Stability of transverse vibration of drillstring conveying drilling fluid

In this paper, an analytical model is proposed to predict lateral vibration of a drillstring in a vertical well. The effect of parameters, such as stiffness of spring, average weight on bit (WOB), amplitude of fluctuating WOB and so on, on the dynamic stability of the drillstring is discussed. It is found that the interaction between the drillstring and drilling mud has a great influence on drillstring buckling and dynamics. For constant drilling pressure, the mud flow rate stabilizes the drillstring under certain conditions, but the fluctuating WOB drives the drillstring parametric resonance.