钻柱螺旋屈曲时钻速与轴向力间的关系

在研究垂直井眼中钻柱在自重作用下发生屈曲时,一直沿用Lubinski的临界钻压条件得出结论,但该结论是在静态下考虑钻柱的失稳问题时获得的,由于钻柱还会受到其他因素的影响,因而该结论具有明显的缺陷。鉴于此,通过考虑离心力和重力对钻柱屈曲的影响,运用能量法研究了钻柱最大转速与螺旋屈曲时临界轴向力间的关系。根据能量法原理,确定钻柱的弯曲变形能等于重力做的功和离心力做的功之和,推导了钻速和轴向临界力间的数学关系表达式。研究结果发现,在工作状态下,钻柱的临界压力会明显地小于静态时的临界力,这在一定程度上弥补了Lubinski无重钻杆螺旋失稳条件的缺陷。对实际的钻探工程来说具有十分重要的指导意义。

RELATIONSHIP BETWEEN THE AXIS CRITICAL FORCE AND THE SPEED OF THE DRILL STRING WITH HELICAL BUCKLING

The usually applied buckling criterion of drill sting is Lubinski's axis critical force when investigating the buckling of drill sting in deep straight well.However,this criterion is obtained in studying the buckling of drill sting at static state.In engineering,the dill sting will affected by a lot factors.As a result,there are defects in this criterion.Consequently,this paper investigates the relationship between the axis critical force under helical buckling and the maximum speed of drill string.According to the energy method,we first consider that the helical buckling energy of drill string equals the work of the eccentric force plus the work of the gravity and then obtain a mathematics model for the speed and axis critical force.Considering the inertial eccentric force and the weight of the drill string,we find that the axis critical force will be obviously less than that under the static state,which makes up for the Lubinski's axis critical force criterion and should be very important in drill engineering applications.