Criterion Energy Partners is aiming to be a next-gen energy company. Photo via Getty Images

Sean Marshall and Danny Rehg founded Criterion Energy Partners in 2020 with the hope that geothermal energy could be the cleaner, safer wave of the future. Less than three years later, the team is close to making their plan a reality thanks to a geothermal well that they hope to drill this year.

Entrepreneurship wasn’t always part of the plan for either partner. When Marshall enrolled in the MBA program at Rice University’s Jones School of Business in 2016, he had a successful career at Credit Suisse and had his eye set on a future political career. But then he met classmate Rehg, whose background was in petroleum engineering. Their wives were both attorneys in the Houston district attorney’s office and the couples became fast friends. They also realized that, as Marshall now puts it, Rehg knew how to drill wells and he knew how to make deals.

In the ensuing years, both Rehg and Marshall's careers evolved and, eventually, the pair started looking for other opportunities. That’s when they read an article in Rolling Stone about geothermal energy.

“It was really a place where it really felt like this was something we were put here to do,” says Marshall.

Marshall and Rehg spent the ensuing months “like rats in a dumpster” learning about the players and opportunities in the geothermal industry and built from there. They learned about Pleasant Bayou Power Plant, a 1989 geothermal energy project based in Brazoria County that was backed by the U.S. Department of Energy.

Last summer, Criterion Energy Partners, a member of Greentown Houston, closed on a 10,000-acre lease around the site of Pleasant Bayou.

"We hope by the end of this year we will be generating electrons,” says Marshall.

Though the company has a patented technology that connects wells to the grid, called Criterion Geothermal System, Marshall says that some of the best advice he’s gotten was, “Don’t fall in love with your technology; fall in love with the problem.” The 2021 Texas freeze reminded the founders what that was.

“People were looking for cleaner, lower-emission power sources and [there was] a need for energy resiliency,” says Marshall, explaining that the freeze created an ideal situation for the company, as people began to think more outside the grid.

The year 2022 was a big one for Criterion Energy Partners. Oil and gas powerhouse Patterson-UTI invested in the company, followed by funding from the Department of Energy. The money not only allowed Criterion Energy Partners to lease their land, they are also now paying 12 salaries, including those of the founders. The team offices in The Cannon’s Esperson coworking space.

“Our mission is to make geothermal commercially viable everywhere,” says Marshall. “I still believe in that.”

However, Criterion Energy Partners may be even bigger than proving an alternative energy source. Marshall says that geothermal is the foundation on which they are building “a next-generation energy company.” Criterion Energy Partners could be the more stable basis for a whole new energy system.

Sean Marshall and Danny Rehg founded Criterion Energy Partners in 2020. Photos courtesy

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This article originally ran on InnovationMap.

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Houston company lands first deal from new Blackstone energy transition fund

M&A activity

Asset manager Blackstone has agreed to buy Houston-based Dresser Utility Solutions from Connecticut private equity firm First Reserve for an undisclosed amount. First Reserve has a major presence in Houston.

The deal represents the first investment from Blackstone Energy Transition Partners V.

“Blackstone’s deep resources and experience in the utility sector make them an ideal partner as we continue to invest in innovation, expand our product portfolio, and deliver value for our customers,” Dresser CEO David Evans said in a news release.

Founded in 1880, Dresser provides metering technology, digital instrumentation and software, pressure and flow controls, and infrastructure repair products for gas and water utilities and industrial customers. The company employs about 850 people worldwide.

“As demands on the energy grid continue to grow, Dresser plays a critical role as a trusted partner to utilities managing essential infrastructure. The company’s products are foundational to the safe and reliable operation of gas and water networks, and its reputation for quality has helped build longstanding customer relationships,” David Foley, global head of Blackstone Energy Transition Partners, and JP Munfa, senior managing director, said in the release.

Blackstone Energy Transition Partners has invested more than $28 billion across the energy transition sector. New York-based Blackstone closed Blackstone Energy Transition Partners Fund IV at $5.6 billion in February 2025. Blackstone Energy Transition Partners Fund III closed in 2020 for $4.4 million, according to Pitchbook.

Other notable energy transition investments from Blackstone funds include Salt Lake City-based Energy Exemplar, French electronics manufacturing company Sediver, Plano-based Westwood Professional Services and others.

Two years ago, Dresser secured a $335 million credit facility from funds managed by asset manager Blue Owl Capital. At the time, Dresser said the money would go toward capital expenses, acquisitions and corporate needs.

This is the second notable investment Blackstone has made in a Houston-based energy company in recent months. In May, Blackstone and energy heavyweight Halliburton made a $1 billion equity investment in Houston power generation startup VoltaGrid, which provides behind-the-meter mobile power generation equipment for data centers, microgrids and industrial customers.

Houston cleantech startup closes $17M round to tap into hot geothermal sector

fresh funding

Houston-area startup Hephae Energy Technology Corp. has closed a $17.8 million Series A financing round to commercialize its geothermal technology.

The round was co-led by Pennsylvania-based Susquehanna Sustainable Investments, which invests in early-stage climatech companies, and Copenhagen-based Underground Ventures, which focuses on geothermal energy startups. Alfa8, Baruch Future Ventures, Centaurus Capital LP, Elemental Impact, Exa Ventures, Future Ventures, Grantham Foundation for the Protection of the Environment, New System Ventures and True North Institute joined the round, along with existing Houston-based investor Nabors Industries. Hyphae reports in a news release that the Series A round brings the company's total capital raised to $24.7 million.

Hephae develops ultra-high-temperature downhole sensing, measurement, communications and control systems that can withstand the heat of geothermal sites, which are hotter and deeper than traditional oil and gas reservoirs. The company's Pandora210 system can operate at up to 400 degrees Fahrenheit.

Hephae reports that it plans to use the new funding to commercialize its Pandora210 tool and to launch research and development into systems that can withstand temperatures of up to 570 degrees Fahrenheit. Houston-based Fervo Energy, for instance, recently tapped its hottest geothermal well to date in western Utah, showing temperatures above 555 degrees Fahrenheit.

"Commercial deployment represents a major milestone in our mission to scalable, always-on, emission-free power globally, with a world-class team to tackle this problem," Steve Krase, CEO of Hephae Energy Technology, said in the release." This investment enables Hephae to transition from development to scale, delivering the ultra-high temperature drilling technologies needed to support the rapid growth of the geothermal industry in the US and international markets."

Hephae has been collaborating with Fervo Energy in the field. The company told the Houston Business JournalHouston Business Journal this spring that it expected its Pandora210 technology to be deployed at its Utah sites.

“Fervo is encouraged by the early progress of our collaboration with Hephae, whose novel high-temperature innovations have the potential to contribute positively to EGS economics, unlock higher-energy geothermal resources, and further cement the competitiveness of next-generation geothermal power," Elliot Howard, director of drilling and completions at Fervo, added in the release.

As the geothermal industry continues to scale, Hephae says it aims for its technology to help companies "unlock hotter, deeper resources that result in lower produced energy costs."

The Spring-based startup was founded in 2020 by CEO Steve Krase and CTO John Clegg. Krase previously launched Navigate Energy Services, which was acquired by Nabors in 2013. Clegg is also an industry veteran and has held numerous leadership positions at energy companies, including Weatherford, NOV, Schlumberger and others.