Mazama Raised $135M to Drill Into 629°F Rock

On September 17, Mazama Energy announced $135 million in new capital, including an oversubscribed Series B, to develop superhot rock geothermal at the Newberry volcano in Oregon. Centaurus Capital — John Arnold's firm — and Doerr Capital led. ConocoPhillips and Shell Ventures joined. Khosla Ventures and Gates Frontier returned.

Two oil majors funding a geothermal round is the detail to sit with. Their presence is not ESG positioning; it is the recognition that superhot rock geothermal is, mechanically, a drilling problem, and drilling is the thing they are best in the world at.

The record that makes this credible

Mazama's first well at Newberry holds the record for the hottest enhanced geothermal system ever drilled: 629°F (331°C).

Temperature is the entire economic argument in geothermal, and the relationship is not linear. Conventional geothermal plants run on resources in the 300–400°F range, where the thermodynamics cap conversion efficiency and each well produces a modest few megawatts. Push into superhot territory and the available energy per unit of fluid rises steeply. The same borehole, the same surface footprint and roughly the same drilling campaign yield far more power.

That is why the company's target for Project Ceres is 15 MWe per well. Conventional geothermal wells typically deliver a fraction of that. If Mazama hits it, the cost per megawatt collapses, because the expensive part of geothermal has always been the hole in the ground, not the turbine at the top.

Project Ceres is focused on horizontal well development in superhot rock, targeting power generation by 2027. Horizontal drilling is the technique that turned shale from a curiosity into the dominant source of American hydrocarbons — it multiplies the reservoir contact you get from a single expensive vertical descent. Applying it to superhot rock is the direct transfer of the shale playbook to heat.

Which is exactly why ConocoPhillips and Shell are in the round. The hard parts of this problem — drilling at extreme temperature, managing well integrity under thermal stress, steering a horizontal lateral thousands of feet down — are oilfield engineering problems. The reservoir is just rock that is much too hot.

What "enhanced" means, and why it matters

Conventional geothermal has a geography problem. It requires a natural reservoir: hot rock and water and permeability, all in the same place. That combination exists in Iceland, parts of Kenya, the Geysers in California and a short list of other locations. It is why geothermal has remained a rounding error in global generation despite being the only firm, weather-independent renewable.

Enhanced geothermal removes the water and permeability requirements. You drill into hot dry rock, engineer the fracture network yourself, circulate your own working fluid, and harvest the heat. If that works reliably, the constraint reduces to a single variable: is the rock hot enough, close enough to the surface, to be worth drilling to?

That variable is satisfied across an enormous fraction of the planet. Mazama is designing Project Ceres explicitly as a near-term proof point for a larger claim — an independent certification of at least 10 GWe of resource potential at the Newberry site alone. The company also plans to evaluate additional sites in the U.S. and internationally.

Ten gigawatts from one volcanic complex would be roughly the output of ten large nuclear reactors, from a resource that requires no fuel cycle, no fuel deliveries and no combustion.

The demand side has changed

Five years ago a geothermal round of this size would have been a climate bet with a long fuse. In 2026 it is an infrastructure bet with an impatient customer.

U.S. data center electricity demand has gone from roughly 23 GW in 2023 to about 42 GW now. Grid interconnection queues stretch years. Wholesale power prices near hyperscale facilities have surged. Hyperscalers have responded by signing direct nuclear power purchase agreements and, where nuclear is not available fast enough, by building gas.

Geothermal fits that demand profile better than anything else on the clean side. It is firm — it runs at high capacity factor around the clock, unlike solar and wind, which is the specific property a training cluster needs. It has a small land footprint relative to output. And it has no fuel supply chain, which matters to buyers signing twenty-year agreements.

The obstacle has always been that it only worked in a handful of places. Superhot enhanced geothermal is the attempt to delete that sentence.

What has to go right

The record well proves the temperature exists and is reachable. It does not yet prove three things: that horizontal laterals hold up under sustained thermal cycling, that the engineered fracture network circulates fluid at commercial rates without short-circuiting, and that the per-well economics land where the model says at production scale rather than in a demonstration.

Project Ceres, by 2027, is the test of all three at once. $135 million and two oil majors is the market saying the physics has been demonstrated and the engineering is now the only question left.