Numerical simulation of coal water driven gas evolution based on cavity throat network model
In order to explore the evolution law of water driven gas in the coal pore network under different temperature and water gas pressure states during the coal seam thermal injection process,a two-dimensional coal cavity throat network topology model based on fractal theory was established,and the equilibrium equation of water gas interface mechanics based on interface mechanics.On this ba-sis,numerical simulations of water driven gas under different temperature and pressure conditions were conducted.The research results indicate that during the process of coal water injection driven gas,as the water injection pressure increases,the water driven gas rate changes in an"S"shaped curve.Under the same pressure,the larger the fractal dimension of the pore throat,the smaller the proportion of water area,which means the lower the water driven gas rate.There is a drainage critical pressure in coal water driven gas,and both the drainage critical pressure and the drainage critical water driven gas rate increase with the increase of fractal dimension.After the completion of coal seam water injection and stable drainage,the number of residual gas domain connected groups first increases and then decreases with the decrease of residual gas rate.The average area of residual gas domain connected groups and the maximum area of gas domain connected groups both decrease with the decrease of residual gas rate.The number and maximum area of residual gas domain connected groups increase with the increase of fractal dimension,while the average area of residual gas domain connected groups decrea-ses with the increase of fractal dimension.
cavity throat networkcoalgaswater driven gasconnected group
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