A thermodynamically consistent characterization of wettability in porous media using high-resolution imaging.

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Title: A thermodynamically consistent characterization of wettability in porous media using high-resolution imaging.
Authors: Blunt, MJ
Lin, Q
Akai, T
Bijeljic, B
Item Type: Journal Article
Abstract: Conservation of energy is used to derive a thermodynamically-consistent contact angle, θt, when fluid phase 1 displaces phase 2 in a porous medium. Assuming no change in Helmholtz free energy between two local equilibrium states we find that Δa1scosθt=κϕΔS1+Δa12, where a is the interfacial area per unit volume, ϕ is the porosity, S is the saturation and κ the curvature of the fluid-fluid interface. The subscript s denotes the solid, and we consider changes, Δ, in saturation and area. With the advent of high-resolution time-resolved three-dimensional X-ray imaging, all the terms in this expression can be measured directly. We analyse imaging datasets for displacement of oil by water in a water-wet and a mixed-wet sandstone. For the water-wet sample, the curvature is positive and oil bulges into the brine with almost spherical interfaces. In the mixed-wet case, larger interfacial areas are found, as the oil resides in layers. The mean curvature is close to zero, but the interface tends to bulge into brine in one direction, while brine bulges into oil in the other. We compare θt with the values measured geometrically in situ on the pore-scale images, θg. The thermodynamic angle θt provides a robust and consistent characterization of wettability. For the water-wet case the calculated value of θt gives an accurate prediction of multiphase flow properties using pore-scale modelling.
Issue Date: 15-Sep-2019
Date of Acceptance: 6-May-2019
URI: http://hdl.handle.net/10044/1/71791
DOI: https://doi.org/10.1016/j.jcis.2019.05.026
Start Page: 59
End Page: 65
Journal / Book Title: J Colloid Interface Sci
Volume: 552
Copyright Statement: © 2019 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).⇑Corresponding author.E-mail address:m.blunt@imperial.ac.uk(M.J. Blunt).Journal of Colloid and Interface Science 552 (2019) 59–65Contents lists available atScienceDirectJournal of Colloid and Interface Sciencejournal homepage: www.elsevier.com/locate/jcis
Keywords: Contact angle
Imaging
Interfacial area
Minimal surfaces
Multiphase flow
Pore-scale
Porous media
Wettability
Contact angle
Imaging
Interfacial area
Minimal surfaces
Multiphase flow
Pore-scale
Porous media
Wettability
03 Chemical Sciences
09 Engineering
02 Physical Sciences
Chemical Physics
Publication Status: Published online
Conference Place: United States
Open Access location: https://doi.org/10.1016/j.jcis.2019.05.026
Online Publication Date: 2019-05-08
Appears in Collections:Earth Science and Engineering



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