Houston-based geothermal startup Quaise Energy has closed its Series B fundraising round at $180 million after inking a significant investment from another local energy leader.

Quaise, which is developing a 50-megawatt superhot geothermal plant in Oregon, announced a "first close" of the round last month at $134 million, led by San Francisco-based investment firm Prelude Ventures. The $46 million bump has been fueled by a $35 million investment from Houston-based Nabors Industries.

The funding will go toward the continued development of the company's superhot geothermal plant, Project Obsidian, as well as the commercialization of Quaise's millimeter-wave drilling system, according to a news release.

“We are unlocking the most powerful clean energy source on Earth, and the Series B signals deep conviction across a wide range of investors,” Carlos Araque, Quaise CEO and president, said in the release. “Nabors is an invaluable partner as we move millimeter wave drilling to full commercial operations at Project Obsidian and beyond.”

Nabors, a repeat investor in Quaise, has also entered into a strategic framework agreement with Quaise. Under the agreement, Quaise will have access to a dedicated Nabors land rig and drilling platform. Nabors will also provide expertise in reservoir modeling, well design and drilling strategy.

Last year, Quaise drilled to a depth of about 330 feet using its millimeter-wave technology at its field site in Central Texas. Canary Media previously reported that Quaise plans to drill to nearly 3,300 feet later this year and to deploy its millimeter-wave technology at its power plant in 2027. The plant is expected to deliver power to the Pacific Northwest in 2030.

Quaise and Nabors say the partnership will improve drilling performance, reduce costs and accelerate project timelines.

“Superhot geothermal has the potential to make clean energy ubiquitous. That is why we are excited about our close relationship with Quaise,” Anthony Petrello, president and CEO of Nabors, added in the release. “Quaise’s millimeter wave technology changes the equation entirely by reaching superhot rock at temperatures and depths that are inaccessible with conventional drilling, transforming geothermal from a location-dependent resource into a global energy solution. Combined with Nabors’ drilling expertise and infrastructure, we see a path to gigawatt-scale geothermal power that no other company can offer today.”

Quaise reports that with the latest funding, it has now raised $280 million. It raised $21 million in a Series A1 financing round in 2024 and a $52 million Series A in 2022.

The company announced in March that it was aiming to raise $200 million for Project Obsidian through $100 million in Series B funding, plus an additional $100 million from grants, debt and project-level finance.