Oil and Gas Terminology

Oil and Gas Glossary



(1) Cleaning up and abandoning an inoperative well site in compliance with the applicable regulations and to the satisfaction of the concerned governmental body. (2) To cease production from the said well or field. (3) Proper plugging of the well and salvaging the equipment and material.


(1) The process aimed at reducing pollution levels or intensity. (2) Using some abatement method to reduce pollution.

American Petroleum Institute (API)  

The primary trade association that represents the energy industry in the USA (oil and natural gas).


The space between any 2 concentric objects of the borehole like (1) casing and wall (2) Casing and tubing (3) Two casing strings.

Appraisal Well    

A well drilled during the appraisal drilling program conducted to assess the rate of production for a specific field and its reserves.


A standard unit of measurement for the volume of petroleum and related products (1 ton= 7.3 barrels).


One barrel volume of oil (1 barrel = 159 liters (approx.); 6.29 barrels = 1 cubic meter).


0.83 million tons of oil is equivalent to 1 Billion cubic feet


Volume measured in billion cubic meters (1 cubic meter is equivalent to 35.31 cubic feet).


An acreage sub-division is a part of a quadrant, which is approximately equal to 10 x 20 kms.


Condensate is produced along with gas at the same time during the start of production.


Oil and gas blow-out occurs when the well pressure is more than the controlling capacity of the wellhead valves.

Blow-out preventers (BOPs)

High-pressure wellhead valves with increased capacity to control and shut off the excessive flow of hydrocarbons.


The hole of the borewell drilled by the bit.


Head of a casing.


Comparing the measurement values of a particular equipment undergoing testing, with known accuracy standards.


Cemented pipe fixed in the well used to seal off unwanted fluids from forming and to prevent caving in of the hole.

Casing string

The lining of the drilled well which is formed from screwing the sections of steel tube together.

Chart recorders

Devices used to record electrical and mechanical inputs and display on a piece of paper.

Central estimate 

Estimates made by exploring various drilling scenarios combined with experience in recent past.Christmas tree

Fittings and valves assembled on top of the casing used to control the rate of oil production.

Commercial field  

Oil or gas field worthy and capable enough to produce the desired net income.


Installing the wellhead equipment on a permanent basis, in order to produce oil and gas.


Higher hydrocarbons and pentanes that turn from gaseous state to liquid form, with changes in temperature or pressure, under the reservoir conditions.


The process of using a “core barrel”, a specialized tool for collecting rock samples from the field or well.

Crane Barge

A large barge(“derrick barge”) used to lift heavy equipment to offshore platforms.

Crude Oil  

Crude form of liquid petroleum extracted from the ground as opposed to manufactured refined oils.

Cubic foot 

A standard unit of measurement for gas; 1 cubic foot is equivalent to 0.0283 cubic meters.


Rock chips cut by drilling, which reach the surface. Geologists use these to gather data.


The towering structure that contains all the drilling controls.

Development phase

The process of drilling production wells.


The process of boring a hole (2)Equipment that is used for boring holes.


The process of drilling to production testing, capping to plugging back, sidetracking or reconditioning a well. Converting a well into a source or producing well using stratigraphic and environmental tests.

Drilling rig 

Temporary drilling unit fixed to the jack-up unit, including the derrick.

Dry Gas

Natural gas, especially methane and fewer amounts of higher hydrocarbons.

Dry hole

A non-productive well.

Enhanced oil recovery

The oil recovery process, excluding the usage of natural pressure in the reservoir.

Exploration drilling

Drilling process that determines the presence of hydrocarbons in a particular field.

Exploration phase 

Operational phase to uncover oil or gas using geophysical, geological surveys and exploratory drilling.

Exploration well  

A “wildcat well” drilled in an unproven area.

Farm in

Another company taking over the production and financial commitment of the drilling process and the well.


An area where the reservoir lies.


Extracting objects and material like tools or broken drill strings from the borehole.

Force Gauge

An instrument that measures force using pull or push test.

Formation pressure

The pressure built in the well at its bottom, when its wellhead is shut.

Formation water      

Saltwater formed with gas and oil.


In order to increase the production rate of a reservoir, the formation is broken down using the fluid pumped at very high pressures.


Gas Condensate.

Gas field 

A field containing only natural gas, and not oil.

Gas injection 

The process in which separated associated gas is injected into a reservoir to maintain its pressure.

Gas/oil ratio

The ratio of the volume of gas(at atmospheric pressure) produced to the oil produced.

Geographic Information Systems(GIS)  

Computer systems used to assemble, store and manipulate geographic information.

Hydro Testing

Tests used to detect strength and leaks of pressure vessels like boilers and pipelines.


A compound of hydrogen and carbon elements in gaseous, solid or liquid state- term used to reference oil, gas or condensate.

Injection well   

A well that pumps gas or water into a reservoir.


The lower section of offshore platforms.


A well in which the formation pressure is more than the pressure of the mud column.

Lay Barge 

A barge with special equipment for laying submarine pipelines.

Liquefied natural gas (LNG)

Natural gas, mainly methane, or oil in liquefied form, which is easy to transport.

Liquefied petroleum gas (LPG)

Light hydrocarbons converted to a liquid state by changing the pressure- for storage, transport or handling purposes. Commercial liquefied gas contains propane or butane, or both.


Million Barrels Oil Equivalent.

Mechanical Integrity Test

Setting a packer bridge plug, which is retrievable over the perforations of a wellbore and then applying pressure on the annulus.

Metric ton

1 metric ton= 7.5 barrels or 1000 kilos, equivalent to 2204.61 lbs.


Millions of cubic feet in a day (of gas).


Drillship aperture facilitating the drilling or diving operations.


Base substance mixed with additives that lubricate the drill bit and counteract natural pressure formation.

Natural gas

Naturally found gas along with crude petroleum.


Liquid hydrocarbons found along with natural gas.


Natural Gas Policy Act of 1978.


Oil and Gas.


Various liquid hydrocarbons with different molecular weights and their mixture


The geographic area over the oil reservoir.

Oil in place

The total estimated amount of oil in the reservoir which is a higher figure than estimated recoverable reserves.


The company with the legal authority over the entire process of drilling wells- acts on behalf of the consortium to which it belongs.


Rock in which there are exploitable quantities of oil and gas.


The property of the formation which allows the fluid to flow through its pore spaces and enter the wellbore.


Hydrocarbons, natural gas, crude oil, natural gas liquids and their products.


A permanent offshore structure fixed to the seabed.


Comparative percentage ratio of the void in a porous rock in its solid formation.

Possible reserves

Those reserves whose probability is less than 50%, but still have the possibility of being producible.

Pressure Measurement

Is pressure applied by gas or fluid on unit surface area.

Pressure Relief Valve

The value used to control the pressure build up that can damage the equipment.

Primary recovery

Recovering the oil or gas from the reservoir by using nothing more than the built natural pressure to force it out.

Probable reserves

Those reserves with more than 50% probability of being producible.

Proven field

Oil and/or gas fields whose reserves and physical extent are already determined.

Proven reserves

Reserves which are virtually proved to have more than 90% probability of being producible.

Recoverable reserves

That proportion of total reserves in a reservoir of oil and/gas that can be extracted using current techniques.


To abandon a well then enter the same again.


The underground formation with porous rock, where there is an accumulation of oil and gas. Caprock prevents them from escaping.

Riser (drilling)

A drilling pipe fixed between seabed BOP and floating rig.

Riser (production)

Pipework section joining the seabed wellhead and the Christmas tree.


Drill crew members who screw the drill pipe sections together, working on the aderrick floor.


Drill crew members assisting in general operations and load and unload the equipment around the rig.

Royalty payment

Owner of the mineral rights receives cash, called royalty.

Secondary recovery

The process of obtaining oil or gas by injecting gas or water, and artificially enhancing the reservoir pressure in the reservoir rock.

Shut-In Well

A producible well which is not currently producing owing to lack of equipment or other reasons.


A hiatus where production ceases, but necessary maintenance work is done.


Shut In /Temporarily Abandoned


Drilling a wellbore segment from the existing wellbore intersection to the bottom hole or target of this new wellbore.


The drilling process involving the first part in a new well.

Surface Location

The location of the measurement point or a well.

Suspended well

Temporarily capped off well.


Trillion Cubic Feet (of gas).

Temporarily Abandoned

Isolating completed intervals of a wellbore using a cement retainer, a cast iron bridge plug or other methods.


Second highest in the hierarchy of the drilling crew, next to the drilling superintendent, who ensures the availability of the necessary equipment on daily basis.


The superstructure of the platform.

Torque Tester

Device to test quality control of the tools in use.

Torque Wrench

A tool used to fasten nuts and bolts, in order to apply specific torque.

Underground Injection Control (UIC )

A program to regulate Injection Wells that adversely affect the quality of an underground drinking water source. The applicant seeking the permit has to demonstrate that it complies with the Safe Drinking Water Act (SDWA) Act.

Well log

A record of the geological formation undergoing the operation- all the details of drilling, including technical aspect are recorder in the log.

Wildcat well

An “exploration well” being drilled in an undetermined reserve or unproven area.


Remedial work was done to the equipment used within the well in order to increase the flow rate.