Scaling geothermal energy with horizontal drilling

Posted: April 21, 2025

Four and a half billion years ago, a nebula of gas and dust, pulled together by gravitational force, collided and amassed together to form the Earth. That initial accretion of material created enormous amounts of heat—and the Earth has been radiating it ever since. It’s cooled down somewhat over the last several billion years, but underneath the Earth’s surface, it’s still very hot. Adding to that heat is the radioactive decay of elements like uranium, thorium and potassium.

The heat under the Earth’s surface could theoretically provide energy to 8 billion people for another 17 billion years. Considering that the Sun is expected to make the Earth uninhabitable in about 1 billion years, geothermal energy could provide us with all the energy we’ll ever need. All we need to do is drill down a couple of miles below the surface, where temperatures can reach 350-450 degrees Fahrenheit, depending on the location.

Until recently, geothermal energy was only commercially viable in particular locations where fissures in the Earth’s crust allowed us to access the heat radiating up from under the surface.  Iceland is a prime example, where its position on the Mid-Atlantic Ridge creates exceptional geothermal resources. The country currently gets 66% of its energy—and 25% of its electricity—from geothermal. Tuscany is another geothermal hotspot. The world’s first geothermal electric plant was built in the Larderello area of Tuscany in the early 1900s and to this day, Italy remains Europe's largest producer of geothermal electricity outside of Iceland.  

But now, the horizontal drilling techniques that allowed fracking to uncover oil and gas from previously unreachable reservoirs are helping companies generate electricity with geothermal plants in previously unviable locations.

How horizontal drilling makes geothermal commercially successful

The basic principle is to drill 2.5 km (1.5 mi.) or so below the surface, where temperatures can reach over 150 C (302 F) and more. You then pump cold water down to that heat reservoir, where it heats up, then flows back to the surface where it’s used to drive turbines that generate electricity. The cooled water can then recirculate below the surface in a closed loop. The resulting electricity can be completely carbon-free.

The trouble with installing geothermal plants in areas that aren’t natural hotspots is that you can sink millions of dollars into drilling a vertical hole that it turns out won’t get enough water hot enough to power the turbines.

That’s the challenge that Fervo, a Texas-based green energy supplier, seems to have tackled. Back in 2023, Fervo partnered with Google to revive a geothermal plant in Nevada that had already drilled multiple conventional wells that hadn’t been able to heat enough water to meet its turbine capacity. Fervo drilled two wells 2.4 km (1.5 mi.) deep—but then continued each of them horizontally through granite for nearly 1 km (.57 mi.).

“The key thing that made our geothermal work was when you turn horizontally, you get access to way more hot rock per well that you drill than a vertical well,” says Fervo CEO Tim Latimer. “And so, we were able to flow across a much larger system of rock so we could get way higher flow rates. Importantly, they could sustain at the same temperature for a lot longer.”

The result was that just those two wells now produce enough hot water to generate over three megawatts of electricity. “And that was more than double what any other enhanced geothermal system technology had done,” says Latimer.

Scaling enhanced geothermal systems (EGS) for the grid

Less than two years after that first plant opened, Fervo is already in the process of drilling new wells for a plant in Utah that will eventually produce up to 400 MW, a roughly 13,000% increase in capacity over its 3 MW plant.

Part of the reason Fervo was able to scale up so quickly is that the company gathers a tremendous amount of data and uses it to continuously refine its drilling process.

“So the first time we drilled a horizontal well, it took us 75 days. It took us $13 million to drill that well. In the horizontal section, we drilled 3,000 ft, and we broke 13 bits in the span of drilling that 3,000 ft. A lot of innovation is not sexy. A lot of times, it's just breaking a lot of things. And then running a really rigorous program to figure out, why did it break? How do you make it better for next time, and how do you improve?”

“By the time we were drilling our 10th well, we drilled an entire lateral section through solid granite, 5,000 ft, and we only broke one bit instead of 13. And that meant that we were drilling wells in 17 days instead of 75 days. And so now, we're drilling wells at under $4 million when we used to drill them at $13 million.”

Those improvements in drilling efficiency mean Fervo can now drill deeper, where it’s hotter, and extend horizontally much farther through hard rock like granite, which increases the amount of heat its wells can transfer. Whereas its two wells in Nevada had 3,000 ft horizontal spans through 350 degrees Fahrenheit rock, the wells at its Utah site reach down to rock that's 450 degrees Fahrenheit and then extend horizontally for 5,000 feet.

Fervo has drilled 20 wells already and plans eventually to drill about 80. Because they are deeper and hotter, each well can now generate 10 megawatts instead of 3. The plant is on track to send 100 megawatts to the grid in 2026 and will add the remaining 300 megawatts by 2028.

“In October, the Biden administration announced that we'd gotten our final Federal permitting action to expand the site up to 2 gigawatts. We've only announced 400 megawatts publicly. The 2 gigawatts thing may give you a clue of how we're thinking about expanding that asset,” said Latimer.

Chris Wright, the newly appointed Secretary of Energy, has also expressed strong support for geothermal energy calling it a "tremendous potential energy source" during his confirmation hearing—a statement that signals growing federal confidence in geothermal technology.

How sensors and AI optimize geothermal energy

Back underground, Fervo continues to collect data on the wells it’s already drilled so it can continue to monitor and improve their performance. Each well has fiber optic cables running through it, which collect real-time data on water flow, temperature and other parameters. The company has also developed algorithms that determine how it can extract heat most efficiently from the wells.

This data-driven approach has been adopted by other geothermal plants as well. ENEL uses AI to monitor and run diagnostics on its geothermal plants in Tuscany.

That data promises to pay big dividends, both for the health of the planet and for investors’ pocketbooks. If Fervo, ENEL and others continue to refine their processes, the International Energy Agency estimates that geothermal could meet 150 times the current global electricity demand. Meanwhile, Fervo is eyeing a multi-billion dollar IPO within the next couple of years.

Listen to Fervo CEO Tim Latimer interviewed by David Roberts on the Volt podcast.