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Petroleum: a primer for Kansas, Page 15 of 15
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abandon, v: To cease producing oil and gas from a well when it becomes unprofitable. A wildcat well may also be abandoned if it has been proved unproductive.

acidize, v: To treat oil-bearing limestone or dolomite with acid in order to enlarge pore space and improve permeability. Acid is injected under pressure.

adjustable choke, n: Special valve by which the rate of flow from a well may be regulated.

air drilling, n: Method of rotary drilling that uses air under pressure to cool the bit and remove cuttings from the bore hole.

American Petroleum Institute: Founded in 1920, the API is a national trade organization which maintains offices in Washington, D.C., and Dallas, Texas; the leading standardizing organization for the petroleum industry.

angular unconformity, n: Unconformity or break between two series of rock layers such that rocks of the lower series underlie rocks of the upper series at an angle; the two series are not parallel. The lower series was deposited, then tilted and eroded prior to deposition of the upper layers.

annular space (annulus), n: Space surrounding a cylindrical object within a cylinder such as tubing inside of casing or casing inside of a bore hole.

anticline, n: Elongate fold in the rocks in which sides slope downward and away from the crest; an upfold.

API, abbr: American Petroleum Institute.

arkose, n: Sandstone containing a significant proportion of feldspar grains, usually signifying a source area composed of granite or gneiss.


back off, v: To unscrew one threaded section of pipe from another.

back pressure, n: Pressure resulting from restriction of full natural flow of oil or gas.

barrel, n: Measure of volume for petroleum products. One barrel is the equivalent of 42 U.S. gallons.

basement, n: In geology, the crust of the Earth beneath sedimentary deposits, usually, but not necessarily, consisting of metamorphic and/or igneous rocks of Precambrian age.

basement fault, n: Fault that displaces basement rocks and originated prior to deposition of overlying sedimentary rocks. Such faults may or may not extend upward into overlying strata, depending upon their history of rejuvenation.

bed, n: Specific layer of earth or rock in contrast to other layers of material lying above or below it.

bit, n: Cutting or boring element used in drilling oil and gas wells.

blow out, n: Uncontrolled flow of gas, oil, or other well fluids into the atmosphere.

blowout preventer, n: Equipment installed at the surface on drilling rigs to prevent the escape of pressure from the well during drilling or completion operations.

bore hole, n: Well bore; the hole made by drilling or boring.

bottom-hole pressure, n: Pressure in a well measured at or near the bottom of the hole.

BS or BS&W, abbr: Basic sediment or basic sediment and water; it refers to contaminants in produced crude oil.


cable tool, n: Drilling method in which the hole is drilled by dropping a sharply pointed bit on the bottom of the hole. The bit is raised and dropped by means of a cable attached to it.

cap rock, n: Impermeable rock overlying an oil or gas reservoir. It is part of the trapping mechanism.

cased hole, n: Well bore in which casing has been inserted and cemented.

casing, n: Steel pipe placed in a bore hole to prevent the walls from collapsing and to provide a means of extracting oil and gas if the well is productive.

casing head, n: Heavy, flanged steel fitting that connects to the first string of casing and provides a housing for the slips and packing assemblies by which intermediate strings of casings are suspended and the annulus sealed off.

casing-head gas, n: Associated and dissolved gas produced along with crude oil.

casing pressure, n: Gas pressure built up between the casing and tubing.

casing shoe, n: Short, heavy, hollow cylindrical steel section with a rounded bottom, which is placed on the end of the casing string to facilitate the insertion of the casing into the well bore.

catch samples, v: To obtain cuttings made by the drill bit. The cuttings are obtained from the drilling fluid as it emerges from the well bore. The cuttings are examined by geologists to determine the nature of the rock being penetrated and the possible presence of oil or gas.

cellar, n: Pit in the ground to provide additional space between the well head and the rig floor to accommodate the installation of equipment such as blowout preventers, etc.

cement casing, v: To fill the annulus between the casing and bore-hole wall with cement to support the casing and to prevent the migration of fluid between permeable zones.

cementing, n: Application of a liquid slurry of cement and water at various points between the casing and the bore-hole wall.

chert, n: Very dense siliceous rock usually found as nodular or concretionary masses, or as distinct beds, associated with limestones. jasper is red chert containing iron-oxide impurities.

choke, n: Device inserted in a flow line to regulate the rate of flow.

Christmas tree, n: Control valves, pressure gauges, and chokes assembled at the top of a well to control the flow of oil and gas.

circulation, n: Movement of drilling fluid out of the mud pits, down the drill stem, up the annulus, and back to the mud pits.

clastic rocks, n: Deposits consisting of fragments of preexisting rocks; conglomerate, sandstone, and shale are examples.

condensate, n: Hydrocarbons in the gaseous state under reservoir conditions but which become liquid in passage up the hole or at the surface.

conductor pipe, n: Short string of large-diameter pipe or casing that is used to keep the top of the well bore open and to provide a means of conducting the drilling fluid to the mud pit from the well bore.

conglomerate, n: Consolidated equivalent of gravel. The constituent rock and mineral fragments may be of varied composition and range widely in size. The rock fragments are rounded and smoothed from transportation by water.

connate water, n: Water that is inherent to the producing formation; or fossil seawater that was trapped in the pore spaces of sediments during their deposition.

contact, n: Surface, often irregular, which constitutes the junction of two bodies of rock.

continental deposits, n: Deposits laid down on land or in bodies of water not connected with the ocean.

core, n: Cylindrical sample taken from a formation for geological analysis during the drilling of a well.

core analysis, n: Laboratory analysis of a core sample to determine its properties such as porosity, permeability, type of rock, fluid content, and probable productivity.

core barrel, n: Tubular device attached to the bottom of the drill pipe with a core bit on the end to cut a core sample.

correlation, n: Process of determining the position or time of occurrence of one geologic phenomenon in relation to others. Usually it means determining the equivalence of geologic formations in separated areas through a comparison and study of fossils or rock peculiarities.

crown block, n: Assembly of sheaves mounted on the top of the derrick over which the drilling line is reeved.

cuttings, n: Fragments of rock which are dislodged by the drill bit and returned to the surface by the drilling fluid.


deadman, n: An anchoring device with a guy line attached to it for bracing a mast or tower.

degasser, n: Equipment used to remove gas from the drilling fluid.

density, n: Weight of a substance per unit volume.

derrick, n: Large, load-bearing structure which rises above the derrick floor on a drill rig, from which the drill pipe is suspended. The derrick is equipped with sheaves and blocks through which the drilling line is threaded.

desander, n: Centrifuge used to remove fine particles of sand from the drilling fluid.

desilter, n: Centrifuge device, much like a desander, used to remove silt-sized particles from the drilling fluid.

development well, n: Well drilled in proven territory to complete a desired pattern of production.

deviation, n: Inclination of the well bore from the vertical.

deviation survey, n: Operation to determine the angle of deviation from the vertical.

diamond bit, n: Steel bit that has a surface of industrial diamonds.

directional drilling, n: Intentional deviation of a well bore from the vertical.

disconformity, n: Break in the orderly sequence of stratified rocks above and below which the beds are parallel. The break is usually indicated by erosional channels, indicating a lapse of time or absence of part of the rock sequence.

displacement fluid, n: In oil-well cementing, the fluid--usually drilling mud or saltwater--that is pumped into the well after the cement to force the cement out of the casing and into the annulus.

dolomite, n: Mineral composed of calcium and magnesium carbonate, or a rock composed chiefly of the mineral dolomite, formed by alteration of limestone.

dome, n: Upfold in which strata dip downward in all directions from a central area; the opposite of a basin.

drawworks, n: Hoisting equipment on a drilling rig. It is essentially a large winch.

drill collar, n: Heavy, thick walled section of pipe that is used between the drill bit and the drill pipe to put weight on the bit.

driller, n: Employee directly in charge of the rig and the drilling crew during a shift or tour. This person is responsible for the drilling rig and the downhole condition of the well.

drilling crew, n: Driller, a derrick-man, and two or more helpers who operate a drilling rig for one tour (pronounced tower) each day.

drilling fluid, n: Circulating fluid used in the drilling of oil and gas wells. Its purpose is to cool and lubricate the drill string and bit, to return the cuttings to the surface, and to confine formation fluids to their respective horizons.

drill pipe, n: Heavy, seamless tubing used to rotate the bit and to circulate the drilling fluid.

drill stem, n: Entire length of tubular pipes composed of the kelly, drill pipe, and drill collars.

drill string, n: The column of drill pipe, not including the drill collars or the kelly.

DST, abbr: Drill-stem test. (see formation testing)

disposal well, n: Well through which water (usually saltwater) is returned to subsurface formations.

dissolved gas, n: Natural gas which is in solution with crude oil in the reservoir.

dry hole, n: Exploratory or development well that contains insufficient amounts of oil or gas to justify completion as an oil or gas well.


electric well log, n: Record of certain electrical characteristics of formations penetrated by the bore hole, made to identify the formations, determine the porosity, determine the nature and quantity of the fluids that they may contain, and their estimated depth.

eolian, adj: Pertaining to wind. Designates rocks or soils whose constituents have been transported and deposited by wind. Windblown sand and dust (loess) deposits are termed "eolian."

erosional unconformity, n: Break in the continuity of deposition of a series of rocks caused by an episode of erosion.


facies, n: Generally, the term "facies" refers to a physical aspect or characteristic of a sedimentary rock, as related to adjacent strata. It is usually applied to distinguish different aspects of the sediments in time-equivalent or laterally continuous beds.

fault, n: Break or fracture in rocks, along which there has been movement, one side relative to the other. Displacement along a fault may be vertical (normal or reverse fault) or lateral (strike-slip or "wrench" fault).

field, n: Geographical area in which a number of oil or gas wells produce from one or more oil pools.

fire wall, n: Wall of earth built around an oil tank or other surface equipment to hold the oil if a leak should occur.

fish, n: Object left in the hole during drilling operations. It must be removed before drilling operations can be resumed.

fishing tool, n: Tool designed to recover equipment lost in the well.

float collar, n: Device used in cementing casing. It is attached to several joints above the bottom of the casing and prevents the entry of drilling fluid into the casing as it is inserted into the well bore, allowing the casing to float during its descent, thus decreasing the load on the derrick.

flow by heads, v: Well that flows at irregular intervals.

flowing wells, n: Wells that produce oil or gas without artificial lift.

flow lines, n: Surface pipes through which oil or gas flow from well head to storage.

fluid injection, n: Injection of liquid into a reservoir to force oil toward and into producing wells.

fluid level, n: Distance between the well head and the point to which fluid rises in the well.

formation, n: Fundamental unit in the local classification of layered rocks, consisting of a bed or beds of similar or closely related rock types, and differing from strata above and below. A formation must be readily distinguishable, thick enough to be mappable, and of broad regional extent. A formation may be subdivided into two or more members, and/or combined with other closely related formations to form a group.

formation fracturing, n: Method of stimulating production of oil or gas by fracturing the rock with a combination of high-pressure, acidic fluid, and propping agents such as sand and glass beads. The purpose is to increase the permeability of the producing formation.

formation pressure, n: Pressure exerted by fluids in a formation.

formation testing, n: Method of determining the potential productivity of a formation or portion of a formation prior to installing casing in the well. By means of drill pipe, packers, and special valving equipment, a sample of the formation fluid can be recovered and analyzed at the surface. Pressure data are also acquired from the formation.


gas-cut mud, n: Drilling mud that has formation gas entrained in it. The gas must be removed prior to returning the mud or drilling fluid to the well bore.

gas lift, n: Method of producing oil by injecting gas into the casing and allowing it to force the oil to the surface through the tubing.

gas/oil ratio, n: Measurement of the amount of gas produced for a specific quantity of oil. The measurement is given in cubic feet per barrel.

geologic map, n: Map showing the geographic distribution of geologic formations and other geologic features--such as folds, faults, and mineral deposits--by means of color or other appropriate symbols.

granite, n: Intrusive igneous rock with visibly granular, interlocking, crystalline quartz, feldspar, and perhaps other minerals.

gravity-API, n: Specific gravity or density of oil expressed in terms of a scale developed by the American Petroleum Institute. The formula is:

formula for calculating Specific gravity

The lighter the oil, the higher the gravity.


halite, n: Common rock salt (NaCl) precipitates from seawater under conditions of intense evaporation. Occurs as bedded, usually crystalline, white or red rock only in the subsurface; flows plastically under high confining pressure.

hydrocarbons, n: Organic compounds of hydrogen and carbon, whose densities, boiling points, and freezing points increase as their molecular weights increase.


igneous rock, n: Rocks formed by solidification of molten material (magma), including rocks crystallized from cooling magma at depth (intrusive) and those poured out onto the surface as lavas (extrusive).

impermeable, adj: Preventing the passage of fluid. The absence of connecting channels between pore spaces in rock causes its impermeability.

intermediate casing, n: String of casing that is sometimes inserted into the well bore after the surface casing to prevent caving and further hole problems as drilling continues.


kelly, n: Heavy steel member, four- or six-sided, suspended from the swivel through the rotary table and connected to the topmost joint of the drill string. The kelly turns the drill stem as the rotary table turns.

kelly bushing, n: Device fitted to the rotary table through which the kelly passes and by which the turning motion of the rotary table is transferred to the kelly.


LACT ("lease automatic custody transfer"), acronym: Automatic measuring equipment that allows for the transfer of oil or gas from lease to pipeline without any manual activity or witnessing.

law of superposition, n: Concept stating that, if undisturbed, any sequence of sedimentary rocks will have the oldest beds at the base and the youngest at the top.

limestone, n: Bedded sedimentary deposit consisting chiefly of calcium carbonate, usually formed from the calcified hard parts of organisms.

location, n: Place at which a well is to be or has been drilled.

log, n: Systematic recording of data, as from a driller’s log, electric well log, radioactivity log, mud log, etc.


make a connection, v: To connect another joint of drill pipe to the drill string.

make a trip, v: To withdraw all of the drill pipe, drill collars, and drill bit from the well bore and to insert it back into the well bore again. This is frequently done to change drill bits.

marginal well, n: Well whose production is barely sufficient to pay its operating costs.

metamorphic rock, n: Rocks formed by the alteration of preexisting igneous or sedimentary rocks, usually by intense heat and/or pressure, or mineralizing fluids.

miscible flood, n: Injection of a solvent that lowers the viscosity of the crude oil in a formation which is followed by a displacing fluid.

mouse hole, n: Opening through the rig floor, usually lined with pipe, into which a length of drill pipe is placed temporarily for later connection to the drill string.

mud, n: Drilling fluid circulated during drilling operations. It may consist of water and native mud or may contain many additives that give the mud certain properties.

mud cake, n: Sheath of mud solids that forms on die wall of the bore hole when the liquid from the mud filters into the formation.

mud pit, n: Reservoir or tank, usually made of steel, through which the drilling fluid is circulated. Additives are mixed with the mud in the pit.

mud pump, n: Pump which circulates the drilling fluid throughout the drilling system.

multiple completion, n: Well equipped to produce oil and/or gas separately from more than one reservoir.


natural gas, n: Mixture of hydrocarbons and varying quantities of nonhydrocarbons that exist either in the gaseous state or in solution with crude oil in natural underground reservoirs.

natural gas liquids, n: Those portions of reservoir gas which are liquefied at the surface in lease separators, or gas-processing plants.


offset well, n: Well that is drilled close by another producing well. An offset well is usually only one spacing unit away from a producing well.

oil field, n: Surface area overlying an oil reservoir or reservoirs.

oil pool, n: Accumulation of oil in the pores of sedimentary rock that yields petroleum on drilling.

operator, n: Person or company, either proprietor or lessee, actually operating an oil well or lease.

orogeny, n: Literally, the process of formation of mountains, but practically it refers to the processes by which structures in mountainous regions were formed, including folding, thrusting, and faulting in the outer layers of the crust, and plastic folding, metamorphism, and plutonism (emplacement of magmas) in the inner layers. An episode of structural deformation may be called an orogeny, e.g., the Laramide Orogeny.


pay zone, n: Producing formation or interval within a formation.

perforate, v: To pierce the casing wall and cement so as to enable the formation fluids to enter the well bore.

permeability, n: Measure of the ease with which fluids can flow through porous rock.

petroleum, n: Oil or gas obtained from the rocks of the earth.

plug and abandon (P&A), v: To place cement plugs into a dry hole and abandon it.

pore, n: Opening or space within a rock or mass of rock, usually small and often filled with fluid.

porosity, n: State of voids or open spaces existing in rock.

positive choke, n: Choke in which the orifice size must be changed to change the rate of flow through the choke.

potential test, n: Test of the maximum rate at which a well can produce oil.

pressure gradient, n: Scale of pressure differences in which there is a uniform variation of pressure from point to point.

pressure maintenance, n: Repressuring of an oil field to maintain pressure or to slow the decline of reservoir pressure as oil is produced.


radioactivity well logging, n: Recording of the natural or induced radioactive characteristics of subsurface formations.

rat hole, n: Hole in the rig floor from 30 to 35 ft (9 to 10 m) deep, lined with casing that projects above the floor. The kelly and swivel are placed in the rat hole when hoisting operations are in progress.

reserve pit, n: Pit in which a supply of drilling fluid is stored.

rig, n: Derrick, drawworks, and other surface equipment of a drilling unit.

rig down, v: To dismantle a drilling rig.

rig up, v: To assemble a drilling rig.

roughneck, n: Worker on a drilling rig, a subordinate to the driller.

round trip, n: To pull out and subsequently run back into the hole a string of drill pipe or tubing.


samples, n: Well cuttings obtained at designated footage intervals during drilling.

sandstone, n: Consolidated rock composed of sand grains cemented together; usually composed predominantly of quartz, it may contain other sand-sized fragments of rocks and/or minerals.

sedimentary rock, n: Rocks composed of sediments, usually aggregated through processes of water, wind, glacial ice, or organisms, derived from preexisting rocks. In limestones, constituent particles are usually derived from organic processes.

seismograph, n: Device that detects vibrations in the earth, used in prospecting for probable oil-bearing structures.

shale, n: Solidified muds, clays, and silts that are fissile (split like paper) and break along original bedding planes.

shale shaker, n: Device that separates the coarser well cuttings from the drilling fluid when it returns to the surface.

spud in, v: To commence drilling operations.

stratigraphy, n: Definition and interpretation of the layered rocks, the conditions of their formation, their character, arrangements, sequence, age, distribution, and correlation, using fossils and other means.

stripper, n: Well that produces a small quantity of oil, usually less than 10 barrels per day.

swab, n: Device that is inserted into the tubing and lifts oil as it is pulled up.

swab, v: To pull a swab through the tubing in order to lift oil to the surface.

syncline, n: Elongate, troughlike downfold in which the sides dip downward and inward toward the axis.


tectonic, adj: Pertaining to rock structures formed by Earth movements, especially those that are widespread.

trip, n: (see round trip)


unconformity, n: Surface of erosion or nondeposition separating sequences of layered rocks.

unitization, n: System of operating a certain oil and condensate reservoir in order to conduct some form of pressure maintenance, repressuring, waterflood, or other cooperative form to increase ultimate recovery.


well bore, n: Bore hole; the hole drilled by the bit.

well completion, n: Activities and methods necessary to prepare a well for the production of oil or gas.

well head, n: Equipment installed at the surface of the well bore.

wildcat, n: Well drilled in an area where no oil or gas production exists.

WOC, abbr: Waiting on cement.

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Kansas Geological Survey, Education
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