Play Fairway Analysis is a systematic approach to exploration that integrates data at the regional or basin scale in order to define exploration targets (plays), and then interrogates these data to highlight plays that have the highest likelihood of success. Play Fairway Analysis provides greater technical rigor than traditional geothermal exploration approaches, and facilitates quantification of play risks even when data are sparse or incomplete. It is a mature practice in petroleum, but represents a new approach for geothermal that we believe will aid in the discovery of buried or blind systems. A key challenge will be adapting fairway analysis to geothermal exploration in a way that provides both meaningful results and measurable return on investment. In this project, we focus on the Snake River Plain where, during Project HOTSPOT, our team discovered a blind hydrothermal system at Mountain Home Air Force Base in Idaho. From that discovery we are able to define key parameters that characterize the elements necessary for a geothermal reservoir based on basaltic (plume-related) magmatism, fracturing that defines a reservoir volume, seals that are provided by lake beds, hyaloclastics, and highly altered clay-rich basalts, and fluid recharge that is controlled by faulting and the primary permeability of basalt flows. Basaltic terrains are not generally considered to be viable exploration targets for high-temperature geothermal systems since basalt is channeled rapidly from depth to the surface through fractures, forming dikes that cool rapidly. However, important geothermal systems in basaltic terrains include the Puna geothermal district in Hawaii, the Reyjanes peninsula in Iceland, and the hydrothermal systems related to mid-ocean ridges. Although the Snake River Plain is part of the highest heat flow anomaly in the US, it has seen relatively little geothermal exploration. We believe that this results from the lack of obvious high temperature manifestations and the basaltic nature of the province. Project Hotspot identified three different play types in the SRP (a) high thermal gradients along the volcanic axis beneath the SRP aquifer, (b) extremely large low temperature systems, and (c) blind high-temperature systems like that discovered at Mountain Home. Phase 1 of this project will assess the distribution and viability of these plays throughout the SRP region; Phase 2 will focus on detailed analyses of specific plays as we move from a Regional/Basin focus to a Play/Prospect focus. Our approach is to analyze direct and indirect methodologies for identifying critical reservoir parameters: heat source, reservoir permeability, seal and recharge. Critical Element Charts will be used to compile the age and distribution of critical fairway elements, and Composite Common Risk Segment (CCRS) maps compiled to integrate and assess all of the data elements.

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