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The Kallanish Glossary aims to be a useful resource for complex industry specific terminology. We are constantly adding to our glossary, so if you have a suggestion or amendment please do get in touch.

To cease work on a well which is no longer in production and to plug off the well with cement plugs while salvaging material and equipment. 

Absorption Oil

A hydrocarbon liquid used to absorb and recover components from natural gas before being processed.

Appraisal Well

A well drilled as part of an appraisal drilling program which is carried out to determine the physical extent, reserves and likely production rate of a field.

Associated Gas

Associated gas is a form of natural gas which is found with deposits of petroleum, either dissolved in the oil or it may form a cap of free gas above the oil. 


A unit of volume measurement used for petroleum and its products.


To vent gas from a well or production system. Wells that have been shut in for a period often develop a gas cap caused by gas percolating through the fluid column in the wellbore. It is often desirable to remove or vent the free gas before starting well intervention work.

Blow Out

An uncontrolled flow of reservoir fluids into the wellbore, and sometimes catastrophically to the surface. A blowout may consist of salt water, oil, gas or a mixture of these. Blowouts occur in all types of exploration and production operations, not just during drilling operations.

Blow Out Preventer

A large valve at the top of a well that may be closed if the drilling crew loses control of formation fluids. These high pressure valves are designed to shut off the uncontrolled flow of hydrocarbons.


A borehole is a narrow shaft, bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water or other liquid (such as petroleum) or gases (such as natural gas). As well as pumping petroleum from an underground well through a borehole, liquid or gas can be pumped into it, for that process, or for underground storage of unwanted substances. 


Casing is the structural retainer for the walls of oil and gas wells. The process is used to prevent contamination of both the surrounding water table and the well itself. Casing lasts the life of a well and is not usually removed when a well is closed.

Casing Pipe

Casing is the term given to pipe that is cemented into the well to seal off formation fluids or to keep the hole from caving in. Casing pipe is usually manufactured from plain carbon steel that is heat-treated to varying strengths, but may be specially fabricated of stainless steel, aluminum, titanium, fiberglass and other materials.

Casing String

An assembled length of steel pipe configured to suit a specific wellbore. The sections of pipe are connected and lowered into a wellbore, then cemented in place.


The installation of permanent wellhead equipment for the production of oil and gas.


An engine used to increase the pressure of natural gas so that it will flow more easily through a pipeline. A compressor normally uses positive displacement to compress the gas to higher pressures so that the gas can flow into pipelines and other facilities.


Hydrocarbons which are in the gaseous state under reservoir conditions and which become liquid when temperature or pressure is reduced.Its presence as a liquid phase depends on temperature and pressure conditions in the reservoir allowing condensation of liquid from vapour. Gas produced in association with condensate is called wet gas.

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