Abstract: A 3-D mechanical model for calculating the frictional resistance of the whole drill-string in horizontel well is built,and the mechanical analysis on frictional resistance of drill string with gap element method was put forward.Taking into account the influence of the bending rigidity of drill string on its deformation and frictional resistance,a calculation procedure for the contact force,frictional force(including the frictional resistance moment)and distribution pattern along the axial line of drill string that produced by whole drill-string and well wall in 3-D space is given,and the corresponding software is made.The field experiment shows a good result.The average error of the result in field test is less than 5.5%,in comparison with the theoretical forecasted frictional resistance,which proves that the mechanical model and theoretical method presented in this article is correct and valid.A theoretical basis may be provided for analyzing and forecasting the frictional resistance in horizontal drilling.A high calculation precision can be obtained.

Key words: horizontal drilling, whole drill-string, frictional resistance, gap element method, finite element method

摘要： 建立了用于计算水平井整体钻柱摩阻的三维力学模型,提出用间隙元理论对钻柱摩阻力进行力学分析的方法.考虑到钻柱的抗弯刚度对钻柱受力变形和摩阻力的影响,给出了三维空间中的整体钻柱与井壁的接触力、摩擦力(包括摩阻力矩)及其沿钻柱轴线分布规律的计算方法,编制了相应的计算机软件.现场实验表明,实际应用效果良好,理论预测摩阻和现场实测结果的平均误差在5.5%以下.该力学模型和理论方法为水平井摩阻分析预测提供了理论依据,并具有较高的计算精度.

关键词: 水平井, 整体钻柱, 摩阻力, 间隙元法, 有限元法, 力学分析