Study on the influence of pre-injection blocking fluid on the pore and fracture structure of coal and its seepage law

Abstract

To study the influence of pre-injection blocking fluid on the pore and fracture structure of coal and its seepage law, CT three-dimensional reconstruction technology was used to characterize the coal structure. Using Comsol software to simulate the flow characteristics of the blocking fluid in the fractures of coal. At 200 °C, compared with the untreated coal, the specific surface area, pore volume, and connectivity of the treated coal show the most significant changes, reducing by 24.24 %, 32.87 %, and 7.04 %, respectively. When the injection pressure of the blocking liquid is 3.1 MPa, the overall flow velocity of the blocking liquid is relatively high, and the maximum flow velocity occurs at the larger pore size where the blocking liquid has fully developed, that is, at the cross-sectional position of 192 μm. Research has shown that changes in coal structure can affect the flow characteristics of the blocking fluid inside the coal. At 200 °C, the inhibitory ability of the blocking liquid on the pore and fracture structure and connectivity development of the coal sample is stronger, which can suppress the circulation of oxygen inside the coal sample and is more conducive to the prevention and control of coal spontaneous combustion fires. The research results provide valuable technical support for the evaluation of the fire prevention and extinguishing effects of pre-injection inhibitors and the optimization of technology.