Research on the mechanism of gas extraction enhancement and gas flow patterns in coal seam hydraulic fracturing

In response to the challenge of precisely determining the effective extraction radius during gas drainage after hydraulic fracturing, this study employed PFC2D (Particle Flow Code Two Dimension) to perform a discrete element numerical simulation of coal hydraulic fracturing. The simulation revealed the fracture propagation characteristics as well as the variation pattern of coal porosity during hydraulic fracturing, and the results were validated by laboratory experiments. Furthermore, by effectively integrating PFC2D with COMSOL (Computer Solution), a novel numerical simulation optimization method for gas extraction was proposed. In this method, the fracture propagation and porosity variation results obtained from the PFC2D simulation were directly imported into COMSOL to accurately simulate the borehole gas extraction performance, thereby determining the effective influence range of hydraulic fracturing. This approach was compared with the gas extraction performance prior to fracturing, providing a basis for the design of gas extraction boreholes. Additionally, the method's effectiveness is validated through field experiments, and the findings offer valuable guidance for the optimized layout of gas extraction boreholes.