Hydro‐Mechanical Measurements of Sheared Crystalline Rock Fractures With Applications for EGS Collab Experiments 1 and 2

We present hydro-mechanical measurements that characterize shear on natural fractures in schist, amphibolite, and rhyolite specimens from the enhanced geothermal system (EGS) Collab Project's Experiment 1 2 sites (E1 E2) at Sanford Underground Research Facility. employed a triaxial direct method augmented with X-ray imaging to perform hydroshearing (injection-induced shearing) mechanical shearing naturally fractured situ stress conditions. Measurements included fracture permeability, strength, stress-dependent aperture, dilation, frictional strength. Results reveal must be permeable, weak, shear-oriented hydrosheared, only subset of observable were suitable. When sheared, permeability typically increased by factor 10 or more this increase was retained over time. However, slip did not always result increase. High phyllosilicate content associated exceptionally weak exhibited poor even decreased after stimulation. These combination site data used conduct slip-tendency analysis for different sets, we selected top candidate EGS sites. also found lower stronger E2 make challenging than E1 site. Overall, methods our work can applied any project identify joint sets are best suited hydroshearing, which turn help optimize well placement energy production.