Stochastic exploration and the geologic context of enhanced geothermal system viability on the Snake River Plain, Idaho
Alex Moody, Jerry Fairley, Mitchell Plummer, 2016. "Stochastic exploration and the geologic context of enhanced geothermal system viability on the Snake River Plain, Idaho", Geothermal Energy: An Important Resource, Gordon R. Osinski, David A. Kring
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Geothermal energy depends on high subsurface temperature, adequate permeability and fracture volume, and accessible groundwater supply to support heat exchange with surrounding rock. Some regions may have adequate thermal resources but lack the necessary permeability or deep circulating water. Exploitation of such areas for geothermal energy could occur if permeability can be enhanced enough to provide the necessary heat exchange. These improvements to the geothermal reservoir would produce what is termed an “enhanced geothermal system” (EGS). The Snake River Plain (SRP) in southern Idaho is a geological region with high heat flux (~110 mW/m2) that has been recommended as an EGS target. In this study, we consider how the geologic and thermal history of the SRP might influence its EGS potential. We describe the fracture distribution (mean = 28.63 fractures/10 m) in a welded tuff core recovered from one of the few deep boreholes located on the SRP and provide a preliminary discussion of the likely geomechanical behavior under in situ stress. Spatial autocorrelation of fracture features is defined with geostatistical techniques and used in a stochastic simulation of possible structures in other welded tuff reservoirs. Autocorrelation scales for the continuous date are on the order of 70 meters with high subsample scale variability (56 m). Results should aid in designing criteria for a hydraulic fracturing plan that would augment the permeability and connectivity of an SRP reservoir's preexisting fracture network.