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ABB powering up for ultra-deep substation

A seven-year joint industry project to develop subsea power technology is moving into a final phase this summer with full-scale prototype trials of a system that could enable up to 100 megawatts of power from shore to subsea developments in ultra-deepwater hundreds of kilometres offshore, writes Russell McCulley.

Electrification and automation giant ABB and JIP partners Equinor, Chevron and Total plan to carry out the 3000-hour shallow-water test of the subsea power substation in Vaasa, Finland, where ABB has a subsea transformer factory and where components of the prototype system were assembled.

Development of the subsea switchgear — a substation that can distribute power subsea — is key to the offshore oil and gas industry’s quest for the so-called subsea factory, which could enable fully automated, all-electric developments controlled and powered from shore.

Proponents say such developments would take workers away from harsh and hazardous offshore work and put them in safer onshore control centres.

A subsea power substation could also enable substantial cuts in greenhouse gas emissions, reduce development costs and boost recovery, they say.

Svein Vatland, vice president at ABB and director of the subsea power JIP, says upcoming shallow-water tests will include two full-scale prototype variable speed drives (VSDs), switchgear and a control and protection system all running in tandem.

The technology “has never been done before — the subsea substation or subsea VSD — and these are big VSDs”, he says.

“One VSD is capable of 9MVA (mega volt amp) — that’s around 6 MW, so you can run all the large loads we know of today.”

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ABB built and tested a full-scale prototype of the VSD in 2017.

The trial was “very successful” and allowed the JIP to proceed to this summer’s testing stage.

Electricity for the subsea power substation will be supplied via a single cable from shore or tied back to existing offshore infrastructure.

This is a much less costly option than multiple cables for each “load” or power demand source in a subsea production system such as a pump or compression system. ABB says the system could be used to power developments 600 kilometres from shore in depths up to 3000 metres.

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“The general trend we see is that the easy oil has been discovered, so more discoveries are further out and deeper down. And that is a very strong driver for going (with a) subsea (development),” Vatland says.

Operators are also looking for ways to cut greenhouse gas emissions, he notes.

“Being able to have AC power supplied from shore — in Norway you can tap into the national grid, but in general you could generate power in a much more environmentally friendly way than if you have local generation from gas turbines on a facility,” he says.

“That plays an important role on the emissions side of it.”

Placing the distribution system on the seabed, closer to the reservoir, reduces the amount of power consumption required, the company says.

Vatland says that a 600-kilometere step-out may be extreme but not unfathomable. In any case, he says, “we have the ability to do it and the equipment is qualified for that” once the JIP completes its work.

The system is designed for a 30-year field life.

“Reliability issues and pressure issues had to be addressed,” he says. At 3000-metre depths the components are subject to extreme pressure.

“All the equipment is oil-filled for pressure compensation,” Vatland says.

“All the components that go into the system have to be able to operate under extremely high pressure, in oil. So that was one of the big challenges we had to solve.”

Launched in 2013, the JIP coincided with one of the worst industry downturns in recent memory. But Vatland says the partners remained committed to the project.

“There were never any discussions about backing out, and that was really good,” he says.

“It also shows the need for it. This is really something that the industry wants. It’s a game-changer — it enables the development of fields that before were not economically or technically viable.”

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