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Pressure boost for Troll Gas

October 3, 2005, 01:35 CEST

Production capacity on Statoil’s Troll A gas platform in the North Sea rose on 1 October from 85 million cubic metres per day to 110 million following completion of the precompression project.

Brought in on schedule and to budget, this development boosts pressure on the installation and allows it to deliver up to 27 billion cubic metres of gas per year.

That in turn strengthens the role of Troll as a swing producer, allowing the field to act as a buffer against seasonal variations in gas demand.

Declining pressure in the Troll reservoir means that more compression is needed to help drive gas production through the pipelines to the processing plant at Kollsnes near Bergen.

Two compressors have accordingly been installed on the A platform, and new technology allows these units to be powered from land.

That in turn means zero carbon dioxide and nitrogen oxide emissions from the installation or the processing plant.

“Without electricity from land, the new compressors would need to be powered by gas turbines on Troll A,” explains Geir Amland, operations vice president for Troll/Kvitebjørn.

“That would have released about 230,000 tonnes of carbon dioxide and 230 tonnes of nitrogen oxide annually.”

Electricity is transmitted to the platform through high voltage direct current (HVDC) cables specially developed and delivered by ABB.

A transformer/rectifier station has also been built at Kollsnes, which in turn greatly reduces space requirements on the platform.

Before this solution was adopted on Troll, Statoil carried out studies to determine whether the technology was feasible in an offshore context.

“This represents a very successful outcome for the licensees, who dared to commit to a new application for an environment-friendly technology,” says Mr Amland.

Investment in the project is NOK 3.6 billion. On stream since 1996, Troll A is the only Norwegian offshore platform to be powered from land.