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Automatic measurement of contact angle in pore-space images

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Title: Automatic measurement of contact angle in pore-space images
Authors: AlRatrout, A
Raeini, AQ
Bijeljic, B
Blunt, MJ
Item Type: Journal Article
Abstract: A new approach is presented to measure the in-situ contact angle (θ) between immiscible fluids, applied to segmented pore-scale X-ray images. We first identify and mesh the fluid/fluid and fluid/solid interfaces. A Gaussian smoothing is applied to this mesh to eliminate artifacts associated with the voxelized nature of the image, while preserving large-scale features of the rock surface. Then, for the fluid/fluid interface we apply an additional smoothing and adjustment of the mesh to impose a constant curvature. We then track the three-phase contact line, and the two vectors that have a direction perpendicular to both surfaces: the contact angle is found from the dot product of these vectors where they meet at the contact line. This calculation can be applied at every point on the mesh at the contact line. We automatically generate contact angle values representing each invaded pore-element in the image with high accuracy. To validate the approach, we first study synthetic three-dimensional images of a spherical droplet of oil residing on a tilted flat solid surface surrounded by brine and show that our results are accurate to within 3° if the sphere diameter is 2 or more voxels. We then apply this method to oil/brine systems imaged at ambient temperature and reservoir pressure (10MPa) using X-ray microtomography (Singh et al., 2016). We analyse an image volume of diameter approximately 4.6  mm and 10.7  mm long, obtaining hundreds of thousands of values from a dataset with around 700 million voxels. We show that in a system of altered wettability, contact angles both less than and greater than 90° can be observed. This work provides a rapid method to provide an accurate characterization of pore-scale wettability, which is important for the design and assessment of hydrocarbon recovery and carbon dioxide storage.
Issue Date: 27-Jul-2017
Date of Acceptance: 26-Jul-2017
URI: http://hdl.handle.net/10044/1/54921
DOI: https://dx.doi.org/10.1016/j.advwatres.2017.07.018
ISSN: 0309-1708
Publisher: Elsevier
Start Page: 158
End Page: 169
Journal / Book Title: Advances in Water Resources
Volume: 109
Copyright Statement: © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license. (http://creativecommons.org/licenses/by/4.0/)
Sponsor/Funder: Abu Dhabi Company for Onshore Petroleum Operations (ADCO)
Funder's Grant Number: 16312.01
Keywords: Science & Technology
Physical Sciences
Water Resources
WETTABILITY LITERATURE SURVEY
POROUS-MEDIA
2-PHASE FLOW
RECOVERY
ROCK
0905 Civil Engineering
0907 Environmental Engineering
Environmental Engineering
Publication Status: Published
Appears in Collections:Faculty of Engineering
Earth Science and Engineering



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