Abstract: During overflow shutdown in high-pressure gas wells, the rapid pressure changes within the wellbore cause an imbalance in casing stress distribution, significantly reducing its internal pressure resistance and increasing the risk of failure. To address the insufficient accuracy of existing methods in calculating the internal pressure resistance of shut-in casings, this paper proposes a toughness burst model for open-ended casings. The model was used to calculate the internal pressure resistance of a BG110SS grade casing with dimensions of 244.5 mm×13.8 mm. Concurrently, a finite element model of a casing-cement ring system incorporating cement ring constraints was established using 3D software to simulate the mechanical response of the casing under shut-in internal pressure loads. Comparison between the finite element simulation results and the calculations from the toughness burst model demonstrates that the proposed model achieves high computational accuracy and more realistically reflects the casing's internal pressure resistance. This provides a new scientific reference basis for determining the internal pressure resistance of casings under overflow shutdown conditions in high-pressure gas wells.

Key words: casing strength, internal pressure resistance, burst model, yield strength, finite element analysis