The Effect of Dynamical Parameters on Precession in Rotary Drilling

Abstract

Precession, which is the rolling motion of the drillstring on the walls of the borehole, is investigated by considering the various possible motions of a rotating disk in a circular hole. Due to the simplicity of the model, closed-form results are derived on the stability of precession and on the evolution of impacting motions towards precession. It is found that increasing coefficients of friction and contact damping have a favoring effect on precession, while the stiffness and damping of the drillstring bending mode have an opposing effect.

Nonlinear vibration analysis of an axially moving drillstring system with time dependent axial load and axial velocity in inclined well

“…In Figs. (12) and (13) the frequency response curve and stability results are presented for first and second mode. The continuous line represents the stable response and the dashed line represents the unstable response.…”

“…Also, in Figs. (12) and (13) frequency response curve is plotted for different mass eccentricity. According to these figures, by increasing the mass eccentricity, two branches will diverge and the unstable region increases.…”

“…Theoretical investigation of the lateral drillstring vibrations was initiated with the so called Jeffcott model which was a relatively simple low-dimensional approach [4,[10][11][12][13]. Also, continuous model was employed for studying the lateral vibrations of the drillstring [14][15][16].…”