Process Modeling and Load Prediction for Pear-Shaped Expander Restoration of Deformed Casing in Horizontal Oil and Gas Wells

Casing deformation in horizontal wells reduces the effective drift diameter of the wellbore and may interrupt workover and hydraulic fracturing operations. Accurate prediction of reshaping load is therefore important for deformed-casing repair and wellbore integrity management. In this study, the mechanical response of C110-grade elliptically deformed casing restored by a pear-shaped expander was investigated without cement-sheath constraint. Two analytical reshaping-force models based on curved beam theory and thick-walled cylinder theory were established, and a three-dimensional finite element model was developed to simulate nonlinear tool–casing contact and elastoplastic deformation. Five expander outer diameters of 122–130 mm were analyzed, and a 1:8 similarity-scaled experiment was conducted for validation. The results show that the reshaping force increased from 50.2 t to 141.7 t as the expander outer diameter increased from 122 mm to 130 mm, whereas the improvement in minor-axis expansion was relatively limited. The finite element results agreed well with the experimental results, with average errors of 8.542% for reshaping force and 8.822% for minor-axis expansion. The thick-walled cylinder model showed better prediction accuracy than the curved beam model, with an average error of 4.11%. The proposed analytical–numerical–experimental framework provides a basis for reshaping-load estimation, expander selection, and stepwise restoration process design in deformed-casing repair.