Abstract: The curvature of a directional well bore greatly affects the stress state of the drill string. The control of the well path needs a careful analysis of the stress and deformation of the bottom part of the drill string or the BHA. A three-dimensional static analysis of the drill string has been done with the finite element method. some modifications introduced in this paper make the finite element method more suitable for this analysis. A new method for solving the contact problems of the drill string with wall of the well is presented to reduce computing cost. Analysis of the performance of the common types of BHA shows the effects on the bit side forces of such factors as WOB, inclination angle, well bore enlargement, three-dimensional curvature of the well bore and torque on the bitetc.

摘要： 定向井眼的弯曲形态,极大地影响了钻柱的受力状况,井眼轨迹控制特别要求对钻柱的最底端,即下部钻具组合进行深入的受力与变形分析。本文将有限单元法应用于下部钻具组合的三维静力分析。由于对处理方法做了一些改进,使有限单元法更适用于弯曲井眼中的钻柱受力与变形分析。针对钻柱与井壁的接触间题,文中提出了一种新的计算方法,大大缩短了这类问题的计算时间。对一些下部钻具组合进行了分析并论述了钻压、井斜角、井眼扩大、井眼三维曲率和钻头扭矩对钻头侧向力的影响。