Disused oil wells could enhance compressed air storage

Developed by researchers at Penn State University, the geothermal-assisted compressed air energy storage (GA-CAES) system harnesses the existing infrastructure of abandoned oil and gas wells (AOGWs). Compressed air is pumped into the wells, where geothermal heat raises its temperature and compresses it further. Published in the Journal of Energy Storage, the study showed how geothermal energy could increase round-trip efficiency by 9.5 per cent.

“This improvement in efficiency can be a game changer to justify the economics of compressed-air energy storage projects,” said corresponding author Arash Dahi Taleghani, Professor of Petroleum and Natural Gas Engineering at Penn State.

“And on top of that, we could significantly avoid the upfront cost by using existing oil and gas wells that are no longer in production. This could be a win, win situation.”

Using numerical modelling simulations, the researchers found that placing CAES systems in abandoned oil and gas wells could raise the air temperature by 160°C. This led to an increase in pressure of 0.5MPa, which significantly boosted overall efficiency.

“Without taking advantage of the geothermal setup, you could not get enough encouraging numbers,” said Prof Taleghani. 

“And on top of that, drilling new wells may not justify the economics of this type of storage. But by combining these two factors, and by going back and forth through modelling and simulation, we found this could be a very good solution.”

The US Environmental Protection Agency estimates there are around 3.9 million AOGWs across the United States. If these wells are improperly plugged or damaged, they can leak methane into the atmosphere and groundwater. The Penn State team believes repurposing AOGWs could help mitigate the potential environmental impacts of abandoned wells, while also providing new job opportunities in areas where fossil fuel production has declined.

“If we use existing wells, we are basically hitting two birds with one stone,” said Prof Taleghani.

“First, we are sealing these wells. That stops any potential leaks. And then if we are repurposing these wells for energy storage, we are still using the infrastructure that is in place in these communities. It can potentially maintain employment in the area and allow communities to be part of the energy future.”