damaging or altering the rock sample, such as a bland coring fluid.
3224bland coring fluid, core, drilling mud, filtrate tracer
3225None
3226None
3227--
3228carbon dioxide
32291.n. [Drilling Fluids]
3230The compound with the formula CO2. An odorless gas, carbon dioxide [CO2] is widely distributed in nature and is a minor component of air. It is highly soluble in water and oil, especially under pressure. In water, it occurs as carbonic acid, a weak acid that can donate one or two hydrogen ions in neutralization reactions that produce bicarbonate [HCO3-] and carbonate [CO3-2] salts or ions. CO2, being an acid in water, reacts instantly with NaOH or KOH in an alkaline water mud, forming carbonate and bicarbonate ions. Similarly, it reacts with Ca(OH)2 (lime) to form insoluble calcium carbonate and water.
3231carbonate ion, carbonate test, Dräger tube, Garrett Gas Train, gypsum, lime mud, pH, sour gas
3232None
3233None
3234--
3235chemical potential
32361.n. [Enhanced Oil Recovery]
3237The change in the Gibbs free energy (G) of a system when an infinitesimally small amount of a component is added under constant pressure (P) and temperature (T) while keeping the mass of the other components of the system unchanged. Concentration variation within a system tends to drive a particle along a gradient from higher to lower chemical potential (μ). Chemical potential can also be defined in terms of Helmholtz free energy (A) under conditions of constant volume (V) and temperature.Chemical potential equation:μi = (∂G / ∂Ni)T, P, Nj ≠ i
3238None
3239None
3240None
3241--
3242coiled tubing
32431.n. [Drilling]
3244A 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.
3245coiled tubing drilling, packer
3246endless tubing, reeled tubing
3247CT
3248--
3249coiled tubing
32502.n. [Well Workover and Intervention]
3251A 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.
3252None
3253endless tubing, reeled tubing
3254CT
3255--
3256corrosion
32571.n. [Enhanced Oil Recovery]
3258The loss of metal due to chemical or electrochemical reactions, which could eventually destroy a structure.Corrosion can occur anywhere in the production system, either at bottomhole or in surface lines and equipment. The corrosion rate will vary with time depending on the particular conditions of the oil field, such as the amount of water produced, secondary recovery operations and pressure variations.
3259corrosion control, corrosion rate, secondary recovery
3260None
3261None
3262--
3263carbonate
32641.n. [Geology]
3265A class of sedimentary rock whose chief mineral constituents (95% or more) are calcite and aragonite (both CaCo3) and dolomite [CaMg(CO3)2], a mineral that can replace calcite during the process of dolomitization. Limestone, dolostone or dolomite, and chalk are carbonate rocks. Although carbonate rocks can be clastic in origin, they are more commonly formed through processes of precipitation or the activity of organisms such as coral and algae. Carbonates form in shallow and deep marine settings, evaporitic basins, lakes and windy deserts. Carbonate rocks can serve as hydrocarbon reservoir rocks, particularly if their porosity has been enhanced through dissolution. They rely on fractures for permeability.
3266chert, clastic sediment, karst, micrite, reef, reservoir, siliciclastic sediment, stylolite
3267None
3268None
3269--
3270carbonate
32712.adj. [Geology]
3272A group of minerals found mostly in limestone and dolostone that includes aragonite, calcite and dolomite. Calcite is the most abundant and important of the carbonate minerals.
3273dolomitization, evaporite, humic acid, micrite, reef, siderite, sour gas
3274None
3275None
3276--
3277chemical wash
32781.n. [Well Completions]
3279A fluid, generally water-based, to thin and disperse mud in preparation for cementing. The chemical wash is pumped ahead of the cement slurry to help ensure effective mud removal and efficient cement placement. Other specialized chemical washes may be used in the remedial treatment of scales or paraffin deposits in production tubulars.
3280None
3281None
3282None
3283--
3284coiled tubing completion
32851.n. [Well Completions]
3286A completion that utilizes coiled tubing as the production conduit, or as a means of conveying and installing completion equipment or components. Since the coiled tubing string is continuous, problems associated with connections are avoided. Also, the pressure-control equipment used on coiled tubing operations enables work to be safely conducted on live wells.
3287None
3288None
3289None
3290--
3291corrosion coupon
32921.n. [Drilling Fluids]
3293A specimen of test material to be used in a corrosion test, usually a metal strip or ring shaped to fit into a testing cell or between joints of drillpipe. Rings, or coupons, are weighed before and after exposure, and weight loss is measured. They are also examined for pits and cracks. Corrosion products are analyzed to define the type of corrosion reaction.
3294anode, hydrogen sulfide, sacrificial anode, stress-corrosion cracking, sulfide scavenger
3295None
3296None
3297--
3298carbonate ion
32991.n. [Drilling Fluids]
3300An anion with formula CO3-2. Carbonate chemistry involves a pH-dependent equilibrium between H2O, H+, OH-, CO2, HCO3- and CO3-2. At low pH, carbon dioxide [CO2] dominates. As pH rises from acidic toward neutral, HCO3- ions dominate. As pH rises above neutral, CO3-2 ions dominate. If no component is lost from the system (such as CO2 gas evolving), changing pH up and down continually reverses the relative proportion of the carbonate species. Carbonates play several important roles in water mud chemistry. One role is the corrosion of metals by acidic CO2. A second is the formation of calcium carbonate [CaCO3] scale on surfaces by carbonate and calcium ion reactions. Another role is in the chemistry of deflocculated mud, where bicarbonate ions prevent attachment of deflocculants such as lignosulfonate, onto clay edge charges.
3301alkalinity, buffered mud, calcium hydroxide, calcium sulfate, carbonate test, Garrett Gas Train, hydrolysis, lignite, sodium bicarbonate, sodium carbonate
3302None
3303None
3304--
3305chemical marker injection
33061.n. [Production Logging]
3307A technique in which a slug of material is introduced into the flowstream of a producing well to determine the flow rate of one or more of the fluids. The marker has specific properties, such as high neutron capture cross section, that allow it to be detected by sensors of a production logging tool. Some markers are specifically designed to be soluble in only one fluid phase, so that they can be used to produce a phase-velocity log. The term refers to nonradioactive markers, in contrast to the more traditional radioactive markers, or tracers.
3308production log, tracer, tracer measurement
3309None
3310None
3311--
3312coiled tubing drilling
33131.n. [Drilling]
3314The use of coiled tubing with downhole mud motors to turn the bit to deepen a wellbore. Coiled tubing drilling operations proceed quickly compared to using a jointed pipe drilling rig because connection time is eliminated during tripping. Coiled tubing drilling is economical in several applications, such as drilling slimmer wells, areas where a small rig footprint is essential, reentering wells and drilling underbalanced.
3315coiled tubing, mud motor, trip, tripping pipe
3316None
3317None
3318--
3319corrosion inhibitor
33201.n. [Well Workover and Intervention]
3321A chemical additive used in acid treatments to protect iron and steel components in the wellbore and treating equipment from the corrosive treating fluid. Corrosion inhibitors generally are mixed with the treatment fluid and are formulated to be effective in protecting the metal components the fluid is likely to contact. This protection must remain effective under the anticipated pressure and temperature environment for the duration of the treatment.
3322treatment fluid
3323None
3324None
3325--
3326corrosion inhibitor
33272.n. [Enhanced Oil Recovery]
3328In matrix treatments, a chemical added to acid that adsorbs on the pipe surface to form a protective film. This decreases the destructive reaction of acid with metals. The inhibitor does not completely stop the corrosion reaction, but it eliminates more than 99% of the metal losses that would occur if the inhibitor were not present. The inhibitor has little or no effect on the reaction rate of acid with limestone, dolomite or acid-soluble minerals.Specific corrosion inhibitors are environmentally compatible, effective in hydrogen sulfide [H2S] environments, effective on high chrome steel, and effective on special steel alloys, such as coiled tubing. These inhibitors may be used at temperatures approaching 500oF [260oC].
3329None
3330None
3331None
3332--
3333carbonate scale
33341.n. [Well Completions]
3335A common type of mineral deposit that is often found on wellbore tubulars and components as the saturation of produced water is affected by changing temperature and pressure conditions in the production conduit. Carbonate scales have a high dissolution rate in common oilfield acids and generally can be effectively removed using acid or chemical treatments. Scale inhibition techniques also may be used to prevent scale formation. In the majority of cases, scale prevention is simpler and more cost-effective than attempting a cure.
3336scale inhibitor, scale removal, scale-inhibitor squeeze
3337None
3338None
3339--
3340chert
33411.n. [Geology]
3342A sedimentary rock and a variety of quartz made of extremely fine-grained, or cryptocrystalline, silica, also called chalcedony. The silica might be of organic origin, such as from the internal structures of sponges called spicules, or inorganic origin, such as precipitation from solution. The latter results in the formation of flint. Chert can form beds, but is more common as nodules in carbonate rocks.
3343limestone
3344None
3345cherty
3346--
3347coiled tubing string
33481.n. [Well Workover and Intervention]
3349A continuous length of low-alloy carbon-steel tubing that can be spooled on a reel for transport, then deployed into a wellbore for the placement of fluids or manipulation of tools during workover and well-intervention operations. The process of spooling and straightening a coiled tubing string imparts a high degree of fatigue to the tube material. Therefore, a coiled tubing string should be regarded as a consumable product with a finite service life. Predicting and managing the factors that affect the safe working life of a coiled tubing string are key components of the string-management system necessary for ensuring safe and efficient coiled tubing operations.
3350None
3351None
3352None
3353--
3354corrosion resistant alloy cra
33551.n. [Well Completions]
3356A specially formulated material used for completion components in wells likely to present corrosion problems. Corrosion-resistant alloys can be formulated for a wide range of aggressive wellbore conditions. However, cost generally determines the viability of any particular completion design. Alloys with a high chrome content are commonly used for tubing strings.
3357None
3358None
3359None
3360--
3361carboxymethylcellulose
33621.n. [Drilling Fluids]
3363A drilling-fluid additive used primarily for fluid-loss control, manufactured by reacting natural cellulose with monochloroacetic acid and sodium hydroxide [NaOH] to form CMC sodium salt. Up to 20 wt % of CMC may be NaCl, a by-product of manufacture, but purified grades of CMC contain only small amounts of NaCl. To make CMC, OH groups on the glucose rings of cellulose are ether-linked to carboxymethyl (-OCH2-COO-) groups. (Note the negative charge.) Each glucose ring has three OH groups capable of reaction, degree-of-substitution = 3. Degree of substitution determines water solubility and negativity of the polymer, which influences a CMC's effectiveness as a mud additive. Drilling grade CMCs used in muds typically have degree-of-substitution around 0.80 to 0.96. Carboxymethylcellulose is commonly supplied either as low-viscosity ("CMC-Lo Vis") or high-viscosity ("CMC-Hi Vis") grades, both of which have API specifications. The viscosity depends largely on the molecular weight of the starting cellulose material.Reference:Hughes TL, Jones TG and Houwen OW: "The Chemical Characterization of CMC and Its Relationship to Drilling-Mud Rheology and Fluid Loss," SPE Drilling & Completion 8, no. 3 (September 1993): 157-164.
3364bentonite, calcium carbonate, carboxymethyl starch, carboxymethyl hydroxyethylcellulose, cellulosic polymer, emulsion mud, gyp mud, hydroxyethylcellulose, lime mud, polyanionic cellulose, potassium mud, seawater mud
3365CMC
3366None
3367--
3368cherty
33691.adj. [Geology]
3370Containing chert, asedimentaryrockand a variety ofquartzmade of extremely fine-grained, or cryptocrystalline,silica, also called chalcedony. The silica might be of organic origin, such as from the internal structures of sponges called spicules, or inorganic origin, such asprecipitationfrom solution. The latter results in the formation of flint. Chert can form beds, but is more common as nodules in carbonaterocks.
3371limestone
3372None
3373None
3374--
3375cold heavy oil production with sand
33761.n. [Enhanced Oil Recovery, Heavy Oil]
3377A non-thermal primary process for producing heavy oil, also called CHOPS. In this method, continuous production of sand improves the recovery of heavy oil from the reservoir. There is both a theoretical basis and physical evidence that, in many cases, wormholes are formed in the unconsolidated sand reservoir, thereby increasing oil productivity. In most cases, an artificial lift system is used to lift the oil with sand.
3378wormhole
3379None
3380CHOPS
3381--
3382cosolvent
33831.n. [Enhanced Oil Recovery]
3384A chemical used in small quantities to improve the effectiveness of a primary solvent in a chemical process.
3385None
3386None
3387None
3388--
3389carried working interest
33901.n. [Oil and Gas Business]
3391A working interest generally paid in consideration for work related to the prospect. This interest is paid, or carried, for the drilling and or completion costs as specified in the contract between the parties, by another working interest owner typically until casing point is reached, or through the tanks, meaning through completion of the well, as agreed upon contractually.
3392None
3393None
3394None
3395--
3396choke manifold
33971.n. [Drilling]
3398A set of high-pressure valves and associated piping that usually includes at least two adjustable chokes, arranged such that one adjustable choke may be isolated and taken out of service for repair and refurbishment while well flow is directed through the other one.
3399choke line
3400None
3401None
3402--
3403choke manifold
34042.n. [Well Completions]
3405A manifold assembly incorporating chokes, valves and pressure sensors used to provide control of flow back or treatment fluids.
3406treatment fluid
3407None
3408None
3409--
3410collapse pressure
34111.n. [Well Workover and Intervention]
3412The pressure at which a tube, or vessel, will catastrophically deform as a result of differential pressure acting from outside to inside of the vessel or tube. The collapse-pressure rating of perfectly round tubing is relatively high. However, when the tubing is even slightly oval, the differential pressure at which the tube will collapse may be significantly reduced. This is an important factor in determining the operating limits of coiled tubing strings since the action of spooling the string tends to induce some ovality.
3413coiled tubing string
3414None
3415None
3416--
3417counterbalance weight
34181.n. [Production Testing]
3419Part of rod pumping unit. The counterbalance weight is installed on the end of the walking beam, opposite to the end over the well, and counterbalances the weight of the sucker rods and the fluid being pumped.
3420rod pump, rod unit, sucker rod pump
3421None
3422None
3423--
3424carrier fluid
34251.n. [Well Completions]
3426A fluid that is used to transport materials into or out of the wellbore. Carrier fluids typically are designed according to three main criteria: the ability to efficiently transport the necessary material (such as pack sand during a gravel pack), the ability to separate or release the materials at the correct time or place, and compatibility with other wellbore fluids while being nondamaging to exposed formations.
3427None
3428None
3429None
3430--
3431chromate salt
34321.n. [Drilling Fluids]
3433A type of salt in which chromium atoms are in the plus-6 valence state, such as potassium chromate, K2CrO4. Chromium compounds of various types have been used in lignite and lignosulfonate and other mud additives to enhance thermal stability. Since the late 1970s, they are prohibited in muds to be discarded offshore and in other environmentally sensitive areas of the US.
3434chloride test, chrome lignite, chrome lignosulfonate, chrome-free, chromic salt, deflocculated mud, endpoint, indicator, redox, sodium chromate
3435None
3436None
3437--
3438collar locator
34391.n. [Well Completions]
3440A downhole tool or logging device used to detect and track (log) casing or tubing collars across a zone of interest, typically for correlation purposes. Most collar locators detect the magnetic anomaly created by the mass of the steel collar and transmit a signal to surface-display and depth correlation equipment.
3441casing collar locator (CCL)
3442None
3443None
3444--
3445coupling
34461.n. [Geophysics]
3447The state of being attached to another entity: A well-planted geophone has a coupling to the Earth's surface or to a borehole wall that allows it to record ground motion during acquisition of seismic data.
3448geophone, plant, transition zone, tube wave
3449None
3450None
3451--
3452coupling
34532.n. [Geophysics]
3454An electrical or mechanical device that joins parts of systems and can affect the interaction of, or energy transfer between, parts of systems. Electrical couplings promote the passage of certain signals but prevent the passage of others, such as an alternating current coupling that excludes direct current.
3455signal
3456None
3457None
3458--
3459carrying capacity
34601.n. [Drilling Fluids]
3461The 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.
3462Brookfield viscometer, cuttings, drill-in fluid, rheology, rheology modifier, saltwater mud, spud mud, XC polymer
3463cuttings lifting, hole cleaning
3464None
3465--
3466chrome free
34671.adj. [Drilling Fluids]
3468Pertaining to a mud additive (usually lignosulfonate or lignite) that does not contain any chromium compounds.
3469None
3470None
3471chrome-free
3472--
3473collar log
34741.n. [Well Completions]
3475A log showing the depth or relative position of casing or tubing collars that is used to correlate depth for depth-sensitive applications such as perforating or isolation treatments. Indications are provided by a collar locator tool and correlations are made with previous baseline logs, such as the gamma ray log, or the casing or tubing running tally prepared during the installation process.
3476None
3477None
3478None
3479--
3480coupon
34811.n. [Drilling Fluids]
3482An abbreviation for corrosion coupon, a specimen of test material to be used in a corrosion test, usually a metal strip or ring shaped to fit into a testing cell or between joints of drillpipe. Rings, or coupons, are weighed before and after exposure, and weight loss is measured. They are also examined for pits and cracks. Corrosion products are analyzed to define the type of corrosion reaction.
3483anode, hydrogen sulfide, stress-corrosion cracking, sulfide scavenger
3484corrosion coupon
3485None
3486--
3487coupon
34882.n. [Well Workover and Intervention]
3489An abbreviation for electrical coupon, an 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.
3490None
3491None
3492None
3493--
3494casing
34951.n. [Drilling]
3496Large-diameter pipe lowered into an openhole and cemented in place. The well designer must design casing to withstand a variety of forces, such as collapse, burst, and tensile failure, as well as chemically aggressive brines. Most casing joints are fabricated with male threads on each end, and short-length casing couplings with female threads are used to join the individual joints of casing together, or joints of casing may be fabricated with male threads on one end and female threads on the other. Casing is run to protect fresh water formations, isolate a zone of lost returns or isolate formations with significantly different pressure gradients. The operation during which the casing is put into the wellbore is commonly called "running pipe." Casing is usually manufactured from plain carbon steel that is heat-treated to varying strengths, but may be specially fabricated of stainless steel, aluminum, titanium, fiberglass and other materials.
3497box, brine, cased hole, casing grade, cement bond log, concentric, day rate, displacement, float joint, float shoe, joint, pin, scratcher, turnkey
3498None
3499None
3500--
3501casing
35022.n. [Well Completions]
3503Steel pipe cemented in place during the construction process to stabilize the wellbore. The casing forms a major structural component of the wellbore and serves several important functions: preventing the formation wall from caving into the wellbore, isolating the different formations to prevent the flow or crossflow of formation fluid, and providing a means of maintaining control of formation fluids and pressure as the well is drilled. The casing string provides a means of securing surface pressure control equipment and downhole production equipment, such as the drilling blowout preventer (BOP) or production packer. Casing is available in a range of sizes and material grades.
3504BOP, casing grade, casing joint
3505None
3506None
3507--
3508chrome lignosulfonate
35091.n. [Drilling Fluids]
3510A lignosulfonate that has been treated by mixing or reacting into the molecular structure some form of chromium (either chromate or chromic salt). Although still used today in less environmentally sensitive areas, it has been replaced by iron or calcium lignosulfonates. Ferro-chrome lignosulfonate is a popular type of deflocculant that contains iron and chromium salts.
3511chromate salt, chrome lignite, chrome-free, conventional mud, ferro-chrome lignosulfonate
3512None
3513None
3514--
3515collector
35161.n. [Well Workover and Intervention]
3517The electrical device used on the axle of a spool or reel to provide electrical continuity between the rotating reel core and the stationary reel chassis. When using a coiled tubing string equipped with an electrical conductor, such as required during coiled tubing logging operations, a collector is fitted to the reel axle to allow connection of the surface data-acquisition equipment.
3518None
3519None
3520None
3521--
3522cpmg
35231.adj. [Formation Evaluation]
3524In a nuclear magnetic resonance (NMR) measurement, referring to the cycle of radio frequency pulses designed by Carr, Purcell, Meiboom and Gill to produce pulse echoes and counteract dephasing due to magnetic field inhomogeneities. In the CPMG sequence, an initial radio frequency pulse is applied long enough to tip the protons into a plane perpendicular to the static magnetic field (the 90o pulse). Initially the protons precess in unison, producing a large signal in the antenna, but then quickly dephase due to the inhomogeneities. Another pulse is applied, long enough to reverse their direction of precession (the 180o pulse), and causing them to come back in phase again after a short time. Being in phase, they produce another strong signal called an echo. They quickly dephase again but can be rephased by another 180o pulse. Rephasing is repeated many times, while measuring the magnitude of each echo. This magnitude decreases with time due to molecular relaxation mechanisms surface, bulk and diffusion. One measurement typically may comprise many hundreds of echoes, while the time between each echo (the echo spacing) is of the order of 1 ms or less.Carr HY and Purcell EM: ?Effects of Diffusion on Free Precession in Nuclear Magnetic Resonance Experiments,? Physical Review 94, no. 3 (1954): 630-638.Meiboom S and Gill D: ?Modified Spin-Echo Method for Measuring Nuclear Relaxation Times,? The Review of Scientific Instruments 29, no. 8 (1958): 688-691.
3525echo spacing, longitudinal relaxation, nuclear magnetic resonance, nuclear magnetic resonance measurement, pulse-echo, T1, T2, transverse relaxation
3526None
3527None
3528--
3529casing bowl
35301.n. [Well Completions]
3531A wellhead component or a profile formed in wellhead equipment in which the casing hanger is located when a casing string has been installed. The casing bowl incorporates features to secure and seal the upper end of the casing string and frequently provides a port to enable communication with the annulus.
3532None
3533None
3534casing spool
3535--
3536chrome tubing
35371.n. [Well Workover and Intervention]
3538Tubing manufactured from an alloy containing a high proportion of chrome, typically greater than 13%. Chrome tubing is classified as a corrosion-resistant alloy (CRA) and is used where the wellbore conditions or reservoir fluid create a corrosive environment that conventional tubing cannot safely withstand. Wells that produce hydrogen sulfide, and similar corrosive fluids, typically require chrome tubing.
3539corrosion-resistant alloy (CRA)
3540None
3541None
3542--
3543collision
35441.n. [Geology]
3545An interaction of lithospheric plates that can result in the formation of mountain belts and subduction zones. The collision of two plates of continental lithosphere, known as an A-type collision, can produce high mountains as rocks are folded, faulted and uplifted to accommodate the converging plates, as observed in the Alps and the Himalayas. B-type collisions, in which oceanic lithospheric plates collide with continental lithospheric plates, typically produce a subduction zone where the relatively denser oceanic plate descends below the relatively lighter continental plate, as seen on the Pacific coast of South America.
3546convergence, earthquake, fault, fold, passive margin, plate tectonics, volcano
3547None
3548None
3549--
3550cracking
35511.n. [Heavy Oil]
3552The process of splitting a large heavy hydrocarbon molecule into smaller, lighter components. The process involves very high temperature and pressure and can involve a chemical catalyst to improve the process efficiency.
3553None
3554None
3555None
3556--
3557casing centralizer
35581.n. [Drilling]
3559A mechanical device that keeps casing from contacting the wellbore wall. A continuous 360-degree annular space around casing allows cement to completely seal the casing to the borehole wall. There are two distinct classes of centralizers. The older and more common is a simple, low-cost bow-spring design. Since the bow springs are slightly larger than the wellbore, they can provide complete centralization in vertical or slightly deviated wells. However, they do not support the weight of the casing very well in deviated wellbores. The second type is a rigid blade design. This type is rugged and works well even in deviated wellbores, but since the centralizers are smaller than the wellbore, they will not provide as good centralization as bow-spring type centralizers in vertical wells. Rigid-blade casing centralizers are slightly more expensive and can cause trouble downhole if the wellbore is not in excellent condition.
3560annulus, bow-spring centralizer, deviated hole
3561None
3562None
3563--
3564chrome free
35651.adj. [Drilling Fluids]
3566Pertaining to a mud additive (usually lignosulfonate or lignite) that does not contain any chromium compounds.
3567chromate salt, chrome lignite, chrome lignosulfonate, chromic salt, deflocculant
3568None
3569None
3570--
3571colloid
35721.n. [Drilling Fluids]
3573A finely divided, solid material, which when dispersed in a liquid medium, scatters a light beam and does not settle by gravity; such particles are usually less than 2 microns in diameter. Some drilling fluid materials become colloidal when used in a mud, such as bentonite clay, starch particles and many polymers. Oil muds contain colloidal emulsion droplets, organophilic clays and fatty-acid soap micelles.
3574anion, calcium contamination, clay extender, clay-water interaction, colloidal solids, colloidal suspension, dispersion, hydration, micelle, oil mud, oil-mud emulsifier, peptize, peptized clay, peptizing agent, polymer, prehydration, silt
3575None
3576None
3577--
3578craton
35791.n. [Geology]
3580A stable area of continental crust that has not undergone much plate tectonic or orogenic activity for a long period. A craton includes a crystalline basement of commonly Precambrian rock called a shield, and a platform in which flat-lying or nearly flat-lying sediments or sedimentary rock surround the shield. A commonly cited example of a craton is the Canadian Shield.
3581basement, orogeny, plate tectonics, platform, sedimentary
3582None
3583None
3584--
3585casing collar locator ccl
35861.n. [Perforating, Well Completions]
3587A downhole tool used to confirm or correlate treatment depth using known reference points on the casing string. The casing collar locator is an electric logging tool that detects the magnetic anomaly caused by the relatively high mass of the casing collar. A signal is transmitted to surface equipment that provides a screen display and printed log enabling the output to be correlated with previous logs and known casing features such as pup joints installed for correlation purposes.
3588None
3589None
3590None
3591--
3592churn flow
35931.n. [Well Completions, Production Logging]
3594Amultiphaseflow regimein 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. Unlikeslug flow, neither phase is continuous. The gas slugs are relatively unstable, and take on large, elongated shapes. Also known astransition flow, this flow is an intermediate flow condition between slugflow and mist flow, and occurs at relatively high gas velocity. As the gas velocity increases, it changes intoannular flow.
3595annular flow, bubble flow, flow regime, flow structure, mist flow, multiphase fluid flow, slug, slug flow
3596transition flow
3597None
3598--
3599churn flow
36002.n. [Production Logging]
3601A 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. Unlike slug flow, neither phase is continuous. The gas slugs are relatively unstable, and take on large, elongated shapes. Churn flow occurs at relatively high gas velocity and is similar to froth flow. As the gas velocity increases, it changes into annular flow.
3602bubble flow, flow structure, mist flow
3603None
3604None
3605--
3606colloidal
36071.adj. [Drilling Fluids]
3608Referring to a finely divided, solid material, which when dispersed in a liquid medium scatters a light beam and does not settle bygravity; such particles are usually less than 2 microns in diameter. Somedrilling fluidmaterials such asbentoniteclay,starchparticles and many polymers becomecolloidal when used in amud. Oil muds contain colloidalemulsiondroplets,organophilicclays and fatty-acid soapmicelles.
3609alum, clay-water interaction, colloid, colloidal solids, micelle, oil mud, oil-mud emulsifier, peptizing agent, polymer, prehydration
3610None
3611None
3612--
3613critical angle
36141.n. [Geophysics]
3615The angle of incidence according to Snell's law at which a refracted wave travels along the interface between two media. It can be quantified mathematically as follows:sin θc = V1 / V2,whereθc = the critical angleV1 = velocity of the first mediumV2 = velocity of the first medium, which is greater than V1.
3616angle of incidence, critical reflection, head wave, refraction, refractor, Snell's law
3617None
3618None
3619--
3620casing collar log
36211.n. [Perforating, Well Completions]
3622A log provided by a casing collar locator tool that generally incorporates a gamma ray log to correlate the relative position of casing string features, such as the location of a pup joint, with the reservoir or formation of interest.
3623casing collar locator (CCL)
3624None
3625None
3626--
3627circle shooting
36281.n. [Geophysics]
3629A technique for acquiring full-azimuth marine seismic data. This technique uses a vessel equipped with source arrays and streamers to shoot and record seismic data; however, unlike conventional surveys acquired in a series of parallel straight lines, circle shooting surveys are acquired as the vessel steams in a series of overlapping, continuously linked circles, or coils. The circular shooting geometry acquires a full range of offset data across every azimuth to sample the subsurface geology in all directions. The resulting full azimuth (FAZ) data are used to image complex geology, such as highly faulted strata, basalt, carbonate reefs and subsalt formations.
3630acquisition, salt dome
3631None
3632None
3633--
3634colloidal solids
36351.n. [Drilling Fluids]
3636Solid particles of size less than 2 microns equivalent spherical diameter, also identified as clay by definitions in International Standards Organization ISO/CD 13501, par. 3.1.17. Because of extremely small size, these solids largely defy direct removal by mechanical devices that rely on screening or gravitational forces. Their removal is aided by chemical aggregation prior to gravity separation or filtration.
3637acrylamide polymer, acrylamide-acrylate polymer, acrylate polymer, Bingham plastic model, clay extender, clay-water interaction, clear-water drilling, closed mud system, colloid, dispersion, dispersion, fines, gel, gelled-up mud, gumbo, native-solids mud, plastic viscosity, prehydrated bentonite, reserve-mud pit, siderite, silicate mud, smectite clay, wastewater cleanup, water clarification
3638None
3639None
3640--
3641critical damping
36421.n. [Geophysics]
3643The minimum damping that will prevent or stop oscillation in the shortest amount of time, typically associated with oscillatory systems like geophones. Critical damping is symbolized by μc.
3644damping, geophone
3645None
3646None
3647--
3648casing completion
36491.n. [Well Completions]
3650A completion configuration in which a production casing string is set across the reservoir interval and perforated to allow communication between the formation and wellbore. The casing performs several functions, including supporting the surrounding formation under production conditions, enabling control of fluid production through selective perforation and allowing subsequent or remedial isolation by packers, plugs or special treatments.
3651conductor pipe, intermediate casing, packer, perforated interval, production casing, selective perforating, surface casing
3652None
3653Antonyms:openhole completion
3654--
3655circulate
36561.vb. [Drilling]
3657To pump fluid through the whole active fluid system, including the borehole and all the surface tanks that constitute the primary system.
3658bottomhole circulating temperature, break circulation, circulation, pack off
3659None
3660None
3661--
3662colloidal suspension
36631.n. [Drilling Fluids]
3664A finely divided, solid material dispersed in a liquid medium. The solid particles scatter a light beam and do not settle bygravity; they are usually less than 2 microns in diameter. Somedrilling fluidmaterials such asbentoniteclay,starchparticles and many polymers become colloidal when used in amud. Oil muds contain colloidalemulsiondroplets,organophilicclays and fatty-acid soapmicelles.
3665colloid
3666None
3667None
3668--
3669critical reflection
36701.n. [Geophysics]
3671A reflection, typically at a large angle, that occurs when the angle of incidence and the angle of reflection of a wave are equal to the critical angle.
3672angle of incidence, critical angle, reflection
3673None
3674None
3675--
3676casing grade
36771.n. [Drilling]
3678A system of identifying and categorizing the strength of casing materials. Since most oilfield casing is of approximately the same chemistry (typically steel), and differs only in the heat treatment applied, the grading system provides for standardized strengths of casing to be manufactured and used in wellbores. The first part of the nomenclature, a letter, refers to the tensile strength. The second part of the designation, a number, refers to the minimum yield strength of the metal (after heat treatment) at 1000 psi [6895 KPa]. For example, the casing grade J-55 has minimum yield strength of 55,000 psi [379,211 KPa]. The casing grade P-110 designates a higher strength pipe with minimum yield strength of 110,000 psi [758,422 KPa]. The appropriate casing grade for any application typically is based on pressure and corrosion requirements. Since the well designer is concerned about the pipe yielding under various loading conditions, the casing grade is the number that is used in most calculations. High-strength casing materials are more expensive, so a casing string may incorporate two or more casing grades to optimize costs while maintaining adequate mechanical performance over the length of the string. It is also important to note that, in general, the higher the yield strength, the more susceptible the casing is to sulfide stress cracking (H2S-induced cracking). Therefore, if H2S is anticipated, the well designer may not be able to use tubulars with strength as high as he or she would like.
3679casing string, float shoe, hydrogen sulfide
3680None
3681None
3682--
3683circulate out
36841.vb. [Drilling]
3685To pump the drilling fluid until a sample from the bottom of the hole reaches the surface. This is commonly performed when drilling has ceased so that the wellsite geologist may collect a cuttings sample from the formation being drilled, or when the driller suspects that a small amount of gas has entered the wellbore. Thus, by circulating out, the gas bubble is eased out of the wellbore safely.
3686drilling fluid
3687None
3688None
3689--
3690combination string
36911.n. [Drilling]
3692Another term for a tapered string: a string of drillpipe or casing that consists of two or more sizes or weights. In most tapered strings, a larger diameter pipe or casing is placed at the top of the wellbore and the smaller size at the bottom. Note that since the pipe is put into the well bottom first, the smaller pipe is run into the hole first, followed by the larger diameter. Other than the different sizes, which are usually chosen to optimize well economics, there is nothing distinctive about the pipe sections. However, pipe-handling tools must be available for each pipe size, not just one size, as is the typical case.
3693None
3694tapered string
3695None
3696--
3697crooked hole
36981.n. [Drilling]
3699Antiquated term for a deviated wellbore, usually used to describe a well deviated accidentally during the drilling process.
3700deviated hole, directional drilling
3701None
3702None
3703--
3704casing gun
37051.n. [Perforating]
3706A perforating gun assembly designed to be used in a wellbore before the production tubulars or completion equipment have been installed, thus allowing access for a larger diameter gun assembly. Casing guns are typically 3- to 5-in. In diameter and carry up to four perforating charges per foot.
3707carrier gun, perforating charge, perforation density, shaped charge
3708None
3709None
3710--
3711circulation device
37121.n. [Well Completions]
3713A completion component, generally included in the lower assembly near the packer, that allows communication between the tubing and annulus. Circulation devices enable the circulation of fluids for well control or kickoff purposes.
3714sliding sleeve
3715None
3716None
3717--
3718common depth point
37191.n. [Geophysics]
3720In multichannel seismic acquisition where beds do not dip, the common reflection point at depth on a reflector, or the halfway point when a wave travels from a source to a reflector to a receiver. In the case of flat layers, the common depth point is vertically below the common midpoint. In the case of dipping beds, there is no common depth point shared by multiple sources and receivers, so dip moveout processing is necessary to reduce smearing, or inappropriate mixing, of the data.
3721channel, depth point, dip, fold, stacking velocity
3722None
3723CDP
3724--
3725cross dipole
37261.adj. [Formation Evaluation]
3727Describing a waveform or a log that has been recorded by a set of dipole receivers oriented orthogonally (or 900 out of line) with a dipole transmitter. In sonic logging, cross-dipole flexural modes are used to determine shear anisotropy together with in-line flexural modes. The data are processed using the Alford rotation.
3728Alford rotation, array sonic, cross dipole, sonic log
3729None
3730None
3731--
3732casing hanger
37331.n. [Well Completions]
3734The subassembly of a wellhead that supports the casing string when it is run into the wellbore. The casing hanger provides a means of ensuring that the string is correctly located and generally incorporates a sealing device or system to isolate the casing annulus from upper wellhead components.
3735wellhead
3736None
3737None
3738--
3739circulation loss
37401.n. [Drilling]
3741The loss of drilling fluid to a formation, usually caused when the hydrostatic head pressure of the column of drilling fluid exceeds the formation pressure. This loss of fluid may be loosely classified as seepage losses, partial losses or catastrophic losses, each of which is handled differently depending on the risk to the rig and personnel and the economics of the drilling fluid and each possible solution.
3742hydrostatic pressure
3743None
3744lost circulation
3745--
3746common midpoint
37471.n. [Geophysics]
3748In multichannel seismic acquisition, the point on the surface halfway between the source and receiver that is shared by numerous source-receiver pairs. Such redundancy among source-receiver pairs enhances the quality of seismic data when the data are stacked. The common midpoint is vertically above the common depth point, or common reflection point. Common midpoint is not the same as common depth point, but the terms are often incorrectly used as synonyms.
3749bin, brute stack, channel, common midpoint method, fold, gather, reflector, stack, velocity analysis
3750None
3751CMP
3752--
3753cross section
37541.n. [Geology]
3755A diagram of a vertical section through a volume, as opposed to the surface, "bird's eye," or plan view of a map. Cross sections are useful for displaying the types and orientations of subsurface structures and formations.
3756fence diagram, lithostratigraphy
3757None
3758None
3759--
3760cross section
37612.n. [Formation Evaluation]
3762Constant of proportionality relating the fraction of incident particles that undergo an interaction to the thickness and number of target atoms within a material, and the incident flux. It is a measure of the probability of an interaction. The microscopic cross section has units of area per interacting atom. The macroscopic cross section, which is the product of the microscopic cross section and the number of particles per unit volume, has units of inverse length. Cross sections for most reactions are determined experimentally and depend on the type of interaction, the material and the energy of the incident particle.
3763Compton scattering, pair production, photoelectric effect
3764None
3765None
3766--
3767casing inspection log
37681.n. [Production Logging]
3769An in situ record of casing thickness and integrity, to determine whether and to what extent the casing has undergone corrosion. The term refers to an individual measurement, or a combination of measurements using acoustic, electrical and mechanical techniques, to evaluate the casing thickness and other parameters. The log is usually presented with the basic measurements and an estimate of metal loss. It was first introduced in the early 1960s. Today the terms casing-evaluation log and pipe-inspection log are used synonymously.
3770casing-potential profile, eddy-current measurement
3771None
3772None
3773--
3774circulation sub
37751.n. [Well Workover and Intervention]
3776A downhole tool typically used with motors or assemblies that restrict the allowable fluid-circulation rates. When operated, the circulation sub allows a higher circulation rate to be established by opening a path to the annulus in the top section of the tool string. This is especially useful in applications such as drilling in slim-diameter wells, where a higher circulation rate may be necessary to effect good cuttings transport and hole cleaning before the string is retrieved.
3777slimhole well
3778None
3779None
3780--
3781communitization
37821.n. [Oil and Gas Business]
3783The combining of smaller federal tracts of land to total the acreage required by the US Bureau of Land Management and/or state regulations to form a legal spacing and proration unit.
3784pooling, spacing unit, unitization
3785None
3786None
3787--
3788crossflow
37891.n. [Drilling]
3790The flow of fluid across the bottom of the bit after it exits the bit nozzles, strikes the bottom or sides of the hole and turns upwards to the annulus. Modern, well-designed bits maximize crossflow using an asymmetric nozzle arrangement.
3791bit nozzle
3792None
3793None
3794--
3795crossflow
37962.n. [Drilling]
3797The flow of reservoir fluids from one zone to another. Crossflow can occur when a lost returns event is followed by a well control event. The higher pressured reservoir fluid flows out of the formation, travels along the wellbore to a lower pressured formation, and then flows into the lower pressure formation.
3798annulus, backflow, bit nozzle, lost returns, well control
3799None
3800None
3801--
3802crossflow
38033.n. [Well Completions]
3804A condition that exists when two production zones with dissimilar pressure characteristics are allowed to communicate during production. Reservoir fluid from the high-pressure zone will flow preferentially to the low-pressure zone rather than up the production conduit unless the production parameters are closely controlled.
3805None
3806None
3807None
3808--
3809casing joint
38101.n. [Well Completions]
3811A length of steel pipe, generally around 40 ft [13 m] long with a threaded connection at each end. Casing joints are assembled to form a casing string of the correct length and specification for the wellbore in which it is installed.
3812casing
3813None
3814None
3815--
3816circulation system
38171.n. [Drilling]
3818The complete, circuitous path that the drilling fluid travels. Starting at the main rig pumps, major components include surface piping, the standpipe, the kelly hose (rotary), the kelly, the drillpipe, drill collars, bit nozzles, the various annular geometries of the openhole and casing strings, the bell nipple, the flowline, the mud-cleaning equipment, the mud tanks, the centrifugal precharge pumps and, finally, the positive displacement main rig pumps.
3819bit nozzle, casing string, centrifugal pump, drill collar, kelly, positive-displacement pump, surface pipe
3820None
3821None
3822--
3823company man
38241.n. [Drilling]
3825The representative of the oil company or operator on a drilling location. For land operations, the company man is responsible for operational issues on the location, including the safety and efficiency of the project. Even administrative managers are expected to respond to the direction of the company man when they are on the rigsite. Offshore, depending on the regulatory requirements, there may be an offshore installation manager, who supervises the company man on safety and vessel integrity issues, but not on operational issues.
3826drilling foreman, toolpusher
3827company representative
3828None
3829--
3830crosslinker
38311.n. [Well Workover and Intervention]
3832A compound, typically a metallic salt, mixed with a base-gel fluid, such as a guar-gel system, to create a viscous gel used in some stimulation or pipeline cleaning treatments. The crosslinker reacts with the multiple-strand polymer to couple the molecules, creating a fluid of high, but closely controlled, viscosity. Treatments using crosslinkers should take account of the conditions needed to break the gel structure to ensure satisfactory cleanup and disposal.
3833None
3834None
3835None
3836--
3837casing potential profile
38381.n. [Production Logging]
3839An in situ log of the electrical potential on the inner wall of a casing. The log is used to identify intervals that are susceptible to corrosion. A negative slope in the profile indicates a zone in which current is leaving the casing and therefore acting as an anode. Such zones are susceptible to corrosion. The log was first introduced in the early 1960s. Modern logs are recorded with the tool stationary, and measure the potential difference and casing resistance between several pairs of sensors pushed against the casing wall, and between sensors and surface.The log is usually represented with casing resistance and casing axial current. Sharp increases in casing resistance can indicate corroded zones or even holes in the casing. Decreasing axial current with depth indicates a corroding region.
3840casing-inspection log
3841None
3842None
3843--
3844circulation time
38451.n. [Drilling Fluids]
3846The elapsed time formudtocirculatefrom the suction pit, down the wellbore and back to surface. Circulation time allows the mud engineer to catch "in" and "out" samples that accurately represent the same element of mud in a circulating system. Circulation time is calculated from the estimated hole volume and pump rate and can be checked by using tracers such as carbide or rice granules.
3847lag time, mud engineer, mud tracer, mud-in sample, mud-out sample, suction pit
3848cycle time
3849None
3850--
3851company representative
38521.n. [Drilling]
3853The representative of the oil company or operator on a drilling location. For land operations, the company man is responsible for operational issues on the location, including the safety and efficiency of the project. Even administrative managers are expected to respond to the direction of the company man when they are on the rigsite. Offshore, depending on the regulatory requirements, there may be an offshore installation manager, who supervises the company man on safety and vessel integrity issues, but not on operational issues.
3854drilling foreman, toolpusher
3855company man
3856None
3857--
3858crossplot
38591.n. [Reservoir Characterization]
3860A two-dimensional plot with one variable scaled in the vertical (Y) direction and the other in the horizontal (X) axis. The scales are usually linear but may be other functions, such as logarithmic. Additional dimensions may be represented by using color or symbols on the data points. These plots are common tools in the interpretation of petrophysical and engineering data.
3861None
3862None
3863None
3864--
3865casing pressure
38661.n. [Well Completions]
3867A term used in well-control operations, typically during the drilling or workover phases of a well, to describe the pressure in the drillpipe or tubing annulus.
3868well control
3869None
3870None
3871--
3872circulation valve
38731.n. [Well Workover and Intervention]
3874A downhole device that enables circulation through the tubing string and associated annulus. As a completion accessory, a circulation valve is included to circulate fluid for well kill or kickoff. Circulation valves typically are operated by slickline tools and are generally capable of several opening and closing cycles before requiring service.
3875None
3876unloading valve
3877None
3878--
3879compatibility
38801.n. [Enhanced Oil Recovery]
3881In matrix stimulation, a characteristic of rock that indicates formation permeability is not reduced when treating fluids and their additives contact the formation minerals or fluids inside the reservoir.Compatibility is especially important in sandstone treatments, in which potentially damaging reactions may occur. The treatment fluid should remove existing damage without creating additional damage, such as precipitates or emulsions, through interactions with the formation rock or fluids.
3882fluid compatibility test, sensitivity
3883None
3884None
3885--
3886crossplot porosity
38871.n. [Formation Evaluation]
3888The porosity obtained by plotting two porosity logs against each other, normally density and neutron porosity. The computation assumes a particular fluid, usually fresh water, and particular response equations. The result is largely independent of lithology and is often a more reliable estimate of porosity than a single porosity log. It is often displayed as a quicklook log.
3889apparent matrix, fresh water, neutron porosity
3890None
3891None
3892--
3893casing roller
38941.n. [Well Workover and Intervention]
3895A heavy-duty downhole tool used to restore the internal diameter of collapsed or buckled casing. Casing rollers generally are configured with an incremental series of rollers that act to gradually form the damaged casing to the desired size. Depending on the degree of damage and the requirement for wellbore access below the site of damage, the nominal diameter of the casing roller and repaired wellbore may be significantly less than the nominal drift diameter of the original casing string.
3896None
3897None
3898None
3899--
3900citric acid
39011.n. [Drilling Fluids]
3902An organic acid, properly called 2-Hydroxy-1,2,3-propanetricarboxylic acid, with formula C6H8O7. Citric acid is used to reduce the pH of drilling fluids and hence for treatment of cement contamination. It also acts as a polymer stabilizer.
3903chelating agent, drilling fluid, sulfide
3904None
3905None
3906--
3907compensated density log
39081.n. [Formation Evaluation]
3909A density log that has been corrected for the effect of mud and mudcake by using two or more detectors at different spacings from the source. The shorter the spacing, the shallower the depth of investigation and the larger the effect of the mudcake. Thus, a short spaced detector, which is very sensitive to the mudcake, can be used to correct a long-spaced detector, which is only slightly sensitive to it.In a typical two-detector compensation scheme, the density measured by the longest spacing detector is corrected by an amount, delta rho, which is a function of the difference between long- and short-spacing densities. The correction is found to depend on the difference between formation and mudcake density multiplied by mudcake thickness. Although there are three unknowns, simple functions are reliable for moderate corrections. Experimental results are often presented in the form of a spine and ribs plot. There are other schemes using, for example, more detectors. Dual detector density logs were introduced in the mid 1960s.
3910azimuthal density, density measurement, photoelectric effect
3911None
3912None
3913--
3914crown block
39151.n. [Drilling]
3916The fixed set of pulleys (called sheaves) located at the top of the derrick or mast, over which the drilling line is threaded. The companion blocks to these pulleys are the traveling blocks. By using two sets of blocks in this fashion, great mechanical advantage is gained, enabling the use of relatively small drilling line (3/4 to 1 1/2 in. diameter steel cable) to hoist loads many times heavier than the cable could support as a single strand.
3917block, drawworks, mast, sheave, slip-and-cut, traveling block
3918None
3919None
3920--
3921casing scraper
39221.n. [Well Workover and Intervention]
3923A downhole tool incorporating a blade assembly that is used to remove scale and debris from the internal surface of a casing string. Generally run on tubing or drillpipe, casing scrapers are routinely used during workover operations to ensure that the wellbore is clean before reinstalling the completion string.
3924None
3925None
3926None
3927--
3928city gate
39291.n. [Production]
3930The metering and pressure-reducing station where gas is transferred from a high-pressure cross-country transmission line to a low-pressure distribution piping system, usually within a city.
3931None
3932None
3933None
3934--
3935compensated neutron log
39361.n. [Formation Evaluation]
3937A neutron porosity log in which the effects of the borehole environment are minimized by using two detectors. In the most common technique, the two source-detector spacings are chosen so that the ratio of the two count rates is relatively independent of the borehole environment. This ratio is then calibrated in terms of porosity in a known formation and borehole environment typically with the tool placed against the side of an 8-in. [20-cm] borehole in a limestone block, both filled with fresh water at surface temperature and pressure. The response is also determined at different porosities and in sandstones, dolomites and other borehole environments. Correction factors are developed to convert the measured log to the standard conditions.The source and detectors are not azimuthally focused. Wireline tools are run eccentralized against the borehole wall. Since the neutrons emitted into the mud are strongly attenuated, the resulting log is effectively focused into the formation. Measurements-while-drilling tools will normally be unfocused since they are centralized unless the borehole is overgauge.The vertical resolution is about 2 ft [0.6 m], but can be improved by alpha processing.
3938chemical neutron source, epithermal neutron porosity measurement, limestone porosity unit, limestone-compatible scale, thermal neutron porosity measurement, vertical resolution
3939None
3940None
3941--
3942crushed zone
39431.n. [Drilling]
3944The rubblized rock just below the tooth of a rock bit. Rock in the crushed zone fails due to the high compressive stress placed on it by the bit tooth (in the case of a roller-cone bit). The effective creation of and removal of crushed zone rock is important to the efficiency of the drill bit. If the rock is not broken and removed efficiently, the result is akin to effectively drilling the hole twice.
3945roller-cone bit
3946None
3947None
3948--
3949crushed zone
39502.n. [Perforating, Well Completions]
3951The rubblized or damaged zone surrounding a perforation tunnel where the action of the perforating charge or bullet has altered the formation structure and permeability. Although it is generally damaging to production, the severity or extent of the crushed zone depend greatly on the characteristics of the formation, the perforating charge and the underbalance or overbalance conditions at time of perforating. Measures to reduce the effect of the crushed zone include underbalanced perforating in which the crushed zone and perforating debris are flushed from the perforating tunnel by the reservoir fluid as soon as the perforation is created. Where overbalanced perforating techniques are used, it may be necessary to acidize the crushed zone to achieve maximum productivity from the perforated interval.
3952overbalance, underbalance
3953None
3954None
3955--
3956casing shoe
39571.n. [Drilling]
3958The bottom of the casing string, including the cement around it, or the equipment run at the bottom of the casing string.
3959bullhead, float shoe, plug and abandon
3960shoe
3961None
3962--
3963casing shoe
39642.n. [Drilling]
3965A short assembly, typically manufactured from a heavy steel collar and profiled cement interior, that is screwed to the bottom of a casing string. The rounded profile helps guide the casing string past any ledges or obstructions that would prevent the string from being correctly located in the wellbore.
3966float shoe, guide shoe
3967shoe
3968None
3969--
3970classical reservoir modeling
39711.n. [Reservoir Characterization]
3972A conventional method of mapping reservoir parameters in two dimensions, x and y. The resulting map set usually includes the top and bottom structure map derived from seismic and well data and that are used to generate thickness maps, in addition to maps of other geological and petrophysical parameters produced by standard interpolation techniques. These techniques are appropriate for describing reservoirs that are reasonably continuous and not too heterogeneous. They are usually much faster than full 3D techniques or geostatistical methods, but may be inaccurate when applied to description of complex, heterogeneous strata.
3973None
3974None
3975None
3976--
3977compensated density log
39781.n. [Formation Evaluation]
3979A density log that has been corrected for the effect of mud and mudcake by using two or more detectors at different spacings from the source. The shorter the spacing, the shallower the depth of investigation and the larger the effect of the mudcake. Thus, a short spaced detector, which is very sensitive to the mudcake, can be used to correct a long-spaced detector, which is only slightly sensitive to it.In a typical two-detector compensation scheme, the density measured by the longest spacing detector is corrected by an amount, delta rho, which is a function of the difference between long- and short-spacing densities. The correction is found to depend on the difference between formation and mudcake density multiplied by mudcake thickness. Although there are three unknowns, simple functions are reliable for moderate corrections. Experimental results are often presented in the form of a spine and ribs plot. There are other schemes using, for example, more detectors. Dual detector density logs were introduced in the mid 1960s.
3980azimuthal density, density measurement, photoelectric effect
3981None
3982None
3983--
3984crust
39851.n. [Geology]
3986The thin, outermost shell of the Earth that is typically 5 km to 75 km thick [3 to 46 miles]. The continental crust comprises rocks similar in composition to granite and basalt (i.e., quartz, feldspar, biotite, amphibole and pyroxene) whereas the composition of oceanic crust is basaltic (pyroxene and feldspar). The crust overlies the more dense rock of the mantle, which consists of rocks composed of minerals like pyroxene and olivine, and the iron and nickel core of the Earth. The Mohorovicic discontinuity abruptly separates the crust from the mantle; the velocity of compressional waves is significantly higher below the discontinuity. The crust, mantle and core of the Earth are distinguished from the lithosphere and asthenosphere on the basis of their composition and not their mechanical behavior.
3987diagenesis, flower structure, growth fault, midoceanic ridge, Mohorovicic discontinuity, normal fault, reverse fault, rift, sedimentary basin, structure, subsidence, thrust fault, transpression, transtension
3988None
3989None
3990--
3991casing shoe test
39921.n. [Well Completions]
3993A pressure test applied to the formation directly below a casing shoe. The test is generally conducted soon after drilling resumes after an intermediate casing string has been set. The purpose of the test is to determine the maximum pressures that may be safely applied without the risk of formation breakdown. The results of the test are used to design the mud program for the subsequent hole section and to set safe limits on casing shut-in or choke pressures for well-control purposes.
3994casing string
3995None
3996None
3997--
3998clastic intrusion
39991.n. [Geology]
4000Structures formed by sediment injection. Because they resemble intrusive and extrusive igneous features, much of the vocabulary for describing clastic intrusions, or injectites, 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.
4001seismite
4002None
4003injectite
4004--
4005completion fluid
40061.n. [Well Completions]
4007A solids-free liquid used to "complete" an oil or gas well. This fluid is placed in the well to facilitate final operations prior to initiation of production, such as setting screens production liners, packers, downhole valves or shooting perforations into the producing zone. The fluid is meant to control a well should downhole hardware fail, without damaging the producing formation or completion components. Completion fluids are typically brines (chlorides, bromides and formates), but in theory could be any fluid of proper density and flow characteristics. The fluid should be chemically compatible with the reservoir formation and fluids, and is typically filtered to a high degree to avoid introducing solids to the near-wellbore area. Seldom is a regular drilling fluid suitable for completion operations due to its solids content, pH and ionic composition. Drill-in fluids can, in some cases, be suitable for both purposes.
4008brine, calcium carbonate, carboxymethyl starch, carboxymethyl hydroxyethylcellulose, cesium acetate, cesium formate, drill-in fluid, formate, formation damage, liner, packer
4009None
4010None
4011--
4012crystallization temperature
40131.n. [Well Completions]
4014The temperature at which crystals will appear in a brine solution of a given density as it cools. In preparing oilfield brines, the crystallization temperature can be used to indicate the maximum saturation (density) achievable for a brine solution at a given temperature.
4015brine
4016None
4017None
4018--
4019casing string
40201.n. [Drilling]
4021An assembled length of steel pipe configured to suit a specific wellbore. The sections of pipe are connected and lowered into a wellbore, then cemented in place. The pipe joints are typically approximately 40 ft [12 m] in length, male threaded on each end and connected with short lengths of double-female threaded pipe called couplings. Long casing strings may require higher strength materials on the upper portion of the string to withstand the string load. Lower portions of the string may be assembled with casing of a greater wall thickness to withstand the extreme pressures likely at depth.Casing is run to protect or isolate formations adjacent to the wellbore. The following are the most common reasons for running casing in a well:1) protect fresh-water aquifers (surface casing)2) provide strength for installation of wellhead equipment, including BOPs3) provide pressure integrity so that wellhead equipment, including BOPs, may be closed4) seal off leaky or fractured formations into which drilling fluids are lost 5) seal off low-strength formations so that higher strength (and generally higher pressure) formations may be penetrated safely6) seal off high-pressure zones so that lower pressure formations may be drilled with lower drilling fluid densities7) seal off troublesome formations, such as flowing salt8) comply with regulatory requirements (usually related to one of the factors listed above).
4022bell nipple, blowout preventer, BOP, box, casing, casing shoe, conductor pipe, coupling, displacement, dogleg, float joint, intermediate casing string, joint, liner, mill, pin, reciprocate, surface casing
4023None
4024None
4025--
4026clathrate
40271.n. [Geology]
4028An 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.
4029methane hydrate
4030gas hydrate
4031None
4032--
4033clathrate
40342.n. [Production Testing]
4035Compounds 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.
4036None
4037hydrate
4038None
4039--
4040clathrate
40413.n. [Drilling Fluids]
4042A 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.
4043None
4044gas hydrate
4045None
4046--
4047composite frac tree
40481.n. [Shale Gas, Well Completions, Well Workover and Intervention]
4049A frac tree in which multiple frac valves are contained in a single large body such that the overall height of the frac tree is reduced.
4050None
4051None
4052None
4053--
4054csg
40551.n. [Geology]
4056Abbreviation for coal seam gas. Natural gas, predominantly methane [CH4], generated during coal formation and adsorbed in coal. Natural gas adsorbs to the surfaces of matrix pores within the coal and natural fractures, or cleats, as reservoir pressure increases.Production of natural gas from coal requires decreasing the pore pressure below the coal’s desorption pressure so that methane will desorb from surfaces, diffuse through the coal matrix and become free gas. Because the diffusivity and permeability of the coal matrix are ultralow, coal must have an extensive cleat system to ensure adequate permeability and flow of methane to wellbores at economic production rates.Coal seams are typically saturated with water. Consequently, the coal must be dewatered for efficient gas production. Dewatering reduces the hydrostatic pressure and promotes gas desorption from coal. As dewatering progresses, gas production often increases at a rate governed by how quickly gas desorbs from coal, the permeability of the cleat and the relative permeability of the gas-water system in the cleat. Eventually, the rate and amount of gas desorption decreases as the coal seam is depleted of its gas, and production declines.Coal seams with no water (dry coal) have been discovered and commercially exploited. In these reservoirs, the adsorbed gas is held in place by free gas in the cleats. Consequently, gas production consists of both free gas from the cleat system and desorbed gas from the matrix.
4057unconventional resource
4058coalbed methane, coal bed methane, coal-bed methane, CBM
4059coal seam gas, coal-seam gas
4060--
4061csg
40622.n. [Geophysics]
4063Abbreviation for common source gather. A display of seismictraces that share a source.
4064seismic trace, trace
4065None
4066common source gather
4067--
4068casing swage
40691.n. [Well Completions]
4070A short crossover joint used between two sizes or specifications of casing. A circulating swage is an adapter that enables a temporary circulating line to be rigged to the top of the casing string, allowing circulation of fluids to help properly locate the casing string.
4071None
4072None
4073None
4074--
4075clay
40761.n. [Geology]
4077Fine-grained sediments less than 0.0039 mm in size.
4078argillaceous, colloid, deflocculant, dirty, eolian, hectorite, matrix, polar compound, quebracho, SAPP, sediment, shale, silicate anion, Udden-Wentworth scale
4079None
4080None
4081--
4082clay
40832.n. [Geology]
4084A group of rock-forming, hydrous aluminum silicate minerals that are platy in structure and can form by the alteration of silicate minerals like feldspar and amphibole. Common examples include chlorite, illite, kaolinite, montmorillonite and smectite. Some clays, such as montmorillonite, have the tendency to swell when exposed to water, creating a potential drilling hazard when clay-bearing rock formations are exposed to water-base fluids during drilling, possibly reducing the permeability of a good reservoir rock. Some clays are used in drilling fluids to form an impermeable mudcake to isolate a formation from the invasion of drilling fluid.The structural difference among clays (smectite, kaolinite, chlorite, illite) determines the surface area exposed to reservoir fluids or stimulating fluids. Generally, higher surface area indicates higher reactivity. However, not all the clay present in a rock is reactive. Clays can be found in pore spaces, as part of the matrix or as grain-cementing material. Authigenic clays, which grow in the pores from minerals in the connate water, can be pore-filling or pore-lining. These clays have considerable surface area exposed in the pore and can be reactive, while detrital clays that are part of the matrix are usually less reactive. Additionally, clays as cementing, or grain-binding, materials may react with water or acid to disaggregate the formation if they are not protected by quartz overgrowths.The most common clays that create clay problems are kaolinite, smectite, illite and chlorite. These minerals can be treated using hydrofluoric acid [HF].
4085argillaceous, bentonite, connate water, dirty, effective porosity, eolian, glauconite, limestone, mica, sedimentary, stimulation fluid, stylolite
4086None
4087None
4088--
4089clay
40903.n. [Drilling Fluids]
4091A large family of complex minerals containing the elements magnesium, aluminum, silicon and oxygen (magnesium, aluminum silicates) combined in a sheet-like structure. Clays are mined from surface pits as relatively pure deposits and used for bricks, pottery, foundry molds and in drilling fluids among other uses. Clays, as claystones, shales and intermixed with sands and sandstones make up the largest percentage of minerals drilled while exploring for oil and gas. Sodium bentonite is a useful additive for increasing the density of drilling muds, but other clay types are considered contaminants to be avoided and removed. Individual clay platelets can be viewed only with an electron microscope. Crystal structures are also determined by X-ray diffraction (XRD). The atomic structure of the clay group of layered silicate minerals varies from two-layer to three-layer or four-layer (mixed-layer) structures. One of the structural layers is a plane of silicon dioxide tetrahedra (silicon at the center and oxygen at all four corners of the tetrahedron). The other structural layer is a plane of aluminum hydroxide octahedra (aluminum at the center and hydroxides at all six corners). The tetrahedral and octahedral layers fit one on top of the other, with oxygen atoms being shared as oxide and hydroxide groups.
4092aggregation, anion, attapulgite, cation-exchange capacity, clay-water interaction, colloidal solids, conventional mud, encapsulation, gel, hectorite, hygroscopic, inhibitive mud, ion exchange, kaolinite, montmorillonite, octahedral layer, organophilic clay, polar compound, potassium ion, quaternary amine, sepiolite, shale, silica layer, smectite clay
4093None
4094None
4095--
4096composite log
40971.n. [Formation Evaluation]
4098A single log created by splicing together two logs of the same type run at different times in the well; or by splicing two different types of log run at the same time. For example, it is common practice to splice all the basic logs run over different depth intervals in a well to obtain a single composite record.
4099correlation log, detail log
4100None
4101None
4102--
4103ct
41041.n. [Drilling]
4105Another 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.
4106coiled tubing drilling, packer
4107coiled tubing, endless tubing, reeled tubing
4108None
4109--
4110ct
41112.adj. [Well Workover and Intervention]
4112A 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.
4113None
4114None
4115coiled tubing, endless tubing, reeled tubing
4116--
4117casing valve
41181.n. [Well Completions]
4119A valve installed in the wellhead assembly to provide access to the casing annulus of non-producing casings.
4120None
4121None
4122None
4123--
4124clay extender
41251.n. [Drilling Fluids]
4126A class of polymers added to a drilling-grade clay mineral during grinding, or added directly into a clay-based mud system, to enhance the clay's rheological performance. In concept, clay-extender polymers achieve the type of rheology needed for fast drilling with fewer colloidal solids and lower viscosity at high shear rate (at the bit). This is the concept of a "low-solids, nondispersed mud" system. Extenders are usually long-chain anionic or nonionic polymers that link clay platelets together in large networks. Anionic polymers are highly effective but can be precipitated by hardness ions. Nonionic polymers are less effective but also much less sensitive to hardness ions. Excessively long, linear polymers may break up under mechanical shearing. Either by precipitation or breakup, extender polymers can quickly become ineffective if poorly chosen and used improperly. A drilling-grade clay that has no extender is that which meets the standard for API nontreated bentonite. API bentonite and OCMA-grade API bentonite usually contain extender polymers.
4127acrylamide polymer, acrylamide-acrylate polymer, acrylate polymer, beneficiation, clear-water drilling, hardness ion, low-solids mud, peptize, peptized clay, PHPA mud, polar compound, polymer
4128None
4129None
4130--
4131compositional fluid analysis
41321.n. [Heavy Oil]
4133Any of a variety of analytical techniques carried out to determine the composition of a crude oil by breaking it down into basic chemical components. The hydrocarbon components are usually identified by carbon number fractions: C1, C2, C3,etc. up to Cn, where the limiting carbon number, n, is defined by the particular analytical technique. These analytical techniques include, but are not limited to, gas or liquid chromatography, cryogenic and flash distillations, true boiling-point distillations, structural fluid characterizations such as polynuclear aromatic hydrocarbon analysis, SARA analysis, sonic testing and other crude oil assay methods. Other nonhydrocarbon components can also be identified, such as nitrogen, heavy metals, sulfur and salts.
4134None
4135None
4136None
4137--
4138cubic packing
41391.n. [Geology]
4140The arrangement in space of uniform spheres (atoms and molecules in mineral crystals, or grains in clastic sedimentary rocks) that results in a cubic material structure. Cubic packing is mechanically unstable, but it is the most porous packing arrangement, with about 47% porosity in the ideal situation. Most sediments are not uniform spheres of the same size, nor can they be arranged in a cubic structure naturally, so most sediments have much less than 47% porosity.
4141clastic sediment, porosity, rhombohedral packing, sediment, sorting
4142None
4143None
4144--
4145casing inspection log
41461.n. [Production Logging]
4147An in situ record of casing thickness and integrity, to determine whether and to what extent the casing has undergone corrosion. The term refers to an individual measurement, or a combination of measurements using acoustic, electrical and mechanical techniques, to evaluate the casing thickness and other parameters. The log is usually presented with the basic measurements and an estimate of metal loss. It was first introduced in the early 1960s. Today the terms casing-evaluation log and pipe-inspection log are used synonymously.
4148casing-potential profile, eddy-current measurement
4149None
4150None
4151--
4152clay stabilizer
41531.n. [Well Workover and Intervention]
4154A chemical additive used in stimulation treatments to prevent the migration or swelling of clay particles in reaction to water-base fluid. Without adequate protection, some water-base fluids can affect the electrical charge of naturally occurring clay platelets in the formation. Modifying the charge causes the platelets to swell or migrate in the flowing fluid and, once these are dispersed, it is likely that some clay plugging of the formation matrix will occur. Clay stabilizers act to retain the clay platelets in position by controlling the charge and electrolytic characteristics of the treatment fluid.
4155None
4156None
4157None
4158--
4159compressibility
41601.n. [Formation Evaluation]
4161The ratio of the percent change in volume to the change in pressure applied to a fluid or rock.
4162None
4163None
4164None
4165--
4166compressibility
41672.n. [Well Testing]
4168The 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).
4169None
4170fluid compressibility
4171None
4172--
4173curve matching
41741.n. [Geophysics]
4175The graphical comparison of well-understood data sets, called type curves, to another data set. If a certain type curve closely corresponds to a data set, then an interpretation of similarity can be made, although, as Sheriff (1991) points out, there might be other type curves that also match the data of interest. Curve matching differs from curve fitting in that curve fitting involves theoretical models rather than actual examples.
4176curve fitting, type curves
4177None
4178None
4179--
4180casing potential profile
41811.n. [Production Logging]
4182An in situ log of the electrical potential on the inner wall of a casing. The log is used to identify intervals that are susceptible to corrosion. A negative slope in the profile indicates a zone in which current is leaving the casing and therefore acting as an anode. Such zones are susceptible to corrosion. The log was first introduced in the early 1960s. Modern logs are recorded with the tool stationary, and measure the potential difference and casing resistance between several pairs of sensors pushed against the casing wall, and between sensors and surface.The log is usually represented with casing resistance and casing axial current. Sharp increases in casing resistance can indicate corroded zones or even holes in the casing. Decreasing axial current with depth indicates a corroding region.
4183casing-inspection log
4184None
4185None
4186--
4187clay water interaction
41881.n. [Drilling Fluids]
4189An all-inclusive term to describe various progressive interactions between clay minerals and water. In the dry state, clay packets exist in face-to-face stacks like a deck of playing cards, but clay packets begin to change when exposed to water. Five descriptive terms describe the progressive interactions that can occur in a clay-water system, such as a water mud.1) Hydration occurs as clay packets absorb water and swell.2) Dispersion (or disaggregation) causes clay platelets to break apart and disperse into the water due to loss of attractive forces as water forces the platelets farther apart.3) Flocculation begins when mechanical shearing stops and platelets previously dispersed come together due to the attractive force of surface charges on the platelets.4) Deflocculation, the opposite effect, occurs by addition of chemical deflocculant to flocculated mud; the positive edge charges are covered and attraction forces are greatly reduced.5) Aggregation, a result of ionic or thermal conditions, alters the hydrational layer around clay platelets, removes the deflocculant from positive edge charges and allows platelets to assume a face-to-face structure.
4190None
4191None
4192clay-water interaction
4193--
4194compressor
41951.n. [Production Facilities]
4196A device that raises the pressure of air or natural gas. A compressor normally uses positive displacement to compress the gas to higher pressures so that the gas can flow into pipelines and other facilities.
4197None
4198None
4199None
4200--
4201cushion
42021.n. [Well Testing]
4203A fluid column (usually water or nitrogen) put in the drillstem to provide the desired backpressure at the start of a drillstem test. The cushion usually serves to limit the differential pressure across the test string and packer to avoid flow below the bubblepoint pressure (in which case water is the usual cushion) or to enable a depleted reservoir to flow (nitrogen is the likely cushion).
4204differential pressure, drillstem test
4205None
4206None
4207--
4208cat line
42091.n. [Drilling]
4210A relatively thin cable used with other equipment to move small rig and drillstring components and to provide tension on the tongs for tightening or loosening threaded connections.
4211None
4212None
4213None
4214--
4215clay water interaction
42161.n. [Drilling Fluids]
4217An all-inclusive term to describe various progressive interactions between clay minerals and water. In the dry state, clay packets exist in face-to-face stacks like a deck of playing cards, but clay packets begin to change when exposed to water. Five descriptive terms describe the progressive interactions that can occur in a clay-water system, such as a water mud.1) Hydration occurs as clay packets absorb water and swell.2) Dispersion (or disaggregation) causes clay platelets to break apart and disperse into the water due to loss of attractive forces as water forces the platelets farther apart.3) Flocculation begins when mechanical shearing stops and platelets previously dispersed come together due to the attractive force of surface charges on the platelets.4) Deflocculation, the opposite effect, occurs by addition of chemical deflocculant to flocculated mud; the positive edge charges are covered and attraction forces are greatly reduced.5) Aggregation, a result of ionic or thermal conditions, alters the hydrational layer around clay platelets, removes the deflocculant from positive edge charges and allows platelets to assume a face-to-face structure.
4218acrylamide-acrylate polymer, Bingham plastic model, calcium contamination, calcium mud, capillary-suction-time test, closed mud system, colloid, colloidal solids, dewatering, dispersant, encapsulation, gel strength, gyp mud, hydrophilic, hygroscopic, inhibitive mud, ion exchange, kaolinite, lignosulfonate, lime mud, low-yield clay, make-up water, montmorillonite, native clay, peptized clay, peptizing agent, phosphate salt, PHPA mud, potassium mud, prehydrated bentonite, prehydration, rheology, smectite clay, sulfonated polystyrene-maleic anhydride copolymer, tannic acid, tannin, vinyl acetate-maleic anhydride copolymer, water clarification
4219None
4220None
4221--
4222compressor plant
42231.n. [Production Facilities]
4224A facility consisting of many compressors, auxiliary treatment equipment and pipeline installations to pump natural gas under pressure over long distances. A compressor plant is also called a compressor station. Several compressor stations can be used to repressurize gas in large interstate gas pipelines or to link offshore gas fields to their final terminals.
4225compressor
4226None
4227None
4228--
4229cut
42301.n. [Production Logging]
4231The fraction of the total flow rate produced from a well that is due to a particular fluid, for example the water cut in the case of water. The cut is normally quoted at standard surface conditions.
4232holdup, water cut
4233None
4234None
4235--
4236cataclasite
42371.n. [Geology]
4238A type of metamorphic rock with shearing and granulation of minerals caused by high mechanical stress during faulting or dynamic metamorphism, typically during episodes of plate tectonic activity.
4239fault, plate tectonics
4240None
4241None
4242--
4243clean
42441.adj. [Geology]
4245Pertaining to a sedimentary rock, such as sandstone or limestone, that contains only minimal amounts of clay minerals. Clean reservoir rocks typically have better porosity and permeability than dirty rocks whose pores are clogged with fine clay particles. Clean and dirty are qualitative, descriptive terms.
4246eolian, limestone, sandstone, sedimentary
4247None
4248Antonyms:dirty
4249--
4250computed tomography
42511.n. [Formation Evaluation]
4252A technique for imaging a core by scanning it with a highly focused source of X-rays and recording the attenuated X-rays on the other side. The source and detector are rotated and moved along the core. The measurements are combined mathematically to give a full core image.
4253fluoroscopy, X-radiography
4254None
4255None
4256--
4257cut and thread fishing technique
42581.n. [Drilling]
4259A method for recovering wireline stuck in a wellbore. In cut-and-thread operations, the wireline is gripped securely with a special tool and cut at the surface. The cut end is threaded through a stand of drillpipe. While the pipe hangs in the wellbore, the wireline is threaded through another stand of drillpipe, which is screwed onto the stand in the wellbore. The process is repeated until the stuck wireline is recovered. This technique, while dangerous and time-consuming, is known to improve greatly the chances of full recovery of the wireline and the tool at its end in the shortest overall time compared with trying to grab the wireline in the openhole with fishing tools.
4260drillpipe, fishing tool, stand
4261None
4262None
4263--
4264cataclastic
42651.adj. [Geology]
4266Pertaining to a type of metamorphic rock with shearing and granulation of minerals caused by high mechanical stress during faulting or dynamic metamorphism, typically during episodes of plate tectonic activity.
4267fault, plate tectonics
4268None
4269None
4270--
4271clean out
42721.vb. [Well Workover and Intervention]
4273To remove wellbore-fill material such assand,scaleor organic materials, and other debris from the wellbore. Many reservoirs produce some sand orfinesthat may not be carried to surface in the produced fluid. Accumulations of fill material may eventually increase in concentration within the lower wellbore, possibly restrictingproduction. Cleanouts usingcoiled tubing,snubbingor hydraulicworkover techniques are performed routinely.
4274None
4275None
4276None
4277--
4278conceptual model
42791.n. [Reservoir Characterization]
4280A hypothetical model characterizing strata, generally strata deposited in one or a related set of environments. Conceptual models usually incorporate rules about possible geometries and successions of facies that can be included in a geological scenario. These often provide limitations to the interpretation of a given reservoir. Conceptual models commonly incorporate sequence stratigraphic concepts such as facies tracts, unconformities, flooding surfaces, erosional surfaces and parasequences. Conceptual models are often used in conjunction with geostatistical and classical technologies for reservoir characterization.
4281flooding surface, geostatistics, parasequence, unconformity
4282None
4283None
4284--
4285cut oil
42861.n. [Production Facilities]
4287A crude oil that contains water, normally in the form of an emulsion. The emulsion must be treated inside heaters using chemicals, which will break the mixture into its individual components (water and crude oil).
4288crude oil, heater, roll a tank
4289None
4290None
4291--
4292cathodic protection
42931.n. [Enhanced Oil Recovery]
4294A technique used to minimize the rate of corrosion of a structure. Cathodic protection does not eliminate corrosion, it transfers corrosion from the structure under protection to a known location where artificial anodes (plates or metal bars) are placed and could be replaced easily. Cathodic protection is used for floating vessels, platforms, storage tanks and pipelines The cathodic protection principle is based on the electrochemical nature of the corrosion phenomena; the anodic area corrodes (current is discharged) and the cathodic area does not corrode (current is received). Cathodic protection overrides the naturally occurring anodic areas inside a structure, thus turning the structure under protection completely cathodic, which means it receives current from the surrounding electrolyte (for example, soils, water) and does not corrode. Cathodic protection is achieved by passing enough direct current electricity from an external source (a more powerful anode), which could be a galvanic anode or an impressed current anode.
4295corrosion, corrosion control, galvanic anodes, impressed current anodes
4296None
4297None
4298--
4299cleanout
43001.n. [Well Workover and Intervention]
4301The removal of wellbore-fill material, such as sand, scale or organic materials, and other debris from the wellbore. Many reservoirs produce some sand or fines that may not be carried to surface in the produced fluid. Accumulations of fill material may eventually increase in concentration within the lower wellbore, possibly restricting production. Cleanouts using coiled tubing, snubbing or hydraulic workover techniques are performed routinely.
4302produced fluid
4303None
4304None
4305--
4306concession
43071.n. [Oil and Gas Business]
4308A grant extended by a government to permit a company to explore for and produce oil, gas or mineral resources within a strictly defined geographic area, typically beneath government-owned lands or lands in which the government owns the rights to produce oil, gas or minerals. The grant is usually awarded to a company in consideration for some type of bonus or license fee and royalty or production sharing provided to the host government for a specified period of time.
4309None
4310None
4311None
4312--
4313concession
43142.n. [Oil and Gas Business]
4315The geographic area in which the government allows a company to operate.
4316None
4317None
4318None
4319--
4320cut point
43211.n. [Drilling Fluids]
4322The particle size that has a specified chance of being removed by an item of solids control equipment. Most commonly, D10, D50 and D90 cut points are specified corresponding to 10, 50 and 90% chances of removal, respectively. Taken together, they approximate the separation curve. If the percent is not specified, it is normally taken to be the D50 value. For example, if the D50 of a shaker screen is 100 microns, then a particle of this size has an equal chance of being removed or staying in the system. Larger particles are more likely to be removed and smaller ones more likely to be retained in the underflow.
4323crude oil
4324None
4325None
4326--
4327cation exchange capacity
43281.n. [Formation Evaluation]
4329The quantity of positively charged ions (cations) that a clay mineral or similar material can accommodate on its negatively charged surface, expressed as milli-ion equivalent per 100 g, or more commonly as milliequivalent (meq) per 100 g. Clays are aluminosilicates in which some of the aluminum and silicon ions have been replaced by elements with different valence, or charge. For example, aluminum (Al+++) may be replaced by iron (Fe++) or magnesium (Mg++), leading to a net negative charge. This charge attracts cations when the clay is immersed in an electrolyte such as salty water and causes an electrical double layer. The cation-exchange capacity (CEC) is often expressed in terms of its contribution per unit pore volume, Qv.In formation evaluation, it is the contribution of cation-exchange sites to the formation electrical properties that is important. Various techniques are used to measure CEC in the laboratory, such as wet chemistry, multiple salinity and membrane potential. Wet chemistry methods, such as conductometric titration, usually involve destruction or alteration of the rock. Although quicker and simpler to perform, they are less representative of electrical properties in situ. The multiple salinity and membrane potential methods are more direct measurements of the effect of CEC on formation resistivity and spontaneous potential.
4330None
4331None
4332cation-exchange capacity, CEC
4333--
4334cation exchange capacity
43352.n. [Drilling Fluids]
4336Quantity of positively charged ions (cations) that a clay mineral (or similar material) can accommodate on its negative charged surface, expressed as milliequivalents per 100 grams. CEC of solids in drilling muds is measured on a whole mud sample by a methylene blue capacity (MBC) test, which is typically performed to specifications established by API. CEC for a mud sample is reported as MBC, methylene blue test (MBT) or bentonite equivalent, lbm/bbl or kg/m3.
4337None
4338base exchange
4339cation-exchange capacity, CEC
4340--
4341cleanup
43421.n. [Well Completions]
4343A period of controlled production, generally following a stimulation treatment, during which time treatment fluids return from the reservoir formation. Depending on the treatment, the cleanup period can be relatively short and uncomplicated. However, following more complex treatments such as gravel pack or hydraulic fracturing, the cleanup process should be conducted carefully to avoid jeopardizing the long-term efficiency of the treatment.
4344treatment fluid
4345None
4346None
4347--
4348condensate
43491.n. [Geology]
4350A low-density, high-API gravity liquid hydrocarbon phase that generally occurs in association with natural gas. Its presence as a liquid phase depends on temperature and pressure conditions in the reservoir allowing condensation of liquid from vapor. The production of condensate reservoirs can be complicated because of the pressure sensitivity of some condensates: During production, there is a risk of the condensate changing from gas to liquid if the reservoir pressure drops below the dew point during production. Reservoir pressure can be maintained by fluid injection if gas production is preferable to liquid production. Gas produced in association with condensate is called wet gas. The API gravity of condensate is typically 50 degrees to 120 degrees.
4351dry gas, field, fluid contact, retrograde condensation
4352None
4353None
4354--
4355condensate
43562.n. [Well Testing]
4357Liquid phase occurring in gas condensate reservoirs when the pressure is below the dewpoint pressure.
4358None
4359None
4360None
4361--
4362condensate
43633.n. [Production Testing, Enhanced Oil Recovery]
4364A natural gas liquid with a low vapor pressure compared with natural gasoline and liquefied petroleum gas. Condensate is mainly composed of propane, butane, pentane and heavier hydrocarbon fractions. The condensate is not only generated into the reservoir, it is also formed when liquid drops out, or condenses, from a gas stream in pipelines or surface facilities.
4365natural gas liquids
4366None
4367None
4368--
4369cut and thread fishing technique
43701.n. [Drilling]
4371A method for recovering wireline stuck in a wellbore. In cut-and-thread operations, the wireline is gripped securely with a special tool and cut at the surface. The cut end is threaded through a stand of drillpipe. While the pipe hangs in the wellbore, the wireline is threaded through another stand of drillpipe, which is screwed onto the stand in the wellbore. The process is repeated until the stuck wireline is recovered. This technique, while dangerous and time-consuming, is known to improve greatly the chances of full recovery of the wireline and the tool at its end in the shortest overall time compared with trying to grab the wireline in the openhole with fishing tools.
4372drillpipe, fishing tool, stand
4373None
4374None
4375--
4376cation exchange capacity
43771.n. [Formation Evaluation]
4378The quantity of positively charged ions (cations) that a clay mineral or similar material can accommodate on its negatively charged surface, expressed as milli-ion equivalent per 100 g, or more commonly as milliequivalent (meq) per 100 g. Clays are aluminosilicates in which some of the aluminum and silicon ions have been replaced by elements with different valence, or charge. For example, aluminum (Al+++) may be replaced by iron (Fe++) or magnesium (Mg++), leading to a net negative charge. This charge attracts cations when the clay is immersed in an electrolyte such as salty water and causes an electrical double layer. The cation-exchange capacity (CEC) is often expressed in terms of its contribution per unit pore volume, Qv.In formation evaluation, it is the contribution of cation-exchange sites to the formation electrical properties that is important. Various techniques are used to measure CEC in the laboratory, such as wet chemistry, multiple salinity and membrane potential. Wet chemistry methods, such as conductometric titration, usually involve destruction or alteration of the rock. Although quicker and simpler to perform, they are less representative of electrical properties in situ. The multiple salinity and membrane potential methods are more direct measurements of the effect of CEC on formation resistivity and spontaneous potential.
4379clay-bound water, dual water
4380None
4381None
4382--
4383cation exchange capacity
43842.n. [Drilling Fluids]
4385Quantity of positively charged ions (cations) that a clay mineral (or similar material) can accommodate on its negative charged surface, expressed as milliequivalents per 100 grams. CEC of solids in drilling muds is measured on a whole mud sample by a methylene blue capacity (MBC) test, which is typically performed to specifications established by API. CEC for a mud sample is reported as MBC, methylene blue test (MBT) or bentonite equivalent, lbm/bbl or kg/m3.
4386anion, bentonite, cation, equivalent weight, ion exchange, methylene blue dye, mixed-metal hydroxide, montmorillonite, peptized clay, peptizing agent, shale
4387base exchange
4388CEC
4389--
4390clear brine
43911.n. [Geology]
4392Water containing more dissolved inorganic salt than typical seawater.
4393cesium formate, formation water, fresh water
4394brine
4395None
4396--
4397clear brine
43982.n. [Drilling]
4399Saline liquid usually used in completion operations and, increasingly, when penetrating a pay zone. Brines are preferred because they have higher densities than fresh water but lack solid particles that might damage producible formations. Classes of brines include chloride brines (calcium and sodium), bromides and formates.
4400completion fluid, producing formation
4401None
4402None
4403--
4404clear brine
44053.n. [Drilling Fluids]
4406A general term that refers to various salts andsaltmixtures dissolved in an aqueous solution. Brine can be used more strictly, however, to refer to solutions of sodium chloride. We prefer to use brine as a general term. Clear brines are salt solutions that have few or nosuspended solids.
4407balanced-activity oil mud, bromide brine, calcium bromide, drill-in fluid, formate, guar gum, hydrometer, synthetic/brine ratio, undersaturated fluid
4408None
4409None
4410--
4411clear brine
44124.n. [Well Completions]
4413A water-based solution of inorganic salts used as a well-control fluid during the completion and workover phases of well operations. Brines are solids free, containing no particles that might plug or damage a producing formation. In addition, the salts in brine can inhibit undesirable formation reactions such as clay swelling. Brines are typically formulated and prepared for specific conditions, with a range of salts available to achieve densities ranging from 8.4 to over 20 lbm/gal (ppg) [1.0 to 2.4 g/cmo]. Common salts used in the preparation of simple brine systems include sodium chloride, calcium chloride and potassium chloride. More complex brine systems may contain zinc, bromide or iodine salts. These brines are generally corrosive and costly.
4414cesium formate, producing formation
4415None
4416None
4417--
4418condensate liquids
44191.n. [Production Testing]
4420Hydrocarbons that are in the gaseous phase at reservoir conditions but condense into liquid as they travel up the wellbore and reach separator conditions. Condensate liquids are sometimes called distillate.
4421None
4422None
4423None
4424--
4425cutt point
44261.n. [Drilling Fluids]
4427The spherical diameter corresponding to the ellipsoidal volume distribution of the screen opening sizes as measured by image analysis techniques. Named after Al Cutt of Amoco who developed the technique. Not to be confused with cut point.Reference:Cutt AR: "Shaker Screen Characterization Through Image Analysis," paper SPE 22570, presented at the 66th SPE Annual Technical Conference and Exhibition, Dallas, Texas, USA, October 6-9, 1991.
4428None
4429None
4430None
4431--
4432catline
44331.n. [Drilling]
4434A relatively thin cable used with other equipment to move small rig and drillstring components and to provide tension on the tongs for tightening or loosening threaded connections.
4435cat line
4436None
4437None
4438--
4439clear water drilling
44401.n. [Drilling Fluids]
4441Drilling operations using a water-base drilling fluid that contains few solids. Clear-water drilling is done in "hard rocks" in which density and fluid loss are not critical. Rapid drilling rate is the incentive for using a solids-free mud. Fluid returned to the surface must be screened and processed by hydrocyclones and centrifuges to remove larger solids. Colloidal solids can be agglomerated by adding polymers and removing the aggregates. Polymers such as acrylates, acrylamides and partially-hydrolyzed polyacrylamides are used. They are added at the flowline as mud exits the well or added in pits downstream from the flowline.
4442None
4443None
4444clear-water drilling
4445--
4446conductance
44471.n. [Geophysics]
4448The product of conductivity and thickness, typically measured in units of siemens (S). In the inversion of electrical and electromagnetic measurements, the conductance of a layer or zone is usually much better determined than either the conductivity or thickness individually.
4449None
4450None
4451None
4452--
4453conductance
44542.n. [Geophysics]
4455The reciprocal of resistance in a direct current circuit, measured in siemens (formerly mhos). In an alternating current circuit, conductance is the resistance divided by the square of impedance, also measured in siemens.
4456None
4457None
4458None
4459--
4460cuttings
44611.n. [Drilling]
4462Small pieces of rock that break away due to the action of the bit teeth. Cuttings are screened out of the liquid mud system at the shale shakers and are monitored for composition, size, shape, color, texture, hydrocarbon content and other properties by the mud engineer, the mud logger and other on-site personnel. The mud logger usually captures samples of cuttings for subsequent analysis and archiving.
4463bridge, cable-tool drilling, circulate out, eccentricity, mechanical sticking, mud engineer, overbalance, pack off, pill, reciprocate, reverse circulation, rotary drilling, settling pit, shale shaker
4464None
4465None
4466--
4467cuttings
44682.n. [Drilling Fluids]
4469Rock pieces dislodged by the drill bit as it cuts rock in the hole. Cuttings are distinct from cavings, rock debris that spalls as a result of wellbore instability. Visual inspection of rock at the shale shaker usually distinguishes cuttings from cavings.
4470attapulgite, breaker, cavings, flowline mud sample, lag time, LC50, pour point, shale shaker
4471None
4472None
4473--
4474catwalk
44751.n. [Drilling]
4476A long, rectangular platform about 3 ft [0.9 m] high, usually made of steel and located perpendicular to the vee-door at the bottom of the slide. This platform is used as a staging area for rig and drillstring tools, components that are about to be picked up and run, or components that have been run and are being laid down. A catwalk is also the functionally similar staging area, especially on offshore drilling rigs, that may not be a separate or raised structure.
4477pipe rack
4478None
4479None
4480--
4481clear water drilling
44821.n. [Drilling Fluids]
4483Drilling operations using a water-base drilling fluid that contains few solids. Clear-water drilling is done in "hard rocks" in which density and fluid loss are not critical. Rapid drilling rate is the incentive for using a solids-free mud. Fluid returned to the surface must be screened and processed by hydrocyclones and centrifuges to remove larger solids. Colloidal solids can be agglomerated by adding polymers and removing the aggregates. Polymers such as acrylates, acrylamides and partially-hydrolyzed polyacrylamides are used. They are added at the flowline as mud exits the well or added in pits downstream from the flowline.
4484acrylamide polymer, acrylamide-acrylate polymer, acrylate polymer, centrifuge, clay extender, closed mud system, drilling rate, hydrocyclone, PHPA mud, wastewater cleanup, water clarification
4485None
4486None
4487--
4488conductive invasion
44891.n. [Formation Evaluation]
4490A situation in which the resistivity of the flushed zone is less than the resistivity of the undisturbed zone. Such a setting generally favors the use of electrode resistivity devices (laterologs, ring resistivity), which respond to resistivity, rather than induction and propagation resistivity devices, which respond to conductivity.
4491array laterolog, azimuthal laterolog, true resistivity
4492None
4493Antonyms:resistive invasion
4494--
4495cuttings lifting
44961.n. [Drilling Fluids]
4497Transportof rockfragments out of a wellbore bya circulatingdrilling fluid. Carrying capacity is an essential function of a drilling fluid, synonymous with hole-cleaning capacity and cuttings lifting capacity. Carrying capacity is determined principally by theannular velocity, hole angle andflow profileof the drilling fluid, but is also affected bymud weight, cuttings size and pipe position and movement.
4498Brookfield viscometer, cuttings, rheology, rheology modifier, XC polymer
4499carrying capacity, hole cleaning
4500None
4501--
4502cave effect
45031.n. [Formation Evaluation]
4504The effect of a sharp change in the borehole diameter, such as that caused by a cave or rugose hole, on an induction log. In smooth boreholes of constant diameter, the effect of the borehole is well understood and can be corrected for. However, a sharp increase in diameter over a small depth interval can induce signals on one coil in the array and not in others. This signal is not handled by the normal borehole correction and may result in a spike on the log. The spike usually is significant only when the resistivity is high and the contrast between formation and borehole resistivity is very large. The spike also depends on the design of the array or the processing.
4505array induction
4506None
4507None
4508--
4509closed in well
45101.n. [Well Testing]
4511A well with a valve closed to halt production. Wells are often closed in for a period of time to allow stabilization prior to beginning a drawdown-buildup test sequence.
4512buildup test, drawdown test
4513None
4514None
4515--
4516conductive rock matrix model
45171.n. [Formation Evaluation]
4518A model, or set of equations, for the resistivity response of formations with conductive minerals, such as shaly sands. The model is used to analyze core data and to calculate water saturation from resistivity and other logs. The conductive rock matrix model (CRMM) was proposed by W. Givens. The model treats the rock as two components in parallel: a conductive pore network with fluid that is free to move, and the remainder of the rock, which may have conductive minerals or immobile but conductive water. The model is not concerned with the origin of this conductivity, but gives it a resistivity, Rm. The two components are in parallel as follows:	1 / Rt = 1 / Rp + 1 / Rmwhere Rp is the resistance of the free-fluid pore network and can be expressed in terms of the porosity and formation water resistivity by the Archie equation. The model was developed from core data, and can explain the observed variations of the porosity exponent with porosity and the saturation exponent with water saturation in shaly sands. For log analysis Rm needs to be related to parameters that can be measured by logs.Reference:Givens WW: Formation Factor, Resistivity Index and Related Equations Based upon a Conductive rock Matrix Model (CRMM), Transactions of the SPWLA 27th Annual Logging Symposium, Houston, Texas, USA, June 9-13, 1986, paper P.
4519cation-exchange capacity, resistivity log, saturation equation, saturation exponent
4520None
4521None
4522--
4523cycle time
45241.n. [Drilling Fluids]
4525The elapsed time for mud to circulate from the suction pit, down the wellbore and back to surface. Cycle time allows the mud engineer to catch "in" and "out" samples that accurately represent the same element of mud in a circulating system. Cycle time is calculated from the estimated hole volume and pump rate and can be checked by using tracers such as carbide or rice granules.
4526lag time, mud engineer, mud tracer, mud-in sample, mud-out sample, suction pit
4527circulation time
4528None
4529--
4530cavings
45311.n. [Drilling Fluids]
4532Pieces of rock that came from the wellbore but that were not removed directly by the action of the drill bit. Cavings can be splinters, shards, chunks and various shapes of rock, usually spalling from shale sections that have become unstable. The shape of the caving can indicate why the rock failure occurred. The term is typically used in the plural form.
4533cuttings
4534None
4535None
4536--
4537closed mud system
45381.n. [Drilling Fluids]
4539A mud and solids-control system in which the only discarded waste is moist, drilled-up rock materials. Such systems are used for drilling wells in environmentally sensitive areas. No reserve-mud pit is used in a truly closed mud system. Mud is continually processed primarily by mechanical means, such as screening, hydrocycloning and centrifuging to remove solids initially. A second stage to remove colloidal solids is by wastewater cleanup techniques.
4540alum, centrifuge, clay-water interaction, clear-water drilling, dewatering, drill solids, hydrocyclone, vinyl acetate-maleic anhydride copolymer, water clarification
4541None
4542None
4543--
4544conductometric titration
45451.n. [Formation Evaluation]
4546A technique for estimating the cation-exchange capacity of a sample by measuring the conductivity of the sample during titration. The technique includes crushing a core sample and mixing it for some time in a solution like barium acetate, during which all the cation-exchange sites are replaced by barium (Ba++) ions. The solution is then titrated with another solution, such as MgSO4, while observing the change in conductivity as the magnesium (Mg++) ions replace the Ba++ ions. For several reasons, but mainly because the sample must be crushed, the measured cation-exchange capacity may differ from that which affects the in situ electrical properties of the rock.
4547multiple salinity
4548None
4549None
4550--
4551cyclic steam injection
45521.n. [Heavy Oil]
4553A method of thermal recovery in which a well is injected with steam and then subsequently put back on production. A cyclic steam-injection process includes three stages. The first stage is injection, during which a slug of steam is introduced into the reservoir. The second stage, or soak phase, requires that the well be shut in for several days to allow uniform heat distribution to thin the oil. Finally, during the third stage, the thinned oil is produced through the same well. The cycle is repeated as long as oil production is profitable. Cyclic steam injection is used extensively in heavy-oil reservoirs, tar sands, and in some cases to improve injectivity prior to steamflood or in situ combustion operations.Cyclic steam injection is also called steam soak or the huff `n puff (slang) method.
4554enhanced oil recovery, hot waterflooding, in-situ combustion, steamflood, tar sand
4555None
4556huff and puff, steam soak
4557--
4558cavitation
45591.n. [Geophysics]
4560An implosion produced by locally low pressure, such as the collapse of a gas bubble in liquid (the energy of which is used as the source of seismic energy from air guns).
4561air gun, bubble effect, water gun
4562None
4563None
4564--
4565cavitation
45662.n. [Production]
4567The rapid formation and collapse of vapor pockets in a flowing liquid in localized regions of very low pressure. It is often a cause of erosive damage to pumps, throttling type valves and the piping itself. It can cause excessive noise.
4568None
4569None
4570None
4571--
4572closed in well
45731.n. [Well Testing]
4574A well with a valve closed to halt production. Wells are often closed in for a period of time to allow stabilization prior to beginning a drawdown-buildup test sequence.
4575buildup test, drawdown test
4576None
4577None
4578--
4579conductor pipe
45801.n. [Drilling]
4581The casing string that is usually put into the well first, particularly on land wells, to prevent the sides of the hole from caving into the wellbore. This casing, sometimes called drive pipe, is generally a short length and is sometimes driven into the ground. Conductor pipe is run because the shallow section of most wells onshore is drilled in unconsolidated sediment or soil rather than consolidated strata typically encountered deeper. Offshore, the drive pipe or structural casing may be installed prior to the conductor for similar reasons.
4582None
4583None
4584None
4585--
4586conductor pipe
45872.n. [Well Completions]
4588A short string of large-diameter casing set to support the surface formations. The conductor pipe is typically set soon after drilling has commenced since the unconsolidated shallow formations can quickly wash out or cave in. Where loose surface soil exists, the conductor pipe may be driven into place before the drilling commences.
4589None
4590None
4591None
4592--
4593cycling plant
45941.n. [Production Facilities]
4595An oilfield installation used when producing from a gas-condensate reservoir. In a cycling plant, the liquids are extracted from the natural gas and then the remaining dry gas is compressed and returned to the producing formation to maintain reservoir pressure. This process increases the ultimate recovery of liquids.
4596dry gas, gas condensate, natural gas
4597None
4598None
4599--
4600cbm
46011.n. [Geology]
4602Abbreviation for coalbed methane. Natural gas, predominantly methane [CH4], generated during coal formation and adsorbed in coal. Natural gas adsorbs to the surfaces of matrix pores within the coal and natural fractures, or cleats, as reservoir pressure increases.Production of natural gas from coal requires decreasing the pore pressure below the coal’s desorption pressure so that methane will desorb from surfaces, diffuse through the coal matrix and become free gas. Because the diffusivity and permeability of the coal matrix are ultralow, coal must have an extensive cleat system to ensure adequate permeability and flow of methane to wellbores at economic production rates.Coal seams are typically saturated with water. Consequently, the coal must be dewatered for efficient gas production. Dewatering reduces the hydrostatic pressure and promotes gas desorption from coal. As dewatering progresses, gas production often increases at a rate governed by how quickly gas desorbs from coal, the permeability of the cleat and the relative permeability of the gas-water system in the cleat. Eventually, the rate and amount of gas desorption decreases as the coal seam is depleted of its gas, and production declines.Coal seams with no water (dry coal) have been discovered and commercially exploited. In these reservoirs, the adsorbed gas is held in place by free gas in the cleats. Consequently, gas production consists of both free gas from the cleat system and desorbed gas from the matrix.
4603unconventional resource
4604coal seam gas, CSG
4605coalbed methane, coal bed methane, coal-bed methane
4606--
4607closure
46081.n. [Geology]
4609The vertical distance from the apex of a structure to the lowest structural contour that contains the structure. Measurements of both the areal closure and the distance from the apex to the lowest closing contour are typically incorporated in calculations of the estimated hydrocarbon content of a trap.
4610anticlinal trap, unconformity trap
4611None
4612None
4613--
4614closure
46152.n. [Geology]
4616The area, or areal closure, included in the lowest closing contour of a trap. Measurements of both the areal closure and the distance from the apex to the lowest closing contour are typically incorporated in calculations of the estimated hydrocarbon content of a trap.
4617anticlinal trap, contour, unconformity trap
4618None
4619None
4620--
4621conformable
46221.adj. [Geology]
4623Parallel strata that have undergone a similar geologic history, deposited in succession without interruption.
4624erosion, erosion, hiatus, nonconformity, sequence, sequence boundary, stratum, unconformity
4625None
4626conformity
4627--
4628conformable
46292.adj. [Geology]
4630The nature of the contact between strata deposited in continuous succession.
4631erosion, erosion, hiatus, nonconformity, sequence, sequence boundary, stratum, unconformity
4632None
4633conformity
4634--
4635cyclothem
46361.n. [Reservoir Characterization]
4637A succession of strata deposited during a single cycle of deposition. These sedimentary successions usually occur repeatedly, one above the other. The two main varieties are the cyclic units that are symmetrical cyclothems, and the rhythmic units that are asymmetrical cyclothems. Cyclic groupings of cyclothems are called megacyclothems, and cyclic groupings of megacyclothems are called hypercyclothems. Cyclothems are thought to be due to natural cycles, such as changes in sea levels related to changes in the volume of polar ice caps.
4638None
4639None
4640None
4641--
4642damaged zone
46431.n. [Perforating, Well Completions]
4644The area surrounding the wellbore that has been harmed by the drilling process, generally as a result of mud or cement-filtrate invasion. Near-wellbore damage can significantly affect productivity and is typically easier to prevent than it is to cure. Although almost always present, a lightly damaged zone around the wellbore can be bypassed by perforation tunnels to create connecting conduits from the wellbore to the undamaged reservoir formation. More severe cases of damage may require a matrix-acidizing treatment to restore the natural permeability, or a hydraulic fracturing treatment to create a new high-conductivity flow path to the reservoir.
4645hydraulic fracturing, matrix acidizing
4646None
4647None
4648--
4649depth reference
46501.n. [Formation Evaluation]
4651The 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.
4652depth wheel, first reading, last reading
4653depth datum
4654None
4655--
4656dipole
46571.n. [Geophysics]
4658A pair of opposite (and equal) electrical charges. The strength of the dipole is a vector quantity whose direction points from the positive to the negative charge and whose magnitude is the product of the absolute value of the charge times the separation. A point dipole is an idealized mathematical representation of a dipole in which the separation of the charges goes to zero while their charge increases so that the product (dipole strength) remains constant.
4659None
4660None
4661None
4662--
4663dipole
46642.n. [Geophysics]
4665Two poles of opposite polarity that can generate a field, such as an electric or magnetic field or a dipole source and dipole receiver used in sonic logging for excitation and detection of shear waves.
4666S-wave, shear wave
4667None
4668None
4669--
4670dipole
46713.n. [Geophysics]
4672A small antenna used in electromagnetic surveying that can be represented mathematically as a dipole.
4673electromagnetic method
4674None
4675None
4676--
4677drift
46781.n. [Drilling]
4679A term to describe the inclination from vertical of a wellbore.
4680deviation survey, inclination
4681None
4682None
4683--
4684drift
46852.vb. [Drilling]
4686To guarantee the inside diameter of a pipe or other cylindrical tool by pulling a cylinder or pipe (often called a rabbit) of known outside diameter through it. The drift diameter is the inside diameter (ID) that the pipe manufacturer guarantees per specifications. Note that the nominal inside diameter is not the same as the drift diameter but is always slightly larger. The drift diameter is used by the well planner to determine what size tools or casing strings can later be run through the casing, whereas the nominal inside diameter is used for fluid volume calculations such as mud circulating times and cement slurry placement calculations.
4687casing string, inside diameter, rabbit
4688None
4689None
4690--
4691drift
46923.vb. [Drilling]
4693To pass a gauge through casing, tubulars and completion components to ensure minimum-diameter specifications are within tolerance, as described in definition 2. This task is also performed to ensure that there is no junk, dried cement, dirt, rocks or other debris inside the pipe.
4694None
4695None
4696None
4697--
4698drift
46994.n. [Geophysics]
4700In calibration of a check-shot survey, the difference between geometrically corrected transit time and integrated sonic time.
4701check-shot survey, transit time
4702None
4703None
4704--
4705drift
47065.n. [Geophysics]
4707A gradual change in a measurement or recording device during surveying. Reference to or repetition of a measurement at a base station can indicate whether drift is a problem.
4708base station, survey
4709None
4710None
4711--
4712drift
47136.n. [Well Completions]
4714An accurately machined device that is pulled through the casing, tubulars and completion components to ensure minimum-diameter specifications are within tolerance, as described in definition 2. While this tool is usually of a short length, the well planner may specify a special drift that either has a longer length or a nonstandard outside diameter. The large-diameter casing drifts are frequently known as "rabbits."
4715None
4716rabbit
4717None
4718--
4719darcy units
47201.n. [Well Testing]
4721Units of atm, cm3/s, cp and D, as originally used by Darcy in flow experiments.
4722None
4723None
4724None
4725--
4726depth wheel
47271.n. [Formation Evaluation]
4728A calibrated wheel used to drive the depth recording system in wireline logging. The wheel is pressed against the logging cable as the cable is spooled onto the drum and therefore turns as the cable is run in and out of the borehole. After zeroing the depth on surface, the depth wheel provides the depth input to the recording system. Small errors in calibration and slippage can cause the wheel to introduce systematic errors in the depth recorded. For this reason, the depth is checked and corrected using depth marks. The depth wheel is also referred to as a depth encoder. Modern encoders have two wheels so that slippage can be detected by differences between the two measurements.
4729depth mark
4730None
4731None
4732--
4733direct indicating viscometer
47341.n. [Drilling Fluids]
4735The instrument used to measure viscosity and gel strength of drilling mud. The direct-indicating viscometer is a rotational cylinder and bob instrument, also known as a V-G meter. 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 true centipoise viscosity. For example, at 300 rpm, the dial reading (511 sec-1) is a true viscosity. Bingham plastic rheological parameters are easily calculated from direct-indicating viscometer readings: PV (in units of cp) = 600 dial - 300 dial and YP (in units of lb/100 ft2) = 300 dial - PV. Gel strength is also directly read as dial readings in oilfield units of lb/100 ft2.
4736None
4737Fann viscometer
4738direct-indicating viscometer
4739--
4740drill bit
47411.n. [Drilling]
4742The tool used to crush or cut rock. Everything on a drilling rig directly or indirectly assists the bit in crushing or cutting the rock. The bit is on the bottom of the drillstring and must be changed when it becomes excessively dull or stops making progress. Most bits work by scraping or crushing the rock, or both, usually as part of a rotational motion. Some bits, known as hammer bits, pound the rock vertically in much the same fashion as a construction site air hammer.
4743bottomhole assembly, drillstring, gauge hole, jet, make hole, PDC bit, roller-cone bit, spud
4744bit
4745None
4746--
4747datum
47481.n. [Geophysics]
4749An agreed and known value, such as the elevation of a benchmark or sea level, to which other measurements are corrected. In seismic data, the term refers to an arbitrary planar surface to which corrections are made and on which sources and receivers are assumed to lie to minimize the effects of topography and near-surface zones of low velocity.
4750benchmark, datum correction, elevation correction, receiver, source
4751None
4752None
4753--
4754datum
47552.n. [Well Completions]
4756A depth reference point, typically established at the time the well is completed, against which subsequent depth measurements should be corrected or correlated.
4757None
4758None
4759None
4760--
4761depth derived
47621.adj. [Formation Evaluation]
4763Referring 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.
4764borehole compensation, logging tool, long-spacing sonic log, sonic log, sonic measurement
4765None
4766None
4767--
4768direct indicating viscometer
47691.n. [Drilling Fluids]
4770The instrument used to measure viscosity and gel strength of drilling mud. The direct-indicating viscometer is a rotational cylinder and bob instrument, also known as a V-G meter. 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 true centipoise viscosity. For example, at 300 rpm, the dial reading (511 sec-1) is a true viscosity. Bingham plastic rheological parameters are easily calculated from direct-indicating viscometer readings: PV (in units of cp) = 600 dial - 300 dial and YP (in units of lb/100 ft2) = 300 dial - PV. Gel strength is also directly read as dial readings in oilfield units of lb/100 ft2.
4771Bingham plastic model, deflocculant, gel strength, Herschel-Bulkley fluid, Newtonian fluid, non-Newtonian fluid, plastic viscosity, power-law fluid, rheological property, yield point
4772Fann viscometer
4773None
4774--
4775drill collar
47761.n. [Drilling]
4777A component of a drillstring that provides weight on bit for drilling. Drill collars are thick-walled tubular pieces machined from solid bars of steel, usually plain carbon steel but sometimes of nonmagnetic nickel-copper alloy or other nonmagnetic premium alloys. The bars of steel are drilled from end to end to provide a passage to pumping drilling fluids through the collars. The outside diameter of the steel bars may be machined slightly to ensure roundness, and in some cases may be machined with helical grooves ("spiral collars"). Last, threaded connections, male on one end and female on the other, are cut so multiple collars can be screwed together along with other downhole tools to make a bottomhole assembly (BHA). Gravity acts on the large mass of the collars to provide the downward force needed for the bits to efficiently break rock. To accurately control the amount of force applied to the bit, the driller carefully monitors the surface weight measured while the bit is just off the bottom of the wellbore. Next, the drillstring (and the drill bit), is slowly and carefully lowered until it touches bottom. After that point, as the driller continues to lower the top of the drillstring, more and more weight is applied to the bit, and correspondingly less weight is measured as hanging at the surface. If the surface measurement shows 20,000 pounds [9080 kg] less weight than with the bit off bottom, then there should be 20,000 pounds force on the bit (in a vertical hole). Downhole MWD sensors measure weight-on-bit more accurately and transmit the data to the surface.
4778bottomhole assembly, circulation system, collar, drilling fluid, keyseat, measurements-while-drilling, outside diameter, saver sub, sub, weight indicator
4779None
4780None
4781--
4782day rate
47831.n. [Drilling]
4784The daily cost to the operator of renting the drilling rig and the associated costs of personnel and routine supplies. This cost may or may not include fuel, and usually does not include capital goods, such as casing and wellheads, or special services, such as logging or cementing. In most of the world, the day rate represents roughly half of the cost of the well. Similarly, the total daily cost to drill a well (spread rate) is roughly double what the rig day-rate amount is.
4785casing, cementing, contract depth, drilling contractor, wellhead
4786None
4787None
4788--
4789derivative logs
47901.n. [Reservoir Characterization]
4791Logs that have been calculated from other logs to find the rate at which a log is changing with depth. For example, the derivative caliper (rugosity) calculates the rate at which the caliper is changing from one depth to another. Bad hole conditions that cause the density log to produce incorrect measurements are usually more closely related to the rugosity of the hole than the hole size, so the rugosity curve is the more useful in this regard.
4792None
4793None
4794None
4795--
4796directional driller
47971.n. [Drilling]
4798An individual trained in the science and art of intentionally drilling a well along a predetermined path in three-dimensional space, usually involving deviating the well from vertical and directing it in a specific compass direction or heading. The directional driller considers such parameters as rotary speed, weight on bit, control drilling and when to stop drilling and take surveys of the wellpath, and works closely with the toolpusher.
4799deviation, directional drilling, toolpusher
4800None
4801DD
4802--
4803drill in fluid
48041.n. [Drilling Fluids]
4805A special fluid designed exclusively for drilling through the reservoir section of a wellbore. The reasons for using a specially designed mud are: (1) to drill the reservoir zone successfully, often a long, horizontal drainhole. (2) to minimize damage and maximize production of exposed zones. (3) to facilitate the well completion needed, which can include complicated procedures. A drill-in fluid should resemble a completion fluid. It may be a brine containing only selected solids of appropriate particle size ranges (salt crystals or calcium carbonate) and polymers. Only additives essential for filtration control and cuttings carrying are present in a drill-in fluid.
4806None
4807None
4808drill-in fluid
4809--
4810daylight tour
48111.n. [Drilling]
4812The work shift of a drilling crew that commences at about the sunrise hour. Drilling operations usually take place 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 daylight tour starts at daylight or 8 AM; the graveyard tour is the overnight shift or the shift that begins at midnight. (Pronounced "tower" in many areas.)
4813drilling crew
4814morning tour, tour
4815None
4816--
4817derrick
48181.n. [Drilling]
4819The structure used to support the crown blocks and the drillstring of a drilling rig. Derricks are usually pyramidal in shape, and offer a good strength-to-weight ratio. If the derrick design does not allow it to be moved easily in one piece, special ironworkers must assemble them piece by piece, and in some cases disassemble them if they are to be moved.
4820crown block, derrickman, escape line, fingerboard, gooseneck, mast, round trip, sheave, slide, standpipe, sub, tongs, traveling block
4821None
4822None
4823--
4824directional drilling
48251.n. [Drilling, Shale Gas]
4826The 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.
4827bottomhole assembly, crooked hole, deviated drilling, directional driller, directional well, dogleg, drill bit, driller, geosteering, horizontal drilling, mud motor, rotary drilling, rotary steerable system, slide, steerable motor
4828None
4829None
4830--
4831drill noise vertical seismic profile
48321.n. [Geophysics]
4833A 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.
4834acquisition, noise, receiver, reflection, source, vertical seismic profile
4835None
4836None
4837--
4838db
48391.n. [Geophysics]
4840The unit of measurement to compare the relative intensity of acoustic or electrical signal, equal to one-tenth of a bel, named for American inventor Alexander Graham Bell (1847 to 1922). The logarithm of the ratio of the sound or signal to a standard provides the decibel measurement. The symbol for the unit is dB. Humans typically hear sounds in the range of 20 to 50 dB in conversation, and upwards of 90 dB when exposed to heavy machinery or aircraft.
4841None
4842None
4843decibel
4844--
4845derrick floor
48461.n. [Drilling]
4847The relatively small work area in which the rig crew conducts operations, usually adding or removing drillpipe to or from the drillstring. The rig floor is the most dangerous location on the rig because heavy iron is moved around there. Drillstring connections are made or broken on the drillfloor, and the driller's console for controlling the major components of the rig are located there. Attached to the rig floor is a small metal room, the doghouse, where the rig crew can meet, take breaks and take refuge from the elements during idle times.
4848doghouse, slide, Texas deck
4849rig floor
4850None
4851--
4852directional permeability
48531.n. [Well Testing]
4854Permeability that varies with direction of flow through the porous medium. Lateral permeability contrast can be particularly important in fractured formations, where effective permeability in the direction of the fractures may be many times greater than the matrix permeability. If the permeability in one direction is significantly more than in the other, the flow pattern may more closely approximate linear flow than radial flow. This can be detected from well-test data.Likewise, laminations in most clastic formations cause the permeability normal to the bedding plane to be less than the lateral permeability parallel to bedding. This is called vertical to horizontal permeability anisotropy.
4855bed, isotropic permeability, lamination, linear flow
4856None
4857None
4858--
4859drill pipe
48601.n. [Drilling]
4861Tubular 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.
4862bottomhole assembly, circulation system, drilling fluid, drillstem, drillstring, joint, tool joint
4863None
4864None
4865--
4866dd
48671.n. [Drilling Fluids]
4868A surfactant-type mud additive intended to prevent formation shales and clays from sticking to the drilling assembly and also to prevent gumbo shale from agglomerating and plugging the annulus and flowlines. Some DDs are claimed to be mud lubricants that lessen the torque and drag of the drillstring as it is rotated and moved up and down in the hole.
4869None
4870None
4871drilling detergent
4872--
4873dd
48742.n. [Drilling]
4875An individual trained in the science and art of intentionally drilling a well along a predetermined path in three-dimensional space, usually involving deviating the well from vertical and directing it in a specific compass direction or heading. The directional driller considers such parameters as rotary speed, weight on bit, control drilling and when to stop drilling and take surveys of the wellpath, and works closely with the toolpusher.
4876None
4877None
4878directional driller
4879--
4880derrickman
48811.n. [Drilling]
4882One of the rig crew members who gets his name from the fact that he works on a platform attached to the derrick or mast, typically 85 ft [26 m] above the rig floor, during trips. On small land drilling crews, the derrickman is second in rank to the driller. Larger offshore crews may have an assistant driller between the derrickman and the driller. In a typical trip out of the hole (TOH), the derrickman wears a special safety harness that enables him to lean out from the work platform (called the monkeyboard) to reach the drillpipe in the center of the derrick or mast, throw a line around the pipe and pull it back into its storage location (the fingerboards) until it is time to run the pipe back into the well. In terms of skill, physical exertion and perceived danger, a derrickman has one of the most demanding jobs on the rig crew. Some modern drilling rigs have automated pipe-handling equipment such that the derrickman controls the machinery rather than physically handling the pipe. In an emergency, the derrickman can quickly reach the ground by an escape line often called the Geronimo line.
4883derrick, driller, drilling crew, escape line, fingerboard, gas-cut mud, monkeyboard, racking back pipe, round trip
4884None
4885None
4886--
4887derrickman
48882.n. [Drilling Fluids]
4889The member of the drilling crew in charge of the mud-processing area during periods of circulation. The derrickman also measures mud density and conducts the Marsh funnel viscosity test on a regular basis when the mud is circulating in the hole. The derrickman reports to the toolpusher, but is instructed in detail by the mud engineer on what to add to the mud, how fast and how much. His other job is to handle pipe in the derrick while pulling out or running into the hole.
4890chemical barrel, funnel viscosity, Marsh funnel, mud balance, mud density, mud engineer
4891None
4892None
4893--
4894directional survey
48951.n. [Drilling]
4896A 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.
4897survey
4898deviation survey
4899None
4900--
4901drill ship
49021.n. [Drilling]
4903A 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.
4904dynamic positioning, moon pool
4905None
4906None
4907--
4908decibel
49091.n. [Geophysics]
4910The unit of measurement to compare the relative intensity of acoustic or electrical signal, equal to one-tenth of a bel, named for American inventor Alexander Graham Bell (1847 to 1922). The logarithm of the ratio of the sound or signal to a standard provides the decibel measurement. The symbol for the unit is dB. Humans typically hear sounds in the range of 20 to 50 dB in conversation, and upwards of 90 dB when exposed to heavy machinery or aircraft.
4911acoustic, bel, dynamic range, signal
4912None
4913dB
4914--
4915desander
49161.n. [Drilling]
4917A hydrocyclone device that removes large drill solids from the whole mud system. The desander should be located downstream of the shale shakers and degassers, but before the desilters or mud cleaners. A volume of mud is pumped into the wide upper section of the hydrocylone at an angle roughly tangent to its circumference. As the mud flows around and gradually down the inside of the cone shape, solids are separated from the liquid by centrifugal forces. The solids continue around and down until they exit the bottom of the hydrocyclone (along with small amounts of liquid) and are discarded. The cleaner and lighter density liquid mud travels up through a vortex in the center of the hydrocyclone, exits through piping at the top of the hydrocyclone and is then routed to the mud tanks and the next mud-cleaning device, usually a desilter. Various size desander and desilter cones are functionally identical, with the size of the cone determining the size of particles the device removes from the mud system.
4918degasser, desilter, mud cleaner, shale shaker
4919None
4920None
4921--
4922directional variograms
49231.n. [Reservoir Characterization]
4924Variograms and semivariograms that have a directional component in addition to the normal distance component. Directional variograms and semivariograms are commonly used where geological features are heterogeneous. For example, fluvial environments dominated by valleys, channels and point bars are likely to have directional components that are detectable and that will influence the behavior of fluids in these formations. Geostatistical models that use directional variograms can be expected to be more reliable in these circumstances.
4925channel, geostatistical modeling, heterogeneous formation, point bar, variogram
4926None
4927None
4928--
4929drill solids
49301.n. [Drilling Fluids]
4931Formation solids contained in a mud system, generally considered to be detrimental to the drilling operation because they produce high plastic viscosity, yield point and gel strengths and build poor-quality filter cakes. They also occupy space that is needed for barite in high-density muds. Drill solids cause excessive wear in the mud pumps and other rig equipment. Solids control is aimed at economically and efficiently removing drill solids. This implies removal as soon as possible after they enter the mud system, while the particles are at their largest size.
4932bypass, closed mud system, deflocculant, filter cake, gel strength, high-gravity solids, low-gravity solids, plastic viscosity, retort solids, sand test, yield point
4933None
4934None
4935--
4936decollement
49371.n. [Geology]
4938A fault surface parallel to a mechanically weak horizon or layer, or parallel to bedding, that detaches or separates deformed rocks above from undeformed or differently deformed rocks below. Decollements, or decollement surfaces, are typical of regions of thrust faulting such as the Alps.
4939fault, thrust fault
4940None
4941None
4942--
4943desilter
49441.n. [Drilling]
4945A hydrocyclone much like a desander except that its design incorporates a greater number of smaller cones. As with the desander, its purpose is to remove unwanted solids from the mud system. The smaller cones allow the desilter to efficiently remove smaller diameter drill solids than a desander does. For that reason, the desilter is located downstream from the desander in the surface mud system.
4946drill solids
4947None
4948None
4949--
4950directional well
49511.n. [Drilling]
4952A wellbore that requires the use of special tools or techniques to ensure that the wellbore path hits a particular subsurface target, typically located away from (as opposed to directly under) the surface location of the well.
4953directional drilling, horizontal drilling, slant rig
4954None
4955None
4956--
4957drillable packer
49581.n. [Well Completions]
4959A packer assembly that can be removed from the wellbore only by drilling or milling. Drillable packers, and similar tools such as bridge plugs, are typically made from cast iron, aluminum, plastic or similar brittle materials.
4960None
4961None
4962None
4963--
4964deconvolution
49651.n. [Geophysics]
4966A step in seismic signal processing to recover high frequencies, attenuate multiples, equalize amplitudes, produce a zero-phase wavelet or for other purposes that generally affect the waveshape. Deconvolution, or inverse filtering, can improve seismic data that were adversely affected by filtering, or convolution that occurs naturally as seismic energy is filtered by the Earth. Deconvolution can also be performed on other types of data, such as gravity, magnetic or well log data.
4967autocorrelation, backscatter, deterministic deconvolution, filter, inverse filter, processing, resolution, signature deconvolution, zero-phase
4968None
4969None
4970--
4971deconvolution
49722.n. [Formation Evaluation]
4973With reference to induction logging, a method of removing shoulder-bed effects from an induction log. The term refers to early 6FF40 and deep induction logs in which the standard method of deconvolution was based on three measurements separated by 78 in. [198 cm] in depth. The three measurements were weighted by an amount calculated to reduce the effect of shoulder beds on the readings in a high-resistivity bed. Originally, the resistivity of the shoulder beds could be input, but in later usage this resistivity became standardized at 1 ohm-m. The deconvolution was not effective in high-contrast formations. In modern tools, the shoulder effect is corrected by using an inverse filter or an automatic inversion.
49746FF40, bed, inverse filter, shoulder bed
4975None
4976None
4977--
4978deconvolution
49793.n. [Well Testing]
4980A mathematical operation that uses downhole flow-rate measurements to transform bottomhole pressure measurements distorted by variable rates to an interpretable transient. Deconvolution also can use surface rates to transform wellhead pressures to an interpretable form. Deconvolution has the advantage over convolution that it does not assume a particular model for the pressure-transient response. However, the simplest form of deconvolution often gives a noisy result, and more complex approaches may be computing intensive.
4981convolution, transient-rate and pressure-test analysis
4982None
4983None
4984--
4985detectable limit
49861.n. [Geophysics]
4987The minimum thickness necessary for a layer of rock to be visible or distinct in reflection seismic data. Generally, the detectable limit is at least 1/30 of the wavelength. Acquisition of higher frequency seismic data generally results in better detection or vertical resolution of thinner layers.
4988vertical resolution, wavelength
4989None
4990None
4991--
4992directivity
49931.n. [Geophysics]
4994The property of some seismic sources whereby the amplitude, frequency, velocity or other property of the resulting seismic waves varies with direction. A directional charge, such as a length of primer cord or a linear array of charges, can be used when directivity is desirable. Directivity is also a property of geophone arrays, air guns, explosives or vibrators, which can be positioned to reduce horizontal traveling noise such as ground roll. Receivers in the form of groups in which the individual geophones or hydrophones are separated from each other in linear (1D) or areal (2D) arrays are directional, and are designed to suppress signal arriving nearly horizontally and to pass nearly vertical arrivals with minimum attenuation or distortion. Directivity is often present, but the difficulty in accounting for it during seismic processing makes it undesirable in most cases.
4995air gun, geophone array, ground roll, hydrophone, primer cord, receiver, seismic processing, shaped charge, source, vibrator, wave
4996None
4997None
4998--
4999drilled solids
50001.n. [Drilling Fluids]
5001Formation solids contained in a mud system, generally considered to be detrimental to the drilling operation because they produce high plastic viscosity, yield point and gel strengths and build poor-quality filter cakes. They also occupy space that is needed for barite in high-density muds. Drill solids cause excessive wear in the mud pumps and other rig equipment. Solids control is aimed at economically and efficiently removing drill solids. This implies removal as soon as possible after they enter the mud system, while the particles are at their largest size.
5002bottomhole assembly, deflocculant, filter cake, gel strength, high-gravity solids, low-gravity solids, retort solids, yield point
5003None
5004None
5005--
5006deep induction
50071.n. [Formation Evaluation]
5008A 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.
5009cave effect, depth of investigation, dual induction, geometrical factor
5010None
5011ID
5012--
5013detergency
50141.n. [Enhanced Oil Recovery]
5015The ability of a chemical agent to remove a contaminant from a solid surface. For example, in enhanced oil recovery, a surfactant can be used to remove an oil phase from a mineral surface. At least two mechanisms can occur: a) The surfactant adsorbs on the contaminated surface and presents its hydrophilic group to the contacting liquid. Thus, the surface behaves hydrophilically and repels macroscopic oil drops. b) The surfactant adsorbs to the contaminant. It is energetically more favorable for the combination of surfactant and contaminant to be in solution than to be attached to the surface so the contaminant is solubilized, exposing the mineral surface.
5016None
5017None
5018None
5019--