酸性气田开发中腐蚀对套管强度的影响

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

在酸性气田的套管服役过程中,酸性等腐蚀条件会引起套管的腐蚀,套管腐蚀都会降低套管的有效强度,从而影响套管的抗挤强度和抗内压强度。研究了腐蚀孔引起的应力集中对套管强度的影响。将套管的腐蚀孔看成是类圆形腐蚀孔,以弹塑性力学的知识建立了计算套管腐蚀孔引起的应力集中系数的数学模型,在此基础上建立了套管腐蚀后的剩余强度的计算模型。利用该文推导出的计算套管腐蚀后的剩余强度的计算公式,对影响套管强度的腐蚀孔参数进行了分析,分析了套管剩余强度随着腐蚀孔开口直径和腐蚀孔开口深度这2个参数变化而变化的关系。

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 ofplasto-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.