Silica Nanoparticle-Stabilized Anionic Surfactant Microemulsions: Characterization, Technical Evaluation, and Core-Flooding Studies for Enhanced Oil Recovery

Microemulsions encompass a viable injection fluid candidate in enhanced oil recovery (EOR) due to their exceptional ability to extract residual oil from natural oil reservoirs via several mechanistic approaches. However, challenges exist in the field during the interface–rheology relationship, fluid handling, and limitations in terms of microemulsion composition. In the present paper, the favorability of a novel, cost-effective microemulsion stabilized by an olefin sulfonate surfactant (ENORDET) and/or silica nanoparticles has been investigated intricately for application in EOR. The critical micelle concentration of the surfactant was identified by surface tensiometry using the du Noüy ring technique. Microemulsions with suitable ENORDET concentration(s) were prepared via a high-energy technique and characterized by turbidity analysis. Droplet distribution/stability was analyzed by dynamic light scattering and zeta potential studies. The microemulsion initially exhibited Winsor I behavior, which transitioned to the Winsor III phase and then to Winsor II (with gradually increasing salt concentration). Pendant drop analyses revealed a significantly low interfacial tension at the oil–microemulsion interface in comparison to water (as injection fluid). Sessile drop analyses predicted the alteration of oil-saturated rock to a strongly water-wet state with an elapse of time. Though oil displacement experiments revealed favorable recovery factors for both surfactant and surfactant–nanoparticle microemulsions, the presence of nanoparticles exhibited enhanced flooding performance in the sandstone (core) model. Core-flood studies showed ∼20% and ∼29% recovery of original oil in place (OOIP) for ENORDET microemulsion and {ENORDET + SiO2} microemulsion respectively, after secondary water flooding. The novelty of the research lies in the development of a microemulsion system stabilized by a novel olefin sulfonate surfactant with unique molecular properties and cost-effective silica nanoparticles for a sustainable EOR implementation. In summary, the research includes extensive laboratory testing and mechanistic analyses, which are strong evidence of the formulation's effectiveness and practical applicability in EOR.