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Application of unsupervised deep learning to image segmentation and in-situ contact angle measurements in a CO2-water-rock system

Publication ,  Journal Article
Wang, H; Dalton, L; Guo, R; McClure, J; Crandall, D; Chen, C
Published in: Advances in Water Resources
March 1, 2023

Rock surface wettability is a critical property that regulates multiphase flows in porous media, which can be quantified using the surface contact angle (CA). X-ray micro-computed tomography (μCT) provides an effective approach to in-situ measurements of surface CAs. However, the CA measurement accuracy depends significantly on the quality of CT image segmentation, which is the clustering of CT pixels into separate phases. Inspired by this, we developed a deep learning (DL)-based CA measurement workflow. Motivated by the recent tremendous progress in unsupervised learning techniques and aiming to avoid expensive manual data annotations, an unsupervised DL pipeline for CT image segmentation was proposed and implemented, which includes unsupervised model training and post-processing. The unsupervised model training was driven by a novel loss function constrained with feature similarity and spatial continuity and implemented by iterative forward and backward paths; the former clustered the pixel-wise feature vectors extracted by convolution neural networks, whereas the latter updated the parameters using gradient descent. An over-segmentation strategy was adopted for model training. The post-processing steps based on agglomerative hierarchical clustering (AHC) were implemented to further merge the over-segmented model output to the desired cluster number, which is intended to improve the efficiency of image segmentation. The developed unsupervised DL pipeline was compared with other commonly-used image segmentation methods using pixel-wise and physics-based evaluation metrics on a synthetic raw-image dataset, which had a known ground truth. The unsupervised DL pipeline showed the best performance. Next, the segmented images were input to an automatic CA measurement tool, and the results were validated by comparisons with manual measurements. The CA values from the manual and automatic measurements showed similar distributions and statistical properties. The automatic measurement demonstrated a wider spectrum because of the much larger number of measurement data points. The primary novelty of the unsupervised DL pipeline developed in this study lies in the novel loss function and the over-segmentation strategy associated with AHC post-processing. The workflow has been proven an efficient tool for pore-scale wettability characterization, which has a wide range of applications in fundamental studies of multiphase flows in natural porous media, which have critical implications to geological carbon sequestration, hydrocarbon energy recovery, and contaminant transport in groundwater.

Duke Scholars

Published In

Advances in Water Resources

DOI

ISSN

0309-1708

Publication Date

March 1, 2023

Volume

173

Related Subject Headings

  • Environmental Engineering
  • 4901 Applied mathematics
  • 4005 Civil engineering
  • 3707 Hydrology
  • 0907 Environmental Engineering
  • 0905 Civil Engineering
  • 0102 Applied Mathematics
 

Citation

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Wang, H., Dalton, L., Guo, R., McClure, J., Crandall, D., & Chen, C. (2023). Application of unsupervised deep learning to image segmentation and in-situ contact angle measurements in a CO2-water-rock system. Advances in Water Resources, 173. https://doi.org/10.1016/j.advwatres.2023.104385
Wang, H., L. Dalton, R. Guo, J. McClure, D. Crandall, and C. Chen. “Application of unsupervised deep learning to image segmentation and in-situ contact angle measurements in a CO2-water-rock system.” Advances in Water Resources 173 (March 1, 2023). https://doi.org/10.1016/j.advwatres.2023.104385.
Wang H, Dalton L, Guo R, McClure J, Crandall D, Chen C. Application of unsupervised deep learning to image segmentation and in-situ contact angle measurements in a CO2-water-rock system. Advances in Water Resources. 2023 Mar 1;173.
Wang, H., et al. “Application of unsupervised deep learning to image segmentation and in-situ contact angle measurements in a CO2-water-rock system.” Advances in Water Resources, vol. 173, Mar. 2023. Scopus, doi:10.1016/j.advwatres.2023.104385.
Wang H, Dalton L, Guo R, McClure J, Crandall D, Chen C. Application of unsupervised deep learning to image segmentation and in-situ contact angle measurements in a CO2-water-rock system. Advances in Water Resources. 2023 Mar 1;173.
Journal cover image

Published In

Advances in Water Resources

DOI

ISSN

0309-1708

Publication Date

March 1, 2023

Volume

173

Related Subject Headings

  • Environmental Engineering
  • 4901 Applied mathematics
  • 4005 Civil engineering
  • 3707 Hydrology
  • 0907 Environmental Engineering
  • 0905 Civil Engineering
  • 0102 Applied Mathematics