In the U.K. “keeping the lights on” is a phrase we have become used to over the last few years as concern spreads over a possible gap between power supply and demand toward the end of this decade.

Those of us old enough to remember the 1970s, three-day weeks and prolonged power outages will hope we don’t face a return to the dark days.

But if we are struggling to keep the power supply running to our homes, how can we expect to keep subsea equipment fi red up? There are a number of companies out there focusing on exactly this problem.

As Stuart Ellison, director of Exnics, explained, “We have been looking at potential sources of power at the well site. You have solar, wind, waves, tidal, all those kind of things, but we realized nobody is really looking at the geothermal energy a subsea well produces.

“Wells are deep. The reservoirs are some distance below the [surface]. As the hydrocarbons rise up the well to the seabed, the sea is very cold, and you get a big thermal difference at the mud line. We think that is something we can exploit for energy.”

Ellison said the heat in the fl uids could be harvested and the power used to run wellsite systems and control systems.

He used the example of the U.K. North Sea Devenick Field, a two-well 34-km (21-mile) tieback.

“There is quite a long umbilical here, and it is quite a hot well at 140 C [284 F]. There is a tremendous amount of geothermal energy that these two wells produce, over 7 MW of heat.

“That is quite a lot of power to have, especially when you are having to bring power from the topsides from so far away.”

The Exnics solution is to harvest the heat through thermoelectric “hot rings” fitted onto the flowline and then to store the power in lithium ion batteries for future use.

“Because there is such an enormous amount of heat, you can get away with quite low efficiencies,” he added.

The technology is currently being trialed with the first field applications not too far away.

Other technologies to enable remote subsea power hubs to be developed also are emerging.

Ocean currents are at the heart of plans being developed by Aberdeen-based East Coast Oil and Gas (ECOG). The company has designed a 2-m (6.5-ft) across hub that contains turbines that cut in at current speeds of 0.4 m (1 ft) per second and can produce 500 watts.

EC-OG’s Managing Director Richard Knox said, “We believe things are moving toward the autonomous subsea well. Keeping a subsea well operational only needs a maximum of 100 watts to keep the subsea control module up and running and keep the oil and gas flowing, effectively keeping the lights on for us.”

The company has a full-scale remote subsea power hub about to undergo testing at the Underwater Centre in Fort William, Scotland. Could this be the answer?

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