Wettability in complex porous materials, the mixed-wet state, and its relationship to surface roughness
File(s)
Published version
Author(s)
AlRatrout, Ahmed
Blunt, Martin J
Bijeljic, Branko
Type
Journal Article
Abstract
A quantitative in situ characterization of the impact of surface roughness on wettability in porous media is currently lacking. We use reservoir condition micrometer-resolution X-ray tomography combined with automated methods for the measurement of contact angle, interfacial curvature, and surface roughness to examine fluid/fluid and fluid/solid interfaces inside a porous material. We study oil and water in the pore space of limestone from a giant producing oilfield, acquiring millions of measurements of curvature and contact angle on three millimeter-sized samples. We identify a distinct wetting state with a broad distribution of contact angle at the submillimeter scale with a mix of water-wet and water-repellent regions. Importantly, this state allows both fluid phases to flow simultaneously over a wide range of saturation. We establish that, in media that are largely water wet, the interfacial curvature does not depend on solid surface roughness, quantified as the local deviation from a plane. However, where there has been a significant wettability alteration, rougher surfaces are associated with lower contact angles and higher interfacial curvature. The variation of both contact angle and interfacial curvature increases with the local degree of roughness. We hypothesize that this mixed wettability may also be seen in biological systems to facilitate the simultaneous flow of water and gases; furthermore, wettability-altering agents could be used in both geological systems and material science to design a mixed-wetting state with optimal process performance.
Date Issued
2018-09-04
Date Acceptance
2018-07-17
Citation
Proceedings of the National Academy of Sciences of the United States of America, 2018, 115 (36), pp.8901-8906
ISSN
0027-8424
Publisher
National Academy of Sciences
Start Page
8901
End Page
8906
Journal / Book Title
Proceedings of the National Academy of Sciences of the United States of America
Volume
115
Issue
36
Copyright Statement
© 2018 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
Sponsor
Abu Dhabi Company for Onshore Petroleum Operations (ADCO)
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/30120127
PII: 1803734115
Grant Number
16312.01
Subjects
complex porous media
contact angle
curvature
in situ reservoir conditions
roughness
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2018-08-17