The Mathematical Model and Numerical Simulation of High Pressure Air Replacement Coal Seam Gas

摘要

The high pressure air replaces seam gas is one of effective methods to prevent coal and gas outburst. The paper studied the seam gas flow theory and mathematical model of multi-physics system which coupled the coal deformation, and also worked out the dynamic Mathematical Model both in the pore system and in the fracture system. The coupled models were implemented in the COMSOL Multi-physics, in which the high pressure air injected process was simulated ,and the following conclusions was gained :The injection rate of high pressure air was directly decided by the fracture development, the more a mount of fractures in the coal seams, the higher of the initial coal permeability, and gas transportation in them would be much easier; The gas seepage speed in the fracture system had directionality: The gas seepage speed of fracture system in the horizontal direction is faster than that in the vertical direction; the fracture system plays a more important role in the coal permeability than the role of pore system.