Repurposed Oil and Gas Wells Can Be Used to Store Sustainable Energy Underground

Solar and wind energy can be converted into high-pressure air for storage in abandoned wells.

Sustainable energy will be converted into high-pressure air and stored underground in idle well pipes that contain shallow wet sand. (Illustration courtesy of Iraj Ershaghi.)

Sustainable energy will be converted into high-pressure air and stored underground in idle well pipes that contain shallow wet sand. (Illustration courtesy of Iraj Ershaghi.)

A team of researchers from the University of Southern California (USC) is proposing an innovative and efficient solution to California’s growing number of abandoned oil and gas wells. These wells are typically sealed off with cement once they dry out. However, this often results in contaminated soil over time, which can subsequently cost states like California a considerable amount of money to resolve.

According to the research team, these wells can still be used as a subsurface storage space for wind and solar power. Not only will this avoid environmental degradation, but it can also address energy security issues in the country. California, in particular, is battling the prospect of rolling blackouts in the near future. Iraj Ershaghi, a USC Viterbi Professor who is the Omar B. Milligan Chair of Petroleum Engineering, shares how the country currently cannot provide sufficient battery storage for California’s energy demands.

“It is a shame to abandon these wells that were drilled at high cost when we could use them for something that the country needs: subsurface energy storage,” said Ershaghi. “This is going to be enormous in terms of environmental safety, in terms of energy sufficiency and in terms of storage. You can turn an eyesore and potential problem into an opportunity.”

The idea is to convert the energy generated by solar panels and wind turbines into high-pressure air through a compressor. This air will then be stored in the well pipes using subsurface saline aquifers or wet sand that will be deposited approximately 1,000 to 8,000 feet below the surface. Ershaghi explains that this high-pressure air can be stored underground and released to generate electricity using turbines and send power to the grid when needed. He adds that, if this method is expanded across the country, areas will have geological storage sites that can be readily accessed when blackouts occur.

“I think this would be good for the oil and gas well owners, who wouldn’t have to go through the large expense of total abandonment and could actually receive potential royalties for providing their wells for storage sites,” shared Ershaghi. “Utilities, which desperately need to meet deadlines for alternative energy solutions, and come up with viable storage solutions would also benefit, as would the entire economy. This is a win-win.”

This is a method that is frequently used by petroleum engineers and subsurface geoscientists to hide greenhouse gases in wells. One converted well can already store five megawatts of energy. A complete oil or gas field, on the other hand, could potentially hold thousands of megawatts. The U.S. Energy Information Administration is expecting that 300,000 wells may be idled in the coming decade.

To transform the wells into energy storage spaces, the pipes will be filled with cement to seal the oil and gas reservoirs. A hole will be added to the well for better access to shallower wet sand, in addition to a sensor on the well’s front end for detecting dangerous leaks.

The team has already begun planning to select their first demonstration site, which they expect to be ready by next summer. They are aiming to complete the project’s description paper by fall 2021. Alongside Ershaghi, the project will be facilitated by USC faculty members Don Paul, a research professor of engineering, William M. Keck, a professor of energy resources, and Birendra Jha, an assistant professor of petroleum engineering. Ershaghi added that the team will also be enlisting the help of USC Viterbi computer scientists, as well as civil, environmental and electrical engineers.

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