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Adsorption and capillary condensation in porous media as a function of the chemical potential of water in carbon dioxide
Author(s) -
Heath Jason E.,
Bryan Charles R.,
Matteo Edward N.,
Dewers Thomas A.,
Wang Yifeng,
Sallaberry Cédric J.
Publication year - 2014
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2013wr013728
Subject(s) - adsorption , capillary condensation , capillary action , porous medium , condensation , surface tension , saturation (graph theory) , chemistry , chemical engineering , porosity , materials science , thermodynamics , composite material , physics , mathematics , organic chemistry , combinatorics , engineering
The chemical potential of water may play an important role in adsorption and capillary condensation of water under multiphase conditions at geologic CO 2 storage sites. Injection of large volumes of anhydrous CO 2 will result in changing values of the chemical potential of water in the supercritical CO 2 phase. We hypothesize that the chemical potential will at first reflect the low concentration of dissolved water in the dry CO 2 . As formation water dissolves into and is transported by the CO 2 phase, the chemical potential of water will increase. We present a pore‐scale model of the CO 2 ‐water interface or menisci configuration based on the augmented Young‐Laplace equation, which combines adsorption on flat surfaces and capillary condensation in wedge‐shaped pores as a function of chemical potential of water. The results suggest that, at a given chemical potential for triangular and square pores, liquid water saturation will be less in the CO 2 ‐water system under potential CO 2 sequestration conditions relative to the air‐water vadose zone system. The difference derives from lower surface tension of the CO 2 ‐water system and thinner liquid water films, important at pore sizes <1 × 10 −6 m, relative to the air‐water system. Water movement due to capillary effects will likely be minimal in reservoir rocks, but still may be important in finer grained, clayey caprocks, where very small pores may retain water and draw water back into the system via adsorption and capillary condensation, if dry‐out and then rewetting were to occur.