The study examines patterns of methane inflow into a degassing horizontal well that passes through a coal massif during its degassing process. The gas flow is formed due to the difference between the pressures in the massif and the pressure in the degassing system for gas extraction. A method to resolve the problem of methane filtration into an imperfect longwell (100m) passed through a homogeneous coal seam, where the supply contour cannot be isolated, has been proposed.
To estimate the total gas flow rate and the efficient well operation time, a numerical algorithm in ANSYS that merges two types of liquid flows, that is, the filtration through a porous medium and the free flow through a well, is used. The algorithm enables the simultaneous solution of these problems. Degassing wells are passed through the formation prior to clean-up operations to remove the maximum amount of methane, which reduces accident risks and ensures the occupational safety of miners, preventing environmental consequences.
In any case, changing the configuration of excavated spaces in the massif as a result of rock or coal extraction causes the change of its stress-strain state and, consequently, its porosity and permeability. The latter factor significantly determines the formation of mass transfer in the massif, e.g., including gas extraction into wells. Lava propagation and the respective destruction of the rock massif structure cause the methane desorption from the coal and the outflow of free methane from macropores and cracks in the coal.
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