Slow-Slip Evolution of Injection-Induced Shearing on Granite Fracture Available to Purchase

Shear slip of fractures/faults induced by pressurized fluid injection has been recognized as an important mechanism in reservoir stimulation and induced earthquake. A lab-scale physical simulation of fluid injection-induced shearing is still lacking to understand the slip evolution under reservoir conditions. In this study, triaxial injection-induced shear tests were conducted on cylindrical granite samples that contain an inclined and embedded fracture. The aim is to close enough to simulate the natural fracture properties, in-situ stress, and temperature conditions. Results demonstrate three visible slip stages from static friction to unstable slip. Variable normal stress and its response to a sudden change in shear stress was observed from the acquired pulse data. Moreover, slowly stick-slip friction dominates the injection-induced shearing in the velocity of tens of micrometers per second. Friction stability analysis indicates that the aseismic and seismic creeps alternatively appear, which reveals the complexity of induced shear friction. Our results confirm that the fluid injection-induced shearing is a type of variable normal stress, stick-slip, and slow slip friction.