Implications of geology, structure and tectonic setting for heat extraction on the Eastern Snake River Plain

摘要

Typically, high-temperature geothermal systems are found in regions of high geothermal gradients and strain rates that are host to an adequate and accessible groundwater supply to be used as a medium for heat exchange with the surrounding rock matrix. In some regions such as older collapsed calderas, there are reservoirs with extensive amounts of heat resources that lack either the permeability and hydraulic connectivity or the deep circulating waters necessary for traditional geothermal power production. The Snake River Plain is one such area with high geothermal gradients that was unfavorable in the past due to limitations in in-situ groundwater and proper circulation. As more attention is focused on the region with the advancement of Engineered Geothermal Systems (EGS), the high heat flow beneath the extensive Snake River Plain Aquifer can be reassessed in terms of potential thermal energy available. While enhancement of the reservoir is likely to increase the efficiency of the geothermal system, preliminary calculations of extractable heat energy based on the remote state of stress and structural context will inform where the optimal geothermal reservoirs are. Heat extraction of the Snake River Plain must consider the large-volume rhyolitic volcanism and caldera formation that defines the structure, lithologies and therefore the permeability of a given site. Given these criteria, we use a semi-analytical heat transfer models in the context of in-place geologic structures and suggest a tentative fracturing plan for augmenting the permeability and connectivity of the reservoir, thereby increasing the efficiency of heat exchange by induced fluid flow.