Dynamic behavior of a drill-string: experimental investigation of lateral instabilities

This paper focuses on laboratory tests concerned with the lateral behavior of a rod representative of part of a drill-string in the area of rotary oil drilling. The original experimental set-up takes into account the curvature of the rod, mud, stabilizers and rotation speed. The lateral behavior of the drill-string subjected to the axial excitations of the bit is governed by time varying parameter equations due to torsion-lateral and longitudinal-lateral couplings. The experimental results highlight the different kinds of lateral instabilities and they are compared either with existing experimental, or theoretical results. The experimental investigation described in this paper is included in a wide ranging study which also involves theory and the development of a computer code, both briefly presented here.