Phase 2 Update for the Fallon FORGE Site, Nevada, USA

Abstract

The Department of Energy (DOE) Frontier Observatory for Research in Geothermal Energy (FORGE) is to be a dedicated field laboratory where the scientific and engineering community can develop, test, and improve sub-surface technologies and techniques for the creation of cost-effective and sustainable enhanced geothermal systems (EGS) in a controlled environment. The establishment of FORGE will facilitate an understanding of the key mechanisms controlling a successful EGS. The Fallon FORGE site in Nevada is one of two sites that are still being evaluated as potential candidates for hosting the final FORGE laboratory. In Phase 1 of the FORGE initiative, the Fallon team reviewed extensive, pre-existing data including lithological, well log and flow test results from deep wells within the Fallon FORGE footprint that penetrate the target reservoir, as well as a suite of geophysical, geochemical, geological and hydrological data on and adjacent to the site. Such evaluation confirmed that the Fallon site is ideally positioned to host a sub-surface EGS laboratory, with low permeability, appropriate temperatures and depths (175-225°C, 1-4 km), no hydrothermal system, appropriate lithologies, and a favorable stress regime. In Phase 2, key activities included: o securing additional environmental permits and initiating an EA; extensive outreach with key local, regional and state stakeholders; preparing our induced seismicity mitigation plan (ISMP); acquisition of seismic and geodetic baseline datasets (MEQ, GPS and InSAR); reprocessing and reinterpretation of preexisting seismic reflection profiles; acquisition of new, detailed gravity and magnetic data; refining our detailed 3D model of the site (originally constructed in Phase 1) based on the new geophysical data and reinterpreted seismic reflection profiles; geomechanical and reservoir modelling, and, siting and drilling a deep well to provide additional certainty that the target reservoir has low permeability. This paper provides an overview of these Phase 2 activities at the Fallon FORGE site, and how these activities have further improved our knowledge of site characteristics.