Glossary

Different expressions used in the gas industry.

Natural gas
Natural gas comprises organically-derived, odourless and non-toxic gaseous compounds created by the decomposition of biological organisms. Consisting primarily of methane (75-95 per cent), ethane, butanes, propane and naphtha, these substances are built up from hydrogen and carbon atoms – hence the name hydrocarbons. A distinction is made between rich gas, dry gas and natural gas liquids (NGL).

Rich gas
This term applies to any blend of dry gas (methane) and NGL (ethane, butanes, propane and naphtha) transported through a pipeline. The Statpipe leg from Statfjord to Kårstø and the Åsgard Transport system from the Norwegian Sea to the same processing complex are examples of rich gas facilities.

NGL
Natural gas liquids are a collective term for various petroleum components which liquefy under small increases in pressure or reductions in temperature. Comprising ethane, propane, butanes and naphtha, and often containing small quantities of heavier hydrocarbons, NGL is shipped in special carriers.

Dry gas
This is a common term for natural gas which contains no liquid hydrocarbons under pressure. It consists largely of methane, but can also contain ethane. Norwegian pipelines carrying dry gas include Europipe I and Franpipe.

Shippers
Owners of gas to be transported through the pipelines operated by Gassco.

Scm
The usual abbreviation for standard cubic metre – a cubic metre of gas under a standard condition, defined as an atmospheric pressure of 1.01325 bar and a temperature of 15°C. This unit provides a measure for gas volume.

Gscm
Abbreviation for giga standard cubic metres, or one billion cubic metres under a standard condition, defined as an atmospheric pressure of 1.01325 bar and a temperature of 15°C. This unit provides a measure for gas volume.

LNG
Liquefied natural gas, or methane which has been converted to liquid phase by cooling it to -163°C. LNG is shipped in special carriers. One tonne of LNG corresponds to roughly 1 400 cubic metres of natural gas in gaseous form under a standard condition defined as an atmospheric pressure of 1.0132 bar and a temperature of 15C. In terms of volume, the ratio between LNG and gaseous methane is 1:625.

LPG
Liquefied petroleum gases consist of propane and butanes which have been converted to liquid phase through a pressure of roughly seven-eight bar or through some cooling. In Norway, LPG is synonymous with propane (95 per cent propane and five per cent butane) because the temperature properties of this gas suit the Norwegian climate. Special LPG carriers are used to ship these products.

Upstream
Collective term for activities which take place before crude oil leaves the (export) terminal or gas is piped from the processing plant. Exploration and field production are typical upstream operations.

Downstream
Collective term for all petroleum operations relating to refining, sale and distribution of products. These include the activities which take place after oil or gas leaves the (export) terminal to be processed, refined, transported and sold to consumers.

Gross calorific value (gcv)
This calorimetric unit is used to measure upper and lower (gross and net) calorific value. The upper (gross) calorific value is defined as the quantity of heat released through combustion at constant volume and with the water that arises from the combustion process in liquid form. The lower (net) calorific value is the quantity of heat released through combustion at constant pressure and with the water that arises from the combustion process in the form of steam.