The Fragmentation Mechanism of Heterogeneous Granite by High-Voltage Electrical Pulses

The high-voltage electrical pulses (HVEP) technology is the most potential method to improve the rate of penetration (ROP) in deep hard formations. A detailed understanding of the fragmentation mechanism by HVEP is essential to enhance ROP in rock-breaking and to optimize the electrical parameters. However, few pieces of researches are focused on the uneven dielectric properties of rock. This paper uses particle flow code software and Voronoi tessellation to generate granite models with different heterogeneity indexes; the granite models consider the differences in the micro-dielectric properties and particle size of various mineral components. The simulation of the plasma channel growth process, which considers the circuit equations of HVEP and the probabilistic development model, is analyzed. The results show that the concentration of the electric field in the feasible region makes the extreme value of the entire electric field smaller, which puts forward a higher energy demand for the initial breakdown of granite. The finer the grain size of granite, the smaller the broken ratio coefficient, and the better the crushing degree of HVEP. There is almost no difference in the energy efficiency of HVEP between granites with different heterogeneity indexes. The total length of the plasma channel is dominated by “directional self-direction” and “priority of tips”, which is positively correlated with the energy efficiency of HVEP. The research results have definite guiding significance for engineering application of HVEP, bottom hole assembly design, and drilling tool design of HVEP.