Interplay of viscosity and wettability controls fluid displacement in porous media

Saideep Pavuluri, Ran Holtzman, Luqman Kazeem, Malyah Mohammed, Thomas Daniel Seers, Harris Sajjad Rabbani

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Direct numerical simulations are used to elucidate the interplay of wettability and fluid viscosities on immiscible fluid displacements in a heterogeneous porous medium. We classify the flow regimes based using qualitative and quantitative analysis into viscous fingering (low M), compact displacement (high M), and an intermediate transition regime (M ≈ 1). We use stability analysis to obtain theoretical phase boundaries between these regimes, which agree well with our analyses. At the macroscopic (sample) scale, we find that wettability strongly controls the threshold M (at which the regimes change). At the pore scale, wettability alters the dominant pore-filling mechanism. At very small M (viscous fingering regime), smaller pore spaces are preferentially invaded during imbibition, with flow of films of invading fluid along the pore walls. In contrast, during drainage, bursts result in filling of pores irrespective of their size. As M increases, the effect of wettability decreases as cooperative filling becomes the dominant mechanism regardless of wettability. This suggest that for imbibition at a given contact angle, decreasing M is associated with change in effective wetting from neutral-wet (cooperative filling) to strong-wet (film flow).
Original languageEnglish
Article number094002
Number of pages15
JournalPhysical Review Fluids
Issue number9
Early online date6 Sept 2023
Publication statusPublished - Sept 2023

Bibliographical note

Published by the American Physical Society under the terms of the Creative
Commons Attribution 4.0 International license.

This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (,
which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly cited.


  • Multiphase flow
  • Displacement patterns
  • Direct Numerical Simulations
  • Viscosity ratio
  • Wettability


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