This week, OneSubsea® officially handed over the subsea Multiphase Compressor, the world’s first and only true wet gas compressor, to Statoil for the Gullfaks field located in the North Sea. The main driver in the development of the multiphase compressor was to increase recovery rates and to cost-effectively increase the tieback distances of subsea gas fields. The recovery rate for the Gullfaks South Brent reservoir is expected to increase by 22 million barrels of oil equivalent by using the wet gas compression system.
Work on the subsea multiphase compressor began in 2009 when Statoil awarded an extensive Technology Qualification Program (TQP). In 2012, the contract for delivery of a complete subsea compression system based on the qualified multiphase compressor, was awarded. Subsequently, OneSubsea and Statoil have worked in collaboration to develop this one-of-a-kind technology.
“Statoil is a leading oil company in developing new subsea technologies through their subsea factory strategy,” Mads Andersen, President of Processing Systems at OneSubsea, said. “Subsea compression is an important building block here, and we are pleased to have been selected to work with Statoil over many years to finally bring this technology to the market.”
A 2015 OTC Spotlight on New Technology Award recipient, the subsea multiphase compressor is the world’s first and only true wet gas compressor with no requirements for an upstream separation facility or an anti-surge system, which greatly simplifies the subsea system requirements. The compressor is a contra-rotating machine specifically designed for pressure boosting of unprocessed wellstream. This unique configuration allows for a compact and robust design that is easy to install by use of light intervention vessels, and is based on the well-proven design developed for subsea booster pumps.
“Our subsea wet gas compressor is built on the same principle as our well-tested and robust subsea multiphase pumps. We expect similar performance and reliability stats as on our pumps, which currently run in excess 15 years mean time between failure (MTBF),” Andersen said.
The wet gas compressor station consists of a 420-tonne protective structure with two, five-megawatt compressors totaling 650 tonnes, and all of the necessary topside equipment for power supply and control. Installation is expected Q2 with start-up planned for the fall. The station will be installed at 443 ft (135 m) water depth and tied into existing templates and pipelines 9 mi (15 km) from the Gullfaks C platform.