Study On The Influence Mechanism Of PDC Bit Stick-slip Vibration Under Torsional Impact

On the drilling engineering,the stick-slip vibration on the PDC bit appears frequently,leading to premature failure of the bit.Torsional impact drilling technology and equipment can effectively eliminate the stick-slip vibration of the PDC bit,can effectively improve the drilling speed,protect bits and drilling tools.The application of the impact in the field achieve very good results.The mechanism of the stick-slip vibration of the PDC bit is not clear,in order to further expand the application of torsion impact drilling technology in the field,the influence mechanism of the PDC bit stick-slip vibration under torsional impact is studied.Firstly,the mechanism of the stick-slip vibration of the PDC bit is analyzed,and the theoretical model of the effect of torsional impact force on the stick-slip vibration of the PDC bit is established.The theoretical calculation is conducted.The results show that:(1)As the impact force increases,the speed fluctuation of the drill bit decreases gradually,the greater the impact force,the better the inhibition of the stick-slip vibration;(2)With the impact force increasing,the inhibition of the drill bit speed first decreases and then increases,and there is an optimal value so that the inhibition of the bit stick-slip vibration is the best.Secondly,the experimental model is simplified and the friction contact between the PDC tooth and the rock is studied by the experiment.The influence of the impact force and the impact frequency on the PDC stick-slip vibration is explored.The inhibition mechanism of PDC bit stick-slip vibration under torsional impact is achieved.The experimental results show that:(1)With the impact force increasing,the effect of the impact on the stick-slip vibration increases.(2)With the impact frequency increasing,the effect of the impact on the stick-slip vibration decreases first and then increases and then decreases;(3)With the increase of the contact surface size,the effect of impact on the viscous sliding vibration increases first and then decreases and there is an optimal contact surface size.Then,the influence of torsional impact on the stick-slip vibration of PDC bit is studied by numerical simulation.The influence of different impact amplitude and impact frequency on the stick-slip vibration of the PDC bit is analyzed.The results show that the stick-slip vibration of the PDC bit is effectively inhibited obviously.There are optimal torsional impact force and impact frequency which make the effect of sticking vibration of PDC bit to be the best.In this paper,the mathematical model of the influence of torsional impact force on the sticking and sliding vibration of PDC bit was established.The experimental study on the stick-slip vibration of PDC bit by torsional impact was completed.The numerical simulation of the stick-slip vibration of the PDC bit was completed,and the influence mechanism of the torsional impact on the stick-slip vibration of the PDC was revealed.The results show that: the torsional impact can effectively inhibit the stick-slip vibration of the PDC bit,and provide a reliable reference for the application of the reverse drilling technology in the field.