Production enhancement in shale oil horizontal wells is commonly achieved by volumetric fracturing, yet induced fault slip and associated casing deformation remain prominent issues. A three-dimensional geomechanics-wellbore indirect-coupling finite-element method was adopted, by which a fault-bearing reservoir and a casing-cement sheath-formation system were constructed. The effects of fluid-pressure increment within the fault, the angle between fault strike and the maximum horizontal principal stress, and fault dip on slip behavior and casing response were evaluated. Tool passability was determined by the curvature radius and the minimum inner diameter of the deformed casing. The results show that significant slip is triggered when the fluid-pressure increment on the fault plane exceeds approximately 30 MPa, larger strike-stress angles lead to stronger slip, and increasing dip simultaneously amplifies both strike-slip and normal-slip components. The induced slip subjects the casing to strongly non-uniform external loads, resulting in S-shaped bending and an elliptical reduction of the cross-sectional area, on the basis of which threshold outer-diameter limits for tool sticking were provided. These findings provide a quantitative basis for fault-risk identification, parameter optimization, and casing-deformation control in multi-stage fracturing.