Overview of Utah Forge Results in 2019

Abstract

The Utah FORGE site is unpopulated and covers an area of about 1.9 square miles. It is situated within Utah’s Renewable Energy Corridor adjacent to a 306 MWe wind farm, a 240 MWe solar field and PacifiCorp Energy’s 38 MWe Blundell geothermal plant at Roosevelt Hot Springs. Site characterization activities conducted in 2016-2017 during Phase 2A and B demonstrated that the location is ideally suited for the development of an EGS reservoir. In Phase 2C (2018-2019), moderate rate injection tests were undertaken in well 58-32 to evaluate fracture initiation and growth, to detect related microseismicity, and to assesses the ability of establishing fracture connectivity. Three zones were selected for injection to confirm the insitu stress and natural fracture characteristics. Prior to stimulation testing, two vertical wells were drilled and instrumented with seismometers and a DAS cable, including 68-32 (1000 ft depth) and 78-32 (3280 ft depth). The 2019 tests confirm stress gradients determined in 2017, and in concert with fracture orientations, show the achievability of EGS reservoir development. The work also demonstrated that fractures behind casing can be accessed and stimulated and that multiple fracture sets with different closure pressures were stimulated. Other achievements include development of numerical reservoir models which incorporate a discrete fracture network. Multi-level geophone strings straddling the alluvium-granitoid contact provided the most sensitive microseismic monitoring. Phase 2C results also showed that the aquifer beneath the FORGE site can provide the quantities of water required for circulation operations in Phase 3. Focused geological study showed no evidence of faults in the alluvium or disrupting the alluvium-granitoid contact beneath the FORGE site.