j0FCLDDw

1routine core analysis
21.n. [Formation Evaluation]
3The set of measurements normally carried out on core plugs or whole core. These generally include porosity, grain density, horizontal permeability, fluid saturation and a lithologic description. Routine core analyses often include a core gamma log and measurements of vertical permeability. Measurements are made at room temperature and at either atmospheric confining pressure, formation confining pressure, or both. Routine core analysis is distinct from special core analysis (SCAL).Recommended practices for routine core analysis are available in the API document RP40.
4core plug, sidewall core, whole core
5None
6None
7--
8reciprocate
91.vb. [Drilling]
10To alternately raise and lower the drillstring, casing string or liner in the wellbore. Reciprocation is usually limited to 30 to 60 ft [9 to 18 m] of vertical travel in the derrick. The purpose of reciprocating the drillstring is usually to clean cuttings and other debris from the wellbore. Reciprocating the strings can improve the chances of a good cement job in casing or liners.
11cementing, cuttings, liner
12None
13None
14--
15reservoir characterization
161.n. [Reservoir Characterization]
17A model of a reservoir that incorporates all the characteristics of the reservoir that are pertinent to its ability to store hydrocarbons and also to produce them. Reservoir characterization models are used to simulate the behavior of the fluids within the reservoir under different sets of circumstances and to find the optimal production techniques that will maximize the production.
18None
19reservoir description
20None
21--
22reservoir characterization
232.n. [Reservoir Characterization]
24The act of building a reservoir model based on its characteristics with respect to fluid flow.
25None
26reservoir description
27None
28--
29rhombohedral packing
301.n. [Geology]
31The most compact arrangement in space of uniform spheres (atoms and molecules in mineral crystals, or grains in sedimentary rocks) that results in a structure having no more than 26% porosity. Rhombohedral packing is more stable mechanically than cubic packing. Cubic packing is the most porous packing arrangement, with about 47% porosity in the ideal situation. Most sediments, however, 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 of ideal cubic packing and commonly less than the 26% porosity of ideal rhombohedral packing.
32compaction, cubic packing, mineral, porosity, sedimentary, sorting
33None
34None
35--
36rugose
371.adj. [Formation Evaluation]
38Pertaining to a borehole wall that is rough.
39bad hole, rugosity
40None
41None
42--
43record
441.vb. [Geophysics]
45To detect and measure energy.
46None
47None
48None
49--
50record
512.n. [Geophysics]
52In seismic data, the energy detected and measured by a receiver. Normally, most of the energy is provided by a seismic source. Noise records are obtained in the absence of a seismic source to measure background or ambient noise levels.
53brute stack, noise, receiver, source
54None
55None
56--
57reservoir characterization model
581.n. [Shale Gas]
59A model of a specific volume of the subsurface that incorporates all the geologic characteristics of the reservoir. Such models are used to quantify characteristics within the subsurface volume that are relatively stable over long periods of time and can, therefore, be considered static. These attributes include the structural shape and thicknesses of the formations within the subsurface volume being modeled, their lithologies, and the porosity and permeability distributions. These last two characteristics often vary significantly from location to location within the volume, resulting in heterogeneity. However, porosity and permeability are stable in the near-geologic timeframe and do not change due to the movement of fluids or gases through any of the formations pore spaces. The result of reservoir characterization is a reservoir characterization model (also known as a static model and sometimes referred to as a geologic model).Shale gas reservoir rocks require the analysis of high-quality seismic data, core, and log measurements and engineering data to produce an accurate reservoir characterization model. This model is then used as input into reservoir simulation, during which reservoir engineers add other reservoir characteristics, such as pressures, temperatures, and fluid and gas compositions. These features can change due to the movement of fluids or gases through any of the formations pore spaces. Since these are dynamic in their nature over short timeframes, once production is initiated these models are referred to as dynamic models. Thorough reservoir simulations (dynamic models) that are based on accurately developed reservoir characterizations (static models) can be of significant value in optimizing well placement and field-development planning.
60None
61None
62None
63--
64rig
651.n. [Drilling]
66The machine used to drill a wellbore. In onshore operations, the rig includes virtually everything except living quarters. Major components of the rig include the mud tanks, the mud pumps, the derrick or mast, the drawworks, the rotary table or topdrive, the drillstring, the power generation equipment and auxiliary equipment. Offshore, the rig includes the same components as onshore, but not those of the vessel or drilling platform itself. The rig is sometimes referred to as the drilling package, particularly offshore.
67rig up
68drilling rig
69None
70--
71rugosity
721.n. [Formation Evaluation]
73A qualitative description of the roughness of a borehole wall. Alternatively, the term pertains to a borehole whose diameter changes rapidly with depth. The term usually refers to changes at the scale of logging measurements, a few inches to a few feet, and to the effect this has on logging tool responses. Rugosity can be observed on caliper logs, image logs and by its effect on measurements with a small depth of investigation.
74bad hole
75None
76None
77--
78recorder
791.n. [Formation Evaluation]
80Also called camera, the device used in early logging to record logging measurements on photographic film. The camera consisted of a light shining on galvanometers, which reflected the light to produce a trace on one or more films. The galvanometers deflected according to the log measurement to give the log reading. The films were turned by the depth wheel, which gave the depth axis of the log.
81None
82camera
83None
84--
85reservoir description
861.n. [Reservoir Characterization]
87Also called reservoir characterization, a model of a reservoir that incorporates all the characteristics of the reservoir that are pertinent to its ability to store hydrocarbons and also to produce them. Reservoir characterization models are used to simulate the behavior of the fluids within the reservoir under different sets of circumstances and to find the optimal production techniques that will maximize the production.
88None
89reservoir characterization
90None
91--
92reservoir description
932.n. [Reservoir Characterization]
94The act of building a reservoir model based on its characteristics with respect to fluid flow.
95None
96reservoir characterization
97None
98--
99rig down
1001.vb. [Drilling]
101To take apart equipment for storage and portability. Equipment typically must be disconnected from power sources, decoupled from pressurized systems, disassembled and moved off the rig floor or even off location.
102None
103None
104Antonyms:rig up
105--
106run in hole
1071.vb. [Drilling]
108To connect pipe together and lower the connected length into the borehole in a controlled fashion. The pipe lengths are usually screwed together either with rotary-shouldered connections for the drillstring, or threaded and coupled connections for casing, liners and most tubing.
109RIH, round trip
110None
111Antonyms:come out of the hole
112--
113recorder carrier
1141.n. [Well Completions]
115A downhole tool used to locate or convey a downhole gauge. Recorder carriers may be incorporated into temporary completions, such as for testing purposes, or run on slickline for temporary placement within the wellbore. In some cases, permanent gauges may be installed in recorder carriers run as completion components.
116None
117None
118None
119--
120reservoir drive mechanisms
1211.n. [Production Testing, Enhanced Oil Recovery]
122Natural forces in the reservoir that displace hydrocarbons out of the reservoir into the wellbore and up to surface.Reservoir-drive mechanisms include gasdrive (gas cap or solution gasdrive), waterdrive (bottomwater drive or edgewater drive), combination drive, and gravity drainage. Waterdrive is the most efficient drive mechanism, followed by gasdrive and gravity drainage.Reservoir-drive mechanisms are also called natural drives.
123primary recovery
124None
125None
126--
127rig floor
1281.n. [Drilling]
129The 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.
130doghouse, slide, sub, Texas deck
131derrick floor
132None
133--
134running squeeze
1351.n. [Well Workover and Intervention]
136A cement-squeeze technique in which the cement slurry is continuously injected until the desired squeeze pressure is achieved. When pumping stops, the final squeeze pressure is monitored. If the pressure falls, additional slurry is squeezed to increase the pressure back to the final squeeze value. This process is repeated until the final squeeze pressure can be sustained.
137None
138None
139None
140--
141recoverable gas lift gas
1421.n. [Production Testing]
143Injection gas that has returned to surface and it is not reinjected into the gas-lift system. Instead, it is transferred to a pipeline. This gas is sometimes called spent gas-lift gas.
144injection gas
145None
146None
147--
148reservoir pressure
1491.n. [Geology]
150The pressure of fluids within the pores of a reservoir, usually hydrostatic pressure, or the pressure exerted by a column of water from the formation's depth to sea level. When impermeable rocks such as shales form as sediments are compacted, their pore fluids cannot always escape and must then support the total overlying rock column, leading to anomalously high formation pressures. Because reservoir pressure changes as fluids are produced from a reservoir, the pressure should be described as measured at a specific time, such as initial reservoir pressure.
151hydrostatic pressure, lithostatic pressure, retrograde condensation, virgin pressure
152hydrostatic pressure
153None
154--
155reservoir pressure
1562.n. [Drilling]
157The pressure of the subsurfaceformationfluids, commonly expressed as the density of fluid required in the wellbore to balance that pore pressure. A normal pressure gradient might require 9 lbm/galUS[1.08 kg/m3], while an extremely high gradient may need 18 lbm/galUS [2.16 kg/m3] or higher.
158None
159None
160formation pressure, pore pressure
161--
162reservoir pressure
1633.n. [Well Completions]
164The pressure within the reservoir rock. The formation pressure value can be further categorized as relating to flowing well or shut-in conditions.
165None
166None
167formation pressure, pore pressure
168--
169rig up
1701.vb. [Drilling]
171To make ready for use. Equipment must typically be moved onto the rig floor, assembled and connected to power sources or pressurized piping systems.
172None
173None
174Antonyms:rig down
175--
176s wave
1771.n. [Geophysics]
178An elastic body wave in which particles oscillate perpendicular to the direction in which the wave propagates. S-waves are generated by most land seismic sources, but not by air guns. P-waves that impinge on an interface at non-normal incidence can produce S-waves, which in that case are known as converted waves. S-waves can likewise be converted to P-waves. S-waves, or shear waves, travel more slowly than P-waves and cannot travel through fluids because fluids do not support shear. Recording of S-waves requires receivers coupled to the solid Earth. Interpretation of S-waves can allow determination of rock properties such as fracture density and orientation, Poisson's ratio and rock type by crossplotting P-wave and S-wave velocities, and by other techniques.
179acoustic wave, seismic, shear
180shear wave, tangential wave
181None
182--
183shear wave
1841.n. [Geophysics]
185Also known as S-wave, an elastic body wave in which particles oscillate perpendicular to the direction in which the wave propagates. S-waves are generated by most land seismic sources, but not by air guns. P-waves that impinge on an interface at non-normal incidencecan produce S-waves, which in that case are known as converted waves. S-waves can likewise be converted to P-waves. S-waves, or shear waves, travel more slowly than P-waves and cannot travel through fluids because fluids do not support shear. Recording of S-waves requires receivers coupled to the solid Earth.Interpretationof S-waves can allow determination ofrock propertiessuch as fracture density and orientation, Poisson's ratio androcktype by crossplotting P-wave and S-wave velocities, and by other techniques.
186four-component seismic data
187S-wave, tangential wave
188None
189--
190snubbing
1911.n. [Drilling]
192The act of putting drillpipe into the wellbore when the blowout preventers (BOPs) are closed and pressure is contained in the well. Snubbing is necessary when a kick is taken, since well kill operations should always be conducted with the drillstring on bottom, and not somewhere up the wellbore. If only the annular BOP has been closed, the drillpipe may be slowly and carefully lowered into the wellbore, and the BOP itself will open slightly to permit the larger diameter tool joints to pass through. If the well has been closed with the use of ram BOPs, the tool joints will not pass by the closed ram element. Hence, while keeping the well closed with either another ram BOP or the annular BOP, the ram must be opened manually, then the pipe lowered until the tool joint is just below the ram, and then closing the ram again. This procedure is repeated whenever a tool joint must pass by a ram BOP. In snubbing operations, the pressure in the wellbore acting on the cross-sectional area of the tubular can exert sufficient force to overcome the weight of the drillstring, so the string must be pushed (or "snubbed") back into the wellbore. In ordinary stripping operations, the pipe falls into the wellbore under its own weight, and no additional downward force or pushing is required.
193annular blowout preventer, blowout preventer, kick, kill, ram blowout preventer, stripping, tool joint
194None
195None
196--
197snubbing
1982.n. [Well Workover and Intervention]
199The act of forcing a pipe or tubular into a well against wellborepressure. Well-intervention techniques in live wells, such ascoiled tubingand snubbing, use equipment designed to apply the necessary forces while supporting the tubing and safely containing wellbore pressure and fluids.
200snub
201None
202None
203--
204stimulation
2051.n. [Enhanced Oil Recovery, Well Completions, Well Workover and Intervention, Shale Gas]
206A treatment performed to restore or enhance the productivity of a well. Stimulation treatments fall into two main groups, hydraulic fracturing treatments and matrix treatments. Fracturing treatments are performed above the fracture pressure of the reservoir formation and create a highly conductive flow path between the reservoir and the wellbore. Matrix treatments are performed below the reservoir fracture pressure and generally are designed to restore the natural permeability of the reservoir following damage to the near-wellbore area. Stimulation in shale gas reservoirs typically takes the form of hydraulic fracturing treatments.
207matrix stimulation
208well stimulation
209None
210--
211sacrificial anode
2121.n. [Drilling Fluids]
213A 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.
214anode, corrosion coupon
215None
216None
217--
218sheave
2191.n. [Drilling]
220A pulley. In oilfield usage, the term usually refers to either the pulleys permanently mounted on the top of the rig (the crown blocks), or the pulleys used for running wireline tools into the wellbore. In the case of the crown blocks, the drilling line, a heavy wire rope, is threaded between the crown blocks and the traveling blocks in a block and tackle arrangement to gain mechanical advantage. A relatively weak drilling line, with a breaking strength of perhaps 100,000 pounds [45,400 kg], may be used to lift much larger loads, perhaps in excess of one million pounds [454,000 kg]. During wireline operations, two sheaves are temporarily hung in the derrick, and the wireline is run from the logging truck through the sheaves and then down to the logging tool in the wellbore.
221block, crown block, derrick, slip-and-cut, traveling block
222None
223None
224--
225snubbing jack
2261.n. [Well Workover and Intervention]
227The components of a snubbing unit that provide the vertical stroke or movement required to run or retrieve the work string. Snubbing jacks are hydraulically operated and can apply extremely high forces to the tubing string and the wellhead to which they are attached.
228work string
229None
230None
231--
232stimulation byproduct
2331.n. [Well Workover and Intervention]
234A compound formed by a secondary reaction of stimulation fluids with fluids or solids present in the reservoir matrix. The most damaging stimulation byproducts are the insoluble precipitates that can form when the pH of the treatment fluid increases during the reaction process. Precipitates of iron compounds can be particularly problematic if conditions allow the formation of gelatinous, insoluble ferric compounds in the near-wellbore area.
235None
236None
237None
238--
239safety clamp
2401.n. [Well Workover and Intervention]
241A mechanical device attached to tool strings or flush surface tubulars as they are assembled or disassembled. The safety clamp prevents the tool string from being dropped downhole accidentally if the slips or elevators securing the string lose their grip.
242None
243None
244None
245--
246sheen test
2471.n. [Drilling Fluids]
248A test intended to indicate the presence of free oil when drilling fluid, drilled cuttings, deck drainage, well treatment fluids, completion and workover fluids, produced water or sand or excess cement slurry are discharged into offshore waters. Two types of sheen tests are mandated by EPA under NPDES permits. The visual sheen test consists of an observation made when surface and atmospheric conditions permit watching the ocean water for a sheen around the point where the discharge entered the water. When the conditions do not permit visual observations, a static sheen test is mandated by NPDES permits and the protocol published by US EPA. This test uses sea water in a shallow pan (not more than 30 cm deep) with 1000 cm2 surface area. Either 15 cm3 of fresh mud or 15 g fresh cuttings are injected below the surface of the water. An observer watches for up to 1.0 hour for a silvery, metallic, colored or iridescent sheen. If sheen covers 50% of the area, the mud or cuttings cannot be discharged.Reference:Federal Register 57, no. 224 (November 19, 1992): 54652-57.Weintritt DJ, Qaisieh NS and Otto GH: "How To Improve Accuracy in the EPA Static Sheen Test," Oil & Gas Journal 91, no. 18 (May 3, 1993): 77-83.
249emulsion mud, EPA, Minerals Management Service, MMS, mysid shrimp, NPDES, oil mud, sheen, synthetic-base mud
250None
251None
252--
253soak phase
2541.n. [Heavy Oil, Enhanced Oil Recovery]
255In cyclic steam injection, the second phase between the steam-injection phase and the production phase. During the soak phase, the well is shut in for several days to allow uniform heat distribution to thin the oil.
256thermal recovery
257steam soak
258None
259--
260stochastic modeling
2611.n. [Reservoir Characterization]
262The production of a model of a reservoir or field by using stochastic methods to interpolate between data measurements (usually wells).
263stochastic analysis
264None
265None
266--
267safety joint
2681.n. [Drilling]
269A weak spot in the drillstring. Such a weak spot sometimes is intentionally put into the drillstring so that if tension in the drillstring exceeds a predetermined amount, the safety joint will part and the rest of the drillstring will be salvageable. A safety joint is commonly included in fishing strings and drillstem testing equipment, where the fish may be successfully caught by the fishing assembly, but tension to free the fish may prove insurmountable. By having the safety joint in the hole, the fishing company representative knows where the fishing string will part and what will be needed to latch onto the top of this additional fish.
270drillstem test, fishing tool
271None
272None
273--
274safety joint
2752.n. [Well Completions, Well Workover and Intervention]
276Another term for release joint, a downhole tool that is designed to part under controlled conditions. A release joint enables part of the tool string to be left in the wellbore while the running string is retrieved.
277None
278release joint
279None
280--
281shifted spectrum
2821.n. [Formation Evaluation]
283A technique in nuclear magnetic resonance (NMR) logging based on the shift in the T2 distributions, or spectra, acquired with different echo spacings. The technique is usually used to detect gas or light oil. These fluids have a significant diffusion relaxation. A measurement made with a standard short echo spacing will give a signal from these fluids at a certain T2. A measurement made with a long echo spacing will cause more diffusion relaxation and a shorter T2. Other fluids, with minor contribution from diffusion, will not be changed. Gas and light oil can therefore be identified by the shift between the two T2 distributions.
284differential spectrum, diffusion relaxation, direct hydrocarbon typing, echo spacing, nuclear magnetic resonance measurement, transverse relaxation
285None
286None
287--
288soda ash
2891.n. [Drilling Fluids]
290Another term for sodium carbonate, a chemical with the formula Na2CO3. It is called soda ash at the drilling rig and is used to treat most types of calcium ion contamination in freshwater and seawater muds. For cement contamination, sodium bicarbonate is used. Calcium ions from drilling gypsum or anhydrite, CaSO4, cause clay flocculation and polymer precipitation and lower pH. A soda-ash treatment is appropriate for gypsum contamination because caustic soda, NaOH, is not needed to raise pH. This is also generally the case with hard water influxes into water muds.
291acrylate polymer, calcium carbonate, carbonate ion, carbonate test, Garrett Gas Train, hardness ion, hydrolysis, phenolphthalein, prehydrated bentonite, seawater mud, sodium bicarbonate, soft water
292sodium carbonate
293None
294--
295stoiip
2961.n. [Enhanced Oil Recovery]
297Abbreviation for stock-tank oil initially in place, the volume of oil in a reservoir prior to production.
298None
299None
300stock-tank oil initially in place, stock-tank original oil in place, STOOIP
301--
302safety spacer
3031.n. [Perforating]
304A blank gun section or spacer installed between the top perforating-gun assembly and firing head in a TCP operation. The safety spacer serves to position the gun assembly a safe distance below the rig floor during arming and disarming operations. The spacer should be a minimum of 10 feet [3 m] in length. In some cases, a longer safety spacer will be required to ensure that the gun assembly is positioned safely below the living quarters or other occupied areas of the drilling rig.
305rig floor
306None
307None
308--
309shifting tool
3101.n. [Well Completions]
311A downhole tool, most commonly associated with slickline operations, that is used to open, close or shift the position of downhole flow control or circulation devices, such as sliding sleeves. The shifting tool generally features some means of engaging the components to be shifted and is typically run with upward or downward operating jars to deliver the necessary force or impact.
312None
313None
314None
315--
316shifting tool
3172.n. [Well Workover and Intervention]
318A downhole tool used to adjust the position of sliding sleeves or similar production and completion equipment. Shifting tools are typically run on slickline, although they may be used with coiled tubing in deviated or horizontal wellbores. Shifting tools are generally prepared or dressed for use with a specific model and size of sliding sleeve, requiring careful selection of the appropriate shifting tool.
319None
320None
321None
322--
323sodium bicarbonate
3241.n. [Drilling Fluids]
325A chemical with the formula NaHCO3. It is called bicarb at the drilling rig and is used to treat cement contamination in water mud. When cement hydrates, substantial amounts of lime, Ca(OH)2, are produced. As the cement sets, less free lime is available. When partially set cement is drilled with a water mud, Ca+2 and OH- ions are leached into the mud, often causing problems associated with clay flocculation and polymer precipitation. Bicarb can be added, either as a pretreatment or over a period of time, to remove the Ca+2 in the form of insoluble CaCO3 while simultaneously neutralizing OH- ions with the H+ ion in the bicarb molecule.
326acrylate polymer, bicarbonate, carbonate ion, carbonate test, Garrett Gas Train, hardness ion, hydrolysis, pH, phenolphthalein, polymer, sodium carbonate
327bicarb
328None
329--
330stoneley permeability
3311.n. [Formation Evaluation]
332The ability of fluid to move through a rock, as measured by the reduction in amplitude or increase in slowness of the acoustic Stoneley wave generated in the borehole. The velocity and amplitude of the Stoneley wave are reduced by the presence of mobile fluids in the formation. Physically, the effect can be seen as a coupling of the Stoneley energy into a formation wave known as the slow wave, as predicted by the Biot theory. The amount of reduction is a complicated function of this mobility (or permeability divided by viscosity), the properties of the borehole fluid, the pore fluid and the mudcake, the elastic properties of the rock and the frequency. Since all these factors are measured or estimated from logs, it is possible to determine formation mobility. In practice, the mobility needs to be reasonably high for the method to be accurate.
333Biot theory, Stoneley wave
334None
335None
336--
337sagd
3381.n. [Heavy Oil]
339A thermal production method for heavy oil that pairs a high-angle injection well with a nearby production well drilled along a parallel trajectory. The pair of high-angle wells is drilled with a vertical separation of about 5 m [16 ft]. Steam is injected into the reservoir through the upper well. As the steam rises and expands, it heats up the heavy oil, reducing its viscosity. Gravity forces the oil to drain into the lower well where it is produced.
340steam-assisted gravity drainage
341None
342None
343--
344shoe
3451.n. [Drilling]
346The bottom of the casing string, including the cement around it, or the equipment run at the bottom of the casing string.
347bullhead, float shoe, plug and abandon
348casing shoe
349None
350--
351shoe
3522.n. [Drilling]
353A 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.
354float shoe, guide shoe
355casing shoe
356None
357--
358shoe
3593.n. [Drilling]
360A tapered, often bullet-nosed piece of equipment often found on the bottom of a casing string. The device guides the casing toward the center of the hole and minimizes problems associated with hitting rock ledges or washouts in the wellbore as the casing is lowered into the well. The outer portions of the guide shoe are made from steel, generally matching the casing in size and threads, if not steel grade. The inside (including the taper) is generally made of cement or thermoplastic, since this material must be drilled out if the well is to be deepened beyond the casing point. It differs from a float shoe in that it lacks a check valve.
361casing point, casing string, check valve, float shoe, washout
362guide shoe
363None
364--
365sodium carbonate
3661.n. [Drilling Fluids]
367A chemical with the formula Na2CO3. It is called soda ash at the drilling rig and is used to treat most types of calcium ion contamination in freshwater and seawater muds. For cement contamination, sodium bicarbonate is used. Calcium ions from drilling gypsum or anhydrite, CaSO4, cause clay flocculation and polymer precipitation and lower pH. A soda-ash treatment is appropriate for gypsum contamination because caustic soda, NaOH, is not needed to raise pH. This is also generally the case with hard water influxes into water muds.
368acrylate polymer, calcium carbonate, carbonate ion, carbonate test, Garrett Gas Train, hardness ion, hydrolysis, phenolphthalein, prehydrated bentonite, seawater mud, sodium bicarbonate, soft water
369soda ash
370None
371--
372stoneley wave
3731.n. [Geophysics]
374A type of large-amplitude interface, or surface, wave generated by a sonic tool in a borehole. Stoneley waves can propagate along a solid-fluid interface, such as along the walls of a fluid-filled borehole and are the main low-frequency component of signal generated by sonic sources in boreholes. Analysis of Stoneley waves can allow estimation of the locations of fractures and permeability of the formation. Stoneley waves are a major source of noise in vertical seismic profiles.
375signal, sonic, surface wave, tube wave, vertical seismic profile, wave
376None
377None
378--
379salt
3801.n. [Geology]
381[NaCl]A soft, solubleevaporitemineralalso known as halite or rocksalt. Because salt is less dense than many sedimentary rocks, it is relatively buoyant and can form salt domes, pillars or curtains by flowing and breaking through or piercing overlying sediments, as seen in the Gulf of Mexico and the Zagros fold belt. Halite can be critical in forming hydrocarbon traps and seals because it tends to flow rather than fracture during deformation, thus preventing hydrocarbons from leaking out of a trap even during and after some types of deformation.
382cap rock, diapir, gypsum, rheology, salt dome, seal, subsalt
383halite
384None
385--
386salt
3872.n. [Drilling Fluids]
388The product formed by neutralization of an acid and a base. The term is more specifically applied to sodium chloride. Neutralization is an important reaction in many aspects of mud control and treatment.
389alkalinity, alkalinity test, caustic potash, caustic soda, fatty-acid soap, neutralization, pH, polar compound, saturated solution, titration
390None
391None
392--
393shoe joint
3941.n. [Drilling]
395Another term for float joint, a full-sized length of casing placed at the bottom of the casing string that is usually left full of cement on the inside to ensure that good cement remains on the outside of the bottom of the casing. If cement were not left inside the casing in this manner, the risk of overdisplacing the cement (due to improper casing volume calculations, displacement mud volume measurements, or both) would be significantly higher. Hence, the well designer plans on a safety margin of cement left inside the casing to guarantee that the fluid left outside the casing is good-quality cement. A float collar is placed at the top of the float joint and a float shoe placed at the bottom to prevent reverse flow of cement back into the casing after placement. There can be one, two or three joints of casing used for this purpose.
396casing string, displacement fluid, float collar, float joint, float shoe
397None
398None
399--
400sodium chromate
4011.n. [Drilling Fluids]
402A sodiumsalt, Na2CrO4, in which chromium atoms are in the plus-6 valence state. Chromium compounds of various types have been used inligniteandlignosulfonateand other mudadditives 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.
403chloride test, chromate salt, chrome lignite, chrome lignosulfonate, chrome-free, chromic salt, deflocculated mud, endpoint, indicator, redox
404None
405None
406--
407stopple
4081.n. [Production]
409A procedure used in the repair of a pipeline to isolate a section of line in the absence of a shutoff valve. After welding a flanged saddle to the pipe, the line is hot tapped—a method of making a connection to existing piping or pressure vessels without the interruption of emptying that section of pipe or vessel—and an expanding resilient plug is inserted into the pipe bore. When the repair is completed, the plug is withdrawn and a valve, installed on the saddle flange, is closed.
410None
411None
412None
413--
414salt plug
4151.n. [Well Completions]
416A temporary plugging agent comprising graded granules of salt that form a physical or hydraulic barrier. The different grain sizes are prepared as a slurry for placement, then allowed to settle into a plug. The resulting plug typically provides good mechanical and hydraulic strength to enable safe treatment of an adjacent zone. On completion of the treatment, the temporary salt plug is easily removed by circulating a water-base fluid to dissolve the plug.
417None
418None
419None
420--
421shoe track
4221.n. [Drilling]
423Another term for float joint, a full-sized length of casing placed at the bottom of the casing string that is usually left full of cement on the inside to ensure that good cement remains on the outside of the bottom of the casing. If cement were not left inside the casing in this manner, the risk of overdisplacing the cement (due to improper casing volume calculations, displacement mud volume measurements, or both) would be significantly higher. Hence, the well designer plans on a safety margin of cement left inside the casing to guarantee that the fluid left outside the casing is good-quality cement. A float collar is placed at the top of the float joint and a float shoe placed at the bottom to prevent reverse flow of cement back into the casing after placement. There can be one, two or three joints of casing used for this purpose.
424casing string, displacement fluid, float collar, float shoe
425float joint
426None
427--
428shoe track
4292.n. [Well Completions]
430Another term for float joint, a full-sized length of casing placed at the bottom of the casing string that is usually left full of cement on the inside to ensure that good cement remains on the outside of the bottom of the casing. If cement were not left inside the casing in this manner, the risk of overdisplacing the cement (due to improper casing volume calculations, displacement mud volume measurements, or both) would be significantly higher. Hence, the well designer plans on a safety margin of cement left inside the casing to guarantee that the fluid left outside the casing is good-quality cement. A float collar is placed at the top of the float joint and a float shoe placed at the bottom to prevent reverse flow of cement back into the casing after placement. There can be one, two or three joints of casing used for this purpose.
431float collar, guide shoe
432None
433None
434--
435sodium polyacrylate
4361.n. [Drilling Fluids]
437Made by neutralizing a linear,anionicpolymermade from themonomeracrylicacid, CH2=CHCOO- H+, with sodium hydroxide (NaOH). Sodium polyacrylate is often abbreviated to SPA. Polyacrylates are best utilized in soft water with low salinity to achieve the bestdispersionand full chain elongation. Even low concentrations of hardness ions, for example, Ca+2,precipitatepolyacrylates. Low molecular-weight polyacrylates are used asclaydeflocculants. High molecular weight polymers are used forfluid-loss controland as aclay extender. As an extender, SPA is added tobentoniteat the grinding plant. It is also used at theriginlow-solids mud. Divalent cations can negate its benefits as a clay extender. SPA is highly efficient when used to flocculatecolloids in native-solids muds, clear-water muds andwastewater cleanup. The polymer chain links togethercolloidal solidsthat can be removed by gravity settling in shallow pits or by applyinghydrocyclone,centrifugeor filtrationtechniques.
438acrylamide-acrylate polymer, acrylate polymer, anion, calcium contamination, clear-water drilling, deflocculant, deflocculated mud, flocculant, hardness ion, low-solids, nondispersed mud, native-solids mud, peptized clay, peptizing agent, PHPA mud, polyacrylate, potassium mud, sodium bicarbonate, sodium carbonate, soft water, vinyl polymer, water clarification
439None
440SPA
441--
442storm packer
4431.n. [Well Completions]
444A heavy-duty retrievable packer assembly that can be run in to isolate the wellbore of a new well in the event of suspended activities, for example, during a severe storm. An on-off disconnect feature enables the storm packer to be set at a safe depth while using the weight of the string below the packer to maintain the set and hang off the drillstring to avoid pulling all the way out of the hole.
445None
446None
447None
448--
449salt proximity survey
4501.n. [Geophysics]
451A type of refraction survey to help define a salt-sediment interface near a wellbore. The source is typically placed directly above the top of a salt dome and the receivers are placed at a number of locations within the borehole. This technique takes advantage of the fact that sound travels faster through the salt than the surrounding soft sediments, such as in the US Gulf Coast. This survey measures the fastest travel path, with part of its path through the salt. The resultant traveltimes are then inverted via a model to obtain a profile of the salt flanks relative to the borehole.
452radial refraction, refraction, salt-proximity vertical seismic profile, source, survey
453None
454None
455--
456shoot a well
4571.vb. [Geophysics]
458To acquire a type ofborehole seismic datadesigned to measure the seismictraveltimefrom the surface to a known depth. P-wavevelocityof the formations encountered in a wellbore can be measured directly by lowering ageophoneto eachformationof interest, sending out a source of energy from the surface of the Earth, and recording the resultantsignal. The data can then be correlated to surface seismic data by correcting thesonic logand generating a syntheticseismogramto confirm or modify seismic interpretations. It differs from avertical seismic profilein the number and density ofreceiverdepths 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.
459check-shot survey, depth conversion, drift, first break, one-dimensional seismic data, one-way time
460None
461None
462--
463shoot a well
4642.vb. [Perforating]
465To perforate a wellbore in preparation for production.
466perforation
467None
468None
469--
470soft line
4711.n. [Drilling]
472Oilfield slang term for rope not made of steel, such as nylon, cotton, or especially standard manila hemp rope.
473None
474None
475softline
476--
477strain
4781.n. [Geology]
479The permanent deformation evident in rocks and other solid bodies that have experienced a sufficiently high applied stress. A change in shape, such as folding, faulting, fracturing, or change, generally a reduction, in volume are common examples of strain seen in rocks. Strain can be described in terms of normal and shear components, and is the ratio of the change in length or volume to the initial length or volume.For more on strain: Means WD: Stress and Strain. New York, New York, Springer-Verlag, 1976.
480fault, fold, fracture, rock, shear strain, stress
481None
482None
483--
484saltwater flow
4851.n. [Drilling Fluids]
486An influx of formation water, usually salty and sometimes hard, into the mud in the wellbore. Saltwater flows contaminate freshwater or seawater muds, making it expensive, difficult and time-consuming to regain the mud properties. Influxes pose a lesser problem for saltwater muds. Saltwater contamination flocculates the bentonite clay in fresh- or seawater muds. Flocculated, thick, filter cake on a permeable zone frequently results in differential-pressure sticking.
487bentonite, clay-water interaction, differential pressure sticking, flocculation, saltwater mud, seawater mud
488None
489None
490--
491short trip
4921.n. [Drilling]
493An abbreviated recovery of pipe out of, and then the replacement of same back into the wellbore. Such a trip is normally limited to 10 or 20 stands of drillpipe. Since the short trip is drillpipe only (no bottomhole assembly for the drilling crew to handle), and is limited in length, it can be accomplished quickly and sometimes results in additional information or improved operating conditions. A short trip often is used to gauge whether a hole is clean or whether the mud weight is sufficient to permit a full trip out of the hole.
494bottomhole assembly, stand, wiper trip
495None
496None
497--
498softline
4991.n. [Drilling]
500Oilfield slang term for rope not made of steel, such as nylon, cotton, or especially standard manila hemp rope.
501cathead
502None
503None
504--
505streamer
5061.n. [Geophysics]
507A surface marine cable, usually a buoyant assembly of electrical wires that connects hydrophones and relays seismic data to the recording seismic vessel. Multistreamer vessels tow more than one streamer cable to increase the amount of data acquired in one pass.
508acoustic positioning, bird, cable, depth controller, eel, footprint, hydrophone, ocean-bottom cable, streamer feathering, tail buoy
509None
510None
511--
512saltwater mud
5131.n. [Drilling Fluids]
514A water mud containing varying amounts of dissolved sodium chloride, NaCl, as a major component. Undissolved salt may also be present in saturated salt muds to increase density beyond 10 lbm/gal or to act as a bridging agent over permeable zones. Starch and starch derivatives for fluid-loss control and xanthan gums for hole-cleaning are among the few highly effective additives for saltwater muds. Attapulgite and sepiolite are used in saltwater muds only for cuttings lifting. The primary use of saltwater mud is to drill salt strata that are prone to dissolution when exposed to other types of drilling fluid. A saturated salt mud is used to drill salt to prevent hole enlargement. In hot, plastic, salt zones, the hole may close inward unless extremely high mud weight is maintained. As an alternative to high mud weight, maintaining undersaturation in the fluid allows controlled leaching to offset hole closure by plastic flow. Sized salt particles in saturated saltwater muds are used, along with polymers, to bridge over permeable production zones. The salt can be removed later with a water flush. Salt solids can increase density beyond 10 lbm/gal, up to about 13 lbm/gal, if needed.
515carrying capacity, chloride test, drilling fluid, hydroxypropyl starch, saltwater flow, sized salt, starch, undersaturated fluid, water-base drilling fluid, XC polymer
516HE starch
517None
518--
519short path multiple
5201.n. [Geophysics]
521Multiply-reflected seismic energy with a shorter travel path than long-path multiples. Short-path multiples tend to come from shallow subsurface phenomena or highly cyclical sedimentation and arrive soon after, and sometimes very near, the primary reflections. Short-path multiples are less obvious than most long-path multiples and are less easily removed by seismic processing.
522event, ghost, long-path multiple, multiple reflection, noise, peg-leg multiple, primary reflection, processing
523None
524None
525--
526solar terrestrial rhythms
5271.n. [Reservoir Characterization]
528The periodicities in the behavior of the Earth and its climate with respect to the sun. Some rhythms are caused by variations in the elliptically of the Earth's orbit, rotation of the semimajor axis of the Earth's orbit, variation on the tilt of the Earth's axis and rotation in the tilt of the Earth's axis. Most of these rhythms are predictable over the short term (up to hundreds of millions of years) but can become chaotic due to the influence of other planets (particularly massive Jupiter) or extra solar-system activity. The rhythms affect sea level and other factors that dictate the long-term behavior of depositional systems.
529None
530None
531None
532--
533stress
5341.n. [Geology]
535The force applied to a body that can result in deformation, or strain, usually described in terms of magnitude per unit of area, or intensity.
536earthquake, elastic, elastic deformation, elastic limit, shear strain, strain
537None
538None
539--
540sand
5411.n. [Geology]
542A detrital grain between 0.0625 mm and 2 mm in diameter. Sand is larger than silt but smaller than a granule according to the Udden-Wentworth scale. Sand is also a term used for quartz grains or for sandstone.
543arenaceous, detrital, fairway, pay, point bar, quartz, sandstone, tar sand, Udden-Wentworth scale
544None
545None
546--
547sand
5482.n. [Drilling Fluids]
549A category of size used to describe particles in a mud that will not pass through a 200-mesh screen (74 micrometers and larger).
550fines, sand test, silt
551None
552None
553--
554sand
5553.n. [Well Completions]
556A generic term used to describe small formation particles known as fines that may be produced with the reservoir fluid. Sand production generally is undesirable and, if severe, may require some remedial action to control or prevent production, such a gravel packing or sand consolidation.
557None
558None
559None
560--
561shot detection
5621.n. [Perforating]
563A surface detection technique to verify that perforating guns have fired. This technique typically employs sensors that detect vibration or hydraulic shock at surface, and is used with TCP operations.
564perforating gun, tubing-conveyed perforating
565None
566None
567--
568solubility
5691.n. [Enhanced Oil Recovery]
570The maximum amount of a substance that will dissolve in a given amount of solvent at a given temperature and pressure, or the degree to which a substance will dissolve in a particular solvent. The solubility of a substance is its concentration in a saturated solution. Two fluids that are soluble in one another in all proportions are also referred to as miscible.
571miscible
572None
573None
574--
575stress corrosion cracking
5761.n. [Drilling Fluids]
577A form of corrosion in which susceptible types of metals will break by a combination of stress within the metal and the specific type of corrosion. Sulfide corrosion of ferrous alloys and chloride corrosion of stainless steels are two common type of SCC. When high-strength steel remains in contact with hydrogen sulfide (or sulfide ion) in a water-mud environment, sulfide SCC may occur. Tool joints, hardened parts of blowout preventers and valve trim are particularly susceptible to brittle failure caused by sulfide SCC. For this reason, along with toxicity risks of hydrogen sulfide gas, it is essential that water muds be kept entirely free of soluble sulfides and especially hydrogen sulfide at low pH.
578blowout preventer, corrosion coupon, Garrett Gas Train, iron sulfide, scavenger, sulfide, sulfide scavenger
579None
580SCC, stress-corrosion cracking
581--
582sand bailer
5831.n. [Well Completions]
584A downhole device, usually run on slickline, used to remove sand or debris from the bottom of the wellbore. In operation, an atmospheric chamber within the tool is opened to create a surge of fluids into the chamber. Debris is then held within the chamber for recovery at surface.
585sand
586None
587None
588--
589sand bailer
5902.n. [Well Workover and Intervention]
591Another term for a hydrostatic bailer, a slickline tool generally used for the removal of sand or similar small particles around the fishing necks of downhole tools or equipment. The hydrostatic bailer incorporates a sealed atmospheric chamber and a shear pin, or similar activation mechanism, to allow communication with the wellbore. When the tool is activated, there is a fluid surge into the atmosphere as the pressure is equalized. A shroud arrangement at the base of the tool contains and directs the fluid surge to dislodge and capture any debris in the area.
592fishing neck, shear pin
593hydrostatic bailer
594None
595--
596sand bailer
5973.n. [Production Testing]
598A swabbing device used to clean up sand that has accumulated in the wellbore. Because sands abrasiveness is detrimental to the normal operation of production equipment, its production should be minimized. A sand bailer operates by creating a partial vacuum that sucks up the sand.
599None
600None
601None
602--
603show
6041.n. [Drilling]
605A surface observation of hydrocarbons, usually observed as florescent liquid on cuttings when viewed with an ultraviolet or black light (oil show) or increased gas readings from the mud logger's gas-detection equipment (gas show).
606gas show
607None
608None
609--
610sonde error
6111.n. [Formation Evaluation]
612The measurement of an induction tool in a nonconducting medium before correction. Electronic offsets and coupling within the tool cause a signal in the receivers even in a nonconducting medium such as air. This signal is cancelled either electronically or in software. Sonde errors change with temperature and pressure downhole. This can be allowed for by characterizing the sonde's response to temperature and pressure on the surface.Sonde error is measured by placing the tool far from the ground in air. Ideally measurements are made at two distances, since the ground signal can then be determined from the difference and eliminated. Originally, sonde error referred only to the R-signal, since this was the only signal being used. The term now refers to both R- and X-signals.
613calibration, R-signal, X-signal
614None
615None
616--
617stress induced anisotropy
6181.n. [Formation Evaluation]
619A situation in which theformationshear-wavevelocityvaries azimuthally around theborehole, because unequal stresses in the formation have caused azimuthal variations in thestress concentrations around the borehole. These stress concentrations change the shear-wave speeds in the region surrounding the well from those in the far field, such that a characteristic response is observed in the dispersion of thedipoleflexural mode.
620azimuthal, flexural mode, S-wave
621None
622None
623--
624sand consolidation
6251.n. [Well Completions]
626A means of controlling the undesirable production of sand from weak sandstone formations. Sand consolidation chemically binds the grains of sand that make up the formation matrix while maintaining sufficient permeability to achieve viable production rates.
627sand control
628None
629None
630--
631shrimp test
6321.n. [Drilling Fluids]
633A 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.
634bactericide, emulsion mud, EPA, LC50, Minerals Management Service, NPDES, potassium mud
635None
636None
637--
638sonic log
6391.n. [Geophysics]
640A type of acoustic log that displays traveltime of P-waves versus depth. Sonic logs are typically recorded by pulling a tool on a wireline up the wellbore. The tool emits a sound wave that travels from the source to the formation and back to a receiver.
641acoustic log, P-wave, sonic, traveltime, velocity
642None
643None
644--
645stress corrosion cracking
6461.n. [Drilling Fluids]
647A form of corrosion in which susceptible types of metals will break by a combination of stress within the metal and the specific type of corrosion. Sulfide corrosion of ferrous alloys and chloride corrosion of stainless steels are two common type of SCC. When high-strength steel remains in contact with hydrogen sulfide (or sulfide ion) in a water-mud environment, sulfide SCC may occur. Tool joints, hardened parts of blowout preventers and valve trim are particularly susceptible to brittle failure caused by sulfide SCC. For this reason, along with toxicity risks of hydrogen sulfide gas, it is essential that water muds be kept entirely free of soluble sulfides and especially hydrogen sulfide at low pH.
648blowout preventer, corrosion coupon, Garrett Gas Train, iron sulfide, scavenger, sulfide, sulfide scavenger
649None
650SCC, stress corrosion cracking
651--
652sand control
6531.n. [Well Completions]
654The installation of equipment or application of techniques to prevent migration of reservoir sand into the wellbore or near-wellbore area. In weak formations, sand control may be necessary to maintain the structure of the reservoir around the wellbore. In other formation types, the migration of sand and fines into the near wellbore area may severely restrict production. Each of these conditions requires different treatments. The principal sand-control techniques include gravel packing and sand consolidation.
655None
656None
657None
658--
659shut in pressure
6601.n. [Drilling]
661The surface force per unit area exerted at the top of a wellbore when it is closed at either the Christmas tree or the BOP stack. The pressure may be from the formation or an external and intentional source. The SIP may be zero, indicating that any open formations are effectively balanced by the hydrostatic column of fluid in the well. If the pressure is zero, the well is considered to be dead, and can normally be opened safely to the atmosphere.
662BOP stack, Christmas tree, hydrostatic pressure
663None
664SIP
665--
666sonic measurement
6671.n. [Formation Evaluation]
668A technique for recording the formation compressional slowness based on the transit time between transmitter and receiver. In the most basic wireline sonic measurement, an acoustic transducer emits a sonic signal, of between about 10 and 30 kHz, which is detected at two receivers farther up the hole. The time between emission and reception is measured for each receiver, and subtracted to give the traveltime in the interval between the two receivers. If the receivers are two feet apart, then this time is divided by two to give the interval transit time, or slowness, of the formation. This type of measurement is also known as first motion detection.This technique works because the first arrival at the receiver is a wave that has traveled from the transmitter to the borehole wall, where it has generated a compressional wave in the formation. Some of this wave is critically refracted up the borehole wall, generating head waves in the borehole fluid as it progresses. Some of these strike the receiver, arriving in most cases well before any signal traveling directly through the mud. Furthermore, if the logging tool is parallel to the borehole wall, the traveltime in the mud is cancelled by taking the difference between the traveltime to the two receivers. Problems of irregular hole or a tilted tool are avoided by using borehole compensation.The depth of investigation depends on the slowness, the transmitter-to-receiver spacing and the presence or absence of an altered zone. It is generally within the invaded zone, and of the order of several inches.
669acoustic transducer, altered zone, borehole compensation, delta-t stretch, depth of investigation, first break, head wave, interval transit time, invaded zone, long-spacing sonic log, monopole, P-wave, sonic log, ultrasonic measurement
670None
671None
672--
673sonic measurement
6742.n. [Formation Evaluation]
675The technique for recording a borehole sonic log, in the sense of measurement of any of the acoustic properties in and around the borehole. The standard sonic measurement, based on first motion detection, normally can be used only to determine formation compressional slowness. For all other sonic measurements, such as shear, flexural and Stoneley slownesses and amplitudes, it is necessary to record the full waveform using an array-sonic tool and process with a technique such as slowness-time coherence.
676acoustic mode, array sonic, flexural mode, slow formation, slowness-time coherence, sonic log, Stoneley wave
677None
678None
679--
680stress induced anisotropy
6811.n. [Formation Evaluation]
682A situation in which theformationshear-wavevelocityvaries azimuthally around theborehole, because unequal stresses in the formation have caused azimuthal variations in thestress concentrations around the borehole. These stress concentrations change the shear-wave speeds in the region surrounding the well from those in the far field, such that a characteristic response is observed in the dispersion of thedipoleflexural mode.
683azimuthal, flexural mode, S-wave
684None
685None
686--
687sand line
6881.n. [Well Workover and Intervention]
689A long cable, installed on most drilling and workover rigs, used when swabbing or bailing in the production tubing or wellbore tubulars. The sand line is typically stored and operated on a winch drum that is part of the rig drawworks. The sand line is capable of significantly higher tensile forces than slickline or electric wireline.
690None
691None
692None
693--
694side pocket mandrel
6951.n. [Well Completions]
696A completion component that is used to house gas-lift valves and similar devices that require communication with the annulus. The design of a side-pocket mandrel is such that the installed components do not obstruct the production flow path, enabling access to the wellbore and completion components below.
697gas lift
698None
699None
700--
701sorting
7021.n. [Geology]
703The range of sedimentary grain sizes that occurs in sediment or sedimentary rock. The term also refers to the process by which sediments of similar size are naturally segregated during transport and deposition according to the velocity and transporting medium. Well-sorted sediments are of similar size (such as desert sand), while poorly-sorted sediments have a wide range of grain sizes (as in a glacial till). A well-sorted sandstone tends to have greater porosity than a poorly sorted sandstone because of the lack of grains small enough to fill its pores. Conglomerates tend to be poorly sorted rocks, with particles ranging from boulder size to clay size.
704cubic packing, depositional energy, porosity, rhombohedral packing, sediment, Udden-Wentworth scale
705None
706None
707--
708strike fault
7091.n. [Reservoir Characterization]
710A fault whose primary movement is in the strike direction (usually horizontal). This type of fault is usually caused by continents or tectonic plates moving laterally with respect to each other, as is happening in California today. The San Andreas fault is a strike-slip fault along which the western side is moving north relative to the eastern side.
711strike-slip fault
712None
713None
714--
715sand production
7161.n. [Well Completions]
717The migration of formation sand caused by the flow of reservoir fluids. The production of sand is generally undesirable since it can restrict productivity, erode completion components, impede wellbore access, interfere with the operation of downhole equipment, and present significant disposal difficulties.
718None
719None
720None
721--
722side scan sonar
7231.n. [Geophysics]
724A system for acoustic surveying most commonly deployed in marine environments and towed by a ship. The side-scan sonar generates a pulse on the order of 30 to 120 kHz that is reflected from the seafloor. Side-scan sonar records yield an image of the seafloor and shallow sediments.
725acoustic, deep tow, survey
726None
727None
728--
729sour
7301.adj. [Geology]
731Contaminated with sulfur or sulfur compounds, especially hydrogen sulfide. Crude oil and gas that are sour typically have an odor of rotten eggs if the concentration of sulfur is low. At high concentrations, sulfur is odorless and deadly.
732hydrogen sulfide
733None
734Antonyms:sweet
735--
736strike slip fault
7371.n. [Geology]
738A type of fault whose surface is typically vertical or nearly so. The motion along a strike-slip fault is parallel to the strike of the fault surface, and the fault blocks move sideways past each other. A strike-slip fault in which the block across the fault moves to the right is described as a dextral strike-slip fault. If it moves left, the relative motion is described as sinistral. Local deformation near bends in strike-slip faults can produce pull-apart basins and grabens. Flower structures are another by-product of strike-slip faults. A wrench fault is a type of strike-slip fault in which the fault surface is nearly vertical.
739basin, fault, flower structure, graben, graben, offset, strike, transform fault, transpression, transtension, wrench fault
740None
741None
742--
743sand trap
7441.n. [Drilling Fluids]
745A small pit, typically located immediately after the shaker screens, which is used as a settling pit to separate coarser solids that accidentally bypass the shakers. Mud enters the pit at one side and exits via an overflow at the other. Sand traps are dumped periodically to remove the settled solids, or alternatively the contents can be processed over a fine screen or with a centrifuge.
746None
747None
748None
749--
750side pocket mandrel
7511.n. [Well Completions]
752A completion component that is used to house gas-lift valves and similar devices that require communication with the annulus. The design of a side-pocket mandrel is such that the installed components do not obstruct the production flow path, enabling access to the wellbore and completion components below.
753gas lift
754None
755None
756--
757sour gas
7581.n. [Drilling Fluids]
759A general term for those gases that are acidic either alone or when associated with water. Two sour gases associated with oil and gas drilling and production are hydrogen sulfide, H2S, and carbon dioxide, CO2. Sulfur oxides and nitrogen oxides, generated by oxidation of certain sulfur- or nitrogen-bearing materials, are also in this category but not found in the anaerobic conditions of the subsurface.
760anaerobic, carbon dioxide, carbonate, hydrogen sulfide, sulfate-reducing bacteria, sulfide
761None
762Antonyms:sweet gas
763--
764sour gas
7652.n. [Production Testing]
766A gas containing hydrogen sulfide, carbon dioxide or mercaptans, all of which are extremely harmful.
767None
768None
769None
770--
771stripper rubber
7721.n. [Well Workover and Intervention]
773The sealing element used in coiled tubing or snubbing stripper systems. The stripper element is a consumable product and generally should be replaced for each operation. Coiled tubing elements can be replaced with the tubing in place, enabling a worn or leaking element to be replaced during an operation. Snubbing stripper rubbers are of single-piece construction and cannot be changed with the work string in place.
774work string
775None
776None
777--
778sandstone compatible scale
7791.n. [Formation Evaluation]
780Display ranges chosen for the density and neutron porosity logs such that the two curves will overlay at all porosity values providing the matrix is pure quartz and the pores are filled with fresh water. The most common overlay spans two tracks, with the density reading from 1.9 to 2.9 g/cm3, and the neutron in sandstone porosity units from 0.45 to −0.15 vol/vol.
781limestone porosity unit, limestone-compatible scale, neutron porosity, sandstone porosity unit
782None
783None
784--
785side scan sonar
7861.n. [Geophysics]
787A system for acoustic surveying most commonly deployed in marine environments and towed by a ship. The side-scan sonar generates a pulse on the order of 30 to 120 kHz that is reflected from the seafloor. Side-scan sonar records yield an image of the seafloor and shallow sediments.
788acoustic, deep tow, survey
789None
790None
791--
792source rock
7931.n. [Geology, Geochemistry, Shale Gas]
794A rock rich in organic matter which, if heated sufficiently, will generate oil or gas. Typical source rocks, usually shales or limestones, contain about 1% organic matter and at least 0.5% total organic carbon (TOC), although a rich source rock might have as much as 10% organic matter. Rocks of marine origin tend to be oil-prone, whereas terrestrial source rocks (such as coal) tend to be gas-prone. Preservation of organic matter without degradation is critical to creating a good source rock, and necessary for a complete petroleum system. Under the right conditions, source rocks may also be reservoir rocks, as in the case of shale gas reservoirs.
795argillaceous, basin, bitumen, coal, critical moment, generation, geochemistry, hydrocarbon, hydrocarbon kitchen, immature, kerogen, lacustrine, limestone, marine, maturity, migration, natural gas, overmature, petroleum system, pinch-out, pinch-out, play, post-mature, primary migration, prospect, pyrolysis, secondary migration, sedimentary basin, sequence stratigraphy, shale, swamp, vitrinite, vitrinite reflectance
796None
797None
798--
799stripping
8001.n. [Drilling]
801The act of putting drillpipe into the wellbore when the blowout preventers (BOPs) are closed and pressure is contained in the well. This is necessary when a kick is taken, since well kill operations should always be conducted with the drillstring on bottom, and not somewhere up the wellbore. If only the annular BOP has been closed, the drillpipe may be slowly and carefully lowered into the wellbore, and the BOP itself will open slightly to permit the larger diameter tool joints to pass through. If the well has been closed with the use of ram BOPs, the tool joints will not pass by the closed ram element. Hence, while keeping the well closed with either another ram or the annular BOP, the ram must be opened manually, then the pipe lowered until the tool joint is just below the ram, and then the ram closed again. This procedure is repeated whenever a tool joint must pass by a ram BOP. Rig crews are usually required to practice ram-to-ram and ram-to-annular stripping operations as part of their well control certifications. In stripping operations, the combination of the pressure in the well and the weight of the drillstring is such that the pipe falls in the hole under its own weight, whereas in snubbing operations the pipe must be pushed into the hole.
802annular blowout preventer, ram blowout preventer, snubbing, tool joint
803None
804None
805--
806stripping
8072.n. [Well Workover and Intervention]
808The running or retrieving of a tubing string in a well under pressure, using a stripper or similar sealing device to contain well pressure and fluids. Coiled tubing, snubbing and some specialized workover rig operations can be conducted on live wells using special sealing equipment to safely and reliably contain wellbore pressure and fluids. Well-intervention systems designed to operate on live wells incorporate a secondary or contingency means of isolating wellbore pressure.
809None
810None
811None
812--
813sandstone porosity unit
8141.n. [Formation Evaluation]
815A transform from raw log data chosen so that a log recorded in these units will give the correct porosity of the formation providing the matrix is pure quartz and the pores are filled with fresh water. The unit, which may be in vol/vol or p.u., is most commonly used for neutron porosity logs but may also be used for density and acoustic logs. The definition is strictly true only if all borehole and other environmental corrections have been applied.
816limestone porosity unit, limestone-compatible scale, neutron porosity, sandstone-compatible scale
817None
818None
819--
820sidetrack
8211.vb. [Drilling]
822To drill a secondary wellbore away from an original wellbore. A sidetracking operation may be done intentionally or may occur accidentally. Intentional sidetracks might bypass an unusable section of the original wellbore or explore a geologic feature nearby. In the bypass case, the secondary wellbore is usually drilled substantially parallel to the original well, which may be inaccessible due to an irretrievable fish, junk in the hole, or a collapsed wellbore.
823fish, junk
824None
825None
826--
827sidetrack
8282.n. [Drilling]
829A secondary wellbore drilled away from the original hole. It is possible to have multiple sidetracks, each of which might be drilled for a different reason.
830multilateral
831None
832None
833--
834soxhlet extractor
8351.n. [Formation Evaluation]
836An apparatus for cleaning core samples using the distillation extraction method. In the Soxhlet apparatus (also called extractor, or chamber), the sample soaks in hot solvent that is periodically siphoned off, distilled and returned to the sample. The process continues until the siphoned-off solvent becomes clear. In the Soxhlet apparatus, the sample soaks in the solvent, while in the Dean-Stark apparatus, the solvent flows through the sample from top to bottom.
837centrifuge, Dean-Stark extraction, distillation extraction
838None
839None
840--
841stroke
8421.n. [Production Testing]
843In a sucker-rod pump, one complete round of the polished rod (surface stroke). On each stroke, a fixed volume of liquid is lifted. This volume is related to the cross-sectional area of the pump and the length of the stroke.The stroke length at the subsurface sucker-rod pump usually differs from the surface stroke because of the stretching in the upstroke and the rebounding in the downstroke.
844rod pump
845None
846None
847--
848sandstone compatible scale
8491.n. [Formation Evaluation]
850Display ranges chosen for the density and neutron porosity logs such that the two curves will overlay at all porosity values providing the matrix is pure quartz and the pores are filled with fresh water. The most common overlay spans two tracks, with the density reading from 1.9 to 2.9 g/cm3, and the neutron in sandstone porosity units from 0.45 to −0.15 vol/vol.
851limestone porosity unit, limestone-compatible scale, neutron porosity, sandstone porosity unit
852None
853None
854--
855sidewall
8561.adj. [Formation Evaluation]
857Relating to being held against, or taken from, the side of the borehole. The term also describes a measurement that must be made by pressing the sonde against the side of the borehole in order to minimize borehole effects, as, for example, a sidewall epithermal neutron log.
858pad, sidewall core
859None
860None
861--
862sp
8631.n. [Geophysics]
864One of a number of locations or stations at the surface of the Earth at which a seismic source is activated.
865acquisition, amplitude variation with offset, common midpoint method, depth migration, dropout, fold, migration, offset, receiver, seismic record, seismogram, shot depth, spacing, spread, synthetic seismogram
866None
867None
868--
869sp
8702.n. [Geophysics]
871Naturally occurring (static) electrical potential in the Earth. Spontaneous potentials are usually caused by charge separation in clay or other minerals, by the presence of a semipermeable interface impeding the diffusion of ions through the pore space of rocks, or by natural flow of a conducting fluid (salty water) through the rocks. Variations in SP can be measured in the field and in wellbores to determine variations of ionic concentration in pore fluids of rocks.
872None
873None
874spontaneous potential
875--
876sp
8773.n. [Formation Evaluation]
878An abbreviation of spontaneous potential.
879None
880None
881spontaneous potential
882--
883structural
8841.adj. [Geology]
885Pertaining to structure, the geometry and spatial arrangement of rocks. The structure or deformation can include many mechanisms, such as folding, faulting and fracturing. Structure can usually be interpreted in terms of the deformation of thecrustof the Earth as continents and tectonic plates move and collide.
886anticlinal trap, anticline, closure, crest, crust, diapir, differential compaction, drape, en echelon, fault, fold, fracture, geologic map, harmonic, inversion, orogeny, plate tectonics, prospect, spill point, stratigraphy, structural trap, structure, structure map, syncline, trap
887None
888None
889--
890sara analysis
8911.n. [Heavy Oil]
892A method for characterization of heavy oils based on fractionation, whereby a heavy oil sample is separated into smaller quantities or fractions, with each fraction having a different composition. Fractionation is based on the solubility of hydrocarbon components in various solvents used in this test. Each fraction consists of a solubility class containing a range of different molecular-weight species. In this method, the crude oil is fractionated to four solubility classes, referred to collectively as SARA: saturates, aromatics, resins, and asphaltenes. Saturates are generally iso- and cyclo-paraffins, while aromatics, resins, and asphaltenes form a continuum of molecules with increasing molecular weight, aromaticity, and heteroatom contents. Asphaltenes may also contain metals such as nickel and vanadium. This method is sometimes referred to as Asphaltene/Wax/Hydrate Deposition analysis.
893None
894None
895None
896--
897sidewall core
8981.n. [Formation Evaluation]
899A core taken from the side of the borehole, usually by a wireline tool. Sidewall cores may be taken using percussion or mechanical drilling. Percussion cores are taken by firing hollow bullets into the formation. The bullets are attached to the tool by fasteners, and are retrieved, along with the core inside, by pulling up the tool and the fasteners. Percussion coring tools typically hold 20 to 30 bullets, but two or three tools can be combined on one run in the hole. Mechanical tools use hollow rotary drills to cut and then pull out core plugs. Up to 75 plugs can be recovered on one run. With full recovery, cores from typical percussion tools are 1 in. [2.5 cm] in diameter by 1 3/4 in. [4.4 cm] long, while those from mechanical tools are 0.91 in. [2.3 cm] in diameter by 2 in. [5 cm] long. The latter are also known as rotary sidewall cores.
900core plug, whole core
901None
902None
903--
904spa
9051.n. [Drilling Fluids]
906Abbreviation for sodium polyacrylate. SPA is the result of neutralizing a linear,anionicpolymermade from themonomeracrylicacid,CH2=CHCOO- H+, with sodium hydroxide (NaOH).Polyacrylates are best utilized in soft water with low salinity to achieve the bestdispersionand full chain elongation. Even low concentrations of hardness ions, for example, Ca+2, precipitatepolyacrylates. Low molecular-weight polyacrylates are used asclaydeflocculants. High molecular weight polymers are used forfluid-loss controland as aclay extender. As an extender, SPA is added tobentoniteat the grinding plant. It is also used at theriginlow-solids mud. Divalent cations can negate its benefits as a clay extender. SPA is highly efficient when used to flocculatecolloids in native-solids muds, clear-water muds andwastewater cleanup. The polymer chain links togethercolloidal solidsthat can be removed by gravity settling in shallow pits or by applyinghydrocyclone,centrifugeor filtrationtechniques.
907acrylamide polymer, acrylamide-acrylate polymer, acrylate polymer, anion, calcium contamination, clear-water drilling, deflocculant, deflocculated mud, flocculant, hardness ion, low-solids, nondispersed mud, native-solids mud, peptized clay, peptizing agent, PHPA mud, polyacrylate, potassium mud, sodium bicarbonate, sodium carbonate, soft water, vinyl polymer, water clarification
908None
909sodium polyacrylate
910--
911structural analysis
9121.n. [Reservoir Characterization]
913An examination of a geological scenario to understand the geometry and spatial arrangement of rocks. The structure or deformation can include many mechanisms, such as folding, faulting and fracturing. Structure can usually be interpreted in terms of the deformation of the crust of the Earth as continents and tectonic plates move and collide.
914stratigraphy, structure
915None
916None
917--
918saturation
9191.n. [Geology]
920The relative amount of water, oil and gas in the pores of a rock, usually as a percentage of volume.
921effective permeability, permeability, pore, porosity, relative permeability, undersaturated fluid
922None
923None
924--
925sieve analysis
9261.n. [Well Completions]
927The process of analyzing the size distribution of a sand or gravel sample. In sand-control applications, a sample of formation sand is shaken through a series of sieves of known size. The resulting distribution is then used to design an appropriate treatment that will retain the sand, while causing a minimal restriction to production.
928None
929None
930None
931--
932sieve analysis
9332.n. [Formation Evaluation]
934A technique for analyzing the grain-size distribution of a core sample. A cleaned, weighed core sample is disaggregated and agitated through a series of stacked screens with progressively smaller openings. The material left on each screen is weighed in order to give a distribution of quantity versus sieve size. Sieve analysis may be done dry, wet or a combination of both. Wet analysis is necessary for analyzing any clay fraction.
935laser diffraction
936None
937None
938--
939space out
9401.vb. [Well Completions]
941To assemble components to ensure that all critical length dimensions are met, as is required to ensure that the production tubing can be landed in the wellhead and production packer with the desired weight distribution. The term also may apply to surface pressure-control equipment offshore, where well intervention equipment may be required at certain deck levels.
942production packer, production tubing
943None
944None
945--
946structural steering
9471.n. [Drilling]
948Structural steering is a method of directing the wellbore trajectory of horizontal wells using 3D visualization. It is the process of combining structural analysis and modeling capabilities with borehole images to optimize well placement, often in real-time. Structural steering integrates deep-reading LWD resistivity tools and high-resolution imaging devices to create structural models of often complex geologic conditions encountered by the drill bit. This technique helps operators understand the formations already drilled and allows them proactively to correct wellbore trajectories for anticipated changes.
949deviated drilling, directional drilling, directional well, geosteering, horizontal drilling, logging while drilling, LWD
950None
951None
952--
953saturation equation
9541.n. [Formation Evaluation]
955An equation for calculating the water saturation from resistivity and other logs. There are many saturation equations. Practical equations are all extensions of the Archie equation, which is valid for a rock with very little clay, or very high salinity water, and with a regular pore structure. The majority deal with the problem of shaly sands, and can be divided into two main groups?those that treat the shale as a volume of conductive material (Vsh models), and those that analyze the effect of clay counter-ions. Vsh models take many forms. Typical examples are the Simandoux, laminated sand and Indonesian equations. The other group includes the Waxman-Smits, Dual Water and SGS equations. Most nonshaly sand equations deal with the problem of mixed pore types, for example combinations of fractures, isolated pores and intergranular pores.
956isolated porosity
957None
958None
959--
960sigma
9611.n. [Formation Evaluation]
962The macroscopic cross section for the absorption of thermal neutrons, or capture cross section, of a volume of matter, measured in capture units (c.u.). Sigma is also used as an adjective to refer to a log of this quantity. Sigma is the principal output of the pulsed neutron capture log, which is mainly used to determine water saturation behind casing. Thermal neutrons have about the same energy as that of the surrounding matter, typically less than 0.4 eV.
963neutron capture, time-lapse
964None
965None
966--
967spacer fluid
9681.n. [Drilling]
969Any liquid used to physically separate one special-purpose liquid from another. Special-purpose liquids are typically prone to contamination, so a spacer fluid compatible with each is used between the two. The most common spacer is simply water. However, chemicals are usually added to enhance its performance for the particular operation. Spacers are used primarily when changing mud types and to separate mud from cement during cementing operations. In the former, an oil-base fluid must be kept separate from a water-base fluid. In this case, the spacer may be base oil. In the latter operation, a chemically treated water spacer usually separates drilling mud from cement slurry. For proper performance and to prevent unanticipated problems, the spacer should be tested with each fluid in small-scale pilot tests. Some spacer fluids are designed to induce a particular flow regime. Ideally, a cement slurry should have turbulent flow to efficiently displace drilling fluids, but there might be pumping restrictions on fluid velocity. Therefore, a spacer that can achieve turbulent or pseudolaminar flow might be selected.
970cement head, displacement
971None
972None
973--
974structure
9751.n. [Geology]
976A geological feature produced by deformation of the Earth's crust, such as a fold or a fault; a feature within a rock, such as a fracture or bedding surface; or, more generally, the spatial arrangement of rocks.
977anticlinal trap, anticline, closure, closure, crest, crust, diapir, differential compaction, drape, en echelon, fault, fold, fracture, geologic map, harmonic, inversion, inversion, orogeny, plate tectonics, prospect, spill point, structural trap, structure map, syncline, trap
978None
979structural
980--
981saturation exponent
9821.n. [Formation Evaluation]
983The 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 the resistivity 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 particular reservoir 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 as shaly 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 the clay effects removed. The variation of I with Sw is then predicted, with varying success, by the different equations.In carbonates with multiple pore types, such as fractures, vugs, interparticle porosity 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.
984None
985None
986None
987--
988signal
9891.n. [Geophysics]
990The portion of the seismic wave that contains desirable information. Noise is the undesirable information that typically accompanies the signal and can, to some extent, be filtered out of the data.
991acoustic coupler, acquisition, aliasing, autocorrelation, bel, check-shot survey, coupling, decibel, dynamic range, filter, filter, frequency, inversion, noise, polarity standard, processing, signal-to-noise ratio, Stoneley wave, traveltime, zero crossing
992None
993None
994--
995spacing unit
9961.n. [Oil and Gas Business]
997An area allotted to a well by regulations or field rules issued by a governmental authority having jurisdiction for the drilling and production of a well.
998communitization, proration unit, unitization
999None
1000None
1001--
1002structure map
10031.n. [Geology]
1004A type of subsurface map whose contours represent the elevation of a particular formation, reservoir or geologic marker in space, such that folds, faults and other geologic structures are clearly displayed. Its appearance is similar to that of a topographic map, but a topographic map displays elevations of the Earth's surface and a structure map displays the elevation of a particular rock layer, generally beneath the surface.
1005contour, contour interval, contour map, depth map, formation, structure, topographic map
1006None
1007None
1008--
1009saver sub
10101.n. [Drilling]
1011A short length of drill collar that has male threads on one end and female on the other. It is screwed onto the bottom of the kelly or topdrive and onto the rest of the drillstring. When the hole must be deepened, and pipe added to the drillstring, the threads are unscrewed between the saver sub and the rest of the drillstring, as opposed to between the kelly or topdrive and the saver sub. This means that the connection between the kelly or topdrive and the saver sub rarely is used, and suffers minimal wear and tear, whereas the lower connection is used in almost all cases and suffers the most wear and tear. The saver sub is expendable and does not represent a major investment. However, the kelly or topdrive component threads are spared by use of a saver sub, and those components represent a significant capital cost and considerable downtime when replaced.
1012drill collar, kelly, slips, topdrive
1013None
1014None
1015--
1016signal to noise ratio
10171.n. [Geophysics]
1018The ratio of desirable to undesirable (or total) energy. The signal-to-noise ratio can be expressed mathematically as S/N or S/(S+N), although S/N is more commonly used. The signal-to-noise ratio is difficult to quantify accurately because it is difficult to completely separate signal from noise. It also depends on how noise is defined.
1019filter, inversion, noise, signal, stack, stacking velocity
1020None
1021None
1022--
1023spectral
10241.adj. [Geophysics]
1025Pertaining to a spectrum. The spectral content of a wavetrain or wavelet usually refers to its amplitude and phase as a function of frequency.
1026amplitude, frequency, phase, wavelet
1027None
1028None
1029--
1030stuck
10311.adj. [Drilling]
1032Referring to the varying degrees of inability to move or remove the drillstring from the wellbore. At one extreme, it might be possible to rotate the pipe or lower it back into the wellbore, or it might refer to an inability to move the drillstring vertically in the well, though rotation might be possible. At the other extreme, it reflects the inability to move the drillstring in any manner. Usually, even if the stuck condition starts with the possibility of limited pipe rotation or vertical movement, it will degrade to the inability to move the pipe at all.
1033stuck pipe
1034None
1035None
1036--
1037scale removal
10381.n. [Enhanced Oil Recovery]
1039A common well-intervention operation involving a wide variety of mechanical scale-inhibitor treatments and chemical options. Mechanical removal is done by means of a pig or by abrasive jetting that cuts scale but leaves the tubing untouched. Scale-inhibition treatments involve squeezing a chemical inhibitor into a water-producing zone for subsequent commingling with produced fluids, preventing further scale precipitation. Chemical removal is performed with different solvents according to the type of scale:·	Carbonate scales such as calcium carbonate or calcite [CaCO3] can be readily dissolved with hydrochloric acid [HCl] at temperatures less than 250oF [121oC].·	Sulfate scales such as gypsum [CaSO4·2H2O] or anhydrite [CaSO4] can be readily dissolved using ethylenediamine tetraacetic acid (EDTA). The dissolution of barytine [BaSO4] or strontianite [SrSO4] is much more difficult.·	Chloride scales such as sodium chloride [NaCl] are easily dissolved with fresh water or weak acidic solutions, including HCl or acetic acid.·	Iron scales such as iron sulfide [FeS] or iron oxide [Fe2O3] can be dissolved using HCl with sequestering or reducing agents to avoid precipitation of by-products, for example iron hydroxides and elemental sulfur.·	Silica scales such as crystallized deposits of chalcedony or amorphous opal normally associated with steamflood projects can be dissolved with hydrofluoric acid [HF].
1040damage, precipitate, scale, scale inhibitor, scraper
1041None
1042None
1043--
1044signal to noise ratio
10451.n. [Geophysics]
1046The ratio of desirable to undesirable (or total) energy. The signal-to-noise ratio can be expressed mathematically as S/N or S/(S+N), although S/N is more commonly used. The signal-to-noise ratio is difficult to quantify accurately because it is difficult to completely separate signal from noise. It also depends on how noise is defined.
1047filter, inversion, noise, signal, stack, stacking velocity
1048None
1049None
1050--
1051spectrum
10521.n. [Geophysics]
1053Generally, a display of entities or properties according to magnitude. In geophysics, spectrum refers to a display of characteristics of a wavetrain or trace as a function of frequency, wavenumber, or arrival time. A common display of spectrum is amplitude as a function of frequency.
1054amplitude, arrival, frequency, phase, trace
1055None
1056None
1057--
1058spectrum
10592.n. [Formation Evaluation]
1060The distribution of gamma ray energies, or the number of gamma rays as a function of gamma ray energy.
1061activation log, geochemical log, induced gamma ray spectroscopy, neutron interactions, pulsed neutron spectroscopy measurement
1062None
1063None
1064--
1065stuck pipe
10661.n. [Drilling]
1067The portion of the drillstring that cannot be rotated or moved vertically.
1068differential sticking, pack off, stuck, topdrive
1069None
1070None
1071--
1072scallop gun
10731.n. [Perforating]
1074A perforating gun with a recess profile in the perforating gun body adjacent to the shaped charge. The scallop profile reduces the external burrs created as the perforating jet exits the gun body, thereby reducing the risk of hang-up or damage as the gun assembly is retrieved.
1075perforating gun
1076None
1077None
1078--
1079silica
10801.n. [Geology]
1081[SiO2]A chemically resistant dioxide of silicon that occurs in crystalline (quartz), amorphous (opal) and cryptocrystalline (chert) forms.
1082arenaceous, chert, diatom, diatomite, felsic, montmorillonite, quartz, sandstone, siliciclastic sediment
1083None
1084None
1085--
1086spherical focusing
10871.n. [Formation Evaluation]
1088A technique for focusing an electrode device based on maintaining a spherical equipotential surface centered at the main current electrode. Unlike the laterolog, which tries to maintain equipotential lines parallel to the sonde, spherical focusing tries to maintain the spherical equipotential lines that would exist in a homogeneous formation with no borehole. This is achieved with a particular arrangement of current-emitting electrode, current-return electrodes and monitor electrodes. This arrangement creates two spherical equipotential spheres with a constant voltage drop between them. The resistivity is determined from the current flowing between the spheres and the voltage drop. The depth of investigation is determined by the radii of the two spheres. Spherical focusing is used to produce shallow-reading resistivity logs and the pad-based microspherical log.
1089microresistivity
1090None
1091None
1092--
1093styrene
10941.n. [Drilling Fluids]
1095The compound C6H5-HC=CH2, also known as styrolene, cinnamene and phenethylene. The phenyl radical, C6H5-, replaces one of the hydrogen atoms on ethylene. Styrene polymers are analogous to vinyl polymers in structure except that phenyl radicals replace the corresponding H atom. (Due to larger size of the phenyl radical as compared to the H atom, not all corresponding polymers are possible.) A phenyl radical has the benzene ring structure-missing one H-with alternating double bonds between adjacent carbons. It is an aromatic group that is nonionic.
1096aromatic hydrocarbon, sulfonated polystyrene-maleic anhydride copolymer, vinyl polymer
1097None
1098None
1099--
1100scc
11011.n. [Drilling Fluids]
1102A form of corrosion in which susceptible types of metals will break by a combination of stress within the metal and the specific type of corrosion. Sulfide corrosion of ferrous alloys and chloride corrosion of stainless steels are two common type of SCC. When high-strength steel remains in contact with hydrogen sulfide (or sulfide ion) in a water-mud environment, sulfide SCC may occur. Tool joints, hardened parts of blowout preventers and valve trim are particularly susceptible to brittle failure caused by sulfide SCC. For this reason, along with toxicity risks of hydrogen sulfide gas, it is essential that water muds be kept entirely free of soluble sulfides and especially hydrogen sulfide at low pH.
1103None
1104None
1105stress-corrosion cracking
1106--
1107silica layer
11081.n. [Drilling Fluids]
1109One of the layers that constitute the atomic structure of the clay group of layeredsilicateminerals. The structure of these minerals can consist of two, three or four layers.The silica layer is a plane of silicon dioxide tetrahedra (silicon at the center and oxygen at all four corners of the tetrahedron). Another 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.
1110octahedral layer
1111None
1112None
1113--
1114spherical separator
11151.n. [Production Facilities]
1116A ball-shaped vessel used for fluid separation. A spherical separator can be used for two-phase or three-phase separation purposes.Spherical separators are less efficient than either horizontal or vertical cylindrical separators and are seldom used. Nevertheless, their compact size and ease of transportation have made them suitable for crowded processing areas.
1117horizontal separator, separator, three-phase separator, two-phase separator, vertical separator
1118None
1119None
1120--
1121sub
11221.n. [Drilling]
1123Any small component of the drillstring, such as a short drill collar or a thread crossover.
1124bit breaker, drill collar, junk basket
1125None
1126None
1127--
1128sub
11292.n. [Drilling]
1130Slang for substructure, which is the part of the rig that supports the derrick, rig floor and associated equipment.
1131derrick, rig floor
1132None
1133None
1134--
1135schedule
11361.n. [Production]
1137A system for indicating the wall thickness of pipe. The higher the schedule number, the thicker the wall for a certain pipe size.
1138None
1139None
1140None
1141--
1142similar fold
11431.n. [Geology]
1144A type of fold in which the thickness of the layers remains constant when measured parallel to the axial surface and the layers have the same wave shape, but the thickness along each layer varies. The folded layers tend to be thicker in the hinge of the fold and thinner along the limbs of the fold.
1145concentric fold, fold, harmonic, parallel fold
1146None
1147None
1148--
1149spill point
11501.n. [Geology]
1151The structurally lowest point in a hydrocarbon trap that can retain hydrocarbons. Once a trap has been filled to its spill point, further storage or retention of hydrocarbons will not occur for lack of reservoir space within that trap. The hydrocarbons spill or leak out, and they continue to migrate until they are trapped elsewhere.
1152contour map, migration, reservoir, structure, trap
1153None
1154None
1155--
1156subduction
11571.n. [Geology]
1158A plate tectonic process in which one lithospheric plate descends beneath another into the asthenosphere during a collision at a convergent plate margin. Because of the relatively higher density of oceanic lithosphere, it will typically descend beneath the lighter continental lithosphere during a collision. In a collision of plates of continental lithosphere, the density of the two plates is so similar that neither tends to be subducted and mountains form. As a subducted plate descends into the asthenosphere, Earthquakes can occur, especially in the Wadati-Benioff zone, but, if the plate descends deeply into the mantle, it will eventually be heated to the point of melting. Volcanoes can form above a descending plate.
1159active margin, asthenosphere, collision, convergence, density, lithosphere, mantle, midoceanic ridge, plate tectonics, volcano, Wadati-Benioff zone
1160None
1161None
1162--
1163scintillation detector
11641.n. [Formation Evaluation]
1165A device for measuring the number and energy of gamma rays. The device consists of a crystal and a photomultiplier. In the crystal, an incident gamma ray imparts energy to electrons through Compton scattering, photoelectric absorption and pair production. The electrons excite the detector crystal lattice. Crystal de-excitation emits visible or near-visible light, the scintillation, which is detected by the photomultiplier and transformed into an electrical pulse. The frequency and amplitude of the electric pulse are related to the number of gamma rays and their respective energy levels, and are recorded in a log. Scintillation detectors are used in all natural gamma ray, induced gamma ray and density logging devices.
1166activation log, density measurement, gamma ray log, natural gamma ray spectroscopy, photoelectric effect
1167None
1168None
1169--
1170simple multiple
11711.n. [Geophysics]
1172An event in which one deeper and one near-surface reflector, such as the base of weathering or the ocean floor, are involved. The seismic energy bounces twice from the deep reflector and only once from the shallow reflector, causing the multiple to appear at roughly twice the traveltime of the primary reflection.
1173long-path multiple
1174None
1175None
1176--
1177spin flowmeter
11781.n. [Production Testing]
1179A production logging method that uses a small propeller turned by fluid movement. The number of turns of the propeller can be related to the amount of fluid passing through the instrument.These devices are used to determine which of several zones contributes the most to the total production or, in the case of an injection well, which zone is receiving the most injected fluids.
1180None
1181None
1182None
1183--
1184submersible drilling rig
11851.n. [Drilling]
1186A particular type of floating vessel, usually used as a mobile offshore drilling unit (MODU), that is supported primarily on large pontoon-like structures submerged below the seasurface. The operating decks are elevated 100 or more feet [30 m] above the pontoons on large steel columns. Once on the desired location, this type of structure is slowly flooded until it rests on the seafloor. After the well is completed, the water is pumped out of the buoyancy tanks, the vessel refloated and towed to the next location. Submersibles, as they are known informally, operate in relatively shallow water, since they must actually rest on the seafloor.
1187mobile offshore drilling unit
1188None
1189None
1190--
1191scotch yoke
11921.n. [Production]
1193A slotted link mechanism that works as the quarter-turn operator for use on quarter-turn valves in place of gears. The Scotch yoke has a torque output at the beginning and end of its stroke that is generally twice the magnitude of the torque output in the center of its stroke.
1194None
1195None
1196None
1197--
1198simulated annealing
11991.n. [Reservoir Characterization]
1200A method for constructing a gridded reservoir model by iterative trial and error. The grid is initially populated randomly with a characteristic (such as facies) so that some property (such as a net/gross ratio) is correct. Then the grids are randomly swapped so that the property is preserved but another property (such as total length) is improved.
1201None
1202None
1203None
1204--
1205spine and ribs plot
12061.n. [Formation Evaluation]
1207For a two-detector density tool, the plot of long-spacing versus short-spacing count rates for different formation densities, mudcake densities and mudcake thicknesses. The plot takes its name from the spine, which is the locus of points with no mudcake, and the ribs, which show the effect of mudcake at certain fixed formation densities. The plot illustrates graphically that for a given formation density there is only one rib for all normal mudcake densities and thicknesses. Thus, although there are three unknowns, it is possible to make a correction using two measurements.
1208azimuthal density, compensated-density log, delta rho, density measurement
1209None
1210None
1211--
1212subsalt
12131.n. [Geology]
1214An exploration and production play type in which prospects exist below salt layers. Until relatively recently, many explorationists did not seek prospects below salt because seismic data had been of poor quality below salt (i.e., it was not possible to map traps accurately) or because they believed that reservoir-quality rock or hydrocarbons did not exist below salt layers. Advances in seismic processing and compelling drilling results from exploration wells encouraged companies to generate and drill prospects below salt layers, salt sheets and other previously disregarded potential traps. The offshore Gulf of Mexico contains numerous subsalt-producing fields, and similar areas are being explored internationally.
1215exploration, halite, play, play, production, prospect, salt dome, stratigraphic trap, structural trap, trap
1216None
1217subsalt
1218--
1219scout ticket
12201.n. [Geology]
1221A brief report about a well from the time it is permitted through drilling and completion. A scout ticket typically includes the location, total depth, logs run, production status and formation tops.
1222exploration, production
1223None
1224None
1225--
1226simultaneous operation simop
12271.n. [Well Completions]
1228A term used mainly on offshore platforms, or installations with multiple wellheads, where more than one wellbore is being accessed, such as where a drilling rig, slickline unit or coiled tubing unit may be operating at the same time. Simultaneous operations generally have an impact on the installation safety procedures and contingency planning processes.
1229None
1230None
1231None
1232--
1233spinner flowmeter
12341.n. [Production Logging]
1235A device for measuring in situ the velocity of fluid flow in a production or injection well based on the speed of rotation of an impeller, or spinner. The spinner can be helical, that is, longer than it is wide, or like a vane, which is similar to a fan blade. In both cases, the speed of rotation is measured and related to the effective velocity of the fluid. Friction and fluid viscosity cause the relationship to be slightly nonlinear at low effective velocities and introduce a threshold velocity below which the spinner does not turn. Results are interpreted using the multipass, two-pass or single-pass methods.There are several types of spinner flowmeter. The most common device uses a small vane-like spinner, about 1.5 in. [3.8 cm] in diameter, allowing the logging tool to pass through the tubing and other restrictions before reaching the reservoir interval. The small spinner captures only part of the fluid flow in the casing, too little to make it turn in some low flow-rate wells and possibly unrepresentative in multiphase flow settings. Other devices have been designed to capture more of the flow, for example the fullbore spinner and various types of flow-concentrating or diverter spinners, such as the packer flowmeter and the basket flowmeter.
1236basket flowmeter, flow profile, packer flowmeter, production log
1237None
1238None
1239--
1240subsea isolation valve
12411.n. [Production]
1242A valve used underwater, generally in a manifold that will close and isolate a particular pipeline or process in an emergency.
1243None
1244None
1245None
1246--
1247scraper
12481.n. [Well Workover and Intervention]
1249Also called a pig, a device with blades or brushes inserted in apipelinefor cleaning purposes. Thepressureof the oil stream behind pushes the pig along the pipeline to clean out rust, wax,scaleand debris. To clean downhole tubulars a similar device, called a casing scraper or paraffin scraper, may be used.
1250scraper trap
1251pig
1252None
1253--
1254single pass method
12551.n. [Production Logging]
1256A technique for interpreting the results from a spinner flowmeter using only one logging run over the zone of interest. Spinner speed is related to fluid velocity using laboratory-determined values for threshold velocity and spinner response. The single-pass method is generally considered inferior to the in-situ multipass or two-pass method. However, in highly deviated and horizontal wells, where the logging tools must be deployed using coiled tubing or a tractor, the cost of an additional pass is high. Single-pass interpretation, with improved spinner characterization, has therefore become more common in recent years.
1257effective velocity, flow profile, multipass method, spinner flowmeter, spinner reversal, threshold velocity, two-pass method, velocity-correction factor
1258None
1259None
1260--
1261spinning drop tensiometer
12621.n. [Enhanced Oil Recovery]
1263A standard laboratory instrument to measure interfacial tension. The method is particularly applicable to values of interfacial tension below 1 mN/m and especially below 10-2 mN/m, as may occur when employing surfactants for enhanced oil recovery. The method utilizes a tube containing a drop of the less-dense phase within the more-dense phase. When the tube is spun along its long axis at high speed, the resulting forces center the drop on the tube axis and deform it. The interfacial tension is a function of the shape of the deformed drop, the liquid densities and the rotation speed. Advanced versions of the instrument can periodically vary the rotation rate. The phase lag between the change of rotation rate and the drop deformation can be used to determine both interfacial elasticity and interfacial viscosity.
1264interfacial tension, pendant-drop tensiometer
1265None
1266None
1267--
1268subsurface safety valve sssv
12691.n. [Well Completions]
1270A safety device installed in the upper wellbore to provide emergency closure of the producing conduits in the event of an emergency. Two types of subsurface safety valve are available: surface-controlled and subsurface controlled. In each case, the safety-valve system is designed to be fail-safe, so that the wellbore is isolated in the event of any system failure or damage to the surface production-control facilities.
1271surface-controlled subsurface safety valve (SCSSV)
1272None
1273None
1274--
1275scratcher
12761.n. [Drilling]
1277A device for cleaning mud and mud filter cake off of the wellbore wall when cementing casing in the hole to ensure good contact and bonding between the cement and the wellbore wall. The scratcher is a simple device, consisting of a band of steel that fits around a joint of casing, and stiff wire fingers or cable loops sticking out in all directions around the band (360-degree coverage). A scratcher resembles a bottlebrush, but its diameter is greater than its height. Importantly, for scratchers to be effective, the casing must be moved. This movement may be reciprocal motion in and out of the wellbore, rotary motion, or both. In general, the more motion, the better the cement job will be.
1278casing, cementing
1279None
1280None
1281--
1282single phase
12831.n. [Production Logging]
1284The only component of a flow or other phenomenon, normally oil, water or gas.
1285biphasic, multiphase, phase
1286None
1287None
1288--
1289spline
12901.n. [Reservoir Characterization]
1291A mathematical procedure for connecting data points with a smooth line. The line does not necessarily go through the data points, but its direction and curvature are affected by all the data points. The "stiffness" of the line is controlled by a variable (lambda) in the algorithm.
1292None
1293None
1294None
1295--
1296subsurface surface controlled safety valve sscsv
12971.n. [Well Completions]
1298A downhole safety valve designed to close automatically in an emergency situation. There are two basic operating mechanisms: valves operated by an increase influid flowand valves operated by a decrease in ambientpressure.
1299None
1300None
1301None
1302--
1303screen
13041.n. [Well Completions]
1305A device used insand controlapplications to support thegravel pack. To form a screen, a profiled wire is wrapped and welded in place on aperforated liner. Screens are available in a range of sizes and specifications, includingoutside diameter, material type and the geometry and dimension of the screen slots. The space between each wire wrap must be small enough to retain the gravel placed behind the screen, yet minimize any restriction toproduction.
1306None
1307wire-wrapped screen
1308None
1309--
1310single shot survey
13111.n. [Reservoir Characterization]
1312A technique for acquiring deviation information from a borehole on a slickline. In high-angle wells, a multishot technique is usually used instead.
1313multishot survey
1314None
1315None
1316--
1317spontaneous potential
13181.n. [Geophysics]
1319Naturally occurring (static) electrical potential in the Earth. Spontaneous potentials are usually caused by charge separation in clay or other minerals, by the presence of a semipermeable interface impeding the diffusion of ions through the pore space of rocks, or by natural flow of a conducting fluid (salty water) through the rocks. Variations in SP can be measured in the field and in wellbores to determine variations of ionic concentration in pore fluids of rocks.
1320diffusion
1321None
1322SP
1323--
1324spontaneous potential
13252.n. [Formation Evaluation]
1326A log of the natural difference in electrical potential, in millivolts, between an electrode in the borehole and a fixed reference electrode on the surface. The most useful component of this difference is the electrochemical potential since it can cause a significant deflection opposite permeable beds. The magnitude of the deflection depends mainly on the salinity contrast between drilling mud and formation water, and the clay content of the permeable bed. The spontaneous potential (SP) log is therefore used to detect permeable beds and to estimate formation water salinity and formation clay content. The SP log cannot be recorded in nonconductive mud.The SP can be affected by several factors that make interpretation difficult. First, there are other possible sources of electrical potential not related to the electrochemical effect, for example, the electrokinetic potential and bimetallism. Many of these are small and constant throughout the log, and can be lumped together in the shale baseline. Second, the SP can measure only the potential drop in the borehole, and not the full electrochemical potential. The ideal SP opposite a clean bed is known as the static spontaneous potential (SSP), and opposite a shaly bed as the pseudostatic spontaneous potential (PSP). The SP is always less than the SSP or the PSP and more rounded at the boundaries between shales and permeable beds.The SP was first recognized by C. Schlumberger, M. Schlumberger and E.G. Leonardon in 1931, and the first published examples were from Russian oil fields.
1327differential SP, fish, liquid-junction potential, membrane potential
1328None
1329None
1330--
1331subsurface surface controlled safety valve sscsv
13321.n. [Well Completions]
1333A downhole safety valve designed to close automatically in an emergency situation. There are two basic operating mechanisms: valves operated by an increase in fluid flow and valves operated by a decrease in ambient pressure.
1334None
1335None
1336None
1337--
1338seal assembly
13391.n. [Well Completions]
1340A system of seals arranged on the component that engages in a sealbore to isolate the production-tubing conduit from the annulus. The seal assembly is typically longer than the sealbore to enable some movement of the components while maintaining an efficient seal.
1341production tubing
1342None
1343None
1344--
1345single tank composite sample
13461.n. [Production Testing]
1347The mixture of liquid samples taken from the upper, middle and lower sections of a storage tank. Normally the storage tanks (upright cylindrical or horizontal cylindrical tanks) in the oil field contain crude oil, water and emulsions.
1348None
1349None
1350None
1351--
1352spooler
13531.n. [Well Workover and Intervention]
1354A device used to handle and temporarily store a coiled tubing string. Spoolers generally are configured with a removable drum that allows transport spools to be inserted, allowing a new string to be spooled onto a reel. The term is also occasionally used to describe the levelwind assembly on a tubing reel.
1355coiled tubing string, levelwind
1356None
1357None
1358--
1359suction pit
13601.n. [Drilling]
1361A mud tank, usually made of steel, connected to the intake of the main rig pumping system. The connection is commonly formed with a centrifugal pump charging the main rig pumps to increase efficiency. Since it is the last tank in the surface mud system, the suction pit should contain the cleanest and best-conditioned mud on location. It is also the most representative of mud characteristics in the hole, except for temperature.
1362None
1363None
1364None
1365--
1366seals
13671.n. [Reservoir Characterization]
1368The geological barriers that isolate fluid compartments within reservoirs or that hydraulically isolate reservoirs from each other. The seals may contain fluids (for example shales) but have very low permeability. The properties of seals can determine the height of hydrocarbon column trapped below them.
1369None
1370None
1371None
1372--
1373single pass method
13741.n. [Production Logging]
1375A technique for interpreting the results from a spinner flowmeter using only one logging run over the zone of interest. Spinner speed is related to fluid velocity using laboratory-determined values for threshold velocity and spinner response. The single-pass method is generally considered inferior to the in-situ multipass or two-pass method. However, in highly deviated and horizontal wells, where the logging tools must be deployed using coiled tubing or a tractor, the cost of an additional pass is high. Single-pass interpretation, with improved spinner characterization, has therefore become more common in recent years.
1376effective velocity, flow profile, multipass method, spinner flowmeter, spinner reversal, threshold velocity, two-pass method, velocity-correction factor
1377None
1378None
1379--
1380spot
13811.vb. [Drilling Fluids]
1382To place a small volume or pill of fluid in a wellboreannulusto free differentiallystuckpipe. Oil-base mud is the traditional stuck-pipe spotting fluid. Speed in mixing and placing the spot is of primary importance to successfully freeing pipe. Because of concern about mud disposal, spots used offshore are either synthetic-based emulsions or benign water-base formulations. Each type is supplied as prepackaged concentrate designed for rapid access and mixing at the rig. A spot frees pipe by covering the stuck region. It presumably breaks up the filter cake, allowing the spot to migrate into cracks in the cake and between the pipe and the cake, reducing the stuck area and allowing pipe to be pulled free.
1383differential sticking, dynamic filtration, hydrostatic pressure, pill, spotting, static filtration, surfactant, synthetic-base mud, water-base drilling fluid
1384None
1385None
1386--
1387spot
13882.vb. [Well Workover and Intervention]
1389To accurately place a fluid, or fluid interface, at a given position within the wellbore. Treatment fluids such as cement slurries and stimulation fluids for localized treatment often require accurate placement. Correctly calculating and pumping the appropriate volume of displacement fluid while taking account of well production, wellbore returns and fluid-density variations are key factors in achieving accurate placement of fluids.
1390spotting
1391None
1392None
1393--
1394sulfate reducing bacteria
13951.n. [Drilling Fluids]
1396A common anaerobic bacterium, commonly abbreviated SRB, that can convert sulfate ions, SO4-2, into S-2 and HS-, with the concomitant oxidation of a carbon source. The lignite, lignin, tannins, cellulose, starches and fatty acids found in many mud systems are carbon food sources for SRB. Where mud is stored, precautions should always be taken when handling or reconditioning water muds containing lignosulfonates, gypsum (sulfate sources) and starches, cellulose, xanthan gum and lignite (food sources). These muds can harbor SRB and can have high sulfide accumulations. Mud filtrate should be tested with the Garrett Gas Train to determine sulfide concentration in a stored mud, followed by treatments with caustic soda to raise pH and zinc-based scavengers to remove sulfides as ZnS. Before storage of mud, treatment with a bactericide can inhibit SRB growth. Also, circulating mud from time to time, with air entrainment, can retard development of anaerobic conditions.Anaerobic bacteria can convert the sulfate or sulfite present in water handling facilities to hydrogen sulfide [H2S]. This by-product, combined with iron, can form iron sulfide, a scale that is very difficult to remove. SRB occur naturally in surface waters, including seawater. Bacteria accumulation can lead to pitting of steel, and the buildup of H2S increases the corrosiveness of the water, thus increasing the possibility of hydrogen blistering or sulfide stress cracking.
1397None
1398None
1399sulfate-reducing bacteria
1400--
1401seat
14021.n. [Production]
1403That part of a valve against which the closure element (gate, ball) affects a tight shutoff. In many ball valves and gate valves, it is a floating member usually containing a soft seating element.
1404None
1405None
1406None
1407--
1408single phase
14091.adj. [Production Logging]
1410Referring to a flow or other phenomenon with only one component, normally oil, water or gas.
1411biphasic, multiphase, phase
1412None
1413None
1414--
1415spotting
14161.n. [Drilling Fluids]
1417Placing a small volume or pill of fluid in a wellboreannulusto free differentiallystuckpipe. Oil-base mud is the traditional stuck-pipe spotting fluid. Speed in mixing and placing the spot is of primary importance to successfully freeing pipe. Because of concern about mud disposal, spots used offshore are either synthetic-based emulsions or benign water-base formulations. Each type is supplied as prepackaged concentrate designed for rapid access and mixing at the rig. A spot frees pipe by covering the stuck region. It presumably breaks up the filter cake, allowing the spot to migrate into cracks in the cake and between the pipe and the cake, reducing the stuck area and allowing pipe to be pulled free.
1418differential sticking, dynamic filtration, hydrostatic pressure, pill, spot, static filtration, surfactant, synthetic-base mud, water-base drilling fluid
1419None
1420None
1421--
1422spotting
14232.n. [Well Workover and Intervention]
1424Accurately placing a fluid, or fluid interface, at a given position within the wellbore. Treatment fluids such as cement slurries and stimulation fluids for localized treatment often require accurate placement. Correctly calculating and pumping the appropriate volume of displacement fluid while taking account of well production, wellbore returns and fluid-density variations are key factors in achieving accurate placement of fluids.
1425None
1426None
1427None
1428--
1429sulfate reducing bacteria
14301.n. [Drilling Fluids]
1431A common anaerobic bacterium, commonly abbreviated SRB, that can convert sulfate ions, SO4-2, into S-2 and HS-, with the concomitant oxidation of a carbon source. The lignite, lignin, tannins, cellulose, starches and fatty acids found in many mud systems are carbon food sources for SRB. Where mud is stored, precautions should always be taken when handling or reconditioning water muds containing lignosulfonates, gypsum (sulfate sources) and starches, cellulose, xanthan gum and lignite (food sources). These muds can harbor SRB and can have high sulfide accumulations. Mud filtrate should be tested with the Garrett Gas Train to determine sulfide concentration in a stored mud, followed by treatments with caustic soda to raise pH and zinc-based scavengers to remove sulfides as ZnS. Before storage of mud, treatment with a bactericide can inhibit SRB growth. Also, circulating mud from time to time, with air entrainment, can retard development of anaerobic conditions.Anaerobic bacteria can convert the sulfate or sulfite present in water handling facilities to hydrogen sulfide [H2S]. This by-product, combined with iron, can form iron sulfide, a scale that is very difficult to remove. SRB occur naturally in surface waters, including seawater. Bacteria accumulation can lead to pitting of steel, and the buildup of H2S increases the corrosiveness of the water, thus increasing the possibility of hydrogen blistering or sulfide stress cracking.
1432fatty acid, hydrogen sulfide, iron-oxidizing bacteria, paraformaldehyde, redox, slime-forming bacteria, sour gas, stress-corrosion cracking, sulfide scavenger, XC polymer
1433None
1434SRB
1435--
1436seating nipple
14371.n. [Well Completions]
1438A completion component fabricated as a short section of heavy wall tubular with a machined internal surface that provides a seal area and a locking profile. Landing nipples are included in most completions at predetermined intervals to enable the installation of flow-control devices, such as plugs and chokes. Three basic types of landing nipple are commonly used: no-go nipples, selective-landing nipples and ported or safety-valve nipples.
1439no-go landing nipple, selective nipple
1440None
1441None
1442--
1443single shot survey
14441.n. [Reservoir Characterization]
1445A technique for acquiring deviation information from a borehole on a slickline. In high-angle wells, a multishot technique is usually used instead.
1446multishot survey
1447None
1448None
1449--
1450spotting fluid
14511.n. [Drilling Fluids]
1452A small volume or pill of fluid placed in a wellbore annulus to free differentially stuck pipe. Oil-base mud is the traditional stuck-pipe spotting fluid. Speed in mixing and placing the spot is of primary importance to successfully freeing pipe. Because of concern about mud disposal, spots used offshore are either synthetic-based emulsions or benign water-base formulations. Each type is supplied as prepackaged concentrate designed for rapid access and mixing at the rig. A spot frees pipe by covering the stuck region. It presumably breaks up the filter cake, allowing the spot to migrate into cracks in the cake and between the pipe and the cake, reducing the stuck area and allowing pipe to be pulled free.
1453differential sticking, dynamic filtration, hydrostatic pressure, pill, spot, spotting, static filtration, surfactant, synthetic-base mud, water-base drilling fluid
1454None
1455None
1456--
1457sulfide scavenger
14581.n. [Drilling Fluids]
1459A chemical that removes all three soluble sulfide species, H2S, S-2 and HS-, and forms a product that is nonhazardous and noncorrosive. Zinc compounds are commonly used to precipitate ZnS and decrease the concentration of all three sulfides that are in equilibrium in a solution to a very low concentration. For water mud, zinc basic carbonate, and, for oil mud, zinc oxide, are recognized to be effective sulfide scavengers. Oxidation of sulfides to form other types of sulfur compounds will remove sulfides from a mud, but slowly and with less certainty.
1460copper carbonate, corrosion coupon, Garrett Gas Train, hydrogen sulfide, iron sulfide, oxygen scavenger, precipitation, pyrrhotite, redox, scavenger, sequestering agent, stress-corrosion cracking, sulfate-reducing bacteria, sulfide, zinc basic carbonate
1461None
1462None
1463--
1464secondary porosity index
14651.n. [Formation Evaluation]
1466An indicator of the porosity that does not contribute to a sonic measurement of interval transit time. The transit time is little affected by vugs, fractures and other irregular events because the sonic wave finds a faster path around them. Spherical pores such as oomolds also have less effect on traveltime than oblate pores. Thus, when the sonic porosity is less than some measurement of the total porosity, the difference can be attributed to the presence of post-depositional, or secondary, porosity. The sonic porosity is usually derived from the Wyllie time-average equation, or some other suitable transform, and the total porosity taken as the density-neutron crossplot porosity.
1467sonic log
1468None
1469None
1470--
1471single tank composite sample
14721.n. [Production Testing]
1473The mixture of liquid samples taken from the upper, middle and lower sections of a storage tank. Normally the storage tanks (upright cylindrical or horizontal cylindrical tanks) in the oil field contain crude oil, water and emulsions.
1474None
1475None
1476None
1477--
1478spreading loss
14791.n. [Formation Evaluation]
1480The additional loss in amplitude of an electromagnetic wave emitted by an electromagnetic propagation or dielectric propagation measurement compared to that of a plane wave. The spreading loss depends on the geometry of the transmitter-receiver array and also on the dielectric properties of the formation. The same effect also causes a small correction to the propagation time.
1481attenuation, broadside array, dielectric propagation log, electromagnetic propagation, electromagnetic propagation measurement, endfire array, plane wave
1482None
1483None
1484--
1485sulfide stress cracking
14861.n. [Drilling Fluids, Well Workover and Intervention, Well Completions]
1487A type of spontaneous brittle failure in steels and other high-strength alloys when they are in contact with moisthydrogen sulfide and other sulfidic environments.Tool joints, hardened parts of blowout preventers and valve trim are particularly susceptible. For this reason, along with toxicity risks of hydrogen sulfide gas, it is essential that water muds be kept entirely free of soluble sulfides and especially hydrogen sulfide at low pH. Sulfide stress cracking is also called hydrogen sulfide cracking, sulfide cracking, sulfide corrosion cracking and sulfide stress-corrosion cracking. The variation of the name is due to the lack of agreement in the mechanism of failure. Some researchers consider sulfide-stress cracking a type of stress-corrosion cracking, while others consider it a type of hydrogen embrittlement.
1488corrosion control, hydrogen embrittlement, hydrogen induced failures, stress-corrosion cracking
1489None
1490None
1491--
1492secondary production
14931.n. [Well Completions]
1494The method used to sustain production levels at viable rates following a fall in flow rate as the efficiency of the primary production methods declines. Secondary production methods frequently involve an artificial-lift system or reservoir injection for pressure maintenance.
1495None
1496None
1497None
1498--
1499sinistral
15001.adj. [Geology]
1501Pertaining to a strike-slip or left-lateral fault in which the block across the fault moves to the left; also called a sinistral strike-slip fault. If it moves to the right, the relative motion is described as dextral. Counterclockwise rotation or spiraling is also described as sinistral.
1502fault, strike-slip fault
1503None
1504Antonyms:dextral
1505--
1506spud
15071.vb. [Drilling]
1508To start the well drilling process by removing rock, dirt and other sedimentary material with the drill bit.
1509bit
1510None
1511None
1512--
1513spud
15142.vb. [Drilling]
1515To apply weight to a troublesome drilling section, usually by moving the drilling string up and down, in hopes that the section will drill faster.
1516drillstring
1517None
1518None
1519--
1520sulfide test
15211.n. [Drilling Fluids]
1522A quantitative analysis of sulfides in the drilling fluid. Specific test methods have been published byAPI. The oil-mudprocedure analyzes active sulfides and uses whole mud samples, whereas thewater-base drilling fluidprocedure testsfiltrate. Theinstrument used is called a Garrett gas train (GGT), a clear,plasticblock (2.5 in. x 4 in. x 6 in.) that contains three interconnected chambers. A carrier gas is used to flow an inert gas through the chambers. The sample is placed in chamber #1 and is acidified to release sulfides as H2S (and carbonates as CO2). The appropriateDrdger tubeis used to measure the effluent gas that is evolved from the sample. The device is named after Bob Garrett, who invented it while at Exxon Production Research.References: Garrett RL: "A New Field Method for the Quantitative Determination of Sulfides in Water-Based Drilling Fluids,"Journal of Petroleum Technology29, no. 9 (September 1977): 1195-1201.Garrett RL, Carlton LA and Denekas MO: "Methods for Field Monitoring of Oil-Based Drilling Fluids for Hydrogen Sulfide and Water Intrusions,"SPE Drilling Engineering3, no.3 (September 1988): 296-302.
1523Garrett Gas Train, hydrogen sulfide, iron sulfide, OSHA, pyrrhotite, stress-corrosion cracking, sulfate-reducing bacteria, zinc basic carbonate
1524None
1525None
1526--
1527secondary recovery
15281.n. [Enhanced Oil Recovery, Enhanced Oil Recovery]
1529The second stage of hydrocarbon production during which an external fluid such as water or gas is injected into the reservoir through injection wells located in rock that has fluid communication with production wells. The purpose of secondary recovery is to maintain reservoir pressure and to displace hydrocarbons toward the wellbore.The most common secondary recovery techniques are gas injection and waterflooding. Normally, gas is injected into the gas cap and water is injected into the production zone to sweep oil from the reservoir. A pressure-maintenance program can begin during the primary recovery stage, but it is a form or enhanced recovery.The secondary recovery stage reaches its limit when the injected fluid (water or gas) is produced in considerable amounts from the production wells and the production is no longer economical. The successive use of primary recovery and secondary recovery in an oil reservoir produces about 15% to 40% of the original oil in place.
1530enhanced oil recovery, gas cap, improved oil recovery, primary recovery, reservoir pressure, tertiary recovery, waterdrive, waterflooding
1531None
1532None
1533--
1534sinker bar
15351.n. [Well Workover and Intervention]
1536Also known as stem, the weight bar used in slickline operations to overcome the effects of wellhead pressure and friction at the surface seal where the wire enters the wellbore. In addition to a solid steel stem, a special high-density stem is available with internal cavities filled with lead, tungsten or mercury alloys.
1537None
1538None
1539None
1540--
1541spud mud
15421.n. [Drilling Fluids]
1543Mud used to drill a well from surface to a shallow depth. Guar gum or salt gel are commonly used offshore as spud mud. Onshore spud mud is usually a water-base mud containing bentonite clay that is flocculated with lime. In a large-diameter surface hole, a flocculated clay-based mud can remove large gravel cuttings encountered at shallow depths and is simple and inexpensive.
1544carrying capacity, flocculation, guar gum, lime mud, mudding up, native clay, native-solids mud
1545None
1546None
1547--
1548sulfonated polystyrene maleic anhydride copolymer
15491.n. [Drilling Fluids]
1550A copolymer of polystyrene (containing sulfonate groups on the ring) and anhydrous maleic acid (a di-hydroxy acid). The sulfonated ring-structure polymer component is anionic and usually low to moderate in chain length and molecular weight. As such, with negative groups on the structure (amount of negativity depending on degree of sulfonation), it is used as a clay deflocculant for bentonite-based water mud. It is especially stable to temperature up to around 400°F [204°C], and often used in high-density muds to stabilize rheology. Lignosulfonate is used for this purpose up to about 300°F [149°C] and then SSMA polymeric deflocculant is often phased into the mud system for drilling deeper and hotter zones.
1551bentonite, clay-water interaction, polar compound, styrene
1552None
1553SSMA, SSMA copolymer
1554--
1555secondary porosity index
15561.n. [Formation Evaluation]
1557An indicator of the porosity that does not contribute to a sonic measurement of interval transit time. The transit time is little affected by vugs, fractures and other irregular events because the sonic wave finds a faster path around them. Spherical pores such as oomolds also have less effect on traveltime than oblate pores. Thus, when the sonic porosity is less than some measurement of the total porosity, the difference can be attributed to the presence of post-depositional, or secondary, porosity. The sonic porosity is usually derived from the Wyllie time-average equation, or some other suitable transform, and the total porosity taken as the density-neutron crossplot porosity.
1558sonic log
1559None
1560None
1561--
1562sip
15631.n. [Drilling]
1564The surface force per unit area exerted at the top of a wellbore when it is closed at either the Christmas tree or the BOP stack. The pressure may be from the formation or an external and intentional source. The SIP may be zero, indicating that any open formations are effectively balanced by the hydrostatic column of fluid in the well. If the pressure is zero, the well is considered to be dead, and can normally be opened safely to the atmosphere.
1565None
1566None
1567shut-in pressure
1568--
1569squeeze pressure
15701.n. [Well Workover and Intervention]
1571The final or maximum pressure that can be applied during a squeeze operation. When conducting a squeeze-cement job, it is generally desirable to achieve a high final squeeze pressure that indicates the target holes and voids are filled with cement filter cake.
1572squeeze job
1573None
1574None
1575--
1576summation of fluids method
15771.n. [Formation Evaluation]
1578A technique for measuring the effective porosity of a core sample by summing the volumes of the fluids recovered from it. The volumes of the gas, oil and water in the sample usually are determined by the retort method, which also determines the bulk volume. The porosity is then the ratio of the total fluid volume to the bulk volume.
1579Boyle's Law Double Cell, Boyle's Law Single Cell, buoyancy, core plug, liquid saturation method, mercury displacement method, porosimeter, retort method, routine core analysis
1580None
1581None
1582--
1583seep
15841.n. [Geology]
1585A naturally occurring, typically slow leakage of fluid—water, oil or gas—at the Earth’s surface. A seep results frommigration of the fluid from its source orreservoir formation because theformation pressure exceeds the formation’sseal capacity such as during rapid loading of theoverburden bysedimentation or during fluid expansion or from damage to the seal such as byfaulting or tectonism.
1586exploration
1587None
1588None
1589--
1590skewness
15911.n. [Reservoir Characterization]
1592The degree to which a distribution has lost the bilateral symmetry of a normal distribution. Skewness is usually expressed qualitatively rather than quantitatively.
1593None
1594None
1595None
1596--
1597srb
15981.n. [Drilling Fluids]
1599A common anaerobic bacterium, commonly abbreviated SRB, that can convert sulfate ions, SO4-2, into S-2 and HS-, with the concomitant oxidation of a carbon source. The lignite, lignin, tannins, cellulose, starches and fatty acids found in many mud systems are carbon food sources for SRB. Where mud is stored, precautions should always be taken when handling or reconditioning water muds containing lignosulfonates, gypsum (sulfate sources) and starches, cellulose, xanthan gum and lignite (food sources). These muds can harbor SRB and can have high sulfide accumulations. Mud filtrate should be tested with the Garrett Gas Train to determine sulfide concentration in a stored mud, followed by treatments with caustic soda to raise pH and zinc-based scavengers to remove sulfides as ZnS. Before storage of mud, treatment with a bactericide can inhibit SRB growth. Also, circulating mud from time to time, with air entrainment, can retard development of anaerobic conditions.Anaerobic bacteria can convert the sulfate or sulfite present in water handling facilities to hydrogen sulfide [H2S]. This by-product, combined with iron, can form iron sulfide, a scale that is very difficult to remove. SRB occur naturally in surface waters, including seawater. Bacteria accumulation can lead to pitting of steel, and the buildup of H2S increases the corrosiveness of the water, thus increasing the possibility of hydrogen blistering or sulfide stress cracking.
1600None
1601None
1602sulfate-reducing bacteria
1603--
1604superficial velocity
16051.n. [Production Logging]
1606The velocity of fluid moving through a pipe, defined as the volumetric flow rate of that fluid divided by the cross-sectional area. In monophasic flow, it is equal to the mean velocity of the fluid. In multiphase flow, it is not a physically real velocity but is a convenient parameter for analysis.
1607flow regime, flow structure, laminar flow, multiphase flow, turbulent flow
1608None
1609None
1610--
1611seismic acquisition
16121.n. [Geophysics]
1613The 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.
1614common midpoint method, explosive seismic data, gather, geophone, hydrophone, shotpoint
1615acquisition
1616None
1617--
1618skid
16191.n. [Geophysics]
1620A conveyance, such as a sled with runners or pontoons, used to transport geophysical gear to a location. Skids are commonly deployed in acquisition of seismic data in marshes or other areas of soft, soggy terrain.
1621acquisition, marsh
1622None
1623None
1624--
1625skid
16262.n. [Drilling]
1627A steel frame on which portable equipment is mounted to facilitate handling with cranes or flatbed trucks. The skid is robust, is usually designed with attachment points for hooks, chains, or cables, and has at least two lengthwise beams to facilitate sliding the equipment into place on the rigsite.
1628None
1629None
1630None
1631--
1632skid
16333.vb. [Drilling]
1634To slide the rig over, such as to move it from one well slot to another on a fixed offshore platform. This operation is accomplished by disconnecting the rigid attachments from the platform to the rig, and energizing large-capacity hydraulic cylinders that push the rig over greased steel skid beams.
1635None
1636None
1637None
1638--
1639ssma
16401.n. [Drilling Fluids]
1641A copolymer of polystyrene (containing sulfonate groups on the ring) and anhydrous maleic acid (a di-hydroxy acid). The sulfonated ring-structure polymer component is anionic and usually low to moderate in chain length and molecular weight. As such, with negative groups on the structure (amount of negativity depending on degree of sulfonation), it is used as a clay deflocculant for bentonite-based water mud. It is especially stable to temperature up to around 400°F [204°C], and often used in high-density muds to stabilize rheology. Lignosulfonate is used for this purpose up to about 300°F [149°C] and then SSMA polymeric deflocculant is often phased into the mud system for drilling deeper and hotter zones.
1642None
1643None
1644sulfonated polystyrene-maleic anhydride copolymer
1645--
1646superposition
16471.n. [Geology]
1648The stratigraphic principle that, in the case of undeformed, flat-lying strata, younger layers are deposited atop older ones, such that the top layer is youngest and underlying layers increase in age with depth. Nicolaus Steno articulated the law of superposition of strata in the 17th century.
1649absolute age, bed, geochronology, relative age, stratigraphy, stratum
1650None
1651None
1652--
1653superposition
16542.n. [Well Testing]
1655A mathematical technique based on the property that solutions to linear partial equations can be added to provide yet another solution. This permits constructions of mathematical solutions to situations with complex boundary conditions, especially drawdown and buildup tests, and in settings where flow rates change with time.
1656buildup test, drawdown test
1657None
1658None
1659--
1660seismic line
16611.n. [Geophysics]
1662A display ofseismicdata along a line, such as a 2D seismicprofileor a profile extracted from a volume of3D seismic data. A seismic section consists of numerous traces with location given along the x-axis and two-way traveltimeor depth along the y-axis. The section is called adepth sectionif the section has been converted from time to depth and a time section if this has not been done.
1663trace, two-dimensional survey
1664seismic section
1665None
1666--
1667skin
16681.n. [Well Completions]
1669A dimensionless factor calculated to determine the production efficiency of a well by comparing actual conditions with theoretical or ideal conditions. A positive skin value indicates some damage or influences that are impairing well productivity. A negative skin value indicates enhanced productivity, typically resulting from stimulation.
1670None
1671None
1672None
1673--
1674skin
16752.n. [Well Testing]
1676The zone of reduced or enhanced permeability around a wellbore, often explained by formation damage and mud-filtrate invasion during drilling or perforating, or by well stimulation.
1677None
1678None
1679None
1680--
1681ssma copolymer
16821.n. [Drilling Fluids]
1683A copolymer of polystyrene (containing sulfonate groups on the ring) and anhydrous maleic acid (a di-hydroxy acid). The sulfonated ring-structure polymer component is anionic and usually low to moderate in chain length and molecular weight. As such, with negative groups on the structure (amount of negativity depending on degree of sulfonation), it is used as a clay deflocculant for bentonite-based water mud. It is especially stable to temperature up to around 400°F [204°C], and often used in high-density muds to stabilize rheology. Lignosulfonate is used for this purpose up to about 300°F [149°C] and then SSMA polymeric deflocculant is often phased into the mud system for drilling deeper and hotter zones.
1684None
1685None
1686sulfonated polystyrene-maleic anhydride copolymer
1687--
1688surface casing
16891.n. [Drilling]
1690A large-diameter, relatively low-pressure pipe string set in shallow yet competent formations for several reasons. First, the surface casing protects fresh-water aquifers onshore. Second, the surface casing provides minimal pressure integrity, and thus enables a diverter or perhaps even a blowout preventer (BOP) to be attached to the top of the surface casing string after it is successfully cemented in place. Third, the surface casing provides structural strength so that the remaining casing strings may be suspended at the top and inside of the surface casing.
1691aquifer, blowout preventer, casing string, casinghead, cellar, cementing
1692surface pipe
1693None
1694--
1695seismic processing
16961.n. [Geophysics]
1697Alteration of seismic data to suppress noise, enhance signal and migrate seismic events to the appropriate location in space. Processing steps typically include analysis of velocities and frequencies, static corrections, deconvolution, normal moveout, dip moveout, stacking, and migration, which can be performed before or after stacking. Seismic processing facilitates better interpretation because subsurface structures and reflection geometries are more apparent.
1698amplitude variation with offset, automatic gain control, common midpoint method, depth migration, dip moveout, filter, migration, normal moveout, quicklook, slant stack, stack, static correction, time migration, wavelet extraction
1699processing
1700None
1701--
1702skin factor
17031.n. [Well Testing]
1704A numerical value used to analytically model the difference from the pressure drop predicted by Darcy's law due to skin. Typical values for the skin factor range from -6 for an infinite-conductivity massive hydraulic fracture to more than 100 for a poorly executed gravel pack. This value is highly dependent on the value of kh. For example, a 20-psi [138-kPa] total pressure drop related to skin effect could produce almost any skin factor, depending on the value of kh. For any given pressure drop from skin effect, the skin factor increases proportionally as kh increases.
1705gravel pack, hydraulic fracturing, permeability thickness, skin effect
1706None
1707None
1708--
1709stabbing valve
17101.n. [Well Workover and Intervention]
1711A valve that is connected to the work string in the event that the well starts to flow when running or retrieving the string. A stabbing valve generally is kept on the rig floor as a contingency against unexpected well flow. On snubbing operations, a stabbing valve, or safety valve, is kept in the workbasket to protect against tubing plug or backpressure valve failure.
1712snubbing basket
1713None
1714None
1715--
1716surface controlled subsurface safety valve scssv
17171.n. [Well Completions]
1718A downhole safety valve that is operated from surface facilities through a control line strapped to the external surface of the production tubing. Two basic types of SCSSV are common: wireline retrievable, whereby the principal safety-valve components can be run and retrieved on slickline, and tubing retrievable, in which the entire safety-valve assembly is installed with the tubing string. The control system operates in a fail-safe mode, with hydraulic control pressure used to hold open a ball or flapper assembly that will close if the control pressure is lost.
1719downhole safety valve (DSV), production string, subsurface safety valve (SSSV)
1720None
1721None
1722--
1723seismic section
17241.n. [Geophysics]
1725A display of seismic data along a line, such a 2D seismic profile or a profile extracted from a volume of 3D seismic data. A seismic section consists of numerous traces with location given along the x-axis and two-way traveltime or depth along the y-axis. The section is called a depth section if the section has been converted from time to depth and a time section if this has not been done.
1726arrival, depth conversion, event, header, synthetic seismogram, trace, two-dimensional survey
1727seismic line
1728None
1729--
1730slam retarder
17311.n. [Production]
1732A device to prevent the clapper of a check valve from slamming as it closes upon flow reversal. Hydraulic damping cylinders, rotary vanes and torsional springs are all used for this purpose.
1733None
1734None
1735None
1736--
1737stability meter
17381.n. [Drilling Fluids]
1739A piece of equipment required to conduct the electrical stability (ES) test, a test for oil-base and synthetic-base muds that indicates the emulsion and oil-wetting qualities of the sample. The test is performed by inserting the ES probe into a cup of 120°F [48.9°C] mud and pushing a test button. The ES meter automatically applies an increasing voltage (from 0 to 2000 volts) across an electrode gap in the probe. Maximum voltage that the mud will sustain across the gap before conducting current is displayed as the ES voltage. The modern ES meter has sine-wave circuitry, whereas older meters used square-wave circuits. (The older units should not be used because they do not correctly address the theory described in the reference below.) The ES sine-wave design and meaning of ES readings have been studied and were found to relate to an oil mud's oil-wetting of solids and to stability of the emulsion droplets in a complex fashion not yet understood.Reference:Growcock FB, Ellis CF and Schmidt DD: "Electrical Stability, Emulsion Stability, and Wettability of Invert Oil-Based Muds," SPE Drilling & Completion 9, no. 1 (March 1994): 39-46.
1740high-pressure, high-temperature filtration test, jar test, oil mud, oil-base mud, synthetic-base mud, wettability
1741electrical stability test
1742None
1743--
1744surface pipe
17451.n. [Drilling]
1746Another term for surface casing, a large-diameter, relatively low-pressure pipe string set in shallow yet competent formations for several reasons. First, the surface casing protects fresh-water aquifers onshore. Second, the surface casing provides minimal pressure integrity, and thus enables a diverter or perhaps even a blowout preventer (BOP) to be attached to the top of the surface casing string after it is successfully cemented in place. Third, the surface casing provides structural strength so that the remaining casing strings may be suspended at the top and inside of the surface casing.
1747aquifer, blowout preventer, casing string, casinghead, cellar, cementing
1748surface casing
1749None
1750--
1751seismic stratigraphy
17521.n. [Geophysics]
1753Another term for sequence stratigraphy, a field of study in which basin-filling sedimentary deposits, called sequences, are interpreted in a framework of eustasy, sedimentation and subsidence through time in order to correlate strata and predict the stratigraphy of relatively unknown areas. Sequences tend to show cyclicity of changes in relative sea level and widespread unconformities, processes of sedimentation and sources of sediments, climate and tectonic activity over time. Sequence stratigraphic study promotes thorough understanding of the evolution of basins, but also allows for interpretations of potential source rocks and reservoir rocks in both frontier areas (having seismic data but little well data) and in more mature hydrocarbon provinces. Prediction of reservoir continuity is currently a key question in mature hydrocarbon provinces where sequence stratigraphy is being applied.The field originated during the 1960s with the study of the stratigraphy of the continental USA, where numerous unconformities could be correlated widely, and led to the proposal that major unconformities might mark synchronous global-scale events. Through sequence stratigraphy, widely-separated sediments that occur between correlatable unconformities could be compared with each other. Studies of outcrops and seismic lines bore out these concepts, which initially were called "Seismic Stratigraphy" and first published widely in 1977. Further study of seismic lines led to the interpretation of the geometry or architecture of seismic events as representing particular styles of sedimentation and depositional environments, and the integration of such interpretations with well log and core data. Because of the simultaneous, competitive nature of the research, numerous oil companies and academic groups use the terminology of sequence stratigraphy differently, and new terms are added continually.
1754condensed section, hiatus, onlap, parasequence, sequence boundary, sequence stratigraphy, source rock, systems tract
1755None
1756None
1757--
1758slant hole rig
17591.n. [Drilling]
1760A specially designed drilling rig capable of drilling directional wells.
1761directional well
1762None
1763None
1764--
1765stabilized gas well
17661.n. [Well Testing]
1767A gas well producing at a constant rate in which wellhead pressure changes no more than a small amount as a function of time. The actual amount of change permitted in a given time period to allow a well to be designated as stabilized may be fixed by law. Alternatively, the target stabilization for rigorous flow-after-flow testing in gas wells is pseudosteady-state flow, and this may be recognized as the pressure change versus time predicted from formation properties and drainage area size.
1768flow-after-flow tests, pseudosteady state
1769None
1770None
1771--
1772surface pressure
17731.n. [Well Testing]
1774The pressure measured at or near the surface in a well. This measurement of pressure is usually performed by inserting a gauge into the production string just below the shut-in valve, and is also referred to as tubing-head pressure.
1775production string
1776None
1777None
1778--
1779seismic velocity
17801.n. [Geophysics]
1781The rate at which a seismic wave travels through a medium, that is, distance divided by traveltime. Seismic velocity can be determined from vertical seismic profiles or from velocity analysis of seismic data. It can vary vertically, laterally and azimuthally in anisotropic media 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.
1782velocity, velocity survey, wavelength
1783None
1784None
1785--
1786slant rig
17871.n. [Drilling]
1788A specially designed drilling rig capable of drilling directional wells.
1789directional well
1790None
1791None
1792--
1793stack
17941.n. [Geophysics]
1795A processed seismic record that contains traces that have been added together from different records to reduce noise and improve overall data quality. The number of traces that have been added together during stacking is called the fold.
1796bin, brute stack, common midpoint, common midpoint method, fold, ground roll, noise, processing, random noise, seismic record, semblance, slant stack, stacking velocity, velocity analysis, zero-offset data
1797None
1798None
1799--
1800stack
18012.vb. [Geophysics]
1802To sum traces to improve the signal-to-noise ratio, reduce noise and improve seismic data quality. Traces from different shot records with a common reflection point, such as common midpoint (CMP) data, are stacked to form a single trace during seismic processing. Stacking reduces the amount of data by a factor called the fold.
1803bin, common midpoint, fold, mute, noise, processing, seismic record, signal-to-noise ratio, trace
1804None
1805None
1806--
1807surface tension
18081.n. [Drilling Fluids]
1809Surface free energy that exists between a liquid and air. Surface tension can be observed as a curved meniscus in a small tube of the liquid. This energy barrier prevents a liquid (such as water) from spontaneously mixing with air to form a foam. To make a foam, as used for a drilling fluid, the liquid's surface tension must be lowered by adding a third component (a foamer) that accumulates at the interface. Foam preparation usually requires mechanical energy to break up the bulk liquid into thin films around each gas bubble.
1810emulsion, emulsion mud, HLB number, interfacial tension, invert emulsion, invert-emulsion oil mud, meniscus, oil mud, oil/water ratio
1811None
1812None
1813--
1814seismology
18151.n. [Geophysics]
1816The study of seismic or elastic waves, such as from earthquakes, explosions or other causes. Interpretation of the structure and composition of the Earth from artificially created seismic waves is a chief concern of seismologists exploring for hydrocarbons and other resources. English physicist John Mitchell (1724 to 1793) is known as the founder of seismology in part because of his observation that one can determine an earthquake's epicenter, or point of origin in the subsurface, by measuring the arrival time of earthquake waves at different locations. The invention of the modern seismograph in 1880 promoted further studies of earthquakes.
1817birefringence, earthquake, elastic, reflection tomography, seismograph, shadow zone, wave
1818None
1819None
1820--
1821slant hole rig
18221.n. [Drilling]
1823A specially designed drilling rig capable of drilling directional wells.
1824directional well
1825None
1826None
1827--
1828stage separation
18291.n. [Production Facilities]
1830An operation in which the well stream is passed through two or more separators that are arranged in series. The first separator is called first-stage separator, the second separator is called second-stage separator and additional separators are named according to their position in the series. The operating pressures are sequentially reduced, so the highest pressure is found at the first separator and the lowest pressure at the final separator.The objective of stage separation is to maximize the hydrocarbon liquid recovery and to provide maximum stabilization to the resultant phases (liquid and gas) leaving the final separator. Stabilization means that considerable amounts of gas or liquid will not evolve from the final liquid and gas phases, respectively, in places such as stock tanks or gas pipelines. Additionally, stage separation reduces the horsepower required by a compressor, since the gas is fed at higher pressures.
1831None
1832None
1833None
1834--
1835surface controlled subsurface safety valve scssv
18361.n. [Well Completions]
1837A downhole safety valve that is operated from surface facilities through a control line strapped to the external surface of the production tubing. Two basic types of SCSSV are common: wireline retrievable, whereby the principal safety-valve components can be run and retrieved on slickline, and tubing retrievable, in which the entire safety-valve assembly is installed with the tubing string. The control system operates in a fail-safe mode, with hydraulic control pressure used to hold open a ball or flapper assembly that will close if the control pressure is lost.
1838downhole safety valve (DSV), production string, subsurface safety valve (SSSV)
1839None
1840None
1841--
1842semblance
18431.n. [Geophysics]
1844A quantitative measure of the coherence of seismic data from multiple channels that is equal to the energy of a stacked trace divided by the energy of all the traces that make up the stack. If data from all channels are perfectly coherent, or show continuity from trace to trace, the semblance has a value of unity.
1845channel, coherence, coherence, stack
1846None
1847None
1848--
1849slickline
18501.n. [Well Completions]
1851A thin nonelectric cable used for selective placement and retrieval of wellbore hardware, such as plugs, gauges and valves located in sidepocket mandrels. Valves and sleeves can also be adjusted using slickline tools. Partially collapsed tubing can be repaired using a tubing swage on slickline.
1852side-pocket mandrel
1853None
1854None
1855--
1856slickline
18572.n. [Well Workover and Intervention]
1858A single-strand wireline used to run and retrieve tools and flow-control equipment in oil and gas wells. The single round strand of wire passes through a stuffing box and pressure-control equipment mounted on the wellhead to enable slickline operations to be conducted safely on live wellbores.
1859None
1860None
1861None
1862--
1863staged fracturing
18641.n. [Shale Gas]
1865An operation in which numerous reservoir intervals are hydraulically stimulated in succession. Staged hydraulic fracturing operations are commonly performed from horizontal wellbores placed in shale gas reservoirs. Using geomechanical data, engineers are able to optimize the placement of perforations and fracturing stages to maximize gas production.
1866None
1867None
1868None
1869--
1870surfactant
18711.n. [Enhanced Oil Recovery, Drilling Fluids]
1872A chemical that preferentially adsorbs at an interface, lowering the surface tension or interfacial tension between fluids or between a fluid and a solid. This term encompasses a multitude of materials that function as emulsifiers, dispersants, oil-wetters, water-wetters, foamers and defoamers. The type of surfactant behavior depends on the structural groups on the molecule (or mixture of molecules). Hydrophile-lipophile balance (HLB) number helps define the function that a molecular group will perform.
1873amides, amines, breaker, cloud point, defoamer, dispersant, drilling detergent, emulsifier, foaming agent, gas hydrate, HLB number, hydrophile-lipophile balance number, hydrophilic, interfacial tension, lyophilic, lyophobic, quaternary amine, spotting fluid, surface tension
1874None
1875None
1876--
1877semisubmersible
18781.n. [Drilling]
1879A particular type of floating vessel that is supported primarily on large pontoon-like structures submerged below the sea surface. The operating decks are elevated perhaps 100 or more feet above the pontoons on large steel columns. This design has the advantage of submerging most of the area of components in contact with the sea and minimizing loading from waves and wind. Semisubmersibles can operate in a wide range of water depths, including deep water. They are usually anchored with six to twelve anchors tethered by strong chains and wire cables, which are computer controlled to maintain stationkeeping. Semisubmersibles (called semisubs or simply semis) can be used for drilling, workover operations, and production platforms, depending on the equipment with which they are equipped. When fitted with a drilling package, they may be called semisubmersible drilling rigs.
1880drillship, dynamic positioning, mobile offshore drilling unit, workover
1881None
1882None
1883--
1884slide
18851.vb. [Drilling]
1886To drill with a mud motor rotating the bit downhole without rotating the drillstring from the surface. This operation is conducted when the bottomhole assembly has been fitted with a bent sub or a bent housing mud motor, or both, for directional drilling. Sliding is the predominant method to build and control or correct hole angle in modern directional drilling operations. Directional drilling is conceptually simple: Point the bit in the desired direction. This pointing is accomplished through the bent sub, which has a small angle offset from the axis of the drillstring, and a measurement device to determine the direction of offset. Without turning the drillstring, the bit is rotated with a mud motor, and drills in the direction it points. With steerable motors, when the desired wellbore direction is attained, the entire drillstring is rotated and drills straight rather than at an angle. By controlling the amount of hole drilled in the sliding versus the rotating mode, the wellbore trajectory can be controlled precisely.
1887catwalk, directional drilling, mud motor, vee-door
1888None
1889None
1890--
1891slide
18922.n. [Drilling]
1893The escape device for workers on the rig floor should an emergency require prompt evacuation. It is similar to a child's playground slide, only longer and perhaps faster.
1894rig floor
1895None
1896None
1897--
1898slide
18993.n. [Drilling]
1900The inclined plane below the vee-door that connects the rig floor to the catwalk. This part of the rig is simply a reinforced steel plate, and is used as a guide when dragging equipment or pipes up into the derrick or to the rig floor. Equipment rests against the slide as it is pulled up to the drill floor. The lower end of pipe is guided by the slide as it is pulled into the derrick.
1901catwalk, derrick, rig floor, vee-door
1902None
1903None
1904--
1905stand
19061.n. [Drilling]
1907Two or three single joints of drillpipe or drill collars that remain screwed together during tripping operations. Most modern medium- to deep-capacity drilling rigs handle three-joint stands, called "trebles" or "triples." Some smaller rigs have the capacity for only two-joint stands, called "doubles." In each case, the drillpipe or drill collars are stood back upright in the derrick and placed into fingerboards to keep them orderly. This is a relatively efficient way to remove the drillstring from the well when changing the bit or making adjustments to the bottomhole assembly, rather than unscrewing every threaded connection and laying the pipe down to a horizontal position.
1908bottomhole assembly, connection, cut-and-thread fishing technique, fingerboard, make a connection, racking back pipe, short trip, slips, tripping pipe
1909None
1910None
1911--
1912surfactant flooding
19131.n. [Enhanced Oil Recovery]
1914An enhanced oil recovery process in which a small amount of surfactant is added to an aqueous fluid injected to sweep the reservoir. The presence of surfactant reduces the interfacial tension between the oil and water phases and also alters the wettability of the reservoir rock to improve oil recovery.
1915surfactant
1916None
1917None
1918--
1919sensitivity
19201.n. [Geophysics]
1921The smallest change in a measurement that can be recorded by an instrument.
1922None
1923None
1924None
1925--
1926sensitivity
19272.n. [Enhanced Oil Recovery]
1928In matrix stimulation, a characteristic of rock that indicates the degree of reaction between the rock minerals and a given treating fluid. A formation is described as sensitive if a given stimulating fluid damages the formation. The detrimental reactions include disaggregation and collapse of the matrix, release of fines or formation of precipitates.Sensitivity depends on the overall reactivity of the formation minerals with the fluid; reactivity depends on the structure of the rock and the distribution of minerals within the rock.Sandstone sensitivity also depends on permeability; low-permeability formations are normally more sensitive than high-permeability sandstones for a given mineralogy because certain types of damage, such as formation of precipitates, are more harmful in small pore throats (as in low-permeability formations).
1929compatibility, matrix stimulation, sandstone petrography
1930None
1931None
1932--
1933sliding sleeve
19341.n. [Well Completions]
1935A completion device that can be operated to provide a flow path between the production conduit and the annulus. Sliding sleeves incorporate a system of ports that can be opened or closed by a sliding component that is generally controlled and operated by slickline tool string.
1936None
1937None
1938None
1939--
1940standing valve
19411.n. [Well Completions]
1942A downhole valve assembly that is designed to hold pressure from above while allowing fluids to flow from below. Standing valves generally are run and retrieved on slickline with the valve assembly located in an appropriate nipple. Applications for standing valves include testing the tubing string, setting packers, or other applications in which it is desirable to maintain fluid in the tubing string.
1943packer
1944None
1945None
1946--
1947standing valve
19482.n. [Production Testing]
1949In a subsurface sucker-rod pump, a valve that permits flow up the tubing to fill the pump-barrel chamber while preventing downward flow.
1950pump barrel, rod pump
1951None
1952None
1953--
1954surfactant alternating gas
19551.n. [Enhanced Oil Recovery]
1956An enhanced oil recovery process in which alternating slugs of a surfactant solution and gas are injected into a reservoir. The injected surfactant and gas mix and generate foam that reduces the gas mobility, especially in previously swept or high-permeability regions of the reservoir. This improves sweep efficiency by mitigating gravity override and viscous fingering during gas injection. The presence of the surfactant in the injectant can also improve recovery by reducing interfacial tension between reservoir oil and the injection phases.
1957gas injection, surfactant
1958None
1959sag
1960--
1961separator
19621.n. [Production Facilities]
1963A cylindrical or spherical vessel used to separate oil, gas and water from the total fluid stream produced by a well. Separators can be either horizontal or vertical.Separators can be classified into two-phase and three-phase separators (commonly called free-water knockout). The two-phase type deals only with oil and gas, while the three-phase type handles oil, water and gas. Additionally, separators can be categorized according to their operating pressure. Low-pressure units handle pressures of 10 to 180 psi [69 to 1241 kPa]. Medium-pressure separators operate from 230 to 700 psi [1586 to 4826 kPa]. High-pressure units handle pressures of 975 to 1500 psi [6722 to 10,342 kPa].Gravity segregation is the main force that accomplishes the separation, which means the heaviest fluid settles to the bottom and the lightest fluid rises to the top. Additionally, inside the vessel, the degree of separation between gas and liquid will depend on the separator operating pressure, the residence time of the fluid mixture and the type of flow of the fluid. Turbulent flow allows more bubbles to escape than laminar flow.
1964free-water knockout, horizontal separator, oil and gas separator, spherical separator, stage separation, three-phase separator, two-phase separator, vertical separator
1965None
1966None
1967--
1968slim hole well
19691.n. [Drilling]
1970An inexact term describing a borehole (and associated casing program) significantly smaller than a standard approach, commonly a wellbore less than 6 in. in diameter. The slimhole concept has its roots in the observed correlation between well costs and volume of rock extracted. If one can extract less rock, then well costs should fall. One form of slimhole work involves using more or less conventional equipment and procedures, but simply reducing the hole and casing sizes for each hole interval. A second form involves technology used for exploration boreholes in the hard rock mining industry. In the mining rig operations, the drillstem serves a dual purpose. After the hole is drilled, the drillstem remains in the hole and is cemented in place. Then a new drillstem is used for the new hole section, and also cemented in place. The drillstring for mining rig operations is rotated like that for conventional oilfield rotary rig operations, but typically at a much higher speed.
1971None
1972None
1973slimhole well
1974--
1975standoff
19761.n. [Perforating]
1977The space between the shaped charge and the internal surface of the perforating gun body. The standoff is generally sufficient to allow the shaped charge jet to form before exiting the gun body.
1978perforating gun
1979None
1980None
1981--
1982standoff
19832.n. [Formation Evaluation]
1984The distance between the external surface of a logging tool and the borehole wall. This distance has an important effect on the response of some logging measurements, notably induction and neutron porosity logs. For resistivity tools, the effect of standoff is taken into account in the borehole correction. In the neutron porosity tool, it is usually corrected for separately. In a smooth, regular hole, the standoff is constant and determined by the geometry of the logging tool string and the borehole. In rugose or irregular holes, standoff varies with depth.
1985borehole correction, cave effect, neutron porosity
1986None
1987None
1988--
1989standoff
19903.n. [Formation Evaluation]
1991A piece of material designed to hold a logging tool a certain distance away from the borehole wall. It is usually made of hard rubber and consists of four to six fins of the desired length.
1992None
1993None
1994None
1995--
1996surge
19971.n. [Production]
1998A surge is the transient sudden rise or fall of pressure in a pipeline. Pipeline surges can be positive or negative and are caused most frequently by the sudden closure of a block valve or emergency shutdown of a pump. Surge pressure in excess of the rated capacity of a pipeline can cause ruptures of the piping system.
1999None
2000None
2001None
2002--
2003sequence stratigraphy
20041.n. [Geology]
2005A field of study in which basin-filling sedimentary deposits, called sequences, are interpreted in a framework of eustasy, sedimentation and subsidence through time in order to correlate strata and predict the stratigraphy of relatively unknown areas. Sequences tend to show cyclicity of changes in relative sea level and widespread unconformities, processes of sedimentation and sources of sediments, climate and tectonic activity over time. Sequence stratigraphic study promotes thorough understanding of the evolution of basins, but also allows for interpretations of potential source rocks and reservoir rocks in both frontier areas (having seismic data but little well data) and in more mature hydrocarbon provinces. Prediction of reservoir continuity is currently a key question in mature hydrocarbon provinces where sequence stratigraphy is being applied.The field originated during the 1960s with the study of the stratigraphy of the continental USA, where numerous unconformities could be correlated widely, and led to the proposal that major unconformities might mark synchronous global-scale events. Through sequence stratigraphy, widely-separated sediments that occur between correlatable unconformities could be compared with each other. Studies of outcrops and seismic lines bore out these concepts, which initially were called "Seismic Stratigraphy" and first published widely in 1977. Further study of seismic lines led to the interpretation of the geometry or architecture of seismic events as representing particular styles of sedimentation and depositional environments, and the integration of such interpretations with well log and core data. Because of the simultaneous, competitive nature of the research, numerous oil companies and academic groups use the terminology of sequence stratigraphy differently, and new terms are added continually.
2006accommodation, aggradation, basin, chronostratigraphic chart, condensed section, correlation, depositional environment, downlap, eustasy, hiatus, onlap, parasequence, plate tectonics, progradation, regression, reservoir, retrogradation, sedimentation, sequence, sequence boundary, source rock, stratigraphy, stratum, subsidence, systems tract, transgression, unconformity
2007None
2008None
2009--
2010slimhole well
20111.n. [Drilling]
2012An inexact term describing a borehole (and associated casing program) significantly smaller than a standard approach, commonly a wellbore less than 6 in. in diameter. The slimhole concept has its roots in the observed correlation between well costs and volume of rock extracted. If one can extract less rock, then well costs should fall. One form of slimhole work involves using more or less conventional equipment and procedures, but simply reducing the hole and casing sizes for each hole interval. A second form involves technology used for exploration boreholes in the hard rock mining industry. In the mining rig operations, the drillstem serves a dual purpose. After the hole is drilled, the drillstem remains in the hole and is cemented in place. Then a new drillstem is used for the new hole section, and also cemented in place. The drillstring for mining rig operations is rotated like that for conventional oilfield rotary rig operations, but typically at a much higher speed.
2013None
2014None
2015None
2016--
2017starch
20181.n. [Drilling Fluids]
2019A drilling-mud additive used to control fluid loss in water muds ranging from freshwater to saturated-salt to high-pH lime muds. Starches have thermal stability to about 250°F [121°C]. They are subject to bacterial attack unless protected by high salinity or bactericide. Drilling-grade natural starch has API/ISO specifications for quality. Starches are carbohydrates of a general formula (C6H10O5)n and are derived from corn, wheat, oats, rice, potatoes, yucca and similar plants and vegetables. They consist of about 27% linear polymer (amylose) and about 73% branched polymer (amylopectin). The two polymers are intertwined within starch granules. Granules are insoluble in cold water, but soaking in hot water or under steam pressure ruptures their covering and the polymers hydrate into a colloidal suspension. This product is a pregelatinized starch and has been used in muds for many years. Amylose and amylopectin are nonionic polymers that do not interact with electrolytes. Derivatized starches, such as hydroxypropyl and carboxymethyl starches, are used in drill-in fluids, completion fluids and various brine systems as well as in drilling-mud systems. The use of starch typically causes a minimal increase in viscosity while effectively controlling fluid loss.
2020colloid, completion fluid, emulsion mud, gyp mud, hydroxypropyl starch, lime mud, methylglucoside drilling fluid, paraformaldehyde, potassium mud, pregelatinized starch, quebracho, red mud, saltwater mud, soft water
2021HP starch
2022None
2023--
2024survey
20251.n. [Geophysics]
2026A data set measured and recorded with reference to a particular area of the Earth's surface, such as a seismic survey.
2027accelerometer, base station, baseline, baseline, benchmark, benchmark, cultural noise, depth point, drift, electromagnetic method, free-air correction, gravity, gravity survey, magnetics, monument, perpendicular offset, salt proximity survey, seismic, side-scan sonar, telluric-current method
2028None
2029None
2030--
2031survey
20322.vb. [Geophysics]
2033To measure and record data according to location on the Earth's surface. In geophysics, the term is used in the context of acquiring seismic, electrical, gravity or magnetic data to evaluate the subsurface.
2034acquisition
2035None
2036None
2037--
2038survey
20393.n. [Drilling]
2040A 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.
2041azimuth, deviation survey, directional drilling, directional survey, inclination, measurements-while-drilling, total depth, tripping pipe
2042None
2043None
2044--
2045survey
20464.n. [Drilling]
2047A precise and legally binding measurement of surface locations, referenced to known benchmark locations.
2048None
2049None
2050None
2051--
2052survey
20535.vb. [Drilling]
2054To make the measurements as in definitions 1 or 2.
2055None
2056None
2057None
2058--
2059survey
20606.n. [Formation Evaluation]
2061The measurement versus depth or time, or both, of one or more physical quantities in or around a well. In early years, the term was used more often than log.
2062None
2063log
2064electrical survey
2065--
2066survey
20677.vb. [Formation Evaluation]
2068To record a measurement versus depth or time, or both, of one or more physical quantities in or around a well. In early years, the term was used more often than log.
2069None
2070log
2071None
2072--
2073sequential gaussian simulation
20741.n. [Reservoir Characterization]
2075A procedure for estimating the reservoir characteristics between data points. Based on the idea of iterating from a first guess and refining through reduction of errors, the procedure generally transforms the model to normality, simulating the normally distributed transform, and then back-transforming to the original variable of interest.
2076None
2077None
2078None
2079--
2080slip lock
20811.n. [Well Completions]
2082A downhole lock device, run on slickline, that incorporates a slip mechanism that engages on the tubing wall to anchor the lock at the desired setting depth. Slip locks are not depth-dependent and do not require special completion equipment. However, the slip lock has limited function and pressure capacity and is generally less desirable than nipple or collar locks.
2083collar lock, lock
2084None
2085None
2086--
2087static aging test
20881.n. [Drilling Fluids]
2089A mud test in which the mud sample is not agitated. This test is usually performed at a selected high temperature. Typically, the mud sample is sealed in a mud-aging cell and placed in an oven for a given period of time (often 16 hours, overnight). The cooled mud is tested before it is stirred. Commonly, the sample is retested after it has been stirred. Static-aged mud, before it is stirred, simulates a mud that is static in a well while pipe is out of the hole during a bit trip or logging run. The stirred mud simulates the same mud after arriving at the surface and after being agitated by mud guns and through centrifugal pumps. The amount and kind of mud treatment are determined from these tests.
2090None
2091None
2092static-aging test
2093--
2094swab
20951.vb. [Drilling]
2096To reduce pressure in a wellbore by moving pipe, wireline tools or rubber-cupped seals up the wellbore. If the pressure is reduced sufficiently, reservoir fluids may flow into the wellbore and towards the surface. Swabbing is generally considered harmful in drilling operations, because it can lead to kicks and wellbore stability problems. In production operations, however, the term is used to describe how the flow of reservoir hydrocarbons is initiated in some completed wells.
2097kick, volumetric efficiency, well control
2098None
2099None
2100--
2101swab
21022.vb. [Well Completions]
2103To unload liquids from the production tubing to initiate flow from the reservoir. A swabbing tool string incorporates a weighted bar and swab cup assembly that are run in the wellbore on heavy wireline. When the assembly is retrieved, the specially shaped swab cups expand to seal against the tubing wall and carry the liquids from the wellbore.
2104None
2105None
2106None
2107--
2108sequestering agent
21091.n. [Drilling Fluids]
2110A chemical whose molecular structure can envelop and hold a certain type of ion in a stable and soluble complex. Divalent cations, such as hardness ions, form stable and soluble complex structures with several types of sequestering chemicals. When held inside the complex, the ions have a limited ability to react with other ions, clays or polymers. Ethylenediamine tetraacetic acid (EDTA) is a well-known sequestering agent for the hardness ions, such as Ca+2, and is the reagent solution used in the hardness test protocol published by API. Polyphosphates can also sequester hardness ions. The addition of sodium acid pyrophosphate (SAPP) to a cement-contaminated mud renders the calcium ions essentially nonreactive with clays in the mud. As a side benefit, SAPP also lowers mud pH. Sequestering is not the same as precipitation because sequestering does not form a solid.
2111EDTA, hardness ion, oxygen scavenger, precipitation, SAPP, scavenger, sulfide scavenger
2112None
2113None
2114--
2115sequestering agent
21162.n. [Well Completions, Drilling Fluids, Well Workover and Intervention]
2117Another term for chelating agent, a chemical used to bind metal ions to form a ring structure. Chelating agents stabilize or prevent the precipitation of damaging compounds. In the oil field, chelating agents are used in stimulation treatments and for cleaning surface facilities. They are also used to treat or remove scale or weighting agents in reservoir drilling fluids.During acid or scale-removal treatments, various compounds may be dissolved in the treatment fluid. As the acid reacts and the pH increases, reaction products may precipitate as a gelatinous, insoluble mass. Should this occur within the formation matrix, it is almost impossible to remove and permanent permeability damage may occur. Chelating agents prevent precipitation by keeping ions in a soluble form until the treatment fluid can be flowed back from the formation during cleanup.Typical oilfield chelating agents include EDTA (ethylenediamine tetraacetic acid), HEDTA (hydroxyethylenediamine triacetic acid), NTA (nitriolotriacetic acid) and citric acid.
2118acetic acid, chelation, reducing agent
2119chelating agent
2120None
2121--
2122sequestering agent
21233.n. [Enhanced Oil Recovery]
2124Another term for chelating agent, a chemical added to an acid to stabilize iron. The injected acid dissolves iron from rust, millscale, iron scales or iron-containing minerals in the formation. Iron can exist as ferric iron [Fe+3] or ferrous iron [Fe+2]. If the iron is not controlled, it will precipitate insoluble products such as ferric hydroxide and, in sour environments, ferrous sulfide [FeS], which will damage the formation.Chelating agents associate with iron [Fe+3 or Fe+2] to form soluble complexes. Citric acid, acetic acid and EDTA are effective chelating agents and can be used at temperatures up to 400oF [204oC].
2125reducing agent
2126None
2127chelating agent
2128--
2129slips
21301.n. [Drilling]
2131A device used to grip the drillstring in a relatively nondamaging manner and suspend it in the rotary table. This device consists of three or more steel wedges that are hinged together, forming a near circle around the drillpipe. On the drillpipe side (inside surface), the slips are fitted with replaceable, hardened tool steel teeth that embed slightly into the side of the pipe. The outsides of the slips are tapered to match the taper of the rotary table. After the rig crew places the slips around the drillpipe and in the rotary, the driller slowly lowers the drillstring. As the teeth on the inside of the slips grip the pipe, the slips are pulled down. This downward force pulls the outer wedges down, providing a compressive force inward on the drillpipe and effectively locking everything together. Then the rig crew can unscrew the upper portion of the drillstring (kelly, saver sub, a joint or stand of pipe) while the lower part is suspended. After some other component is screwed onto the lower part of the drillstring, the driller raises the drillstring to unlock the gripping action of the slips, and the rig crew removes the slips from the rotary.
2132kelly, make a connection, rotary table, saver sub, spinning chain, stand
2133None
2134None
2135--
2136slips
21372.n. [Drilling]
2138Any self-gripping toothed device functioning substantially as above, but gripping components other than drillstring, such as wireline, metal sinker bars, or drill collars.
2139drill collar, sinker bar
2140None
2141None
2142--
2143static correction
21441.n. [Geophysics]
2145Often called statics, a bulk shift of a seismic trace in time during seismic processing. A common static correction is the weathering correction, which compensates for a layer of low seismic velocity material near the surface of the Earth. Other corrections compensate for differences in topography and differences in the elevations of sources and receivers.
2146base of weathering, brute stack, differential weathering correction, dynamic correction, elevation correction, first break, moveout, processing, receiver, source, velocity, weathered layer, weathering correction
2147None
2148near surface correction, near-surface correction, statics
2149--
2150swage
21511.n. [Well Completions]
2152A threaded adapter used to connect a circulating line to a casing or tubing string. A casing or tubing swage generally is required as a contingency option to enable any obstruction or fill to be circulated clear during the running process.
2153None
2154None
2155None
2156--
2157swage
21582.n. [Production]
2159A tool for bending or forming cold metal to a required shape.
2160None
2161None
2162None
2163--
2164settling pit
21651.n. [Drilling]
2166A drilling mud filled open steel or earthen berm tank that is not stirred or circulated. By having mud slowly pass through such a container, most large drilling solids sink to the bottom, cleaning the mud somewhat. If the settling pit is small, as in the case of steel mud tanks, it must be cleaned out frequently as cuttings pile up on the bottom of the tank. In the early days of rotary drilling, some rigs had no more solids control than a large settling pit into which mud was discharged after coming back from the wellbore and suction for the mud pumps was taken at the other end of the pit. A major drawback to this type of "cleaning" is that solids intentionally put into the mud, such as barite, may settle to the bottom and be discarded rather than circulated back into the wellbore.
2167barite, cuttings, rotary drilling
2168None
2169None
2170--
2171sloughing shale
21721.n. [Drilling Fluids]
2173A fine-grained, impermeable, sedimentary rock composed of clays and other minerals, usually with a high percentage of quartz. Shale is the most common, and certainly the most troublesome, rock type that must be drilled in order to reach oil and gas deposits. The characteristic that makes shales most troublesome to drillers is its water sensitivity, due in part to its clay content and the ionic composition of the clay. For this reason, oil-base drilling fluids are the mud of choice to drill the most water-sensitive shales.
2174activity of aqueous solutions, balanced-activity oil mud, cation-exchange capacity, Chenevert Method, clay, clay-water interaction, drilling detergent, encapsulation, gumbo, inhibit, inhibitive mud, montmorillonite, native clay, oil mud, pore-pressure transmission, potassium ion, relative humidity, silicate mud, synthetic-base mud
2175None
2176None
2177--
2178static filter press
21791.n. [Drilling Fluids]
2180A pressurized cell, fitted with a filter medium, used for evaluatingfiltrationcharacteristics of a drilling fluid while it is static in the test cell. Generally, either low-pressure, low-temperature orhigh-pressure, high-temperaturedevices are used.
2181drilling fluid, dynamic filter press, filter cell, filter medium, filter press, filter-cake quality, filter-cake thickness, filtrate, filtration, filtration test cell, fluid-loss control, fluid-loss-control material, high-pressure, high-temperature filtration test, low-pressure, low-temperature filtration test, spurt loss, static filtration
2182None
2183None
2184--
2185swaging tool
21861.n. [Well Workover and Intervention]
2187A downhole tool, generally run on slickline, that is used to open collapsed or damaged tubing. Configured with a tapered profile, the swaging tool acts as a circular wedge to force the tubing wall out as it is driven through a collapsed or restricted area. A jar is included in the tool string to provide the impact force necessary to push the swaging tool through the tubing restriction.
2188None
2189None
2190None
2191--
2192settling tank
21931.n. [Drilling]
2194Another term for settling pit, a drilling mud filled open steel or earthen berm tank that is not stirred or circulated. By having mud slowly pass through such a container, most large drilling solids sink to the bottom, cleaning the mud somewhat. If the settling pit is small, as in the case of steel mud tanks, it must be cleaned out frequently as cuttings pile up on the bottom of the tank. In the early days of rotary drilling, some rigs had no more solids control than a large settling pit into which mud was discharged after coming back from the wellbore and suction for the mud pumps was taken at the other end of the pit. A major drawback to this type of "cleaning" is that solids intentionally put into the mud, such as barite, may settle to the bottom and be discarded rather than circulated back into the wellbore.
2195barite, cuttings, rotary drilling
2196None
2197None
2198--
2199slowing down length
22001.n. [Formation Evaluation]
2201A parameter used to characterize neutron interactions in bulk material above the thermal region. The slowing-down length (Ls) is proportional to the root-mean-square distance from the point of emission of a high-energy neutron to the point at which its energy has decreased to the lower edge of the epithermal energy region. The slowing-down length is the physical parameter that best describes the response of an epithermal neutron porosity measurement, and describes a large part of the response of a thermal neutron porosity measurement. Thermal neutrons have about the same energy as the surrounding matter, typically less than about 0.4 eV, while epithermal neutrons have higher energy, between about 0.4 and 10 eV.
2202epithermal neutron porosity measurement, neutron interactions, slowing-down time, thermal diffusion length, thermal neutron porosity measurement
2203None
2204None
2205--
2206static seal
22071.n. [Production]
2208A sealing element used as a gasket between two nonmoving parts, for example, valve bonnet O-rings, ball valve body O-rings and flange gaskets.
2209None
2210None
2211None
2212--
2213s wave
22141.n. [Geophysics]
2215An elastic body wave in which particles oscillate perpendicular to the direction in which the wave propagates. S-waves are generated by most land seismic sources, but not by air guns. P-waves that impinge on an interface at non-normal incidence can produce S-waves, which in that case are known as converted waves. S-waves can likewise be converted to P-waves. S-waves, or shear waves, travel more slowly than P-waves and cannot travel through fluids because fluids do not support shear. Recording of S-waves requires receivers coupled to the solid Earth. Interpretation of S-waves can allow determination of rock properties such as fracture density and orientation, Poisson's ratio and rock type by crossplotting P-wave and S-wave velocities, and by other techniques.
2216acoustic, acoustic wave, body wave, converted wave, dilatancy theory, elastic, four-component seismic data, fracture, hodogram, P-wave, Poisson's ratio, seismic, SH-wave, shadow zone, shear, Snell's law, SV-wave, wave
2217shear wave, tangential wave
2218None
2219--
2220severance
22211.n. [Oil and Gas Business]
2222The separation of mineral and/or royalty interest from fee-simple title. Severance of interests is usually accomplished by reservation in a deed or assignment or by conveyance in mineral or royalty deed, assignment or lease.
2223conveyance, horizontal severance, mineral interest, royalty interest, vertical severance
2224None
2225None
2226--
2227slowing down time
22281.n. [Formation Evaluation]
2229With reference to pulsed neutron logging, the characteristic time for the decay of the epithermal neutron population. The slowing-down time of a formation is strongly dependent on the porosity. In openhole pulsed neutron logging, it is also dependent on the standoff between tool and borehole wall. Epithermal neutrons have energies above that of the surrounding matter, between about 0.4 eV and 10 eV.
2230epithermal neutron porosity measurement, slowing-down length
2231None
2232None
2233--
2234static spontaneous potential
22351.n. [Formation Evaluation]
2236The ideal spontaneous potential (SP) that would be observed opposite a permeable bed if the SP currents were prevented from flowing and any shaliness in the bed were ignored. The static spontaneous potential (SSP) is equal to the electrochemical potential. When current is flowing, the SP measures only that fraction of the potential drop that occurs in the borehole. In normal conditions, this potential drop is much higher than the drop in the formation because the cross-sectional area of the borehole is much smaller, and hence its resistance much higher. It is for this reason that in the middle of a thick, clean bed whose resistivity is not too high, the SP reads close to the SSP. However, in other conditions the SP is significantly less than the SSP.As well as ignoring shaliness in the sand, the SSP ignores other sources of potential and assumes a surrounding shale that is a perfect cationic membrane.
2237electrokinetic potential, liquid-junction potential, membrane potential, pseudostatic spontaneous potential, shale baseline
2238None
2239None
2240--
2241sweep efficiency
22421.n. [Enhanced Oil Recovery]
2243A measure of the effectiveness of an enhanced oil recovery process that depends on the volume of the reservoir contacted by the injected fluid. The volumetric sweep efficiency is an overall result that depends on the injection pattern selected, off-pattern wells, fractures in the reservoir, position of gas-oil and oil/water contacts, reservoir thickness, permeability and areal and vertical heterogeneity, mobility ratio, density difference between the displacing and the displaced fluid, and flow rate.
2244gas-oil contact, oil-water contact
2245None
2246None
2247--
2248shadow zone
22491.n. [Geophysics]
2250Generally, an area of the Earth from which waves do not emerge or cannot be recorded. In seismology, the term is used to more specifically describe regions of the subsurface where P-waves and S-waves are difficult to detect, such as regions of the core at certain distances from the epicenter of an earthquake, or the point on the Earth's surface directly above an earthquake. Such zones were first observed in 1914 by Beno Gutenberg (1889 to 1960), an American geologist born in Germany. Because of the molten nature of the outer core, S-waves are especially difficult to detect at 103 to 142 degrees from the epicenter of an earthquake and not observable from 142 to 180 degrees from the epicenter. Areas below salt features are also called shadow zones because the high velocity of salt bends and traps energy, so seismic data quality beneath salt is generally poor unless special seismic processing is performed.
2251blind zone, P-wave, S-wave, seismology
2252None
2253None
2254--
2255slowness
22561.n. [Formation Evaluation, Geophysics]
2257Also called interval transit time, The amount of time for a wave to travel a certain distance, proportional to the reciprocal of velocity, typically measured in microseconds per foot by an acoustic log and symbolized by t or DT. P-wave interval transit times for common sedimentary rock types range from 43 (dolostone) to 160 (unconsolidated shales) microseconds per foot, and can be distinguished from measurements of steel casing, which has a consistent transit time of 57 microseconds per foot.
2258acoustic, drift, P-wave
2259delta t, interval transit time
2260None
2261--
2262static aging test
22631.n. [Drilling Fluids]
2264A mud test in which the mud sample is not agitated. This test is usually performed at a selected high temperature. Typically, the mud sample is sealed in a mud-aging cell and placed in an oven for a given period of time (often 16 hours, overnight). The cooled mud is tested before it is stirred. Commonly, the sample is retested after it has been stirred. Static-aged mud, before it is stirred, simulates a mud that is static in a well while pipe is out of the hole during a bit trip or logging run. The stirred mud simulates the same mud after arriving at the surface and after being agitated by mud guns and through centrifugal pumps. The amount and kind of mud treatment are determined from these tests.
2265barrel equivalent, mud oven, mud-aging cell, pilot test, rolling-aging test, shear-strength measurement test, temperature stability
2266dynamic-aging test
2267None
2268--
2269sweep pill
22701.n. [Well Completions]
2271A relatively small volume of viscous fluid, typically a carrier gel, that is circulated to sweep, or remove, debris or residual fluids from the circulation system.
2272None
2273None
2274None
2275--
2276shaker
22771.n. [Drilling]
2278Abbreviation for shale shaker, the primary and probably most important device on the rig for removing drilled solids from the mud. This vibrating sieve is simple in concept, but a bit more complicated to use efficiently. A wire-cloth screen vibrates while the drilling fluid flows on top of it. The liquid phase of the mud and solids smaller than the wire mesh pass through the screen, while larger solids are retained on the screen and eventually fall off the back of the device and are discarded. Obviously, smaller openings in the screen clean more solids from the whole mud, but there is a corresponding decrease in flow rate per unit area of wire cloth. Hence, the drilling crew should seek to run the screens (as the wire cloth is called), as fine as possible, without dumping whole mud off the back of the shaker. Where it was once common for drilling rigs to have only one or two shale shakers, modern high-efficiency rigs are often fitted with four or more shakers, thus giving more area of wire cloth to use, and giving the crew the flexibility to run increasingly fine screens.
2279cuttings, desander
2280None
2281shale shaker
2282--
2283sludge
22841.n. [Enhanced Oil Recovery]
2285A thick, viscous emulsion containing oil, water, sediment and residue that forms because of the incompatibility of certain native crude oils and strong inorganic acids used in well treatments.Use of certain additives, such as surfactants, or the presence of dissolved iron can promote sludge formation, especially if asphaltenes are present in the crude oil. Therefore, it is important to test a sample of crude with the treating fluid before injecting a treatment into a reservoir.
2286crude oil, surfactant, treatment fluid
2287None
2288None
2289--
2290stationarity
22911.n. [Reservoir Characterization]
2292A form of homogeneity in a single characteristic. Local stationarity occurs when two or more adjacent, locally homogeneous samples yield similar values of the property of interest.
2293None
2294None
2295None
2296--
2297sweet corrosion
22981.n. [Well Completions]
2299The deterioration of metal due to contact with carbon dioxide or similar corrosive agents, but excluding hydrogen sulfide [H2S]. Sweet corrosion typically results in pitting or material loss and occurs where steel is exposed to carbon dioxide and moisture.
2300None
2301None
2302None
2303--
2304sweet corrosion
23052.n. [Enhanced Oil Recovery]
2306The corrosion caused by contact with carbon dioxide [CO2] dissolved in water.In gas condensate wells, sweet corrosion takes the form of deep pitting inside the tubing walls. The pitting is produced only at depths where the acidic gas contacts condensed water droplets.
2307acid gas, sour gas
2308None
2309None
2310--
2311shale
23121.n. [Geology, Shale Gas]
2313A fine-grained, fissile, detrital sedimentary rock formed by consolidation of clay- and silt-sized particles into thin, relatively impermeable layers. It is the most abundant sedimentary rock. Shale can include relatively large amounts of organic material compared with other rock types and thus has potential to become a rich hydrocarbon source rock, even though a typical shale contains just 1% organic matter. Its typical fine grain size and lack of permeability, a consequence of the alignment of its platy or flaky grains, allow shale to form a good cap rock for hydrocarbon traps.Gas shows from shales during drilling have led some shales to be targeted as potential gas reservoirs. Various clay types and volumes influence the quality of the reservoir from a petrophysical and geomechanical perspective. The quality of shale reservoirs depends on their thickness and extent, organic content, thermal maturity, depth and pressure, fluid saturations, and permeability, among other factors.
2314cap rock, clastic sediment, clay, detrital, diapir, formation pressure, illite, impermeable, lamination, pore pressure, seal, sedimentary, shaly, siliciclastic sediment, source rock, trap
2315None
2316None
2317--
2318shale
23192.n. [Drilling Fluids]
2320A fine-grained, impermeable, sedimentary rock composed of clays and other minerals, usually with a high percentage of quartz. Shale is the most common, and certainly the most troublesome, rock type that must be drilled in order to reach oil and gas deposits. The characteristic that makes shales most troublesome to drillers is its water sensitivity, due in part to its clay content and the ionic composition of the clay. For this reason, oil-base drilling fluids are the mud of choice to drill the most water-sensitive shales.
2321activity of aqueous solutions, balanced-activity oil mud, cation-exchange capacity, Chenevert Method, clay, clay-water interaction, drilling detergent, encapsulation, gumbo, inhibit, inhibitive mud, montmorillonite, native clay, oil mud, pore-pressure transmission, potassium ion, relative humidity, silicate mud, synthetic-base mud
2322None
2323sloughing shale
2324--
2325slug
23261.n. [Drilling Fluids]
2327A volume of mud that is more dense than the mud in the drillpipe and wellbore annulus. A slug is used to displace mud out of the upper part of the drillpipe before pulling pipe out of the hole and is mixed in the pill pit by adding additional weighting material (barite) to a few barrels of mud from the surface pits. The pill is pumped into the top of the drillstring to push mud downward, out of the pipe, thus keeping the upper stands of pipe empty.
2328mud, mud weight, U-tube effect, weighting material
2329slugging pill
2330None
2331--
2332slug
23332.n. [Well Workover and Intervention]
2334A small volume of fluid, often of a higher density than the main body of fluid, within the circulating or production-fluid system that influences the flow or production characteristics of the well. A slug may be placed to ensure that fluids are naturally drained from a tubing string as it is pulled from the wellbore. The term may also be applied to a small volume of liquid produced from a gas well. Similarly, it is used to describe the flow characteristics that occur when a mixture of liquid and gas result in a sporadic production regime as the liquids are unloaded erratically.
2335None
2336None
2337None
2338--
2339steady state behavior
23401.n. [Well Testing]
2341Simultaneously constant pressure (wellhead or bottomhole) and flow rate. This behavior can result when there is pressure support, either naturally through an aquifer or gas-cap drive, or artificially through water or gas injection.
2342gas injection, gas-cap drive
2343None
2344None
2345--
2346sweet crude
23471.n. [Well Completions]
2348Crude oil containing low levels of sulfur compounds, especially hydrogen sulfide [H2S]. The facilities and equipment to handle sweet crude are significantly simpler than those required for other potentially corrosive types of crude oil.
2349None
2350None
2351None
2352--
2353shale baseline
23541.n. [Formation Evaluation]
2355The average reading of the spontaneous potential (SP) log opposite the shale layers in a well. Opposite shales, the SP is relatively constant and changes only slowly with depth. This is the shale baseline. The log is normally adjusted by the logging engineer to read near zero at the baseline. Sharp shifts in the baseline can sometimes be observed, for example when two permeable beds with different formation water salinities are separated by a shale that is not a perfect cationic membrane, or when the formation water salinity changes within a permeable bed.
2356bimetallism, fish
2357None
2358None
2359--
2360slug flow
23611.n. [Well Completions]
2362A multiphase-fluid flow regime characterized by a series of liquid plugs (slugs) separated by a relatively large gas pockets. In vertical flow, the bubble is an axially symmetrical bullet shape that occupies almost the entire cross-sectional area of the tubing. The resulting flow alternates between high-liquid and high-gas composition.
2363multiphase fluid flow
2364None
2365None
2366--
2367slug flow
23682.n. [Production Logging]
2369A multiphase-flow regime in pipes in which most of the lighter fluid is contained in large bubbles dispersed within, and pushing along, the heavier fluid. The word slug normally refers to the heavier, slower moving fluid, but sometimes to the bubbles of lighter fluid. There are also small bubbles within the liquid, but many of these have coalesced to form the large bubbles until they span much of the pipe. In gas-liquid mixtures, slug flow is similar to plug flow, but the bubbles are generally larger and move faster. As flow rates increase, slug flow becomes churn flow.
2370bubble flow, churn flow, flow structure, froth flow, multiphase flow, plug flow
2371None
2372None
2373--
2374slug flow
23753.n. [Production Testing]
2376A type of flow in which surface equipment may be damaged by the sudden impact of a liquid slug in a phenomenon called water hammer.
2377None
2378None
2379None
2380--
2381steady state behavior
23821.n. [Well Testing]
2383Simultaneously constant pressure (wellhead or bottomhole) and flow rate. This behavior can result when there is pressure support, either naturally through an aquifer or gas-cap drive, or artificially through water or gas injection.
2384gas injection, gas-cap drive
2385None
2386None
2387--
2388sweet crude oil
23891.n. [Production Testing]
2390Oil containing small amounts of hydrogen sulfide and carbon dioxide.
2391None
2392None
2393None
2394--
2395shale shaker
23961.n. [Drilling]
2397The primary and probably most important device on the rig for removing drilled solids from the mud. This vibrating sieve is simple in concept, but a bit more complicated to use efficiently. A wire-cloth screen vibrates while the drilling fluid flows on top of it. The liquid phase of the mud and solids smaller than the wire mesh pass through the screen, while larger solids are retained on the screen and eventually fall off the back of the device and are discarded. Obviously, smaller openings in the screen clean more solids from the whole mud, but there is a corresponding decrease in flow rate per unit area of wire cloth. Hence, the drilling crew should seek to run the screens (as the wire cloth is called), as fine as possible, without dumping whole mud off the back of the shaker. Where it was once common for drilling rigs to have only one or two shale shakers, modern high-efficiency rigs are often fitted with four or more shakers, thus giving more area of wire cloth to use, and giving the crew the flexibility to run increasingly fine screens.
2398cuttings, desander
2399None
2400shaker
2401--
2402slugging pill
24031.n. [Drilling Fluids]
2404Also called a slug, a volume of mud that is more dense than the mud in the drillpipe and wellbore annulus. A slug is used to displace mud out of the upper part of the drillpipe before pulling pipe out of the hole and is mixed in the pill pit by adding additional weighting material (barite) to a few barrels of mud from the surface pits. The pill is pumped into the top of the drillstring to push mud downward, out of the pipe, thus keeping the upper stands of pipe empty.
2405mud, mud weight, U-tube effect, weighting material
2406slug
2407trip pill
2408--
2409slugging pill
24102.n. [Well Workover and Intervention]
2411Another term for a slug, a small volume of fluid, often of a higher density than the main body of fluid, within the circulating or production-fluid system that influences the flow or production characteristics of the well. A slug may be placed to ensure that fluids are naturally drained from a tubing string as it is pulled from the wellbore.
2412None
2413slug
2414None
2415--
2416steam chamber
24171.n. [Enhanced Oil Recovery, Heavy Oil]
2418The volume of reservoir in which mobile steam exists for an extended period of time. Within the steam chamber, rock temperature rises to the point where steam vapor can be sustained at reservoir pressure conditions. The steam chamber is normally found in the upper portion of a reservoir sand between a steam injector and a producer, where steam has broken through to the producer. With time, the steam chamber can expand to cover an entire area of a five-spot pattern steamflood. For a steam assisted gravity drainage (SAGD) system, the steam chamber in a mature field project can extend from a broad area across the top of the sand to a narrow finger down to the producing horizontal well near the bottom of the sand. Also referred to as a steam chest.
2419reservoir pressure
2420None
2421None
2422--
2423sweet gas
24241.n. [Well Completions]
2425Natural gas that does not contain hydrogen sulfide [H2S] or significant quantities of carbon dioxide [CO2].
2426None
2427None
2428Antonyms:sour gas
2429--
2430sweet gas
24312.n. [Production Testing]
2432Natural gas that contains small amounts of hydrogen sulfide and carbon dioxide.
2433None
2434None
2435None
2436--
2437shaly
24381.adj. [Geology, Shale Gas]
2439Containing shale, a fine-grained, fissile, detrital sedimentary rock formed by consolidation of clay- and silt-sized particles into thin, relatively impermeable layers. It is the most abundant sedimentary rock. Shale can include relatively large amounts of organic material compared with other rock types and thus has potential to become a rich hydrocarbon source rock, even though a typical shale contains just 1% organic matter. Its typical fine grain size and lack of permeability, a consequence of the alignment of its platy or flaky grains, allow shale to form a good cap rock for hydrocarbon traps.Gas shows from shales during drilling have led some shales to be targeted as potential gas reservoirs. Various clay types and volumes influence the quality of the reservoir from a petrophysical and geomechanical perspective. The quality of shale reservoirs depends on their thickness and extent, organic content, thermal maturity, depth and pressure, fluid saturations, and permeability, among other factors.
2440cap rock, clastic sediment, clay, detrital, diapir, formation pressure, illite, impermeable, lamination, pore pressure, seal, sedimentary, shaly, siliciclastic sediment, source rock, trap
2441None
2442None
2443--
2444shaly
24452.adj. [Drilling Fluids]
2446Containing shale, a fine-grained, impermeable, sedimentary rock composed of clays and other minerals, usually with a high percentage of quartz. Shale is the most common, and certainly the most troublesome, rock type that must be drilled in order to reach oil and gas deposits. The characteristic that makes shales most troublesome to drillers is its water sensitivity, due in part to its clay content and the ionic composition of the clay. For this reason, oil-base drilling fluids are the mud of choice to drill the most water-sensitive shales.
2447cap rock, clastic sediment, clay, detrital, diapir, formation pressure, illite, impermeable, lamination, pore pressure, seal, sedimentary, siliciclastic sediment, source rock, trap
2448None
2449None
2450--
2451slurry
24521.n. [Drilling Fluids]
2453A mixture of suspended solids and liquids. Muds in general are slurries, but are seldom called that. Cement is a slurry and is often referred to as such.
2454drill-in fluid, dynamic filtration, filter cake, gunk plug, material-balance equation, mud, oil mud, pressurized mud balance, slurries
2455None
2456None
2457--
2458steam flood
24591.n. [Heavy Oil, Enhanced Oil Recovery, Well Completions]
2460A method of thermal recovery in which steam generated at surface is injected into the reservoir through specially distributed injection wells.When steam enters the reservoir, it heats up the crude oil and reduces its viscosity. The heat also distills light components of the crude oil, which condense in the oil bank ahead of the steam front, further reducing the oil viscosity. The hot water that condenses from the steam and the steam itself generate an artificial drive that sweeps oil toward producing wells.Another contributing factor that enhances oil production during steam injection is related to near-wellbore cleanup. In this case, steam reduces the interfacial tension that ties paraffins and asphaltenes to the rock surfaces while steam distillation of crude oil light ends creates a small solvent bank that can miscibly remove trapped oil. Steamflooding is also called continuous steam injection or steam drive.
2461cyclic steam injection, enhanced oil recovery, hot waterflooding, in-situ combustion, paraffin, secondary recovery
2462None
2463None
2464--
2465sweetening
24661.n. [Production Facilities]
2467A process used to remove hydrogen sulfide [H2S] and carbon dioxide [CO2] from a gas stream. These components are removed because they can form acidic solutions when they contact water, which will cause corrosion problems in gas pipelines.In a sweetening process, different types of ethanolamine can be used, including monoethanolamine (MEA), diethanolamine (DEA), diglycolamine (DGA) and methyldiethanolamine (MDEA). Hydrogen sulfide and carbon dioxide are absorbed by the ethanolamine and sweet gas leaves at the top of the absorber.The ethanolamine is heated and acid gas (hydrogen sulfide and carbon dioxide gases) and water vapor are obtained. The water is removed while the acid gas can be flared or further treated in a sulfur recovery unit to separate out elemental sulfur. Finally, the lean ethanolamine is returned to the absorber.
2468flare, sour gas
2469None
2470None
2471--
2472shaped charge
24731.n. [Geophysics]
2474Explosives designed to affect a certain direction preferentially. Shaped charges are most commonly used to perforate wells, but can be an energy source for seismic acquisition.
2475directivity
2476None
2477perforating charge
2478--
2479shaped charge
24802.n. [Perforating]
2481An explosive device that utilizes a cavity-effect explosive reaction to generate a high-pressure, high-velocity jet that creates a perforation tunnel. The shape of the explosive material and powdered metal lining determine the shape of the jet and performance characteristics of the charge. The extremely high pressure and velocity of the jet cause materials, such as steel, cement and rock formations, to flow plastically around the jet path, thereby creating the perforation tunnel.
2482perforating gun
2483perforating charge
2484None
2485--
2486slurry density
24871.n. [Drilling Fluids]
2488The weight per unit volume of a cement slurry, usually given in units of kg/m3 or lbm/gal. Typical oil- or gas-well slurries have densities of 1380 kg/m3 to 2280 kg/m3 [11.5 lbm/gal to 19.0 lbm/gal], although special techniques, such as foamed cementing and particle-size distribution cementing, extend this range to 840 kg/m3 to 2760 kg/m3 [7 lbm/gal to 23 lbm/gal].
2489foamed cement
2490None
2491None
2492--
2493steam management
24941.n. [Heavy Oil]
2495The overall heat and fuel management for a steam injection process. It includes economically efficient use of fuel consumed to generate steam, minimization of heat losses in surface steam-distribution lines, proper splitting of steam flow and quality and intersections in steam-distribution lines, and effective management of steam and heat distribution in the reservoir.
2496None
2497None
2498None
2499--
2500swellable packer
25011.n. [Drilling, Well Completions]
2502An isolation device that relies on elastomers to expand and form an annular seal when immersed in certain wellbore fluids. The elastomers used in these packers are either oil- or water-sensitive. Their expansion rates and pressure ratings are affected by a variety of factors. Oil-activated elastomers, which work on the principle of absorption and dissolution, are affected by fluid temperature as well as the concentration and specific gravity of hydrocarbons in a fluid. Water-activated elastomers are typically affected by water temperature and salinity. This type of elastomer works on the principle of osmosis, which allows movement of water particles across a semi-permeable membrane based on salinity differences in the water on either side of the membrane.
2503None
2504None
2505None
2506--
2507shear modulus
25081.n. [Geophysics]
2509An elastic constant for the ratio of shear stress to shear strain. The shear modulus is one of the Lamé constants. It can be expressed mathematically as follows:
2510None
2511None
2512None
2513--
2514slurry service
25151.n. [Production]
2516An application involving a flowing medium consisting of small solid particles suspended in a liquid. Coal slurry consisting of about equal parts of coal and water is transported by pipeline from coal mines to plants where the coal is dewatered and burned.
2517None
2518None
2519None
2520--
2521steam soak
25221.n. [Enhanced Oil Recovery, Heavy Oil]
2523Another term for soak phase, in cyclic steam injection, the second phase between the steam-injection phase and the production phase. During the soak phase, the well is shut in for several days to allow uniform heat distribution to thin the oil.
2524thermal recovery
2525soak phase
2526None
2527--
2528swivel
25291.n. [Drilling]
2530A mechanical device that suspends the weight of the drillstring. It is designed to allow rotation of the drillstring beneath it conveying high volumes of high-pressure drilling mud between the rig's circulation system and the drillstring.
2531hook, kelly hose, standpipe, traveling block
2532None
2533None
2534--
2535shear ram
25361.n. [Well Workover and Intervention, Drilling]
2537Ablowoutpreventer (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.
2538blind ram, blowout, blowout preventer, BOP stack, drillstring, kill, shear-seal BOP
2539blind shear ram
2540None
2541--
2542slurry yield
25431.n. [Drilling Fluids]
2544The volume of slurry obtained when one sack of cement is mixed with the desired amount of water and other additives, usually given in units of m3/kg or ft3/sk (sack).
2545None
2546None
2547None
2548--
2549steam trap
25501.n. [Enhanced Oil Recovery]
2551A barrier or resistance to the flow of injected steam formed by a volume around a producing well in a steamflood that contains high oil and liquid water saturation. This is typically maintained by choking the production well to keep the surrounding formation just below saturated steam temperature and pressure conditions. It is used in the steam-assisted gravity-drainage process.
2552steamflood
2553None
2554None
2555--
2556syncline
25571.n. [Geology]
2558Basin- or trough-shaped fold in rock in which rock layers are downwardly convex. The youngest rock layers form the core of the fold and outward from the core progressively older rocks occur. Synclines typically do not trap hydrocarbons because fluids tend to leak up the limbs of the fold. An anticline is the opposite type of fold, having upwardly-convex layers with old rocks in the core.
2559anticline, fold, structural trap, structure, trap
2560None
2561Antonyms:anticline
2562--
2563shear rate
25641.n. [Drilling Fluids]
2565The velocity gradient measured across the diameter of a fluid-flow channel, be it a pipe, annulus or other shape. Shear rate is the rate of change of velocity at which one layer of fluid passes over an adjacent layer. As an example, consider that a fluid is placed between two parallel plates that are 1.0 cm apart, the upper plate moving at a velocity of 1.0 cm/sec and the lower plate fixed. The fluid layer at the lower plate is not moving and the layer nearest the top plate is moving at 1.0 cm/sec. Halfway between the plate, a layer is moving at 0.5 cm/sec. The velocity gradient is the rate of change of velocity with distance from the plates. This simple case shows the uniform velocity gradient with shear rate (v1 - v2)/h = shear rate = (cm/sec)/(cm/1) = 1/sec. Hence, shear rate units are reciprocal seconds.
2566apparent viscosity, attapulgite, Bingham plastic model, Brookfield viscometer, centipoise, dynamic filtration, gel strength, Herschel-Bulkley fluid, high-pressure, high-temperature viscometer, Newtonian fluid, non-Newtonian fluid, plastic fluid, plastic viscosity, power-law fluid, pseudoplastic, rheological property, rheology, shear stress, viscosity, yield point
2567rate of shear
2568None
2569--
2570small pore water
25711.n. [Formation Evaluation]
2572Water in microporosity or other small pores. The term usually refers to the nuclear magnetic resonance signal of such water, which occurs at very short times and overlaps the signal from clay-bound water.
2573clay-bound water, effective porosity, nuclear magnetic resonance, total porosity
2574None
2575None
2576--
2577steam assisted gravity drainage
25781.n. [Heavy Oil, Enhanced Oil Recovery]
2579A thermal production method for heavy oil that pairs a high-angle injection well with a nearby production well drilled along a parallel trajectory. The pair of high-angle wells is drilled with a vertical separation of about 5 m [16 ft]. Steam is injected into the reservoir through the upper well. As the steam rises and expands, it heats up the heavy oil, reducing its viscosity. Gravity forces the oil to drain into the lower well where it is produced.
2580heavy oil, injection well
2581None
2582SAGD
2583--
2584synthetic base mud
25851.n. [Drilling Fluids]
2586Nonaqueous, water-internal (invert) emulsion muds in which the external phase is a synthetic fluid rather than an oil. This and other more minor changes in formulations have made synthetic fluids in muds more environmentally acceptable for offshore use. Synthetic muds are popular in most offshore drilling areas, despite high initial mud costs, because of their environmental acceptance and approval to dispose of cuttings into the water. "Oil mud" should not be used to describe synthetic-base muds.
2587synthetic-base mud
2588None
2589None
2590--
2591shear stock
25921.n. [Well Completions]
2593The material from which shear pins are typically cut. Shear stock is precision-manufactured in a range of sizes and material characteristics to provide predictable performance from the shear pin and the tool in which it is installed.
2594shear pin
2595None
2596None
2597--
2598shear stock
25992.n. [Well Workover and Intervention]
2600The bar or rod from which shear pins are cut for use in downhole slickline tools. Shear stock is prepared from carefully monitored materials to precise dimensions to ensure predictable and repeatable performance of shear pins.
2601None
2602None
2603None
2604--
2605small pore water
26061.n. [Formation Evaluation]
2607Water in microporosity or other small pores. The term usually refers to the nuclear magnetic resonance signal of such water, which occurs at very short times and overlaps the signal from clay-bound water.
2608clay-bound water, effective porosity, nuclear magnetic resonance, total porosity
2609None
2610None
2611--
2612steamflood
26131.n. [Heavy Oil, Enhanced Oil Recovery, Well Completions]
2614A method of thermal recovery in which steam generated at surface is injected into the reservoir through specially distributed injection wells.When steam enters the reservoir, it heats up the crude oil and reduces its viscosity. The heat also distills light components of the crude oil, which condense in the oil bank ahead of the steam front, further reducing the oil viscosity. The hot water that condenses from the steam and the steam itself generate an artificial drive that sweeps oil toward producing wells.Another contributing factor that enhances oil production during steam injection is related to near-wellbore cleanup. In this case, steam reduces the interfacial tension that ties paraffins and asphaltenes to the rock surfaces while steam distillation of crude oil light ends creates a small solvent bank that can miscibly remove trapped oil. Steamflooding is also called continuous steam injection or steam drive.
2615cyclic steam injection, enhanced oil recovery, hot waterflooding, in-situ combustion, paraffin, secondary recovery
2616None
2617None
2618--
2619synthetic seismogram
26201.n. [Geophysics]
2621The result of one of many forms of forward modeling to predict the seismic response of the Earth. A more narrow definition used by seismic interpreters is that a synthetic seismogram, commonly called a synthetic, is a direct one-dimensional model of acoustic energy traveling through the layers of the Earth. The synthetic seismogram is generated by convolving the reflectivity derived from digitized acoustic and density logs with the wavelet derived from seismic data. By comparing marker beds or other correlation points picked on well logs with major reflections on the seismic section, interpretations of the data can be improved. The quality of the match between a synthetic seismogram depends on well log quality, seismic data processing quality, and the ability to extract a representative wavelet from seismic data, among other factors. The acoustic log is generally calibrated with check-shot or vertical seismic profile (VSP) first-arrival information before combining with the density log to produce acoustic impedance.
2622check-shot survey, convolution, forward modeling, marker bed, multiple reflection, one-dimensional seismic data, phase, reflection, reflection coefficient, Ricker wavelet, seismic modeling, seismic record, seismic section, shotpoint, trace, velocity, vertical seismic profile
2623None
2624None
2625--
2626shear strain
26271.n. [Geology]
2628The amount of deformation by shearing, in which parallel lines slide past each other in differing amounts. The measurement is expressed as the tangent of the change in angle between lines that were initially perpendicular.
2629strain, stress
2630None
2631None
2632--
2633smectite clay
26341.n. [Drilling Fluids]
2635A category of clay minerals that have a three-layer crystalline structure (one alumina and two silica layers) and that exhibit a common characteristic of hydrational swelling when exposed to with water. Montmorillonite is a well-known smectite clay mineral to those working in drilling and drilling fluids. Its sodium form, bentonite, is a widely-used water mud additive. It is also used as an oil-mud additive when made oil-dispersible by surface treatment. Smectite clays that occur naturally in shales cause wellbore and mud-control problems due to their hydrational swelling and colloidal dispersion characteristics.
2636bentonite, clay, clay-water interaction, colloidal solids, gumbo, montmorillonite
2637None
2638None
2639--
2640stem
26411.n. [Well Workover and Intervention]
2642The weight bar used in slickline operations to overcome the effects of wellhead pressure and friction at the surface seal where the wire enters the wellbore. In addition to a solid steel stem, a special high-density stem is available with internal cavities filled with lead, tungsten or mercury alloys.
2643None
2644None
2645None
2646--
2647stem
26482.n. [Production]
2649A rod or shaft transmitting motion from an operator to the closure element of a valve.
2650None
2651None
2652None
2653--
2654synthetic seismograms
26551.n. [Reservoir Characterization]
2656The seismic traces at a wellbore generated from wireline log data. Synthetic seismograms are generated by calculating reflection coefficients from the sonic and density logs and then applying an ideal or real wavelet to the reflections to obtain the seismic "wiggle" traces. Synthetic seismograms are usually generated to compare with the actual seismic data and identify reflectors with layers and formations already known in the wellbore.
2657sonic log
2658None
2659None
2660--
2661shear stress
26621.n. [Drilling Fluids]
2663The force per unit area required to sustain a constant rate of fluid movement. Mathematically, shear stress can be defined as:τ = F/A,whereτ = shear stessF = shear forceA = Area acted on by the shear force.If a fluid is placed between two parallel plates spaced 1.0 cm apart, and a force of 1.0 dyne is applied to each square centimeter of the surface of the upper plate to keep it in motion, the shear stress in the fluid is 1 dyne/cm2 at any point between the two plates.
2664Bingham plastic model, Brookfield viscometer, centipoise, gel strength, Herschel-Bulkley fluid, high-pressure, high-temperature viscometer, Newtonian fluid, non-Newtonian fluid, plastic fluid, plastic viscosity, power-law fluid, pseudoplastic, rheological property, rheology, shear rate, viscosity, yield point
2665None
2666None
2667--
2668snub
26691.vb. [Drilling]
2670To put drillpipe into the wellbore when the blowout preventers (BOPs) are closed and pressure is contained in the well. Snubbing is necessary when a kick is taken, since well kill operations should always be conducted with the drillstring on bottom, and not somewhere up the wellbore. If only the annular BOP has been closed, the drillpipe may be slowly and carefully lowered into the wellbore, and the BOP itself will open slightly to permit the larger diameter tool joints to pass through. If the well has been closed with the use of ram BOPs, the tool joints will not pass by the closed ram element. Hence, while keeping the well closed with either another ram BOP or the annular BOP, the ram must be opened manually, then the pipe lowered until the tool joint is just below the ram, and then closing the ram again. This procedure is repeated whenever a tool joint must pass by a ram BOP. In snubbing operations, the pressure in the wellbore acting on the cross-sectional area of the tubular can exert sufficient force to overcome the weight of the drillstring, so the string must be pushed (or "snubbed") back into the wellbore. In ordinary stripping operations, the pipe falls into the wellbore under its own weight, and no additional downward force or pushing is required.
2671annular blowout preventer, blowout preventer, kick, kill, ram blowout preventer, stripping, tool joint
2672None
2673None
2674--
2675snub
26762.vb. [Well Workover and Intervention]
2677To force a pipe or tubular into a well against wellborepressure. Well-intervention techniques in live wells, such ascoiled tubingandsnubbing, use equipment designed to apply the necessary forces while supporting the tubing and safely containing wellbore pressure and fluids.
2678None
2679None
2680None
2681--
2682step profile
26831.n. [Formation Evaluation]
2684With reference to invasion, an abrupt change from the flushed zone to the undisturbed zone, with no transition zone or annulus. This simple model is used most commonly in connection with older resistivity logs since it allows the invasion to be represented by three parameters: flushed-zone resistivity, undisturbed-zone resistivity and diameter of invasion. The model assumes equal invasion at all azimuths. Newer array logs allow more complex invasion models to be interpreted.
2685array induction, array laterolog, array propagation resistivity, diameter of invasion, filtrate slump, flushed zone, radial response, undisturbed zone
2686None
2687None
2688--
2689synthetic base mud
26901.n. [Drilling Fluids]
2691Nonaqueous, water-internal (invert) emulsion muds in which the external phase is a synthetic fluid rather than an oil. This and other more minor changes in formulations have made synthetic fluids in muds more environmentally acceptable for offshore use. Synthetic muds are popular in most offshore drilling areas, despite high initial mud costs, because of their environmental acceptance and approval to dispose of cuttings into the water. "Oil mud" should not be used to describe synthetic-base muds.
2692calcium chloride, conventional mud, diesel-oil mud, drilling fluid, electrical stability test, flash point, invert-emulsion oil mud, isomerized olefin, lignite, linear alphaolefin, oil content, oil mud, olefinic hydrocarbon, rheology modifier, shale, sheen test, spotting fluid, syn, synthetic-base fluid, synthetic/brine ratio, synthetic/water ratio, water-in-oil emulsion
2693None
2694None
2695--
2696t1
26971.n. [Formation Evaluation]
2698In a nuclear magnetic resonance measurement, the characteristic time for longitudinal relaxation. In rocks, longitudinal relaxation is the inverse sum of the surface relaxation and bulk relaxation. T1 is not normally measured in NMR logging, but is an important parameter in deciding the polarization time and hence the logging speed. T1 is closely related to the transverse relaxation time, T2. The ratio T1/T2 in water-filled rocks is typically between 1.5 and 2.5. In light hydrocarbons and gas, the ratio increases up to 10 and more as the viscosity decreases.
2699bulk relaxation, longitudinal relaxation, nuclear magnetic resonance measurement, relaxation time, transverse relaxation
2700None
2701None
2702--
2703thermal recovery
27041.n. [Heavy Oil, Enhanced Oil Recovery]
2705A general term for injection processes that introduce heat into a reservoir. Thermal recovery is used to produce viscous, thick oils with API gravities less than 20. These oils cannot flow unless they are heated and their viscosity is reduced enough to allow flow toward producing wells.During thermal recovery, crude oil undergoes physical and chemical changes because of the effects of the heat supplied. Physical properties such as viscosity, specific gravity and interfacial tension are altered. The chemical changes involve different reactions such as cracking, which is the destruction of carbon-carbon bonds to generate lower molecular weight compounds, and dehydrogenation, which is the rupture of carbon-hydrogen bonds.Thermal recovery is a major branch of enhanced oil recovery processes and can be subdivided in two types: hot fluid injection such as steam injection (steamflood or cyclic steam injection) and hot waterflooding and in-situ combustion processes.
2706API gravity, chemical flooding, miscible displacement
2707None
2708TEOR
2709--
2710time lapse
27111.adj. [Formation Evaluation]
2712Pertaining to techniques in which the same quantity is measured at different times in the life of a reservoir. Normally the only change in a time-lapse measurement orsurveywill be due to changes in water or gassaturation. Thus, a comparison of two logsrunat different times, such as a year apart, should simply reflect the change in fluid saturations in theporespace. The most common time-lapse logs are made with pulsedneutron capture, pulsed neutron spectroscopy andboreholegravity measurements.
2713acid effect, pulsed neutron spectroscopy log, sigma, time-lapse seismic data
2714None
2715None
2716--
2717trend
27181.n. [Geology]
2719The azimuth or orientation of a linear feature, such as the axis of a fold, normally expressed as a compass bearing.
2720azimuth, fold
2721None
2722None
2723--
2724trend
27252.n. [Geology]
2726Used synonymously with the term play to describe an area in which hydrocarbons occur, such as the Wilcox trend of the Gulf Coast.
2727play
2728None
2729None
2730--
2731t2
27321.n. [Formation Evaluation]
2733In nuclear magnetic resonance (NMR) logging, the characteristic time for transverse relaxation. In rocks, there are three components of the transverse relaxation: surface, Ts; bulk, Tb; and diffusion relaxation, Td. T2 is the inverse sum of each component for each fluid, as follows:1/T2 = 1/Ts + 1/Tb + 1/Td.Because of the reciprocal sum, the smallest of the three types of relaxations is the most important in determining the final T2 for each fluid. There is not one single value of T2 for a rock but a wide distribution of values lying anywhere between fractions of a millisecond and several seconds. The distribution of T2 values is the principal output of an NMR log.
2734bulk relaxation, longitudinal relaxation, nuclear magnetic resonance measurement, relaxation time, T1
2735None
2736None
2737--
2738thief hatch
27391.n. [Production Facilities]
2740An opening in the top of the stock tank. The thief hatch allows tank access for a thief or other level measuring devices.
2741None
2742None
2743None
2744--
2745timed slug analysis
27461.n. [Production Logging]
2747A technique for determining thevelocityoffluid flowin aninjection wellbased on measuring the time a slugofradioactive tracertakes to move down the well. The analysis is usually performed as part of a tracer-loss measurement. The depth of the slug is measured by running repeated gamma ray logs at well-defined time intervals. From the differences in depth and time, the velocity can be determined.
2748production log, radioactive-tracer log, tracer measurement, velocity-shot measurement
2749None
2750None
2751--
2752trip
27531.n. [Drilling]
2754The act of pulling thedrillstringout of the hole or replacing it in the hole. A pipe trip is usually done because thebithas dulled or has otherwise ceased to drill efficiently and must be replaced.
2755monkeyboard, round trip, short trip
2756tripping pipe
2757None
2758--
2759tail buoy
27601.n. [Geophysics]
2761A floating device used in marine seismic acquisition to identify the end of a streamer. Tail buoys allow the seismic acquisition crew to monitor the location and direction of streamers. They are commonly brightly colored, reflect radar signals, and are fitted with Global Positioning System (GPS) receivers.
2762acquisition, Global Positioning System, streamer
2763None
2764None
2765--
2766thinner
27671.n. [Drilling Fluids]
2768Another term for deflocculant, a thinning agent used to reduceviscosityor preventflocculation; incorrectly called a "dispersant." Most deflocculants are low-molecular weightanionicpolymers thatneutralizepositive charges onclayedges. Examples includepolyphosphates, lignosulfonates,quebrachoand various water-soluble synthetic polymers.
2769clay-water interaction, conventional mud, gel strength, polar compound, rheology, yield point
2770deflocculant
2771Antonyms:flocculant
2772--
2773timed slug analysis
27741.n. [Production Logging]
2775A technique for determining the velocity of fluid flow in an injection well based on measuring the time a slug of radioactive tracer takes to move down the well. The analysis is usually performed as part of a tracer-loss measurement. The depth of the slug is measured by running repeated gamma ray logs at well-defined time intervals. From the differences in depth and time, the velocity can be determined.
2776production log, radioactive-tracer log, tracer measurement, velocity-shot measurement
2777None
2778None
2779--
2780trip gas
27811.n. [Drilling]
2782Gas entrained in the drilling fluid during a pipe trip, which typically results in a significant increase in gas that is circulated to surface. This increase arises from a combination of two factors: lack of circulation when the mud pumps are turned off, and swabbing effects caused by pulling the drillstring to surface. These effects may be seen following a short trip into casing or a full trip to surface.
2783connection gas, short trip, tripping pipe
2784None
2785TG
2786--
2787tail cement
27881.n. [Drilling Fluids]
2789The last cement system pumped during primary cementing. The tail cement covers the lower sections of the well, especially planned completion intervals, and is typically more dense than the lead slurry that precedes it.
2790None
2791None
2792None
2793--
2794thorium
27951.n. [Formation Evaluation]
2796An element with an atomic number of 90. The 232Th isotope is radioactive and decays with a half-life of 1.4 * 1010 years through a series of intermediate isotopes to a stable isotope of lead. The intermediate isotopes emit a wide range of gamma rays, the most prominent being that of thallium, 208Tl. It is assumed that formations are in secular equilibrium; that is, the relative proportions of parent and daughter isotopes remain constant, and the measured spectrum is directly related to the amount of 232Th. The concentration in the Earth's crust is about 12 parts per million, ppm, by weight.Thorium-bearing minerals are rare. Thorium is a trace element associated with clays and heavy minerals. It is very immobile so that quantity measured today probably was present at the time of deposition. A log of thorium is presented in parts per million. It is often a good measure of clay content.
2797gamma ray log, natural gamma ray spectroscopy, potassium, uranium
2798None
2799None
2800--
2801time lapse
28021.adj. [Formation Evaluation]
2803Pertaining to techniques in which the same quantity is measured at different times in the life of a reservoir. Normally the only change in a time-lapse measurement or survey will be due to changes in water or gas saturation. Thus, a comparison of two logs run at different times, such as a year apart, should simply reflect the change in fluid saturations in the pore space. The most common time-lapse logs are made with pulsed neutron capture, pulsed neutron spectroscopy and borehole gravity measurements.
2804acid effect, pulsed neutron spectroscopy log, sigma, time-lapse seismic data
2805None
2806None
2807--
2808trip pill
28091.n. [Drilling Fluids]
2810Also called a slug, a volume of mud that is more dense than the mud in the drillpipe and wellbore annulus. A slug is used to displace mud out of the upper part of the drillpipe before pulling pipe out of the hole and is mixed in the pill pit by adding additional weighting material (barite) to a few barrels of mud from the surface pits. The pill is pumped into the top of the drillstring to push mud downward, out of the pipe, thus keeping the upper stands of pipe empty.
2811mud, mud weight, U-tube effect, weighting material
2812slug
2813None
2814--
2815tangential wave
28161.n. [Geophysics]
2817Also known as S-wave, an elastic body wave in which particles oscillate perpendicular to the direction in which the wave propagates. S-waves are generated by most land seismic sources, but not by air guns. P-waves that impinge on an interface at non-normal incidence can produce S-waves, which in that case are known as converted waves. S-waves can likewise be converted to P-waves. S-waves, or shear waves, travel more slowly than P-waves and cannot travel through fluids because fluids do not support shear. Recording of S-waves requires receivers coupled to the solid Earth. Interpretation of S-waves can allow determination of rock properties such as fracture density and orientation, Poisson's ratio and rock type by crossplotting P-wave and S-wave velocities, and by other techniques.
2818None
2819S-wave, shear wave
2820None
2821--
2822thousand standard cubic feet per day
28231.n. [Production Testing]
2824A common measure for volume of gas. Standard conditions are normally set at 60oF and 14.7 psia, abbreviated Mscf/d.
2825None
2826None
2827None
2828--
2829tiv
28301.n. [Geophysics]
2831Abbreviation for vertical transverse isotropy. Transverse isotropy that has a vertical axis of rotational symmetry. In layered rocks, properties are uniform horizontally within a layer, but vary vertically and from layer to layer.
2832None
2833None
2834vertical transverse isotropy, VTI
2835--
2836triplex pump
28371.n. [Well Workover and Intervention]
2838A positive-displacement reciprocating pump that is configured with three plungers. Triplex pumps are the most common configuration of pump used in both drilling and well service operations. Pumps used in well service activities generally are capable of handling a wide range of fluid types, including corrosive fluids, abrasive fluids and slurries containing relatively large particulates.
2839None
2840None
2841None
2842--
2843tank battery
28441.n. [Production Facilities]
2845A group of tanks that are connected to receive crude oil production from a well or a producing lease. A tank battery is also called a battery.In the tank battery, the oil volume is measured and tested before pumping the oil into the pipeline system.
2846None
2847None
2848None
2849--
2850thread protector
28511.n. [Drilling]
2852A cheap, expendable, perhaps even disposable threaded shape to mate with threads on drillstring and casing components. Thread protectors prevent harmful impacts and other contact to the metal thread surfaces. Some protectors are strong enough and are fitted with lifting eyes so that they may be screwed into a joint of drillpipe, a drill collar or another component and a chain tied to the eye for lifting the joint. Except for this type, most of the other available styles of thread protectors are relatively inexpensive, being made from thermoplastics and various epoxy resins.
2853drill collar
2854None
2855None
2856--
2857thread protector
28582.n. [Well Completions]
2859A protective sleeve or cap generally made up on the threads of tubular goods during transport and storage. Thread protectors are available in metal, plastic, or a combination of both.
2860None
2861None
2862None
2863--
2864tomography
28651.n. [Geophysics]
2866A technique to measure and display the three-dimensional distribution of velocity or reflectivity of a volume of the Earth by using numerous sources and receivers. There are several types of tomography used by geophysicists, including transmission tomography (which uses measurements between boreholes, surface-to-surface, or between a borehole and the surface), reflection or seismic tomography (based on standard reflection seismology), and diffraction tomography (using Fermat's principle for computations instead of Snell's law). Variations in velocity can be attributed to changes in density and elastic properties of rocks, which in turn are affected by the increasing temperature with depth in the Earth. Tomographic techniques have been used to construct maps of the Earth's interior, deep in the mantle, as well as for mapping the shallow subsurface by borehole tomography.
2867crosswell tomography, Fermat's principle, receiver, reflection tomography, Snell's law, source, velocity
2868None
2869None
2870--
2871tripping pipe
28721.n. [Drilling]
2873The act of pulling the drillstring out of the hole or replacing it in the hole. A pipe trip is usually done because the bit has dulled or has otherwise ceased to drill efficiently and must be replaced.
2874coiled tubing drilling, measurements-while-drilling, monkeyboard, round trip, stand, survey
2875pipe trip
2876None
2877--
2878tank bottoms
28791.n. [Production Facilities]
2880The settlings -- sediment, dirt, oil emulsified with water and free water -- that accumulate in the bottom of storage tanks. The tank bottoms are periodically cleaned up and settlings can be disposed of or treated by chemicals to recover additional hydrocarbons. Tank bottoms are also called tank settlings or tank sludge.
2881None
2882None
2883None
2884--
2885threadform
28861.n. [Drilling]
2887A particular style or type of threaded connection, especially as used for rotary shouldered connections. Threadforms come in a variety of sizes, pitches, tapers, threads per in., and individual thread profiles. Fortunately, each of these varieties has a published standard, either considered public and maintained by the American Petroleum Institute (API) or maintained by operating or service companies as proprietary information.
2888back off, break out, pin
2889None
2890None
2891--
2892tongs
28931.n. [Drilling]
2894Large-capacity, self-locking wrenches used to grip drillstring components and apply torque. As with opposing pipe wrenches for a plumber, the tongs must be used in opposing pairs. As a matter of efficiency, one set of tongs is essentially tied off with a cable or chain to the derrick, and the other is actively pulled with mechanical catheads. The breakout tongs are the active tongs during breakout (or loosening) operations. The makeup tongs are active during makeup (or tightening) operations.
2895breakout tongs, cat line, cathead, chain tongs, derrick, makeup cathead, tool joint
2896None
2897None
2898--
2899true resistivity
29001.n. [Formation Evaluation]
2901With reference to log analysis, the resistivity of the undisturbed formation. It is derived from a resistivity log that has been corrected as far as possible for all environmental effects, such as borehole, invasion and surrounding bed effects. Hence, it is taken as the true resistivity of the undisturbed formation in situ and is called Rt.
2902in situ, water-filled resistivity
2903None
2904None
2905--
2906true resistivity
29072.n. [Formation Evaluation]
2908With reference to core analysis, the resistivity of a sample only partially filled with water. Called Rt, it is used in contrast to the resistivity of a sample completely filled with water, Ro. The water may be replaced by any nonconductive fluid, usually air or dead oil.
2909dead oil
2910None
2911None
2912--
2913tank dike
29141.n. [Production Facilities]
2915A structure constructed around an oil tank to contain the oil in case the tank collapses. The volume or space inside the tank dike should be greater than the volume of the tank. A tank dike is also called a fire wall.
2916None
2917None
2918None
2919--
2920three component seismic data
29211.n. [Geophysics]
2922A 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.
2923accelerometer, geophone, hydrophone, multicomponent seismic data
2924None
2925None
2926--
2927tool joint
29281.n. [Drilling]
2929The enlarged and threaded ends of joints of drillpipe. These components are fabricated separately from the pipe body and welded onto the pipe at a manufacturing facility. The tool joints provide high-strength, high-pressure threaded connections that are sufficiently robust to survive the rigors of drilling and numerous cycles of tightening and loosening at threads. Tool joints are usually made of steel that has been heat treated to a higher strength than the steel of the tube body. The large-diameter section of the tool joints provides a low stress area where pipe tongs are used to grip the pipe. Hence, relatively small cuts caused by the pipe tongs do not significantly impair the strength or life of the joint of drillpipe.
2930back off, break out, dope, drillpipe, kelly spinner, keyseat, pipe dope, snubbing, spinning chain, stripping, tight hole, tongs
2931None
2932None
2933--
2934true vertical depth
29351.n. [Drilling]
2936The vertical distance from a point in the well (usually the current or final depth) to a point at the surface, usually the elevation of the rotary kelly bushing (RKB). This is one of two primary depth measurements used by the drillers, the other being measured depth. TVD is important in determining bottomhole pressures, which are caused in part by the hydrostatic head of fluid in the wellbore. For this calculation, measured depth is irrelevant and TVD must be used. For most other operations, the driller is interested in the length of the hole or how much pipe will fit into the hole. For those measurements, measured depth, not TVD, is used. While the drilling crew should be careful to designate which measurement they are referring to, if no designation is used, they are usually referring to measured depth. Note that measured depth, due to intentional or unintentional curves in the wellbore, is always longer than true vertical depth.
2937bottomhole pressure, hydrostatic head, hydrostatic pressure, kelly bushing, measured depth
2938None
2939TVD
2940--
2941tank table
29421.n. [Production Facilities]
2943A table that shows the tank capacity in barrels as a function of the liquid level inside the tank. A tank table is also called a tank capacity table or gauge table.
2944strap
2945None
2946None
2947--
2948three dimensional seismic data
29491.n. [Geophysics]
2950A 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.
2951acquisition, bin, crossline, in-line, migration, two-dimensional seismic data
2952None
2953None
2954--
2955tool string
29561.n. [Formation Evaluation]
2957The downhole hardware needed to make a log. Measurements-while-drilling(MWD)loggingtools, in some cases known aslogging while drilling(LWD) tools, are drill collars into which the necessary sensors and electronics have been built.Wirelinelogging tools are typically cylinders from 1.5 to 5 in. [3.8 to 12.7 cm] in diameter. Since the total length is more than can be conveniently handled in one piece, the logging tool is divided into different sections that are assembled at the wellsite. These sections consist of cartridges and sondes. Different measurements can be combined to make up a tool string. The total length of a tool string may range from 10 to 100 ft [3 to 30 m] or more. Flexible joints are added in long tool strings to ease passage in the borehole, and to allow different sections to be centralized or eccentralized. If the total length is very long, it is often preferable to make two or more logging runs with shorter tool strings.
2958bridle, cable, drill collar, head, log, torpedo
2959None
2960None
2961--
2962true vertical thickness
29631.n. [Geology]
2964The thickness of a bed or rock body measured vertically at a point. The values of true vertical thickness in an area can be plotted and contours drawn to create an isochore map.
2965attitude, bed, contour, isochore, isopach, stratigraphy, true stratigraphic thickness
2966None
2967None
2968--
2969tankage
29701.n. [Production Facilities]
2971The capacity of all the tanks in a field
2972None
2973None
2974None
2975--
2976three dimensional survey
29771.n. [Geophysics]
2978The 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.
2979acquisition, processing
2980None
2981None
2982--
2983toolpusher
29841.n. [Drilling]
2985The location supervisor for the drilling contractor. The toolpusher is usually a senior, experienced individual who has worked his way up through the ranks of the drilling crew positions. His job is largely administrative, including ensuring that the rig has sufficient materials, spare parts and skilled personnel to continue efficient operations. The toolpusher also serves as a trusted advisor to many personnel on the rigsite, including the operator's representative, the company man.
2986company man, driller
2987drilling foreman, pusher
2988None
2989--
2990trunnion
29911.n. [Production]
2992The part of a ball valve that holds the ball on a fixed vertical axis and about which the ball turns. The torque requirements of a trunnion-mounted ball valve are significantly less than for a floating ball design.
2993None
2994None
2995None
2996--
2997tanker
29981.n. [Production Facilities]
2999A ship designed to transport crude oil, liquefied petroleum gas (LPG), liquefied natural gas (LNG), synthetic natural gas (SNG) or refined products. Tankers with 100,000 deadweight tons of capacity or more are called supertankers (very large crude carriers or ultralarge crude carriers). A tanker is also called a tank ship.
3000ultralarge crude carrier, very large crude carrier
3001None
3002None
3003--
3004three phase separator
30051.n. [Production Facilities]
3006A vessel that separates the well fluids into gas and two types of liquids: oil and water. A three-phase separator can be horizontal, vertical or spherical. This type of separator is commonly called a free-water knockout because its main use is to remove any free water that can cause problems such as corrosion and formation of hydrates or tight emulsions, which are difficult to break.A free-water knockout is commonly called a three-phase separator because it can separate gas, oil and free water. The liquids that are discharged from the free-water knockout are further treated in vessels called treaters. Free-water knockout is abbreviated as FWKO.
3007horizontal separator, mist extractor, spherical separator, stage separation, vertical separator
3008None
3009None
3010--
3011top drive
30121.n. [Drilling]
3013A device that turns thedrillstring. It consists of one or more motors (electric or hydraulic) connected with appropriate gearing to a short section of pipe called a quill, that in turn may be screwed into a saver sub or the drillstring itself. The topdrive is suspended from the hook, so the rotary mechanism is free to travel up and down thederrick. This is radically different from the more conventional rotary table and kelly method of turning the drillstring because it enables drilling to be done with threejointstands instead of single joints of pipe. It also enables thedrillerto quickly engage the pumps or the rotary whiletripping pipe, which cannot be done easily with the kelly system. While not a panacea, modern topdrives are a major improvement todrilling rigtechnology and are a large contributor to the ability to drill more difficult extended-reach wellbores. In addition, the topdrive enables drillers to minimize bothfrequencyand cost per incident ofstuckpipe.
3014hook, kelly, make a connection, rotary table, stuck pipe
3015None
3016None
3017--
3018tube wave
30191.n. [Geophysics]
3020A Stoneley wave that occurs at the low frequencies of seismic data.
3021Stoneley wave, surface wave
3022None
3023None
3024--
3025tube wave
30262.n. [Geophysics]
3027An interface wave that occurs in cased wellbores when a Rayleigh wave encounters a wellbore and perturbs the fluid in the wellbore. The tube wave travels down the wellbore along the interface between the fluid in the wellbore and the wall of the wellbore. A tube wave suffers little energy loss and typically retains a very high amplitude which interferes with reflected arrivals occurring later in time on vertical seismic profile (VSP) data. Because the tube wave is coupled to the formation through which it is traveling, it can perturb the formation across open fractures intersecting the borehole. This squeezing effect can generate secondary tube waves which travel both up and down from the fracture location. Such events can be diagnostic of the presence of open fractures and their amplitude related qualitatively to the length and width, e.g., volume of the fluid-filled fracture space. This effect is generally seen only in shallow formations where the overburden pressure is lower.
3028coupling, Rayleigh wave, vertical seismic profile
3029None
3030None
3031--
3032tapered cutoff
30331.n. [Formation Evaluation]
3034In a nuclear magnetic resonance measurement, the use of a gradual rather than a sharp cutoff to distinguish between bound water and free water. A sharp cutoff at, for example T2 = 33 ms in sandstones, is normally used to distinguish free water (all T2s above 33 ms) from bound water (all T2s below 33ms). In a water-filled rock, in the fast diffusion limit, T2 is directly related to pore size. The distinction between bound and free water is based on the assumption that all free water resides in large pores, and all bound water in small pores. However, in rocks with large pores, a significant volume of bound water exists on the surface of the grains around a large pore. Being part of a large pore, it gives a long T2 and will be incorrectly counted as free water. One solution is the tapered cutoff, in which the bound water is the sum of all the T2 below a minimum, for example 5 ms, and is then a progressively smaller fraction of the volume at T2s up to a maximum, for example 500 ms. All signal above 500 ms represents free water. The form of the taper is usually empirical, but is based on some model of pore shape, such as a bundle of tubes.See Kleinberg RL and Boyd A: 'Tapered Cutoffs for Magnetic Resonance Bound Water Volume' paper SPE 38737, presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, October 5-8, 1997.
3035bound fluid, bound water, free water, irreducible water, nuclear magnetic resonance measurement
3036None
3037None
3038--
3039three component seismic data
30401.n. [Geophysics]
3041A 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.
3042accelerometer, geophone, hydrophone, multicomponent seismic data
3043None
30443C seismic data
3045--
3046top log interval
30471.n. [Formation Evaluation]
3048The top of the interval recorded on the log, or the shallowest point at which the log readings are valid. If the top of the log is at the casing shoe, the last valid reading of many logs will be a short distance below. However, it is common to give the depth of the casing shoe as the top log interval.
3049casing shoe, last reading
3050None
3051Antonyms:bottom log interval
3052--
3053tubing broach
30541.n. [Well Completions]
3055A downhole tool used to repair damaged or collapsed tubing. The tubing broach incorporates a cutter profile that is forced inside the tubing by jarring or hydraulic force to re-form the tubing wall by removing tubing wall material and forcing the tubing wall into place.
3056None
3057None
3058None
3059--
3060tapered string
30611.n. [Drilling]
3062A 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.
3063None
3064combination string
3065None
3066--
3067tapered string
30682.n. [Well Completions]
3069A string comprising tubing or components of varying size or dimension. A tapered production string may be configured with larger OD tubing joints in the upper wellbore area to optimize the hydraulic performance of the string. Although a tapered coiled tubing string will have the same tubing outside diameter throughout, the upper portion of the string may have a greater wall thickness to support the load of the string below.
3070None
3071None
3072None
3073--
3074tapered string
30753.n. [Well Workover and Intervention]
3076A tubing string or work string that is made up from tubulars of different outside diameters (OD). In production applications, this may be used to improve the flow and production characteristics of a well. In drilling applications, a tapered string may be used to enable a small hole section to be drilled without changing the entire string. In coiled tubing operations, tapered strings are configured with a constant OD but with varying wall thickness.
3077None
3078None
3079None
3080--
3081three dimensional seismic data
30821.n. [Geophysics]
3083A 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.
3084acquisition, bin, crossline, in-line, migration, two-dimensional seismic data
3085None
3086None
3087--
3088topdrive
30891.n. [Drilling]
3090A device that turns the drillstring. It consists of one or more motors (electric or hydraulic) connected with appropriate gearing to a short section of pipe called a quill, that in turn may be screwed into a saver sub or the drillstring itself. The topdrive is suspended from the hook, so the rotary mechanism is free to travel up and down the derrick. This is radically different from the more conventional rotary table and kelly method of turning the drillstring because it enables drilling to be done with three joint stands instead of single joints of pipe. It also enables the driller to quickly engage the pumps or the rotary while tripping pipe, which cannot be done easily with the kelly system. While not a panacea, modern topdrives are a major improvement to drilling rig technology and are a large contributor to the ability to drill more difficult extended-reach wellbores. In addition, the topdrive enables drillers to minimize both frequency and cost per incident of stuck pipe.
3091hook, kelly, make a connection, rig, rotary table, saver sub, stuck pipe
3092None
3093None
3094--
3095tubing conveyed perforating
30961.n. [Perforating]
3097The use of tubing,drillpipeor coiled tubing to convey perforating guns to the required depth. Initially, the technique was developed as a means for conveying the gun string on the production tubing, with the guns remaining in the well until they are removed during the firstworkover. The subsequent popularity of highly deviated and horizontal wells increased the requirement for tubing-conveyed perforating as the only means of gaining access to the perforating depth. The term is often abbreviated as TCP.
3098coiled tubing, perforating gun, production tubing
3099None
3100TCP
3101--
3102tar sand
31031.n. [Heavy Oil]
3104A sand body that contains heavy hydrocarbon residues such as tar or asphalt, or degraded oil that has lost its volatile components. Hydrocarbons can be liberated from tar sands by heating and other processes, but tar sands, such as the Athabasca tar sands of Canada, are not commonly commercial because of high costs of production.Among some workers in the field of heavy oil, this term is falling out of use, in favor of the term "oil sand."
3105asphalt, bitumen, hydrocarbon, oil sand
3106None
3107None
3108--
3109three dimensional survey
31101.n. [Geophysics]
3111The 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.
3112acquisition, processing
3113None
3114None
3115--
3116tornado chart
31171.n. [Formation Evaluation]
3118A 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 invasion and conductive invasion are plotted, the chart is called a butterfly chart. When only one is plotted, it is known as a tornado chart.
3119butterfly chart, conductive invasion, depth of investigation, diameter of invasion, flushed zone, resistive invasion, step profile, true resistivity
3120None
3121None
3122--
3123tubing displacement
31241.n. [Enhanced Oil Recovery]
3125A type of batch-treating technique used in corrosion control in which a batch of corrosion inhibitor is displaced through the tubing to the bottom of the well. The well is shut in for 2 to 15 hr and then put back on production.The tubing-displacement technique, also called a kiss squeeze, is used mainly in wells with packers and in gas-lift wells. The treatment could last from a week to several months depending on the specific corrosion inhibitor used.
3126batch treatment, corrosion inhibitor, gas lift, packer, standard batch
3127None
3128None
3129--
3130taylor bubbles
31311.n. [Production Logging]
3132In multiphase flow, large bubbles of the lighter phase that form by coalescence of small bubbles under certain conditions of fluid flow. The large bubbles occur during slug flow and plug flow. The term is named after G.I. Taylor.Reference:Davies RM and Taylor G: The Mechanics of Large Bubbles Rising Through Liquids and Through Liquids in Tubes, Proceedings of the Royal Society of London, Series A. 200 (February 22, 1950): 375-390.
3133fluid flow, multiphase flow, plug flow, slug flow
3134None
3135None
3136--
3137three phase separator
31381.n. [Production Facilities]
3139A vessel that separates the well fluids into gas and two types of liquids: oil and water. A three-phase separator can be horizontal, vertical or spherical. This type of separator is commonly called a free-water knockoutbecause its main use is to remove anyfree waterthat can cause problems such as corrosionandformationof hydrates or tight emulsions, which are difficult to break.A free-water knockout is commonly called a three-phase separator because it can separate gas, oil and free water. The liquids that are discharged from the free-water knockout are further treated in vessels called treaters. Free-water knockout is abbreviated as FWKO.
3140horizontal separator, mist extractor, spherical separator, stage separation, vertical separator
3141None
3142None
3143--
3144total depth
31451.n. [Drilling]
3146The depth of the bottom of the well. Usually, it is the depth where drilling has stopped.
3147None
3148None
3149TD
3150--
3151tubing grade
31521.n. [Well Completions]
3153A system of classifying the material specifications for steel alloys used in the manufacture of tubing.
3154None
3155None
3156None
3157--
3158tcp
31591.n. [Perforating]
3160Abbreviation for tubing-conveyed perforating, the use of tubing,drillpipeor coiled tubing to convey perforating guns to the required depth. Initially, the technique was developed as a means for conveying the gun string on the production tubing, with the guns remaining in the well until they are removed during the firstworkover. The subsequent popularity of highly deviated and horizontal wells increased the requirement for tubing-conveyed perforating as the only means of gaining access to the perforating depth.
3161coiled tubing, perforating gun, production tubing
3162None
3163tubing-conveyed perforating
3164--
3165throttling
31661.n. [Production]
3167The intentional restriction of flow by partially closing or opening a valve. A wide range of throttling is accomplished automatically in regulators and control valves.
3168None
3169None
3170None
3171--
3172total hardness test
31731.n. [Drilling Fluids]
3174A chemical analysis to measure the hardness ions in water-mud filtrates or in make-up water. Hardness is quantitatively determined by titration using standardized EDTA (versenate) reagent and ammonium hydroxide (weak) buffer, typically according to procedures of API. Results are reported as calcium ion in mg/L. The hardness ion Ca+2 can be analyzed alone by another EDTA titration method described by the API.
3175buffer, calcium test, EDTA, endpoint, filtrate, hard water, hardness ion, magnesium test, make-up water, titration
3176None
3177None
3178--
3179tubing hanger
31801.n. [Well Completions]
3181A device attached to the topmost tubing joint in the wellhead to support the tubing string. The tubing hanger typically is located in the tubing head, with both components incorporating a sealing system to ensure that the tubing conduit and annulus are hydraulically isolated.
3182tubing head, tubing joint
3183None
3184None
3185--
3186td
31871.n. [Drilling]
3188Abbreviation for total depth. The depth of the bottom of the well. Usually, it is the depth where drilling has stopped.
3189None
3190None
3191total depth
3192--
3193through flowline tfl
31941.adj. [Well Completions]
3195Pertaining to treatments performed on subsea wells where the fluids and associated pump-down equipment, such as plugs or darts, are pumped through theflowlinenormally used for production fluids.
3196dart, subsea well
3197None
3198None
3199--
3200total solids
32011.n. [Drilling Fluids]
3202Also known as retort solids, the volume percent (or fraction) of a mud that is not captured in the receiver when performing the water, oil and solids test as prescribed by API, as given in the equation below.Retort solids thus include suspended solids, dissolved solids (salts), charred organic materials and volatile materials that do not condense. For calculations, retort solids are normally assumed to be only suspended and dissolved solids, as in the equation below.Volume percent suspended solids (weighting material plus drill solids) is of particular interest to mud engineers. To calculate that percentage, the volume increase caused by the dissolved salts is determined from filtrate analyses of chloride and calcium ions. For oil muds, the calculations are more complicated.
3203calcium test, chloride test, dissolved solids, drill solids, high-gravity solids, material-balance equation, retort, suspended solids, water, oil and solids test
3204None
3205None
3206--
3207tubing joint
32081.n. [Well Completions]
3209A single length of the pipe that is assembled to provide a conduit through which the oil or gas will be produced from a wellbore. Tubing joints are generally around 30 ft [9 m] long with a thread connection on each end. The specification of the tubing material, geometry of the tubing, and design of the connection thread are selected to suit the reservoir fluid and wellbore conditions.
3210None
3211None
3212None
3213--
3214te
32151.n. [Geophysics]
3216A mode of the electromagnetic field that involves only one component of the electric field and the two components of the magnetic field perpendicular to it; e.g., the x-component of the electric field and y- and z-components of the magnetic field. The TE mode is useful in describing 2D models in which the electric field is perpendicular to the 2D plane of the model. For this case, Maxwell's equations can be reduced to a single scalar equation for the electric field component, which simplifies calculations tremendously. There is an analogous mode for the magnetic field called the TM mode. A general EM field in a region without sources can be expressed as a sum of TE and TM modes.
3217None
3218None
3219transverse electric mode
3220--
3221through tubing gun
32221.n. [Perforating]
3223A perforating gun assembly designed to run through the restricted clearance of production tubing, then operate effectively within the larger diameter of thecasingorlinerbelow. A range of small-diameter guns has been developed for this purpose, although small-diameter casing guns also may be used when larger production tubing sizes permit.
3224casing gun, perforating gun, production tubing
3225None
3226None
3227--
3228tour
32291.n. [Drilling]
3230A work shift of a drilling crew. Drilling operations usually occur around the clock because of the cost to rent a rig. 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.)
3231daylight tour, drilling crew, evening tour, graveyard tour, morning tour
3232None
3233None
3234--
3235tubing puncher
32361.n. [Perforating, Well Completions]
3237A special perforating gun, or charge, that is designed for limited penetration to allow an inner tubing or casing string to be perforated without damaging a surrounding outer string. These guns often are used in remedial or workover operations in which downhole communication devices, such as sliding sleeves, cannot be opened to allow circulation of well-kill fluids.
3238casing string, perforating gun, sliding sleeve
3239None
3240None
3241--
3242technical evaluation agreement
32431.n. [Oil and Gas Business]
3244An agreement between a host country and operator to allow the operator to evaluate geological, geophysical, engineering and transportation issues involving a concession. Also known as a TEA.
3245concession, operator
3246None
3247None
3248--
3249through conduit
32501.n. [Production]
3251An expression characterizing valves when in the open position, wherein the bore presents a smooth uninterrupted interior surface across seat rings and through the valve port, thus affording minimum pressure drop. There are no cavities or large gaps in the bore between seat rings and body closures or between seat rings, balls and gates. Consequently, there are no areas where debris can accumulate and impede pipeline cleaning equipment or restrict the valve's motion.
3252None
3253None
3254None
3255--
3256tracer ejector measurement
32571.n. [Production Logging]
3258Another term for velocity-shot measurement, a method of producing a radioactive-tracerlog, in which aslugof radioactive material is injected into the flow streamof aproductionorinjection wellfrom one section of aloggingtool and observed as it passes one or more gamma ray detectors in another section. The slug, or shot, causes apeakin the gamma ray reading as it passes adetector. The flowvelocityis determined from the difference in the time of arrival of the slug at the two detectors, or between ejector and detector. This technique has been applied for many years using radioactive tracers such as iodine. Water-soluble tracers are the most common, but oil- and gas-soluble tracers are also used.Velocity-shot measurements are recorded with the tool stationary. They are more accurate than flowmeters at low flow rates, below approximately 100 B/D [16m3/d]. They are not usuallyrunin production wells because of problems of tracer disposal. Inmultiphaseflow, the tracer most often travels with thecontinuous phase, thereby giving a type ofphase-velocity log.
3259interval method, production log, timed-slug analysis, tracer measurement, tracer-loss measurement
3260velocity-shot measurement
3261None
3262--
3263tubing seal assembly
32641.n. [Well Completions]
3265A system of seals arranged on the component that engages in asealboreto isolate theproduction-tubing conduit from theannulus. The seal assembly is typically longer than the sealbore to enable some movement of the components while maintaining an efficient seal.
3266production tubing
3267None
3268None
3269--
3270tectonics
32711.n. [Geology]
3272Also known as plate tectonics, the unifying geologic theory developed to explain observations that interactions of the brittle plates of the lithosphere with each other and with the softer underlying asthenosphere result in large-scale changes in the Earth. The theory of plate tectonics initially stemmed from observations of the shapes of the continents, particularly South America and Africa, which fit together like pieces in a jigsaw puzzle and have similar rocks and fossils despite being separated by a modern ocean. As lithospheric plates heat up or cool down depending on their position, or their tectonic environment, relative to each other and to warmer areas deeper within the Earth, they become relatively more or less dense than the asthenosphere and thus tend to rise as molten magma or sink in cold, brittle slabs or slide past each other. Mountain belts can form during plate collisions or an orogeny; diverging plates or rifts can create new midoceanic ridges; plates that slide past one another create transform fault zones (such as the San Andreas fault); and zones of subduction occur where one lithospheric plate moves beneath another. Plate tectonic theory can explain such phenomena as earthquakes, volcanic or other igneous activity, midoceanic ridges and the relative youth of the oceanic crust, and the formation of sedimentary basins on the basis of their relationships to lithospheric plate boundaries. Convection of the mantle is postulated to be the driving mechanism for the movement of lithospheric plates. Measurements of the continents using the Global Positioning System confirm the relative motions of plates. Age determinations of the oceanic crust confirm that such crust is much younger than that of the continents and has been recycled by the process of subduction and regenerated at midoceanic ridges.
3273active margin, aulacogen, basin, core, craton, earthquake, eustasy, Global Positioning System, isostasy, midoceanic ridge, normal fault, orogeny, passive margin, preservation, rift, rock, sedimentary basin, sequence stratigraphy, transform fault, Wadati-Benioff zone
3274plate tectonics
3275None
3276--
3277through flowline tfl
32781.adj. [Well Completions]
3279Pertaining to treatments performed on subsea wells where the fluids and associated pump-down equipment, such as plugs or darts, are pumped through the flowline normally used for production fluids.
3280dart, subsea well
3281None
3282None
3283--
3284tracer ejector measurement
32851.n. [Production Logging]
3286Another term for velocity-shot measurement, a method of producing a radioactive-tracerlog, in which aslugof radioactive material is injected into the flow streamof aproductionorinjection wellfrom one section of aloggingtool and observed as it passes one or more gamma ray detectors in another section. The slug, or shot, causes apeakin the gamma ray reading as it passes adetector. The flowvelocityis determined from the difference in the time of arrival of the slug at the two detectors, or between ejector and detector. This technique has been applied for many years using radioactive tracers such as iodine. Water-soluble tracers are the most common, but oil- and gas-soluble tracers are also used.Velocity-shot measurements are recorded with the tool stationary. They are more accurate than flowmeters at low flow rates, below approximately 100 B/D [16m3/d]. They are not usuallyrunin production wells because of problems of tracer disposal. Inmultiphaseflow, the tracer most often travels with thecontinuous phase, thereby giving a type ofphase-velocity log.
3287interval method, production log, timed-slug analysis, tracer measurement, tracer-loss measurement
3288velocity-shot measurement
3289None
3290--
3291tubing thread
32921.n. [Well Completions]
3293The threaded connection used to assemble the tubing string from individual tubing joints. Various tubing thread types have evolved to suit the wellbore conditions and functions required of the tubing string, both during installation and while the well is in production.
3294None
3295None
3296None
3297--
3298telemetry
32991.n. [Formation Evaluation]
3300A system for converting the measurements recorded by a wireline or measurements-while-drilling (MWD) tool into a suitable form for transmission to the surface. In the case of wireline logging, the measurements are converted into electronic pulses or analog signals that are sent up the cable. In the case of MWD, they are usually converted into an amplitude or frequency-modulated pattern of mud pulses. Some MWD tools use wirelines run inside the drillpipe. Others use wireless telemetry, in which signals are sent as electromagnetic waves through the Earth. Wireless telemetry is also used downhole to send signals from one part of an MWD tool to another.
3301cartridge, mud pulse telemetry, sonde
3302None
3303None
3304--
3305through tubing
33061.adj. [Well Completions]
3307Pertaining to any reservoir or wellbore treatment performed through the tubing string. Through-tubing treatments are generally associated with live-well operations, thereby causing minimal interruption to production and eliminating the need to kill the well.
3308None
3309None
3310None
3311--
3312through tubing
33132.adj. [Well Workover and Intervention]
3314Pertaining to a range of products, services and techniques designed to be run through, or conducted within, the production tubing of an oil or gas well. The term implies an ability to operate within restricted-diameter tubulars and is often associated with live-well intervention since the tubing is in place.
3315production tubing
3316None
3317None
3318--
3319track
33201.n. [Formation Evaluation]
3321A vertical section of a log presentation over which one particular set of data is displayed. The track divides the presentation into different sections, each with a certain set of log curves or other data, such as depth numbers. The section is vertical in the sense that it is along the depth or time axis of the log. The curves are usually blanked off when they run outside their allotted track. Tracks are typically numbered from left to right across the page (when viewed with depth or time increasing towards the bottom of the page).
3322heading, insert, repeat section, tail
3323None
3324None
3325--
3326tubing conveyed perforating
33271.n. [Perforating]
3328The use of tubing, drillpipe or coiled tubing to convey perforating guns to the required depth. Initially, the technique was developed as a means for conveying the gun string on the production tubing, with the guns remaining in the well until they are removed during the first workover. The subsequent popularity of highly deviated and horizontal wells increased the requirement for tubing-conveyed perforating as the only means of gaining access to the perforating depth. The term is often abbreviated as TCP.
3329coiled tubing, perforating gun, production tubing
3330None
3331TCP
3332--
3333telluric current
33341.n. [Geophysics]
3335A low-frequency electrical current that occurs naturally over large areas at or near the surface of the Earth. Telluric currents are induced by changes in Earth's magnetic field which are usually caused by interactions between the solar wind and the ionosphere (part of the upper atmosphere).
3336telluric-current method
3337None
3338None
3339--
3340through tubing gun
33411.n. [Perforating]
3342A perforating gun assembly designed to run through the restricted clearance of production tubing, then operate effectively within the larger diameter of the casing or liner below. A range of small-diameter guns has been developed for this purpose, although small-diameter casing guns also may be used when larger production tubing sizes permit.
3343casing gun, perforating gun, production tubing
3344None
3345None
3346--
3347transgression
33481.n. [Geology]
3349The migration of shoreline out of a basin and onto land during retrogradation. A transgression can result in sediments characteristic of shallow water being overlain by deeper water sediments.
3350condensed section, eustasy, onlap, regression, retrogradation, sequence stratigraphy, systems tract
3351None
3352Antonyms:regression
3353--
3354tubingless completion
33551.n. [Well Completions]
3356A completion design in which the reservoir fluids are produced through small-diameter casing. The absence of a separate tubing string significantly limits the operating and contingency options available for the well.
3357None
3358None
3359None
3360--
3361telluric current method
33621.n. [Geophysics]
3363An electromagnetic method in which naturally occurring, low-frequency electric currents (telluric currents), are measured at a base station and compared with values measured at other stations. The normalized measurements of telluric current provide information about the direction of current flow and the conductance (conductivity times thickness) of sediments in the surveyed area. Extremely low-frequency telluric currents (with periods of days or months) provide information about conductivity in the deep interior of the Earth.
3364base station, survey, telluric current
3365None
3366None
3367--
3368thrust fault
33691.n. [Geology]
3370A type of reverse fault in which the fault plane has a very shallow dip, typically much less than 45o. The hanging wall fault block moves up the fault surface relative to the footwall. In cases of considerable lateral movement, the fault is described as an overthrust fault. Thrust faults can occur in areas of compression of the Earth's crust.
3371crust, decollement, dip, fault, orogeny, overthrust, reverse fault
3372None
3373None
3374--
3375transgressive
33761.adj. [Geology]
3377Pertaining to transgression, themigrationof shoreline out of abasinand onto land during retrogradation. A transgression can result in sediments characteristic of shallow water being overlain by deeper water sediments.
3378condensed section, eustasy, retrogradation, sequence stratigraphy, systems tract
3379onlap
3380None
3381--
3382turbidity current
33831.n. [Geology]
3384An influx of rapidly moving, sediment-laden water down a slope into a larger body of water; also called a density current because the suspended sediment results in the current having a higher density than the clearer water into which it flows. Such currents can occur in lakes and oceans, in some cases as by-products of earthquakes or mass movements such as slumps. The sedimentary deposits that form as the current loses energy are called turbidites and can be preserved as Bouma sequences. Turbidity currents are characteristic of trench slopes of convergent plate margins and continental slopes of passive margins.
3385Bouma sequence, channel, convergence, lamination, passive margin, sediment, turbidite
3386density current
3387None
3388--
3389telluric current method
33901.n. [Geophysics]
3391An electromagnetic method in which naturally occurring, low-frequency electric currents (telluric currents), are measured at a base station and compared with values measured at other stations. The normalized measurements of telluric current provide information about the direction of current flow and the conductance (conductivity times thickness) of sediments in the surveyed area. Extremely low-frequency telluric currents (with periods of days or months) provide information about conductivity in the deep interior of the Earth.
3392base station, survey, telluric current
3393None
3394None
3395--
3396ti
33971.n. [Geophysics]
3398Abbreviation for transverse isotropy. Transverse isotropy, polar anisotropy, axial anisotropy and cross anisotropy are synonymous terms referring to the particular directional character of materials in which properties have the same values in all directions parallel to planes of isotropy and different values perpendicular to or crossing the planes of isotropy; this perpendicular direction is an axis of rotational symmetry.
3399axis of rotational symmetry, vertical transverse isotropy, horizontal transverse isotropy
3400None
3401transverse isotropy
3402--
3403transgressive surface
34041.n. [Reservoir Characterization]
3405A marine flooding surface separating the underlying lowstand systems tract from the overlying transgressive systems tract. Typically, this is the first major flooding surface following the lowstand systems tract.
3406flooding surface, maximum flooding surface, sequence stratigraphy
3407None
3408None
3409--
3410turbulent flow
34111.n. [Well Completions]
3412A fluid-flow regime characterized by swirling or chaotic motion as the fluid moves along the pipe or conduit. The linear velocity of the fluid particles is similar regardless of position in the conduit, although particles close to the conduit walls have a lower velocity. This characteristic makes turbulent flow an efficient flow regime for the pickup and transport of solids. However, the potential for erosion may be significant, especially with abrasive fluids and a tortuous flow path.
3413None
3414None
3415None
3416--
3417turbulent flow
34182.n. [Production Logging]
3419A type of flow for single-phase fluids in which the velocity at any point may vary in both direction and magnitude with time. Turbulent flow is characterized by random, irregular, locally circular currents, or vortices. It occurs in straight pipes when the Reynolds number is above a critical value, corresponding to a higher production rate. Below this value, the flow is laminar. For turbulent flow in straight pipes, the velocity increases from zero at the wall of the pipe, passes through a thin layer of laminar flow to reach a near constant value over most of the pipe.
3420flow regime, laminar flow
3421None
3422None
3423--
3424turbulent flow
34253.n. [Drilling Fluids]
3426A type of fluid flow characterized by swirling or chaotic motion as the fluid moves along the flow path. This is a preferred flow regime for mud removal during primary cementing because it is perceived to result in better removal of mud, especially of mud at the formation wall.
3427None
3428None
3429None
3430--
3431turbulent flow
34324.n. [Production]
3433The random flow of a fluid in which the velocity at a certain point in the fluid varies irregularly. It occurs at a high Reynolds number, a dimensionless term related to fluid viscosity and flow rates.
3434None
3435None
3436None
3437--
3438temperature gradient
34391.n. [Geology, Drilling Fluids]
3440Also known as geothermal gradient, the rate of increase in temperature per unit depth in the Earth. Although the geothermal gradient varies from place to place, it averages 25 to 30°C/km [15°F/1000 ft].Temperature gradients sometimes increase dramatically aroundvolcanicareas. It is particularly important for drilling fluids engineers to know the geothermal gradient in an area when they are designing a deep well. The downhole temperature can be calculated by adding the surface temperature to the product of the depth and the geothermal gradient.
3441high-pressure, high-temperature filtration test, mud engineer
3442geothermal gradient, thermal gradient
3443None
3444--
3445tick mark
34461.n. [Formation Evaluation]
3447In logging while drilling, a mark associated with each measurement indicating when a sample was taken. It is usually presented as a short bar in the depth track. Widely spaced tick marks indicate a low sampling rate. In wireline logging, a tick mark indicates the cumulative volume of some quantity, such as hole volume or traveltime. The term is sometimes spelled tic mark.
3448logging while drilling
3449None
3450None
3451--
3452transient pressure response
34531.n. [Well Testing]
3454The pressure response resulting from changes in a well's production rate. This includes drawdown, in which the pressure falls in response to the production of fluids; buildups, in which the pressure rises after a well is shut in; and falloffs, in which the pressure falls after an injection well is shut in.
3455injection well, pressure buildup, pressure falloff
3456None
3457None
3458--
3459turnkey
34601.adj. [Drilling]
3461A type of financing arrangement for the drilling of a wellbore that places considerable risk and potential reward on the drilling contractor. Under such an arrangement, the drilling contractor assumes full responsibility for the well to some predetermined milestone such as the successful running of logs at the end of the well, the successful cementing of casing in the well or even the completion of the well. Until this milestone is reached, the operator owes nothing to the contractor. The contractor bears all risk of trouble in the well, and in extreme cases, may have to abandon the well entirely and start over. In return for assuming such risk, the price of the well is usually a little higher than the well would cost if relatively trouble free. Therefore, if the contractor succeeds in drilling a trouble-free well, the fee added as contingency becomes profit. Some operators, however, have been required by regulatory agencies to remedy problem wells, such as blowouts, if the turnkey contractor does not.
3462blowout, casing, cementing, completion, contract depth, drilling contractor
3463None
3464None
3465--
3466temperature stability
34671.n. [Drilling Fluids]
3468The characteristic of a drilling fluid or a mud product pertaining to its response to prolonged heating, usually in a controlled mud composition in a rolling- or static-aging test.
3469hydrolysis, mud-aging cell, pilot test, rolling-aging test, static-aging test
3470None
3471None
3472--
3473tie
34741.n. [Geophysics]
3475A comparison, or the location of a comparison, of data. Properly processed and interpreted seismic lines can show good ties, or correlations, at intersection points.
3476correlation, interpretation, mis-tie
3477None
3478None
3479--
3480tie
34812.vb. [Geophysics]
3482To correlate data in order to formulate or verify an interpretation or to demonstrate the relationship between data sets. Long, regional-scale 2D seismic lines are commonly tied to 3D surveys that cover a limited area, and 3D surveys of different vintages are tied to each other. Well logs are tied into seismic data routinely to determine the relationship between lithologic boundaries in the logs and seismic reflections. Properly tying all available data, including seismic data, well logs, check-shot surveys, synthetic seismograms and vertical seismic profiles, can reduce or, if there are sufficient data, eliminate ambiguity in interpretations.
3483check-shot survey, correlation, lithology, reflector, synthetic seismogram, three-dimensional survey, two-dimensional seismic data, vertical seismic profile
3484None
3485None
3486--
3487transient pressure testing
34881.n. [Well Testing]
3489The pressure measurements recorded as a function of time, usually in the wellbore near the productive interval, after the flow rate of the well is changed. These form the basis for transient well-test analysis, and are primarily used for determining reservoir-rock properties and producing-formation limits.
3490None
3491None
3492None
3493--
3494tvd
34951.n. [Drilling]
3496The vertical distance from a point in the well (usually the current or final depth) to a point at the surface, usually the elevation of the rotary kelly bushing (RKB). This is one of two primary depth measurements used by the drillers, the other being measured depth. TVD is important in determining bottomhole pressures, which are caused in part by the hydrostatic head of fluid in the wellbore. For this calculation, measured depth is irrelevant and TVD must be used. For most other operations, the driller is interested in the length of the hole or how much pipe will fit into the hole. For those measurements, measured depth, not TVD, is used. While the drilling crew should be careful to designate which measurement they are referring to, if no designation is used, they are usually referring to measured depth. Note that measured depth, due to intentional or unintentional curves in the wellbore, is always longer than true vertical depth.
3497None
3498None
3499true vertical depth
3500--
3501teor
35021.n. [Heavy Oil, Enhanced Oil Recovery]
3503Abbreviation for thermal enhanced oil recovery, also known as thermal recovery, a general term for injection processes that introduce heat into areservoir. Thermal recovery is used to produce viscous, thick oils withAPIgravities less than 20. These oils cannot flow unless they are heated and theirviscosityis reduced enough to allow flow toward producing wells.During thermal recovery,crude oilundergoes physical and chemical changes because of the effects of the heat supplied. Physical properties such as viscosity,specific gravityandinterfacial tensionare altered. The chemical changes involve different reactions such ascracking, which is the destruction of carbon-carbon bonds to generate lower molecular weight compounds, and dehydrogenation, which is the rupture of carbon-hydrogen bonds.Thermal recovery is a major branch ofenhanced oil recoveryprocesses and can be subdivided in two types: hot fluid injection such as steam injection (steamfloodorcyclic steam injection) andhot waterfloodingandin-situ combustionprocesses.
3504API gravity, chemical flooding
3505miscible displacement
3506thermal recovery
3507--
3508tie back liner
35091.n. [Well Completions]
3510A section oflinerthat is run from aliner hangerback to thewellheadafter the initial liner and hanger system have been installed and cemented. Atie-back liner may be required to provide the necessarypressurecapacity during a flow-test period or for special treatments, and is typically not cemented in place. In some cases, a tie-back liner will be installed as a remedial treatment when the integrity of theintermediatecasingstring is in doubt.
3511casing string
3512None
3513None
3514--
3515transit time
35161.n. [Geophysics]
3517The duration of time for a P-wave to travel one foot, typically displayed on an acoustic log. The unit of microseconds per foot (or meter) is called the slowness, which is the inverse of velocity. Transit time is measured in microseconds per foot (μs/ft) or in microseconds per meter (μs/m).
3518acoustic, cycle skip, delta t, drift, P-wave
3519interval transit time
3520None
3521--
3522two dimensional seismic data
35231.n. [Geophysics]
3524A vertical section of seismic data consisting of numerous adjacent traces acquired sequentially.
3525trace
3526None
3527None
3528--
3529two dimensional seismic data
35302.n. [Geophysics]
3531A group of 2D seismic lines acquired individually, as opposed to the multiple closely spaced lines acquired together that constitute 3D seismic data.
3532acquisition, three-dimensional seismic data, trace
3533None
3534None
3535--
3536tertiary recovery
35371.n. [Enhanced Oil Recovery]
3538Traditionally, the third stage of hydrocarbon production, comprising recovery methods that follow waterflooding or pressure maintenance. The principal tertiary recovery techniques used are thermal methods, gas injection and chemical flooding. The term is sometimes used as a synonym for enhanced oil recovery (EOR), but because EOR methods today may be applied at any stage of reservoir development, the term tertiary recovery is less commonly used than in the past.
3539API gravity, chemical flooding, enhanced oil recovery, EOR, fluid flow, formation pressure, in-situ combustion, miscible displacement, primary recovery, residual oil, secondary recovery, steamflood, thermal recovery
3540None
3541None
3542--
3543tie back packer
35441.n. [Well Completions]
3545A specially designedpackerassembly used in conjunction with atie-backliner. The tie-back packer can be integral to the original liner hanger, or if the tie-back is a remedial treatment, it can be a separate component set above the liner hanger.
3546liner hanger, tie-back liner
3547None
3548None
3549--
3550transition flow
35511.n. [Well Completions]
3552A multiphase flow regime in near-vertical pipes in which large, irregular slugs of gas move up the center of the pipe, usually carrying droplets of oil or water with them. Most of the remaining oil or water flows up along the pipe walls.The flow is relatively chaotic, producing a frothy mixture. Unlike slug flow, neither phase is continuous. The gas slugs are relatively unstable, and take on large, elongated shapes. Also known aschurn 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 into annular flow.
3553annular flow, bubble flow, flow regime, flow structure, mist flow, multiphase fluid flow, slug, slug flow
3554churn flow
3555None
3556--
3557two dimensional survey
35581.n. [Geophysics]
3559Seismic 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.
3560acquisition, correlate, correlation, fault, fold, strike
3561None
3562None
3563--
3564test separator
35651.n. [Production Facilities]
3566A vessel used to separate and meter relatively small quantities of oil and gas. Test separators can be two-phase or three-phase, or horizontal, vertical or spherical. They can also be permanent or portable.Test separators sometimes are equipped with different meters to determine oil, water and gas rates, which are important to diagnose well problems, evaluate production performance of individual wells and manage reserves properly.Test separators can also be called well testers or a well checkers.
3567None
3568None
3569None
3570--
3571tie back liner
35721.n. [Well Completions]
3573A section of liner that is run from a liner hanger back to the wellhead after the initial liner and hanger system have been installed and cemented. A tie-back liner may be required to provide the necessary pressure capacity during a flow-test period or for special treatments, and is typically not cemented in place. In some cases, a tie-back liner will be installed as a remedial treatment when the integrity of the <a href="Display.cfm?Term=intermediate%20casing%20string">intermediate <a href="Display.cfm?Term=casing">casing string is in doubt.
3574casing string
3575None
3576None
3577--
3578transition zone
35791.n. [Geophysics]
3580An area in which water is too shallow for acquisition of marine seismic data with towed streamers, such as near the shoreline, marshes and lagoons. In some cases, source explosives can be rammed into the unconsolidated sediments of transition zone environments rather than drilling more costly shot holes. Likewise, hydrophones can be placed by ramming to couple the receiver to the Earth better and to save time and money during survey acquisition.
3581acquisition, coupling
3582None
3583None
3584--
3585transition zone
35862.n. [Formation Evaluation]
3587With reference to invasion, the volume between the flushed zone and the undisturbed zone in which the mud filtrate has only partially displaced the moveable formation fluids. One common model of invasion assumes a smooth transition in resistivity and other formation properties from the flushed to the undisturbed zone. Based on this assumption, the inner and outer diameters of invasion can be determined from array resistivity logs. Another common invasion model, which does not assume a smooth transition, is the annulus.
3588step profile
3589None
3590None
3591--
3592two pass method
35931.n. [Production Logging]
3594A technique for interpreting the results from a spinnerflowmeterusing twologgingruns over the zone of interest, one up and one down. If the two passes arerunat the samecablespeed, they will overlay below the perforations, where there is no flow. If they were not run at the same speed, the curves are shifted to overlay. Elsewhere, the separation between the curves gives the relative contribution of each zone.Viscositychanges should have a small effect, since they will have the same influence on both passes.The technique is applicable when the flow issingle-phase, or elsemultiphasewith a sufficiently homogeneous-flow regime, such as withemulsionordispersed bubble flow.
3595effective velocity, flow profile, multipass method, single-pass method, spinner flowmeter, spinner reversal, threshold velocity, velocity-correction factor
3596None
3597None
3598--
3599tetrahedral layer
36001.n. [Drilling Fluids]
3601One of the layers that constitute the atomic structure of the clay group of layeredsilicateminerals. The structure of these minerals can consist of two, three or four layers.The tetrahedral layer is a plane of silicon dioxide tetrahedra (silicon at the center and oxygen at all four corners of the tetrahedron). Another 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.
3602anion, clay, colloidal solids, hygroscopic, ion exchange, kaolinite, montmorillonite, octahedral layer, polar compound, silica layer
3603None
3604None
3605--
3606tie back packer
36071.n. [Well Completions]
3608A specially designed packer assembly used in conjunction with a tie-back liner. The tie-back packer can be integral to the original liner hanger, or if the tie-back is a remedial treatment, it can be a separate component set above the liner hanger.
3609liner hanger, tie-back liner
3610None
3611None
3612--
3613transverse electric mode
36141.n. [Geophysics]
3615A mode of the electromagnetic field that involves only one component of the electric field and the two components of the magnetic field perpendicular to it; e.g., the x-component of the electric field and y- and z-components of the magnetic field. The TE mode is useful in describing 2D models in which the electric field is perpendicular to the 2D plane of the model. For this case, Maxwell's equations can be reduced to a single scalar equation for the electric field component, which simplifies calculations tremendously. There is an analogous mode for the magnetic field called the TM mode. A general EM field in a region without sources can be expressed as a sum of TE and TM modes.
3616electromagnetic method, transverse magnetic mode, wave
3617None
3618TE
3619--
3620two phase separator
36211.n. [Production Facilities]
3622A vessel that separates the well fluids into gas and total liquid. A two-phase separator can be horizontal, vertical or spherical. The liquid (oil, emulsion) leaves the vessel at the bottom through a level-control or dump valve. The gas leaves the vessel at the top, passing through a mist extractor to remove the small liquid droplets in the gas.
3623horizontal separator, mist extractor, spherical separator, stage separation, vertical separator
3624None
3625oil and gas separator, two-phase separator
3626--
3627texas deck
36281.n. [Drilling]
3629On an offshore jackup drilling rig, the deck below the rotary table and rig floor where workers can access the BOP stack. This platform surrounds the base of the BOP stack and is suspended from the cantilever (where the rig floor is located) by adjustable cables. It is accessed from the main deck of the jackup barge by a semipermanent stairwell. The Texas deck is used primarily for installing the wellhead and nippling the BOP stack up and down.
3630BOP stack, jackup rig, rig floor, rotary table, wellhead
3631None
3632None
3633--
3634tie back string
36351.n. [Well Completions]
3636Another term for tie-back liner, a section oflinerthat is run from aliner hangerback to thewellheadafter the initial liner and hanger system have been installed and cemented. Atie-back liner may be required to provide the necessarypressurecapacity during a flow-test period or for special treatments, and is typically not cemented in place. In some cases, a tie-back liner will be installed as a remedial treatment when the integrity of theintermediatecasingstring is in doubt.
3637casing string
3638tie-back liner
3639None
3640--
3641transverse isotropy
36421.n. [Geophysics]
3643Transverse isotropy, polar anisotropy, axial anisotropy and cross anisotropy are synonymous terms referring to the particular directional character of materials in which properties have the same values in all directions parallel to planes of isotropy and different values perpendicular to or crossing the planes of isotropy; this perpendicular direction is an axis of rotational symmetry.
3644axis of rotational symmetry, vertical transverse isotropy, horizontal transverse isotropy
3645None
3646TI
3647--
3648two dimensional seismic data
36491.n. [Geophysics]
3650A vertical section of seismic data consisting of numerous adjacent traces acquired sequentially.
3651trace
3652None
3653None
3654--
3655two dimensional seismic data
36562.n. [Geophysics]
3657A group of 2D seismic lines acquired individually, as opposed to the multiple closely spaced lines acquired together that constitute 3D seismic data.
3658acquisition, three-dimensional seismic data, trace
3659None
3660None
3661--
3662tg
36631.n. [Drilling]
3664Gas entrained in the drilling fluid during a pipe trip, which typically results in a significant increase in gas that is circulated to surface. This increase arises from a combination of two factors: lack of circulation when the mud pumps are turned off, and swabbing effects caused by pulling the drillstring to surface. These effects may be seen following a short trip into casing or a full trip to surface.
3665None
3666None
3667trip gas
3668--
3669tight
36701.adj. [Geology, Shale Gas]
3671Describing a relatively impermeable reservoir rock from which hydrocarbon production is difficult. Reservoirs can be tight because of smaller grains or matrix between larger grains, or they might be tight because they consist predominantly of silt- or clay-sized grains, as is the case for shale reservoirs.Stimulation of tight formations can result in increased production from formations that previously would have been abandoned or produced uneconomically.
3672formation, impermeable, reservoir
3673None
3674None
3675--
3676tight
36772.adj. [Geology]
3678Secrecy or confidentiality of information. Operators typically try to prevent disclosure of results from exploration wells and will hold any such information "tight". A tight hole is a well whose status and data are not widely disseminated by the operator.
3679scout
3680None
3681tight hole
3682--
3683transverse relaxation
36841.n. [Formation Evaluation]
3685The loss of coherent energy by protons in a rock while precessing about a static magnetic field during a nuclear magnetic resonance measurement. The loss of coherent energy, or relaxation, due to the <a href="Display.cfm?Term=free%20induction%20decay">free <a href="Display.cfm?Term=induction">induction decay is corrected by the CPMG pulse sequence. This leaves three mechanisms for relaxation: surface relaxation, bulk relaxation and diffusion relaxation, all of which depend on formation properties. Transverse relaxation is characterized by an exponential decay of time constant T2.
3686free-induction decay, longitudinal relaxation, nuclear magnetic resonance measurement, relaxation time, T1
3687None
3688None
3689--
3690two dimensional survey
36911.n. [Geophysics]
3692Seismic 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.
3693acquisition, correlate, correlation, fault, fold, strike
3694None
3695None
3696--
3697thermal capture
36981.n. [Formation Evaluation]
3699A neutron interaction in which the neutron is absorbed by the target nucleus, producing an isotope in an excited state. The activated isotope de-excites instantly through the emission of characteristic gamma rays. Thermal capture, also called neutron capture, usually occurs at low thermal energies at which the neutrons have about the same energy as the surrounding matter, typically below 0.4 eV (0.025 eV at room temperature). Some elements are better thermal absorbers than others. Neutron capture is an important principle behind the pulsed neutron capture log, theelemental capture spectroscopylog, the pulsed neutron spectroscopy logand thethermal neutron porosity measurement.
3700chemical neutron source, fast-neutron reaction, inelastic neutron scattering, neutron generator, neutron interactions
3701neutron capture
3702None
3703--
3704tight emulsion
37051.n. [Production Facilities]
3706An emulsion with small and closely distributed droplets. A tight emulsion can be difficult to break.
3707None
3708None
3709Antonyms:loose emulsion
3710--
3711trapped oil
37121.n. [Enhanced Oil Recovery]
3713Oil in pore spaces that cannot be moved because of capillary forces. Typical trapped or residual oil saturation is in the range of 10% to 50% of the pore space, and it is higher in tighter formations where the pore spaces are small. The amount of trapped oil is a function of the displacement method and conditions, making this oil a target for enhanced oil recovery (EOR) processes. EOR methods introduce fluids that reduce viscosity, interfacial tension or mobility ratio, and thus improve flow and sweep efficiency to release the residual oil.
3714None
3715None
3716None
3717--
3718two pass method
37191.n. [Production Logging]
3720A technique for interpreting the results from a spinner flowmeter using two logging runs over the zone of interest, one up and one down. If the two passes are run at the same cable speed, they will overlay below the perforations, where there is no flow. If they were not run at the same speed, the curves are shifted to overlay. Elsewhere, the separation between the curves gives the relative contribution of each zone. Viscosity changes should have a small effect, since they will have the same influence on both passes.The technique is applicable when the flow is single-phase, or else multiphase with a sufficiently homogeneous-flow regime, such as with emulsion or dispersed bubble flow.
3721effective velocity, flow profile, flow regime, multipass method, single-pass method, spinner flowmeter, spinner reversal, threshold velocity, velocity-correction factor
3722None
3723None
3724--
3725thermal diffusion length
37261.n. [Formation Evaluation]
3727A parameter used to characterize thermal neutron interactions in bulk material. Thermal diffusion length (Ld) is the characteristic distance between the point at which a neutron becomes thermal and the point of its final capture. It is related to the quantity of thermal absorbers in the formation, and therefore is an important factor in the <a href="Display.cfm?Term=thermal%20neutron%20porosity%20measurement">thermal neutron <a href="Display.cfm?Term=porosity">porosity measurement. Thermal neutrons have about the same energy as the surrounding matter, typically less than 0.4 eV (0.025 eV at room temperature).
3728chemical neutron source, neutron capture, neutron interactions
3729None
3730None
3731--
3732tight gas
37331.n. [Shale Gas, Geology]
3734Gas produced from a relatively impermeable reservoir rock. Hydrocarbon production from tight reservoirs can be difficult without stimulation operations. Stimulation of tight formations can result in increased production from formations that previously might have been abandoned or been produced uneconomically. The term is generally used for reservoirs other than shales.
3735tight oil, unconventional resource, shale gas, shale oil
3736None
3737None
3738--
3739traveling valve
37401.n. [Production Testing]
3741In a subsurface sucker-rod pump, the valve that closes the barrel chamber allowing the trapped fluid to be lifted in the upstroke of the pump. This valve is similar in configuration to the standing valve.
3742standing valve, sucker rod
3743None
3744None
3745--
3746two phase separator
37471.n. [Production Facilities]
3748A vessel that separates the well fluids into gas and total liquid. A two-phase separator can be horizontal, vertical or spherical. The liquid (oil, emulsion) leaves the vessel at the bottom through a level-control or dump valve. The gas leaves the vessel at the top, passing through a mist extractor to remove the small liquid droplets in the gas.
3749horizontal separator, mist extractor, spherical separator, stage separation, vertical separator
3750None
3751None
3752--
3753thermal gradient
37541.n. [Drilling Fluids, Geology]
3755Also known as geothermal gradient, the rate of increase in temperature per unit depth in the Earth. Although the geothermal gradient varies from place to place, it averages 25 to 30 °C/km [15 °F/1000 ft].Temperature gradients sometimes increase dramatically around volcanic areas. It is particularly important for drilling fluids engineers to know the geothermal gradient in an area when they are designing a deep well. The downhole temperature can be calculated by adding the surface temperature to the product of the depth and the geothermal gradient.
3756high-pressure, high-temperature filtration test, mud engineer
3757geothermal gradient, temperature gradient
3758None
3759--
3760tight hole
37611.n. [Drilling]
3762A section of a wellbore, usually openhole, where larger diameter components of the drillstring, such as drillpipe tool joints, drill collars, stabilizers, and the bit, may experience resistance when the driller attempts to pull them through these sections.
3763openhole, tool joint
3764None
3765None
3766--
3767tight hole
37682.n. [Drilling]
3769A well that the operator requires be kept as secret as possible, especially the geologic information. Exploration wells, especially rank wildcats, are often designated as tight. Unfortunately, this designation is of questionable benefit in keeping the data secret.
3770wildcat
3771None
3772None
3773--
3774traveltime
37751.n. [Geophysics]
3776The 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.
3777acoustic log, average velocity, depth map, depth migration, isochron map, receiver, signal, sonic log, source, two-way traveltime, wave
3778acoustic traveltime
3779None
3780--
3781type curve analysis
37821.n. [Well Testing]
3783A method for quantifying well andreservoirparameters such aspermeability,skin,fracturehalf-length, dual-porosityparameters, and others, by comparing thepressurechange and its derivative of the acquired data to reservoirmodelcurve families, called type curves. When a match is found between data and a type curve, the parameters that characterize the behavior of the model providing a match are thereby determined.Originally, type-curve analysis was done manually using only the pressure change. With the introduction of the pressure derivative, the analysis requires matching both pressure change and its derivative. Computer-assisted matching permits rigorous accounting forsuperpositionin time due to flow-rate variations before and even during (in the case ofdrawdownanalysis) the transient dataacquisition, as well as providing a continuum of solutions instead of a type-curve family derived from discrete values for the governing parameters.
3784superposition in time, type curves
3785None
3786None
3787--
3788thermal neutron absorber
37891.n. [Formation Evaluation]
3790An element, or mineral, that is particularly effective in absorbing thermal neutrons (neutrons with about the same energy as the surrounding matter, typically less than 0.4 eV). The elements gadolinium, boron, chlorine, hydrogen and iron are thermal absorbers (in decreasing order of effectiveness). The effect of chlorine is used in a pulsed neutron capture log to distinguish salty water from hydrocarbons. In a <a href="Display.cfm?Term=thermal%20neutron%20porosity%20measurement">thermal neutron <a href="Display.cfm?Term=porosity">porosity measurement, the effect of hydrogen is important, while boron and iron affect the response in shales.
3791neutron capture, neutron interactions, thermal diffusion length
3792None
3793None
3794--
3795tight oil
37961.n. [Geology]
3797Oil found in relativelyimpermeablereservoir rock. Production of tight oil comes from very low permeability rock that must be stimulated using hydraulic fracturing to create sufficient permeability to allow the mature oil and/or natural gas liquids to flow at economic rates.
3798tight gas, shale gas, shale oil, unconventional resource
3799None
3800None
3801--
3802treater
38031.n. [Production Facilities]
3804A vessel used to treat oil-water emulsions so the oil can be accepted by the pipeline or transport. A treater can use several mechanisms. These include heat, gravity segregation, chemical additives and electric current to break emulsions.There are vertical and horizontal treaters. The main difference between them is the residence time, which is shorter in the vertical configuration compared with the horizontal one.A treater can be called a heater treater or an emulsion treater.
3805demulsifier, heater, heater treater
3806None
3807None
3808--
3809type curves
38101.n. [Well Testing]
3811Families of the paired pressure change and its derivative computed from a model. The model is usually generated from an analytical solution of the diffusion equation with boundary conditions strategically defined to enable observation of theoretical trends in the pressure-transient response. The boundary conditions that can be defined near the well include constant or variable wellbore storage, limited entry (partial penetration), radial composite (damage skin due to permeability alteration), and a fracture extending the cylindrical wellbore to a extended plane. The borehole trajectory can be vertical, angled, or horizontal. The distant boundary conditions include a sealing or partially sealing planar boundary (fault), intersecting faults and rectangular boundaries (sealing or constant pressure). Further, the diffusion equation can be adjusted to accommodate reservoir heterogeneity in the form of dual porosity or layering. Finally, when generated with computer assistance, the type-curve family can account for superposition in time due to flow-rate variations before and even during the transient data acquisition.Originally, type-curve families were printed on specialized (usually log-log) coordinates with dimensionless parameters defining the x and y axes. Today, commercial software can generate the type-curve families on the computer screen, enabling a much more flexible and user-friendly analysis. Further, automated regression (usually least squares) permits an optimized match between the acquired data and a selected model.Type curves have greatly enriched the ability of interpreters to extract potential explanations for transient data trends that differ from the radial-flow behavior required for conventional semilog (Horner buildup) analysis.
3812diffusion equation, superposition in time
3813None
3814None
3815--
3816thermal neutron porosity measurement
38171.n. [Formation Evaluation]
3818A measurement of the slowing down and capture of neutrons between a source and one or more thermal neutron detectors. The neutron source emits high-energy neutrons that are slowed mainly by elastic scattering to near thermal levels. Thermal neutrons have about the same energy as the surrounding matter, typically less than 0.4 eV. The slowing-down process is dominated by hydrogen. At thermal levels, the neutrons diffuse through the material until they undergo thermal capture. Capture is dominated by chlorine, hydrogen and other thermal neutron absorbers.Typical thermal neutron measurements use a chemical neutron source and two thermal neutron detectors. An accelerator source (neutron generator) is sometimes used. Some, mainly earlier, devices measure the gamma rays emitted by thermal capture, rather than thermal neutrons.
3819chemical neutron source, elastic neutron scattering, epithermal neutron porosity measurement, excavation effect, hydrogen index, limestone porosity unit, limestone-compatible scale, neutron capture, neutron interactions, slowing-down length, slowing-down time, thermal diffusion length
3820None
3821None
3822--
3823tih
38241.n. [Geophysics]
3825Abbreviation for horizontal transverse isotropy. Transverse isotropy that has a horizontal axis of rotational symmetry. In vertically fractured rocks, properties are uniform in vertical planes parallel to the fractures, but vary in the direction perpendicular to the fractures and across the fractures.
3826None
3827None
3828horizontal transverse isotropy, HTI
3829--
3830treatment fluid
38311.n. [Well Workover and Intervention]
3832A fluid designed and prepared to resolve a specific wellbore or reservoir condition. Treatment fluids are typically prepared at the wellsite for a wide range of purposes, such as stimulation, isolation or control of reservoir gas or water. Every treatment fluid is intended for specific conditions and should be prepared and used as directed to ensure reliable and predictable performance.
3833None
3834None
3835None
3836--
3837type curve analysis
38381.n. [Well Testing]
3839A method for quantifying well and reservoir parameters such as permeability, skin, fracture half-length, dual-porosity parameters, and others, by comparing the pressure change and its derivative of the acquired data to reservoir model curve families, called type curves. When a match is found between data and a type curve, the parameters that characterize the behavior of the model providing a match are thereby determined.Originally, type-curve analysis was done manually using only the pressure change. With the introduction of the pressure derivative, the analysis requires matching both pressure change and its derivative. Computer-assisted matching permits rigorous accounting for superposition in time due to flow-rate variations before and even during (in the case of drawdown analysis) the transient data acquisition, as well as providing a continuum of solutions instead of a type-curve family derived from discrete values for the governing parameters.
3840superposition in time, type curves
3841None
3842None
3843--
3844udden wentworth scale
38451.n. [Geology]
3846A grade scale for classifying the diameters of sediments. Particles larger than 64 mm in diameter are classified as cobbles. Smaller particles are pebbles, granules, sand and silt. Those smaller than 0.0039 mm are clay. Several other grain size scales are in use, but the Udden-Wentworth scale (commonly called the Wentworth scale) is the one that is most frequently used in geology.
3847arenaceous, argillaceous, sediment, sorting
3848None
3849Wentworth scale
3850--
3851unconformity
38521.n. [Geology]
3853A geological surface separating older from younger rocks and representing a gap in the geologic record. Such a surface might result from a hiatus in deposition of sediments, possibly in combination with erosion, or deformation such as faulting. An angular unconformity separates younger strata from eroded, dipping older strata. A disconformity represents a time of nondeposition, possibly combined with erosion, and can be difficult to distinguish within a series of parallel strata. A nonconformity separates overlying strata from eroded, older igneous or metamorphic rocks. The study and interpretation of unconformities locally, regionally and globally is the basis of sequence stratigraphy.
3854angular unconformity, basement, conformable, hiatus, lithologic contact, sequence boundary, sequence stratigraphy, stratigraphic trap, stratum, unconformity trap
3855None
3856None
3857--
3858underground blowout
38591.n. [Drilling]
3860The uncontrolled flow of reservoir fluids from one reservoir into the wellbore, along the wellbore, and into another reservoir. This crossflow from one zone to another can occur when a high-pressure zone is encountered, the well flows, and the drilling crew reacts properly and closes the blowout preventers (BOPs). Pressure in the annulus then builds up to the point at which a weak zone fractures. Depending on the pressure at which the fracturing occurs, the flowing formation can continue to flow and losses continue to occur in the fractured zone. Underground blowouts are historically the most expensive problem in the drilling arena, eclipsing the costs of even surface blowouts. It may prove necessary to drill a second kill well in order to remedy an underground blowout.
3861blowout, blowout preventer, kill
3862None
3863None
3864--
3865undershooting
38661.n. [Geophysics]
3867A technique for acquisition of seismic data beneath areas that are difficult to access at the surface of the Earth, such as near rivers, drilling rigs, production platforms, environmentally sensitive areas or around seismically problematic features such as salt domes, which introduce uncertainty because of their high velocity. The sources and receivers are located on opposite sides of the feature.
3868acquisition, receiver, source
3869None
3870None
3871--
3872ultrasonic caliper
38731.n. [Production Logging]
3874A device for measuring the internal diameter of a casing, tubing or open borehole using high-frequency acoustic signals. A transducer (in transmit mode) emits a high-frequency pulse that is reflected by the pipe or borehole wall back to the transducer (in receive mode). The diameter is determined from the time of flight of this echo and the fluid acoustic velocity. The transducer is rotated to produce a cross section of the borehole size and full-coverage images of the borehole wall. The measurement has high resolution and is used to detect deformations, the buildup of scale, or metal loss due to corrosion.The amplitude of the echo from the inner casing surface provides qualitative information on the state of the surface, such as rugosity or corrosion. Casing thickness may also be measured simultaneously, either by analysis of the casing resonance signal, or by detecting separately the echoes from the inner and outer casing surfaces.
3875acoustic velocity, borehole televiewer, casing-inspection log, electromagnetic caliper, multifinger caliper, ultrasonic measurement
3876None
3877None
3878--
3879underbalance
38801.n. [Drilling]
3881The amount of pressure (or force per unit area) exerted on a formation exposed in a wellbore below the internal fluid pressure of that formation. If sufficient porosity and permeability exist, formation fluids enter the wellbore. The drilling rate typically increases as an underbalanced condition is approached.
3882coiled tubing drilling, hydrostatic pressure, kill
3883None
3884Antonyms:overbalance
3885--
3886underream
38871.vb. [Drilling]
3888To enlarge a wellbore past its original drilled size. Underreaming is sometimes done for safety or efficiency reasons. Some well planners believe it is safer to drill unknown shallow formations with a small-diameter bit, and if no gas is encountered, to then enlarge the pilot hole. An underreaming operation may also be done if a small additional amount of annular space is desired, as might be the case in running a liner if surge pressures were problematic.
3889bicenter bit, liner, ream
3890None
3891None
3892--
3893unloading valve
38941.n. [Well Workover and Intervention]
3895Another term for circulation valve, a downhole device that enablescirculationthrough the tubing string and associatedannulus. As a completionaccessory, a circulation valve is included tocirculatefluid for wellkillor kickoff. Circulation valves typically are operated byslicklinetools and are generally capable of several opening and closing cycles before requiring service.
3896None
3897circulation valve
3898None
3899--
3900uncertainty
39011.n. [Formation Evaluation]
3902Result of the evaluation aimed at characterizing the range within which the true value of a quantity is estimated to lie, generally with a given likelihood. (ISO)The uncertainty is the amount of possible inaccuracy. It is often a statistical estimate of this range, such as the half-width of a gaussian distribution. The quantity may have been measured or derived from an equation.
3903accuracy, precision, repeatability, reproducibility
3904None
3905None
3906--
3907uncertainty
39082.n. [Reservoir Characterization]
3909The degree to which a data set may be in error or stray from predicted values. Sometimes quantified in terms of variance or standard deviation, uncertainty exists in data because of a variety of problems, such as poor calibration or contamination or damage to rocks prior to measurement. Uncertainty is the cause of many problems, which occasionally can be overcome by normalizing the data.
3910None
3911None
3912None
3913--
3914underbalanced
39151.adj. [Drilling]
3916Referring to a situation when the pressure(or force per unit area) exerted on aformationexposed in a wellbore is less than the internal fluid pressure of that formation. If sufficientporosityandpermeabilityexist, formation fluids enter the wellbore. Thedrilling ratetypically increases as an underbalanced condition is approached.
3917coiled tubing drilling, hydrostatic pressure, kill
3918None
3919Antonyms:overbalance
3920--
3921undersaturated fluid
39221.n. [Drilling Fluids]
3923A solution that could contain more solute than is presently dissolved in it. In brines, an undersaturated solution will not form crystals as easily as if it were saturated or supersaturated. In saltwater muds, an under-saturated fluid is used to allow salt to leach into the mud, keeping the hole from closing in on the drilling assembly. For moisture in air, a relative humidity of less than 100% is under-saturated.
3924brine, relative humidity, saltwater mud, saturation
3925None
3926None
3927--
3928unsteady state
39291.n. [Formation Evaluation]
3930A system that is in a transient state at the time of a measurement. In the case of permeability measurements on core samples, two transient techniques are used. In the pressure falloff method, the sample is at atmospheric pressure, either in a chamber or under a probe. Fluid at a higher pressure is released into one end of the sample. The decay of pressure with time at that end of the sample is recorded and analyzed by techniques similar to those used for transient well tests. In the pulse-decay method, the sample is held in a chamber and connected to two reservoirs, all of which are filled with a fluid at high pressure. The pressure in one of the reservoirs is increased a small amount and then re-connected to the sample. The change in pressure with time of this sample is recorded and analyzed using flow equations.
3931core plug, inertial resistance, permeameter, retort method, routine core analysis
3932None
3933Antonyms:steady state
3934--
3935vama
39361.n. [Drilling Fluids]
3937A copolymer of vinyl acetate (ethylenic polymer) and anhydrous maleic acid (a di-hydroxy acid). The vinyl acetate polymer component is usually high molecular weight. As such, with polar groups on the structure, it is used as a flocculant or bentonite extender.
3938None
3939None
3940vinyl acetate-maleic anhydride copolymer
3941--
3942velocity image
39431.n. [Production Logging]
3944A two-dimensional display, using colors or different gray scales, of the bubble velocity around the borehole against depth. The x-axis of the image shows different segments of the borehole, normally inside a casing, displayed from the top of the hole clockwise around through the bottom and back to the top again. Depth is in the z-axis, while the values of bubble velocity are represented by different colors or changes from black to white.The velocity image is constructed from between four and eight local probe measurements using interpolation within constraints. Images, sometimes called maps, are also made for bubble count and holdup.
3945bubble count, electric probe, holdup image, local holdup, optical probe, production log
3946velocity map
3947None
3948--
3949vertical resolution
39501.n. [Formation Evaluation]
3951A distance that characterizes the ability of a logging tool to resolve changes parallel to the tool axis. The word vertical implies a vertical well, but the term is used at other wellbore deviations. The vertical resolution summarizes the vertical response of the measurement in one or more distances. Most quoted vertical resolutions assume a homogeneous formation with stated properties. Vertical resolutions can vary considerably in more complex conditions, and at different values of the properties concerned. They should be considered only a qualitative guide to tool response.There are several different definitions of the vertical resolution distance. First, and most commonly, it is the interval within which a large percentage, typically 90%, of the vertical response occurs. Second, it is the minimum bed thickness needed for the measurement to read within a small percentage, typically 10%, of the true value at the center of the bed. Third, it may refer to the smallest bed thickness for which a significant change can be detected by the measurement.For acoustic and electromagnetic propagation measurements, it is taken, with reasonable accuracy, as the span of the receiver array. For nuclear and nuclear magnetic resonance measurements, which must be acquired during a significant time interval, the vertical resolution also depends on the logging speed and the precision required.
3952alpha processing, electromagnetic propagation measurement, geometrical factor, nuclear magnetic resonance measurement, radial response
3953None
3954None
3955--
3956vitrinite reflectance
39571.n. [Geology]
3958A measurement of the maturity of organic matter with respect to whether it has generated hydrocarbons or could be an effective source rock.
3959generation, geochemistry, geologic time scale, kerogen, maturity, source rock, vitrinite
3960None
3961None
3962--
3963vitrinite reflectance
39642.n. [Shale Gas]
3965A measure of the thermal maturity of organic matter. This analytical method was developed to rank the maturity of coals and is now used in other rocks to determine whether they have generated hydrocarbons or could be effective source rocks. The reflectivity of at least 30 individual grains of vitrinite from a rock sample is measured under a microscope. The measurement is given in units of reflectance, % Ro, with typical values ranging from 0% Ro to 3% Ro, with values for gas-generating source rocks typically exceeding 1.5%. Strictly speaking, the plant material that forms vitrinite did not occur prior to Ordovician time, although geochemists have established a scale of equivalent vitrinite reflectance for rocks older than Ordovician.
3966None
3967None
3968None
3969--
3970variable orifice
39711.n. [Production]
3972A small variable profile valve put in a flowline and used with a pilot to restrict the flow into the pilot and make the pilot more or less sensitive to changing conditions.
3973None
3974None
3975None
3976--
3977velocity map
39781.n. [Production Logging]
3979Another term for velocity image, a two-dimensional display, using colors or different gray scales, of the bubblevelocityaround the boreholeagainst depth. The x-axis of theimageshows different segments of the borehole, normally inside acasing, displayed from the top of the hole clockwise around through the bottom and back to the top again. Depth is in the z-axis, while the values of bubble velocity are represented by different colors or changes from black to white.The velocity image is constructed from between four and eightlocal probemeasurements using interpolationwithin constraints. Images, sometimes called maps, are also made for bubble count and holdup.
3980bubble count, electric probe, holdup image, local holdup, optical probe, production log
3981velocity image
3982None
3983--
3984vertical response
39851.n. [Formation Evaluation]
3986The response of a logging measurement as a function of distance parallel to the tool axis. The word vertical implies a vertical well, but the term is used at other wellbore deviations.Vertical responses are determined by computer simulation or laboratory measurement. For some measurements, mainly resistivity, the vertical response can be shaped as desired through signal processing. In general, the vertical response depends on the formation properties throughout the measurement volume. Most quoted vertical responses have been determined in formations that are radially homogeneous and have small vertical changes. They can then be summarized by a geometrical factor or a pseudogeometrical factor. These factors are appropriate for volumetric measurements such as nuclear and resistivity, but not for others such as acoustic propagation.
3987radial response, vertical resolution
3988None
3989None
3990--
3991volcanic
39921.adj. [Geology]
3993Pertaining to one or more volcanoes, surface features of the Earth that allow magma, ash and gas to erupt. The vent can be a fissure or a conicalstructure.
3994collision, earthquake, igneous, magma, subduction
3995None
3996None
3997--
3998variogram
39991.n. [Geophysics]
4000A two-point statistical function that describes the increasing difference or decreasing correlation, or continuity, between sample values as separation between them increases.
4001kriging
4002None
4003None
4004--
4005variogram
40062.n. [Reservoir Characterization]
4007A two-point statistical function that describes the increasing differences or decreasing correlation, or continuity, between sample values as separation between them increases.The term variogram is sometimes used incorrectly in place of semivariogram. The two differ only in that the semivariogram uses each pair of data elements only once, whereas the variogram uses all possible data pairs. Semivariograms are usually used instead of variograms, but opposite vector directions (for example, north and south) are recognized as representing the same thing and having identical ranges, sills, nugget points and the like.
4008None
4009None
4010None
4011--
4012velocity shot measurement
40131.n. [Production Logging]
4014A method of producing a radioactive-tracerlog, in which aslugof radioactive material is injected into the flow streamof aproductionorinjection wellfrom one section of aloggingtool and observed as it passes one or more gamma ray detectors in another section. The slug, or shot, causes apeakin the gamma ray reading as it passes adetector. The flowvelocityis determined from the difference in the time of arrival of the slug at the two detectors, or between ejector and detector. This technique has been applied for many years using radioactive tracers such as iodine. Water-soluble tracers are the most common, but oil- and gas-soluble tracers are also used.Velocity-shot measurements are recorded with the tool stationary. They are more accurate than flowmeters at low flow rates, below approximately 100 B/D [16m3/d]. They are not usuallyrunin production wells because of problems of tracer disposal. Inmultiphaseflow, the tracer most often travels with thecontinuous phase, thereby giving a type ofphase-velocity log.
4015interval method, production log, timed-slug analysis, tracer measurement, tracer-loss measurement
4016tracer ejector measurement
4017None
4018--
4019vertical seismic profile
40201.n. [Geophysics]
4021A class of borehole seismic measurements used for correlation with surface seismic data, for obtaining images of higher resolution than surface seismic images and for looking ahead of the drill bit; also called a VSP. Purely defined, VSP refers to measurements made in a vertical wellbore using geophones inside the wellbore and a source at the surface near the well. In the more general context, VSPs vary in the well configuration, the number and location of sources and geophones, and how they are deployed. Most VSPs use a surface seismic source, which is commonly a vibrator on land and an air gun in offshore or marine environments. VSPs include the zero-offset VSP, offset VSP, walkaway VSP, walk-above VSP, salt-proximity VSP, shear-wave VSP, and drill-noise or seismic-while-drilling VSP. A VSP is a much more detailed survey than a check-shot survey because the geophones are more closely spaced, typically on the order of 25 m [82 ft], whereas a check-shot survey might include measurements of intervals hundreds of meters apart. Also, a VSP uses the reflected energy contained in the recorded trace at each receiver position as well as the first direct path from source to receiver. The check-shot survey uses only the direct path traveltime. In addition to tying well data to seismic data, the vertical seismic profile also enables converting seismic data to zero-phase data and distinguishing primary reflections from multiples.
4022air gun, apparent anisotropy, borehole seismic data, check-shot survey, depth conversion, drill-noise vertical seismic profile, first break, multiple reflection, one-way time, primary reflection, salt-proximity vertical seismic profile, seismic-while-drilling vertical seismic profile, Stoneley wave, walk-above vertical seismic profile, walkaway vertical seismic profile, zero-offset vertical seismic profile
4023None
4024VSP
4025--
4026volcano
40271.n. [Geology]
4028A surface feature of the Earth that allows magma, ash and gas to erupt. The vent can be a fissure or a conical structure.
4029collision, earthquake, igneous, magma, subduction
4030None
4031None
4032--
4033vee door
40341.n. [Drilling]
4035The upside down V-shaped opening in one side of the derrick that enables long pipes and tools to be lifted into the interior of the derrick. This opening is aligned with the slide and catwalk of the rig.
4036vee-door
4037None
4038None
4039--
4040vee door
40412.n. [Drilling]
4042The open location on a mast-type rig (nonderrick) that functions like the vee-door. At least two sides are open on most mast rigs. Hence, the open side adjacent to the slide and catwalk is considered the vee-door. The vee-door is really a hole and has no true door that can be closed or locked, so inexperienced visitors to a rigsite are sometimes asked by the rig crew to find the key to the vee-door as a joke.
4043None
4044None
4045None
4046--
4047velocity string
40481.n. [Well Completions]
4049A small-diameter tubing string run inside the production tubing of a well as a remedial treatment to resolve liquid-loading problems. As the reservoir pressure in a gas well depletes, there may be insufficient velocity to transport all liquids from the wellbore. In time these liquids accumulate and impair production. Installing a velocity string reduces the flow area and increases the flow velocity to enable liquids to be carried from the wellbore. Velocity strings are commonly run using coiled tubing as a velocity string conduit. Safe live-well working and rapid mobilization enable coiled tubing velocity strings to provide a cost effective solution to liquid loading in gas wells.
4050coiled tubing
4051None
4052None
4053--
4054vertical transverse isotropy
40551.n. [Geophysics]
4056Transverse isotropy that has a vertical axis of rotational symmetry. In layered rocks, properties are uniform horizontally within a layer, but vary vertically and from layer to layer.
4057None
4058None
4059TIV, VTI
4060--
4061volumetric cross section
40621.n. [Formation Evaluation]
4063The cross section of a material to photoelectric absorption, in barns/cm3. The volumetric cross section, U, is from the product of the photoelectric factor, PEF or Pe , and the electron density. In practice, U is usually calculated using the bulk density instead of the electron density. U is a volumetric quantity, whereas Pe is not. U is more useful in log interpretation since it can be used in a linear mixing law in terms of the volumes of the formation components.
4064density measurement, Z/A effect
4065None
4066None
4067--
4068vee door
40691.n. [Drilling]
4070The upside down V-shaped opening in one side of the derrick that enables long pipes and tools to be lifted into the interior of the derrick. This opening is aligned with the slide and catwalk of the rig.
4071catwalk, mousehole, racking back pipe, slide, slide
4072None
4073None
4074--
4075vee door
40762.n. [Drilling]
4077The open location on a mast-type rig (nonderrick) that functions like the vee-door. At least two sides are open on most mast rigs. Hence, the open side adjacent to the slide and catwalk is considered the vee-door. The vee-door is really a hole and has no true door that can be closed or locked, so inexperienced visitors to a rigsite are sometimes asked by the rig crew to find the key to the vee-door as a joke.
4078mast
4079None
4080None
4081--
4082velocity correction factor
40831.n. [Production Logging]
4084The factor linking the velocity of single-phase liquid flow measured in the center of a pipe with the average velocity across the pipe. For vertical pipes with turbulent flow measured by standard flowmeters, the velocity-correction factor varies within a range of 0.75 to 0.95, but is often taken as 0.83. For laminar flow, it is theoretically 0.5.
4085flow profile, laminar flow, spinner flowmeter
4086None
4087None
4088--
4089vibratory seismic data
40901.n. [Geophysics]
4091Seismic data whose energy source is a truck-mounted device called a vibrator that uses a vibrating plate to generate waves of seismic energy; also known as Vibroseis data (Vibroseis is a mark of Conoco). The frequency and duration of the energy can be controlled and varied according to the terrain and type of seismic data desired. The vibrator typically emits a linear "sweep" of at least seven seconds, beginning with high frequencies and decreasing with time ("downsweeping") or going from low to high frequency ("upsweeping"). The frequency can also be changed in a nonlinear manner, such that certain frequencies are emitted longer than others. The resulting source wavelet is not impulsive. Vibrators are employed in land acquisition in areas where explosive sources cannot be used, and more than one vibrator can be used simultaneously to improve data quality.
4092acquisition, explosive seismic data, frequency, impulsive seismic data, source, vibrator, wave
4093None
4094None
4095--
4096volumetric displacement efficiency
40971.n. [Enhanced Oil Recovery]
4098Another term for volumetric sweep efficiency, a measure of the effectiveness of an enhanced oilrecoveryprocess that depends on the volume of the reservoircontacted by the injected fluid. Thevolumetric sweep efficiency is an overall result that depends on theinjection patternselected, off-pattern wells, fractures in the reservoir, position of gas-oil and oil/water contacts, reservoir thickness,permeabilityand areal and verticalheterogeneity,mobility ratio, density difference between the displacing and the displaced fluid, and flow rate.
4099gas-oil contact, oil-water contact
4100volumetric sweep efficiency
4101None
4102--
4103velocity
41041.n. [Geophysics]
4105The rate at which a wave travels through a medium (a scalar) or the rate at which a body is displaced in a given direction (a vector), commonly symbolized by v. 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. Velocity 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.
4106acoustic, 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, Poisson's ratio, 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 analysis, velocity anomaly, velocity correction, velocity layering, velocity survey, vertical seismic profile, wave, wave equation, wavelength, weathering correction
4107acoustic velocity, seismic velocity
4108None
4109--
4110velocity shot measurement
41111.n. [Production Logging]
4112A method of producing a <a href="Display.cfm?Term=radioactive%2Dtracer%20log">radioactive-<a href="Display.cfm?Term=tracer">tracer log, in which a slug of radioactive material is injected into the flow stream of a production or injection well from one section of a logging tool and observed as it passes one or more gamma ray detectors in another section. The slug, or shot, causes a peak in the gamma ray reading as it passes a detector. The flow velocity is determined from the difference in the time of arrival of the slug at the two detectors, or between ejector and detector. This technique has been applied for many years using radioactive tracers such as iodine. Water-soluble tracers are the most common, but oil- and gas-soluble tracers are also used.Velocity-shot measurements are recorded with the tool stationary. They are more accurate than flowmeters at low flow rates, below approximately 100 B/D [16m3/d]. They are not usually run in production wells because of problems of tracer disposal. In multiphase flow, the tracer most often travels with the continuous phase, thereby giving a type of phase-velocity log.
4113interval method, production log, timed-slug analysis, tracer measurement, tracer-loss measurement
4114tracer-ejector measurement
4115None
4116--
4117vinyl acetate maleic anhydride copolymer
41181.n. [Drilling Fluids]
4119A copolymer of vinyl acetate (ethylenic polymer) and anhydrous maleic acid (a di-hydroxy acid). The vinyl acetate polymer component is usually high molecular weight. As such, with polar groups on the structure, it is used as a flocculant or bentonite extender.
4120clay extender, clay-water interaction, closed mud system, polar, vinyl polymer, wastewater cleanup
4121None
4122VAMA
4123--
4124volumetric efficiency
41251.n. [Drilling]
4126The ratio of the actual output volume of a <a href="Display.cfm?Term=positive%20displacement%20pump">positive <a href="Display.cfm?Term=displacement">displacement pump divided by the theoretical geometric maximum volume of liquid that the pump could output under perfect conditions. Inefficiencies are caused by gaseous components (air and methane) being trapped in the liquid mud, leaking and noninstantaneously sealing valves in the pumps, fluid bypass of pump swab seals, and mechanical clearances and "play" in various bearings and connecting rods in the pumps. This efficiency is usually expressed as a percentage, and ranges from about 92% to 99% for most modern rig pumps and cement pumps. For critical calculations, this efficiency can be determined by a rigsite version of the "bucket and stopwatch" technique, whereby the rig crew will count the number of pump strokes required to pump a known volume of fluid. In cementing operations, displacement is often measured by alternating between two 10-bbl displacement tanks.
4127swab
4128None
4129None
4130--
4131volumetric efficiency
41322.n. [Production Testing]
4133The relationship between actual pumpdisplacementand the pump displacement under ideal conditions. The relationship can be expressed as percentage. A reduction in pump volumetric efficiencyis an indication of an operational problem in the well. In sucker-rod pumps, thegas lockandgas interference phenomena can significantly reduce the volumetric efficiency of the pump.
4134None
4135pump volumetric efficiency
4136None
4137--
4138velocity analysis
41391.n. [Geophysics]
4140The process of calculating seismic velocity, typically by using common midpoint data, in order to better process seismic data. Successful stacking, time migration and depth migration all require proper velocity inputs. Velocity or stacking velocity can be calculated from normal moveout, or the change in arrival time produced by source-receiver offset.
4141common midpoint, geophone, migration, normal moveout, stack, stacking velocity, time migration, velocity
4142None
4143None
4144--
4145vent plug
41461.n. [Production]
4147A special pipe plug having a small Allen-wrench-operated vent valve. These special plugs are located at the bottom of most ball valves. With the line valve closed (and under pressure), the body cavity pressure can be vented through this small valve to check the tightness of seat seals or to make minor repairs. Having vented the body pressure, the vent plug can be removed to blow out debris and foreign material or to flush the body cavity. On some gate valves, the vent plug is installed on the bonnet for the purpose of venting the body. Such valves have separate drain valves.
4148None
4149None
4150None
4151--
4152viscosity
41531.n. [Drilling Fluids]
4154A property of fluids and slurries that indicates their resistance to flow, defined as the ratio of shear stress to shear rate. Viscosity can be expressed mathematically as follows: Poise is the unit for viscosity, equivalent to dyne-sec/cm2. Because one poise represents a high viscosity, 1/100 poise, or one centipoise (cp), is used for mud measurements. One centipoise equals one millipascal-second. Viscosity must have a stated or an understood shear rate in order to be meaningful. Measurement temperature also must be stated or understood.
4155bentonite, Bingham plastic model, breaker, Brookfield viscometer, capillary tube viscometer, carboxymethylcellulose, centipoise, derrickman, direct-indicating viscometer, funnel viscosity, gel strength, gyp mud, Herschel-Bulkley fluid, high-pressure, high-temperature viscometer, Marsh funnel, mud additive, Newtonian fluid, non-Newtonian fluid, pill, plastic fluid, power-law fluid, pseudoplastic, PVT, rheological property, rheology, shear rate, shear stress, V-G meter, yield
4156None
4157None
4158--
4159volumetric sweep efficiency
41601.n. [Enhanced Oil Recovery]
4161A measure of the effectiveness of an enhanced oilrecoveryprocess that depends on the volume of the reservoircontacted by the injected fluid. Thevolumetric sweep efficiency is an overall result that depends on theinjection patternselected, off-pattern wells, fractures in the reservoir, position of gas-oil and oil/water contacts, reservoir thickness,permeabilityand areal and verticalheterogeneity,mobility ratio, density difference between the displacing and the displaced fluid, and flow rate.
4162None
4163gas-oil contact, oil-water contact
4164None
4165--
4166velocity anomaly
41671.n. [Geophysics]
4168A feature in seismic data that results from changes in velocity, both laterally and vertically. Pull-up and push-down are examples of velocity anomalies.
4169anomaly, pull-up, push-down, velocity
4170None
4171None
4172--
4173venturi valve
41741.n. [Production]
4175A venturi valve is a reduced-bore valve having a bore smaller in diameter than the inlet or outlet. For example, an 8-in. x 6-in. x 8-in. ball valve has 8-in. inlet and outlet connections, while the ball and seats are 6 in. The flow through a venturi valve will be reduced because of the smaller port. Venturi valves can often be economically substituted for plug valves.
4176None
4177None
4178None
4179--
4180viscosity and gel strength test
41811.n. [Drilling Fluids]
4182Measurement of the viscosity and gel strength of a drilling fluid.The gel strength is theshear stressmeasured at lowshear rateafter amudhas set quiescently for a period of time (10 seconds and 10 minutes in the standardAPIprocedure, although measurements after 30 minutes or 16 hours may also be made).Viscosity is measured using a Marsh funnel, a conical-shaped funnel, fitted with a small-bore tube on the bottom end through which mud flows under a gravity head. A screen over the top removes large particles that might plug the tube. In the test standardized by API for evaluating water-base and oil-base muds, the funnel viscosity measurement is the time (in seconds) required for one quart of mud to flow out of a Marsh funnel into a graduated mud cup. Funnel viscosity is reported in seconds (for a quart). Water exits the funnel in about 26 seconds. This test was one of the earliest mud measurements for field use. Simple, quick and fool-proof, it still serves as a useful indicator of change in the mud by comparing mud-in and mud-out sample funnel viscosities.Reference:Marsh H: "Properties and Treatment of Rotary Mud," Petroleum Development and Technology, Transactions of the AIME (1931): 234-251.
4183derrickman, funnel viscosity, gel strength, Marsh funnel, viscosity
4184None
4185None
4186--
4187vsp
41881.n. [Geophysics]
4189A class of borehole seismic measurements used for correlation with surface seismic data, for obtaining images of higher resolution than surface seismic images and for looking ahead of the drill bit; also called a VSP. Purely defined, VSP refers to measurements made in a vertical wellbore using geophones inside the wellbore and a source at the surface near the well. In the more general context, VSPs vary in the well configuration, the number and location of sources and geophones, and how they are deployed. Most VSPs use a surface seismic source, which is commonly a vibrator on land and an air gun in offshore or marine environments. VSPs include the zero-offset VSP, offset VSP, walkaway VSP, walk-above VSP, salt-proximity VSP, shear-wave VSP, and drill-noise or seismic-while-drilling VSP. A VSP is a much more detailed survey than a check-shot survey because the geophones are more closely spaced, typically on the order of 25 m [82 ft], whereas a check-shot survey might include measurements of intervals hundreds of meters apart. Also, a VSP uses the reflected energy contained in the recorded trace at each receiver position as well as the first direct path from source to receiver. The check-shot survey uses only the direct path traveltime. In addition to tying well data to seismic data, the vertical seismic profile also enables converting seismic data to zero-phase data and distinguishing primary reflections from multiples.
4190zero-offset vertical seismic profile
4191None
4192vertical seismic profile
4193--
4194velocity correction
41951.n. [Geophysics]
4196A change made in seismic data to present reflectors realistically. Velocity corrections typically require that assumptions be made about the seismic velocities of the rocks or sediments through which seismic waves pass.
4197velocity, wave
4198None
4199None
4200--
4201vertical resistivity
42021.n. [Formation Evaluation]
4203The resistivity of a formation measured by flowing current in a vertical plane. In anisotropic formations, the horizontal and vertical resistivities are different. In a vertical well, wireline induction logs and measurements-while-drilling propagation logs measure the horizontal resistivity, whereas laterologs measure the horizontal resistivity with some component of the vertical. In deviated and horizontal wells, all these logs measure some mixture of both vertical and horizontal resistivity.
4204electrical anisotropy, parallel resistivity, perpendicular resistivity
4205None
4206Antonyms:horizontal resistivity
4207--
4208viscous oil
42091.n. [Heavy Oil, Enhanced Oil Recovery]
4210Crude oil with highviscosity(typically above 10 cp), and highspecific gravity. TheAPIclassifies heavy oil as crudes with a gravity below 22.3° API. In addition to high viscosity and high specific gravity, heavy oils typically have low hydrogen-to-carbon ratios, high asphaltene, sulfur, nitrogen, and heavy-metal content, as well as higheracidnumbers.
4211crude oil
4212heavy oil
4213None
4214--
4215vti
42161.n. [Geophysics]
4217Abbreviation for vertical transverse isotropy. Transverse isotropy that has a vertical axis of rotational symmetry. In layered rocks, properties are uniform horizontally within a layer, but vary vertically and from layer to layer.
4218None
4219None
4220vertical transverse isotropy, TIV
4221--
4222velocity correction factor
42231.n. [Production Logging]
4224The factor linking thevelocityofsingle-phaseliquid flow measured in the center of a pipe with the average velocityacross the pipe. For vertical pipes withturbulent flowmeasured by standard flowmeters, the velocity-correction factor varies within a range of 0.75 to 0.95, but is often taken as 0.83. For laminar flow, it is theoretically 0.5.
4225flow profile, laminar flow, spinner flowmeter
4226None
4227None
4228--
4229wait on cement
42301.vb. [Drilling]
4231To suspend drilling operations while allowing cement slurries to solidify, harden and develop compressive strength. The drilling crew usually uses this time to catch up on maintenance items, to rig down one BOP and rig up another one for the new casing, to get tools and materials ready for the next hole section, and other non-drilling tasks. The WOC time ranges from a few hours to several days, depending on the difficulty and criticality of the cement job in question. WOC time allows cement to develop strength, and avert development of small cracks and other fluid pathways in the cement that might impair zonal isolation.
4232cement, cementing, rig down, rig up
4233None
4234WOC
4235--
4236wait on cement
42372.vb. [Well Completions]
4238To suspend operations while a cement slurry to develops sufficient compressive strength to allow drilling or other wellbore activity to continue. The WOC time is generally used to test the surface pressure-control equipment, such as the BOP stack. Attempting to drill out the float or guide shoe before the cement has developed sufficient bond strength may result in backing off a casing joint.
4239BOP stack, casing joint, float shoe, guide shoe
4240None
4241WOC
4242--
4243water production
42441.n. [Production Testing]
4245The volume of produced water associated with oil production. In waterdrive reservoirs, water production can be significantly higher than oil production from a field. Consequently, treatment and disposal of produced water, especially in remote locations, have an important impact on the feasibility of a project.
4246None
4247None
4248None
4249--
4250weighting material
42511.n. [Drilling Fluids]
4252A high-specific gravity and finely divided solid material used to increase density of a drilling fluid. (Dissolved salts that increase fluid density, such as calcium bromide in brines, are not called weighting materials.) Barite is the most common, with minimum specific gravity of 4.20 g/cm3. Hematite is a more dense material, with minimum specific gravity of 5.05 g/cm3, per API and ISO specifications. Calcium carbonate, specific gravity 2.7 to 2.8, is considered weighting material but is used more for its acid solubility than for density. Siderite, specific gravity around 3.8, has been used to densify mud, but can cause problems by dissolving into the mud at high pH. Ilmenite, specific gravity of 4.6 has been used in drilling fluid and cement. Only barite and hematite have API/ISO standards.
4253abrasion test, Brookfield viscometer, calcium carbonate, gel strength, high-gravity solids, iron oxide, mud additive, mud weight, slug, specific gravity, unweighted mud, weighted mud
4254weighting agent
4255None
4256--
4257wettability change
42581.n. [Enhanced Oil Recovery, Enhanced Oil Recovery]
4259A type of damage in which the formation wettability is modified, generating a change in relative permeability that eventually affects well productivity.Surfactants or other additives in drilling fluids, especially oil-base mud, or other injected fluids can change formation wettability. A naturally water-wet formation could be changed into an oil-wet formation with consequent production impairment caused by reduction of oil relative permeability.Wettability change is normally treated with mutual solvents to remove the rock-oil coating (asphaltene or paraffin precipitation), followed by a strong water-wet surfactant to reduce the tendency of further hydrocarbon precipitation.
4260drilling fluid
4261None
4262None
4263--
4264wait time
42651.n. [Formation Evaluation]
4266The time allotted for the alignment of protons with the static magnetic field during a nuclear magnetic resonance measurement. The term is used more generally with reference to logging tools, and is synonymous with the more general term polarization time.
4267nuclear magnetic resonance, nuclear magnetic resonance measurement
4268polarization time
4269None
4270--
4271water saturation
42721.n. [Formation Evaluation]
4273The fraction of water in a given pore space. It is expressed in volume/volume, percent or saturation units. Unless otherwise stated, water saturation is the fraction of formation water in the undisturbed zone. The saturation is known as the total water saturation if the pore space is the total porosity, but is known as effective water saturation if the pore space is the effective porosity. If used without qualification, the term usually refers to the effective water saturation.
4274flushed-zone water saturation, moveable hydrocarbons, moved hydrocarbons, residual oil
4275effective water saturation
4276None
4277--
4278well control
42791.n. [Drilling]
4280The technology focused on maintaining pressure on open formations (that is, exposed to the wellbore) to prevent or direct the flow of formation fluids into the wellbore. This technology encompasses the estimation of formation fluid pressures, the strength of the subsurface formations and the use of casing and mud density to offset those pressures in a predictable fashion. Also included are operational procedures to safely stop a well from flowing should an influx of formation fluid occur. To conduct well-control procedures, large valves are installed at the top of the well to enable wellsite personnel to close the well if necessary.
4281abnormal pressure, adjustable choke, aquifer, blowout preventer, BOP stack, check valve, crossflow, flapper valve, formation fluid, kill line, lost circulation, mud weight, openhole, ram blowout preventer, swab
4282None
4283None
4284--
4285whole core
42861.n. [Formation Evaluation]
4287A complete section of a conventionally drilled core. The section may be up to about 2 feet [0.6 m] in length, with typical core diameters lying between 1.75 and 5.25 in. [4.4 and 13.3 cm]. The term full-diameter core is also used, but generally refers to shorter sections of about 6 in. [15 cm]. The advantage of whole core analysis is that it measures properties on a larger scale, closer to that of the reservoir. This is particularly important for heterogeneous formations such as many carbonates or fractured materials.
4288core plug, routine core analysis, sidewall core
4289None
4290None
4291--
4292walk above vertical seismic profile
42931.n. [Geophysics]
4294A type of verticalseismicprofile to accommodate the geometry of a deviated well; sometimes called a vertical incidenceVSP. Eachreceiveris in a different lateral position with thesourcedirectly above the receiver for all cases. Such data provide a high-resolutionseismicimageof the subsurface below the trajectory of the well.
4295deviated hole, vertical seismic profile
4296None
4297None
4298--
4299water wet
43001.adj. [Enhanced Oil Recovery, Well Completions]
4301Pertaining to the adhesion of a liquid to the surface of a solid. In water-wet conditions, a thin film of water coats the surface of theformationmatrix, a condition that is desirable for efficient oil transport. Treatments that change thewettabilityof the formation from water-wet tooil-wetcan significantly impair productivity.
4302None
4303None
4304None
4305--
4306water wet
43072.adj. [Formation Evaluation]
4308Describing the preference of a solid to be in contact with a water phase rather than an oil or gas phase. Water-wet rocks preferentially imbibe water. Generally, sandstones and carbonates are water-wet before contact withcrude oil, but may be altered by components of the crude oil to becomeoil-wet. Certain minerals, as well as different crystallographic faces of the samemineral, may be variably prone to being oil- or water-wet.
4309drainage, fluid contact, imbibition, wettability
4310None
4311None
4312--
4313well interference testing
43141.n. [Well Testing]
4315Thepressurevariation with time recorded in observation wells resulting from changes in rates in productionor injection wells. In commercially viable reservoirs, it usually takes considerable time for production at one well to measurably affect the pressure at an adjacent well. Consequently, interference testing has been uncommon because of the cost and the difficulty in maintaining fixed flow rates over an extended time period. With the increasing number of permanent gauge installations, interference testing may become more common than in the past.
4316injection well
4317interference testing
4318None
4319--
4320whole mud dilution
43211.n. [Drilling Fluids]
4322A dilution process which involves selective dumping of the active system (such as sand traps and "bottoms up" mud) and replacement of the lost volume with fresh mud. This process has proved economical with inhibitive water-base systems and is the only method that actually removes colloidal size particles.
4323None
4324None
4325whole-mud dilution
4326--
4327walk above vsp
43281.n. [Geophysics]
4329A type of verticalseismicprofile to accommodate the geometry of a deviated well; sometimes called a vertical incidenceVSP. Eachreceiveris in a different lateral position with thesourcedirectly above the receiver for all cases. Such data provide a high-resolutionseismicimageof the subsurface below the trajectory of the well.
4330deviated hole, vertical seismic profile
4331None
4332None
4333--
4334water oil and solids test
43351.n. [Drilling Fluids]
4336A test for water mud or oil mud, generally known as the retort test. Proper procedures for retort tests have been published by API. The test is a distillation of a mud sample that measures condensed oil and water collected from the retort. Data obtained are: (1) vol. % water, (2) vol. % oil and (3) vol. % retort solids. Retort solids is the volume that was not recovered as a liquid. Three sizes of retort apparatus are available: 10-, 20- and 50-cm3 mud sample size. Some designs have a small oven in the carrying case to heat the sample (the preferred method for oil muds) while others use a blade heater that goes into the mud sample. Retorts should be heated to around 700°F [371°C] to be effective.
4337barite, bentonite, chloride test, dissolved solids, hematite, oil content, oil-water interface, oil/brine ratio, oil/water ratio, suspended solids, synthetic/brine ratio, total solids
4338retort test
4339None
4340--
4341well log
43421.n. [Formation Evaluation]
4343The measurement versus depth or time, or both, of one or more physical quantities in or around a well. The term comes from the word "log" used in the sense of a record or a note.Wirelinelogs are taken downhole, transmitted through a wireline to surface and recorded there.Measurements-while-drilling(MWD) andlogging while drilling(LWD) logs are also taken downhole. They are either transmitted to surface bymudpulses, or else recorded downhole and retrieved later when the instrument is brought to surface. Mud logs that describe samples of drilledcuttingsare taken and recorded on surface.
4344real-time data, recorded data
4345None
4346None
4347--
4348well log
43492.n. [Formation Evaluation]
4350The display of one or more log measurements on a strip of paper or film (a hard copy) with depth in one axis. In this sense, the term refers to the display not only of the measurement but of other relevant information. A typical log is presented on folded paper of indeterminate length, but about 8.5-in. [21.5-cm] wide. It consists of aheading, well sketch,logging toolsketch,insert, main log,repeat sectionandtail. When the term is used in this sense, each log measurement is usually referred to as acurve.
4351None
4352None
4353None
4354--
4355whole mud dilution
43561.n. [Drilling Fluids]
4357A dilution process which involves selective dumping of the active system (such as sand traps and "bottoms up" mud) and replacement of the lost volume with fresh mud. This process has proved economical with inhibitive water-base systems and is the only method that actually removes colloidal size particles.
4358bottoms-up mud sample, sand trap
4359None
4360None
4361--
4362walk above vertical seismic profile
43631.n. [Geophysics]
4364A type of vertical seismic profile to accommodate the geometry of a deviated well; sometimes called a vertical incidence VSP. Each receiver is in a different lateral position with the source directly above the receiver for all cases. Such data provide a high-resolution seismic image of the subsurface below the trajectory of the well.
4365deviated hole, vertical seismic profile
4366None
4367walk-above VSP
4368--
4369water cut meter
43701.n. [Production Logging]
4371A device for determining the water holdup in a producing well by measuring the capacitance or impedance of the fluid. The term is a misnomer because water cut is not the same as water holdup except in the unlikely case where all phases flow at the same velocity. Since hydrocarbons travel faster than water in a production well, the water holdup is larger than the water cut. However, the water-cut meter was often combined with a flowmeter so that the water cut could be estimated by combining the two measurements.
4372capacitance log, holdup log, production log
4373capacitance meter, holdup meter
4374None
4375--
4376well placement
43771.n. [Shale Gas]
4378Activities associated with drilling a wellbore to intercept one of more specified locations. The term usually is used in reference to directional or horizontal wells that are oriented to maximize contact with the most productive parts of reservoirs via hydraulic fracturing or to optimize intersection with natural fractures. Geomechanical analysis of natural fractures and stresses and geological analysis of the reservoir are critical to successful well planning. Advanced formation evaluation and drilling technology support the drilling operation in real time.
4379None
4380None
4381None
4382--
4383wide azimuth towed streamer acquisition
43841.n. [Geophysics]
4385A marine seismic data acquisition method that uses one or more vessels to tow source arrays and streamers to record seismic signals, along with one or more source-only vessels sailing parallel to, but at some specified distance from, the recording vessel(s). The source-only vessels provide offset sources that generate reflections from a wide range of azimuths; these reflections are received by streamers towed by the recording vessel(s).
4386None
4387None
4388None
4389--
4390walk above vsp
43911.n. [Geophysics]
4392A type of verticalseismicprofile to accommodate the geometry of a deviated well; sometimes called a vertical incidenceVSP. Eachreceiveris in a different lateral position with thesourcedirectly above the receiver for all cases. Such data provide a high-resolutionseismicimageof the subsurface below the trajectory of the well.
4393deviated hole, vertical seismic profile
4394None
4395None
4396--
4397waterdrive
43981.n. [Well Completions]
4399A reservoir-drive mechanism whereby the oil is driven through the reservoir by an active aquifer. As the reservoir depletes, the water moving in from the aquifer below displaces the oil until the aquifer energy is expended or the well eventually produces too much water to be viable.
4400reservoir, reservoir-drive mechanisms
4401None
4402None
4403--
4404waterdrive
44052.n. [Enhanced Oil Recovery]
4406A primary recovery mechanism in which the pressure from free water is sufficient to move hydrocarbons out of the reservoir, into the wellbore and up to surface.Waterdrive reservoirs can have bottomwater drive or edgewater drive. In a bottomwater-drive reservoir, water is located beneath the oil accumulation, while in an edgewater-drive reservoir, water is located only on the edges of the reservoir.
4407gasdrive, gravity drainage, hydrocarbon, recovery
4408None
4409None
4410--
4411well plan
44121.n. [Shale Gas]
4413The description of a proposed wellbore, including the shape, orientation, depth, completion, and evaluation. Well plans might be relatively simple for vertical wellbores. Directional or horizontal wellbores require more detailed planning about where to land the well and begin directional drilling, how long the directional or horizontal section should be, and how to evaluate and complete the well. Shale gas wells, many of which are horizontal wells, require highly detailed well plans to optimize production from reservoirs that are vertically and laterally heterogeneous.
4414None
4415None
4416None
4417--
4418wildcat
44191.n. [Drilling]
4420An exploration well. The significance of this type of well to the drilling crew and well planners is that by definition, little if anything about the subsurface geology is known with certainty, especially the pressure regime. This higher degree of uncertainty necessitates that the drilling crews be appropriately skilled, experienced and aware of what various well parameters are telling them about the formations they drill. The crews must operate top-quality equipment, especially the blowout preventers, since a kick could occur at virtually any time. If a wildcat is especially far from another wellbore, it may be described as a "rank wildcat."
4421blowout preventer, offset well, tight hole
4422None
4423None
4424--
4425wall cake
44261.n. [Drilling Fluids, Formation Evaluation]
4427The 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.
4428deflocculated mud, drilling fluid, dynamic filtration, filter-cake quality, filter-cake thickness, filtrate volume, openhole completion, relative filtrate volume, resin, static filtration
4429mudcake
4430None
4431--
4432water filled resistivity
44331.n. [Formation Evaluation]
4434The resistivity of a sample completely filled with water. Called Ro, it is used in contrast to the resistivity of a sample only partially filled with water, Rt. The ratio Rt / Ro is called the resistivity index, I.
4435quicklook, true resistivity
4436None
4437None
4438--
4439well potential
44401.n. [Well Testing]
4441The flow rate at which a well is theoretically capable of producing. This is usually defined by a mathematical formula related to Darcy's law, often at maximum theoretical pressure drawdown. These theoretical rates were, and still are to some extent, used to set the production quota for an individual well in prorated or unitized production situations.
4442prorated well, unitized production
4443None
4444None
4445--
4446wing valve
44471.n. [Well Completions]
4448A valve located on the side of a Christmas tree or temporary surface flow equipment, such as may be used for a drillstem test. Two wing valves are generally fitted to a Christmas tree. A flowing wing valve is used to control and isolate production, and the kill wing valve fitted on the opposite side of the Christmas tree is available for treatment or well-control purposes. The term wing valve typically is used when referring to the flowing wing.
4449None
4450None
4451None
4452--
4453wall loss
44541.n. [Production Logging]
4455The loss of material on the inside or outside of a casing or tubing due to corrosion. Monitoring wall loss in situ helps determine when the pipe may be at risk for leaking or failure. Wall loss is determined by comparing casing or tubing thickness measured by electromagnetic, acoustic resonance or mechanical methods with either an earlier measurement or an assumed value.
4456casing-inspection log, electromagnetic thickness
4457metal loss
4458Antonyms:metal gain
4459--
4460waterflood
44611.n. [Well Completions, Enhanced Oil Recovery]
4462A method of secondary recovery in which water is injected into the reservoir formation to displace residual oil. The water from injection wells physically sweeps the displaced oil to adjacent production wells. Potential problems associated with waterflood techniques include inefficient recovery due to variable permeability, or similar conditions affecting fluid transport within the reservoir, and early water breakthrough that may cause production and surface processing problems.
4463hot waterflooding, injection well, low-salinity waterflooding, residual oil, secondary recovery
4464None
4465None
4466--
4467well servicing
44681.n. [Well Workover and Intervention]
4469The maintenance procedures performed on an oil or gas well after the well has been completed and production from the reservoir has begun. Well service activities are generally conducted to maintain or enhance the well productivity, although some slickline and coiled tubing applications are performed to assess or monitor the performance of the well or reservoir.Slickline, coiled tubing, snubbing and workover rigs or rod units are routinely used in well service activities.
4470None
4471None
4472None
4473--
4474wiper plug
44751.n. [Drilling]
4476Another term for cementing plug, a rubber plug used to separate thecementslurryfrom 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 thecasingprior to cementing. A diaphragm in the plug body ruptures to allow the cement slurry to pass through after the plug reaches thelanding 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 pumppressure.
4477None
4478cementing plug
4479None
4480--
4481wall sticking
44821.n. [Drilling]
4483Also known as differential sticking, a condition whereby the drillstring cannot be moved (rotated or reciprocated) along the axis of the wellbore. Differential sticking typically occurs when high-contact forces caused by low reservoir pressures, high wellbore pressures, or both, are exerted over a sufficiently large area of the drillstring. Differential sticking is, for most drilling organizations, the greatest drilling problem worldwide in terms of time and financial cost. It is important to note that the sticking force is a product of the differential pressure between the wellbore and the reservoir and the area that the differential pressure is acting upon. This means that a relatively low differential pressure (delta p) applied over a large working area can be just as effective in sticking the pipe as can a high differential pressure applied over a small area.
4484low-colloid oil mud, mechanical sticking, overbalance, pill, reservoir pressure, saltwater flow, stuck pipe
4485differential sticking
4486None
4487--
4488wall sticking
44892.n. [Drilling Fluids]
4490A situation in which the drilling assembly (pipe, drill collars and bottomhole assembly) is stuck in filter cake that was previously deposited on a permeable zone. The pipe is held in the cake by a difference in pressures between the hydrostatic pressure of the mud and the pore pressure in the permeable zone. The force required to pull the pipe free can exceed the strength of the pipe. Methods used to get the pipe free, in addition to pulling and torquing the pipe, include: (1) lowering hydrostatic pressure in the wellbore, (2) placing a spotting fluid next to the stuck zone and (3) applying shock force just above the stuck point by mechanical jarring, or (4) all the above. The most common approach, however, to getting free is to place a spot of oil, oil-base mud, or special spotting fluid.
4491filter cake, spotting fluid
4492differential sticking
4493None
4494--
4495waterflooding
44961.n. [Enhanced Oil Recovery, Well Completions]
4497A method of secondaryrecoveryin which water is injected into thereservoirformationto displace residual oil. The water from injection wells physically sweeps the displaced oil to adjacentproduction wells. Potential problems associated with waterflood techniques include inefficient recovery due to variablepermeability, or similar conditions affecting fluid transport within the reservoir, and early water breakthroughthat may cause production and surface processing problems.
4498hot waterflooding, injection well, low-salinity waterflooding, residual oil, secondary recovery
4499None
4500None
4501--
4502well shoot
45031.n. [Geophysics]
4504A type ofborehole seismic datadesigned to measure the seismictraveltimefrom the surface to a known depth. P-wavevelocityof the formations encountered in a wellbore can be measured directly by lowering ageophoneto eachformationof interest, sending out a source of energy from the surface of the Earth, and recording the resultantsignal. The data can then be correlated to surface seismic data by correcting thesonic logand generating asyntheticseismogramto confirm or modify seismic interpretations. It differs from avertical seismic profilein the number and density ofreceiverdepths 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.
4505depth conversion, drift, first break, one-dimensional seismic data, one-way time
4506check-shot survey
4507None
4508--
4509wiper trip
45101.n. [Drilling]
4511An abbreviated recovery and replacement of the drillstring in the wellbore that usually includes the bit and bottomhole assembly passing by all of the openhole, or at least all of the openhole that is thought to be potentially troublesome. This trip varies from the short trip or the round trip only in its function and length. Wiper trips are commonly used when a particular zone is troublesome or if hole-cleaning efficiency is questionable.
4512None
4513None
4514None
4515--
4516walthers law
45171.n. [Reservoir Characterization]
4518A law stating that lithologies that conformably overlie one another must have accumulated in adjacent depositional environments. Exceptions occur where there are erosional breaks. This law allows for transformations from the vertical data to a horizontal set and is often used when a vertical sequence of facies has been identified and characterized (for example, with Markov chain analysis) to estimate the horizontal depositional pattern.
4519None
4520None
4521None
4522--
4523water flow log
45241.n. [Production Logging]
4525A record of the velocity and direction of water flowing in and around a borehole based on oxygen activation. The log may also include estimates of the flow volume and the distance from tool to flowing water. Water, and occasionally carbon dioxide, is the only source of moving oxygen in and around the borehole. Hence, water flow can be detected by oxygen activation, which, being a nuclear technique, is sensitive to flow inside and outside the casing. The measurement is sensitive to small flows, and can be configured to measure upward or downward flow. It is particularly useful as a leak and channel detector, to identify locations of water entry or exit and as a measurement of water velocity in multiphase flow. Logs may be continuous, but the most accurate measurements are made with the tool stationary.Although first tried in the 1960s, the log was not fully studied and implemented until the late 1970s with a purpose-built experimental tool. Standard pulsed-neutron spectroscopy tools were modified to record the log in the 1980s.
4526activation log, impulse activation, phase-velocity log, production log, pulsed neutron spectroscopy measurement
4527None
4528None
4529--
4530well stimulation
45311.n. [Enhanced Oil Recovery, Well Workover and Intervention, Well Completions, Shale Gas]
4532A treatment performed to restore or enhance the productivity of a well. Stimulation treatments fall into two main groups,hydraulic fracturingtreatments andmatrixtreatments. Fracturing treatments are performed above thefracturepressureof thereservoirformationand create a highly conductive flow path between the reservoir and the wellbore. Matrix treatments are performed below the reservoir fracture pressure and generally are designed to restore the naturalpermeabilityof the reservoir followingdamageto the near-wellbore area. Stimulation inshalegas reservoirs typically takes the form of hydraulic fracturing treatments.
4533matrix stimulation
4534stimulation
4535None
4536--
4537wire clamp
45381.n. [Well Workover and Intervention]
4539A safety device attached to the slickline at surface between the hay pulley and stuffing-box pulley. The wire clamp generally is applied when the slickline is to be stationary for a period of time. This prevents the tool string from dropping down the wellbore if the winch unit fails or the slickline becomes damaged at surface.
4540None
4541None
4542None
4543--
4544wash out
45451.n. [Drilling]
4546An enlarged region of a wellbore. A washout in an openhole section is larger than the original hole size or size of the drill bit. Washout enlargement can be caused by excessive bit jet velocity, soft or unconsolidated formations, in-situ rock stresses, mechanical damage by BHA components, chemical attack and swelling or weakening of shale as it contacts fresh water. Generally speaking, washouts become more severe with time. Appropriate mud types, mud additives and increased mud density can minimize washouts.
4547None
4548None
4549washout
4550--
4551water wet
45521.adj. [Well Completions, Enhanced Oil Recovery]
4553Pertaining to the adhesion of a liquid to the surface of a solid. In water-wet conditions, a thin film of water coats the surface of the formation matrix, a condition that is desirable for efficient oil transport. Treatments that change the wettability of the formation from water-wet to oil-wet can significantly impair productivity.
4554None
4555None
4556None
4557--
4558water wet
45592.adj. [Formation Evaluation]
4560Describing the preference of a solid to be in contact with a water phase rather than an oil or gas phase. Water-wet rocks preferentially imbibe water. Generally, sandstones and carbonates are water-wet before contact with crude oil, but may be altered by components of the crude oil to become oil-wet. Certain minerals, as well as different crystallographic faces of the same mineral, may be variably prone to being oil- or water-wet.
4561drainage, fluid contact, imbibition, wettability
4562None
4563None
4564--
4565wellbore
45661.n. [Drilling]
4567The drilled hole or borehole, 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.
4568inside diameter, openhole
4569borehole
4570None
4571--
4572wire wrapped screen
45731.n. [Well Completions]
4574A type of screen used insand controlapplications to support thegravel pack. The profiled wire is wrapped and welded in place on aperforated liner. Screens are available in a range of sizes and specifications, includingoutside diameter, material type and the geometry and dimension of the screen slots. The space between each wire wrap must be small enough to retain the gravel placed behind the screen, yet minimize any restriction toproduction.
4575None
4576screen
4577None
4578--
4579washout
45801.n. [Drilling]
4581An enlarged region of a wellbore. A washout in an openhole section is larger than the original hole size or size of the drill bit. Washout enlargement can be caused by excessive bit jet velocity, soft or unconsolidated formations, in-situ rock stresses, mechanical damage by BHA components, chemical attack and swelling or weakening of shale as it contacts fresh water. Generally speaking, washouts become more severe with time. Appropriate mud types, mud additives and increased mud density can minimize washouts.
4582drill bit, float shoe, guide shoe, jet velocity
4583None
4584None
4585--
4586washout
45872.n. [Drilling]
4588A hole in a pressure-containing component caused by erosion. A washout is relatively common where a high-velocity stream of dry gas carries abrasive sand. The severity generally decreases with sand content, velocity and liquid content.
4589None
4590None
4591None
4592--
4593waveform
45941.n. [Geophysics]
4595The shape of a wave, typically shown as a graph of amplitude (or other quantity of interest) versus time.
4596correlation, crosscorrelation, fast Fourier transform, signature, signature deconvolution
4597None
4598None
4599--
4600wellbore diagram
46011.n. [Well Completions]
4602A schematic diagram that identifies the main completion components installed in a wellbore. The information included in the wellbore diagram relates to the principal dimensions of the components and the depth at which the components are located. A current wellbore diagram should be available for any well intervention operation to enable engineers and equipment operators to select the most appropriate equipment and prepare operating procedures that are compatible with any downhole restrictions.
4603None
4604None
4605None
4606--
4607wireline formation test
46081.n. [Well Testing]
4609Test taken with a wireline formation tester. The wireline formation pressure measurement is acquired by inserting a probe into the borehole wall and performing a minidrawdown and buildup by withdrawing a small amount of formation fluid and then waiting for the pressure to build up to the formation pore pressure. This measurement can provide formation pressures along the borehole, thereby giving a measure of pressure with depth or along a horizontal borehole. The trend in formation pressure with depth provides a measure of the formation-fluid density, and a change in this trend may indicate a fluid contact. Abrupt changes in formation pressure measurements with depth indicate differential pressure depletion and demonstrate barriers to vertical flow. Lateral variation in formation pressure measurements along a horizontal well or in multiple vertical wells indicate reservoir heterogeneity.
4610fluid contact, formation fluid, formation pressure
4611None
4612None
4613--
4614washover pipe
46151.n. [Drilling]
4616In fishing operations, a large-diameter pipe fitted with an internal grappling device and tungsten carbide cutting surfaces on the bottom. The washover pipe can be lowered over a fish in the wellbore and to latch onto and retrieve the fish. Since the washover pipe is relatively thin-walled and large in diameter, and may be prone to sticking itself, the washover operation is usually reserved as a measure of last resort before abandoning the fish altogether.
4617fish, fishing tool
4618None
4619None
4620--
4621wavelet
46221.n. [Geophysics]
4623A one-dimensional pulse, usually the basic response from a single reflector. Its key attributes are its amplitude, frequency and phase. The wavelet originates as a packet of energy from the source point, having a specific origin in time, and is returned to the receivers as a series of events distributed in time and energy. The distribution is a function of velocity and density changes in the subsurface and the relative position of the source and receiver. The energy that returns cannot exceed what was input, so the energy in any received wavelet decays with time as more partitioning takes place at interfaces. Wavelets also decay due to the loss of energy as heat during propagation. This is more extensive at high frequency, so wavelets tend to contain less high-frequency energy relative to low frequencies at longer traveltimes. Some wavelets are known by their shape and spectral content, such as the Ricker wavelet.
4624convolution, embedded wavelet, peak, polarity, polarity standard, resolution, Ricker wavelet, spectral, synthetic seismogram, trough, wavelet extraction, zero-phase
4625None
4626None
4627--
4628wellbore storage effects
46291.n. [Well Testing]
4630Distortions in thereservoirresponse due to wellbore storage. The characteristic trends are an early unit slope trend withpressurechange and the derivative overlain on the log-log plot, followed by a "hump" in the pressure derivative that gradually disappears as reservoir trends become recognizable. Complex behavior in the wellbore, such as wellbore phasedistribution, can result in a more complex transient trend. A crucial part of the transient analysis is to distinguish the effects of wellbore storage from the interpretable reservoir response.
4631None
4632None
4633None
4634--
4635wireline formation tester
46361.n. [Well Testing]
4637A tool run on an electric logging cable that pushes a probe into the formation, which then allows production into a small closed chamber. The tool is primarily used to obtain formation pressures at chosen locations in an interval, and, with an accurate quartz gauge, permeability estimates may be obtained. Modern variations on this tool have been developed to acquire formation-fluid samples.
4638formation pressure, wireline
4639fluid tester
4640None
4641--
4642washover shoe
46431.n. [Well Workover and Intervention]
4644A 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.
4645None
4646mill shoe
4647None
4648--
4649wavelet extraction
46501.n. [Geophysics]
4651A step in seismic processing to determine the shape of the wavelet, also known as the embedded wavelet, that would be produced by a wave train impinging upon an interface with a positive reflection coefficient. Wavelets may also be extracted by using a model for the reflections in a seismic trace, such as a synthetic seismogram. A wavelet is generated by deconvolving the trace with the set of reflection coefficients of the synthetic seismogram, a process also known as deterministic wavelet extraction. Wavelets may be extracted without a model for the reflections by generating a power spectrum of the data. By making certain assumptions, such as that the power spectrum contains information about the wavelet (and not the geology) and that the wavelet is of a certain phase (minimum, zero), a wavelet may be generated. This is also called statistical wavelet extraction. A particular processing approach to establishing the embedded wavelet is to compare the processed seismic response with the response measured by a vertical seismic profile (VSP) or generated synthetically through a synthetic seismogram in which the embedded wavelet is known. The wavelet can also be extracted through the autocorrelation of the seismic trace, in which case the phase of the wavelet has to be assumed.
4652synthetic seismogram, vertical seismic profile
4653None
4654None
4655--
4656wellbore storage effects
46571.n. [Well Testing]
4658Distortions in the reservoir response due to wellbore storage. The characteristic trends are an early unit slope trend with pressure change and the derivative overlain on the log-log plot, followed by a "hump" in the pressure derivative that gradually disappears as reservoir trends become recognizable. Complex behavior in the wellbore, such as wellbore phase distribution, can result in a more complex transient trend. A crucial part of the transient analysis is to distinguish the effects of wellbore storage from the interpretable reservoir response.
4659None
4660None
4661None
4662--
4663wireline log
46641.n. [Reservoir Characterization, Formation Evaluation, Drilling]
4665A continuous measurement offormationproperties with electrically powered instruments to infer properties and make decisions about drilling andproductionoperations. The record of the measurements, typically a long strip of paper, is also called a log. Measurements include electrical properties (resistivity andconductivityat various frequencies),sonicproperties, active and passive nuclear measurements, dimensional measurements of the wellbore,formation fluidsampling,formation pressuremeasurement, wireline-conveyedsidewallcoring tools, and others. For wireline measurements, theloggingtool (or sonde) is lowered into the open wellbore on a multiple conductor, contra-helically armored wireline cable. Once the tool string (link to ID 2964) has reached the bottom of the interval of interest, measurements are taken on the way out of the wellbore. This is done in an attempt to maintain tension on thecable(which stretches) as constant as possible fordepth correlationpurposes. (The exception to this practice is in certain hostile environments in which the tool electronics might not survive the downhole temperatures for long enough to allow the tool to be lowered to the bottom of the hole and measurements to be recorded while pulling the tool up the hole. In this case, "down log" measurements might be conducted on the way into the well, and repeated on the way out if possible.) Most wireline measurements are recorded continuously while the sonde is moving. Certain fluid sampling and pressure-measuring tools require that the sonde be stopped, increasing the chance that the sonde or the cable might become stuck.Logging while drilling(LWD) tools take measurements in much the same way as wireline-logging tools, except that the measurements are taken by a self-contained tool near the bottom of thebottomhole assemblyand are recorded downward (as the well is deepened) rather than upward from the bottom of the hole.
4666hostile environment, log
4667None
4668None
4669--
4670wastewater cleanup
46711.n. [Drilling Fluids]
4672A process in which dirty water is stripped of its solids and made suitable for recycling into a mud system or disposal into sewer systems or other places. In closed mud systems, water containing colloidal matter can be cleaned and recycled. Efficient agglomeration of colloidal solids is achieved by pH adjustment, small additions of alum or a high-molecular-weight polymer. Agglomerated solids are then filtered or centrifuged from the fluid.
4673acrylamide polymer, acrylamide-acrylate polymer, acrylate polymer, clear-water drilling, closed mud system, colloidal solids, filter medium, reserve-mud pit, vinyl acetate-maleic anhydride copolymer, water clarification
4674None
4675None
4676--
4677weathered layer
46781.n. [Geology, Geophysics]
4679A near-surface, possibly unconsolidated layer of low seismic velocity. The base of the weathered layer commonly coincides with the water table and a sharp increase in seismic velocity. The weathered layer typically has air-filled pores.
4680pore, static correction, weathering, weathering correction
4681None
4682None
4683--
4684wellhead
46851.n. [Drilling]
4686The system of spools, valves and assorted adapters that provide pressure control of a production well.
4687casing string, casinghead, day rate, Texas deck
4688None
4689None
4690--
4691wellhead
46922.n. [Well Completions]
4693The surface termination of a wellbore that incorporates facilities for installing casing hangers during the well construction phase. The wellhead also incorporates a means of hanging the production tubing and installing the Christmas tree and surface flow-control facilities in preparation for the production phase of the well.
4694casing hanger
4695None
4696None
4697--
4698wireline retrievable safety valve wrsv
46991.n. [Well Completions]
4700A type of safety valve in which the principal components can berunand retrieved bywirelineorslickline. The valve assembly is landed in a portednipplethat is equipped with acontrol lineconnected to the surface control system. This configuration enables the safety valve to be easily retrieved for repair or maintenance, but the resulting internal bore of the WRSV must be relatively small.
4701None
4702None
4703None
4704--
4705water block
47061.n. [Well Completions]
4707A condition caused by an increase in water saturation in the near-wellbore area. Water block typically forms during the drilling phase of a well, when the near-wellbore area is exposed to a relatively high volume of filtrate from the drilling fluid. The increased presence of water causes fine clay crystals that may be present in the formation, such as illite, to swell and cause a reduction in permeability. Water-block treatments typically use surfactants to reduce the surface tension between the oil and water, helping to displace the water from the near-wellbore area.
4708surfactant
4709None
4710None
4711--
4712water block
47132.n. [Well Workover and Intervention]
4714A production impairment that can occur when the formation matrix in the near-wellbore area becomes water-saturated, thereby decreasing the relative permeability to hydrocarbons. Water block may result from the invasion of water-base drilling or completion fluids or from fingering or coning of formation waters.The most extreme cases of water block occur in low-pressure, low-permeability gas formations, where alcoholic acid systems are recommended because they promote water vaporization in the produced gas.Alcoholic acid formulations are a mixture of acid and alcohol. The acids normally employed are usually either hydrochloric acid [HCl], mud acid [HF-HCl or HF-organic acid (formic or acetic)]. The alcohol is either methyl or isopropyl. Alcohol lowers the surface tension of acid and allows deeper penetration of the acid into the matrix of the rock. Alcohol is somewhat soluble in both acid and water, and penetration of low-surface-tension volatile alcohol into a water block will aid in its removal.
4715completion fluid, damage, water saturation, water-base drilling fluid
4716None
4717None
4718--
4719weevil
47201.n. [Drilling]
4721A new, completely inexperienced member of the drilling crew. Such a crewmember is stereotyped as prone to making mistakes and being injured, and typically endures pranks played on him by the drilling crew. While the terms weevil and its close cousin, worm, are used widely, they are labels of inexperience, rather than derogatory terms.
4722None
4723worm
4724None
4725--
4726well interference testing
47271.n. [Well Testing]
4728Thepressurevariation with time recorded in observation wells resulting from changes in rates in productionor injection wells. In commercially viable reservoirs, it usually takes considerable time for production at one well to measurably affect the pressure at an adjacent well. Consequently, interference testing has been uncommon because of the cost and the difficulty in maintaining fixed flow rates over an extended time period. With the increasing number of permanent gauge installations, interference testing may become more common than in the past.
4729None
4730interference testing
4731None
4732--
4733wireline retrievable safety valve wrsv
47341.n. [Well Completions]
4735A type of safety valve in which the principal components can be run and retrieved by wireline or slickline. The valve assembly is landed in a ported nipple that is equipped with a control line connected to the surface control system. This configuration enables the safety valve to be easily retrieved for repair or maintenance, but the resulting internal bore of the WRSV must be relatively small.
4736None
4737None
4738None
4739--
4740water cut meter
47411.n. [Production Logging]
4742A device for determining the waterholdupin aproducing wellby measuring the capacitance or impedance of the fluid. The term is a misnomer becausewater cutis not the same as water holdup except in the unlikely case where all phases flow at the samevelocity. Since hydrocarbons travel faster than water in aproductionwell, the water holdup is larger than the water cut. However, the water-cut meter was often combined with aflowmeterso that the water cut could be estimated by combining the two measurements.
4743capacitance log, dielectric constant, diverter flowmeter, holdup log, packer flowmeter, production log
4744None
4745None
4746--
4747weight
47481.n. [Drilling Fluids]
4749Referring to mud weight, the mass per unit volume of adrilling fluid, synonymous with mud density. Weight is reported in lbm/gal (also known asppg), kg/m3or g/cm3(also calledspecific gravityor SG), lb/ft3or in hydrostatic gradient, lb/in2/ft (psi/ft) or pptf (psi/1000 ft). Mud weight controlshydrostatic pressurein a wellbore and prevents unwanted flow into the well. The weight of the mud also prevents collapse ofcasingand theopenhole. Excessive mud weight can causelost circulationby propagating, and then filling, fractures in therock. Mud weight (density) test procedures using a mud balance have been standardized and published by the API.
4750equivalent circulating density, high-gravity solids, mud, mud balance, pressurized mud balance, PVT, recorded data, sag, slug, weighting material
4751mud density
4752None
4753--
4754wentworth scale
47551.n. [Geology]
4756Another name for the Udden-Wentworth scale, a grade scale for classifying the diameters of sediments. Particles larger than 64 mm in diameter are classified as cobbles. Smaller particles are pebbles, granules,sandandsilt. Those smaller than 0.0039 mm areclay. Several other grain size scales are in use, but the Udden-Wentworth scale (commonly called the Wentworth scale) is the one that is most frequently used ingeology.
4757arenaceous, argillaceous, sediment, sorting
4758Udden-Wentworth scale
4759None
4760--
4761wire wrapped screen
47621.n. [Well Completions]
4763A type of screen used insand controlapplications to support thegravel pack. To form the screen, a profiled wire is wrapped and welded in place on aperforated liner. Screens are available in a range of sizes and specifications, includingoutside diameter, material type and the geometry and dimension of the screen slots. The space between each wire wrap must be small enough to retain the gravel placed behind the screen, yet minimize any restriction toproduction.
4764None
4765screen
4766None
4767--
4768water drive
47691.n. [Well Completions]
4770A reservoir-drive mechanism whereby the oil is driven through the reservoir by an active aquifer. As the reservoir depletes, the water moving in from the aquifer below displaces the oil until the aquifer energy is expended or the well eventually produces too much water to be viable.
4771None
4772None
4773waterdrive
4774--
4775water drive
47762.n. [Enhanced Oil Recovery]
4777A primary recovery mechanism in which the pressure from free water is sufficient to move hydrocarbons out of the reservoir, into the wellbore and up to surface.Waterdrive reservoirs can have bottomwater drive or edgewater drive. In a bottomwater-drive reservoir, water is located beneath the oil accumulation, while in an edgewater-drive reservoir, water is located only on the edges of the reservoir.
4778None
4779waterdrive
4780None
4781--
4782weight indicator
47831.n. [Drilling]
4784One of the instruments that the driller uses to monitor and improve the operating efficiencies of the drilling operation. The actual measurement of weight is made with a hydraulic gauge attached to the dead line of the drilling line. As tension increases in the drilling line, more hydraulic fluid is forced through the instrument, turning the hands of the indicator. The weight that is measured includes everything exerting tension on the wire rope, including the traveling blocks and cable itself. Hence, to have an accurate weight measurement of the drillstring, the driller must first make a zero offset adjustment to account for the traveling blocks and items other than the drillstring. Then the indicated weight will represent the drillstring (drillpipe and bottomhole assembly). However, the driller is only nominally interested in this weight for most operations. The weight of interest is the weight applied to the bit on the bottom of the hole. The driller could simply take the rotating and hanging off bottom weight, say 300,000 pounds [136,200 kg], and subtract from that the amount of rotating on bottom weight, say 250,000 pounds [113,500 kg], to get a bit weight of 50,000 pounds [22,700 kg]. However, most rigs are equipped with a weight indicator that has a second indicator dial that can be set to read zero ("zeroed") with the drillstring hanging free, and works backwards from the main indicator dial. After proper zeroing, any weight set on bottom (that takes weight away from the main dial), has the effect of adding weight to this secondary dial, so that the driller can read weight on bit directly from the dial.
4785drill collar, traveling block
4786None
4787None
4788--
4789weight indicator
47902.n. [Well Workover and Intervention]
4791A device or system used to measure, display and record the weight of a tubing string, slickline string or coiled tubing string in the wellbore. The weight indicator is the principal means by which the equipment operator monitors the function of downhole tools and equipment. Factors such as fluid density, which affects buoyancy and wellhead pressure, also impact the forces measured at surface. These factors can influence the apparent string weight significantly.
4792None
4793None
4794None
4795--
4796wet clay porosity
47971.n. [Formation Evaluation]
4798The proportion of a wet clay that is clay-bound water. A formation that has 100% clay would have a porosity equal to the wet-clay porosity (WCLP), all of it being clay-bound water, and a volume of dry clay equal to (1 - WCLP). The concept is used to relate the volume of clay-bound water, CBW, to the volume of dry clay, Vdcl, in an actual rock, since the ratio of the two is the same and equal to:		CBW / Vdcl = WCLP / (1 - WCLP).
4799dual water, electrical double layer
4800None
4801None
4802--
4803woc
48041.vb. [Drilling]
4805To suspend drilling operations while allowing cement slurries to solidify, harden and develop compressive strength. The drilling crew usually uses this time to catch up on maintenance items, to rig down one BOP and rig up another one for the new casing, to get tools and materials ready for the next hole section, and other non-drilling tasks. The WOC time ranges from a few hours to several days, depending on the difficulty and criticality of the cement job in question. WOC time allows cement to develop strength, and avert development of small cracks and other fluid pathways in the cement that might impair zonal isolation.
4806None
4807None
4808wait on cement
4809--
4810water filled resistivity
48111.n. [Formation Evaluation]
4812Theresistivityof a sample completely filled with water. Called Ro, it is used in contrast to the resistivity of a sample only partially filled with water, Rt. The ratio Rt/ Rois called theresistivity index, I.
4813quicklook, true resistivity
4814None
4815None
4816--
4817weight material
48181.n. [Drilling Fluids]
4819Also known as weighting material, a high-specific gravity and finely divided solid material used to increase density of adrilling fluid. (Dissolved salts that increase fluid density, such ascalcium bromidein brines, are not called weighting materials.)Bariteis the most common, with minimum specific gravity of 4.20 g/cm3.Hematiteis a more dense material, with minimum specific gravity of 5.05 g/cm3, perAPIandISOspecifications. Calcium carbonate, specific gravity 2.7 to 2.8, is considered weighting material but is used more for itsacid solubilitythan for density.Siderite, specific gravity around 3.8, has been used to densify mud, but can cause problems by dissolving into the mud at highpH.Ilmenite, specific gravity of 4.6 has been used in drilling fluid andcement. Only barite and hematite have API/ISO standards.
4820Brookfield viscometer, gel strength, high-gravity solids, mud additive, mud weight, slug, specific gravity
4821weighting agent, weighting material
4822None
4823--
4824wet combustion
48251.n. [Enhanced Oil Recovery, Heavy Oil]
4826An in situ combustion technique in which water is injected simultaneously or alternately with air into a 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 the oil bank ahead. Because of this additional energy, the oil displacement is 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 oil viscosity.Wet combustion is also called in situ steam generation or a combination of forward combustion and waterflooding, which is abbreviated as COFCAW.
4827dry combustion, dry forward combustion, reverse combustion
4828None
4829COFCAW
4830--
4831workover fluid
48321.n. [Well Workover and Intervention]
4833A well-control fluid, typically a brine, that is used during workover operations. Since the wellbore is in contact with the reservoir during most workover operations, workover fluids should be clean and chemically compatible with the reservoir fluids and formation matrix.
4834None
4835None
4836None
4837--
4838water flood
48391.n. [Well Completions, Enhanced Oil Recovery]
4840A method of secondary recovery in which water is injected into the reservoir formation to displace residual oil. The water from injection wells physically sweeps the displaced oil to adjacent production wells. Potential problems associated with waterflood techniques include inefficient recovery due to variable permeability, or similar conditions affecting fluid transport within the reservoir, and early water breakthrough that may cause production and surface processing problems
4841None
4842None
4843waterflood
4844--
4845weighted mud
48461.n. [Drilling Fluids]
4847A mud that contains commercial weighting material such as barite or hematite. The economic difference in weighted and unweighted muds is the cost of replacing weighting material according to the solids control practices used. Solids control techniques, such as dilution or hydrocycloning, that can be economical in unweighted muds are not necessarily economical for weighted muds, although centrifugation (incorrectly called "barite recovery") is typically performed when using weighted muds to control mud viscosity.
4848centrifuge, native clay
4849None
4850Antonyms:unweighted mud
4851--
4852wet gas
48531.n. [Geology]
4854Natural gas that contains less methane (typically less than 85% methane) and more ethane and other more complex hydrocarbons.
4855condensate, dry gas, fluid contact, hydrocarbon, natural gas
4856None
4857Antonyms:dry gas
4858--
4859wet gas
48602.n. [Production Facilities]
4861Natural gas that contains water.
4862dehydrate
4863None
4864None
4865--
4866wet gas
48673.n. [Production Testing]
4868Natural gas containing significant heavy hydrocarbons. Propane, butane and other liquid hydrocarbons can be liquefied.
4869hydrocarbon
4870None
4871None
4872--
4873worm
48741.n. [Drilling]
4875A new, completely inexperienced member of thedrilling crew. Such a crewmember is stereotyped as prone to making mistakes and being injured, and typically endures pranks played on him by the drilling crew. While the terms weevil and its close cousin, worm, are used widely, they are labels of inexperience, rather than derogatory terms.
4876None
4877weevil
4878None
4879--
4880water flow log
48811.n. [Production Logging]
4882A record of thevelocityand direction of water flowing in and around aboreholebased onoxygen activation. The log may also include estimates of the flow volume and the distance from tool to flowing water. Water, and occasionallycarbon dioxide, is the only source of moving oxygen in and around the borehole. Hence, water flow can be detected by oxygen activation, which, being a nuclear technique, is sensitive to flow inside and outside thecasing. The measurement is sensitive to small flows, and can be configured to measure upward or downward flow. It is particularly useful as a leak and channel detector, to identify locations of water entry or exit and as a measurement of water velocity inmultiphase flow. Logs may be continuous, but the most accurate measurements are made with the tool stationary.Although first tried in the 1960s, the log was not fully studied and implemented until the late 1970s with a purpose-built experimental tool. Standard pulsed-neutron spectroscopy tools were modified to record the log in the 1980s.
4883activation log, impulse activation, phase-velocity log, production log, pulsed neutron spectroscopy measurement
4884None
4885None
4886--
4887weighting agent
48881.n. [Drilling Fluids]
4889Also known as weighting material, a high-specific gravity and finely divided solid material used to increase density of adrilling fluid. (Dissolved salts that increase fluid density, such ascalcium bromidein brines, are not called weighting materials.)Bariteis the most common, with minimum specific gravity of 4.20 g/cm3.Hematiteis a more dense material, with minimum specific gravity of 5.05 g/cm3, perAPIandISOspecifications. Calcium carbonate, specific gravity 2.7 to 2.8, is considered weighting material but is used more for itsacid solubilitythan for density.Siderite, specific gravity around 3.8, has been used to densify mud, but can cause problems by dissolving into the mud at highpH.Ilmenite, specific gravity of 4.6 has been used in drilling fluid andcement. Only barite and hematite have API/ISO standards.
4890weighting material
4891None
4892None
4893--
4894wet clay porosity
48951.n. [Formation Evaluation]
4896The proportion of a wet clay that is clay-bound water. A formation that has 100% clay would have a porosity equal to the wet-clay porosity (WCLP), all of it being clay-bound water, and a volume of dry clay equal to (1 - WCLP). The concept is used to relate the volume of clay-bound water, CBW, to the volume of dry clay, Vdcl, in an actual rock, since the ratio of the two is the same and equal to:		CBW / Vdcl = WCLP / (1 - WCLP).
4897dual water, electrical double layer
4898None
4899None
4900--
4901wormhole
49021.n. [Enhanced Oil Recovery]
4903A large, empty channel that can penetrate several feet into the formation, caused by the nonuniform dissolution of limestone or dolomite by hydrochloric acid [HCl].Wormholes are created during matrix stimulation or acid fracturing of carbonate formations. The purpose of matrix stimulation is to create highly conductive wormholes to bypass damage. However, in fracture acidizing, wormholing is a problem, since it is an unwanted diversion of the live acid from the hydraulic fracture system, which causes a reduction of the etched fracture length.
4904hydraulic fracturing
4905None
4906None
4907--
4908wormhole
49092.n. [Heavy Oil]
4910A high-porosity, high-permeability channel that develops when heavy oil is produced simultaneously with sand (during cold heavy oil production with sand, or CHOPS). Wormholes develop in a radial pattern away from the borehole and can extend 150 m [492 ft] from the borehole. The development of wormholes can cause reservoir pressure to fall below the bubblepoint, resulting in dissolved gas coming out of solution and forming foamy oil.
4911None
4912None
4913None
4914--
4915x ray diffraction
49161.n. [Formation Evaluation]
4917A technique for the semiquantitative mineralogical analysis of a sample of rock by measuring the diffraction peaks in X-rays diffracted by the sample. The position of the diffraction peaks is a measure of the distance between discrete crystallographic diffracting planes within minerals, while their intensity indicates the quantity of the mineral. The technique is only semiquantitative because the size and shape of the diffraction peak are strongly influenced by the geometry of the measurement, for example orientation of the minerals, and sample preparation. Fine particles such as clays must be separated from larger particles and measured separately if they are to be detected properly. To reduce errors associated with preferred orientation of minerals, samples are most commonly ground to a powder before analysis, a technique known as powder X-ray diffraction.
4918Fourier transform infrared spectroscopy
4919None
4920None
4921--
4922xylene
49231.n. [Drilling Fluids]
4924An aromatic hydrocarbon molecule containing a benzene ring with two methyl side chains, formula C6H4(CH3)2. Xylene is an excellent solvent, especially for aromatic solids such as asphaltic materials. It is used as a solvent and emulsion breaker in workover operations to clean up reservoirs. In drilling mud testing, a 50/50 xylene/isopropanol (IPA) mixture had been used to break oil-mud emulsions prior to titrations to measure alkalinity, chloride and calcium. However, the xylene mixture has been replaced by a single material, propylene glycol normal propyl ether (PNP), to break oil mud emulsions.
4925oil-emulsion mud
4926None
4927None
4928--
4929yield point
49301.n. [Geology]
4931The elastic limit, or the point at which a material can no longer deform elastically. When theelasticlimit is exceeded by an appliedstress, permanent deformation occurs.
4932elastic deformation, plastic
4933elastic limit
4934None
4935--
4936yield point
49372.n. [Drilling Fluids]
4938A parameter of the Bingham plastic model. YP is the yield stress extrapolated to a shear rate of zero. (Plastic viscosity, PV, is the other parameter of the Bingham-plastic model.) A Bingham plastic fluid plots as a straight line on a shear rate (x-axis) versus shear stress (y-axis) plot, in which YP is the zero-shear-rate intercept. (PV is the slope of the line.) YP is calculated from 300- and 600-rpm viscometer dial readings by subtracting PV from the 300-rpm dial reading. YP is used to evaluate the ability of a mud to lift cuttings out of the annulus. A high YP implies a non-Newtonian fluid, one that carries cuttings better than a fluid of similar density but lower YP. YP is lowered by adding deflocculant to a clay-based mud and increased by adding freshly dispersed clay or a flocculant, such as lime.
4939aggregation, apparent viscosity, clay-water interaction, deflocculated mud, direct-indicating viscometer, drill solids, gelled-up mud, mixed-metal hydroxide
4940None
4941YP
4942--
4943youngs modulus
49441.n. [Geophysics]
4945An elastic constant named after British physicist Thomas Young (1773 to 1829) that is the ratio of longitudinal stress to longitudinal strain and is symbolized by E. It can be expressed mathematically as follows:E = (F/A) / (ΔL/L),whereE = Young's modulusF = longitudinal forceA = areaF/A = longitudinal stressΔL = change in lengthL = original lengthΔL/L = longitudinal strain.
4946elastic constants
4947None
4948None
4949--
4950za effect
49511.n. [Formation Evaluation]
4952The ratio of the electron density to the bulk density. The electron density is equal to the bulk density multiplied by 2Z/A where Z is the average atomic number and A is the average atomic weight of the formation. The density log actually responds to electron density, whereas the desired measurement is the bulk density. Although for most rocks 2Z/A is close to 1, it is not practical to adjust 2Z/A for each formation. Instead the electron density is scaled to give the correct bulk density in limestone filled with fresh water. Then it is found that in the majority of sedimentary rocks, the log reads the bulk density within 1%. The main exceptions are halite, sylvite and low-pressure gas, because the 2Z/A of chlorine and hydrogen are not close to 1.
4953density measurement, photoelectric effect
4954None
4955None
4956--
4957zero offset vertical seismic profile
49581.n. [Geophysics]
4959A conventional vertical seismic profile in which the energy source is positioned directly above the receivers, typically very close to the wellbore.
4960None
4961VSP
4962None
4963--
4964zip collars
49651.n. [Drilling]
4966Drill collars (usually straight drill collars) that have been machined with a reduced diameter at the box (up) end so that they may be more easily handled with open-and-close elevators. The elevators close around the reduced-diameter section, latch securely, and a shoulder on the elevators prevents the larger diameter end of the collar from passing through the elevators, so the collars can be lifted. If zip grooves are not used on the collars, special lifting subs must be threaded into each stand of collars for lifting, which is time-consuming and less efficient than zip grooves. The primary drawback to zip grooves is that they may reduce the life of the collar by putting an effective limit on how many times the collar threads may be recut.
4967drill collar, elevator, lifting sub
4968None
4969None
4970--
4971zip groove
49721.n. [Drilling]
4973A reduced-diameter section that has been machined at thebox(up) end of a drill collar (usually a straight drill collar) so that the collar may be more easily handled with open-and-close elevators. The elevators close around the reduced-diameter section, latch securely, and a shoulder on the elevators prevents the larger diameter end of the collarfrom passing through the elevators, so the collars can be lifted. If zip grooves are not used on the collars, special lifting subs must be threaded into eachstandof collars for lifting, which is time-consuming and less efficient than zip grooves. The primary drawback to zip grooves is that they may reduce the life of the collar by putting an effective limit on how many times the collar threads may be recut.
4974zip collars
4975None
4976None
4977--
4978zero offset vertical seismic profile
49791.n. [Geophysics]
4980A conventionalvertical seismic profilein which the energysourceis positioned directly above the receivers, typically very close to the wellbore.
4981None
4982VSP
4983None
4984--