Short-term failure mechanism triggered by hydraulic fracturing

Abstract

Hydraulic fracturing may induce or trigger an earthquake while injecting fluid into strata to initiate a new fracture so as to promote oil and gas production. Previous studies have confirmed that the injection of fluids into the formation, especially hydraulic fracturing, is closely related to seismic activity. However, the mechanism through which fluid injection changes the stress field of rock mass and interacts with the in situ stress state is still poorly understood. This study focused on the short-term mechanism coupling shear stress and hydraulic fracturing in an experimental simulation. Preexisting tension fractures were initiated and propagated by loading shear force. The fracture propagation path of hydraulic fracturing was closely related to the preexisting fractures formed by the preshear stress. Short-term hydraulic fracturing promoted fracture propagation and acoustic emission events (or microearthquake signals), but it was less likely to cause rock mass instability or a large earthquake. The long-term fluid injection could saturate preexisting fractures and infiltrate rock mass to increase the pore pressure and change the in situ stress field in a large area to induce an earthquake.