THE NEVADA PLAY FAIRWAY PROJECT: AN INTEGRATED APPROACH TO DISCOVERING NEW GEOTHERMAL SYSTEMS IN THE GREAT BASIN REGION (Invited Presentation)

The Great Basin region is capable of producing much greater amounts of geothermal energy than the current ~670 MW from ~25 power plants. Most geothermal resources in this region are blind, and thus the favorable characteristics for geothermal activity must be synthesized and methodologies developed to discover new commercial-grade systems (>130^oC). The geothermal play fairway concept involves integration of geologic, geophysical, and geochemical parameters indicative of geothermal activity as a means of identifying promising areas for new development. In the Nevada play fairway project, nine parameters were initially synthesized to produce a new geothermal potential map of 96,000 km² extending from west-central to eastern Nevada. These parameters were grouped into subsets and individually weighted to delineate rankings for heat and local, intermediate, and regional permeability, which collectively defined the play fairways.

From the regional map, 24 highly prospective areas, including known undeveloped systems and unknown potential blind systems, were identified for further analysis in areas where land status and distance to electrical transmission corridors facilitated potential development. Five particularly promising sites were then selected for detailed studies (Sou Hills and Granite Springs, Crescent, Steptoe, and southern Gabbs Valleys). Multiple techniques, including geologic mapping, Quaternary fault analysis, 2-m temperature surveys, gravity surveys, LiDAR, geochemical studies, seismic reflection analysis, and 3D modeling, were employed in these areas to define likely sites for high permeability and prospective drilling targets. The initial permeability models were revised to reflect results of detailed analyses and generate new detailed play fairway maps. Lessons learned include: 1) initially identified sites include multiple favorable settings at a finer scale; 2) geophysical surveys are required for delineation of sites in Cenozoic basins; and 3) play fairway analysis is critical at multiple scales, providing a means both to select regional prospects and vector into drilling targets at individual sites. Based on our detailed studies, several potential new, high temperature systems were discovered, particularly in southern Gabbs and northern Granite Springs Valleys.