Stress Intensity Factor of Surface Cracks in the Tubing of High-Temperature and High-Pressure Deep Wells

Currently, research on tubing failure predominantly focuses on the fractures caused by tubing corrosion, with limited literature addressing the impact of temperature and pressure on tubing fractures. This study develops two analytical models for the surface crack stress intensity factor (SIF) in tubing, taking into account the pressure field and temperature–pressure coupling field. In addition, a finite element model (FEM) of the tubing containing surface cracks is established using the extended finite element method. The theoretical models and the FEM are used to calculate the SIF of cracks on the tubing surface, with a comparison made between the two models to verify their correctness. A parameter sensitivity analysis on the SIF is conducted using the verified FEM. The results indicate that as the crack curvature and crack depth increase, the SIF at the crack leading edge also increases, with the dominant mode of diagonal cracking being mode I cracking. Meanwhile, in the temperature–pressure coupled field, the SIF increases with an increase in both the pressure and temperature difference. The analysis reveals that pressure has a more substantial impact on the SIF compared to the temperature difference.