World’s first subsea compressor units reach 100,000 operational hours
Equinor has awarded MAN Energy Solutions a new contract to supply a subsea compressor unit for the Åsgard gas field in offshore Norway. The compressor system will be deployed at the active field in order to enhance production and extend the field’s lifetime, according to the company's release.
Åsgard became the world’s first subsea gas-compression facility to commence operation 300 meters below sea level in 2016. It features two MAN Subsea HOFIM® motor-compressor units that have run for more than six years, accumulating 100,000 operational hours without any intervention and with an availability of close to 100%.
Subsea gas-compression is a lower-carbon alternative to conventional compressor solutions installed on platforms at sea level. The size and weight of the subsea solution is significantly smaller than a platform infrastructure, resulting in a reduction in the requirement for steel and other materials. Health and safety risks are also minimized by the remote operation of the subsea technology.
In close cooperation with Equinor and Aker Solutions, the existing subsea compression modules at Åsgard are being upgraded to accommodate a higher compression ratio, thus maintaining output and enhancing recovery as the gas reservoir’s pressure naturally declines. The need to further develop the subsea compression technology was identified early on as part of the initial Åsgard Subsea Compression project. The aim is to safeguard the total, additional production of around 306 million barrels of oil equivalents.
MAN Energy Solutions’ scope of supply for the new order comprises a Subsea HOFIM® compressor unit – with compressor frame size RB 45 – with an integrated MAN motor, size M43. To increase the overall pressure-ratio capability, the unit features a new, overhung compression stage on the opposite side of the motor. The motor compressor unit is designed for continuous liquid injection, making it a wet-gas compression solution. It will be developed, manufactured and tested at MAN’s premises in Zurich, Switzerland, with delivery planned for March 2023.
The Subsea HOFIM® compressor has been specifically adapted for underwater use with all components designed to for maximum robustness to counteract the risk of corrosion inside the machinery. Hermetically sealed and oil-free, the system employs seven-axes active magnetic bearings and a high-speed motor. This design dispenses with a large number of components typically seen in conventional topside compressor solutions, including the gearbox, lubrication-oil system, instrumentation and valving.
