Ultimate Axial Load Capacity of Production Tubular Strings in Offshore Extended-Reach Wells

As oil and gas exploration advances, tubular strings in extended-reach wells are becoming increasingly susceptible to buckling, self-locking, and other failure modes due to their relatively low weight and limited structural stiffness. Existing studies have mainly focused on running feasibility and associated mechanical responses, whereas systematic investigations of the ultimate axial load capacity of deployed tubular strings remain limited. To address this research gap, the present study investigates the ultimate axial load capacity of tubular strings in deepwater extended-reach wells, explicitly accounting for the constitutive behavior of the tubular material. Numerical simulations were performed under both tensile and compressive loading conditions for different well trajectories, dogleg severities, material grades, and wellbore diameters, and the effects of these factors on the ultimate axial load capacity were systematically evaluated. The numerical predictions at the initial yielding stage were compared with available analytical solutions, and good agreement was obtained, indicating that the proposed model is reliable for initial yield analysis. The results show that well trajectory, dogleg severity, material grade, and wellbore diameter significantly influence the ultimate axial load capacity of tubular strings. The findings of this study provide useful guidance for structural integrity assessment, design optimization, and operating-parameter selection for downhole tubular strings in deepwater and ultra-deepwater oil and gas developments, thereby supporting the safe and efficient completion of extended-reach wells.