Geothermal Energy

Geothermal Energy provides one means to help expand the mix of energy sources that are used to meet an increasing overall energy demand worldwide. Geothermal energy is currently harnessed from select special locations where surface thermal manifestations indicate the presence of both heat and water near the surface that can be accessed for use in energy production and space heating. With the renewed emphasis on increasing the utilization of geothermal energy, the need for improved means for identification of likely locations where heat and water can be economically accessed has increased. Exploration for, and development of, geothermal energy can be done using techniques similar to those used for petroleum exploration. However, those methods are often too expensive and are not the best ones that can be used in geological environments where geothermal energy is most likely to be found and they are not the best for the identification of thermal resources. Methods that are commonly employed include electromagnetics, remote sensing, gravity and seismics. The Earth Resources Laboratory has efforts on several fronts to develop better methods for the identification of geothermal energy resources. Our work tends to focus on the acquisition of data from potential geothermal fields and the analysis of the data using novel methods. Our work focuses on candidate sites in the Western United States, the Caribbean, and Iceland. In the Caribbean, we collect electromagnetic, gravity and seismic data to infer the presence of hot water and the flow of hot water at depth. We have deployed a seismic network on the Reykjanes Penninsula in Iceland, a region that contains several producing hydrothermal geothermal reservoirs, to collect data to be used for better characterization of existing geothermal energy reservoirs using our new seismic data and using combined seismic and electromagnetic data.

Enhanced Geothermal Energy or EGS encompasses a range of methods that can be used to develop or improve geothermal systems in regions that conventional approaches for extracting geothermal energy are not feasible. Such systems usually involve the stimulation of a region of hot rock to improve the permeability of the region. After stimulation, fluids (usually water) can be injected into the reservoir through one or more wells and recovered in adjacent wells. The fluids heat up as they flow through the reservoir and are recovered from the production well at a higher temperature than that at which they were injected. Economical development of EGS requires that the fracture system that is developed by the stimulation be characterized. Geophysical characterization of the fracture system can be done using seismic and electromagnetic data. Seismic data mainly consists of waveforms of the microearthquakes that accompany the stimulation of the reservoir. The locations and waveforms of the microearthquakes can be interpreted to infer properties of the fracture system that is created by the stimulation.