Numerical and experimental studies of stick-slip oscillations in drill-strings.
Paez Chavez, Joseph
De Sa, Rulston
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LIU, Y., PAEZ CHAVEZ, J., DE SA, R. and WALKER, S. 2017. Numerical and experimental studies of stick-slip oscillations in drill-strings. Nonlinear dynamics [online], 90(4), pages 2959-2978. Available from: https://doi.org/10.1007/s11071-017-3855-9
The cyclic nature of the stick-slip phenomenon may cause catastrophic failures in drill-strings or at the very least could lead to the wear of expensive equipment. Therefore, it is important to study the drilling parameters which can lead to stick-slip, in order to develop appropriate control methods for suppression. This paper studies the stick-slip oscillations encountered in drill-strings from both numerical and experimental points of view. The numerical part is carried out based on path-following methods for non-smooth dynamical systems, with a special focus on the multistability in drill-strings. Our analysis shows that, under a certain parameter window, the multistability can be used to steer the response of the drill-strings from a sticking equilibrium or stick-slip oscillation to an equilibrium with constant drill-bit rotation. In addition, a small-scale downhole drilling rig was implemented to conduct a parametric study of the stick-slip phenomenon. The parametric study involves the use of two flexible shafts with varying mechanical properties to observe the effects that would have on stick-slip during operation. Our experimental results demonstrate that varying some of the mechanical properties of the drill-string could in fact control the nature of stick-slip oscillations.