Oil and gas terminology · MLC-0103

Oil and gas terms: W (117)

• Wadati-Benioff zoneA planar zone of seismicity that dips into the Earth's mantle beneath an oceanic trench and volcanic arc. It...
• Wait on cement (WOC)A period of time during drilling operations when work is suspended to allow freshly placed cement to cure and...
• Wait timeThe delay in NMR logging between the end of one CPMG echo train and the start of the next, during which the...
• Walk-above vertical seismic profile (VSP)A type of vertical seismic profile (VSP) where seismic sources are positioned directly above a downhole...
• Walkaway vertical seismic profile (VSP)A type of seismic survey where a seismic source is moved to progressively greater offsets along a line on the...
• Wall cakeA layer of drilling fluid solids deposited on the wellbore wall during drilling, formed by the filtration of...
• Wall lossThe reduction in the thickness of the casing or tubing wall due to corrosion, erosion, or mechanical wear...
• Wall stickingA condition where the drill string becomes immovably lodged against the wall of the wellbore due to...
• Walsh-Hadamard transformA non-sinusoidal, orthogonal transform that decomposes a signal into a set of Walsh functions, which are...
• Walther's lawA fundamental principle in stratigraphy stating that in a conformable vertical succession of facies, those...
• Wash pipeA relatively short, large-diameter pipe that is run into a well to circulate fluid over the outside of a...
• WashoutAn enlargement of the wellbore diameter beyond the size of the drill bit, caused by erosion from the drilling...
• WashoverTo free stuck pipe or tools in a wellbore by running a larger diameter pipe over the stuck object and...
• Washover pipeA large-diameter pipe run over a stuck drill string or other downhole equipment to free it from the wellbore...
• Washover shoeA specialized cutting shoe run on the bottom of a washover pipe, used to cut away and retrieve a stuck pipe...
• Wastewater cleanupThe process of treating and purifying water that has been used in drilling operations to remove contaminants...
• Water alternating gas (WAG)An enhanced oil recovery method involving the sequential injection of slugs of water and gas into a...
• Water blockA reduction or cessation of hydrocarbon flow into the wellbore caused by the invasion of water into the pore...
• Water bottom rollA type of coherent noise in marine seismic data caused by seismic energy that travels horizontally along the...
• Water clarificationThe process of removing suspended solids, colloidal particles, and dissolved impurities from water used in or...
• Water coningThe upward movement of water from an underlying aquifer into the oil or gas production zone, forming a cone...
• Water controlTechniques and treatments applied to a wellbore to reduce or eliminate unwanted water production while...
• Water cushionA column of water placed in the test string or tubing above a packer or perforating gun before a drill stem...
• Water cutThe proportion of water in the total liquid produced from a well, expressed as a percentage or a fraction. It...
• Water formation volume factorThe ratio of the volume of water at reservoir conditions to its volume at standard surface conditions. This...
• Water gunA marine seismic energy source that generates an acoustic pulse by rapidly injecting high-pressure water into...
• Water hammerA pressure surge or shock wave caused by a sudden change in the velocity of fluid in a pipeline, typically...
• Water influxThe movement of water from an aquifer into a hydrocarbon reservoir, driven by pressure differences. This...
• Water lossThe volume of drilling fluid filtrate that invades a permeable formation from the wellbore, leaving behind a...
• Water mudA drilling fluid system in which water forms the continuous phase, with solids and other additives dispersed...
• Water, oil, and solids testA standard measurement of the volume percentages of water, oil and solids in a drilling fluid, made with a...
• Water productionThe flow of formation water, or connate water, into the wellbore along with hydrocarbons. This water can...
• Water saturationThe fraction of the pore volume in a rock that is occupied by formation water, expressed as a percentage or a...
• Water-based drilling fluidA drilling fluid system where water is the primary liquid phase, carrying suspended solids and dissolved...
• Water-based mudA drilling fluid that uses water as its continuous phase, with solids and chemical additives dispersed within...
• Water-cut meterA downhole or surface instrument that measures the percentage of water in a produced fluid stream. It...
• WaterdriveA natural reservoir drive mechanism where the expansion of an underlying or adjacent aquifer provides the...
• Water-filled resistivityThe electrical resistivity of a rock formation when its pore spaces are completely saturated with formation...
• WaterfloodA secondary recovery method in which water is injected into a reservoir through injection wells to sweep oil...
• Waterflood kickAn uncontrolled influx of formation fluids into the wellbore during a waterflooding operation, caused by an...
• WaterfloodingA secondary recovery method in which water is injected into a reservoir through injection wells to maintain...
• Water-flow logA production log that identifies the location of water movement into or out of a wellbore and quantifies its...
• Water-in-oil emulsionA type of drilling fluid, also called an invert emulsion, in which droplets of water or brine are dispersed...
• Water-mud emulsifierA chemical additive used in drilling fluids to create and stabilize an emulsion of water droplets within a...
• Water/oil ratio (WOR)The ratio of the volume of water produced to the volume of oil produced from a well, expressed as a...
• Water-to-cement ratioThe proportion of water to dry cement by weight in a cement slurry used for wellbore cementing operations...
• Water-wetDescribing a reservoir rock where water preferentially adheres to the surface of the rock grains, forming a...
• WaveA disturbance that propagates through a medium or space, transferring energy without necessarily transferring...
• Wave equationA mathematical relationship that describes the propagation of waves through a medium as a function of space...
• WaveformThe shape of a wave, such as a seismic wave, displayed as a graph of amplitude versus time. It represents the...
• WavefrontA surface connecting points of constant phase on a propagating wave, moving outward from the source. In...
• WaveletA short-duration oscillation with a distinct beginning and end, used in seismic exploration to represent the...
• WavenumberA measure of spatial frequency, representing the number of waves per unit distance or the spatial rate of...
• Weak pointA deliberately designed section in a drilling or logging string that is intended to fail at a predetermined...
• Weathered layerA near-surface zone of unconsolidated or partially consolidated material that has undergone physical and...
• WeatheringThe in-situ physical disintegration and chemical decomposition of rocks and minerals at or near the Earth's...
• Weathering correctionA static correction applied to seismic reflection data to compensate for the time delay caused by the...
• Wedge gateA type of gate valve that uses a wedge-shaped disc to block or allow fluid flow. When the valve is closed...
• WeightA measure of the density of a drilling fluid, expressed as pounds per gallon (ppg), pounds per cubic foot...
• Weight indicatorA primary instrument on the driller's console that displays the total force pulling down on the rig's...
• Weight materialA finely ground, high-density solid added to drilling fluids to increase their specific gravity. These...
• Weighted mudA drilling fluid that has had its density increased by the addition of high-specific-gravity solids, such as...
• Weighting agentA finely divided solid substance introduced into a drilling fluid to increase its density. This increase in...
• Weighting materialA high-density solid, typically in powdered form, added to drilling mud to increase its specific gravity...
• Well cleanupThe process of flowing a newly completed or stimulated well to remove drilling fluids, completion fluids...
• Well controlThe methods and equipment employed to prevent an uncontrolled flow of formation fluids, such as oil, gas, or...
• Well flow rateThe volume of fluid, such as oil, gas, or water, produced from a well over a specific period. This...
• Well interferenceThe pressure response observed in a well caused by a change in the production or injection rate of a...
• Well interference testingA diagnostic procedure conducted to determine the degree of hydraulic communication between wells within a...
• Well logA continuous record of physical properties of rock formations encountered in a borehole, measured by...
• Well placementThe process of determining the optimal three-dimensional trajectory for a wellbore to maximize contact with...
• Well planA detailed engineering document outlining the proposed design, trajectory, and operational procedures for...
• Well potentialThe maximum sustainable production rate that a well can achieve under specific operating conditions...
• Well production rateThe quantity of hydrocarbons, either oil or natural gas, extracted from a well over a given time interval...
• Well servicingRoutine maintenance and remedial operations performed on a producing well to sustain or enhance its...
• Well shootA survey that measures the travel time of seismic energy from a surface source to a geophone placed at known...
• Well stimulationA set of techniques applied to a wellbore or reservoir to enhance the flow of hydrocarbons into the well...
• WellboreThe hole drilled by the bit to create a well, including the openhole or uncased portion and the cased...
• Wellbore damageA reduction in the permeability of the reservoir rock immediately surrounding the wellbore, hindering fluid...
• Wellbore diagramA schematic drawing of a well from surface to total depth that shows the casing strings, liners, tubing...
• Wellbore orientationThe direction of a well's trajectory in three-dimensional space, described by its inclination and azimuth at...
• Wellbore storage effectsThe phenomenon where the volume of fluid within the wellbore itself affects the early-time pressure response...
• WellheadThe surface termination of a wellbore that incorporates a system of spools, valves, and seals for pressure...
• Wentworth scaleA geological classification system for sedimentary particles based on their size, ranging from boulders down...
• Wet combustionAn enhanced oil recovery method that combines forward combustion with the injection of water along with air...
• Wet gasNatural gas that contains a relatively high proportion of heavier hydrocarbon components, such as ethane...
• Wet-clay porosityThe pore volume within clay minerals that is occupied by water, which is bound to the clay surfaces and does...
• WettabilityThe preference of a solid surface, such as a reservoir rock, to be in contact with one fluid rather than...
• Wettability changeAn alteration in the preference of a reservoir rock surface for oil or water, often induced by the injection...
• Whole coreA cylindrical sample of rock, typically 3 to 4 inches in diameter and several feet long, retrieved from a...
• Whole-mud dilutionA way of lowering solids concentration, and with it density and viscosity, by discarding part of the...
• Wide-azimuth towed-streamer acquisitionA marine seismic data acquisition method that employs multiple source vessels and receiver streamers spread...
• WildcatAn exploration well drilled in an area where no oil or gas has been previously discovered. These high-risk...
• WindowA defined segment of a seismic trace or a specific time or depth interval within a seismic dataset. This...
• Wing valveOne of two side valves on the Christmas tree assembly, located on the flow arms extending from the central...
• Winsor phase behaviorA classification system describing the types of microemulsion phases that form when oil, water, and...
• Wiper plugA device used in cementing operations to separate the drilling fluid from the cement slurry and to clean the...
• Wiper tripThe process of pulling the drill string out of the wellbore and then running it back in, usually over a...
• Wire clampA clamp that fastens around a wireline or slickline to secure it and stop it moving, for example to hold the...
• WirelineA method of lowering instruments or tools into a wellbore on a cable for data acquisition or well...
• Wireline cutterA specialized tool deployed on a wireline to sever a stuck wireline or slickline downhole, allowing for...
• Wireline formation testA downhole measurement technique that obtains reservoir fluid samples and pressure data from specific zones...
• Wireline formation testerA downhole tool deployed on a wireline to measure formation pressures and collect fluid samples from specific...
• Wireline grabA fishing tool designed to retrieve a broken or lost wireline or slickline from the wellbore. It features a...
• Wireline logA continuous record of formation properties measured against depth by an instrument package lowered into a...
• Wireline-retrievable safety valve (WRSV)A downhole safety valve that can be installed and retrieved using wireline operations, without requiring a...
• Wire-wrapped screenA type of sand control device consisting of a perforated base pipe over which a continuous wire is wrapped...
• Work basketA platform or cage suspended from a crane or derrick, used to elevate personnel and tools to perform work at...
• Work stationA high-performance computer system equipped with specialized software and graphics capabilities, used by...
• Work stringA string of tubing or drill pipe run into a wellbore to perform a specific operation, such as cementing...
• Working interestAn ownership interest in an oil and gas lease that grants the holder the right to explore, drill, and produce...
• WorkoverAny operation performed on a producing well to restore or improve its production. This can involve repairing...
• Workover fluidA specialized fluid circulated in the wellbore during workover operations to control formation pressures...
• Workover stringA string of pipe, typically tubing or drill pipe, run into a wellbore to perform remedial or maintenance...
• WormSlang for a new and inexperienced member of a drilling crew who has not yet become a hand. During trips the...
• WormholeA large, high-permeability channel created in a carbonate formation during an acid stimulation treatment. As...
• Wrench faultA strike-slip fault characterized by nearly horizontal movement, where blocks of the Earth's crust slide past...

117 of 4,469 terms in Oil and gas terminology (MLC-0103). Request the full dataset.