Study on gas migration blocking mechanism in near hydraulic fracturing hole area

Hydraulic fracturing technology often exhibits a stagnation phenomenon in the near-field zone of fracturing boreholes, characterized by a temporary "depression" or sluggish growth in gas extraction concentration and flow rate. To reveal the underlying mechanism of this phenomenon, this paper establishes a coupled model based on fluid-solid interaction theory, considering gas-water two-phase flow and coal-rock deformation. Using COMSOL Multiphysics software to numerically simulate gas migration processes in the near-hole region. Results indicate that gas migration stagnation is primarily governed by two mechanisms: First, the “gas-water two-phase flow competition mechanism,” where fracturing fluid intrusion induces competition between gas and liquid phases within fracture-pore media, leading to localized water lock and gas phase retention. Second, the “effective stress rebound and fracture closure effect,” wherein post-fracturing stress redistribution in coal causes fracture closure, resulting in reduced permeability. The simulation results reproduce the three-zone distribution pattern of gas migration (“blocked zone–competitive zone–intact zone”) and demonstrate good consistency with physical experimental data.