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大位移井具有长水平位移,大井斜角以及长裸眼段的特点,大位移井钻井过程中摩阻扭矩的预测和控制是成功地钻成大位移井的关键因素之一。文章根据大位移井钻井的特点,忽略钻柱刚度的影响,考虑到实钻轨迹中井斜,方位的变化,采用空间斜平面假设,建立了适合大位移井的摩阻扭矩三维软杆计算模型,并编制了计算程序,建立的模型可用于计算大位移井各种工况下的摩阻和扭矩,实例计算表明,文中提出了的力学模型其理论计算结果与实测结果吻合程度较好,大钩载荷误差在15%以内,扭矩载荷误差基本上保持在20%以内。

Mechanical Model for Calculating Drag and Torque in Extended Reach Well

The extended reach well has such chara cteristics as large horizontal displacement,great deviation angle and long open hole interval.Predicting and controlling the drag and torque in the process of d rilling extended reach wells is one of the key factors to ensure to be successfu l in the drilling.In this paper,a 3 D "soft string"drag and torque calculat ion model suited to extended reach well is set up and the relative calculation p rogram is drawn up in view of the characteristics of extended reach well and the change of the inclination and azimuth of the real well trajectory,and neglectin g the influence of drillstring rigidity and supposing the space to be a slant pl ane.The model can be used for calculating the drag and torque under different op erating conditions.Through example calculation,it is shown that the theoretical calculation results by the mechanical model proposed in this paper have a good c oincidence with the practical measurement results,the error in hood load being l ess than 15% and that in torque load less than 20%.