Dual role of surfactant-producing reaction in immiscible viscous fingering evolution

Abstract

An experimental study on immiscible viscous fingering (VF) with chemical reaction is described, whereby a surfactant produced in a radial Hele-Shaw cell results in a decrease in interfacial tension. The surfactant is formed at the interface between alkaline solution (sodium hydroxide) and a long-chain fatty acid (linoleic acid). This topic is closely related to alkaline flooding, which is an enhanced oil recovery method. The reaction was found to have two opposing effects on VF depending on the flow rate, namely, narrowing and widening of the fingers. Moreover, the influences of the reaction on VF evolution can be categorized into five different types based on the effects appearing in VF evolution and the fingering width and area at the maximum observation region. Possible mechanisms for each type are proposed, and an argument based on scaling of the VF properties using dimensionless numbers gives support to the proposed mechanisms. This dual role of the reaction in immiscible VF evolution may contribute to establishing optimal conditions for alkaline flooding. Moreover, the finding that one chemical reaction has two opposing effects on flow is of value from the standpoint of fundamental studies of reacting flow dynamics.

Chemo-Hydrodynamic Patterns and Instabilities

“…This instability has been thoroughly studied both experimentally and theoretically because, among others, of its ubiquity in oil recovery when a fluid like water or CO2 displaces the more viscous oil in the soils (Saffman & Taylor (1958), Homsy (1987)). In this context, reactions producing for instance surfactants in situ can modify the local surface tension and affect the Safmann-Taylor instability between two immiscible fluids (Jahoda & Hornof (2000), Nasr-El-Din et al (1990), Hornof & Baig (1995), Fernandez & Homsy (2003), Niroobakhsh et al (2017), Tsuzuki et al (2019)). We won't review this particular case as we focus here on miscible systems.…”

Unpredictable Dynamics of Polymeric Reacting Flow by Comparison between Pre- and Post-Reaction Fluid Properties: Hydrodynamics Involving Molecular Diagnosis via ATR–FTIR Spectroscopy

“…Reacting flows, wherein chemical reactions occur in flowing fluid, are ubiquitous phenomena appearing across the industrial, environmental, and biological fields . Thus far, numerous experimental and theoretical reacting flow studies have been performed on the chemical reaction-induced modification of flow dynamics in the liquid phase via changes in density, − viscosity, − interfacial tension, − and viscoelasticity. − These fluid property changes are generally evaluated by comparison between the observed properties before and after the reaction. In other words, if a fluid property such as the viscosity of the solution is higher after the reaction than before, we would expect that an increase in viscosity occurs from the reaction during flow.…”

Tunable Hydrodynamic Interfacial Instability by Controlling a Thermodynamic Parameter of Liquid–Liquid Phase Separation

“…Using the physicochemical properties measured, we determined the critical wavelength, λ c , that destabilizes an initially circular interface with the linear stability analysis, which was derived by Paterson . In this study, the linear stability analysis shows that , where Ca ′(= η q /γ b 2 ) is the capillary number, q is the injection flow rate, b is the gap between the cells, and r is the distance between the injection point and interface. This theoretical value is based on conditions that ignore the viscosity of the displacing liquid, and the actual critical wavelength is 2–3 times this theoretical value when the viscosity of the less viscous fluid is similar to that of water .…”