Three-dimensional simulation of rock breaking efficiency under various impact drilling loads

Percussion drilling is believed to be an efficient way to enhance the drilling performance, compared with the conventional drilling in deep wells, which could be achieved by applying impact loads above the drill bit. The finite simulation is an efficient method to predict the drilling performance when the drill bit interacts with rocks. In contrast, as results of finite element technology limitation, the conventional way is to apply the displacement or velocity boundary conditions on the bit; however, this is completely different from the real field drilling process. Therefore, in this paper, a 3-D rock-bit physical model is presented to simulate the practical percussion drilling under various types of loads; at the same time, experiment was conducted to validate the effectiveness of the rock-bit model. The results demonstrated that the drilling performance with the rectangular and sinusoidal loads was promoted than the other types of load, and rate of penetration (ROP) increases with increasing of the amplitude of dynamic load, which could provide the theoretical guidance to the down-the-hole drilling tool design, thereby proving a quite efficient and lower cost drilling in the exploration of hard formations.