Abstract：Gas adsorption/desorption may influence the coal permeability after injection of CO2 or CO2/N2 mixture into unminable coalbed for enhanced coalbed methane recovery and CO2 sequestration. The laboratory experiments under constant effective stress and different gas pressures are conducted by means of self-developed triaxial gas-seepage experimental device；and the change law of permeability of coal samples under gas pressure and adsorption is discussed. The results show as follows：(1) The permeability decreases as negative exponent with the increase in gas pressure under fixed injected gas composition conditions. (2) The change in permeability of coal samples is a function of the injected gas composition. At the same pore pressure，the permeabilities of coal samples decrease after gas adsorption. The permeability reduction is the greatest for pure CO2 followed by CH4 and N2. When injecting CO2 and N2 mixtures，as the concentration of CO2 in the injected gas increases，the permeability of the coal decreases. However，as the N2 reaches a certain proportion，the permeability of coal samples will be improved. (3) The relation curves of permeability and gas pressure in loading-unloading process of gas pressure have the hysteresis phenomenon，which may be related to the gas adsorption/desorption hysteresis phenomenon in coal. Therefore，the permeability of coal is in relation to pressure path. The results have important significance for prediction and control of reservoir permeability in the process of CO2 or flue gas injection into unminable coalbed to enhance gas recovery and CO2 sequestration.
TENNILLE E M，ANDRZEJ P R，TIM A M，et al. Assessing the potential for CO2 adsorption in a subbituminous coal，Huntly Coalfield，New Zealand，using small angle scattering techniques[J]. International Journal of Coal Geology，2009，77(1/2)：54-68.
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2010, Vol. 29 
