Complex dynamics of drill-strings: Theory and experiments

Abstract

We investigate complex drill-string dynamics in a downhole drilling where strong nonlinear interactions between various types of vibration take place. First, we present a low dimensional model of the downhole drilling where a drill-bit cutting a rock formation has a strong coupling between torsional and axial oscillations. The model can be used to study drilling stability as an example results are given. Then we introduce a new experimental rig developed by the Centre for Applied Dynamics Research at the University of Aberdeen, capable of reproducing all major types of drill-string vibration. One of the most important features of this versatile experimental rig is the fact that commercial drill-bits, employed in the drilling industry, and real rock-samples are used. The rig operate in different configurations, which enables the experimental study of various phenomena, such as stick-slip oscillations, whirling and drill-bit bounce. It also allows to determine mechanical characteristics of the drill-bits, which are used to calibrate mathematical models.

An inverse problem via cross-entropy method for calibration of a drill string torsional dynamic model

“…The equipment used in oil prospecting operations, called drill string, is a long, slender structure under rotation, connected by drill-pipes and auxiliary apparatus. Diverse mechanisms influence in its performance: nonlinear interaction of multiple vibration modes, friction and shock effects, internal and external non-Newtonian flow, hysteretic interaction on the rock contact, etc (Wiercigroch et al, 2018;Spanos et al, 2003). The complexity of its dynamics warrants further works on the modeling approach and the use of numerical procedures that are efficient on the identification of its underlying values (Cunha Jr et al, 2015;Liao et al, 2018;Aguiar, 2010).…”

A Review Dynamic Vibration on Drill String in Drilling Operation

“…Nonlinear interaction between various vibrations like whirling vibration, axial and torsional oscillation. Low dimensional models can be used to study drilling stability based on stick slip and bit bounce (Wiercigroch et al, 2018).…”