3D numerical simulation study of rock breaking of the wavy PDC cutter and field verification

摘要

The structure of polycrystalline diamond compact (PDC) bits is a key factor in improving their rock-breaking efficiency. To further study the rock-breaking mechanism of the wavy PDC cutter, a 3D finite element model of the dynamic rock breaking of the PDC cutter was established, and a comparative study on the rock-breaking process of the wavy PDC cutter and the conventional PDC cutter was conducted. The results show that the wavy PDC mainly breaks the rock by ploughing and shearing, which results in a higher rock-breaking efficiency. The cutting force of the wavy PDC cutter is 6.64% lower than that of the conventional PDC cutter, and its fluctuation is obviously smaller. With an increase in back-rake angle, the cutting force, its fluctuation, and the mechanical specific energy (MSE) increase, and the optimal back-rake angle is 10 degrees-15 degrees. With an increase in cutting depth, the cutting force and its fluctuation in the wavy PDC cutter increase, the MSE decreases, and the optimal cutting depth is 2 mm. As the number of waves increases, the cutting force and MSE of the PDC cutter increase first and then decrease, and the greater the number of waves, the larger the fluctuation of the cutting force. The cutting temperature of the wavy PDC cutter is lower than that of the conventional cutter, it decreases with an increase in the back-rake angle and number of waves, and gradually increases with an increase in cutting depth. The main results of this work will help to reveal the process of rock breaking and the mechanism of the wavy PDC cutter, thus contributing to the achievement of a high rate of penetration and efficiency in the drilling process of hard formations with PDC bits.