垂直井中旋转钻柱受拉段分岔研究

在以往对钻柱稳定性的研究中 ,人们对受压段钻柱的稳定性问题给予了足够的重视 ,而对受拉段钻柱稳定性的研究则明显不足。钻柱属于细长柔性杆件 ,大部分钻柱在工作时处于受拉状态。在旋转钻井作业中 ,当钻柱较长且转速与拉力存在某种关系时 ,钻柱受拉段也会发生屈曲变形。考虑到垂直井中钻柱受拉段在旋转时的转动效应 ,建立了顶部悬挂、受分布浮重作用的旋转细长钻柱的分岔微分方程。通过对方程的数值求解 ,得到了相应的分岔值曲线。利用该计算模型可以模拟石油钻井工程中旋转细长钻柱受拉段的工作状态 ,所得结果对钻井作业具有一定的指导意义。

STUDY ON BIFURCATION FOR TENSILE ROTATING DRILLSTRING IN VERTICAL SECTION OF WELL

studies are in focus of the stability of the drillstring in compression, and little literature with focus on that of the drillstring in tension. The drillstring is a slender and flexible bar. The most part of the drillstring is in tension while working. In rotary drilling, the drillstring being in tension may be buckling when there exist some definite relations between tensile force and the rotary speed. Taking into account the rotating effect of the drillstring, this paper presents a bifurcating differential equation for the rotating slender drillstring being in tension in vertical well section. Solving the equation numerically can obtain the bifurcating value curves. The differential equation can be used to simulate the working state of the tensional section in the rotary slender drillstring in vertical well section.