Linking continuum-scale state of wetting to pore-scale contact angles in porous media

Chenhao Sun; James E McClure; Peyman Mostaghimi; Anna L Herring; Mehdi Shabaninejad; Steffen Berg; Ryan T Armstrong

doi:10.1016/j.jcis.2019.11.105

Linking continuum-scale state of wetting to pore-scale contact angles in porous media

J Colloid Interface Sci. 2020 Mar 1:561:173-180. doi: 10.1016/j.jcis.2019.11.105. Epub 2019 Nov 30.

Authors

Chenhao Sun¹, James E McClure², Peyman Mostaghimi¹, Anna L Herring³, Mehdi Shabaninejad³, Steffen Berg⁴, Ryan T Armstrong⁵

Affiliations

¹ School of Minerals & Energy Resources Engineering, University of New South Wales, Kensington, NSW 2052, Australia.
² Advanced Research Computing, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA.
³ Department of Applied Mathematics, Australian National University, Canberra, ACT 2600, Australia.
⁴ Rock & Fluid Physics, Shell Global Solutions International B.V., Grasweg 31, 1031 HW Amsterdam, the Netherlands; Department of Earth Science & Engineering, Imperial College London, London SW7 2AZ, UK; Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
⁵ School of Minerals & Energy Resources Engineering, University of New South Wales, Kensington, NSW 2052, Australia. Electronic address: ryan.armstrong@unsw.edu.au.

PMID: 31812863
DOI: 10.1016/j.jcis.2019.11.105

Abstract

Hypothesis: Wetting phenomena play a key role in flows through porous media. Relative permeability and capillary pressure-saturation functions show a high sensitivity to wettability, which has different definitions at the continuum- and pore-scale. We hypothesize that the wetting state of a porous medium can be described in terms of topological arguments that constrain the morphological state of immiscible fluids, which provides a direct link between the continuum-scale metrics of wettability and pore-scale contact angles.

Experiments: We perform primary drainage and imbibition experiments on Bentheimer sandstone using air and brine. Topological properties, such as Euler characteristic and interfacial curvature are measured utilizing X-ray micro-computed tomography at irreducible air saturation. We also present measurements for the United States Bureau of Mines (USBM) index, capillary pressure and pore-scale contact angles. Additional studies are performed using two-phase Lattice Boltzmann simulations to test a wider range of wetting conditions.

Findings: We demonstrate that contact angle distributions for a porous multiphase system can be predicted within a few percent difference of directly measured pore-scale contact angles using the presented method. This provides a general framework on how continuum-scale data can be used to describe the geometrical state of fluids within porous media.

Keywords: Contact angle; Gauss-Bonnet theorem; Geometric state of fluids; Interfacial curvature; Multiphase flow; Porous media; Wettability.