Distributed fiber sensing systems could help industry unlock geothermal energy
University of Wisconsin partners with Silixa, Ormat Technologies, and DOE to measure geothermal properties via optical fiber.
Geoscientists and engineers at the University of Wisconsin-Madison are working with industry partners and the U.S. Department of Energy (DOE) to develop a highly detailed monitoring system for geothermal wells based on the use of fiber-optic cables to measure rock properties in a geothermal field.
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 (Hertfordshire, England), one of the industry partners involved in the project. Silixa makes distributed fiber sensing systems for use in energy, security, and other industries.
Manmade geothermal systems that emulate natural ones could, by some conservative estimates, produce up to 100 gigawatts of cost-competitive electrical power 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 University of Wisconsin professors Kurt Feigl, Dante Fratta, Mike Cardiff, Cliff Thurber, and Herb Wang -- has set up at 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'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 geothermal developer Ormat Technologies (Reno, NV) follow the hot water through a complex underground landscape and pursue the long-term goal of commercializing enhanced geothermal systems (EGS).
Manmade geothermal power
Enhanced geothermal systems are manmade 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."