To cease work on a well which is non-productive, to plug off the well with cement plugs and salvage all recoverable equipment. Also used in the context of field abandonment.

Associated gas
Natural gas produced with crude oil from the same reservoir.

Annex B
Operator’s development plan for an offshore installation. It requires government approval before it can be implemented.

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

Associated Gas
Natural gas associated with oil accumulations, which may be dissolved in the oil at reservoir conditions or may form a cap of free gas above the oil.

A unit of volume measurement used for petroleum and its products (7.3 barrels = 1 ton: 6.29 barrels = 1 cubic metre).

One barrel of oil; 1 barrel = 35 Imperial gallons (approx.), or 159 litres (approx.); 7.5 barrels = 1 tonne (approx.); 6.29 barrels = 1 cubic metre.

Billion cubic feet; 1 bcf = 0.83 million tonnes of oil equivalent.

Billion cubic metres (1 cubic metre = 35.31 cubic feet).

A North Sea acreage sub-division measuring approximately 10 x 20 kms, forming part of a quadrant. e.g. Block 9/13 is the 13th block in Quadrant 9.

Condensate and gas is produced simultaneously from the outset of production.

Blow-out preventers
(BOPs) are high pressure wellhead valves, designed to shut off the uncontrolled flow of hydrocarbons.

When well pressure exceeds the ability of the wellhead valves to control it. Oil and gas “blow wild” at the surface.

The hole as drilled by the drill bit.

British thermal unit (BTU)
A measure of the heating value of a fuel.

Capital expenditure.

Metal pipe inserted into a wellbore and cemented in place to protect both subsurface formations (such as groundwater) and the wellbore. A surface casing is set first to protect groundwater. The production casing is the last one set. The production tubing (through which hydrocarbons flow to the surface) will be suspended inside the production casing.

Casing string
The steel tubing that lines a well after it has been drilled. It is formed from sections of steel tube screwed together.

Common Data Access is a not-for-profit subsidiary of Oil & Gas UK, set up in 1994 to provide data management services to its members and to the UK oil industry in general.

Christmas tree
The assembly of fittings and valves on the top of the casing which control the production rate of oil.

Central North Sea.

Commercial field
An oil and/or gas field judged to be capable of producing enough net income to make it worth developing.

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

Hydrocarbons which are in the gaseous state under reservoir conditions and which become liquid when temperature or pressure is reduced. A mixture of pentanes and higher hydrocarbons.

Taking rock samples from a well by means of a special tool — a “core barrel”.

Crane barge
A large barge, capable of lifting heavy equipment onto offshore platforms. Also known as a “derrick barge”.

Creaming Theory
A statistical technique which recognises that in any exploration province after an initial period in which the largest fields are found, success rates and average field sizes decline as more exploration wells are drilled and knowledge of the area matures.

Rock chippings cut from the formation by the drill bit, and brought to the surface with the mud. Used by geologists to obtain formation data.

An engine used to increase the pressure of natural gas so that it will flow more easily through a pipeline.

Managed by CDA, a unique index of the source of released and proprietary well, seismic and other data.

The tower-like structure that houses most of the drilling controls.

Development well
A well drilled within the proved area of an oil or gas reservoir to the depth of a stratigraphic horizon known to be productive; a well drilled in a proven field for the purpose of completing the desired spacing pattern of production.

A term used to describe tools, equipment, and instruments used in the wellbore, or conditions or techniques applying to the wellbore.

When referring to the oil and gas industry, this term indicates the refining and marketing sectors of the industry. More generically, the term can be used to refer to any step further along in the process.

Drill cuttings
The small pieces of rock created as a drill bit moves through underground formations while drilling.

Drilling rig
A drilling unit that is not permanently fixed to the seabed, e.g. a drillship, a semi-submersible or a jack-up unit. Also means the derrick and its associated machinery.

Dry gas
Natural gas composed mainly of methane with only minor amounts of ethane, propane and butane and little or no heavier hydrocarbons in the gasoline range.

Dry hole
Any exploratory or development well that does not find commercial quantities of hydrocarbons.

Abbreviation for exploration and appraisal.

Abbreviation for exploration and production. The ‘upstream’ sector of the oil and gas industry.

Enhanced oil recovery (EOR)
A process whereby oil is recovered other than by the natural pressure in a reservoir. Refers to a variety of processes to increase the amount of oil removed from a reservoir, typically by injecting a liquid (e.g., water, surfactant) or gas (e.g., nitrogen, carbon dioxide).

Exploration well
Drilling carried out to determine whether hydrocarbons are present in a particular area or structure. Also known as a ‘wildcat well’.

Farm in
When a company acquires an interest in a block by taking over all or part of the financial commitment for drilling an exploration well.

A geographical area under which an oil or gas reservoir lies.

Retrieving objects from the borehole, such as a broken drillstring, or tools.

Fisheries Legacy Trust Company; formed in 2007 by Oil & Gas UK, Scottish Fishermen’s Federation (SFF) and National Federation of Fishermen’s Organisations (NFFO) to enhance the safety of fishermen by ensuring the provision in perpetuity of information relating to oil and gas seabed structures and equipment in UK waters.

Formation damage
The reduction in permeability in reservoir rock due to the infiltration of drilling or treating fluids into the area adjacent to the wellbore.

Formation pressure
The pressure at the bottom of a well when it is shut in at the wellhead.

Formation water
Salt water underlying gas and oil in the formation.

A method of breaking down a formation by pumping fluid at very high pressure. The objective is to increase production rates from a reservoir.

Gas field
A field containing natural gas but no oil.

Gas injection
The process whereby separated associated gas is pumped back into a reservoir for conservation purposes or to maintain the reservoir pressure.

Gas-to-Liquids (GTL)
The conversion of natural gas to a liquid form so that it can be transported easily. Typically, the liquid is converted back to natural gas prior to consumption.

A compound containing only the elements hydrogen and carbon. May exist as a solid, a liquid or a gas. The term is mainly used in a catch-all sense for oil, gas and condensate.

The Industry Mutual Hold Harmless indemnity regime is a scheme run by LOGIC to address the contractual gap which traditionally exists between contractors working on the UKCS.

Integrated company
Indicates a firm that operates in both the upstream and downstream sectors (from exploration through refining and marketing).

Injection well
A well used for pumping water or gas into the reservoir

Industry Technology Facilitator; an internationally recognized champion for technology innovation within the oil and gas industry acting as a conduit between technology innovators and the industry.

Irish Sea.

The lower section, or ‘legs’, of an offshore platform.

A legal document conveying the right to drill for oil and gas, or the tract of land on which a lease has been obtained where the producing wells and production equipment are located.

Lifting costs
The cost of producing oil from a well or lease.

Liquefied natural gas (LNG)
Oilfield or naturally occurring gas, chiefly methane, liquefied for transportation.

Liquefied petroleum gas (LPG)
Light hydrocarbon material, gaseous at atmospheric temperature and pressure, held in the liquid state by pressure to facilitate storage, transport and handling. Commercial liquefied gas consists essentially of either propane or butane, or mixtures thereof.

A not-for-profit, wholly owned subsidiary of Oil & Gas UK, set up in 1999 by PILOT to stimulate supply chain collaboration and improve the competitiveness of the UKCS.

Master Deed
Run by LOGIC, the Master Deed greatly expedites the transfer of UKCS offshore licence interests and other agreements relating to associated assets and infrastructure. It also introduces a standard pre-emption regime to give confidence to incoming companies.

Million Barrels Oil Equivalent.

Metric tonne
Equivalent to 1000 kilos, 2204.61 lbs; 7.5 barrels.

Millions of cubic feet per day (of gas).

A mixture of base substance and additives used to lubricate the drill bit and to counteract the natural pressure of the formation.

A term sometimes used to refer to those industry activities that fall between exploration and production (upstream) and refining and marketing (downstream). The term is most often applied to pipeline transportation of crude oil and natural gas.

Natural Gas
Gas, occurring naturally, and often found in association with crude petroleum.

Natural gas liquids (NGLs)
The portions of gas from a reservoir that are liquified at the surface in separators, field facilities, or gas processing plants. NGL from gas processing plants is also called liquified petroleum gas (LPG).


Northern North Sea.

Non-associated gas
Natural gas produced from a reservoir that does not contain significant quantities of crude oil.

A mixture of liquid hydrocarbons of different molecular weights.

Oil field
A geographic area under which an oil reservoir lies.

Oil in place
An estimated measure of the total amount of oil contained in a reservoir, and, as such, a higher figure than the estimated recoverable reserves of oil.

The company that has legal authority to drill wells and undertake production of hydrocarbons. The operator is often part of a consortium and acts on behalf of this consortium.

Operating expenditure.

OPITO – The Oil & Gas Academy
As the skills organisation for oil and gas, OPITO supports the industry to build a sustainable, competent and safe workforce

Rock in which oil and gas are found in exploitable quantities.

The property of a formation which quantifies the flow of a fluid through the pore spaces and into the wellbore.

A generic name for hydrocarbons, including crude oil, natural gas liquids, natural gas and their products.

P&A (plugged and abandoned)
A depleted well or dry hole that has been (typically) filled with cement and marked, with all surface equipment removed.

A measure of the ability of a rock to transmit fluid through pore spaces.

A joint programme involving the Government and the UK oil and gas industry: operators, contractors, suppliers, trade unions and SMEs, aiming to secure the long-term future of the industry in the UK.

An offshore structure that is permanently fixed to the seabed.

A ratio between the volume of the pore space in reservoir rock and the total bulk volume of the rock. The pore space determines the amount of space available for storage of fluids.

Possible reserves
Those reserves which at present cannot be regarded as ‘probable’ but are estimated to have a significant but less than 50% chance of being technically and economically producible.

Primary recovery
Recovery of oil or gas from a reservoir purely by using the natural pressure in the reservoir to force the oil or gas out.

Probable reserves
Those reserves which are not yet proven but which are estimated to have a better than 50% chance of being technically and economically producible.

Produced water
The water extracted from the subsurface with oil and gas. It may include water from the reservoir, water that has been injected into the formation, and any chemicals added during the production/treatment process. Produced water is also called ‘brine’ (and may contain high mineral or salt content) or ‘formation water’. Some produced water is quite fresh and may be used for livestock watering or irrigation (where allowed by law).

Proven field
An oil and/or gas field whose physical extent and estimated reserves have been determined.

Proven reserves
Those reserves which on the available evidence are virtually certain to be technically and economically producible (i.e. having a better than 90% chance of being produced).

Recoverable reserves
That proportion of the oil and/gas in a reservoir that can be removed using currently available techniques.

Recovery factor
The ratio of recoverable oil and/or gas reserves to the estimated oil and/or gas in place in the reservoir.

The underground formation where oil and gas has accumulated. It consists of a porous rock to hold the oil or gas, and a cap rock that prevents its escape.

Riser (drilling)
A pipe between a seabed BOP and a floating drilling rig.

Riser (production)
The section of pipework that joins a seabed wellhead to the Christmas tree.

Drill crew members who work on the derrick floor, screwing together the sections of drillpipe when running or pulling a drillstring.

Drill crew members who handle the loading and unloading of equipment and assist in general operations around the rig.

A percentage interest in the value of production from a lease that is retained and paid to the mineral rights owner.

Secondary recovery
Recovery of oil or gas from a reservoir by artificially maintaining or enhancing the reservoir pressure by injecting gas, water or other substances into the reservoir rock.

The process of separating liquid and gas hydrocarbons and water. This is typically accomplished in a pressure vessel at the surface, but newer technologies allow separation to occur in the wellbore under certain conditions.

A production hiatus during which the platform ceases to produce while essential maintenance work is undertaken.

Southern North Sea.

The operation of drilling the first part of a new well.

Standard contracts
Known formerly as CRINE contracts, standard contracts have been developed by the Standard Contracts Committee and are issued by LOGIC for use within the industry between clients and their contractors, simplifying procedures and saving costs.

Standard agreements
State-of-the-art solutions for oil and gas industry agreements and recommended for use by all UKCS licensees. They are user-friendly and easy to implement. In helping simplify operational and transactional procedures, they focus resources and save costs.

Step Change in Safety
The UK based partnership with the remit to make the UK the safest oil and gas exploration and production province in the world. It was founded in 1997 by the oil and gas industry trade associations with the aim of reducing the UK offshore oil and gas industry injury rate by 50%.

Suspended well
A well that has been capped off temporarily.

Trillion Cubic Feet (of gas).

Second-in-command of a drilling crew under the drilling superintendent. Responsible for the day-to-day running of the rig and for ensuring that all the necessary equipment is available.

The superstructure of a platform.

The exploration and production portions of the oil and gas industry.

United Kingdom Continental Shelf.

UK Flightshare
Initiative developed by LOGIC to permit the sharing of excess seat capacity on North Sea helicopter flights. Interested parties sign up via Deeds of Adherence enabling shares to take place between signed up parties on an ‘as arranged’ basis.

Vantage POB
LOGIC’s shared service to oil and gas operators for personnel and certification tracking at onshore and offshore installations.

The injection of water into an oil reservoir to ‘push’ additional oil out of the reservoir rock and into the wellbores of producing wells.

Well DataStore
Run by CDA, one of the largest shared online stores of digital well report and log data in the world.

The 1equipment at the surface of a well used to control the pressure; the point at which the hydrocarbons and water exit the ground.

Well log
A record of geological formation penetrated during drilling, including technical details of the operation.

Wet gas

Natural gas containing significant amounts of liquifiable hydrocarbons.

Wildcat well
A well drilled in an area where no current oil or gas production exists.

West of Shetland Isles.

Operations on a producing well to restore or increase production. A workover may be performed to stimulate the well, remove sand or wax from the wellbore, to mechanically repair the well, or for other reasons.

West Texas Intermediate, a type of crude oil commonly used as a price benchmark.