Characterization and optimization of anionic surfactant-polyethylene glycol-alumina based nanofluids for enhanced oil recovery application

Abstract

Nanofluids have shown significant potential for enhanced oil recovery (EOR) through mechanisms such as wettability alteration, interfacial tension (IFT) reduction, and viscosity modification under dynamic shear conditions. This study characterizes and evaluates a nanofluid system comprising alumina (Al2O3) nanoparticles, sodium dodecyl sulfate (SDS) surfactant, and polyethylene glycol (PEG 1500) polymer for EOR applications. Structural analysis of Al2O3 nanoparticles using X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed spherical α-Al2O3 aggregates with a crystalline diameter of 20.28 nm. The dispersion of nanoparticles within the base fluid was confirmed by UV–Vis spectroscopy and dynamic light scattering (DLS), while thermogravimetric analysis (TGA) demonstrated thermal stability up to high temperatures in the presence of PEG 1500. Pendant drop tensiometry indicated a significant reduction in oil-aqueous IFT, with the nanofluid achieving values as low as 4 mN/m. Further IFT reduction was observed with the addition of PEG 1500 to the SDS-nanoparticle system, although excessive polymer concentration caused chain entanglements, leading to a slight increase in IFT. Sessile drop analyses on oil-saturated sandstone demonstrated dynamic contact angle reductions from 120° to approximately 40° over time, promoting a water-wet surface favorable for oil displacement. Rheological evaluations showed pseudoplastic behavior (flow index n < 1) under shear conditions typical of reservoirs, with viscosity values in the range of 2–13 cP. Core-flooding investigations revealed a marked enhanced in the tertiary oil recovery of surfactant-based nanofluids by nearly 8–10 % in the presence of Al2O3 nanoparticle/PE 1500 polymer. This ensures effective oil displacement at low shear rates and favorable injectivity at higher shear rates. This study highlights the efficacy of Al2O3 nanoparticles combined with SDS and low-molecular-weight PEG in optimizing injection fluid compositions. By enhancing fluid-rock interactions and improving oil recovery mechanisms, this work contributes to advancing nanotechnology applications in petroleum reservoirs. © 2025