Accumulation
One or more occurrences of oil or gas confirmed by tests, samples or logging.
Appraisal well
A well drilled to determine the extent and scope of a petroleum find.
Associated gas
Natural gas produced together with oil.
Barrel
Oil production is often given in numbers of barrels per day. One barrel of oil = 159 litres, 0.159 cubic metres. In English the abbreviations bll (barrel) or stb (stock tank barrel) are often used.
Barrels of oil equivalents
Unit of volume for petroleum products. Used when oil, gas and NGL are to be summarised. Abbreviated BOE in English. Also see oil equivalents.
bll (barrel)
See barrel.
Block
A country’s exploration and production area is divided into different blocks that indicate the geographic layout. In the Norwegian section of the North Sea, for example, one block is 15 nautical miles wide and 20 nautical miles long, which corresponds to an area of approximately 575 square kilometres.
Blow-out
Uncontrolled release of oil, gas or water from an oil well.
BOE
Barrels of oil equivalents
BOEPD
Barrels of oil equivalents per day.
BOPD
Barrels of oil per day.
Brent oil
A reference oil for the various types of oil in the North Sea, used as a basis for pricing. West Texas Intermediate (WTI) and Dubai are other reference oils.
cf
Cubic foot/feet.
cm
Cubic metres.
CNG (Compressed natural gas)
International designation for dry gas or natural gas under pressure in a tanker.
Concession round
Distribution of blocks in a country is done in connection with a concession round under the direction of state authorities.
Condensate
A mixture of the heavier elements of natural gas, i.e. pentane, hexane, heptane etc. Is a liquid at atmospheric pressure. Also called natural gasoline or nafta.
Continental shelf
A gradual, rapidly deepening seabed on a continental plate. Generally situated at a depth of 0-500 metres and is concluded in a continental slope. The ocean area between UK, Denmark and Norway is for example a continental shelf.
Crude oil
The oil produced from a reservoir, after associated gas is removed in separation. Crude oil is a fossil fuel formed by plant and animal matter several million years ago.
Cubic foot
Unit of volume for gas, most often given in billions of cubic feet.
Cubic meter
Unit of volume for gas, most often given in billions of cubic metres.
Drill bit
Sits on the tip of the drill pipe and has rotating teeth that drill through the bedrock.
Drilling mud (drilling fluid)
Fluid used to lubricate and cool the drill bit and prevent the walls of the well from collapsing. Keeps the flow of oil or gas under control and transports the matrix to the surface. The fluid used is a mixture of water or oil, clay and chemicals.
Drill pipe
Steel pipe that links the drill bit and the drilling platform. The drill pipe consists of connected pipe lengths. The pipe rotates and is also the pipeline for the drilling mud during the drilling operation.
Drilling derrick
The steel tower where the drill pipe is raised/lowered, mounted/dismounted and held in place during drilling operations.
Exploration well
A common term for wildcat and appraisal wells drilled when exploring for oil and gas, to gather facts about the petroleum’s quality, the bedrock’s make-up, the reservoir’s extent and location etc.
FPSO vessel
Floating, Production, Storage and Offloading vessel used at an oil field.
FDPSO vessel
An FPSO with drilling capacity.
Flaring
Controlled burning of gas that must be released for safety reasons at an oil production facility. Used when impossible to utilise the gas.
Gas field
A field containing natural gas, but only minor amounts of oil. The gas can contain larger or smaller amounts of condensate that is separated as a liquid when the gas is produced (the pressure and temperature drop).
GSm3
Giga standard cubic meter. Volume unit for gas. Equals 1 billion cubic metres of gas at an air pressure of 1.01325 bar and 15 °C.
Hydrocarbons
The compounds comprised of the basic elements hydrogen (H) and carbon (C). If an occurrence primarily contains light hydrocarbons, they are most often in gas form in the reservoir, and are then called a gas field. If it is primarily heavy hydrocarbons, they are in liquid form in the reservoir, and called an oil field. Under certain conditions both can exist in the reservoir where a gas cap lies above the oil. Oil always contains a certain element of light hydrocarbons that are freed in production, also known as associated gas. Injection well A well where gas or water is injected to give pressure support in a reservoir. By injecting gas or water (or both), the degree of recovery can be increased as the pressure is maintained by the injection, the hydrocarbons are pushed into the production well.
Injection well
A well where gas or water is injected to give pressure support in a reservoir. By injecting gas or water (or both) the degree of recovery can be increased. As the pressure is maintained by the injection, the hydrocarbons are pushed into the production well.
Jackup rig
A type of installation used when drilling oil wells at sea. It is fixed to the seabed.
Leads
Leads are possible accumulations of hydrocarbons where more geological data needs to be gathered and evaluations need to be performed before they can be called prospects, where drilling is considered to be feasible.
License
A permit to search for and produce oil and gas. Oil and natural gas assets are usually owned by the country in which the accumulation is discovered. The oil companies obtain permission from the respective country’s government to explore for and extract oil and natural gas. These permits can be called concessions, permits, production sharing agreements or licenses depending on the country in question. A license usually consists of two parts an exploration permit and a production license.
LNG (Liquefied natural gas)
Liquid dry gas, primarily methane, that has transformed to liquid form upon cooling to minus 163 °C at atmospheric pressure. One ton of LNG corresponds to approximately 1,400 cubic metres of gas. LNG is transported by special vessels.
Natural gas
A mixture of hydrocarbons in gas form found in the bedrock, usually 60-95 percent methane.
NGL (Natural gas liquids)
Liquid gas that consists of three different gases ethane, propane and butane, as well as small amounts of heavy hydrocarbons. Is partially liquid at atmospheric pressure. NGL is transported by special vessels.
Observation well
A well that is equipped with pressure sensors and other measurement instruments to collect additional information about a reservoir. Occurrence An accumulation of petroleum in a geological unit. Delimited by rock types, a contact surface between petroleum and water or a combination of these.
Occurrence
An accumulation of petroleum in a geological unit. Delimited by rock types, a contact surface between petroleum and water or a combination of these.
Offshore
Designation for operations at sea.
Onshore
Designation for operations on land.
Oil equivalents (o.e.)
An volume unit used when oil, gas and NGL are to be summarised. The concept is tied to the amount of energy released upon combustion of different types of petroleum. Because oil equivalents depend on the amount of energy, it is not constant and different conversion factors are used. In “Oil Field Units”, 5,800 cubic feet of gas = 1barrel of oil equivalents. According to the Norwegian Petroleum Directorate, 1,000 standard cubic metres of gas = 1 standard cubic meter of oil equivalents.
Operator
A company, which on behalf of one or more companies in a partnership, has obtained the right to explore for oil and gas in an area and develop a field for production in a commercial accumulation.
OSS vessel
Oil Storage Service vessel
Petroleum
Collective term for hydrocarbons, whether they occur in solid, liquid or gas state(s).
Platform
An installation used during the production of oil or gas, and for exploration. Oil operations at sea are conducted from both floating platforms and platforms fixed to the seabed.
Produced water
Is the water pumped up from an oil well together with oil, gas or other hydrocarbons. The water is separated from the hydrocarbons and purified before it is pumped back down into the reservoir or taken care of in another manner.
Production sharing agreement
See Licens.
Production well
A well used to extract petroleum from a reservoir.
Recovery forecast
A percentage that indicates how much of the proved, existing reserves are possible to produce.
Refinery
A facility where crude oil is converted to refined products such as petrol, motor oil and bitumen.
Reservoir
An accumulation of oil or gas in a porous type of rock, such as sandstone or limestone.
Seismic data
Seismic investigations are made to be able to describe geological structures in the bedrock. At sea, sonar signals are transmitted from the ocean surface (pings), and the echoes are captured by special measurement instruments. Used to localise occurrences of hydrocarbons.
Sm3
Volume unit for gas. Standard based on the volume at an air pressure of 1.01325 bar and 15 °C.
Terminal
A land-based facility that receives and stores crude oil and products from oil production at sea. The oil is transported to the terminal by tanker or through pipelines.
Ton oil
One ton of oil is equivalent to 7.5 barrels, depending on the oil’s density.
Well
A hole drilled down to a reservoir to look for or extract oil or gas.
Wellhead
The equipment (outlets, valves, etc.) that is fastened to the top of a well to prevent blowout.
Wildcat well
The first well drilled when exploring for oil and gas on a new, defined geological structure (a prospect).