Effects of the Difference Between the Static and the Kinetic Friction Coefficients on a Drill String Vibration Linear Approach

Abstract

Stick–slip phenomenon in drill string is a self-excited vibration that is detrimental to the drilling equipment as well as to the drilling efficiency. Although there are a number of publications on this subject, there is yet not a generally accepted interpretation of its causes. In this paper, an analytical model that differs from the classical block-on-belt one is presented. The equation of motion of the drill bit in the slip phase is obtained and its solution determined for a set of parameters usually found in actual practice, which includes a drill string length of 3000 m. By choosing different sets of friction coefficients, the influence of the difference between the static and the kinetic ones on the occurrence of stick–slip vibration and the performance of the drilling equipment is investigated.