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

Laurent Brochard (1, 2) , Matthieu Vandamme (1) , R.J.M. Pellenq (2, 3) , Teddy Fen-Chong (1)

1 navier umr 8205 - Laboratoire Navier
2 CEE - Department of Civil and Environmental Engineering [Cambridge]
3 CINaM - Centre Interdisciplinaire de Nanoscience de Marseille

Coal 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.

Domaines: Mécanique des matériaux [physics.class-ph]

Laurent Brochard, Matthieu Vandamme, R.J.M. Pellenq, Teddy Fen-Chong. Poromechanics of Microporous Carbons: Application to Coal Swelling during Carbon Storage. Annual world conference on Carbon (Carbon 2012), Jun 2012, Krakow, Poland. ⟨hal-01274150⟩