Evaluation of distributed damping subs with active control for stick–slip reduction in drilling

Abstract

Drill string vibrations can cause damage to the equipment and reduce drilling performance. There are two primary methods to address this issue: top drive control or the use of specialized tools near the bottom hole assembly (BHA). Another previously published idea is to have several torsional damping sleeves along the drill string, adding viscous damping to the system. The sleeves are designed to be non-rotating, held in place by static friction, but if the combination of braking coefficient and relative pipe velocity gets too high, the sleeve will slip. This paper examines the effectiveness of active control of the braking coefficient, using an On–Off-based control scheme with proportional control. Stability maps are employed to assess the effects of this control scheme on the system for various combinations of top drive feed rates and revolutions per minute (RPM) set points. Such maps allow for a performance comparison of passive sleeves and active sleeves. The results show that active control can improve the drill string behavior both when drilling and when rotating off-bottom, by reducing the slippage of the sleeves. The settling time is reduced to up to a third of the settling time of the passive sleeves.