Gullfaks subsea compressor nears installation
Statoil expects the world’s first subsea wet gas compression system to be installed offshore Norway next month.
Since last October, the equipment has been undergoing final system integration tests at Horsøy outside Bergen. Results to date have been very positive, Statoil says.
The company developed the equipment in collaboration withOneSubsea, which has delivered the compressor. It comprises a 420-metric ton (463-ton) protective structure and a 650-metric ton (716-ton) compressor station, incorporating two 5-MW compressors, and is designed to drive out a further 22 MMboe from the Gullfaks South Brent reservoir for export to the Gullfaks C platform.
The compressor station will be placed on the seafloor in a water depth of 135 m (443 ft) and connected to existing templates and pipelines 15 km (9.3 mi) from the Gullfaks C. OneSubsea has also supplied the associated new topsides equipment for power supply to and control of the subsea station.
Over the following months the connecting umbilical and the modules within the compressor station will be installed, followed by hookup to the platform this summer and start-up during the fall.
When the reservoir pressure falls below a critical level, subsea wet gas compression should help maintain high gas production.
Compression on the seabed is more effective than adding a conventional topsides compressor, which takes up extra weight and space on the platform, Statoil says. A wet gas compression facility does not require any treatment of the well stream prior to compression, allowing the use of smaller modules and simpler construction on the seafloor.
Statoil hopes the technology, combined with conventional low-pressure production in a later phase, will raise the gas recovery rate from Gullfaks South Brent from 62% to 74%.