Drill-string vibration analysis considering an axial-torsional-lateral nonsmooth model

Oil drilling operations is usually associated with drill-string severe vibration conditions that lead to an onerous and inefficient process. In order to avoid or minimize the impact of vibrations on operation conditions it is essential a deep dynamical investigation that allows a proper understanding of system dynamics. Drill-string dynamics may be analyzed by considering different vibration modes: axial, torsional and lateral. The coupled analysis of these modes gives a proper comprehension of the system dynamics, elucidating several critical vibration responses. In general, lumped models present a proper description of the system dynamics. This paper deals with a coupled drill-string vibration considering a four-degree of freedom nonsmooth model that presents axial-torsional-lateral coupling. Bit-rock and wellbore interactions, eccentricity and hydrodynamic forces due to fluid resistance to lateral bending are the main system coupling aspects. A parametric study is carried out treating bit-bounce, stick-slip, whirl, and the combined effects. Numerical results present qualitative agreement with experimental field observations. Critical operational conditions are discussed especially those related to interaction among bit-bounce, stick-slip and whirl conditions.