Severity Analysis of Stick-slip Bifurcation in Drill-string Dynamics under Parameter Variation

Abstract

Bifurcations are an interesting class of dynamic behavior exhibited by many nonlinear systems. Drill string typically employed in underground oil exploration are highly nonlinear systems whose dynamic behavior has generated huge research interest. Though it is well-known that typical drill-strings behave like piecewise smooth systems and the severity of bifurcations they exhibit has not been studied in depth. In this work, a two degree of freedom (2-DOF) model of the drill-string is constructed and its dynamic behavior. In-depth analysis of the effect of parameter variation on the severity of bifurcations is conducted. This can potentially deliver key insights in the design of control strategies aimed at suppressing problematic stick-slip oscillation.

Eliminating Stick-Slip Vibrations in Drill-Strings with a Dual-Loop Control Strategy Optimised by the CRO-SL Algorithm

“…In severe cases, this can lead to faster degradation of drill-bits and in rare cases warping or breaking of the drill-string [1]. To thoroughly understand this highly nonlinear phenomena, several drillstring models have been proposed in the literature [2][3][4][5]. Consequently, several bit-rock interaction models have also been proposed and validated [4,6,7].…”