水泥环对油气井套管力学性能影响的分析计算

油田生产中岩层在油井开采中应力变化较大,生产层段的岩层产生的应力作用于套管,挤压套管造成套管损坏,影响了油井的正常生产。通过建立二维平面轴对称和平面应变模型,利用Ansys有限元软件分析套管在水泥环影响下的变形特征。分析表明,油井开采中地应力作用于水泥环,套管最大应力在套管内壁产生,均匀载荷下套管抗挤强度是非均匀载荷的7倍以上。载荷椭圆度越大,套管内壁应力越大且分布不均。增大水泥环弹性模量可以有效减小套管最大应力,生产中应保持水泥环弹性模量在20-35GPa范围,可以提高套管的抗挤强度。均匀载荷下,应采用J55套管,非均匀载荷下,应采用P110套管,可以有效地减小套管产生的应力,提高套管的抗挤强度。

Analysis of Effect of Cement Sheath on Casing Mechanical Property in Oil/Gas Well

The article established the model of two dimension plane axis symmetry and plane strain, and utilized Ansys finite element software to analyze the deformation feature of casing under the effect of cement sheath. The analysis results indicate, the earth stress act on cement sheath in production, the maximum stress form on inwall of casing. Under the uniform load, casing collapsing strength is 7 times much bigger than that in the non-uniform load. With the augment of load ellipticity, the stress of casing inwall is bigger and stress distribution is misproportion. To enhance the cement elasticity modulus and reduce the most load stress of the casing effectively, the cement elasticity modulus range should be keep from 25 to 35 GPa in field production that can enhance the casing collapsing strength. In the uniform load, it is better to use the J55 casing. In the non-uniform load, using the P110 casing can reduce the stress and enhance the casing collapsing strength.