Torque Feedback Used to Cure Slip-Stick Motion

Abstract

Abstract A novel idea to control the rotary speed incorporates the torque signal, in addition to the speed signal, to produce a more uniform motion of the drillstring. This method is easily incorporated into existing equipment used to control the rotary speed. We have tested this control system on a full-scale research drilling rig and have demonstrated that such a system can stop slip-stick motion and prevent it from starting. As an additional benefit, such a control system leads to smoother rotation of the bit which can lead to a reduction in axial and lateral vibrations of the drillstring. In this paper we present the theoretical basis behind such a system and give an example of the experimental results.