USA, Oregon: Altarock has Plans to Reach 500 Degrees Celsius at 4.5 K Depth at Newberry

Q&A: Susan Petty on expanding the reach of geothermal energy (Physics Today)

Susan Petty

Susan Petty (a GRC Member) wants to go hotter. If that means drilling near a volcano, she’s in. Drilling deeper than any geothermal well to date? Fine. Petty’s company, Seattle-based AltaRock Energy, is gearing up to do both those things at its site near the Newberry volcano, about 32 kilometers south of Bend, Oregon.

Physics Today (PT): What’s next for AltaRock?

PETTY: We think we have some new and exciting technology. High temperatures make enhanced geothermal systems (EGS) more efficient and economical. One superhot well can produce 25–50 megawatts. For comparison, the Haynesville shale gas wells in Louisiana produce 8–10 megawatts electric equivalent, a conventional geothermal well produces 5 megawatts, and a typical EGS produces 7 megawatts. And the generation costs would be 4.5 to 5 cents per kilowatt-hour, which is competitive with wind or solar or coal.

Right now you could probably supply 10 GW of electric power in the western US with superhot EGS by going to the sides of volcanoes and other places where shallow areas are hot.

PT: How deep do you need to go?

PETTY: We took over two wells on the side of the Newberry volcano. The deepest well is about 3 kilometers deep, with a temperature of 340 °C. We want to get to 500 °C, which should be at about 4.5 to 5 kilometers in depth. When we do that, we are hoping to create fractures and to produce very high temperature fluids. We are guessing that if we drill to 500 °C, we might be able to produce 450 °C at the surface. We would use surface equipment made with technologies borrowed from nuclear plants.

Deepening the well, doing the fracturing, and then doing a bunch of science that goes with it so you understand what you did will cost about $14 million. We are applying for grants from the government and foundations.

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