<p>In the development of ultra-deep oil and gas resources, wellbore shrinkage and casing damage often occur, posing significant risks to safe drilling operations. Reported analyses on casing integrity have primarily focused on non-uniform external loads without considering geometric non-uniformity of the wellbore. In this work, a creep constitutive model and a casing collapse-strength model are established to model the shrinkage behavior of salt formations. A coupled formation–cement–casing mechanical model that accounts for wellbore non-uniformity is developed. Uniaxial tensile tests are performed to characterize the plastic deformation behavior of casing materials. The results indicate that, for a representative well in the Bozi block of the Tarim Basin, increasing drilling-fluid density gradually reduces both wellbore eccentricity and shrinkage. The optimal density range for safe operation is 2.30–2.35&#xa0;g/cm³. Geometric irregularities in the wellbore amplify non-uniform external loads, leading to an 11.3% increase in casing stress compared to uniform conditions. When both geostress and geometric non-uniformities are considered, the safety factor against external compression decreases by 20.88%, and the residual collapse-strength coefficient decreases by 9%. Increasing casing wall thickness enhances the residual collapse-strength coefficient by 6.83% and the collapse-safety factor by 2.8%.</p>