Stick-slip vibration behaviors of BHA and its control method in highly-deviated wells

Abstract

Stick-slip vibration is a common phenomenon met in oil gas drilling, especially in the complex trajectory wells such as highly-deviated wells, it will cause the earlier failure of BHA (bottom hole assembly) and lower drilling efficiency. In this present paper, a finite element model of highly-deviated well, which consists of a drill string system, a borehole, a PDC bit (Polycrystalline Diamond Compact bit) and a rock model, is carried out to investigate the stick–slip vibration behaviors of drill bit and BHA. Besides, the torsional impact drilling method is proposed in the context to control the stick–slip vibration of BHA. The research results show that, the phenomenon of stick–slip vibration of BHA gradually weaken and disappear with the distance from the drill bit increases, and the stick–slip vibration mainly occurs at the BHA which near drill bit. The high frequency torsional impact drilling method can reduce the resistance torque of the bit by 34.71%, and increase the drilling depth by about 58.28%. It can effectively improve the drilling efficiency of the bit, making the rotation of drill bit becomes relatively more stable, and reducing or even eliminating the stick–slip vibration. These results lead to an enhanced understanding of stick–slip vibration behaviors of drill bit and BHA in highly-deviated wells, and provide the basis for improving the drilling efficiency.