Numerical Simulation of Induced Seismicity in Carbon Capture and Storage Projects

Carbon capture and storage (CCS) technology offers a promising solution to control and reduce CO₂ emissions. Changes in pore fluid pressure within the injection zone can induce low-magnitude seismic events. The induced seismicity associated with CCS needs to be properly addressed in order to obtain public acceptance for the technology and also to prevent possible CO₂ leakage from the storage site due to fractures or fault-slip in the faults which can be reactivated due to injection. Simulation of CO₂ injection inherently poses a multi-physics problem coupling thermal, hydrologic, and geomechanical processes. In this paper, a set of 2D coupled thermo-hydro-mechanical modeling was performed to simulate stress changes and resulting geomechanical deformations in the reservoir, caprock and fault due to CO₂ injection. The model included a limited-dimension pre-existing fault which cannot be easily detected by surveys. The fault slip obtained from the numerical model was then used along with seismological theories to estimate the maximum magnitude of induced earthquake. A parametric study was performed to investigate the effects of reservoir properties as well as thermal stresses on geomechanical deformation, fault slip, pore pressure generation versus time, rupture time, and magnitude of induced events. The effects of permeability, porosity, and thickness of the reservoir were discussed. It was shown that thinner reservoirs have higher probability of fault reactivation and will result in larger induced seismic events. Reservoirs with higher porosity were shown to have longer rupture time and induce larger events. A higher permeable reservoir can decrease the potential of fault reactivation by generating lower buildup pore pressure and smaller fault slip. In general, for the given model geometry and injection characteristics, the heat flux never reached the fault by the time that the fault slip occurred and had no apparent effect on the results.