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建立了钻柱失稳的准螺旋模型，并用能量法推导出水平段和弯曲段钻柱的准螺旋失稳临界屈曲载荷，给出了水平段钻柱失稳后的摩阻力计算公式。计算结果表明，钻柱的准螺旋失稳临界载荷小于其完全螺旋失稳临界载荷。弯曲段井壁的约束增大了该段钻柱的刚度，因此，弯曲段钻柱的临界失稳载荷大于水平段的相应载荷值。室内模拟实验研究表明，准螺旋模型计算值与实验值较为接近，计算结果可供实际钻井作业参考。
The quasi - helical model of the drill string instability was established and the critical buckling load of the quasi - helix instability of the drill string in the horizontal section and the curved section was deduced by the energy method. The friction resistance formula of the horizontal section was obtained. The calculation results show that the critical quasi-helical instability of the drill string is less than the critical load of complete spiral instability. The restraint of the curved wall increases the rigidity of the drill string. Therefore, the critical buckling load of the drill string in the bent section is greater than the corresponding load value of the horizontal section. Laboratory simulation shows that the calculated value of the quasi-helical model is close to the experimental value, and the calculation result can be used for actual drilling operation.