Effects of fault configuration on casing elastic-plastic fracture failure under fault slip

Hydraulic fracturing in shale gas reservoirs with complex fault configurations can activate faults and induce fault slip, thereby imposing shear loading on casing and causing casing failure. Existing studies have mainly focused on casing mechanical behavior at the elastic deformation stage, whereas the full failure process from elastic-plastic deformation to fracture under different fault configurations remains insufficiently understood. To address this issue, a nonlocal peridynamic model incorporating the von Mises yield criterion and a bond-breaking criterion based on total elastic-plastic strain energy is developed to characterize the elastic-plastic deformation and damage evolution process of casing under fault slip. The model was validated against finite element results for a compressed-plate benchmark and further verified by comparison with published casing shear test results. The validated model is then used to systematically investigate the effects of fault slip distance, fault dip angle, fault type, fault spacing, and the angle between faults on casing response. The results show that fault configuration significantly affects the magnitude and distribution of casing stress, the localization of plastic strain, and the evolution of damage and fracture. Based on the simulation dataset, a machine-learning-based prediction and optimization model is further established for casing failure, and mitigation strategies are proposed and applied to an actual shale gas well. This study reveals the effects of fault configuration on casing elastic-plastic fracture failure and provides guidance for the prevention and mitigation of casing failure in shale gas reservoirs with complex fault configurations.