Gjøa: one of the most modern semisubmersible production platforms ever built

Gjøa is a field with estimated reserves of 82 million barrels of oil and condensate and 40 billion cubic metres of gas. The nearby Vega field, a satellite development, has estimated reserves of an additional 26 million barrels of condensate and 18 billion cubic metres of gas.

Gjøa is among the largest recent field developments in the North Sea. It is the first floating platform to be supplied with electric power from shore, enabling a significant reduction in emissions.

The field is being developed using a mobile, semi-submersible production platform and five subsea templates. Aker Solutions carried out the front-end anddetail design and engineering for the topside and hull as well as the procurement, construction and hook-up of the topside. We also carried out the installation of the mooring system before we transported the platform, installed it in the North Sea and supplied the platform’s steel tube umbilicals.

The mating of the 20 000 tonne topside, covering an area similar to a soccer field, and the 15 000 tonne hull was successfully carried out outside Aker Solutions’ yard at Stord in Norway in December 2009. The mating had to be carried out within tolerances of just 25 millimetres (1 inch) in all directions.

“I am impressed by this operation. It was well planned, safe and efficient and carried out with the utmost precision,” says Statoil’s project manager, Kjetel Rokseth Digre. Gjøa licensees are GDF Suez E&P Norge, Petoro, Statoil, Shell and RWE Dea. Statoil is the operator in the development phase, while GDF Suez E&P Norge will assume the role of operator at the start of production.