套管腐蚀缺陷的规则化处理及抗挤强度分析

摘要

随着复杂结构井在石油钻采中的广泛应用,由腐蚀缺陷引起的套管挤毁失效问题日益突出,导致修井周期增大,开采成本增加,成为制约钻采效益的主要因素之一.针对上述问题,将GB/T19624-2004含缺陷压力容器评定标准运用到含腐蚀缺陷套管的抗挤强度分析中,将不同形貌的套管腐蚀缺陷规则化处理.通过理论与仿真对比验证,建立了精确的含腐蚀缺陷套管有限元模型.利用ANSYS研究了不同腐蚀缺陷套管的抗挤毁强度.研究结果表明:在椭球型腐蚀缺陷长轴长度、短轴长度、缺陷深度和穿透型缺陷长度、宽度5个结构参数中,椭球型缺陷深度、短轴长度和穿透型缺陷的宽度是套管强度的最敏感参数.因此套管的抗挤强度分析应着重考虑腐蚀缺陷的影响.针对设计和使用的每种套管,都应考虑可预见的腐蚀缺陷进行精细化数值计算,以确保其安全工作.%As the complex structure well is widely used in oil drilling, the problem of casing collapse failure caused by corrosion defects is increasingly prominent, which resulted in increasing of the workover period and mining costs.To be one of the main factors the drilling efficiency was restricted.According to the above problem,assessment was applied for in-service pressure vessels containing defects GB/T19624-2004 to the analysis of casing collapsing strength with corrosion defects, transfer different corrosion defects into regular shape. Through theory and simulation verification,A numerical model is developed using ANSYS finite element method (FEM) to analyze casing collapsing strength with varieties of corrosion defects. The result shows that, in the five structural parameters which is the length of major axial and minor axial, the defects′ depth, the length and width of throughwall defects, the depth of ellipsoidal corrosion defects, the length of minor axial and the width of through-wall defects are the most sensitive parameters of the casing strength. So the effect of corrosion defects should be considered in casing collapsing strength analysis. For the design and use of each casing, the foreseeable corrosion defects should be considered in refinement numerical calculation, to ensure its security.