Numerical Simulation of Fracture Propagation and Damage Evolution in Coal Seam Under Controlled High-Energy Shock Wave Fracturing

Reservoir stimulation is a critical technique for the efficient development of coalbed methane (CBM), playing a significant role in improving permeability. Controlled shock wave fracturing, as an emerging stimulation method, offers advantages such as safety and high energy utilization, making it a promising candidate for CBM reservoir enhancement. Due to the substantial potential of deep CBM reservoirs, conventional physical simulations and field experiments are limited in accurately analyzing the fracturing effects. Research on the fracture propagation and damage evolution of coal rock under the influence of different geological and engineering parameters is limited, hindering the determination of key operational parameters. In this study, a coupled mathematical model of solid mechanics and damage continuum mechanics is established using the finite element method, alongside a geometric model, to investigate fracture propagation characteristics under the influence of geological and engineering factors. The core contribution of this work is a systematic numerical analysis that clarifies the controlling effects of key parameters. The main conclusions are as follows: (1) a high stress contrast (≥6 MPa) favors fracture extension along the direction of the maximum principal stress while inhibiting the expansion of the damage area; (2) the increase in the orientation of natural fissures and the angle of horizontal stress inhibits the propagation of fractures and the growth of damage area; (3) engineering parameters exert a considerable effect on fracture propagation and multiple shock cycles (≥2 times) and high peak pressure (≥250 MPa) are conducive to fracture formation; and (4) a key distinguishing feature is the formation of radioactive fractures induced by high-energy shock waves, which are beneficial for enhancing communication between rock layers and natural fractures. Compared to hydraulic fracturing, the shock wave method achieves distinctly faster fracture extension in a shorter time, highlighting its unique advantage for improving coalbed permeability and porosity. This study extends the numerical simulation research on controlled shock waves in deep coal seams, elucidates the dynamic response of fracture propagation and damage evolution under the control of geological and engineering parameters, reveals the sensitivity of key parameters to fracture extension, and provides a critical basis for the selection and optimization of operational parameters in field applications of shock wave fracturing.