Numerical Modelling on the Effect of In-Situ Stress Contrast on the Slip Characteristics of a Reactivated Fault during Hydraulic Fracturing

In-situ stress state markedly affects the slip characteristics of faults reactivated after the interaction with hydraulically stimulated fracture. This study investigates the slip characteristics along a fault crossing pay zone and bounding zones, which are under contrasting major principal stresses using numerical simulations with universal distinct element code (UDEC). The results of the simulations showed higher slip displacements along the fault for higher stress contrasts between pay zone and bounding zones at lower approaching angles. The slip displacement increased with increasing approaching angle and showed progressively less dependence on the considered stress contrasts. The aperture of the reactivated fault is greatly reduced by the stress contrast at higher approaching angles. The aperture is greatest at lower approaching angles and trivially affected by the stress contrast. The simulations with different major-to-minor principal stress ratios showed a significant decrease in both slip displacement, and aperture at higher stress ratios, which is more pronounced at higher stress contrasts between the pay zone and bounding zone. Overall, this study revealed some important insights into the slip behavior of reactivated faults due to hydraulic fracturing under contrasting in-situ stress conditions, which can have implications on induced seismicity and groundwater contaminations issues related to hydraulic fracturing.