Optimized Design of Casing Centralizers for Complex Well Structures

ABSTRACT: The safe deployment of casing strings in high-curvature wellbore sections is critical to the success of subsequent drilling operations and the long-term productivity of oil and gas wells. However, comprehensive studies addressing both the passability of casing strings and the structural integrity of threaded connections remain limited. This study, grounded in the theory of axial and transverse bending beams, the principle of equivalent bending moment, and the law of energy conservation, develops a mechanical deflection model that accounts for initial curvature. The model integrates key influencing factors, including wellbore trajectory, bending moments at centralizers, lateral wall forces, buoyant weight, and geometric parameters of the casing string. Based on actual field conditions, an analytical method is proposed to determine the critical wellbore curvature and evaluate the thread strength safety margin, enabling safety assessments of casing deployment under various operational scenarios. A three-dimensional computational model for API casing thread connections is also established, incorporating geometric passability and thread strength criteria. The influence of wellbore curvature on casing deflection and thread stress distribution is investigated, along with a sensitivity analysis of borehole enlargement ratio, casing outer diameter, and centralizer dimensions. Case study validation confirms the reliability of the proposed mechanical model and safety evaluation method. The findings provide theoretical support for the pre-assessment of casing deployment safety in horizontal wells.