Experimental and numerical investigation on the relationship between stick-slip vibration and rate of penetration

Severe torsional vibration of the drill string is referred to as stick-slip. Although it is widely believed that drill string vibration can affect drilling efficiency, there have been no detailed reports on the relationship between stick-slip vibration and rate of penetration (ROP). The main causes of stick-slip vibration are the drill bit rock breaking and the friction between the drill string and the wellbore. Regardless of the cause, in the absence of stuck pipe, the interaction between the drill bit and the formation rock directly determines ROP. Therefore, this paper studies the relationship between stick-slip vibration and ROP through laboratory experiments and numerical simulation. The results show that the intensity of torsional vibration of the drill bit increases as the weight-on-bit (WOB) rises and the torsional stiffness of the drill string decreases, eventually leading to the occurrence of stick-slip vibration. However, the ROP did not show a significant change with the increase of torsional vibration intensity. Although the ROP is almost 0 during the stick phase, it is relatively high when the drill bit enters the slip phase. In addition, the axial displacement curve shows a stepwise increasing characteristic. The average footage during the stick and slip stages is basically equal to that without significant torsional vibration. While the stick slip vibration does not directly affect the ROP, severe torsional vibration can accelerate the wear of the drill bit, thereby reducing the rock breaking efficiency of the drill bit and lowering ROP. The research results of this paper advance the knowledge of drill string vibration.