Enhancing coalbed methane extraction using high-voltage electric pulses: Dynamic evolution of plasma channels in coal

High-voltage electric pulse (HVEP) technology has recently emerged as a promising approach for enhancing coalbed methane (CBM) extraction while supporting environmentally sustainable energy development, owing to its high stimulation efficiency and minimal environmental impact. During the HVEP process, plasma channels (PCs) act as the primary carriers for thermal energy release and stress wave generation. A comprehensive understanding of their evolution mechanisms is essential for improving utilization efficiency of HVEP energy. However, the coupled relationship between PC evolution and electric field distribution remains insufficiently understood. To address this knowledge gap, a numerical model is developed to simulate the dynamic evolution of PCs in coal under HVEP discharge conditions, with particular emphasis on voltage-dependent morphological variations. The model incorporates two critical electrical parameters of coal: the threshold breakdown field intensity and the complete breakdown field intensities, whose values are determined experimentally for the tested coal specimens. Simulation results successfully reproduce the staged development of PCs and reveal the governing mechanisms of deterministic electric field-guided propagation and stochastic path evolution. Furthermore, by introducing quantitative morphological descriptors, including fractal dimension, channel length, and tortuosity, the effects of discharge voltage on PC morphology are systematically analyzed. The results provide new insights into the coupled evolution mechanisms of PCs and electric fields under HVEP loading and establish a theoretical foundation for optimizing discharge parameters and improving the effectiveness of HVEP-based CBM extraction.