Mathematical model and dimensionless numerical simulation of methane flow in a dual-porosity and dual-permeability coal seam
QIN Yueping1,LIU Peng1,HAO Yongjiang2
(1. College of Resource and Safety Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;
2. College of Environment and Safety,Taiyuan University of Science and Technology,Taiyuan,Shanxi 030024,China)
Abstract:Considering the three stages of methane flow in coalseam including desorption,migration and seepage,Darcy?s law was employed to describe gas migration in coal matrix and fracture,and the gas mass transfer flux between coal matrix and fracture was served as a coupling term to develop a mathematical model of methane flow in a dual-porosity,dual-permeability coal seam and its dimensionless model. The finite difference method was applied to develop a numerical solution for the model. The numerical results show that the decline rate of gas pressure and content in fracture is much faster than that in coal matrix. The gas pressure distribution and gas content in coal matrix are heterogeneous and unsteady over time. A higher permeability of fracture,a higher original gas pressure in coal,or a lower gas pressure outside coal wall,lead to a higher gas emission rate. The dual-porosity and dual-permeability model for methane flow in coal seam is validated to be correct by comparing the simulated results and the field data from Panyi mine.
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