Science & Environment

Giant gas platform sinks below waves

A structure the size of a soccer pitch has been sent plunging to the bottom of the ocean 125 miles off Norway.

It will house a giant compressor claimed to be the world’s biggest offshore machine.

The Statoil equipment has been designed to pump some $30bn worth of gas from a depleted gas field.

It’s a technological leap for Statoil to place the compressor on the sea bed instead of on a typical platform perched above the waves.

But environmentalists say as a state-owned enterprise, Statoil should concentrate on saving carbon emissions rather than seeking more hydrocarbons.

This megaproject is a gamble. Statoil say for the same price as a compressor on a platform - $2bn - they can retrieve more gas using 30-50% less energy with a compressor on the sea floor, nearer to the gas deposit.

“We are very excited about this,” Margareth Ovrum, who’s overseeing the project, told me at the construction yard in Egersund near Stavangar.

“This is a really major leap in technology. We are very proud of it and we are confident that it’s going to work.”

The underwater giant will be serviced by robots. The trickiest part of the operation will be keeping the electrics dry when the compressor’s plugged in.

If it all succeeds, Statoil engineers dream that one day they may dispense with oil and gas platforms altogether and place entire drilling operations on the sea bed.

This would open the possibility of drilling in ever deeper water, and also possibly in the Arctic where icebergs would pass overhead if the water is deep enough.

Environmentalists in Norway are angry that Statoil is trying to retrieve more fossil fuels when experts say we can safely burn just a third of what we have already found.

Truls Gulowsen from Greenpeace, Norway, told BBC News: "It may make commercial logic for Statoil to maximise production from this field, but fossil fuel companies and governments are stuck in the mindset that they have to retrieve every last barrel.

“Norway has been a leader in clean technology. The (Norwegian) government should insist that it turns its technology investments to renewable energy systems and doesn’t keep pressing ahead with a strategy that will destroy the climate.”

Statoil is actually a leader in developing carbon capture and storage technology that might allow the world to carry on burning fossil fuels, but the project is a poor relation compared with the prestigious adventure under the waves.

A couple of hours drive north of Stavanger lies the experimental Mongstat technology centre where a consortium of firms led by Statoil is testing two types of carbon capture equipment on two types of exhaust.

The units use amine and ammonia on exhausts from a gas-fired power station and an oil refinery (which has a similar composition to exhaust from a coal-fired power station).

Frank Ellingsen, who runs the centre, says it needs much more investment in different types of technology from different companies to bring the costs down.

He told me: “We know we can capture 90% of the CO2 (from the exhausts) but it’s far too expensive. If governments really want this technology to work they will have to put policies in place to make it work.”

But there appears little international will to force carbon capture into the mainstream and the technology is years behind schedule.

One of Frank’s colleagues at the technology centre put it in a nutshell: “There’s a clear commercial logic to the underwater compressor,” he told me. “We can make tens of billions of dollars."

“We’re an oil and gas company – of course people are excited by a massive operation like that on the sea bed. Do you see that level of excitement about capturing the CO2 that’s emitted? Of course you don’t.”

Follow Roger on Twitter

More on this story