South SFV Today

Access to geothermal energy has traditionally depended on location, as conventional geothermal power plants require specific geological conditions. These include hot, permeable rocks and abundant underground fluid, limiting their use to areas with recent volcanic activity such as Japan, New Zealand, and the western United States.

However, over the last five decades, techniques initially developed for oilfields have been adapted for "enhanced geothermal systems" (EGS), expanding the potential for tapping into Earth's natural heat reserves across a wider range of locations. "There is a lot of excitement about enhanced geothermal energy," stated Roland Horne, a professor at Stanford Doerr School of Sustainability. He recently hosted the 50th Stanford Geothermal Workshop with over 450 participants from 28 countries to discuss advancements in this field.

Despite its historical use dating back to ancient Rome and early 20th-century Italy, geothermal energy today contributes significantly only in certain regions like Kenya but remains underutilized globally. EGS offers the possibility of increasing geothermal's share in global energy supply by utilizing advanced drilling techniques adapted from shale gas extraction.

Horne explained that methods such as horizontal drilling and hydraulic fracturing have been modified for EGS. These methods involve pumping fluids at high pressure into wells deep underground to open fractures in rock formations. In EGS applications, this fluid is hot water from natural reservoirs.

The implementation of synthetic diamond drill bits has further enhanced efficiency by reducing well completion times significantly. "Drilling faster makes an enormous difference to the whole economics of EGS," noted Horne.

Modeling led by PhD student Mohammad Aljubran suggests that improved drilling rates could make EGS competitive with average electricity prices across much of the United States by 2027. In California alone, where current geothermal capacity accounts for about 5% of electricity production, EGS could potentially increase capacity tenfold by 2045.

Nevertheless, concerns remain regarding seismic risks associated with fracturing deep rocks for accessing geothermal reservoirs. Mitigation strategies include avoiding seismically active areas and employing traffic-light protocols to monitor seismicity during operations.

A newer strategy involves creating numerous smaller fractures instead of large ones during drilling to reduce seismic risk. This approach aims to prevent activation of existing faults which can lead to earthquakes when filled with fluid.

Horne emphasized the potential impact: "EGS could be a game changer for green energy production not just in California but across the U.S. and worldwide." He hopes ongoing research will further develop EGS as a sustainable energy source capable of meeting future demands.