Subsea power distribution systems will play a major role in the future of subsea field development projects. Once the Siemens Subsea Power Grid (SPG) is released to the market, the technology will increase tieback ranges massively and hike reserve recovery levels, the company told SEN.

This potential has seen Eni Norge join the SPG Joint Industry Program (JIP) this week.

The JIP is looking to “develop a complete subsea power network.” The effort is being led by Chevron with big hitters Statoil, ExxonMobil and Petrobras also participating.

“The JIP is one of the main initiatives in the offshore oil and gas industry for advancing large-scale subsea processing,” Siemens said.

“The SPG will provide oil companies with the tools needed to use subsea processing on a wider range of projects, including long step-outs, deepwater (more than 3,000 m [9,843 ft])and in remote areas. Ultimately, the SPG will be a key enabler for building the full subsea factories of the future,” the company added. “Siemens Subsea power solutions also provide opportunities for oil companies to achieve increased oil recovery from existing fields, thus maximizing the return for clients, while ensuring recoverable resources are not left in the ground.”

Overcoming Setbacks

While the SPG has had its setbacks—not least with the collapse of the oil price in mid-2014 that put pressure on operators’ budgets and Siemens Subsea proposing a global business restructuring in November 2016 “to adjust to current market situation”—Siemens is now in the final qualification stage for the product and has assembled a prototype that is being tested at the purpose-built Siemens Subsea Technology Center in Trondheim, Norway.

The main component that Siemens is testing is a subsea transformer, which takes high voltage AC power and transforms it down to a medium voltage. Then a medium voltage switch gear is used, which connects and disconnects the different consumers of power. Next the third main part comes into play: the variable speed drive (VSD), which controls the speed of the pump.

This summer Siemens plans to start system integration tests. Once these are completed successfully, the company will move the equipment to a test location in Trondheim Harbour, where the equipment will be tested at shallow depths.

Deepwater Qualification

“The SPG is being qualified for 3,000 m water depth and will be offered to oil and gas operators on a global level. This is somewhat exemplified by the global reach of the JIP partners,” Siemens told SEN.

The company added that its goal with the SPG is the “development and qualification of a complete subsea high-voltage power distribution system including subsea transformer, subsea switchgear, subsea VSD, power control system and interconnection between the different units (wet mate HV connectors).

“This is an extensive development program that started in 2010. Siemens and the JIP partners have all contributed significant expertise and resources into the program, but specific values are not made public,” Siemens added.

Key Enabler Potential

“Subsea power will be an important tool and in some instances it will be the key enabler to apply subsea processing (boosting, compression, water injection and separation) on more fields,” Siemens said.

Called a key enabler for very long subsea tieback projects, Siemens SPG will allow transmission and distribution of power for a subsea field 200 km (124 miles) from the topside or onshore host facility once complete, the company said.

Currently the longest subsea processing tieback is the Åsgard project at 45 km (28 miles).

“Subsea power distribution will improve economics on projects with multiple power consumers [reduced cable cost]. Placing power equipment on the seabed can be an enabler for subsea processing on brown field projects and tying in additional satellite fields where the host is running out of available space/weight to add additional heavy equipment,” the company added.

Next Phase Of Subsea Processing

Siemens’ head of subsea power Bjørn Rasch said the next phase of subsea processing technology is to distribute power more effectively at the seabed.

He said the Siemens SPG would be able to deliver “a genuine subsea to market solution where you actually produce from the well all the processing that you need to transport the oil directly to the market.”

Companies could then power all this subsea processing directly from the shore.

“You won’t need any offshore installation at all,” Rasch added, noting the significant cost reduction, recovery increase and safety implications that the technology will be able to offer.

He also said that in some deepwater projects there could be several consumers with “very complicated power needs and very expensive cable costs.” The use of a subsea power distribution system could reduce the number of cables needed that to go from topside to subsea, he added.

—Steve Hamlen