Mazama Energy's $135M Series B and the 15-Day Well at Newberry

In the high desert of central Oregon, a steel wellhead stands above a hole that runs nearly two miles into Newberry Volcano. At the bottom, the rock holds at 629°F — hotter than any engineered geothermal system on record. On September 1, Mazama Energy's crew finished drilling a second well into that heat and stopped the clock at 15 days.

The same target depth took far longer in 2025. This time it came in 80% fewer days.

That gap is the product.

Three days after the drilling result, the money arrived. ConocoPhillips and Shell Ventures joined the round. So did Khosla Ventures and Gates Frontier, both already on the cap table.

Three years, one volcano, two wells

TIMELINE: Superhot rock at Newberry
─────────────────────────────────────────────────────────────
  2023 ───── 2025 ───── 2026 ───── 2026 ───── 2027
  🧪    ──── 🔥    ──── 🏭    ──── 💰    ──── ⚡
  Founded   World's    Athena    $135M     Project
  at Khosla hottest    well:     Series B  Ceres:
  Ventures  EGS 629°F  15 days             15 MW
─────────────────────────────────────────────────────────────
Source: Mazama Energy, GlobeNewswire, September 2026

Mazama was founded in 2023 and incubated at Khosla Ventures. Its lease sits on the western flank of Newberry, where superhot rock — above 374°C — lies less than five kilometers down. That shallow heat is why the company picked the volcano over a dozen other candidates.

In 2025 it drilled 10,200 feet and built a reservoir where none existed. The rock at the bottom measured 629°F. That was the hottest engineered geothermal system ever completed.

The Athena well is a manufacturing story

Athena reached the 2025 well's target depth in 15 days. The number that matters is the 80% reduction, not the depth itself. It means the second well was not a science experiment. It was a repeat.

Speed like that comes from repetition. The Athena program was built to prove faster, more efficient drilling while validating the technology stack for superhot rock, not to chase a single record. It is also testing supercritical carbon dioxide as a drilling fluid at the site. None of that is exotic. It compounds.

The well is now drilling toward roughly 15,500 feet, where temperatures should exceed 750°F. At that heat, water turns supercritical and carries far more energy per unit of flow. The company says a 750°F well can deliver up to ten times the power of a conventional 390°F well.

The reservoir is the other half of the bet

Speed alone does not make a power plant. The heat has to flow from rock to turbine for decades, and that depends on the reservoir the company leaves behind. Mazama calls its approach Thermal Lattice — a sequence of controlled stimulations that links injector and producer wells through hot crystalline rock.

The 2025 pilot proved the concept at 629°F, with stable circulation and confirmed connectivity. Project Ceres now has to prove it at commercial rates. Two horizontal wells, each running more than half a mile sideways through rock near 710°F, will be connected underground and tested for power output.

Who is paying to drill into 400°C rock

Mazama is not alone at Newberry. Quaise Energy is drilling its own well nearby, using millimeter waves from a surface gyrotron to vaporize rock instead of grinding it. The two approaches could not be more different.

Company disclosures and specialist press, September 2026

The breakthrough in superhot geothermal is turning extreme heat into a repeatable, economic power system.— Sriram Vasantharajan, CEO, Mazama Energy

The wider sector is moving with it. Fervo Energy raised $1.89 billion in a May IPO. Sage Geosystems started producing power from its first Texas pilot and closed a $97 million Series B. Quaise finished its Series B at $180 million in August. Utilities and hyperscalers are hunting for round-the-clock carbon-free power, and geothermal is one of the few sources that can promise it.

From $4,500 to $3,200 a kilowatt

The company expects its first commercial project to cost $4,500 to $4,950 per kilowatt to develop. The stated pathway runs to $3,200 per kilowatt as drilling and reservoir work repeat. That is the number that decides whether superhot rock competes with natural gas.

The company also claims its method uses 75% less water and 80% fewer wells than conventional geothermal. Fewer wells mean less capital and a smaller surface footprint, the two things that have kept geothermal a niche resource.

It is targeting independent certification of more than 10 gigawatts of resource potential at Newberry alone. The site, it says, could host at least 5 gigawatts — roughly a quarter of average Pacific Northwest electricity demand.

What would have to go right

The risks are real. Drilling into rock above 400°C stresses steel and cement in ways oil and gas equipment was never built for. Induced seismicity and water use draw scrutiny even at a remote site. And a single commercial well pair has yet to run for years, which is the only test that matters for a utility contract.

Investors are betting that those are engineering problems with engineering answers. ConocoPhillips and Shell Ventures know the drilling side better than almost anyone. Their presence in the round is a signal about the cost curve, not the science.

The heat was never the hard part

Geothermal has always been a geography problem. You could only build where the heat sat shallow enough to reach with conventional drills. Superhot rock breaks that constraint, but only if drilling gets cheap and repeatable.

As we wrote in September, the same underground thinking is already producing a second revenue stream at a Cornwall site, where geothermal brine yields battery-grade lithium. The heat is the first product. It will not be the last.

The 15-day well is a data point, not a verdict. It says the learning curve is real. It does not yet say the curve is steep enough to reach $3,200 a kilowatt.