非均匀载荷作用下套管挤压失效数值分析

在已有的理论研究与试验工作的基础上，采用有限元数值方法，分析计算了受非均匀地应力作用下套管－水泥环结构的受力与变形，讨论了两个敏感参数─—非均匀载荷比和套管椭圆度对套管失效的影响问题。计算分析发现，随地应力非均匀程度的增加，套管形变经历了由两向挤压－挤压到两向拉伸－挤压组合方式的转变，而套管应力的变化相对较小。由此可得出初步结论：与非均匀地应力作用相对应的套管结构的拉伸－挤压形变，有可能是导致套管失效的主要机制；套管椭圆度的存在使得套管的强度和刚度被进一步的削弱。

A numerical analysis of casing collapse under nonuniform load

Based on theoretical study and test, by using finite element numerical method, the force and deformation of casing with cement sheath under nonuniform load is analyzed, and the effect of two sensentive parameters, the nonuniform load ratio and ellipticity, on the failure of casing is discussed. Calculation and analysis show that, with aggravation of load nonuniform, casing deformation varies from crush-crush style to tension-crush style with little change of casing stress. Thereby it is declared that casing failure is resulted from tension-crush deformation under nonuniform load, and the strength and stiffness of the casing are further decreased owing to the effect of ellipticity.