A Coupled Geomechanical-Reservoir Model for the Modelling of Coal and Gas Outbursts

Abstract Coal mining under conditions of sufficiently high pore gas pressure can produce the hazard of dynamic failure of coal known as coal and gas outbursts. During an outburst, coal fragmentation occurs and the fragmented coal is projected into the mine opening, accompanied by a rapid release of gas. A dual porosity multi-component coalbed methane reservoir simulator has been coupled with a coupled geomechanical – fluid flow analysis code, to investigate gas outburst initiation and evolution during roadwaydevelopment. The model is three-dimensional and can take into account factors such as rate of mining (or face advance), mine geometry,magnitude and orientations of in-situ principal stresses, strength of coal, large deformation, reservoir pressure, mixed gases sorption properties of coal, stress dependent permeability and relative permeabilities for two-phase (gas and fluid) flow in afractured porous medium, and poroelastic effects. Reasonably good agreement between model predictions on outburst initiation and field data has been obtained. Some results on the modelling of the post-initiation deformation and fragmentation of the ejected coal are presented and discussed.