Turbine boost pays off

November 12, 1999, 08:00 CET

A five per cent output boost for a turbine on Statoil's Heidrun field in the Norwegian Sea has yielded an equivalent increase in production.

Based on overall oil output so far this year and an oil price of USD 20 per barrel, this improvement also equals a five per cent rise in Heidrun revenues for 1999 – or NOK 570 million.

That corresponds in turn to roughly 88 per cent of the operations budget for the year, reports staff engineer Kyrre Langnes, in charge of rotary equipment on the Heidrun platform.

Capacity in the export gas compressor represents the bottleneck in expanding Heidrun production. This unit is driven in turn by a gas turbine claimed by manufacturer Rolls-Royce to be the world's only unit of its type to run continuously at such a high load.

"Rolls-Royce was dubious about boosting output from this turbine when we proposed it two years ago," says Mr Langnes.

"Increasing output means higher heat loads on the unit, which could reduce its operating life."

However, the offshore climate proved to have a cooling effect on the turbine, which has been running for roughly 20 months so far without problems and ranks as one of Statoil's most reliable power units both before and after the output boost.

Mr Langnes notes that operating a turbine so close to its physical limits calls for detailed surveillance to ensure that no unnecessary loads are imposed. Continuous condition monitoring is required.

A detailed evaluation of experience so far will be carried out in connection with a scheduled overhaul.

Plans call for the turbine to continue running at top load until 2001 in the first instance. Mr Langnes says it will probably go on operating also beyond that period.