The world's first and only true subsea wet gas compressor
The OneSubsea Multiphase Compressor, a 2015 OTC Spotlight on New Technology Award winner, is the world’s first and only true subsea 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, developed in collaboration with Statoil and Shell, 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.
The subsea multiphase compressor is capable of handling high liquid contents without mechanical issues, with gas volume fractions typically in the range of 95% to 100%. This compressor represents a breakthrough in the subsea environment as it enables compression of the unprocessed wellstream without any need for pre-processing. This will enable deployment of simplified subsea systems at lower capital expenditures and field development costs.
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 Gullfaks field, operated by Statoil and located in the North Sea, will see the first commercial deployment in the world for subsea wet gas compression. Statoil foresees that the recovery rate will increase by 22 million barrels of oil equivalent, by using the wet gas compression system. The wet gas compression station for Gullfaks will be installed approximately 15 km away from the Gullfaks C platform; commissioning is planned for 2015.
Some key advantages of the multiphase compressor, which enables cost-efficiencies and significantly improved operational performance, include:
- Continuous operation on all liquid fractions (0 – 100%)
- Operates in all flow regimes
- Standard fluid film bearing technology
- Surge-free operation so no anti-surge system is required
- Sand and solid tolerant design
- Low speed allow for long step-out without subsea VSDs
- Low module weight (approx. 60 t) allow for light vessel intervention