Hydrothermal Synthesis of γ‑Al₂O₃ Nanofluids for Enhanced Oil Recovery: Characterization and Coreflooding Evaluation

Nanoparticles are increasingly used in enhanced oil recovery (EOR) due to their resistance to harsh conditions and effective oil dispersion. Al₂O₃ nanoparticles, in particular, can reduce interfacial tension (IFT) and alter rock wettability, improving oil mobility. This study synthesized γ-Al₂O₃ nanoparticles via a low-temperature, short-duration hydrothermal method, prepared nanofluids, and evaluated their performance in medium-viscosity oil recovery. Nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), and BET surface area analysis. Nanofluids were prepared in saline solution at different concentrations and assessed for colloidal stability by UV-vis spectroscopy and sedimentation tests, along with rheological properties and interactions with rock and oil. EOR tests used Buff Berea sandstone plugs. XRD confirmed γ-Al₂O₃ formation without secondary phases. FTIR, FESEM, and BET analyses showed characteristic alumina bonds, uniform nanoplate morphology, and high specific surface area. The 0.01 wt % nanofluid remained stable for 2 h, while higher concentrations resulted in sedimentation and aggregation. Nanofluids exhibited Newtonian behavior with viscosity similar to water. IFT decreased as nanoparticle concentration increased; however, efficiency dropped at 0.10 wt % due to agglomeration. Wettability tests after 24 h indicated that 0.01 wt % reduced the contact angle to 64°, whereas 0.05 and 0.10 wt % fully reversed wettability (0°). In oil recovery, 0.10 wt % γ-Al₂O₃ nanofluid achieved the highest recovery (>29%) versus brine (26.31%). Appropriate nanoparticle concentration is essential to optimize recovery efficiency.