EXPERIMENTAL AND NUMERICAL DRILL STRING MODELING FRICTION INDUCED STICK-SLIP

A successful oil and gas prospecting requires many efforts to overcome the encountered challenges, such as axial, lateral and torsional vibrations. These phenomena may cause premature component failures of the drilling system, dysfunction of measurement devices, and increase of time and costs of the prospecting process. Torsional vibrations are present in most drilling processes and may reach an undesired severity state: stick-slip. An improved understanding of the stick-slip phenomenon may provide tools to avoid the increase of prospecting time and costs, assuring the investment and success of the drilling process. In this paper, it is described a numerical/experimental procedure with a non-linear friction aiming to induce stick-slip. The friction model is based on dry friction imposed by a specially designed test rig with a braking device. The non-linear behaviour of the experimental apparatus is analysed and the numerical model will be validated comparing experimental and numerical bifurcation diagrams. Also, it is performed a sensitivity analysis of the experimental apparatus parameters. Bruno C. C. Andrade, Cesar A. L. L. Fosenca, Hans I. Weber