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Geological storage of carbon dioxide in the coal seams : from material to the reservoir

Abstract : CO2 emissions into the atmosphere are recognized to have a significant effect on global warming. Geological storage of CO2 is widely regarded as an essential approach to reduce the impact of such emissions on the environment. Moreover, injecting carbon dioxide in coal bed methane reservoirs facilitates the recovery of the methane naturally present, a process known as enhanced coal bed methane recovery (ECBM). But the swelling of the coal matrix induced by the preferential adsorption by coal of carbon dioxide over the methane in place leads to a closure of the cleat system (a set of small natural fractures) of the reservoir and therefore to a loss of injectivity. This PhD thesis is dedicated to a study of how this injectivity evolves in presence of fluids. We derive two poromechanical dual-porosity models for a coal bed reservoir saturated by a pure fluid. The resulting constitutive equations enable to better understand and model the link between the injectivity of a coal seam and the adsorption-induced swelling of coal. For both models, the pore space of the reservoir is considered to be divided into the macroporous cleats and the pores of the coal matrix. The two models differ by how adsorption of fluid is taken into account: the first model is restricted to surface adsorption, while the second model can be applied for adsorption in a medium with a generic pore size distribution and thus in a microporous medium such as coal, in which adsorption mostly occurs by micropore filling. The latter model is calibrated on two coals with different sorption and swelling properties. We then perform simulations at various scales (Representative Elementary Volume, coal sample, coal seam). In particular, we validate our model on experimental data of adsorption-induced variations of permeability of coal. We also perform simulations of seams from which methane would be produced (CBM) or of methane-free seams into which CO2 would be injected. We study the effect of various parameters such as boundary conditions, compressibility of the coal matrix, or kinetics of transfer of fluid between cleats and coal matrix. In a final part, the derived model is extended to cases for which coal is in presence of fluid binary mixtures such as mixtures of methane and carbon dioxide. We fully calibrate this extended model on available data obtained experimentally and by molecular simulations. Calculations are then performed at the scale of a Representative Elementary Volume in order to predict how its porosity and its permeability vary in presence of fluid mixtures of methane and carbon dioxide
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https://pastel.archives-ouvertes.fr/pastel-00787962
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Submitted on : Wednesday, February 13, 2013 - 2:22:13 PM
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  • HAL Id : pastel-00787962, version 1

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Saeid Nikoosokhan. Geological storage of carbon dioxide in the coal seams : from material to the reservoir. Other. Université Paris-Est, 2012. English. ⟨NNT : 2012PEST1154⟩. ⟨pastel-00787962⟩

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