考虑热固耦合作用的高温高压井井筒完整性分析

以高温高压井套管-水泥环-地层为研究对象,建立套管-水泥环-地层组合系统的热固耦合模型,结合边界条件和连续条件,得到相应的应力解析解,并与有限元结果进行对比,验证了解析方法的计算精度.通过分析热固耦合作用下的解析解和不考虑热载荷的解析解,发现热载荷对整体等效应力的影响较大.采用Mises、Drucker-Prager及Mohr-Coulomb屈服准则定义失效系数评价套管-水泥环-地层组合系统的井筒完整性.讨论了水泥环弹性模量、泊松比、非均匀地应力系数、地层温度、套管内压等参数对套管内壁、水泥环内壁及第一、二胶结面失效系数的影响.上述因素对套管内壁、水泥环内壁及第一、二胶结面失效系数均有影响;第一胶结面失效系数较高,对井筒完整性影响较大.

Integrity analysis of high temperature and high pressure wellbores with thermo-structural coupling effects

Taking a composite system of casing-cement sheath-formation in a high temperature and high pressure oil well as the research object,a thermo-structural coupling model is constructed and its theoretical solution is obtained by considering contact,continuity and boundary conditions.The theoretical solution is very accurate in comparison with FEM solution.Comparing the theoretical solutions with thermo-structural coupling effects and without thermal load,it is indicated that thermal load has much greater influence on the equivalent stress.Failure coefficient,which is used to analyze structure integrity,is defined by Mises,Drucker-Prager and Mohr-Coulomb yield criteria.The factors of elastic modulus,Poisson's ratio,nonuniform in-situ stress coefficient,formation temperature and casing pressure are discussed by considering the failure coefficient distribution of casing-cement sheath-formation.The results show that the above factors have great effect on the failure coefficient distribution.The failure coefficient of the 1 st cementation plane is greater than that of other planes and its influence on wellbore integrity is large.