Researchers at the University of Illinois at Urbana-Champaign have successfully repurposed abandoned oil and gas wells while demonstrating efficient geothermal heat storage.
Led by Tugce Baser, a professor of civil and environmental engineering, the new research is the first field study of a geothermal energy storage system within the Illinois Basin, a geological structure located deep underground.
The findings are published in the journal Renewable Energy.
Baser said the Illinois Basin is a cold basin, meaning it does not naturally generate geothermal energy to generate electricity. However, deeper underground formations have the necessary thermal and hydraulic properties to establish artificial geothermal reservoirs.
“Many of the same properties that make underground rock formations ideal for oil and gas extraction are also ideal for geothermal storage,” said Baser. “And our test site used to be a gas well, so most of the necessary infrastructure is already in place.”
According to Baser, the basin contains spongy rock units with open pore spaces and minerals with optimal thermal conductivity sandwiched between layers of insulation that are suitable for generating electricity. Provides the necessary space and insulation to establish an artificial heat reservoir that can hold enough hot liquids.
Using data from previous field observations and preliminary numerical modeling studies, the team chose to inject the preheated fluid into cypress sandstone, a porous rock unit located approximately 900 meters below the surface of the test site. Did.
To test the site’s heat storage capacity, researchers injected the well with water heated to 50 degrees Celsius for three days in April 2021. After closing the well, the team monitored changes in pressure, thermal conditions and hydraulic power for five days. days.
“Our field results, combined with further numerical modeling, found that the process can sustain a heat storage efficiency of 82%,” said Baser.
The study further reported an average total net cost of electricity generation of $0.138 per kilowatt-hour, making the proposed system economically viable and profitable.
“Our findings show that the Illinois Basin can become an effective means of storing excess thermal energy from industrial sources and ultimately more sustainable sources such as wind and solar. “Underground reservoirs essentially act as large underground batteries while reusing abandoned oil and gas wells. It’s a win-win situation.”
Original: Geothermal ‘batteries’ repurpose abandoned oil and gas wells in Illinois, researchers report
Than: University of Illinois at Urbana-Champaign
