The complexities of the oil and gas industry can make keeping up with all the terms and definitions related to drilling difficult. To simplify things, we’ve compiled a glossary of the most important terms related to drilling and to the oil and gas industry.
Oilfield Glossary of Terms
To pause or stop drilling operations or production from a well. Reasons for abandoning are if a well is a dry hole or if it’s not producing enough to be kept active.
To increase the flow of oil or gas in drilling, hydrochloric acid can be pumped into the well. The acid works to break down limestone, reducing the restrictions the oil or gas was previously facing to increase flow.
AESC Association of Energy Service Companies:
This association provides training materials and represents the interests of energy service employees within the oil and gas industry.
API – Monogram:
The logo of the American Petroleum Institute (API) is added to equipment that meets their minimum standards. API also provides industry-related publications about recommended practices and standards.
Used to describe any method for retrieving oil from a well and bringing it to the surface after the well ceases to produce.
Natural gas that’s created with crude oil from the same resevoir.
The part of a separation vessel used to temporarily slow the flow of fluids; needed when attempting to separate oil and water.
A steel bar that supports the swivel and connects it to the hook; resembles the handle of a bucket.
Barrel of Oil Equivalent (BOE):
The amount of oil barrels produced from a site each day.
A steel bar that supports the swivel and connects it to the hook. Resembles the handle of a bucket.
An extremely viscous form of crude oil that contains sulfer and other metals; to be produced, bitumen must be heated or combined with lighter hydrocarbons.
An oil and gas limited partnership that has not comitted to a single lease or property yet.
Occurs when down-hole pressure gas is not properly balanced with the weight of the drilling mud; the uncontrolled flow of gas, oil, or other fluids.
As a noun, a bore is the inside diameter of a pipe or drilled hole. As a verb, bore means to penetrate a surface with a rotary tool.
An acronym for British Thermal Unit, BTU is a measurement to describe the amount of heat generated from burning oil or gas.
A rope, wire or braid of strong fibers.
A well that has the casing already inserted. The opposite of a cased hole is an open hole.
A steel pipe that’s placed in an oil or gas well after drilling is completed to prevent the well hole from caving in. Casing also prevents fluids from moving from one formation (like groundwater) to another and helps in well control.
Drill Rig: The machinery that’s used to drill oil and gas wells. There are two types of drill rigs: rotary and cable tools, with rotary drill rigs being more efficient.
A large wrench used for turning casing tubulurs when making up or breaking out casing.
A long, but small in diameter pipe that is used to replace jointed pipes in certain types of drilling, completion, and workover operations.
A well that produces enough to pay for it’s production costs and leave enough oil and gas to be sold for revenue.
Used to describe all activities between drilling to casing point and putting the well to production. Includes cleaning out the well bore, setting the casing and tubing, adding surface equipment, and perforating the casing.
An engine that is used to increase natural gas pressure so that it can more easily flow through the pipeline.
Oil’s form as it comes directly from the ground; it’s a mixture including naturally occurring liquid hydrocarbons.
The loss in mineral deposits as the well is produced.
Depletion (Gas) Drive:
When drilling into an oil source, free gas in the well expands and allows the oil to flow into wellbore and up to the surface; also known as a solution gas drive.
A well that’s drilled in a proven oil or gas reservoir at the depth of proven productivity.
A removable, steel, serrated piece that fits into the jaws of tongs. Die inserts grip drill pipes, drill collars and casing while the tongs are making up or breaking out pipe.
A tool used to shape, form, or finish other tools or pieces of metal.
An internal-combustion engine frequently used for powering drilling rigs. A diesel engine is a high-compression engine that draws air into its cylinders and compresses the air to very high pressures; ignition then occurs as fuel is injected into the compressed, hot air. Combustion takes place in the cylinder above the piston; the combustion then powers the piston.
Also called a dip meter or dip log, this surveying method determines the direction and angle of a formation dip in relation to the borehole to provide geological structure of the formation.
Drilling in the opposite direction of a wellbore from the vertical. Directional drilling uses rotary steerable tools to move around rocks or other obstructions to continue drilling.
The industry that includes: oil refineries, petrochemical plants, petroleum products distributors, retail outlets and natural gas distribution companies. The Downstream operates anywhere oil, plastics and natural gases are used.
The cutting or boring element used to access oil or gas in the drilling process. Not only are most bits roller-cone bits, but the drill bit also typically includes both the cutting element and the circulating element.
A heavy steel tube that’s placed between the drill pipe and the bit in the drill stem. Drill collars are used to add weight to the bit to make drilling easier.
A piece of seamless tubing used to rotate the bit and circulate the drilling fluid. The pipe joints are usually about 30 feet long and are joined together by tool joints.
The machinery that’s used to drill oil and gas wells. There are two types of drill rigs: rotary and cable tools, with rotary drill rigs being more efficient.
Transmits fluid and rotational power from the kelly bushing to the drilling collar. As the name suggests, the drill string is a column, or string, with attached tool joints.
Electronic Flow Meter:
Monitors the amount of oil and gas flowing from a wellhead; measurements are expressed in real time, actual flow, cumulative flow, and historical data.
A drilling rig – typically powered by diesel – where the original energy source is converted to electricity via generators. Electricity is then pumped through electrical conductors to electrical motors.
Cylindrical bars used to attach elevators to the hooks and support the weight of the elevator.
Hinged steel devices with manual operating handles that are attached to rotary and top drive rigs. Crew members latch elevators onto tool joints to operate them.
Enhanced Oil Recovery:
This oil recovery process that restores formation pressure and improves oil displacement can be used at any point of the productive life of an oil reservoir. There are three major types of enhanced oil recovery: chemical flooding, miscible displacement, and thermal recovery. Each recovery type alters the original properties of oil, but the specific type used is dependent on the temperature, depth, and other traits of the reservoir.
Estimated Ultimate Recovery (EUR):
An estimation of the cumulative volume of reserves that will be discovered in a specific reservoir.
A well created for the purpose of finding oil or gas in a previously unproductive area.
A well that produces oil and gas using its own reservoir pressure as opposed to pumps or other production methods.
Also known as heavy oil, this substance contains dispersed gas bubbles that were created at the wellhead of a heavy oil reservoir. The bubbles in foamy oil stay small, keeping the oil viscosity low, while still creating the energy needed to drive the oil to the producing well.
The process of a fluid (usually crude oil, diesel or water) being pumped into the reservoir to break the reservoir rock open.
A liquid, typically water, oil, or an acid, that’s used in hydraulic fracturing. Fracturing fluid assists in the hydraulic fracturing process by carrying propping agents that hold open formation cracks after hydraulic pressure dissipates.
Free Water Knockout (FWKO):
A vertical or horizontal separator used to separate gas, oil and water. The water is removed to prevent corrosion and the formation of hydrates or tight emulsions.
Used to prevent gas lock, this tubular and perforated device works by allowing the lighter gas to rise, while the fluids make their way to the pump. It works like this: fluids first enter the anchor, while gas rises and exits the anchor through the perforations at the top. The rest of the fluids enter the anchor through a mosquito bill which allows all the gas to escape before fluids enter the pump.
The energy created by expanding compressed gas within a reservoir. Also called a depletion drive, this energy moves crude oil to a wellbore.
The process of injecting gas into a reservoir to maintain the pressure created by the gas drive. This process also reduces the decline rate of the original reservoir drive. There are two main types of gas injection: non-miscible oil and miscible oil injection.
A well that primarily produces gas.
Crude oil with an API gravity of 20 degrees or less. It tends to have a high viscosity and hinders an easy flow of oil.
A drilling technique that consists of vertical drilling down to a particular depth, and then involves turning at a right angle to drill horizontally within a specified reservoir.
Operated, moved, or effected by water or liquid.
High-pressured liquid is pumped into a formation to force the formation open and create passages for oil to flow into the wellbore.
A pumping method that uses a downhole pump without sucker rods. Specifically, two reciprocating hydraulic pumps are used; the first pump powers the second, production pump. Single and double tubing strings can both be used to pump multiple wells from a main source. When a single string is used, power oil travels down the string to the pump, and a mix of power oil and fluid is returned through the casing tub annulus. When two strings are used, power oil travels down one string, while the other returns the exhaust and produced fluid.
In this electric well log, the conductivity of a formation is measured. In other surveys, the resistivity is measured. Conductivity measurements work because oil-bearing formations are less conductive than water-bearing formations.
Injects coiled tubing into a well to seal the tubing and provide a pressure tight connection.
As the name hints, an injection well is a well where fluids are injected into an underground stratum. Also called an input well, this process increases reservoir pressure and displaces oil.
A weighted float created to sink in oil and float in water; used as a testing tool.
A single section of drill pipe, casing or tubing that’s usually about 30 feet long.
Joint Operating Agreement (JOA):
A written agreement between multiple land operating partners that details how the land will be developed, who will pay for the exploration and development, and when this development will happen.
A phrase to describe an oil and gas investment project.
This steel piece turns the drill stem as the rotary table turns; typically suspended from the swivel through the rotary table and then connected to the top joint of the drill pipe.
A long hollow steel bar that’s used to connect the upper end of a drill string. Kelly bushing is a sleeve in the rotary table that allows the Kelly to freely move up and down during drilling. Kelly bushing also plays a part in the measurement of well depth, as well depth is measured from the Kelly bushing, down to the bottom of the well.
Occurs when water, gas, oil, or other fluid enters the wellbore during drilling when the pressure created by the column of drilling fluid is lower in comparison to the pressure created by fluids in the drilled formation. When not addressed, kicks may cause blowouts.
Any combination of fluids (including oil, gas, and water) that enters the borehole from a permeable formation.
The person who manages land leasing and land damages for oil and gas companies.
The agreement formed by the owner of the property and the interested exploration and development party. The property owner gives the lessee exclusive rights to search for and extract any minerals found on the property.
The person who acquires the rights to drill for oil or gas on a piece of land.
The landowner who grants access for drilling for oil or gas on their land, known as a mineral lease.
The person who acquires the rights to drill for oil or gas on a piece of land.
The most common definition of a liner is a pipe used below existing casing to case an open hole. A liner extends from the setting depth up into another string of casing above the lower end of the oil string. Other types of liners include: a short type of perforated pipe that’s placed opposite of a producing formation to prevent loose sand from entering the well; liners in jet perforating guns are conically shaped and are used to increase the efficiency of the charge by improving the jet penetrability; cylinder liners are replaceable tubes created to fit inside the cylinder of an engine or a pump.
Low Pressure Control Valve:
A diaphragm used to control the flow of liquid and gas; often found in oil and water dump valves. Used in systems with working pressures up to 300 psig.
Also known as the master gate, the master valve is located on the Christmas tree and used to control gas and oil flow.
The acronym that represents one thousand barrels of oil equivalent.
Mechanical Oil Valve:
Also known as a Mechanical Liquid Valve or a Dump Valve, it is designed to work together with a trunnion assembly to remove liquids from the vessel. It’s controlled by a mechanical level.
The sector within the industry between oil production and the consumers that processes, stores and markets crude oil and natural gas.
The movement of oil and gas within layers of rock deep within the earth.
The owner of the gas, oil, or other minerals when they’re naturally occuring in a reservoir. Frequently, mineral owners will contract a oil or gas lease with a third-party to extract the minerals.
A unit of measurement to describe a million barrels of curde oil, bitumen, natural gas liquids, or condensate.
A mixture of hydrocarbons and non-hydrocarbons (like Hydrogen Sulfide or Nitrogen) in the same gaseous space or in a mixture of crude oil in underground preserves
Net Oil Production:
The amount of oil produced minus the injected oil (also known as the power oil).
The extracted natural gas from a reservoir that doesn’t contain notable amounts of crude oil.
A type of drilling mud where the oil is in the continuous phase. Oil-base mud is frequently used where it is difficult to drill with waterbase mud.
A compartment of the separator that gathers oil skimming over the oil weir.
The surface area, reservoir, wells and production equipment overlying oil reservoirs.
The pipe that directs oil out of the treater.
Similar to a dam, this vessel compartment allows oil to skim over into the oil chamber.
The party or person responsible for the drilling and operation of a well, and the maintenance of the leased land. All of the operator’s responsibilities will be detailed in the JOA.
Over Balanced Drilling:
Used to describe instances where the pressure used to drill (from the drilling fluids) is more than the pressure of the oil or gas within the reservoir.
An oil and gas lease that’s paid to the Lessor through the first term at the lease signing.
A hollow steel tube that transports fluids. Pipes used in oil fields are: casing, drill pipes, tubing, and line pipes.
The part of the sucker rod pump that pulls well fluids into the pump.
This type of crude oil is used to energize the bottom pump in hydraulic pumping through surface pressurization.
After deducting the expenses from the oil production, the amount of production that’s left is known as profit oil. This oil will be shared among participating parties and the host government based on the production sharing contract.
Processing plant where crude oil is turned into a variety of more useful oils like gasoline and diesel.
The amount of oil and gas in a reservoir that can be extracted. Measured in terms of barrels of oil or million cubic feet (MCF)
Simply put, a reservoir is the rock body in which oil or gas is stored. Common reservoir rocks are limestones, dolomites, or sandstones – all rocks that are porous, permeable, or naturally fractured. A reservoir can be filled with oil, volatile oil, dry gas, and gas condensate.
When fluids are flowing through rock by way of primary recovery, secondary recovery, and invasion, residual oil does not move.
The machine used to drive rotational power to the drill stem while still allowing vertical movement of the pipe for rotary drilling. Most moden rotary machines have a rotary or master brushing used to turn the kelly bushing, which then allows vertical movement of the kelly while the stem is turning.
A percentage of the profits made from the development of mineral resources. Royalties are paid to the property owners.
Funds given to the lessor from the production of oil and gas excluding production costs, taxes, and transportation fees.
Salt Water Disposal Well:
Oilfield salt water is drained into these wells.
Once a reservoir has been fully extracted using the primary production method, the well or field moves into secondary recovery. Secondary recovery methods frequently include gas injection or water flooding – the goal being to repressurize the reservoir for additional oil recovery.
Closing the valves on a well to stop production. Can also refer to a well on which the valves were closed to stop production.
Spring Loaded Back Pressure Regulator:
Controls the gas pressure and water level in the vessel of a free water knockout.
Steam Oil Ratio:
Also known as SOR, steam-oil ratio is used to rate the efficiency of steam injection oil production. The ratio measures the volume of steam needed to create one unit volume of oil and the lower the ratio, the more efficiently the steam is being used.
A type of improved recovery method used to restore formation pressure, improve oil displacement, or improve reservoir fluid flow. Can also be used to extract additional oil after the secondary recovery.
A floatless level control valve, typically installed with the water leg and oil leg of a heater treater.
A pipe with a small diameter or a tube threaded at both ends. Tubing is lowered into a completed well so that oil and gas can be produced through the string of tubing.
A type of fixed price drilling contract where a drilling contractor is required to drill to a specific depth and provide ample equipment so the operator only needs to turn a valve to see oil or gas flow.
A horizontal, vertical, or spherical vessel that separates well fluids into gas and total liquid. The oil leaves the vessel through the bottom, while gas leaves through the top.
Ultra Heavy Oil:
The US Department of Energy classifies a hydrocarbon fluid as an ultra heavy oil when it has a gravity of 10 degrees API or lower.
A type of sand formation where the grains of sand don’t stick to each other. When an unconsolidated sandstone produces oil, it frequently is mixed with sand unless properly controlled.
When multiple oil companies are involved in field production, the unit operator is the company in charge of development and production.
The sector within the oil and gas industry that finds and produces crude oil and natural gas; often called the exploration sector.
Used as a safety device to control flow within a line by opening or shutting a line completely.
In geophysics, velocity is described as medium-distance divided by traveltime. Velocity can be measured vertically, laterally, and azimuthally and measured with laboratory measurements, acoustic logs, vertical seismic profiles, and velocity analysis of seismic data.
Used to describe a fluid’s resistance to flow. For example, a highly viscous fluid won’t flow as easily as one with a low viscosity.
A heavy crude oil with a viscosity above 10 cp, a gravity below 22.3 degrees API, and low hydrogen-to-carbon ratios. Viscous oil also boasts higher acid numbers as well as high nitrogen and heavy-metal content.
The production of oil due to the expansion of underlying water and rock, which then forces oil into the wellbore. Both bottom water drive and edgewater drive are commonly used. Bottom water involves oil that’s totally in contact with water, whereas with edgewater, only a small portion of the oil touches water.
Water in Oil Emulsion:
A type of drilling fluid that consists of an external phase of oil with water or brine droplets.
Also knowns as WOR, water oil ratio is the ratio of produced water to produced oil.