动态内压力下油田超深井中厚壁套管的动力学响应和实验验证

Dynamic response of thick-walled casing in oilfield′s ultra deep well under kinetic inside pressure and experimental validation

引入中间主应力系数和拉压强度比,采纳统一强度理论求解动态内压力下两封闭末端、两开放末端和平面应变厚壁套管弹塑性极限内压力的解析解。塑性流动最初发生在厚壁套管内壁,且被周围的弹性材料所约束。数值模拟表明,弹性极限内压力随拉压强度比的降低和中间主应力系数的增加而增加;两封闭末端厚壁套管的弹性极限内压力最大,两开放末端厚壁套管的最小,平面应变厚壁套管的在两开放末端和两封闭末端之间;分界面的临界半径随动态内压力的变大而变大;若动态内压力增加时,厚壁套管从弹性变形转变为弹塑性变形,分界面的临界半径自内半径增大至外半径;塑性极限内压力随拉压强度比的减少而增加;随外内直径比的变大,当相等的统一强度理论参数时,两封闭末端、两开放末端和平面应变厚壁套管的塑性极限内压力之间的差距变小;弹性极限内压力低于塑性极限内压力;塑性极限内压力的理论数据与测试数据之间的相对误差为-3%～-9%,国际标准化组织样板数据与测试数据之间的相对误差为-12%～-25%,美国石油协会平均线与测试数据之间的相对误差为-16%～-33%。比较显示,厚壁套管塑性极限内压力公式更接近测试数据。

Introducing the intermediate principal stress coefficient and tensile-to-compressive strength ratio,the analytical solutions for elastic and plastic ultimate inside pressures in thick-walled casing respectively with two closed ends,two open ends and plane strain under kinetic inside pressure are obtained using the unified strength theory.Plastic flow first occurs on inside wall of the thick-walled casing,and is restricted by the surrounding elastic material.Numerical emulation displays that the elastic ultimate inside pressure adds as the tensile-to-compressive strength ratio decreases and the intermediate principal stress coefficient enhances.The value of the elastic ultimate inside pressure for the thick-walled casing with two closed ends is largest,followed by value for the plane strain one,and value for one with two open ends is minimal.The interfacial critical radius becomes larger due to the increase of the kinetic inside pressure.If the kinetic inside pressure ascends,the thick-walled casing diverts from elastic deformation to elastoplastic deformation and the interfacial critical radius expands from inside radius to outside radius.The plastic ultimate inside pressure gains as the tensile-to-compressive strength ratio reduces.The differences among the plastic ultimate inside pressures of thick-walled casings with two closed ends,two open ends and plane strain become smaller with the increment of the outside-to-inside diameter ratio for the equivalent unified strength theory parameters.The elastic ultimate inside pressure is lower than plastic ultimates.The relative error between theoretical values and test data for plastic ultimate inside pressure is between-3%--9%.The relative warp between international standardization organizations template data and test data is between-12%--25%.The relative windage between American petroleum institutes average lines and test data is between-16%--33%.Comparisons show that the current plastic ultimate inside pressures equation in thick-walled casing is closer to test data.