Role of Fluid and Temperature in Fracture Mechanics and Coupled THMC Processes for Enhanced Geothermal Systems

We propose to develop an integrated experimental, theoretical, and computational approach to enhance heat recovery in geothermal systems by characterizing and monitoring the impact of fluid and temperature on fracture slip mechanisms and associated changes in permeability and mechanical properties. Our specific objectives are to 1) advance mechanistic understanding of the frictional/deformational behavior of faults and natural fractures in enhanced geothermal systems (EGS), 2) identify the coupled effects of mechanical, hydraulic, thermal and chemical processes on the spatio-temporal evolution of permeability and stress fields in faults and fracture networks and assess potential seismicity, and 3) address key controllable parameters that have the most significant impact on optimal heat extraction by advancing a EGS simulator capability (FALCON). Theoretical studies will provide a link between laboratory tests and full scale simulations and formulate constitutive relations relating macroscopic behavior and microscale constituents. Specific topics include the stability of frictional sliding, using a rate and state description, due to fluid injection, the role of chemical reactions on frictional sliding and thermo- and chemo- poroelastic effects on fracture propagation.