New fiber-optic monitoring tools could help industry unlock geothermal energy
University of Wisconsin–Madison geoscientists and engineers are working with industry partners and the U.S. Department of Energy to develop a highly detailed monitoring system for geothermal wells.
Man-made geothermal systems that emulate natural ones could, by some conservative estimates, produce a total of 100 gigawatts of cost-competitive electricity over the next 50 years. But to get there, energy providers need more sophisticated systems for gathering and analyzing data about the rock mechanics and hydrology at work.
The research team — including geological engineering and geoscience Professor Kurt Feigl, geological engineering Associate Professor Dante Fratta, geoscience Assistant Professor Mike Cardiff, geoscience Professor Cliff Thurber, and geoscience Professor Herb Wang — has converged on Brady Hot Springs in Nevada to turn a relatively small geothermal field into a proving ground for a system that could be scaled for wider and deeper fields.
The project is the first in North America to use fiber-optic cables to measure rock properties in a geothermal field, though it’s common for energy companies to use the technology in oil exploration. “Locating oil underground is tough, but in geothermal wells, the challenge is finding hot water,” Feigl says.
“We have a real opportunity to create better, more efficient reservoirs … that could lead to the deployment of EGS on a broader scale.”
In the last five years, advances in fiber-optic technology have enabled cables to gather around a terabyte of detailed seismic and temperature data per day. “We have one channel every meter, whereas a typical seismic survey would have one channel every 30 or 40 meters,” says Joe Greer, a business development manager at Silixa, one of the industry partners involved in the project.
The project’s scope spans from fundamental geoscience to maximizing the production of electricity from geothermal wells. Feigl says there’s still a great deal to be learned about fractures and deformation in rocks, and the information will in turn help the DOE, Silixa and Ormat Technologies follow the hot water through a complex underground landscape — and pursue the long-term goal of commercializing enhanced geothermal systems (EGS).
EGS are man-made geothermal wells created by injecting additional fluid into naturally heated rock areas that are not already saturated with fluid. This process opens up existing fractures in the rock, allowing the water to circulate through the area and transport the geothermal heat so that it can be converted into electricity.
“We have a real opportunity to create better, more efficient reservoirs, and that could lead to the deployment of EGS on a broader scale,” says Lauren Boyd, the EGS program manager for DOE. “We have to understand what our fracture network looks like before we try to create a reservoir.”
Boyd says the DOE chose to fund the project in part because of the UW–Madison team’s unique combination of strengths in geoscience and data analysis.
“It was very clear that Kurt and his team have a really clear understanding of these challenges that we’re facing, and it brings a creative approach to integrating technologies,” Boyd says.