基于能量法的定向井中造斜段下凹管柱屈曲临界载荷分析

Analysis of critical buckling load of concave curved pipe string located in the deflecting section of a directional well based on energy analysis method

运用最小势能原理导出定向井造斜段下凹管柱屈曲载荷计算公式。以常见管柱参数为例,编制了相应的MATLAB程序,计算了不同条件下管柱屈曲临界载荷,分析了井眼曲率半径、平均井斜角、油套径向间隙对管柱临界屈曲载荷的影响。分析结果表明:定向井造斜段下凹管柱屈曲临界载荷随井眼曲率半径的增大呈指数递减趋势,随平均井斜角的增大而指数递增;管柱壁厚的增加会提高管柱抵抗屈曲变形的能力,但这种影响会随井眼曲率半径、油套管径向间隙的增大而减小。本文研究结果可为定向井射孔、试油、改造及完井投产管柱组合及下入提供参考。

The formula calculating buckling critical load of concave curved pipe string in the deflecting section of a directional well is derived according to minimum potential energy principle. The corresponding MATLAB programs are prepared based on the parameters of common pipe-string,the influences of the borehole curvature radius,the average deviation angle and the radial clearance between tubing and casing on the critical buckling load are analyzed. It is shown that: the critical buckling load will decrease exponentially with the increase of the borehole curvature radius,and increases exponentially with the increase of the average deviation angle; the ability of pipe string resisting buckling deformation will be enhanced by increasing the wall thickness of the pipe string,but the influence will weaken with the increase of the borehole curvature radius and the radial clearance between tubing and casing. These research results can provide reference for the perforation,the oil testing,the reservoir reconstruction and the combination and trip-in-hole of well completion pipe string.