Annulus Access Valve


To cease efforts to produce oil or gas from a well, and to plug the wells of a depleted formation and salvage all material and equipment.
Final plugging of wells, and/or permanent dismantling, etc. of a production platform or other installation.


Acrylonitrile 50 butadiene styrene (a hard, tough thermoplastic).


The ability of gas, liquid or solid to attract and retain another substance without chemical combination. A quantity of such a substance that has absorbed as much of another as is physically possible is said to be saturated with it. Some refinery processes use this ability, for instance to separate different hydrocarbons.


A pressure vessel charged with nitrogen gas and used to store hydraulic fluid under pressure for the operation of hydraulic valve actuators.


Also known as a takeover is the buying of one company (the ‘target’) by another. An acquisition may be friendly or hostile. In the former case, the companies cooperate in negotiations; in the latter case, the takeover target is unwilling to be bought or the target's board has no prior knowledge of the offer. Acquisition usually refers to a purchase of a smaller firm by a larger one. Sometimes, however, a smaller firm will acquire management control of a larger or longer established company and keep its name for the combined entity. This is known as a reverse takeover.


Unit used to measure the rock volume of an oil or gas reservoir structure.

Activist investors

An individual or group that purchases large numbers of a public company's shares and/or tries to obtain seats on the company's board with the goal of effecting a major change in the company. A company can become a target for activist investors if it is mismanaged, has excessive costs, could be run more profitably as a private company or has another problem that the activist investor believes it can fix to make the company more valuable. Activist investors aim to make money by buying shares of companies and then pushing them to change their strategy. This can include raising their dividend, launching a share buyback, spinning off a division, or an outright sale of company.


A (hydraulic or electrical) device for the remote and/or automatic operation of a valve or choke.


Automotive Diesel Oil. Diesel used as vehicle fuel.


Atmospheric Diving System


The attraction exhibited by the surface of a solid for a liquid or gas, when they are in contact, without absorbing the liquid or gas.


Advanced Drilling Techniques


Atmospheric Gas Oil. Diesel produced by the atmospheric (primary) distillation of crude oil.

Air Emissions

The release of various gases into the atmosphere.

Air Quality Standards

The prescribed level of pollutants allowed in outside or indoor air as established by legislation.


Auto Ignition Temperature

Aliphatic Hydrocarbons

A group of hydrocarbon substances, including the alkanes and most of the other fractions found naturally in crude oil.


A refining process used to produce improved gasoline components with, for instance, lower pollutant effects.


A deviation from the norm. In geology, the term indicates an abnormality such as a fault or a dome in a sedimentary bed.


It is an area of the subsurface where the strata have been pushed into forming a domed shape.

Anticlinical Trap

A hydrocarbon trap in which petroleum accumulates in the top of an anticline.

API Gravity

The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light petroleum liquid is compared to water. If its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks. API gravity is thus a measure of the relative density of a petroleum liquid and the density of water, but it is used to compare the relative densities of petroleum liquids.

Appraisal Well

A well drilled to further confirm and evaluate the presence of hydrocarbons in a reservoir that has been found by a wildcat well.


A water-bearing rock strata. In a water-drive field, the aquifer is the water zone of the reservoir underlying the oil zone.

Aromatic Hydrocarbons

The group of hydrocarbon products which include benzene, toluene, etc. and provide feedstocks for many of the main petrochemical processes asa well as high octane rating gasoline blends. So-called from their "sweet" smell.

Artificial Lift

Any method used to raise oil to the surface through a well after reservoir pressure has declined to the point at which the well no longer produces by means of natural energy. Sucker rod pumps, gas lift, hydraulic pumps, and submersible electric pumps are the most common forms of artificial lift.


A solid petroleum residue, similar to bitumen, tar and pitch.

Associated Gas

Natural gas which is in contact with crude oil in the reservoir or which is dissolved in the oil.


Aviation Gasoline, used as fuel for propeller airplanes.