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Glossary of Oil & Gas Terms

Glossary of Oil & Gas Terms


Underlined Terms are accompanied by a photo. click to view


Volume Abbreviations Natural Gas

Natural Gas

Mcf: one thousand cubic feet of natural gas
Mmcf: one million cubic feet of natural gas
Bcf: one billion cubic feet of natural gas
Tcf: one trillion cubic feet of natural gas
Mmcf/d: millions of cubic feet of gas per day

Energy equivalents

Boe: barrel of oil (one barrel of oil equals 6,000 cubic feet of natural gas)
Mboe: one thousand barrels of oil equivalent
Mmboe: one million barrels of oil equivalent
Mmcfe: one million cubic feet of natural gas equivalent
Bcfe: one billion cubic feet of natural gas equivalent
Tcfe: one trillion cubic feet of natural gas equivalent: one million cubic feet of natural gas


abandonment converting a drilled well to a condition that can be left indefinitely without further attention and will not damage freshwater supplies, potential petroleum reservoirs or the environment.

abiogenic theory – a theory that maintains petroleum originated from hydrocarbons that were trapped inside the Earth during the planet’s formation and are slowly moving upwards.

acidizing the injection of acids under pressure into the rock formation to create channels that allow the hydrocarbons to flow more easily into the wellbore.

air drilling the use of compressed air instead of mud as a drilling fluid to remove the cuttings; air drilling increases penetration rates but offers no control over water in the subsurface formations or downhole gas pressure.

annulus – the space between two concentric lengths of pipe or between pipe and the hole in which it is located.

associated gas – gas that is produced from the same reservoir along with crude oil, either as free gas or in solution.


Barnett Shale - A geologic formation of sedimentary rock that contains natural gas. It is located about a mile and a half underground and is primarily located in Tarrant, Johnson and Dallas counties covering 5,000 square miles.

benzene - a volatile organic compound that occurs naturally in petroleum and is also produced by the combustion of petroleum products.

biogenic theory – the most widely accepted theory explaining the origins of petroleum: as organic materials become deeply buried over time, heat and pressure transform them into hydrocarbons.

bitumen petroleum that exists in the semisolid or solid phase in natural deposits

blowout - an uncontrolled flow of gas, oil or other fluids from a well.

BTU - British Thermal Unit - The amount of energy required to raise the temperature of one pound of water by one Fahrenheit degree. One BTU is equivalent to 252 calories, 0.293 watt-hours or 1,055 joules.


carbon dioxide (CO2) – a non-toxic gas produced from decaying materials, respiration of plant and animal life, and combustion of organic matter, including fossil fuels; carbon dioxide is the most common greenhouse gas produced by human activities.

carbonate rock formed from the hard parts of marine organisms mainly consisting of calcite, aragonite and dolomite.

casing-head gasoline (naphtha) – a highly volatile liquid which is separated from natural gas at the wellhead and was once used as unrefined gasoline.

cat cracking (catalytic cracking) – a refinery process that uses catalysts in addition to pressure and heat to convert heavier fuel oil into lighter products such as gasoline and diesel fuel.

catalysts - materials that assist chemical reactions.

cathodic protection a technique for preventing corrosion in metal pipelines and tanks that uses weak electric currents to offset the current associated with metal corrosion.

CCF - One Hundred Cubic Feet - One CCF is one hundred cubic feet of natural gas at standard distribution pressure of 14.73 pounds per square inch and 60° Fahrenheit.

centrifugal pump a rotating pump, commonly used for large-volume oil and natural gas pipelines, that takes in fluids near the centre and accelerates them as they move to the outlet on the outer rim.

christmas tree - The arrangement of pipes and valves at the wellhead to control the flow of oil or natural gas and to prevent blowouts. (See Wellhead)

clastic made up of pieces (clasts) of older rock; rock derived from mechanical process; generally sandstone, siltstone or shale.

CNG - Compressed Natural Gas

coal bed methane (CBM) natural gas generated and trapped in coal seams.

coal gas a mixture of hydrogen, carbon monoxide and methane, produced by distilling coal, that was once used for heating and lighting.

co-generation – the production of steam to drive turbines producing electrical energy for plant use or sale and for the provision of heat for buildings and industrial processes.

coiled tubing a continuous, jointless hollow steel cylinder that is stored on a reel and can be uncoiled or coiled repeatedly as required; coiled tubing is increasingly being used in well completion and servicing instead of traditional tubing, which is made up of joined sections of pipe.

coke solid carbon that remains in the refining process after cracking of hydrocarbons.

coking – a process used to break down heavy oil molecules into lighter ones by removing the carbon which remains as a coke residue.

common depth point method a method of recording and processing seismic signals so that signals belonging to the same subsurface point are brought together

completion – the process of finishing a well so that it is ready to produce oil or gas.

compressor a machine used to boost natural gas pressure to move it through pipelines or other facilities.

compressor station - Stations located along natural gas pipelines which recompress gas to ensure an even flow.

condensate – hydrocarbons, usually produced with natural gas, that are liquid at normal pressure and temperature.

conventional crude oil – petroleum found in liquid form, flowing naturally or capable of being pumped without further processing or dilution.

conventional resource - Any area where natural gas can be drilled and extracted vertically.

core – a continuous cylinder of rock, usually from five to 10 centimetres in diameter, cut from the bottom of a wellbore as a sample of an underground formation.

cracking – a refining process for increasing the yield of gasoline from crude oil; cracking involves breaking down the larger, heavier and more complex hydrocarbon molecules into simpler and lighter molecules through the use of heat and pressure, and sometimes a catalyst.

critical sour gas wells – a sour gas well that has the potential to release unsafe levels of hydrogen sulphicle, which might affect nearby residents.

critical zone – the zone in a well where sour gas will likely be encountered

crown rights - government-owned surface or mineral rights.

cubic foot - The amount of natural gas required at room temperature at sea level to fill a volume of one cubic foot.

cuttings chips and small fragments of rock cut by the drill bit and brought to the surface by the flow of drilling mud.


density - the heaviness of crude oil, indicating the proportion of large, carbon-rich molecules, generally measured in kilograms per cubic metre (kg/M3) or degrees on the American Petroleum Institute (API) gravity scale; in Western Canada oil up to 900 kg/m3 is considered light to medium crude - oil above this density is deemed as heavy oil or bitumen.

derrick/drilling Rig - A steel structure mounted over the borehole to support the drill pipe and other equipment that is lowered and raised during drilling operations.

development well – a well drilled in or adjacent to a proven part of a pool to optimize petroleum production

directional drilling - A technique that enables drilling at an angle to reach a particular underground formation.

DOE - Department of Energy
A cabinet-level federal agency created in 1977 to replace the Federal Energy Administration. The DOE manages national energy policy, nuclear power and nuclear weapons programs, and the national energy research labs.

dolomite calcium carbonate-rich sedimentary rock in which oil or gas reservoirs are often found

downstream – the refining and marketing sector of the petroleum industry.

drilling mud fluid circulated down the drill pipe and up the annulus during drilling to remove cuttings, cool and lubricate the bit, and maintain desired pressure in the well

drilling permit - Authorization from a regulatory agency to drill a well.

drillbit - Tool used in drilling to break up rock mechanically in order to penetrate the subsoil. The bit drills a circular hole.

dry gas – natural gas from the well that is free of liquid hydrocarbons, or gas that has been treated to remove all liquids; pipeline gas

dry hole – an unsuccessful well; a well not capable of producing commercial quantities of oil or gas


EIA - Energy Information Administration
An agency within the U.S. Department of Energy. EIA provides energy data, forecasts and analyses.  

enhanced recovery the increased recovery from a pool achieved by artificial means, including injection of fluids, chemicals or heat.

established reserves – those reserves recoverable under current technology and present and anticipated economic conditions.


field – the geographical area encompassing a group of one or more underground petroleum pools sharing the same or related infrastructure.

field price – the amount received by petroleum producers after deducting transportation and distribution costs.

flaring - The controlled and safe burning of gas which cannot be used for commercial or technical reasons.

formation – a designated subsurface layer that is composed throughout of substantially the same kind of rock or rock types.

fracturing (or fracing) - hydraulic fracturing or hydraulic fracking - The pumping of a media, typically water, sand and chemical additives, into a reservoir with a controlled force to fracture reservoir rock, resulting in a greater flow of natural gas or oil from the reservoir.


gas processing plant - A facility which extracts liquefiable hydrocarbons or sulfur from natural gas and/or fractionates a liquid stream.

gas transmission systems – pipelines that carry natural gas at high pressure from producing areas to consuming areas.

gathering - The process of collecting natural gas flowing from numerous wells and bringing it together into pooling areas where it is received into transmission pipelines

gathering lines – pipelines that move raw petroleum from wellheads to processing plants and transmission facilities.

geochemistry – the science of chemistry applied to rocks and minerals; geochemists analyze the contents of subsurface rocks for the presence of organic matter associated with oil deposits.

geophones (or jugs) – sensitive vibration-detecting instruments used in conducting seismic surveys; marine versions are known as hydrophones.

geophysics – the science that deals with the relations between the physical features of the Earth and forces that produce them; geophysics includes the study of seismology and magnetism.

GGE - Gasoline Gallon Equivalent

greenhouse effect the warming of the Earth’s surface caused by the presence of carbon dioxide and other gases in the atmosphere that trap the heat of the sun.

greenhouse gases – a wide variety of gases that trap heat near the Earth’s surface, preventing its escape into space; greenhouse gases, such as carbon dioxide, methane, nitrous oxide and water vapour, occur naturally or result from human activities such as the burning of fossil fuels ground-level ozone - see volatile organic compounds.

gusher a well that comes in with such great pressure that the oil or gas blows out of the wellhead like a geyser; gushers are rare today because of improved drilling technology, especially the use of drilling mud to control downhole pressure.


Haynesville Shale - A geologic formation containing natural gas located in Northwest Louisiana and East Texas. The Haynesville has been estimated to be the largest natural gas field in the continental U.S. with an estimated 250 trillion cubic feet of recoverable gas.

heavy oil – dense, viscous oil, with a high proportion of bitumen, that is difficult to extract with conventional techniques and is more costly to refine.

horizontal drilling drilling a well which deviates from the vertical and travels horizontally through a producing layer.

horizontal laterals – a series of drainage wells branching off from a horizontal wellbore.

hydrocarbons – a large class of liquid, solid or gaseous organic compounds, containing only carbon and hydrogen, that are the basis of almost all petroleum products.

hydrocracking a refining process which adds hydrogen to the carbon rich molecules of heavier oil, in the presence of a catalyst, to produce high-octane gasoline.

hydrogen sulphide (H2S) – a naturally occurring, highly toxic gas with the odour of rotten eggs.

hydro-transport – a process that uses hot water to transport oil sand through a pipeline to a processing plant.

hydrotreating the process of adding hydrogen to heavy oil or bitumen molecules during the upgrading process.


infill drilling – wells drilled between established producing wells on a lease in order to increase production from the reservoir.

injection well a well used for injecting air, steam or fluids into an underground formation


jarmout – an agreement between oil companies whereby the owner of a lease who is not interested in drilling at the time agrees to assign the lease or a portion of it to another company that will earn a share of production by under-taking exploration.


kerosene - a mixture of hydrocarbons produced by distilling petroleum, that is used as a lamp oil or jet fuel.

kick – when fluids with a higher pressure than that exerted by the drilling mud enter the wellbore; this creates the potential for a well to blow out of control.


landman – a member of the exploration team whose primary duties are formulating and carrying out exploration strategies and managing an oil company’s relations with its landowners and partners, including securing and administering oil and gas leases and other agreements.

LDC - Local Distribution Company

light crude oil - liquid petroleum which has freely at room temperature.

limestone- calcium carbonate-rich sedimentary rocks in which oil or gas reservoirs are often found.

liquified natural gas (LNG) - supercooled natural gas that is maintained as a liquid at - 160′ Celsius; LNG occupies 1/640th of its original volume and is therefore easier to transport if pipelines cannot be used.

liquefied petroleum gas (LPG) - Propane, butane or propane-butane mixtures derived from crude oil refining or natural gas fractionation. For convenience of transportation, these gases are liquefied through pressurization.

logs – detailed depth-related records of certain significant details of an oil or gas well; usually obtained by lowering measurement instruments into a well.


Marcellus Shale - A geologic formation containing natural gas, which extends throughout much of the Appalachian Basin. It is located primarily in southern New York, Pennsylvania and West Virginia

measurement-while-drilling (MWD) tool – technology that transmits information from downhole measuring devices to the surface while drilling is ongoing.

medium crude oil – liquid petroleum with a density between that of light and heavy crude oil.

methane (CH4) - the simplest hydrocarbon and the main component of natural gas; methane is also produced when organic matter decomposes.

midstream – the processing, storage and transportation sector of the petroleum industry.

mineral interest - An ownership of the minerals beneath a tract of land. If the surface ownership and the mineral ownership are different, the minerals are said to be “severed.”

mineral rights – the rights to explore for and produce the resources below the surface.

miscible flooding – an oil-recovery process in which a fluid, capable of mixing completely with the oil it contacts, is injected into an oil reservoir to increase recovery.

mousehole a hole drilled to the side of the wellbore to hold the next joint of drill pipe to be used; when this joint is pulled out and screwed onto the drill string, another joint of pipe is readied and slipped into the mousehole to await its turn

mud motor a downhole drilling motor that is powered by the force of the drilling mud pushed through the motor by the mud pumps at the surface.

multiple entry – a technique for drilling several horizontal wells from a single vertical, directional or horizontal wellbore naphtha - a light fraction of crude oil used to make gasoline.


natural gas - A naturally occurring mixture of hydrocarbon and non-hydrocarbon gases found in porous rock formations. Its principal component is methane.

natural gas liquids (NGLs) – liquids obtained during natural gas production and processing; they include ethane, propane, butane and condensate.

NGV - Natural Gas Vehicle

nitrous oxide (N20) – a very potent greenhouse gas which has a large number of natural sources and is a secondary product of the burning of organic material and fossil fuels.


octane – a performance rating of gasoline; the higher the octane number, the greater the anti-knock quality of the gasoline.

oil sands - a deposit of sand saturated with bitumen.

operator – the company or individual responsible for managing an exploration, development or production operation.


PVT - Pit Volume Totalizer - equipment used to measure the volume of drilling mud in the mud tanks/pits.

packer an expanding plug used in a well to seal off certain sections of the tubing or casing when cementing and acidizing or when a production formation is to be isolated

perforate – make holes through the casing opposite the producing formation to allow the oil or gas to flow into the well.

perforating gun a special tool used downhole for shooting holes in the well’s casing opposite the producing formation.

permeability – the capacity of a reservoir rock to transmit fluids; how easily fluids can pass through rock.

petrochemicals – chemicals derived from petroleum that are used as feedstocks for the manufacture of a variety of plastics and other products such as synthetic rubber.

petroleum – a naturally occurring mixture composed predominantly of hydrocarbons in the gaseous, liquid or solid phase.

pig a cylindrical device inserted into a pipeline to inspect the pipe or to sweep the line clean of water, rust or other foreign matter; pipeline inspection and cleaning devices are called pigs because early models squealed as they moved through the pipe.

pinnacle reef – a conical formation, higher than it is wide, usually composed of limestone, in which hydrocarbons might be trapped.

pipeline - A string of interconnected pipe providing a route for natural gas to travel from the wellhead to market. Without pipelines, natural gas cannot be transported and sold at market to provide royalty payments, clean energy and economic benefits to the community.

plug - A permanent plug, usually cement, set in a borehole to block the flow of fluids, to isolate sections of the well or to permanently plug a dry hole or depleted well.

pool – a natural underground reservoir containing an accumulation of petroleum.

pooling - A term frequently used interchangeably with “unitization;” more properly, it refers to the combining of small or irregular tracts into a unit large enough to meet state spacing regulations for drilling permits. “Unitization” is a term used to describe the combined operations of all or some portion of a producing reservoir.

porosity – the volume of spaces within rock that might contain oil and gas (like the amount of water a sponge can hold); the open or void space within rock

Precambrian – formed prior to the Cambrian era approximately 600 million years ago.

primary recovery – the production of oil and gas from reservoirs using the natural energy available in the reservoirs and pumping techniques.

probable reserves – hydrocarbon deposits believed to exist with reasonable certainty on the basis of geological information

processing - The separation of oil, gas and natural gas liquids and the removal of impurities.

production casing the last string of casing set in a well; production casing is tubular steel pipe connected by threads and couplings that lines the total length of the wellbore to ensure safe control of production, prevent water from entering the wellbore and keep rock formations from “sloughing” into the wellbore.

production tubing steel pipe inside the casing used to flow the petroleum from the producing zone to the surface.

productive capacity – the estimated maximum volume which can be produced from known reserves based on reservoir characteristics, economic considerations, regulatory limitations and the feasibility of infill drilling or additional production facilities; also known as available supply.

proved reserves – hydrocarbons in known reservoirs that can be recovered with a great degree of certainty under existing technological and economic conditions.

public consultation – the process of involving all affected parties in the design, planning and operation of a seismic program, an oil and gas well, pipeline, processing plant or other facility.


rathole a slanted hole drilled near the wellbore to hold the kelly joint when not in use; the kelly is unscrewed from the drill string and lowered into the rathole.

recoverable resources – hydrocarbon reserves that can be produced with current technology including those not economical to produce at present.

reservoir (pool) – a porous and permeable underground rock formation containing a natural accumulation of crude oil or natural gas that is confined by impermeable rock or water barriers, and is separate from other reservoirs.

residuum – a heavy, black, tar-like substance that remains after crude oil has been fully refined to distil all usable fractions or components.

rod string – a string of steel rods used to provide up and down motion for a bottom-hole pump to lift oil to the surface.

rotary rig a modern drilling unit capable of drilling a well with a bit attached to a rotating column of steel pipe.

rotary table – a heavy, circular casting mounted on a steel platform just above the rig floor which rotates the drill string and thus turns the bit

royalty - The share of production or proceeds reserved to a mineral owner under the terms of a mineral lease. Normally, royalty interests are free of all costs of production except production taxes and transportation costs. It is established in the lease by reserving a royalty which is usually expressed as a fraction of production.


sandstone a compacted sedimentary rock composed mainly of quartz or feldspar; a common rock in which oil, natural gas and/or water accumulate

SCF - Standard Cubic Feet

secondary recovery – the extraction of additional crude oil, natural gas and related substances from reservoirs through pressure maintenance techniques such as water flooding and gas injection.

sedimentary rocks rocks formed by the accumulation of sediment or organic materials and therefore likely to contain hydrocarbons.

seismic - A tool for identifying underground accumulations of oil or natural gas by sending and measuring the return of energy or sound waves. It is a computer-assisted process that maps sedimentary structures to assist in planning drilling programs.

seismic surveys – refers to studies done to gather and record patterns of induced shock wave reflections from underground layers of rock which are used to create detailed models of the underlying geological structure.

service rig – a truck-mounted rig, usually smaller than a drilling rig, that is brought in to complete a well or to perform maintenance, replace equipment or improve production

shale - rock formed from clay. Gas reserves found in unusually nonporous rock, requiring special drilling and completion techniques.

shale shaker – a vibrating screen for sifting out rock cuttings from drilling mud.

shut in well - A well which is producing or capable of producing but is not produced. Reasons for wells being shut in may be lack of pipeline access to market or economically unfavorable market prices.

sidetrack – a section of a well drilled on a curve to bypass debris or other obstructions

smart pig – sophisticated instrument packages sent through pipelines to test for corrosion and buckling.

sound blanket - A sound blanket or a wall sometimes erected in order to reduce the noise emitted from a drilling rig.

sour gas – natural gas containing hydrogen sulphide in measurable concentrations.

sour oil – crude oil containing free sulphur, hydrogen sulphide or other sulphur compounds

spacing - The distance between wells allowed by a regulatory body. Spacing is based on what is deemed to be the amount of acreage that can be efficiently and economically drained by a well.

spud - The commencement of drilling operations

steam injection an improved recovery technique in which steam is injected into a reservoir to reduce the viscosity of the crude oil

steam-assisted gravity drainage (SAGD) – a recovery technique for extraction of heavy oil or bitumen that involves drilling a pair of horizontal wells one above the other, one well is used for steam injection and the other for production

stimulating the formation – a technique for improving production from a reservoir; stimulation may involve acidizing, fracturing or simply cleaning out sand.

straddle extraction plant – a gas processing plant located on or near a gas transmission line that removes natural gas liquids from the gas and returns it to the line

sulphur – a yellow mineral extracted from petroleum for making fertilizers, pharmaceuticals and other products.

sulphur dioxide (S02) – a poisonous gas formed by burning hydrogen sulphide.

surface casing – the first string of casing put into a well; it is cemented into place and serves to shut out shallow water formations and as a foundation for well control.

surface rights - the rights to work on the surface of the land.

sustainable development – development that meets the needs of the present without compromising the ability of future generations to meet their own needs (as defined by United Nations World Commission on Environment and Development).

sweeten – remove hydrogen sulphide and carbon dioxide from sour gas to make it marketable

synthetic crude oil – a mixture of hydrocarbons, similar to crude oil, derived by upgrading bitumen from oil sands


tank battery - Tank batteries are part of the production equipment installed after a well is completed. They store the salt water that is returned from a producing well.

tertiary recovery – the third major phase of crude oil recovery which involves using more sophisticated techniques, such as steam flooding or injection of chemicals, to increase recovery

top drives hydraulic or electric motors that are suspended in the derrick above the rig floor to rotate the drill string and bit.

traps – a mass of porous, permeable rock - sealed on top and both sides by non-porous, impermeable rock that halts the migration of oil and gas, causing them to accumulate.

tripping – the process of removing the drill string from the hole to change the bit and running the drill string and new bit back into the hole

trunk lines – large-diameter pipelines that transport crude oil, natural gas liquids and refined petroleum products to refineries and petrochemical plants; some trunk lines also transport refined products to consuming areas


underbalanced drilling using mud lightened by the addition of nitrogen or other gas to minimize damage to the producing reservoir by drilling fluids.

unitization – process whereby owners of adjoining properties pool reserves into a single unit operated by one of the owners , production is divided among the owners according to the unitization agreement.

upgrading – the process of converting heavy oil or bitumen into synthetic crude oil.

upstream – the exploration and production sector of the petroleum industry.


Vibroseis the process of producing seismic shock waves with “thumpers” or vibrator vehicles


wellbore - a hole drilled or bored into the earth, usually cased with metal pipe, for the production of gas or oil.

wellhead - The control equipment fitted to the top of the well, consisting of outlets, valves, blowout-prevention equipment, etc.

well-logging instruments – instruments lowered into a well to provide specific information on the condition of the well

Western Canada Sedimentary Basin – Canada’s largest region of sedimentary rocks ‘ the largest source of current oil and gas production

wireline logging tools special tools or equipment, such as logging tools, packers or measuring devices, designed to be lowered into the well on a wireline (small-diameter steel cable)

working interest - The right granted to the lessee of a property to explore for and to produce and own oil, gas or other minerals. The working interest owners bear the exploration, development and operating costs.


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