A computational model for pore-scale flow regime tuning with thermally responsive surfactants

Recent experiments with temperature-sensitive surfactants have demonstrated the ability to reversibly toggle the wettability of an oil-water system. This novel curvature switching mechanism changes the direction of capillary pressure and as a result influence pore scale transport. This mechanism has the potential for active control of porous media transport mechanics. To that effect, a dynamic pore network model is developed to couple multiphase flow with thermal transport. The model accounts for temperature-sensitive surfactant-driven curvature switching and explores its impact on flow regimes, wettability, and interfacial tension. Simulations were conducted where a hydrophobic oil saturated porous network was injected with water (with and without surfactants). Initial simulations without surfactants or thermal effects show that higher injection rates favor viscous fingering, while lower rates promote capillary fingering. Isothermal surfactant flooding reduces capillary forces by altering both surface tension and contact angle. This partially stabilizes the invasion front and increases network saturation by up to 30% for unfavorable mobility ratios ( M < 1 ) at low injection rates. However, at higher injection rates, isothermal surfactants become less effective, and the viscous fingering regime remains largely unchanged. We report that using temperature-sensitive surfactant flooding, the flow pattern could be successfully altered. An otherwise viscous fingering regime could be converted to stable displacement under moderate heat loads ( Q t = 0 . 05 W ), leading to a 31.2% increase in network saturation. However, excessive heating ( Q t = 0 . 1 W ) reintroduces fingering near the inlet due to elevated capillary pressures. These results demonstrate that heat rates influence the pore scale displacement, allowing for programmable switching between viscous fingering to stable displacement for appropriate temperature-sensitive surfactants. This study highlights the potential of temperature-sensitive surfactants to optimize multiphase transport in porous materials, offering insights for applications in enhanced oil recovery, microfluidics, and beyond. • Injection rate, and contact angle critically influence invasion patterns, and phase saturation in porous media. • Isothermal surfactants improve the network saturation at low flow rates through wettability alteration, but fail at high rates. • Temperature-sensitive surfactants actively control regimes at high flow rates, transitioning from viscous fingering to stable displacement.