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Suppressing viscous fingering in structured porous media

Rabbani, Harris Sajjad ; Or, Dani ; Liu, Ying ; Lai, Ching-Yao ; Lu, Nancy B ; Datta, Sujit S ; Stone, Howard A ; Shokri, Nima

Proceedings of the National Academy of Sciences of the United States of America, 2018, Vol.115(19), p.4833-4838 [Peer Reviewed Journal]

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  • Title:
    Suppressing viscous fingering in structured porous media
  • Author/Creator: Rabbani, Harris Sajjad ; Or, Dani ; Liu, Ying ; Lai, Ching-Yao ; Lu, Nancy B ; Datta, Sujit S ; Stone, Howard A ; Shokri, Nima
  • Subjects: Physical Sciences ; Suppressed Viscous Fingering ; Structured Porous Media ; Microfluidics ; Direct Numerical Simulation ; Analytical Model
  • Is Part Of: Proceedings of the National Academy of Sciences of the United States of America, 2018, Vol.115(19), p.4833-4838
  • Description: Significance Viscous fingering commonly takes place during injection of one fluid that displaces a resident fluid in a porous medium. Fingering normally is promoted where the injected fluid is less viscous than the resident fluid being displaced. We propose a design of a porous medium in the form of an ordered structure to suppress or trigger (depending on the application) viscous fingering in porous media without modifying fluid properties or wettability. We utilize pore-scale direct numerical simulations, state-of-art experiments and analysis to derive predictive tools to evaluate effects of various parameters on controlling viscous fingering in porous media. Moreover, we propose generalized analytical solutions and a phase diagram for the parameter space affecting viscous fingering patterns. Finger-like protrusions that form along fluid−fluid displacement fronts in porous media are often excited by hydrodynamic instability when low-viscosity fluids displace high-viscosity resident fluids. Such interfacial instabilities are undesirable in many natural and engineered displacement processes. We report a phenomenon whereby gradual and monotonic variation of pore sizes along the front path suppresses viscous fingering during immiscible displacement, that seemingly contradicts conventional expectation of enhanced instability with pore size variability. Experiments and pore-scale numerical simulations were combined with an analytical model for the characteristics of displacement front morphology as a function of the pore size gradient. Our results suggest that the gradual reduction of pore sizes act to restrain viscous fingering for a predictable range of flow conditions (as anticipated by gradient percolation theory). The study provides insights into ways for suppressing unwanted interfacial instabilities in porous media, and provides design principles for new engineered porous media such as exchange columns, fabric, paper, and membranes with respect to their desired immiscible displacement behavior.
  • Identifier: ISSN: 0027-8424 ; E-ISSN: 1091-6490 ; DOI: 10.1073/pnas.1800729115 ; PMCID: 5948996 ; PMID: 29686067