Millions of inactive wells are littered across the United States, the relics of earlier eras of fossil fuel production. A large number of the sites have no official owner, and many are still polluting groundwater and leaking heat-trapping methane. The country has barely scratched the surface in dealing with this problem.

Policymakers in both Republican- and Democratic-led states are exploring whether these sites could instead be converted into new wells for producing geothermal energy. The holes are already drilled in the ground, after all. And regions with widespread oil and gas development have rich subsurface data that geothermal firms need in order to determine where and how to build their carbon-free systems.

The concept is relatively new and largely untested, though scientists and startups are working to change that. States are also laying the groundwork for action by lifting regulatory hurdles and launching in-depth studies.

In Oklahoma, the state Senate is considering a bill that would create a process for companies to buy abandoned oil and gas wells and repurpose them for geothermal energy or underground energy storage. Oklahoma has identified over 20,000 such wells, and state regulators estimate that it would take 235 years and hundreds of millions of dollars to plug all of them. Fixing a single old well can cost anywhere from $75,000 to $150,000 or more, by some calculations, depending on where it’s located and how complicated it is to clean up.

The Well Repurposing Act, which passed Oklahoma’s House in March, is modeled after a similar law that New Mexico adopted last year to address its 2,000-plus orphan wells.

The Oklahoma bill ​“recognizes that these wells are a liability, and that there may be a way to turn them into some sort of revenue generation and give them value,” said Dave Tragethon, communications director for the nonprofit Well Done Foundation, which works to find and cap abandoned oil and gas wells nationwide. ​“And if there’s value, that means there’s more of a willingness to address them and more of an opportunity to raise funding.”

In Alabama, legislators passed a law last month that allows the state to approve and regulate the conversion of oil and gas wells to tap alternative energy resources like geothermal. And in Colorado, state agencies just launched a technical study to evaluate the potential of repurposing old wells for geothermal development and carbon capture and sequestration.

These efforts reflect the growing bipartisan support for geothermal energy, which has largely remained unscathed by the Trump administration’s efforts to block renewable energy projects. The energy resource has the potential to help meet the nation’s soaring energy demand while also slashing planet-warming emissions from electricity and heating.

Converting wells is enticing but complicated

Geothermal systems work by circulating fluids underground to capture naturally occurring heat, which can then be used to drive turbines for generating electricity or to directly warm the air and water in buildings. The industry is gaining momentum thanks to recent advances in drilling methods and technologies that are making it technically possible or financially viable to access geothermal energy in more places.

Many of those breakthroughs have come from the oil and gas industry, whose skilled workforce of drilling engineers and geoscientists, and deep corporate pockets, have helped launch startups and deploy cutting-edge systems. However, most of that expertise and funding are being poured into building new projects — not figuring out how to retool leaky wells left behind by earlier generations.

“Oil and gas well conversion presents an enormous opportunity, … but it’s pretty far away technologically from being a reality,” said Emily Pope, a geologist and senior fellow at the Center for Climate and Energy Solutions who authored a recent study on next-generation geothermal power.

“There are some hurdles that are still pretty immense,” she said, adding that ​“it is worth doing some R&D to try and grow.”

One of the biggest challenges is the fact that oil and gas wells tend to reach relatively low to medium underground temperatures. But high heat is key for geothermal projects, especially ones that generate electricity. The hotter the resource, the more energy a developer can wring out of the system.

Plus, fossil fuel wells generally produce smaller volumes of liquid and gas than geothermal wells need in order to spin power turbines or transfer heat to buildings. Geothermal operators might also have to take extra steps to keep nasty elements in the subsurface reservoirs from mixing with the working fluids used to extract heat underground, said Arash Dahi Taleghani, an engineering professor with the Repurposing Center for Energy Transition at Pennsylvania State University.

He added that the high cost of converting wells to geothermal has limited the number of real-world examples so far.

Early research efforts target direct-use heat and storage

At the University of Oklahoma, however, researchers have been evaluating how to turn four old oil and gas wells into sources of geothermal heat, which they hope to pipe into nearby public schools and homes in the city of Tuttle. The project was awarded a $1.7 million grant from the U.S. Department of Energy’s Wells of Opportunity program in 2022, though it was paused last year during the Trump administration’s sweeping freeze on federal funding and is still waiting to start its next phase, KGOU reported in March.

Saeed Salehi was the Oklahoma project’s director before joining Southern Methodist University as an engineering professor in 2024. He said that repurposing wells for geothermal has several ​“clear advantages.”

Geothermal firms can avoid significant upfront drilling costs if the wells are already sufficiently deep and hot enough. Oil and gas firms, which today pay millions of dollars to properly seal and shut down modern wells, can give their assets a second life instead. And communities near the aging fossil fuel infrastructure could benefit from having clean, affordable heat and lower winter utility bills.

“We need to collect enough data and have enough successful projects … to take it to scale,” Salehi said, calling repurposed wells ​“a custom solution for specific regions and areas.” 

“Everything is going to take time, but I think we are moving in the right direction,” he added.

A smoother permitting process will be key to speeding things up, something Oklahoma, Alabama, and other states are aiming to address. States have traditionally lacked any regulatory framework for dealing with decades-old wells that no one is technically responsible for. Salehi said it took nearly nine months to get the Tuttle project’s permits, though the process is growing faster now.

In Pennsylvania, Dahi Taleghani said his team is looking to secure funding to repurpose old wells to supply the Penn State campus with geothermal heating. They have also studied the potential for using some of the state’s more than 200,000 abandoned wells to heat agricultural greenhouses, as well as to house energy-storage systems that compress air and stash it underground, acting as low-cost grid batteries.

“Decommissioning wells is expensive, costly, and it’s not generating any revenue,” Dahi Taleghani said. ​“So we’re looking to [help] create businesses that can go after these leaky wells, fix them, and then use them for geothermal applications.”