Analysis on the influence of corrosion on casing strength in acidic gas field development

During the service of casing in acidic gas field, the acidic environment and other corrosion condition can cause casing corrosion. The thinning of casing wall and the appearing corrosion cavity in the internal wall of casing can both reduce the effective strength of casing. Thereby they can affect the collapsing strength and internal pressure strength of casing. It is maily discussed in the paper that the affection on casing strength from stress concentration caused by corrosion cavity. The corrosion cavity of casing is re-garded as sphere-like cavity. The mathematical model is established that can calculate the stress concentration factor caused by corrosion cavity, based on the knowledge of plasto-elasticity. The mathematical model is also established, which can calculate the residual intensity of casing after corrosion. The parameters of corrosion cavity affecting the strength of casing are analyzed. It is also analyzed that the relationship between the residual intensity of casing and the depth and diameter of corrosion cavity.