Scaled in-situ laboratory CH4 flushing experiments with CO2 are being carried out on coalin an experimental high P,T device, which is developed by The Delft University of Technology- Department of Applied Earth Sciences. To bridge the gap between laboratory and thefleld we need to develop a numerical model that can be used to interpret the laboratoryexperiments. Moreover the model must also be able to assist in the design of the injectionsystem, management, control of the operations and the effciency. Although the experiencegained by the oil industry represents a valuable starting point, several problems are stillto be studied and solved before CO2 improved deep coalbed methane production may beoperationally feasible. These are all related to the heterogeneous nature of the pore structureof coal, and in particular the presence of fractures. More speciflcally, a number of questionsneed to be addressed, e.g. What are the conditions under which the fluid in the micro poresof the coal is displaced by the CO2 in the presence of competitive adsorption; what is the roleof compositional heterogeneity and fracture anisotropy of coal for the injection design andthe effciency of the sequestration in relation to the swelling and shrinkage characteristics ofcoal. These questions can be answered by means of simulation models that are capable ofaccurately describing the coupled process of multiphase flow, competitive adsorption, andgeo-mechanics. This work describes the initial efforts for the construction of such a model.In the present study we consider the upscaled equations for transport and flow in the multi-porosity coal sample inclusive of multiphase flow and dissolution of CO2 and methane inwater. At depths up to 1500 meters, the temperature and pressure head are such that theinjected CO2 remains in supercritical conditions, and thus in a gas phase. Compressibilityand density of the gas follow the thermodynamic laws of the reservoir gases, which accountsfor non-ideal gas behaviour through the temperature and pressure dependent compressibilityfactor. It is assumed that the dissolution process occurs instantaneously following Henry'slaw. Using these assumptions a set of flow equations have been derived. These equations,which have only a few parameters, have been implemented in a preliminary flow simulatorand compared to the experimental results. Up to now, the results show that dewateringwill be an essential step for successful ICBM combined with a carbon dioxide sequestrationprocess.
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