Research on the mechanism of fault sliding casing damage under the effect of water immersion deterioration of rock mass

Hydraulic fracturing-induced casing deformation has garnered significant attention, yet the effects of water immersion-induced rock deterioration remain underexplored. This study employs finite element analysis to investigate casing shear deformation in fault-sliding scenarios under water immersion deterioration. A 3D casing cement sheath-formation system model with varying water immersion parameters was developed to analyze casing mechanical properties and deformation. Results indicate that an 80% reduction in cohesion increases casing Mises stress by approximately fourfold, significantly impacting casing forces. A 60% reduction in the internal friction angle raises Mises stress by about 20%, exerting a weaker influence compared to cohesion changes. Decreasing the fault sliding surface friction coefficient elevates both Mises stress and inner diameter deformation; a reduction from 0.7 to 0.1 more than doubles Mises stress and increases resistance length eightfold. This study offers insights for designing casing damage models considering rock water immersion, optimizing fracturing parameters, and determining bridge plug dimensions.