Endurance Energy drills first subsea geothermal well at Axial Seamount

Endurance Energy cased and cemented what it called the world’s first offshore geothermal well during a three-week test of its Adélie subsea power system at Axial Seamount, about 300 miles off the Oregon coast.

Using a subsea lander drill in the Axial Caldera, in about 5,000 ft of water, the Seattle-based company bored two holes less than 2 ft apart, and both encountered hydrothermal fluid. The second hole was cased, cemented and capped with a valve, producing a 16 m well that flowed at 260°C after cementing. Drilling used filtered seawater instead of drilling mud.

The well proved too restrictive to run the plant, so the 3-ton Adélie unit was connected to a nearby natural vent flowing at about 281°C. There it generated net-positive power for 8.7 seconds, peaking at 16.5 kW net, before battery overcurrent protection stopped it, and a failed power cable ended the dive on a restart attempt.

Endurance will deploy an upgraded unit, Gentoo, this winter, and its current lander drill can reach 80 m. The company is also developing its first commercial project in Tonga, targeting first power in 2027.