Geological storage of CO2 in coal beds - From material to reservoir

One of the main issues encountered with CO2 storage in coal beds is the loss of permeability of the reservoir during the injection of carbon dioxide. Such a decrease of permeability originates from the closure of the cleat system in these reservoirs, which itself is a consequence of the swelling of the coal matrix during injection. In this study, we first perform a comparison of the numerical simulation based on the derived model, at the scale of a coal sample, with available permeability measurements of coal injected with carbon dioxide. The second objective of the paper is to capture the effect of the kinetics of transfer of fluid between cleats and coal matrix using the set of equations derived before. We then perform simulations at the scale of a Representative Elementary Volume, and we show that adsorption-induced variations of permeability depend significantly on the kinetics of transfer of fluid between cleats and coal matrix. At the scale of a reservoir, simulations of injection of carbone dioxide in a methane-free reservoir are performed. We discuss the effects of the kinetics of transfer of fluid between cleats and coal matrix on the rates of injection.