Field-scale fault reactivation experiments by fluid injection highlight aseismic leakage in caprock analogs: Implications for CO2 sequestration

Observations on tens-of-meter scale experiments of fault activation by fluid injection conducted in shales allow exploring how aseismic and seismic events may jeopardize the integrity a sealing caprock overlying CO2 sequestration reservoir. We contrast behavior shale faults with another set carbonates. Significant leakage occurs along initially low-permeability when rupture is activated. Most pathway closes ceases pressure drops. Dilatant slip plane alone does not explain observed behavior, which also caused opening favored softness shale, structure zone that prevents fluids from diffusing into adjacent damage zone. Experiments show large amount deformation. Small-magnitude seismicity (Mw < -2.5) outside pressurized patch. Stress transferred this deformation patch can build up to stress-criticality favor seismicity. Thus, terms caprocks, leading increased permeability loss seal great concern.