Enhanced Geothermal Systems: A Promising Source of Round-the-Clock Energy

The U.S. has a great advantage to expand EGS, because the technology can be based on the experience of the country’s extensive unconventional oil and gas production that can be transferred to geothermal engineering. In a recently published Nature Reviews Clean Technology paper, my colleagues and I discuss how adopting oilfield drilling strategies has made EGS drilling easier and less expensive.

Geothermal power plants also bring hot liquids rich in critical minerals to Earth’s surface, offering access to elements such as lithium, a key ingredient in most batteries.

Q. Advancements are being made in EGS. What distinguishes these systems from conventional geothermal systems?
Conventional geothermal energy production relies on hot fluid that naturally flows underground through rocks; however, there is a substantial amount of heat in subsurface rock, essentially everywhere, but not all rock is permeable enough to allow fluid to flow through. By injecting water through wells, EGS either improves access to natural fluid or creates new underground heat exchangers by fracturing rock, which increases or enables fluid flow. At the surface, the heat is turned into electricity.

Q. Are there challenges or limitations to developing EGS? How can scientists address them?
Stimulating geothermal reservoirs, fracturing subsurface rocks to allow fluid flow, and injecting fluids underground cause movements or vibrations in the subsurface, most of which go undetected by humans. We study this “induced seismicity” in the field and lab by monitoring and simulating how underground movement changes in response to stimulation.

We have also adapted Berkeley Lab technologies for very hot temperatures (over 750 degrees Fahrenheit) and to access the deep subsurface (3 miles underground) through our own work at The Geysers Geothermal Field in California. Next we want to be able to closely study these harsh temperatures, pressures, and chemical conditions within the laboratory.

Q. How are you advancing EGS efforts within Berkeley Labs’s Energy Geosciences Division?
Through lab experiments, simulations, and field testing, we study the temperature, mechanics, hydraulics, and chemistry of geothermal reservoirs to understand what geologic conditions, such as depth or rock type, are most favorable to EGS reservoirs as we look to create them artificially.

At Berkeley Lab’s Geosciences Measurement Facility (GMF), we develop new technologies in-house, including fiber-optic sensing tools, GPS receivers, and more, which can help us accelerate EGS development and expansion.

We test different methods of creating, sustaining, and monitoring EGS through a collaboration focused on demonstrating the potential of EGS at a United States Department of Energy (DOE)-funded underground field-scale laboratory called Utah FORGE, and through EGS demonstration projects also supported by the DOE. One of these demonstration projects explores EGS in superhot conditions with temperatures above 700 degrees Fahrenheit, which can provide significantly more energy compared to geothermal reservoirs with lower temperatures.

For geotechnology development, there is often a wide gap between small-scale lab experiments and the real-world reservoir scale. That’s why we use an intermediate scale: the underground laboratory to achieve realistic conditions. Berkeley Lab previously led a multi-national lab project called EGS Collab, to study and simulate rock fracturing in reservoir-type rock that allowed us to more closely understand and manipulate EGS development, monitoring, and stimulation methods.

Q. What makes Berkeley Lab especially capable of studying EGS?
Berkeley Lab has more than 40 years of experience in geothermal and EGS research. This expertise made it possible to develop a simulation platform that describes many thermal, hydraulic, mechanical and chemical reservoir processes. The suite of simulators, called TOUGH, is now widely used at universities, government organizations, and private industries, and can give clues on the locations of geothermal resources. This can help inform the logistics for reservoir engineering and operation, and monitor reservoir performance over decades of operation.

Berkeley Lab’s DOE-supported Cyclotron Road has supported today’s key players in geothermal and EGS development such as Fervo Energy and Zanskar. This has allowed Berkeley Lab to create a long-term, collaborative relationship to industry involved in emerging technologies.

Berkeley Lab is also home to many scientists that offer a unique range of expert perspectives on the many interdisciplinary fields involved in EGS, such as geologists, geochemists, geophysicists, seismic monitoring experts, and more. The commitment to team science makes this national laboratory a great place to study something as advanced as EGS which requires many great minds, perspectives, and capabilities.

Julie Bobyock is a communication specialist on Berkeley Lab’s Earth and Environmental. Christina Procopiou is Communications and content manager at Berkeley Lab. The article was originally posted to the website of Berkeley Lab.