径向井钻杆转向阻力建模及实验分析

径向井钻杆的转向是承受内压曲杆反复弹塑性弯曲过程。由于系统的非保守性 ,其匀速钻进状态也不能应用静力平衡方程。将钻杆的运动态作为静止稳定状态的失稳 ,运用线性小位移理论 ,求解钻杆保持静止状态的条件 ,建立了钻杆发生运动的极限载荷、曲率突变点阻力等模型。根据径向井钻杆载荷的边界条件 ,提出了径向井钻杆转向过程中存在临界载荷系数的论断 ,求得了常用径向井转向器的临界载荷系数。计算结果与实验进行了对比分析 ,对径向井现场试验中表现出的钻杆遇阻现象给出了可信的解释。

Modeling and experimental analysis of turning resistance of drill pipe in horizontal holes

The turning of drill pipe of URRS (ultrashort radius radial system) is an elastoplastic alternating bending process under inner pressure. The equilibrium equations are not suitable to the constant velocity status because of non-conservatism of the system. By taking the pipe motion as buckling from stationary state, and by searching the boundary condition of static equilibrium by means of small displacement theory, the models for the limit load of the drill pipe and the axial resistance at curvature interruption point are established. Based on the limit load model and boundary restriction of URRS drill pipe, it is indicated that there exists the critical load coefficient in the course of drill pipe turning, and the critical load coefficient of the common whipstock is calculated. The calculation result is compared with the experiments, and a convincible explanationfor the drill pipe stay in the hole is given.