超深井钻具接头极限工作扭矩图版及其应用

在深井、超深井中,钻具接头由于要承受较大的轴向拉力作用,其抗扭性能受到很大的限制;同时,由于井下情况复杂钻柱遇卡现象时有发生,而顶驱设备的出现使得大轴向力解卡作业时旋转钻柱成为可能,此时钻具接头承受很大的轴向载荷和扭矩联合作用,可能处于极为危险的状态,因此快速准确地确定不同轴向拉力条件下钻具接头的抗扭性能是保障作业安全的关键。API标准中虽提供了拉、扭耦合条件下钻具接头极限载荷的确定方法,但由于基于很多假设性条件,所得结果与实际情况间存在较大误差,特别是在深井、超深井等复杂钻井作业中,这种误差更大。基于钻具接头的三维弹塑性有限元分析,分别计算了3种主流规格钻具接头在不同轴向拉伸载荷条件下的极限工作扭矩,通过对计算结果的多项式拟合,得到钻具接头的极限工作扭矩计算公式,并绘制出钻具接头的极限工作扭矩图版,形成实际工况下的钻具接头极限工作扭矩快速确定方法。

Ultimate working torque chart of tool joints in ultra deep wells and its application

In deep and ultra deep wells, the torsional property of tool joint is highly limited by large axial tensile. Moreover, stucks are frequently encountered during drilling due to complex down-hole situation, while it is possible to twist drill string when using top drive equipment for unstuck operation with larger axial force. In the meantime, tool joints undergo the combined effect of axial load and torque, which may lead to an extreme danger. Therefore, to rapidly determine the torsional property of tool joint under different axial tensile is a key to ensure safety operation. Although API RP 7G provides the method for determining the ultimate load of tool joint under tensile and rotary coupling conditions, a great error exists between the results and the fact due to many hypothetical conditions. Such error may become greater particularly in complex drillings of deep and ultra deep wells. Based on the 3D elasto-plastic finite element analysis of tool joint in this study, the ultimate working torques of three main tool joints were calculated under different axial tensile load conditions. The calculation equations of ultimate working torque were obtained through polynomial fitting of the calculated results, and charts were developed for the ultimate working torque of tool joints, thus establishing a method to rapidly determine the ultimate working torque of tool joint under the actual working conditions.