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The Gullfaks wet gas compressor. Image courtesy of Harald Pettersen/Statoil.

Statoil started up the world’s first ever subsea wet gas compression project on Monday at its Gullfalks field in the North Sea.

The technology is expected to increase recovery by 22 million barrels of oil equivalent and extend plateau production from the Gullfaks South Brent reservoir by about two years, Statoil said.

Statoil is the first company to apply subsea gas compression at one of its projects.

“The recovery rate from the Gullfaks South Brent reservoir may be increased from 62% to 74% by applying this solution in combination with other measures,” says Kjetil Hove, senior vice president for the operations west cluster,” Statoil senior vice president for the operations west cluster Kjetil Hove said.

Wet gas compressors do not require gas and liquid separation before compression, allowing the system to be streamlined considerably and requiring smaller modules and a simpler structure on the seabed.

Subsea compression also has a “stronger impact” than conventional platform-based compression and avoids adding extra weight and clutter on the compression module’s platform, the Norway-based company added.

The Gullfalks system consists of a 420 ton protective structure, a compressor station with two five-megawatt compressors totaling 650 tons and all the equipment needed for power supply and system control on the platform.

Extensive preparations were made on Gullfaks C before the subsea compressor could be started, including modifications and preparation of areas as well as equipment installation.

The company can also tie in other subsea wells to the wet gas compressor through existing pipelines.

The Gullfaks station has already been prepared for new tie-ins.

“We see great opportunities for wet gas compression on the Norwegian continental shelf. It is an efficient system and a concept that can be used for improved recovery on small and medium-sized fields. We are searching for more candidates that are suitable,” Hove added.

In mid-September Statoil started up the Åsgard subsea gas compression project.

The two projects are the first of their kinds in the world and use two different technologies for maintaining production when the reservoir pressure drops off after a certain period.

Statoil operates and holds a 51 percent stake in the Gullfaks license. Norway’s Petoro holds a 30 percent stake and Austria-based OMV holds a 19 percent stake.