Effect of sorption induced swelling on gas transport in coal

In this study, an investigation of carbon dioxide sorption induced coal swelling and its effects on gas transport in coal is shown. The model presented is based on an existing coupled thermal, hydraulic, chemical and mechanical (THCM) model. A series of numerical simulations dealing with high pressure carbon dioxide injection in coal sample is presented. In particular, the effect of carbon dioxide sorption induced swelling on permeability evolution and gas breakthrough is investigated. Different cases are considered accounting for the difference in coal seam properties and its sorption characteristics. Under the conditions considered, it is demonstrated that the permeability response of coal to gas is affected by the carbon dioxide sorption induced volumetric strain. The results suggest that medium and high porous coals that swell gradually over the range of pressures considered in this work would lose a smaller portion of injectivity during gas injection, compared to low porous coals that swell significantly at low pressures, allowing quick breakthrough of gas through the domain