井下套管围压及第四等效应力分析

Confining Pressure and Von Mises Stress of Downhole Casing

随着油田开采期限的延长和增产措施的应用,地应力产生粘弹性围岩蠕变造成套管围压的增加是套管损坏的主要原因之一。建立了固井段套管、水泥环和围岩的地质力学模型,得出了套管第四等效应力和围压的解析解;建立了套管、水泥环和围岩的有限元分析模型,得出了套管围压与第四等效应力的数值解。给定工况,远地应力作用下套管等效应力解析解比数值解大3.0%;套管围压解析解和数值解差别小于0.3%。建立的有限元模型和推导的计算公式可以分析地应力作用下套管的围压及第四等效应力。

With the extension of production period and the application of well stimulation in oil field,the confining pressures which result from the in-situ stress often lead to the damage of cas-ing.Considering casing,cement and rock in cemented sections,a geomechanical model is estab-lished,while analytical solutions of Von Mises stress and confining pressure are obtained.A finite element method is developed to obtain the numerical solutions.The result shows that analytical and numerical solutions are almost equal.Under the action of the in-situ stress,compared to the numerical solution,the analytic solution of von Mises stress of casing is slightly increased by 3%. The difference between the analytic and numerical solution is less than 0.3%.Developed the finite element model of casing,cement and formation and analytic formulas can be used to analyze the confining pressure and Von Mises stress of casing under the action of the in-situ stress.