Annulus Whirling Motion Analysis of the Rotary Drill String by the Action of Hydrodynamic Pressure And Friction Force

摘要

This paper studied the annulus whirling motion of rotary drill string. The drill string whirling motion is caused by the perturbing pressure produced by both hydrodynamic pressure of drilling fluid and the bending deformation of the drill string. Here, hydrodynamic pressure comes form fluid both inside and outside drill string; the bending deformation is derived from the dynamic conditions which guarantee a regular drill string whirling. In this paper, we present a mathematics model describing the annulus whirling motion and derive a critical condition of unstable whirling of the drill string. Furthermore the paper discusses in detail the physical mechanism and operating laws of the drill strings whirling caused by the action of drilling fluid inside and outside the drill string, the whirling motion analysis of the drill string collision and friction the Wall of the well.