在非常规油气藏水平井钻进过程中,井壁稳定性差导致井眼不规则,钻柱受力复杂,摩阻扭矩计算误差较大。根据纵横弯曲连续梁理论,在井斜平面、方位平面内对钻具组合进行管柱受力及变形分析,从而建立了一种含有虚拟接触点的改进纵横弯曲梁模型分析钻井管柱摩阻扭矩。优点在于指定接触点时不用考虑是否为真实接触点,由此可将接头或接箍、扶正器等直径较大的部位指定为接触点。对于非真实接触点可以按虚拟接触点考虑,从而使模型的应用和求解更加方便、可行。实例分析结果表明,套管下入、旋转钻进、滑动钻进、复合钻进状态下管柱摩阻扭矩理论计算值与实测平均值基本相同,且变化趋势一致,验证了计算模型的准确性。
Calculation of torque and drag is analysis of mechanics and deformation of drill string in essence. Based on uniform vertical and horizontal bending beam theory, parameters are decomposed in deviation plane P and azimuth plane Q, and mechanics and deformation of drill string is analyzed, then modified uniform vertical and hori- zontal bending beam model with virtual contact point is constructed to analysis torque and drag. When a contact point is appointed, it is not confirmed true necessarily, connector and stabilizer are appointed contact points, non- true contact point can be appointed virtual contact point. All the advantages make model applied and solved easily. The results of case study show that on condition of casing running, rotation drilling, sliding drilling and compound drilling , computational solution of torque and drag is same as average of real time data, and change rule is same too. All data verify accuracy of model built.