Suppression of the bending vibration of drill strings via an adjustable vibration absorber

Abstract

Vibration control of the drilling process in the gas and oil industries is of great importance. Applying an effective control system diminishes both costs and process time and increases work efficiency. Typically, the drill string vibrates in a combination of three distinct modes of transverse, torsional, and axial vibrations. Due to the importance of torsional vibration and the associated stick-slip phenomenon, many works have been devoted to this area. However, transverse vibration is another major source of vibration arisen from the long length of the drill string structure. In this paper, a tunable vibration absorber as a semiactive controller is designed to suppress the transverse vibration. After modeling the drill string as an Euler-Bernoulli beam and formulating the problem, the optimum specifications of the absorber, such as spring stiffness, absorber mass, and its position, are determined using an algorithm based on the mode summation method. The effect of bit rotational speed under the non-resonance and resonance condition is studied. It is shown that the best position of the absorber depends on the spring stiffness and bit rotational speed.