The subsea factory could be here sooner than many believe and Danish firm Danfoss is helping drive the innovation that will make it happen. Emma Gordon reports.
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Chemical inhibitor system. |
Danish pumping technology is at the forefront of industry efforts to make standalone subsea production facilities, also known as subsea factories, a reality during the next five years.
The concept is widely acknowledged as a potentially economical and practical way to exploit remote reservoirs, as well as those in harsh and deepwater environments.
As part of this drive, Danfoss High Pressure Pumps has been working with Statoil since 2013 to adapt its chemical liquid pump (CLP). The CLP has been developed, assembled and tested at Danfoss’ Nordborg site in South Jutland, for use at depths of around 3000m as part of a subsea hydraulic power unit (SHPU) to control subsea Xmas tree valves. Danfoss, which has more than 40 years’ experience developing and producing axial piston pumps, completed the axial piston pump redesign to Statoil’s specifications in 2014. It was already the subject of more than 20 patents and is using super duplex steel, carbon-reinforced polyetheretherketone (PEEK) thermoplastic, as well as highly corrosion-resistant metal alloys for the springs.
Two third-party organizations tested the pump: Netherlands-based Seatools and DNV GL. It achieved technology readiness level (TRL) four. This means its ability to meet the operator’s requirements, including a stipulation that it would run in the subsea environment without maintenance for 20 years, has been validated in the laboratory.
“Using the SHPU, which really will be the first of its kind, means the umbilical to the Christmas tree only needs to house communications and power,” says Michael Klysner, Danfoss High Pressure Pumps global director of oil and gas. “Everything else is catered for on the seabed, meaning a much smaller, simpler and cheaper umbilical—reduced from around 25cm in diameter to about 7cm.”
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MAG-Drive pump. |
Work is continuing on the development of international standards for this subsea technology, but no other pump is qualified to the exacting Statoil criteria or able to fulfill the API 674 and 675 standards and the relevant NORSOK specifications, he says.
Each pump has pistons running forward and backward against an angled swash plate with integrated port and valve plates controlling flow in and out of the assembly. When the swash plate pushes the pistons up, pressurized fluid is pumped out of the bore. “Our pump is proven to work in extreme circumstances and hostile environments,” Klysner says. “Compared to competitors’ topside units, it’s much smaller and lighter. It weighs just 275kg compared to 25-tonne and uses 20 times less space.”
In 2005, Danfoss took the axial pump principle and adapted its equipment in line with the international API 675 and 674 standards.
“Our track record is encouraging,” he says. “The first API-standard pump was commissioned in a closed-drain system in Vietnam in 2007 and has not needed maintenance since.”
He adds that discussions are underway with two operators working together to modify the pumps for subsea chemical injection, which is another step toward stand- alone subsea production systems that could be tied back to an FPSO or facilities onshore.
“This is a massive opportunity,” Klysner says. “The cost saving to put everything on the seabed is so big compared to traditional developments that it is fast becoming a real area of focus for the industry.
“I believe when the sector gets over some hurdles around storage and instrumentation, things will start to move very fast. We could even see platforms on the seabed as early as 2018,” he says.
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