The Role of Interfacial Tension in Nanobubble-Enhanced Oil Recovery

Aqueous nanobubble solutions (NBs) are emerging as promising enhanced oil recovery (EOR)agents due to their ability to improve oil displacement efficiency in geosystem applications. Unliketraditional EOR methods, which typically rely on chemical additives or complex gas formulations, NBsgenerated from accessible gases such as nitrogen offer a viable alternative. In this study, we examine therole of interfacial tension (IFT) in the displacement of different oils from porous media by NBs. To this end,we utilized mineral and crude oils with varying IFT with water to perform a series of elevated-pressuremicromodel flooding experiments using NBs in a strongly oil-wet porous medium, whereas distilled water(DW) tests served as controls. NBs were prepared through a high-pressure generation system that combinesmembrane dispersion with microfluidic flow. IFT between each oil and both DW or NBs was measured toevaluate interfacial effects. Results show that NBs consistently enhanced sweep efficiency compared to DW,characterized by more uniform front propagation and reduced bypassed oil. This improvement was mostpronounced in oils with higher IFT with water. The improved oil displacement by NBs is attributed to thereduction in oil-water IFT by NBs, which lowers the capillary forces and aids in the effective mobilizationof oil.