Glossary
As with any number of highly specialized fields, the Oil & Gas industry has a language all its own. Whether dealing with the exploration and production sector or the financial and business end of the industry, the uninitiated can find "Oil & Gas Speak" a confusing amalgam of terms, acronyms, and shorthand that might as well be hieroglyphics. If that's the case for you, consider the following glossary your Rosetta Stone. It doesn't promise to have everyone speaking "Oil & Gas" fluently in just a few short weeks, but it will help you crack the code, and help you on your way to understanding what the old hands in the game are saying when they speak "Oil & Gas."
A
Abandon: To temporarily or permanently cease production from a well or to cease further drilling operations.
Abnormal pressure: Pressure outside the normal or expected range.
Abstract of title: A chronological history of the ownership of a tract of land.
Acidize: To treat formations with acid for the purpose of increasing production.
Acre: The most common of land measure in the United States. A square 210 feet on a side (44,100 sq. ft) would be a bit larger than an acre (43,560 sq. ft). There are 640 acres in a square mile.
Acre-foot: In the U.S., the thickness of a pay zone is measured in feet, and the area of the reservoir is measured in acres. An acre-foot is a volume of reservoir rock that is one acre in area and one foot thick.
AFE (Authorization For Expenditure): An estimate of the costs of drilling and completing a proposed well, which the operator provides to each working interest owner before the well is commenced.
American Petroleum Institute (API): A trade association that represents the interests of and sets standards for the oil and gas industry.
Annulus of a well: The space between the surface casing and the inner, producing well-bore casing.
Anticline: A geological term describing a fold in the earth's surface with strata sloping downward on both sides from a common crest. Anticlines frequently have surface manifestations like hills, knobs, and ridges. At least 80 percent of the world's oil and gas has been found in anticlines.
API gravity: The weight per unit of volume of crude oil expressed in degrees according to an American Petroleum Institute recommended system. Higher gravity crudes are generally considered more valuable.
Artificial lift: Any method used to raise oil to the surface after a well ceases to flow.
Asphalt: A solid hydrocarbon which may be deposited within the reservoir rock, in well equipment, or in surface lines and tanks.
Associate gas: The gas that occurs with oil either as free gas or in solution. When occurring alone, it is referred to as unassociated gas.
B
Back off: To unscrew one threaded piece (such as a section of pipe) from another.
Back-in interest (financial): A type of interest in a well or property that becomes effective at a specified time in the future, or on the occurrence of a specified future event.
Back-in unit (equipment): A portable servicing or workover rig that is self-propelled, using the hoisting engines for motive power. Because the driver's cab is mounted on the end opposite the mast support, the unit must be backed up to the wellhead.
Barrel (bbl): A measure of volume for petroleum products in the United States. One barrel is the equivalent of 42 U.S. gallons or 0.15899 cubic meters.
Basement rock - Igneous or metamorphic rock lying below sedimentary formations in the earth's crust. Basement rock does not contain petroleum deposits.
Basin - A depression in the earth's crust in which sedimentary materials have accumulated. Such a basin may contain oil or gas fields.
BCF (billion cubic feet) - The cubic foot is a standard unit of measure for gas at atmospheric pressure.
Beam pumping unit: A machine designed specifically for sucker rod pumping. An engine or motor (prime mover) is mounted on the unit to power a rotating crank. The crank moves a horizontal member (walking beam) up and down to produce reciprocating motion. This reciprocating motion operates the pump.
Behind pipe: If a well drills through several pay zones and is completed in the deepest productive reservoir, casing is set all the way down to the producing zone. Viewed from (a perspective) inside the borehole, reserves in the shallower pay zones up the hole are behind the casing.
Bit: The cutting or boring element used in drilling oil and gas wells.
Bleed: To drain off liquid or gas, generally slowly, through a valve called a bleeder. To bleed down, or bleed off, means to release pressure slowly from a well or from pressurized equipment.
Bleeding core: A core sample of rock so highly permeable and saturated that oil drips from it.
Block: One or more pulleys, or sheaves, mounted into a common framework in order to rotate on a common axis. The crown block is an assembly of sheaves mounted on beams at the top of the derrick or mast. The traveling block is an assembly of sheaves mounted in a framework that allows the block to move up and down.
Blowout: A sudden and uncontrolled escape of gas, oil, or other well fluids from the well, usually occurring during drilling, and generally caused by uncontrolled high pressure in a formation being penetrated.
Blowout preventer (BOP): One or more valves installed at the wellhead to prevent the escape of pressure either in the annular space between the casing and the drill pipe or in an open hole (for example, hole with no drill pipe) during drilling or completion operations.
Bonus Money: Paid to a landowner or other holder of mineral rights by the lessee for the execution of an oil and gas lease in addition to any rental or royalty obligations specified in the lease.
Bore: The inside diameter of a pipe or a drilled hole; or, as a verb, to penetrate or pierce with a rotary tool.
Bottomhole: The lowest or deepest part of a well.
Bottomhole pressure: The pressure of the reservoir or formation at the bottom of the hole.. It is caused by the hydrostatic pressure of the wellbore fluid and, sometimes, by any backpressure held at the surface. A decline in pressure indicates some depletion of the reservoir.
Break out: To unscrew one section of pipe from another section, especially drill pipe while it is being withdrawn from the wellbore.
BS&W (basic sediment and water): Material pumped up with oil and gas which must be separated out.
Btu (British thermal unit): A standard measure of heat content in a fuel. One Btu equals the amount of energy required to raise the temperature of one pound of water one degree Fahrenheit at or near 39.2 degrees Fahrenheit.
Bullet perforator: A tubular device that, when lowered to a selected depth within a well, is engaged forcing the projectiles (bullets) through the casing and cement to provide holes through which the formation fluids may enter the wellbore.
Butane: A hydrocarbon associated with petroleum. It is gaseous at ordinary atmospheric conditions.
C
Cable: A rope of wire, hemp, or other strong fibers; or braided wire used to conduct electricity, often called power cable.
Cable drilling: A method of well-drilling that employs a reciprocating, rather than a rotary, motion to penetrate rock.
Capital Funds: Monies invested in a business for use in conducting the operations of the business.
Capital asset:An asset acquired as an investment, for the purpose of creating a product or service intended to be used in the activities or operations of a business.
Capital costs (Oil & Gas Tax Usage):For Federal income tax purposes, the costs of capital expenditures which may be recovered by deduction against income (through depreciation and depletion).
Capital expenditure: An expenditure intended to benefit the future activities of a business, usually by adding to the assets of a business, or by improving an existing asset.
Capitalize: To treat certain expenditures as capital expenditures for Federal income tax computations.
Carried Interest: A fractional working interest in an oil and gas lease that comes about through an arrangement between co-owners of a working interest.
Casing: Steel pipe placed in an oil or gas well to prevent the wall of the hole from caving in, to prevent movement of fluids from one formation to another and to aid in well control.
Cased hole: A wellbore in which casing has been run.
Casinghead: A heavy, flanged steel fitting connected to the first string of casing. It provides a housing for slips and packing assemblies, allows suspension of intermediate and production strings of casing, and supplies the means for the annulus to be sealed off. Also called a casing spool.
Casinghead gas : Natural gas produced from an oil well, as opposed to gas produced from a gas well.
Casing point: The depth in a well at which casing is set, generally the depth at which the casing shoe rests.
Cellar: A pit in the ground to provide additional height between the rig floor and the well head to accommodate the installation of blowout preventers, ratholes, mouseholes, and so forth.
Cement (b): a powder consisting of alumina, silica, lime, and other substances that hardens when mixed with water. Extensively used in the oil industry to bond casing to the walls of the wellbore.
Cement (v) - Fluid cement is mixed at the surface, pumped to the bottom of a cased well, forced to flow back up the into the annulus between the casing and the borehole. When the cement solidifies, it holds the casing in place, and prevents fluid migration between permeable zones.
Cement plug: A portion of cement placed at some point in the wellbore to seal it.
Chain tongs: a hand tool used to tighten or loosen pipe, consisting of a handle and chain that resembles the chain on a bicycle.
Choke: An orifice installed in a pipeline at the well surface to control the rate of flow
Christmas tree: The control valves, pressure gauges, and chokes assembled at the top of a well to control flow of oil and/or gas after the well has been drilled and completed.
Circulate : To pump drilling fluid into the borehole through the drillpipe and back up the annulus into the mud pit.
Circulation: The movement of drilling fluids described above.
Clean oil: Crude oil containing less than 1 percent sediment and water; "pipeline oil", oil clean enough to send through a pipeline.
CO2 injection: A secondary recovery technique in which carbon dioxide (CO2) is injected into wells as part of a miscible recovery program.
Come out of the hole: To pull the drill stem out of the wellbore to change the bit, to run electric logs, to prepare for a drill stem test, to run casing, and so forth. Also called trip out, tripping out (TOH).
Commissions: Payments to qualified agents of the sponsor of a limited partnership, for selling interests in it to investors. Commissions may take the form of a percent of partnership interests sold, an oil and gas interest, or stock in the sponsor's company.
Complete a well: To finish work on a well and bring it to productive status. Completion involves cleaning out the well, running steel casing and tubing into the hole, adding permanent surface control equipment, and perforating the casing so oil or gas can flow into the well and be brought to the surface.
Condensate: Liquid hydrocarbons separated from natural gas, usually by cooling.
Confirmation well: A well drilled to "prove" the formation encountered by an exploratory well.
Contract: A written agreement that can be enforced by law and that lists the terms under which the acts required are to be performed. A drilling contract may cover such factors as the cost of drilling the well (whether by the foot or by the day), the distribution of expenses between operator and contractor, and the type of equipment to be used.
Conveyance - Legal term for transferring the title of a property from one party to another, typically by deed.
Core: A cylindrical sample taken from a formation for geological analysis.
Core analysis: Laboratory analysis of a core sample that may determine porosity, permeability, lithology, fluid content, angle of dip, geological age, and probable productivity of the formation.
Cracking: The process of breaking down the larger, heavier and more complex hydrocarbon molecules into simpler and lighter molecules, thus increasing the gasoline yield from crude oil. Cracking is done by application of heat and pressure, and in modern time the use of a catalytic agent.
Crew: The workers on a drilling or workover rig, including the driller, the derrickhand, and the rotary helpers.
Crooked hole: A wellbore that has been drilled in a direction other than vertical.
Crown: The crown block or top of a derrick or mast.
Crude oil: Unrefined liquid petroleum as it comes out of the ground. Crude oils range from very light (high in gasoline) to very heavy (high in residual oils). Sour crude is high in sulfur content. Sweet crude is low in sulfur and therefore often more valuable.
Crude oil equivalent: A measure of energy content that converts units of different kinds of energy into the energy equivalent of barrels of oil.
Cuttings : The fragments of rock dislodged by the bit and brought to the surface in the drilling mud. Cuttings samples are analyzed by geologists to obtain information, particularly the presence of oil or gas, in the formations drilled.
CVL (Cotton Valley Lime) : A deep (>12,000 feet) Upper Jurassic geologic formation, part of the Cotton Valley Trend, which occurs throughout the East Texas Basin and extends into Northwest Louisiana. Located between the Bossier/Haynesville Shale formation and the Smackover formation, the CVL, while expensive to drill, stimulate, and produce, has been a prolific reservoir in the East Texas and North Louisiana Fields.
CVS (Cotton Valley Sand): An Upper Jurassic geologic formation, part of the Cotton Valley Trend which occurs throughout the East Texas Basin and extends into Northwest Louisiana. Throughout the region, the CVS interval ranges in depth from 7,000 feet to 12,000 feet. At those depths and because of the general tightness opf the formation, the CVS is an expensive zone to drill, stimulate and produce, yet has been a prolific reservoir in the East Texas Fields.
D
Daily drilling report : A record made each day of the operations on a working drilling rig and, traditionally, phoned, faxed, emailed, or radioed in to the office of the drilling company and possibly the operator every morning.
Deductions:Tax items which may be subtracted from gross income to arrive at taxable income in Federal income tax computations.
Deed: A written document by which the title to a property is transferred from one party (the grantor) to another (the grantee).
Degasser: The equipment used to remove unwanted gas from a liquid, especially from drilling fluid.
Delay rental: Cash payments to the mineral rights owner (lessor) by the working interest owner (lessee), for the privilege of postponing the commencement of drilling operations on the leased property.
Deliverability: A well's tested ability to produce.
Density: The mass or weight of a substance per unit volume. For instance, the density of a drilling mud may be 10 pounds per gallon, or 74.8 pounds/cubic foot.
Derrick: A large load-bearing structure, usually of bolted construction. In drilling, the standard derrick has four legs standing at the corners of the substructure and reaching to the crown block. The substructure is an assembly of heavy beams used to elevate the derrick and provide space to install blowout preventers, casingheads, and so forth.
Development Well: A well drilled in an already discovered oil or gas field.
Diesel fuel: A light hydrocarbon mixture for diesel engines; it has a boiling range just above that of kerosene.
Directional drilling : Intentional deviation of a wellbore from the vertical. Although wellbores are normally drilled vertically, it is sometimes necessary or advantageous to drill at an angle from the vertical. Controlled directional drilling makes it possible to reach subsurface areas laterally remote from the point where the bit enters the earth. Directional drilling is much more expensive than conventional drilling procedures.
Dissolved gas: Natural gas that is in solution with crude oil in the reservoir.
Distillate: Liquid hydrocarbons, usually colorless and of high API gravity, recovered from wet gas by a separator that condenses the liquid out of the gas.
Division Order: A contract for the sale of oil or gas, by the holder of a revenue interest in a well or property, to the purchaser (often a pipeline transmission company).
Domestic production: Oil and gas produced in the United States as opposed to imported product
Downhole: Refers to equipment located or operations that take place down inside the borehole.
Downstream: All operations taking place after crude oil is produced, such as transportation, refining, and marketing.
Drill : To bore a hole in the earth, usually to find and remove subsurface formation fluids such as oil and gas.
Drill bit: The part of the drilling tool, the cutting or boring element, that cuts through rock strata in drilling oil and gas wells.
Drilling contract: An agreement made between a drilling company and an operating company to drill a well. It generally sets forth the obligation of each party, compensation, identification, method of drilling, and depth to be drilled.
Drill string: Also called drill pipe or drill stem. Thirty-foot lengths of steel tubing screwed together to form a pipe connecting the drill bit to the drilling rig. The string is rotated to drill the hole and also serves as a conduit for drilling mud.
Drilling fluid/ drilling mud: Circulating fluid, one function of which is to lift cuttings out of the wellbore and to the surface. It also serves to cool the bit, to counteract downhole formation pressure, to prevent the wall of the borehole from collapsing, and to prevent other fluids from entering the well bore..
Drilling fund: The generic term employed to describe a variety of organizations established to attract venture capital to oil and gas exploration and development. Typically the fund is established as a joint venture or limited partnership.
Drilling platform: An offshore structure with legs anchored to the sea bottom that supports the drilling of up to 35 wells from one location.
Drilling rig: The surface equipment used to drill for oil or gas, consisting chiefly of a derrick, a winch for lifting and lowering drill pipe, a rotary table to turn the drill pipe, and engines to drive the winch and rotary table.
Drill pipe: The heavy seamless tubing used to rotate the bit and circulate the drilling fluid. Joints of pipe are generally approximately 30 feet long are coupled together by means of tool joints.
Drill stem: All members in the assembly used for rotary drilling from the swivel to the bit, including the kelly, the drill pipe and tool joints, the drill collars, the stabilizers, and various specialty items. Compare drill string.
Drill stem test (DST): A method of testing to determine if oil or gas is present in a formation.. The basic drill stem test tool consists of a packer or packers, valves or ports that can be opened and closed from the surface, and two or more pressure-recording devices. The tool is lowered on the drill string to the zone to be tested. The packer or packers are set to isolate the zone from the drilling fluid column.
Dill string: The column, or string, of drill pipe with attached tool joints that transmits fluid and rotational power from the kelly to the drill collars and the bit. Often, the term is loosely applied to include both drill pipe and drill collars.
Dry hole: Any well that does not produce oil or gas in commercial quantities. A dry hole may flow water, gas, or even oil, but not in amounts large enough to justify production.
Dry natural gas: Natural gas containing few or no natural gas liquids (liquid petroleum mixed with gas).
Dual completion: A single well that produces from two separate formations at the same time. Production from each zone is segregated by running two tubing strings with packers inside the single string of production casing, or by running one tubing string with a packer through one zone while the other is produced through the annulus.
Due Diligence: In an offering of securities, certain parties who are responsible for the accuracy of the offering document, have an obligation to perform a "due diligence" examination of the issuer; issuer's counsel, underwriter of the security, brokerage firm handling the sale of the security. Due diligence refers to the degree of prudence that might properly be expected from a reasonable man, on the basis of the significant facts which relate to a specific case.
E
Economic interest: An interest in oil and gas in the ground. It entitles the owner to a deduction from gross income derived from production of that oil and gas as specified in Federal income tax regulations.
Electric well log: A record of certain electrical characteristics (such as resistivity and conductivity) of formations traversed by the borehole. It is made to identify the formations, determine the nature and amount of fluids they contain, and estimate their depth. Also called an electric log or electric survey.
Enhanced oil recovery: Injection of water, steam, gases or chemicals into underground reservoirs to cause oil to flow toward producing wells, permitting more recovery than would have been possible from natural pressure or pumping alone.
Expenses (Tax Usage): Expenditures for business items that have no future life (such as rent, utilities, or wages) and are incurred in conducting normal business activities.
Exploration: The search for oil and gas. Exploration operations include: aerial surveys, geophysical surveys, geological studies, core testing and the drilling of test wells.
Exploratory well: A well drilled to an unexplored depth or in unproven territory, either in search of a new reservoir, in which case it is also known as a "wildcat" well, or to extend the known limits of a field that is already partly developed.
Extraction plant: A plant for the extraction of the liquid constituents in casinghead gas or wet gas.
F
Farm in: When one company drills wells or performs other activity on another company's lease in order to earn an interest in or acquire that lease.
Farm out agreement: An arrangement in which the responsibility of exploration and development is shifted (by assignment) from the working interest owner to another party.
Farmer's oil: An expression that refers to the landowner's share of oil from a well drilled on his property. This royalty is traditionally one-eighth of the produced oil free of any expense to the landowner.
Fault: A break in the continuity of stratified rocks or even basement rocks. Faults are significant to oilmen because they can form traps for oil when the rock fractures, they can break oil reservoirs into noncommunicating sections, they help produce oil accumulations, and they form traps on their own.
Fault trap: A geological formation in which oil or gas in a porous section of rock is sealed off by a displaced, nonporous layer.
Fee lands: Privately owned, nonpublic lands.
Feet of pay: The thickness of the pay zone penetrated in a well.
Field: A geographical area under which one or more oil or gas reservoirs lie, all of them related to the same geological structure.
Fire flooding: A thermal recovery method in which the oil in the reservoir is ignited, the heat vaporizes lighter hydrocarbons and water pushes the warmed oil toward a producing well. Also called in situ combustion. See thermal recovery.
Fish: An object that is left in the wellbore It can be.
Fishing: Recovering an object or objects unintentionally left in the wellbore during drilling or workover operations (anything from a piece of scrap metal to a part of the drill stem) the removal of which must occur before work can proceed.
Flange up: To complete the drilling of a well.
Flaring: The burning of gas vented through a pipe or stack at a refinery, or a method of disposing of gas while a well is being drilled.
Flood: To drive oil from a reservoir into a well by injecting water under pressure into the reservoir formation.
Flow: A current or stream of fluid or gas.
Flowing well: A well that produces oil or gas by its own reservoir pressure rather than by use of artificial means (such as pumps).
Flow line: The surface pipe through which oil or gas travels from a well to processing equipment or to storage.
Flow rate: The speed, or velocity, of fluid or gas flow through a pipe or vessel.
Fluid injection: Injection of gases or liquids into a reservoir to force oil toward and into producing wells.
Formation: A geological term that describes a succession of strata similar enough to form a distinctive geological unit useful for mapping or description.
Formation fluid: Fluid (such as gas, oil, or water) that exists in a subsurface formation.
Formation gas: Gas initially produced from an underground reservoir.
Formation pressure: The force exerted by fluids or gas in a formation, recorded in the hole at the level of the formation with the well shut in. Also called reservoir pressure or shut-in bottomhole pressure.
Fracturing (aka: Frac or Fracing): A means of stimulating and increasing production from a well by opening new channels in the formation. Fluids and chemicals are pumped into the formation under extremely high pressure, causing cracks to open in the reservoir rock. The fracing fluids also carry sand grains or other materials (propping agents) into the cracks. When the pressure is released at the surface, the fracturing fluid returns to the well but leaves behind the propping agents to hold open the formation cracks.
Front-end costs: Costs that are paid out of initial investment in a venture, first, before the venture activities actually begin.
Future prices: Refers to the New York Mercantile Exchange (NYMEX) which introduced futures contracts for crude oil in 1985 and natural gas in 1990.
G
Gamma ray log: A type of radioactivity well log that records natural radioactivity around the wellbore. Shales generally produce higher levels of gamma radiation and can be detected and studied with the gamma ray tool.
Gas cap: The gas that exists in a free state above the oil in a reservoir.
Gas condensate: Liquid hydrocarbons present in casinghead gas that condense when brought to the surface.
Gas drive: The use of the energy that arises from the expansion of compressed gas in a reservoir to move crude oil to a wellbore.
Gas injection well: A well into which gas is injected for the purpose of maintaining or supplementing pressure in an oil reservoir.
Gas lift: The process of raising or lifting fluid from a well by injecting gas down the well through tubing or through the tubing-casing annulus. Injected gas aerates the fluid to make it exert less pressure than the formation does; the resulting higher formation pressure forces the fluid out of the wellbore.
Gas-oil ratio: The number of cubic feet of natural gas produced along with a barrel of oil.
Gas well: A well that primarily produces gas. Legal definitions vary among the states.
General partner: In a limited partnership, the general partner is responsible for managing the partnership's activities (and is commonly the party that put the deal together). His liability to the partnership's creditors is limited.
Geologist: A scientist who gathers and interprets data pertaining to the formations of the earth's crust.
Geophysicist: A geophysicist applies the principles of physics to the understanding of geology.
Go in the hole: To lower the drill stem, the tubing, the casing, or the sucker rods into the wellbore.
Gross income: Total income from an activity, before deduction of (1) items that may be treated as expenses (such as intangible drilling costs), and (2) allowed tax items (such as depletion allowance, depreciation allowance, etc.).
Guaranteed payments: Payments by a partnership to one or more of its partners for services rendered.
Gun perforation: A method of creating holes in a well casing downhole by exploding charges to propel steel projectiles through the casing wall. Such holes allow oil from the formation to enter the well.
Gusher: A well drilled into a formation in which the crude is under such high pressure that at first it spurts out of the wellhead like a geyser. Gushers are rare today owning to improved drilling technology, the use of drilling mud to control downhole pressure, and oilmen's recognition of their wastefulness.
H
Hang rods: To suspend sucker rods in a derrick or mast on rod hangers rather than to place them horizontally on a rack.
Headache (slang): The position in which the mast on a mobile rig is resting horizontally over the driver's cab.
Heavy oil: A type of crude petroleum characterized by high viscosity and a high carbon-to-hydrogen ration. It is usually difficult and costly to produce by conventional techniques.
Held by production (HPB): Refers to an oil and gas property under lease, in which the lease continues to be in force, because of production from the property.
History of a well: A written account of a well's drilling and operation, required by law in some states.
Hook: On a drilling rig, a large, hook-shaped device from which the elevator bails or the swivel is suspended. It turns on bearings in its supporting housing.
Horizontal drilling: A breakthrough in drilling technology whereby a well is drilled vertically to a certain depth, then deviates from the vertical so that the borehole penetrates a productive formation in a manner parallel to the formation. It is much more costly than traditional vertical drilling, but can vastly improve a well's output.
Horsehead: The generally horsehead-shaped steel piece at well end of a pumping unit's beam to which a short loop of cable, called the bridle, is attached to the well's pump rods.
Hydrocarbons: Organic compounds of hydrogen and carbon whose densities, boiling points, and freezing points increase as their molecular weights increase. Crude oil, natural gas, and natural gas condensate are all mixtures of various hydrocarbons, among which methane is the simplest.
Hydrometer: An instrument that measures the specific gravity of liquids.
I
Impermeable: Preventing the passage of fluid. A formation may be porous yet impermeable if there is an absence of connecting passages between the voids within it. See permeability.
Independent producer: A person or corporation that produces oil for the market, who has no pipeline system or refining, or an entrepreneur who secures financial backing and drills his own wells
Induction log: An electric well log in which the conductivity of the formation rather than the resistivity is measured. Because oil-bearing formations are less conductive of electricity than water-bearing formations, an induction survey, when compared with resistivity readings, can aid in determination of oil and water zones.
Initial potential: Flow rate measured during the initial completion of a well in a specific reservoir (initial daily rate of production).
Injection well: A well through which fluids are injected into an underground stratum under pressure. They are used for a variety of purposes... to dispose of salt water or other wastes produced with oil, to maintain pressure in the producing formation, and in secondary recovery operations that drive oil into producing wells, resulting in greater production.
Intangible drilling costs: Expenditures, deductible for federal income tax purposes, incurred by an operator for labor, fuel, repairs, hauling, and supplies used in drilling and completing a well for production.
International Association of Drilling Contractors (IADC): An organization of drilling contractors, oil and gas companies, and service companies that sponsors or conducts research on education, accident prevention, drilling technology, and other matters of interest to its membership and their employees.
Investment Tax Credit (ITC): A credit against income taxes, usually computed as a percent of the cost of investment in certain types of assets.
J
Jack or Unit: An oil-pumping unit. The pumping jack's walking beam provides the up-and-down motion to the well's pump rods.
Jet-perforate: To create holes through the casing with a shaped charge of high explosives instead of a gun that fires projectiles. The loaded charges are lowered into the hole to the desired depth. Once detonated, the charges emit short, penetrating jets of high-velocity gases that make holes in the casing and cement for some distance into the formation. Formation fluids then flow into the wellbore through these perforations.
Joint Interest Billing (JIB): Accounting procedure of billing each working interest owner for his proportional share of drilling and lease operating expenses.
Joint of pipe: A length of drill pipe, tubing, or casing, usually 30 feet in length.
Joint Operating Agreement: A detailed written agreement between the working interest owners of a property setting forth the terms under which that property will be developed.
Joint venture: A large-scale project in which two or more parties cooperate. Each participant retains control over his share, including liability and the right to sell.
Junk: Metal debris lost in a hole. Junk may be a lost bit, pieces of a bit, pieces of pipe, wrenches, or any relatively small object that impedes drilling or completion and must be fished out of the hole.
Junk basket: A device made up on the bottom of the drill stem or on wireline to catch pieces of junk from the bottom of the hole. Circulating the mud or reeling in the wireline forces the junk into a barrel in the tool, where it is caught and held. When the basket is brought back to the surface, the junk is removed. Also called a junk sub or junk catcher.
K
Kelly: The heavy square or hexagonal steel member suspended from the swivel through the rotary table and connected to the topmost joint of drill pipe to turn the drill stem as the rotary table turns.
Kick: An entry of water, gas, oil, or other formation fluid into the wellbore during drilling. It occurs because the pressure exerted by the column of drilling fluid is not great enough to overcome the pressure exerted by the fluids in the formation drilled. If uncontrolled, a kick can lead to a blowout.
Kick off: To bring a well into production. Also to deviate a wellbore from the vertical, as in directional drilling.
Kickoff point (KOP): In directional drilling, the depth in a vertical hole at which a deviated or slant hole is started.
Kill: In drilling, to control a kick by taking suitable preventive measures. In production, to stop a well from producing oil and gas so that reconditioning of the well can proceed.
L
Landman: An oil company employee, or independent, who identifies mineral rights owners and secures leases so that drilling can begin.
Landowner royalty: The share of the gross production of the oil and gas on a property without deducting any of the cost of producing the oil or gas. The usual landowner's royalty is one-eighth of gross production.
Lay down pipe: To pull drill pipe or tubing from the hole and place it in a horizontal position on a pipe rack.
Lease (Oil and Gas): A contract between the owner of the mineral rights on a property (lessor) and an oil company (lessee) and under which the lessor conveys the exclusive right to explore for and produce the minerals on a property, during a specified period of time
Lease acquisition costs: Amounts paid to the mineral rights owner for the right to explore for and produce the minerals on a property. Also know as bonus payments.
Lifting costs: The costs of producing oil from a well or lease; the operating expenses.
Limestone: Sedimentary rock largely consisting of calcite which can be a reservoir rock. It has been estimated that limestone reservoirs contain more oil and gas reserves than all other types of reservoir rock combined.
Limited partnership: A business arrangement in which the general partner manages the partnership's activities and is solely liable for them. The limited partners are liable only to the extent of their contributions.
Liquefied natural gas (LNG): Methane gas which has been converted to liquid form by super cooling it to -260 degrees Fahrenheit.
Liquified petroleum gas (LPG): Propane, butane and ethane gases kept in liquid form by compression and cooling. It is also referred to as "bottled gas."
Location: The place where a well is drilled. Also called well site.
Log: A systematic recording of data, such as a driller's log, mud log, electrical well log, or radioactivity log. Many different logs are run in wells to discern various characteristics of downhole formation. v: to record data.
Log (Logging) a well: The recording of information about subsurface geologic formations, including records kept by the driller and records of mud and cutting analyses, core analysis, drill stem tests, and electric, acoustic, and radioactivity procedures.
Lost circulation: A serious condition in drilling wherein quantities of whole mud are lost to a formation, usually in cavernous, pressured, or coarsely permeable beds. It is evidenced by the complete or partial failure of the mud to return to the surface as it is being circulated in the hole.
Lost pipe: Drill pipe, drill collars, tubing, or casing that has become separated in the hole from the part of the pipe reaching the surface, necessitating its removal before normal operations can proceed; for example, a fish.
Lost time incident: An incident in the workplace that results in an injury serious enough that causes the person injured to be unable to work for a day or more.
M
Make a connection: To attach a joint or stand of drill pipe onto the drill stem suspended in the wellbore to permit deepening the wellbore by the length of the pipe.
Mast: A portable derrick that is capable of being raised as a unit, as distinguished from a standard derrick, which cannot be raised to a working position as a unit. For transporting by land, the mast can be divided into two or more sections to avoid excessive length extending from truck beds on the highway.
Midstream or Middle distillates: Products produced in the middle range of the crude oil refining process which include kerosene, kerosene-based jet fuel, home heating fuel, and diesel fuel.
Migration: The movement of oil and gas through layers of rock deep in the earth.
Mineral Rights: The legal ownership of oil, gas, or other minerals as they naturally occur in place, at or below the surface of a tract of land. The mineral rights owner can explore, drill for, and produce oil and natural gas on or below that land. Mineral rights can be transferred by lease.
MMCF (Million cubic feet): A cubic foot is a standard unit of measure for quantities of gas at atmospheric pressure. The Roman Numeral "M" represents one-thousand; thus, MM is equal to a thousand thousands, or one million.
Mousehole: Shallow bores under the rig floor, usually lined with pipe, in which joints of drill pipe are temporarily suspended for later connection to the drill string.
Mud: The liquid circulated through the wellbore during rotary drilling and workover operations.
Mud logging: The recording of information derived from examination and analysis of formation cuttings made by the bit and of mud circulated out of the hole.
Mud pit: Originally, an open pit dug in the ground to hold drilling fluid or waste materials discarded after the treatment of drilling mud. If steel tanks are used for these purposes, they are still generally referred to as pits.
Mud weight: A measure of the density of a drilling fluid expressed as pounds per gallon, pounds per cubic foot, or kilograms per cubic metre. Mud weight is directly related to the amount of pressure the column of drilling mud exerts at the bottom of the hole.
Multiple completion: An arrangement for producing a well in which one wellbore penetrates two or more petroleum-bearing formations.
N
Natural gas: A highly compressible, highly expansible mixture of hydrocarbons and small amounts of various nonhydrocarbons (such as carbon dioxide, helium, hydrogen sulfide, and nitrogen) which have a low specific gravity and occur naturally in a gaseous form or in solution with crude oil in natural underground reservoirs.
Natural gas liquids (NGL): Portions of natural gas that are liquefied at the surface in separators or gas processing plants, leaving dry natural gas. NGLs include ethane, propane, butane, natural gasoline, and condensate.
Net Revenue Interest (NRI): The percentage of revenues from a property an interest holder is due, calculated as 100% minus royalties or other burdens on the property. Example: A landowner leases his mineral rights to an oilman. The landowner retains a royalty of 1/8 (=12.5%); his net revenue interest is 12.5%. The oilman's net revenue interest would be 87.5% (=100% - 12.5%).
Nipple: A tubular pipe fittinG threaded on both ends used for making connections between pipe joints and other tools.
Normal circulation: The smooth, uninterrupted circulation of drilling fluid down the drill stem, out the bit, up the annular space between the pipe and the hole, and back to the surface.
O
Offering memorandum: A legal document provided to potential investors in a venture describing the terms under which the investment is being offered.
Offset well: A well drilled near the discovery well designed to produce more oil and/or gas from a reservoir. An offset well also will sometimes be drilled to keep oil and gas from draining from one tract of land to another where a well is being drilled or is already producing.
Oil: A simple or complex liquid mixture of hydrocarbons that can be refined to yield gasoline, kerosene, diesel fuel, and various other products.
Oilfield: The surface area overlying an oil reservoir or reservoirs. The term usually includes not only the surface area, but also the reservoir, the wells, and the production equipment.
Oilfield services: Service companies that do work in and for the oilfield. These services may include: cementing, perforating, trucking, and logging, among others.
Oil in place: The crude oil estimated to exist in a field or a reservoir. Oil in the formation not yet produced.
Oil string: The final string of casing set in a well after the productive capacity of the formation has been determined to be sufficient. Also called the long string or production casing.
Oilwell: A well from which oil is obtained.
Oil zone: A formation or horizon of a well from which oil may be produced. The oil zone is usually immediately under the gas zone and on top of the water zone if all three fluids are present and segregated.
On pump: A phrase used in reference to a well that does not flow from natural reservoir energy but is produced by means of a pump.
Open formation: A petroleum-bearing rock with good porosity and permeability.
Open hole: A wellbore in which casing has not been set, or an open or cased hole in which no drill pipe or tubing is suspended.
Open-hole completion: A method of preparing a well for production in which no production casing or liner is set opposite the producing formation. Reservoir fluids flow unrestricted into the open wellbore.
Operator: The person or company, either proprietor or lessee, actually responsible for the drilling, completion and production operations of a well, and the physical maintenance of the leased property. Some of the specific functions (drilling, cementing, fracing, etc.) are frequently contracted to other service companies, but the operator retains ultimate responsibility.
Organization of Petroleum Exporting Countries (OPEC): An organization of the countries of the Middle East, Africa, and South America that produce oil and export it. OPEC members include Algeria, Angola, Ecuador, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, the United Arab Emirates, and Venezuela. The organization's purpose is to negotiate and regulate production and oil prices.
Overriding Royalty (ORRI): A revenue interest in oil and gas, created out of a working interest. Like the lessor's royalty, it entitles the owner to a share of the proceeds from gross production, free of any operating or production costs.
P
Packer: A piece of downhole equipment that consists of a sealing device, a holding or setting device, and an inside passage for fluids.
Paraffin: A saturated aliphatic hydrocarbon having the formula CnH2n+2 (for example, methane, CH4; ethane, C2H6). Heavier paraffin hydrocarbons (for example, C18H38) form a waxlike substance that is called paraffin. These heavier paraffins often accumulate on the walls of tubing and other production equipment, restricting or stopping the flow of the desirable lighter paraffins.
Pay zones: The vertical portion of a reservoir that is producing oil and gas within a given wellbore. Pay zones can vary in thickness from one foot to several hundred feet.
Payoff: The point in time at which a well's operation begins to produce revenues.
Payout: The amount of time it takes to recover the capital investment made on a well or drilling program.
Perforate: To pierce the casing wall and cement of a wellbore to provide holes through which formation fluids may enter or to provide holes in the casing so that materials may be introduced into the annulus between the casing and the wall of the borehole.
Perforated completion: A well completion method in which the producing zone or zones are cased, cemented, and perforated to allow fluid flow into the wellbore.
Perforating gun: An instrument used to perforate a well. The perforating gun contains explosive charges that, after being lowered into cased well, are electronically detonated from the surface.
Perforation: A hole made in the casing, cement, and formation through which formation fluids enter a wellbore. Usually several perforations are made at a time.
Permeability: A measure of the ease with which a fluid flows through the connecting pore spaces of a formation or cement. The unit of measurement is the millidarcy. The term also refers to the ability of a fluid to flow within the interconnected pore network of a porous medium.
Petroleum: A substance occurring naturally in the earth in solid, liquid, or gaseous state and composed mainly of mixtures of chemical compounds of carbon and hydrogen, with or without other nonmetallic elements such as sulfur, oxygen, and nitrogen.
Pipe: A long, hollow cylinder, usually steel, through which fluids are conducted. Oilfield tubular goods are casing (including liners), drill pipe, tubing, or line pipe.
Pipeline: A tube or system of tubes used for the transportation of oil or gas.
Pit level: Height of drilling mud in the mud tanks, or pits.
Plug: Any object or device that blocks a hole or passageway (such as a cement plug in a borehole).
Plug and abandon (P&A): To place cement plugs into a dry hole and abandon it.
Plug back: To place cement in or near the bottom of a well to exclude bottom water, to sidetrack, or to produce from a formation higher in the well.
Pool (noun): An underground reservoir that contains a common accumulation of oil and natural gas. A zone of a structure which is completely separated from any other zone in the same structure is a pool.
Pool (verb): To combine two or more tracts of land into one unit for drilling purposes.
Pooling: The bringing together of small tracts sufficient for the granting of a well permit under applicable spacing rules. The term is frequently used interchangeably with "Unitization."
Porosity: The ratio of the volume of empty space to the volume of solid rock in a formation, indicating how much fluid a rock can hold.
Possible reserves: Areas in which production of crude oil or gas is presumed possible, owing to geological inference.
Present net value: The present value of money to be received at some specified time in the future, discounted back to the present at a specified interest rate.
Primary recovery: The first stage of oil production in which the natural reservoir pressure drives the recovery of oil, although some form of artificial lift may be required to exploit declining reservoir pressures.
Primary term: The basic period of time during which a lease is in effect.
Private Placement Offering: An investment offering not intended for the general public.
Probable reserves: Areas which have not been proven to contain oil or natural gas, but are presumed capable of production because of geological inference; for instance, the area's proximity to proven reserves in the same reservoir.
Production: The phase of the petroleum industry that deals with bringing the well fluids to the surface and separating them and storing, gauging, and otherwise preparing the product for delivery. Also, the amount of oil or gas produced in a given period.
Production test: A test of the well's producing potential usually done during the initial completion phase.
Production well: In fields in which improved recovery techniques are being applied, the well through which oil is produced.
Productivity test: A combination of a potential test and a bottomhole pressure test the purpose of which is to determine the effects of different flow rates on the pressure within the producing zone of the well to establish physical characteristics of the reservoir and to determine the maximum potential rate of flow.
Propping agent (proppant): A granular substance (sand grains, aluminum pellets, or other material) that is carried in suspension by the fracturing fluid and that serves to keep the cracks open when fracturing fluid is withdrawn after a fracture treatment.
Prospect (noun): A lease or group of leases on which an operator intends to drill.
Proved behind-pipe reserves: Estimates of the amount of crude oil or natural gas which would be recoverable by recompleting existing wells.
Proved developed producing reserves (PDP): Estimates of the amount of oil or natural gas which is recoverable from existing wells with existing facilities from open, producing payzones.
Proved reserves: Estimates of the amount of oil or natural gas believed to be recoverable from known reservoirs.
Proved undeveloped reserves (PUD): Estimates of the amount of oil or natural gas that could be recovered by drilling new wells, deepening existing
Public Offering: An investment offering intended for sale to the general public. It must be register with the Securities and Exchange Commission of the Federal government and the securities-regulating agencies of the various states in which it will be offered.
Pump: A device that increases the pressure on a fluid or raises it to a higher level.
Pumping unit: The machine that imparts reciprocating motion to a string of sucker rods extending to the positive displacement pump at the bottom of a well. It is usually a beam arrangement driven by a crank attached to a speed reducer, coupled to a motor.
Pump jack: A surface unit similar to a pumping unit but having no individual power plant.
Pump rate: The speed, or velocity, at which a pump is run. In drilling, the pump rate is usually measured in strokes per minute.
R
Radioactivity well logging: The recording of the natural or induced radioactive characteristics of subsurface formations. A radioactivity log, also known as a radiation log or a nuclear log, normally consists of two recorded curves: a gamma ray curve and a neutron curve. Both help to determine the types of rocks in the formation and the types of fluids contained in the rocks.
Ram: The closing and sealing component on a blowout preventer.
Rate of penetration (ROP): A measure of the speed at which the bit drills into formations, usually expressed in feet per hour or minutes per foot.
Rathole : A hole in the rig floor, some 30 to 40 feet deep, which is lined with casing that projects above the floor, into which the kelly and the swivel are placed when hoisting operations are in progress.
Ream: To enlarge the wellbore by drilling it again with a special bit.
Reamer: A tool used in drilling to smooth the wall of a well, enlarge the bore hole, help stabilize the bit, straighten the wellbore, and drill directionally.
Reciprocating motion: Back-and-forth or up-and-down movement, such as that of a piston in a cylinder.
Reciprocating pump: A pump consisting of a piston that moves back and forth or up and down in a cylinder.
Recompletion: After the initial completion of a well, the action and techniques of reentering the well and redoing or repairing the original completion to restore the well's productivity.
Reserve pit: A mud pit in which a supply of drilling fluid is stored.
Reserves: The unproduced but recoverable oil or gas in a formation that has been proved by production.
Reserve tank: A special mud tank that holds mud that is not being actively circulated. A reserve tank usually contains a different type of mud from that which the pump is currently circulating. For example, it may store heavy mud for emergency well-control operations.
Reservoir: A subsurface, porous, permeable rock body containing quantities of oil or gas, which is surrounded by layers of less permeable or impervious rock. The four basic types of hydrocarbon reservoirs are oil, volatile oil, dry gas, and gas condensate. An oil reservoir generally contains three fluids-gas, oil, and water-with oil the dominant product. In the typical oil reservoir, these fluids become vertically segregated with gas, the lightest, occupying the upper part of the reservoir rocks; water, the lower part; and oil, the intermediate section. In addition to its occurrence as a cap or in solution, gas may accumulate independently of the oil; if so, the reservoir is called a gas reservoir.
Reservoir drive: The process in which reservoir fluids are caused to flow out of the reservoir rock and into a wellbore by natural energy. Gas drive depends on the fact that, as the reservoir is produced, pressure is reduced, allowing the gas to expand, providing the principal driving energy.
Reservoir oil: Oil in place in the reservoir; retained in a reservoir as residual gas saturation is an inverse function of the pressure, due to the physics of gas.
Reservoir pressure: The average pressure within the reservoir at any given time. Determination of this value is best made by bottomhole pressure measurements with adequate shut-in time.
Reservoir rock: A permeable rock that may contain oil or gas in appreciable quantity and through which petroleum may migrate.
Retained Interest: The portion (or fraction) of an interest in a property the owner of such interest retain when conveying the balance of the interest to another party.
Reversionary interest: An interest in a well or property that becomes effective at a certain time in the future or on the occurrence of a specific future event.
Rework: To restore production from an existing formation when it has fallen off substantially or ceased altogether.
Rig: The derrick or mast, drawworks, and attendant surface equipment of a drilling or workover unit.
Rig down: To dismantle a drilling rig and auxiliary equipment following the completion of drilling operations. Also called tear down.
Rotary: The machine used to impart rotational power to the drill stem while permitting vertical movement of the pipe for rotary drilling. Modern rotary machines have a special component, the rotary or master bushing, to turn the kelly bushing, which permits vertical movement of the kelly while the stem is turning.
Rotary drilling: A drilling method in which a hole is drilled by a rotating bit to which a downward force is applied.
Roughneck: A worker on a drilling or workover rig, subordinate to the driller, whose primary work station is on the rig floor. Sometimes called floorhand, floorman, rig crew member, or rotary helper.
Round trip: The procedure of pulling out and subsequently running back into the hole a string of drill pipe or tubing. Also called tripping.
Roustabout: A semi-skilled hand who looks after producing wells and production facilities.
Royalty: A payment to a landowner or mineral rights owner by a leaseholder on each unit of resources produced.
Run casing: To lower a string of casing into the hole. Also called to run pipe.
Run in: To go into the hole with tubing, drill pipe, and so forth.
Run pipe: To lower a string of casing into the hole. Also called to run casing.
S
Samples: The well cuttings obtained at designated footage intervals during drilling. From an examination of these cuttings, the geologist determines the type of rock and formations being drilled and estimates oil and gas content. Also, small quantities of well fluids obtained for analysis.
Sand control: Any method by which large amounts of sand in a sandy formation are prevented from entering the wellbore. Sand in the wellbore can cause plugging and premature wear of well equipment.
Sandfrac: Method of fracturing subsurface rock formations by injecting fluid and sand under high pressure to increase permeability. Fractures are kept open by the grains of sand.
Sandstone: A sedimentary rock composed of individual grains of the mineral quartz between 0.002 and 0.079 inches in diameter and cemented together by silica, calcite, iron oxide, and so forth.
Saturation: The extent to which the pore space in a formation contains hydrocarbons or connate water; or, the extent to which gas is dissolved in the liquid hydrocarbons in a formation.
Secondary recovery: The first improved recovery method of any type applied to a reservoir to produce oil not recoverable by primary recovery methods. Most frequently it entails the introduction of water or gas into a well to supplement the natural reservoir drive and force additional oil to the producing wells.
Section: A square tract of land having an area of one square mile (=640 acres). There are 36 sections in a township.
Sedimentary basin: A large land area composed of unmetamorphized sediments. Oil and gas commonly occur in such formations.
Sedimentary rock: Rock formed by the deposition of sediment, usually in a marine environment. Sedimentary rock is the foremost rock type which composes oil and gas reservoirs.
Seismic exploration: A method of exploring for oil or gas by sending shock waves into the earth. Different rocks transmit, reflect, or refract sound waves at different speeds, so when vibrations at the surface send sound waves into the earth in all directions, they reflect to the surface at a distance and angle from the sound source that indicates the depth of the interface. These reflections are recorded and analyzed to map underground formations.
Seismograph: A device that records natural or manmade vibrations from the earth. Geologists read what it has recorded to evaluate the oil potential of underground formations.
Service company: A company that provides a specialized service, such as a well-logging service or a directional drilling service.
Service well: A nonproducing well used for injecting liquid or gas into the reservoir for enhanced recovery; also, a saltwater disposal well or a water supply well.
Set casing: To run and cement casing at a certain depth in the wellbore. Sometimes called set pipe.
Severance tax: Tax paid to the state government by producers of oil or gas in the state.
Shale: A fine-grained sedimentary rock composed mostly of consolidated clay or mud. Shale is the most frequently occurring sedimentary rock.
Shale shaker: A vibrating screen used to remove cuttings from the circulating fluid in rotary drilling operations. Also called a shaker.
Show: An indication of the presence of oil or gas in a formation which is observed and recorded during the drilling of a well.
Shut-down well: To shut down a well is to halt initial drilling operations for one reason or another.
Shut in: To shut in a well is to close the valves so that the well stops producing; also, to close in a well in which a kick has occurred.
Shut-in bottomhole pressure (SIBHP): The pressure at the bottom of a well when the surface valves on the well are completely closed. It is caused by formation fluids at the bottom of the well.
Solution gas: Natural gas which is dissolved in oil in a reservoir, and which bubbles out of the oil on the surface as pressures decline during production.
Sour Crude or Gas: Oil or natural gas which has a high sulfur content, notably hydrogen sulfide (H2S) which is a deadly poisonous gas.
Source rock: A sedimentary rock containing organic matter which has been transformed into oil and/or gas.
Spacing: The legal distances established by state regulatory authorities which must exist between wells drilled in a specific reservoir.
Spot market: A short-term contract for the purchase and sale of commodities (such as oil and gas) at a specific price.
Spud (spud date): To start drilling a well. The spud date is the day drilling operations begin.
Stipper oil well: A well that is barely profitable, generally capable of producing less than 10 barrels of oil per day.
Stratigraphic trap: A petroleum trap formed during the deposition of the reservoir rock, such as a limestone reef, or by erosion of the reservoir rock.
Structural trap: A petroleum trap created by the deformation of the reservoir rock such as a fold or fault.
Supervisory fee: A fee paid to the general partner in and oil and gas limited partnership for the general partner's duties of directly supervising operations at the well site.
Swab: To remove fluids from a well with a swabbing tool.
Sweet crude: Crude oil which has a very low sulfur content. It is generally more valuable than sour crude because it is more easily refined and processed.
T
Take-or-pay contract: A (long-term) contract between a gas producer and a gas purchaser, such as a pipeline transmission company.
Tally: To measure andrecord the total length of pipe, casing, or tubing that is to be run in a well.
TCF (abbreviation): Trillion cubic feet.
TD (abbreviation): Total depth.
Tertiary recovery: The recovery of oil that involves complex and very expensive methods that not only restore formation pressure but also improve oil displacement or fluid flow in the reservoir. TR methods include the injection of steam, chemicals, gases, or heat. Differs from primary recovery, which involves depleting a naturally flowing reservoir, or secondary recovery, which usually involves repressuring or waterflooding.
Thermal recovery: A type of improved recovery in which heat is introduced into a reservoir to lower the viscosity of heavy oils and to facilitate their flow into producing wells.
Tight formation: A layer of sedimentary rock with low porosity and permeability, thus greatly hindering the flow of gas through the .
Tight sand: Sand or sandstone formation with low permeability. Gas produced from a formation so designated by the Federal Energy Regulatory Commission qualifies for a higher market price.
Tight spot: A section of a borehole in which excessive wall cake has built up, reducing the hole diameter and making it difficult to run the tools in and out.
Time value of money: The concept that a dollar in hand today is worth more than a dollar that will be received in some future year.
Title: The combination of factors that, together, constitute legal ownership of a property.
Tongs: The large wrenches used for turning when making up or breaking out drill pipe, casing, tubing, or other pipe; variously called casing tongs, rotary tongs, and so forth according to the specific use.
Toolpusher: An employee of a drilling contractor who is in charge of the entire drilling crew and the drilling rig. Also called a rig superintendent, drilling foreman, or rig supervisor.
Top drive: A device similar to a power swivel that is used in place of the rotary table to turn the drill stem.
Top plug: A cement wiper plug that follows cement slurry down the casing. It goes before the drilling mud used to displace the cement from the casing and separates the mud from the slurry. See cementing, wiper plug.
Top lease: A (conditional) type of lease that may be granted by the mineral-rights owner of a property while a lease that already exists on that property nears expiration, but is still in effect. The top lease becomes effective only if and when the existing lease expires (or is terminated).
Torque: The turning force that is applied to a shaft or other rotary mechanism to cause it to rotate or tend to do so. Torque is measured in foot-pounds, joules, newton-metres, and so forth.
Total depth (TD): The maximum depth reached in a well.
Township: A square tract of land six miles on a side, it consists of 36 sections of one square mile each.
Tracer: A substance added to reservoir fluids to permit the movements of the fluid to be followed or traced. When samples of the water or gas taken some distance from the point of injection reveal signs of the tracer, the route of the fluids can be mapped
Tracer log: A survey that uses a radioactive tracer such as a gas, liquid, or solid having a high gamma ray emission. When the material is injected into any portion of the wellbore, the point of placement or movement can be recorded by a gamma ray instrument.
Trap: A natural configuration of layers of rock where non-porous or impermeable rocks acts as a barrier, blocking the natural upward flow of hydrocarbons.
Traveling block: An arrangement of pulleys, or sheaves, through which drilling cable is reeved, which moves up or down in the derrick or mast.
Travis Peak (TP): A Lower Cretaceous sedimentary formation which sits atop the Upper Cotton Valley formation at roughly 8 thousand to 10 thousand feet deep in the East Texas Basin, extending into Louisiana. The Travis Peak is composed of tight sandstones which require extensive stimulation, yet yield prolific amounts of gas when properly stimulated.
Trip: The operation of hoisting the drill stem from and returning it to the wellbore; or, as a verb, to insert or remove the drill stem into or out of the hole. Shortened form of "make a trip."
Trip in: To go in the hole.
Trip out: To come out of the hole.
Tubing: Relatively small-diameter pipe that is run into a well to serve as a conduit for the passage of oil and gas to the surface.
Turnkey: A drilling contract that calls for a drilling contractor to drill a well, for a fixed price, to a specified depth. The purpose of drilling a well by turnkey contract may be related to the timing of Federal income tax deductions.
U
Unassociated gas: Natural gas that occurs alone, not in solution or as free gas with oil or condensate.
Uncased hole: See open hole.
Unconsolidated sandstone: A sand formation in which individual grains do not adhere to one another. If an unconsolidated sandstone produces oil or gas, it will produce sand as well if not controlled or corrected.
Unit operator: The oil company in charge of development and production in an oilfield in which several companies have joined to produce the field.
Updip well: A well located high on a structure where the oil-bearing formation is found at a shallower depth.
Upstream: Activities concerned with finding petroleum and producing it, compared to downstream which are all the operations that take place after production.
V
Valve: A device used to control the rate of flow in a line to open or shut off a line completely, or to serve as an automatic or semiautomatic safety device. Those used extensively include the check valve, gate valve, globe valve, needle valve, plug valve, and pressure relief valve.
Vapor pressure: The pressure exerted by a vapor held in equilibrium with its solid or liquid state.
Viscosity: A fluid's resistance to flowing.
W
Walking beam: The horizontal steel member of a beam pumping unit that has rocking or reciprocating motion.
Water drive: The reservoir drive mechanism in which oil is produced by the expansion of the underlying water and rock, which forces the oil into the wellbore.
Waterflooding: A secondary recovery method in which water is injected into a reservoir to force additional oil into the wells.
Well: The hole made by the drilling bit, which can be open, cased, or both. Also called borehole, hole, or wellbore.
Wellbore: A borehole; the hole drilled by the bit. A wellbore may have casing in it or it may be open (uncased); or part of it may be cased, and part of it may be open. Also called a borehole or hole.
Well completion: The activities and methods of preparing a well for the production of oil and gas or for other purposes, such as injection; the method by which one or more flow paths for hydrocarbons are established between the reservoir and the surface.
Well control: The methods used to control a kick and prevent a well from blowing out. Such techniques include, but are not limited to, keeping the borehole completely filled with drilling mud of the proper weight or density during operations, exercising reasonable care when tripping pipe out of the hole to prevent swabbing, and keeping careful track of the amount and weight of mud put into the hole to replace the volume of pipe removed from the hole during a trip.
Well fluid: The fluid, usually a combination of gas, oil, water, and suspended sediment, that comes out of a reservoir. Also called well stream.
Wellhead: The equipment installed at the surface of the wellbore. A wellhead includes such equipment as the casinghead and tubing head. adj: pertaining to the wellhead.
Well logging: The recording of information about subsurface geologic formations, including records kept by the driller and records of mud and cutting analyses, core analysis, drill stem tests, and electric, acoustic, and radioactivity procedures.
Well program: The procedure for drilling, casing, and completing a well.
Well servicing: The maintenance work performed on an oil or gas well to improve or maintain the production from a formation already producing. It usually involves repairs to the pump, rods, gas-lift valves, tubing, packers, and so forth.
Well stimulation: Any of several operations used to increase the production of a well, such as acidizing or fracturing. See acidize.
West Texas Intermediate: Refers to a grade of crude oil produced in the Permian and Midland basin areas of west Texas. The price paid for crude oil varies according to quality.
Wet gas: Natural gas containing liquid hydrocarbons - commonly condensate.
Whipstock: A steel blocking device place in a borehole. As drilling is resumed, the whipstock forces the drill bit to veer off at a slight angle.
Wildcat: An exploration well drilled in an area where no oil or gas has previously been produced.
Wildcatter: An operator who drills the first well in unproven territory.
Wireline: A slender, rodlike or threadlike piece of metal usually small in diameter, that is used for lowering special tools (such as logging sondes, perforating guns, and so forth) into the well. Also called slick line.
WOB (abbreviation): weight on bit.
WOC (abbreviation): waiting on cement; used in drilling reports.
Working interest: An interest created by the execution of an oil and gas lease. It obligates the interest holder to bear the cost of drilling, completing, and producing oil or gas on a tract of land, and provides the interest holder all revenues attributable to production on a lease, less payments of royalty interests.
Workover: The performance of one or more of a variety of remedial operations on a producing well designed to increase production.
Workover rig: A portable rig used for working over a well.
XYZ
Zone: A specific interval or layer of rock layer identified by a certain geologic, chemical, and microfossil characteristics which may contain one or more reservoirs.
Acknowledgements:
Oil and Gas Well Drilling & Servicing eTool; Occupational Safety & Health Administration
Money in the Ground; John Orban, III
Nontechnical Guide to Petroleum, Geology, Exploration, Drilling, and Production; Norman Hyne,Ph.D.
