| Autor: |
M. Vandamme, L. Brochard, O. Coussy, Kambiz Vafai |
| Rok vydání: |
2010 |
| Předmět: |
|
| Zdroj: |
AIP Conference Proceedings. |
| ISSN: |
0094-243X |
| DOI: |
10.1063/1.3453831 |
| Popis: |
An injection of carbon dioxide into a coal bed methane reservoir facilitates the recovery of methane, a process known as enhanced coal bed methane recovery (ECBM). The injected carbon dioxide can then remain stored for geological periods of time. Over the process carbon dioxide gets adsorbed at the surface of the coal pores, which causes the coal to swell. In confined conditions this swelling leads to a closure of the coal reservoir cleat (fracture) system. Since permeability in coal beds is mostly driven by this cleat system, CO2-induced swelling hinders further injection and impairs the economic viability of ECBM. In this work we provide a comprehensive framework to calculate the macroscopic strains induced by adsorption in a porous medium, starting from the molecular level. Using a thermodynamic approach we extend the realm of poromechanics to surface energy and surface stress. This approach enables to calculate the macroscopic strains induced by a change of surface stress at the interface between solid matrix and pore space. The calculations performed are valid for a general microstructure. The microstructural features are identified which govern the mechanical response of the porous medium to a change of surface stress. We then focus on how surface stress depends on adsorption. We employ molecular simulations to estimate adsorption isotherms in both micropores (below 2nm) and mesopores (above 2nm). A comparison of our molecular simulation results with experimental results of coal swelling shows that adsorption in micropores (below 2nm) plays a primordial role in the CO2-induced swelling of coal. The developed framework is here applied to the specific case of the swelling of CO2-injected coal although it is relevant to any problem in which adsorption in a porous medium causes strains. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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