New trends in geophysical applications to geothermal exploration and development

Abstract Enhanced geothermal systems (EGS) are developed by drilling injection and production wells in hot reservoirs. These wells are subsequently interconnected by propped hydraulic fractures. A working fluid, such as water, is circulated through this closed system. To commercialize EGS, the U.S. Department of Energy provided funding for a full-scale field laboratory in south-central Utah. The charter of the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) is to demonstrate relevant technology to derisk EGS development. Early in the drilling campaign, reflection seismic surveys detected the top of granite but did not discriminate properties within the granite reservoir. Comprehensive petrophysical logging was done in multiple wells, including image logs that indicated heterogeneous granitoid properties. Multiple production logs (spinner, temperature, and pressure) as well as fiber-optic measurements and borehole geophones and surface arrays characterized the stimulated reservoir. In this paper, we summarize the key findings for resource development and exploitation.