Impact of interfacial tension on oil-water flow in a narrow gap

Numerous researchers have examined the co-current flow of oil-water and aqueous solutions containing polymers and surfactants in thin gaps for oil recovery. While some have focused on charges and forces at the interfaces of oil-surfactant solutions during flow. The study of flow structures, interface behavior, and relative permeabilities of oil and aqueous phases of surfactant flow through thin gaps has been less explored. For the first time, this research aims to comprehensively investigate the flow of oil-water and oil-surfactant solutions through a thin gap (Hele-Shaw cell) with a particular focus on the impact of sodium dodecyl sulfate (SDS). The experiments reveal that SDS forms an emulsion near the oil-water interface, capturing oil droplets and enabling their flow along with the SDS solution. Microscopic studies confirm this, showing that when SDS contacts oil, it creates channels through the oil phase, leading to the accumulation and division of oil into small round-shaped droplets, resulting in an oil-in-water emulsion. The addition of SDS to the injecting water significantly enhances relative permeabilities, leading to a remarkable 90% increase in oil recovery from the cell. The research suggests that the optimal SDS concentration range for maximum oil recovery is between 1.5 and 2 wt%, as it achieves the minimum interfacial tension between oil and water.