Mechanisms of efficient three-dimensional fracture network construction in deep shale reservoirs via methane multistage explosive fracturing

Methane in situ multistage explosive fracturing (MISMEF) presents a promising technique for enhancing complex fracture networks in deep, low-permeability shale reservoirs. This study employed high-fidelity 3D simulations, integrating a characteristic methane–oxygen explosion load model with dynamic relaxation and full-restart methods, to elucidate the coupled interactions between explosive loading and in situ stress. A damage-based zoning approach was developed to quantify fracture characteristics, leading to the proposal of a novel dimensionless evaluation index, F mef . Results showed that in situ stress predominantly suppressed longitudinal fracture growth, while multistage loading effectively enhanced both lateral and longitudinal propagation following a "delayed initiation–accelerated propagation" pattern. Fracture volume exhibited nonlinear amplification with increasing stages, and the continuous increase in fractal dimension suggested improved network connectivity. Energy redistribution driven by the coupled effects of in situ stress and staged loading promoted complex network formation near the wellbore, with MISMEF progressively reducing fracture thresholds through rock mass weakening. F mef analysis confirmed significant improvement in fracture network quality across all stress conditions, particularly under medium to high in situ stress. This work provides critical mechanistic insights and a theoretical foundation for optimizing MISMEF in deep shale reservoir stimulation.