--> --> Methodologies and strategies for harnessing the vast geothermal potential of Nevada and the Great Basin region: A summary of recent studies and advances

AAPG Pacific Section and Rocky Mountain Section Joint Meeting

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Methodologies and strategies for harnessing the vast geothermal potential of Nevada and the Great Basin region: A summary of recent studies and advances

Abstract

As a result of its transtensional to extensional tectonic setting, Nevada and the surrounding Great Basin region are richly endowed in geothermal resources. Estimates suggest that the Great Basin region is capable of producing much greater amounts of geothermal energy than the current ~600 MW from ~24 power plants. Similar to most hydrocarbon deposits, studies also suggest that most of the geothermal resources in the region are blind (i.e. lack surface hot springs and steam vents). In this region of pervasive high heat flow, sufficient permeability is more challenging to find than suitable temperatures for conventional resources. Thus, it is imperative that the favorable conditions for geothermal activity be synthesized and exploration methodologies developed to discover new robust systems. For areas lacking sufficient permeability (the bulk of the region), development of unconventional resources in hot, relatively impermeable rocks in enhanced geothermal systems (EGS) is critical. We have therefore been proceeding on multiple fronts to 1) better characterize the favorable settings for conventional geothermal activity, 2) improve methodologies for evaluating geothermal potential of conventional systems, and 3) develop methods for assessing EGS development. Because most geothermal systems are fault controlled in this active tectonic region, our efforts at better characterizing conventional systems have focused on evaluating the favorable structural settings for geothermal activity. Nearly 90% of the systems reside in step-overs in normal faults, normal fault terminations, fault intersections, and accommodation zones. High fault and fracture density in these settings facilitate high permeability and fluid flow. These findings were recently incorporated into a regional geothermal play fairway analysis, whereby nine geologic, geochemical, and geophysical parameters were synthesized to produce a new detailed geothermal potential map of 96,000 square kilometers from west-central to eastern Nevada. These parameters were grouped into subsets to delineate rankings for local permeability, regional permeability, and heat, which collectively defined geothermal play fairways (i.e. most likely locations for significant geothermal fluid flow). At least 25 highly prospective areas, including both known undeveloped systems and previously undiscovered potential blind systems, have been identified for further analysis. In addition, work is proceeding to assess the suitability of promising sites for the DOE sponsored Frontier Observatory for Research in Geothermal Energy (FORGE), which will offer a unique opportunity to develop the technologies, techniques, and knowledge needed to make EGS a commercially viable electricity generation option.