EPFL: Ultra-Deep Fracking Can Enable Limitless Geothermal Energy

The potential for nearly limitless clean geothermal energy has significantly improved. Researchers at EPFL’s Laboratory of Experimental Rock Mechanics (LEMR) have demonstrated that the semi-plastic, viscous rock found at supercritical depths can still be fractured to allow water to flow through.

Together with nuclear power—through fission or fusion—and a few other advanced energy sources, geothermal energy could make concerns about general energy shortages as outdated as fears of saber-toothed tigers. By harnessing the immense heat from the Earth’s interior, we could theoretically generate enough clean energy to satisfy humanity’s needs for millions of years, effectively addressing the greatest challenge of climate change almost overnight.

The challenge is that this vast energy lies miles beneath the Earth’s surface, making access costly. As a result, geothermal power is currently a niche resource, limited to volcanic regions where heat is closer to the surface.

Supercritical Geothermal Energy

However, a more powerful supercritical geothermal resource exists almost everywhere if we can drill deep enough to reach extremely hot rocks. At over 400 °C (752 °F), water becomes “supercritical,” an efficient phase for energy extraction, potentially allowing geothermal plants to produce 10 times more power than conventional ones.

While drilling to such depths—sometimes beyond 12 km (7.5 miles)—is currently beyond engineering limits, promising projects aim to solve this. If successful, geothermal plants could be built almost anywhere, including repurposed coal-fired power plant sites.

There are still many challenges to address—one being that geothermal energy requires maximum contact between rock surfaces and the fluid they heat. A highly effective way to increase this contact is to fracture the rock, similar to oil and gas fracking. Fervo Energy has demonstrated how significantly this approach can boost a geothermal plant’s efficiency.

Can Deep Rock Fracture for Supercritical Geothermal Energy?

However, since no one has drilled that deep, it’s unclear if the rock at such depths can crack and allow water to pass through. Observations near the 10 km (6.2 mile) mark show rock behaving differently from surface-level rock—it becomes soft, plastic, and gooey, raising doubts about its ability to fracture at supercritical temperatures.

That understanding shifted when an EPFL team, led by Gabriel Meyer, conducted lab tests using a new gas-based triaxial apparatus, high-resolution synchrotron 3D imaging, and finite element modeling.

“As you approach the 10-kilometer (6.2-mile) depth, the rock stops fracturing and instead deforms uniformly, like soft caramel, making its behavior more complex,” Meyer explained. “The deformation happens within the crystalline structures of the grains. I wanted to investigate whether water could still circulate through rock that has shifted into this unusual ductile state.“

Meyer’s Team Simulates Earth’s Extreme Conditions to Study Rock Behavior

Meyer and his team replicated the pressure and conditions deep within the Earth’s crust to study the brittle-to-ductile transition (BDT). These lab tests are crucial, as it’s nearly impossible to observe this process in real-world settings. Using a test rig, they recreated the temperature and pressure of the rock sample, then scanned it with a synchrotron to produce 3D images, which were fed into computer simulations.

They discovered that the rock behaves more like Silly Putty than typical putty. Like Silly Putty, which can be molded and slowly flows like a liquid, it also shatters like glass when struck with force. Similarly, the rock above the supercritical zone, while ductile, can still be fractured to allow water to pass through. This suggests that with advanced deep fracking technology, it’s possible to develop highly efficient geothermal plants.

Water Can Flow Through Ductile Rock

“Geologists have long believed that the brittle-to-ductile transition marked the deepest point where water could circulate in the Earth’s crust,” says Meyer. “However, we’ve demonstrated that water can also flow through ductile rock. This is a very promising finding that paves the way for new research opportunities in our field.”

This discovery is especially relevant to companies like Quaise Energy, an East Coast startup aiming to prove that super-deep geothermal boreholes can be drilled using particle accelerator technology from the fusion energy sector, rather than traditional drill bits, which don’t hold up at such extreme depths and temperatures.

Companies like Fervo and Sage Geosystems are demonstrating that using a fracking-based approach to geothermal energy can generate far more power than traditional methods. This research shows that the same concept could be applied to ultra-deep supercritical geothermal projects.

If these companies succeed in scaling up this type of power plant, humanity’s energy challenges could essentially be solved. The result would be clean, grid-responsive, 24/7, and nearly limitless power. While many new challenges still need to be addressed, the potential is promising, and further progress is eagerly anticipated.

Read the original article on: New Atlas

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