The World's Hottest Borehole Is Being Drilled Into a Volcano

The Iceland Deep Drilling Project is tapping steam so hot and so pressurized, its power potential is ten times that of conventional geothermal wells.

When finished, it's expected to be the world's hottest borehole, a shaft more than three miles deep, drilled into the rifted margin of the Mid-Atlantic Ridge. Here, two of the planet's main tectonic plates, the North American and Eurasian, are tearing apart as deep molten rock pushes up from beneath. This is Iceland, the land of volcanoes and geysers, a steamy hotbed of unlimited geothermal energy that the country already taps to produce electricity for its residents.

But the Iceland Deep Drilling Project represents a step up from conventional geothermal energy sources because it aims to tap 900-degree F "supercritical" steam - steam so hot and so pressurized, it's neither gas nor liquid. But its power potential is ten times that of steam from conventional geothermal wells. This one could generate 45 megawatts of electricity, enough to power 50,000 homes.

"If this works, in the future we would need to drill fewer wells to produce the same amount of energy, meaning we would touch less surface, which means less environmental impact and hopefully lower costs," the project's CEO Asgeir Margeirsson told the BBC.

And a successful project in Iceland could mean improved geothermal power techniques for other countries with volcanic regions, like the United States. According to a recent assessment by the US Geological Survey of our country's geothermal resources, the electric power potential of known sites is more than 9,000 MW, and 30,000 MW from yet undiscovered sources.

The Icelandic borehole, dryly named IDDP-2, is the country's second attempt to access supercritical steam. The first attempt occurred in 2009 with the IDDP-1 well drilled in the Krafla volcanic region to Iceland's north. The shaft reached only 1.3 miles before striking a reservoir of magma.

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Before the team abandoned the site, its scientists ran multiple tests on the well and found that the steam there reached about 840 degrees F, and for a while, that site held the record for the hottest borehole. At that temperature, the hole would have produced enough steam to create 36 MW of electricity.

Now, IDDP-2 appears on track to beat that record. It was actually drilled five years before the one at Krafla, but as a more shallow borehole - one of many drilled into the Reykjanes peninsula on the island's southwest corner. At the time, it penetrated Earth's crust to a depth of 1.55 miles. But then the IDDP decided to deepen it with the goal of reaching 3.11 miles, which they hope to achieve by the end of this year.

The drilling project, run with a rig nicknamed "Thor," could also contribute to a fundamental understanding about how volcanoes work. Much of what geologists know about volcanoes comes from above-ground studies such as sampling rock, monitoring seismic waves and other indirect observations.

"But actually, we have very few in situ measurements of what the interior of a volcano looks like," Prof Freysteinn Sigmundsson, a volcanologist at the University of Iceland, told the BBC.

Because the drilling project is a collaboration between scientists, industry and the Icelandic government, the borehole could produce the data that provides an inside look.

It could be a bit longer before the world's hottest borehole is producing steam for Icelandic residents. Once the drilling is completed, the project will enter a two-year test period.