三维复杂井眼上提冲放套管屈曲摩阻模拟研究

针对复杂井身结构、复杂井眼轨迹和井径变化导致的套管下放困难甚至不能到达预期井深的问题，开展了三维复杂井眼上提冲放套管屈曲摩阻研究。在螺旋屈曲套管附加摩阻理论的基础上，利用有限元分析，以H井实际工况参数建立三维复杂井眼套管“上提冲放”作业过程的有限元模型。利用该模型对全井段套管受力及屈曲变形情况进行了分析，结果表明，H井直井段套管在冲放瞬间及自由稳定后所受的轴向力大于其螺旋屈曲临界载荷，从2 000 m井深至造斜点之间井段发生了严重的螺旋屈曲变形，套管螺旋屈曲附加摩阻太大而自锁，下部套管无法传递动力出现下放困难。该类三维复杂井眼套管下放困难机理对复杂井眼套管柱屈曲形态损伤及其失效研究具有重要意义。

A Simulation Study on Buckling Friction Resistance of Casing Uplift and Flushing in Three-dimensional Complex Well

In the casing lowering process, it is difficult or even unable to reach the expected well depth due to complex wellbore structures, complex wellbore trajectories and well diameter changes. Intending to solve this problem, a simulation study on buckling friction resistance of casing uplift and flushing in three-dimensional complex well is carried out. Based on the theory of additional friction in helical buckling sleeves, a three-dimensional finite element model of the“ up-and-push” operation of a complex wellbore casing was established based on the actual operating parameters of Well H by ABAQUS. The model was used to analyze the casing stress and buckling deformation of the whole well section. The results of analysis show that the axial force of the casing in the vertical well section of Well H at the moment of flushing and releasing and after free stabilization is greater than its helical buckling critical load, there was severe helical buckling deformation in the section between the well depth of 2 000 m and the deflection point, the lower casing is unable to transmit power and has difficulty in lowering. It reveals the mechanism of this kind of three-dimensional complex wellbore casing down-diffusion, which is of great significance for the research on buckling morphological damage and failure of complex wellbore casing strings.