A Couple fluid-geomechanics Numerical Simulation Study of Hydraulic Fracturing-Induced Fault Activation: A Case Study of Induced Seismicity in the Fox Creek Area, Canada

Since the commencement of hydraulic fracturing operations in the Fox Creek shale gas extraction area in the Western Canadian Basin, there has been a significant increase in seismic activity, which has attracted widespread attention from both the industry and the scientific community. The dynamic mechanisms responsible for the activation of faulting in some typical induced seismic cases in the area are not yet fully understood. In this study, we focus on the seismic sequence and structures that occurred in the Duvernay formation in the Fox Creek region in early 2014. We conduct a multi-field coupled numerical simulation study to investigate the activation of existing faults due to fluid perturbations. Firstly, the fault locations are identified based on seismic data, and the stress perturbation input from fluid injection is calculated using the PKN model. A two-dimensional geological model is then constructed by incorporating formation and structural information. Subsequently, a numerical simulation model is developed to simulate fault activation within a porous elastic medium, integrating solid mechanics, fluid flow laws, and fault valve theory. Finally, the entire process of hydraulic fracturing-induced fault activation is numerically simulated using the finite element method, and the activation locations and timing of faults are determined by calculating the change in Coulomb stress. The evolution of the coupled fluid-solid field and stress-strain field near the faults is analyzed. The results show that regardless of the presence of the eastern fault, the activation of the western fault valve occurs at the same time, and the activation trend is generally consistent, although there are differences in the ∆CFS (Coulomb failure stress) and pore pressure values between the upper and lower plates. Additionally, the regions with positive ∆CFS values generated by fault displacement coincide closely with the locations of induced earthquakes. The numerical simulation study in this paper reproduces the physical processes of hydraulic fracturing-induced fault activation, and if prospective forward analysis of related mechanisms is conducted, it will provide a scientific basis for earthquake hazard prediction.