CO2 environments under extreme mineral confinement: Simulation challenges, molecular-based insights, and implications on macroscopic modeling
Abstract
We address key issues regarding the behavior at CO2 environments under extreme silica confinement, which become of high relevance to the understanding of the process of geological storage of CO2, including (a) how the nature of the surface affects the mineral-fluid interfacial structure and the thermodynamic response functions (b) how the overlapping of mineral-fluid interfaces affects the partition of species between confinement and bulk, (c) how CO2 contaminants compete for preferential adsorption and affect the composition of the interfacial layers, and (d) how the presence of mineral stress might alter the interfacial/confinement phenomena. The effort comprises extensive isobaric-isothermal/grand-canonical molecular dynamics simulations of CO2 + contaminant systems based on optimized force-field parameterization 1-2. Based on this study we illustrate how the interplay between different types of fluid-surface interactions and extreme fluid confinement, i.e., strong overlapping of interfacial structures, can induce unexpected behavior such as (i) the significant reduction of the isothermal compressibility and isobaric thermal expansivity of confined CO2-rich phases relative to the corresponding bulk counterparts 2, (ii) drying out of the pore environment whose immediate consequence is a significant enhancement of the pore CO2 concentration relative to that of the corresponding bulk environment 3, and (iii) the significant effect of surface and fluid polarity on determining the preferential adsorption and resulting species partition. Finally, we discuss some macroscopic implications of our findings, including a novel route to define the mean density of confined fluids without requiring the estimation of the confined volume, and the inadequacy of temperature/average-density corresponding state modeling for the description of the behavior of confined fluids 3. (1) Vlcek, L.; Chialvo, A. A.; Cole, D. R. JCP B 2011, 115, 8775. (2) Chialvo, A. A.; Vlcek, L.; Cole, D. R. RiMG 2013, 77, Chap. 11. (3) Chialvo, A. A.; Vlcek, L.; Cole, D. R. JCP C 2012, 116, 13904. This work was supported as part of the 'Center for Nanoscale Control of Geologic CO2', an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.V41A2744C
- Keywords:
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- 0545 COMPUTATIONAL GEOPHYSICS Modeling