The U.S, has roughly 3 million abandoned oil and gas wells. One plan is to convert them into conduits for much-needed storage space for solar and wind generated power. Cement poured down the pipes would seal the oil and gas reservoirs with a sensor detecting any harmful leaks, and perforations would allow access to shallower-depth saline aquifers. Power created by solar panels and windmills placed near the wells would be converted into high-pressure air by a compressor, and it would travel through pipes to subsurface saline aquifers, or shallow wet sands, between 1,000 and 8,000 feet beneath the surface. This air would remain safely underground until needed and, using turbines, could be released to make electricity and send the power to the grid. A demonstration site should be identified by next summer and a description paper out by fall 2021.
www.smartgreenpost.com/2021/01/18/transforming-oil-wells-into-batteries-for-the-sun-and-wind/
phys.org/news/2014-12-abandoned-oil-gas-wells-emit.html