Research Article
Impact of Pore-Scale Characteristics on Immiscible
Fluid Displacement
Nariman Mahabadi,
1
Leon van Paassen,
2
Ilenia Battiato,
3
Tae Sup Yun,
4
Hyunwook Choo,
5
and Jaewon Jang
6
1
Department of Civil Engineering, University of Akron, Akron, Ohio, USA
2
School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona, USA
3
Department of Energy Resources Engineering, Stanford University, Stanford, California, USA
4
Department of Civil and Environmental Engineering, Yonsei University, Seoul, Republic of Korea
5
Department of Civil Engineering, Kyung Hee University, Yongin, Republic of Korea
6
Department of Civil and Environmental Engineering, Hanyang University, Seoul, Republic of Korea
Correspondence should be addressed to Jaewon Jang; jwj@hanyang.ac.kr
Received 9 January 2020; Accepted 2 May 2020; Published 15 May 2020
Academic Editor:
Reza Rezaee
Copyright © 2020 Nariman Mahabadi et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
Immiscible fluid flows (drainage displacement) where nonwetting fluid invades porous media filled with wetting fluid are
frequently observed. Numerous studies have confirmed the existence of three diff erent displacement patterns which depend on
the viscosity ratio and capillary number: stable displacement, viscous fingering, and capillary fingering. However, the phase
boundary and displacement efficiency of each displacement pattern can vary significantly depending on the characteristics of the
experimental and numerical tools employed. In this study, a three-dimensional (3D) tube network model was extracted from 3D
X-ray computed tomography images of natural sand. The extracted network model was used to quantitatively outline the phase
boundary of the displacement pattern and to examine the displacement efficiency for wide ranges of viscosity ratios and
capillary numbers. Moreover, the effects of the tube size distribution and tube connectivity on the displacement characteristics
were investigated. A transition regime between the viscous fingering and capillary fingering zones with regard to the
displacement efficiency was observed for the first time. As the tube size distribution became uniform, the viscosity effect
increased. As the tube connectivity decreased to ~4.6, the phase boundary became similar to that of a two-dimensional network.
The characteristic changes of the phase boundary and displacement efficiency were highlighted through local gradient diagrams.
1. Introduction
Immiscible fluid flow is frequently observed in various engi-
neering applications, such as enhanced oil and gas recovery,
geological CO
2
sequestration, and soil remediation. While
the invading fl uid is injected into porous media through an
injection well, the defending fluid in the pore space is dis-
placed until the invading fluid reaches a drainage well. Con-
sequently, multiple preferential flow channels are formed.
When a nonwetting invading fluid displaces a wetting
defending fluid, called drainage displacement, the pattern of
fluid invasion and displacement depends on several parame-
ters, such as the viscosity ratio, interfacial tension, injection
rate, and wettability, as well as the characteristics of the
porous media [1].
The viscosity ratio M is defined as the ratio of the viscos-
ity of the invading fluid (μ
inv
) to that of the defending fluid
(μ
def
). The capillary number C is defined as the ratio of the
viscous force to the capillary force:
Viscosity ratio : M =
μ
inv
μ
def
,
ð1Þ
Capillary number : C =
qμ
inv
AT
s
cos θ
:
ð2Þ
Hindawi
Geofluids
Volume 2020, Article ID 5759023, 10 pages
https://doi.org/10.1155/2020/5759023