非均匀地应力条件下注水井泄压对套管受力的影响分析

The Effect of Water Injection Well Blowdown on Casing Stress under Non-uniform Ground Stress

注水井泄压导致套管损坏的现象在油田生产过程中时有发生,特别在非均匀地应力场和井眼几何形状不规则的情况下,套管柱承受的应力集中效应更为显著。为了分析非均匀地应力场注水井泄压过程套管应力的变化,采用有限元方法模拟计算了不同地应力场分布、椭圆水泥环不同弹性模量和泊松比以及不同椭圆度条件下的套管von Mises应力变化。结果表明:地应力差值变化对泄压水井套管应力不存在影响;椭圆水泥环弹性模量增加,水井泄压时套管所受的von Mises应力最大值减小,而泊松比增加,水井泄压时套管所受的von Mises应力最大值增大;水泥环椭圆度增加,套管上的von Mises应力最大值增大。

Casing damage caused by injection well blowdown often happened in the process of oilfield production.The stress concentration effect of casings was more obvious especially in the conditions of non-uniform ground stress field and borehole geometry irregularity.In order to analyze the casing stress change during the blowdown of injection wells in nonuniform ground stress field,a finite element method was used to simulate the von Mises stress change under the condition of different ground stress fields,different elastic modulus and different Poisson's ratios and different ellipticities of elliptic cement sheath.The results show that difference of ground stress change has no effect on casing stress of blowdown in injection wells,the maximum value of von Mises stress of casings during the blowdown decreases with the increasing of elastic modulus and increases with the reduction of Poisson's ratio and ellipticity of cement sheath.