Poromechanics of Microporous Carbons: Application to Coal Swelling during Carbon Storage

International audienceCoal seams are naturally filled with natural gas. Enhanced Coal Bed Methane recovery (ECBM) is a technique which consists in injecting carbon dioxide (CO2) in coal seams in order to enhance the recovery of the methane (CH4) present in the coal seams. A major issue for the industrial development of this technique is the loss of permeability of the reservoirs during injection. In a coal bed, most of the transport of fluids occurs in a network of natural frac- tures. The loss of permeability is attributed to the closure of the fractures induced by the swelling of the coal ma- trix during the progressive replacement of CH4 by CO2. Since both fluids are mostly adsorbed in the microporous matrix of coal, this particular problem raises the funda- mental question of how adsorption impacts the mechanics of a microporous solid. In this work, we present a porome- chanical modeling valid for microporous solids under ad- sorption and we apply this modeling to the specific case of ECBM. The first section presents the theoretical derivation of general constitutive equations of poromechanics which are valid for generic pore sizes and morphologies. In the second section, we apply this general poromechanics to the specific case of CH4 adsorption in coal. We use molecu- lar simulations to calibrate the derived constitutive laws. In the third section we validate this calibration by analyz- ing results of adsorption experiments in unjacketed condi- tions. The fourth section is dedicated to the case of CO2 adsorption in coal. Finally in the last section, we use this modeling to predict the swelling of coal in the context of ECBM

Fracture Properties of Kerogen and Importance for Organic-Rich Shales

International audienceOil and gas produced from organic-rich shales have become in the last ten years one of the most promising sources of unconventional fossil fuels. The oil and gas are trapped in rocks of very small permeability, but hydraulic fracturing enables to operate those reservoirs with competitive costs. The global reserves of shale oil and gas that are potentially recoverable are equivalent to tens of years of world con- sumption. However, hydraulic fracturing is facing many challenges regarding the productivity but also the security and the environment. One of those challenges is to un- derstand how the fractures propagate underground. The propagation depends on the mechanical stress prevailing in the reservoir and on the fracture properties of the rocks. Regarding the fracture properties, the oil and gas indus- try developed brittleness indicators to distinguish between brittle rocks (containing mostly calcite and silica) and duc- tile rocks (containing a significant proportion of clay and kerogen). During fracturing, a brittle rock shatters easily leading to a well-distributed network of fractures, whereas a ductile rock deforms instead of shattering leading to few fractures and in some situations acting as a barrier to the fracture propagation. In this work, we study the role of kerogen in the ductility of shale. The ultimate objective is to develop a fine understanding of the fracture properties of shales

Engineering the bonding scheme in C-S-H: the iono-covalent framework

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An experimental and mesoscopic lattice simulation study of styrene-butadiene latex-cement composites properties

The consequences of styrene-butadiene rubber (SBR) latex addition on the hardness and structural properties of a cement matrix have been investigated. The results show that the primary effect of latex addition is the decrease in the so-called capillary porosity and a shift of the pore-size distribution towards the nanometer range. In spite of this, addition of latex significantly alters the hardness of the polymercement compound as compared to pure cement, due to the intrinsically smaller modulus of the polymer and the lack of strong interaction with cement phases. It is shown that the properties depend both on the Polymer/Cement (P/C) and Water/Cement (W/C) ratios. This study confirms that the butadiene-styrene copolymer is confined to the capillary porosity only and interacts but weakly with the different cement phases. In agreement with this, a simple mesoscopic lattice model, much inspired from Powers pioneering model for cement hydration, was shown to account for the porosity and composition dependence of hardness and modulus. A criterion for the activity of fillers is proposed