Geomechanics in geothermal reservoirs

Enhanced geothermal systems have the potential to play a major role in deep decarbonization of the power sector. Geothermal's unique ability to provide clean power with flexible load profiles would support the high penetration levels of variable wind and solar power needed to reach a 100% clean electricity grid. The innovations that have driven the shale revolution present an exciting opportunity for technology transfer between the oil and gas and geothermal industries - this technology has the scale-up potential that could finally unlock the 100 GW domestic resource for enhanced geothermal systems. In this talk, I will review the fundamental reservoir and geomechanical processes that underpin the thesis that unconventional oil and gas technology has strong application in geothermal systems. I will present geophysical observations and reservoir simulation analyses of three case studies: 1) Hydraulic stimulation at the Fenton Hill EGS project, 2) fluid-driven seismicity at the Long Valley Caldera (a natural hydrothermal system), and 3) diagnostic fracture injection tests (DFITs) at the Utah FORGE EGS site. Each of these case studies show evidence for mixed-mechanism stimulation, a process that involves a strong interaction between newly formed tensile fractures and natural fractures. Because mixed-mechanism stimulation can control reservoir permeability changes in geothermal settings, new opportunities exist to optimize reservoir engineering and completion enginering designs for enhanced geothermal systems.

Speaker: Jack Norbeck, Fervo Energy