It will then be separated into its various components, such as natural gas liquids (ethane, propane, butanes and naphtha) and dry gas (methane). Kollsnes west of Bergen and Kårstø north of Stavanger are both processing plants for gas.

 

Put simply, the rich gas is heated at the bottom of a tall column. The lightest components evaporate and collect at the top of the tower, while the residue is sent to another column and reheated. This process continues until all the gas has been split into separate products.

 

The lightest (driest) gases are separated in an extraction plant, while the heaviest components go to a fractionation facility. Kårstø embraces both types of system. Dry (sales) gas is then piped on from the processing plant to customers in continental Europe.

 

The NGL and any condensate (light oil) are exported by special carriers from Kårstø, which receives 600-700 calls from such ships every year.

Gas products after processing.

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.

 

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.