Yousef Kazemzadeh

Colloidal Gas Aphrons (CGAs) are a next-generation intelligent fluid system in petroleum engineering with certain merits, such as improved interfacial tension (IFT) lowering, improved sweep efficiency, and increased stability, particularly under high-salinity conditions. However, their performance with mineral salts and solid additives is yet to be well established. In this work, we investigate in detail the synergistic effect of three cationic salts KCl, NaCl, and MgCl₂ at two salinity concentrations (5000 and 50000 ppm), constant concentration of cationic surfactant CTAB (300 ppm) and xanthan polymer (6.86 g/L) on the stability and microstructure of CGAs. We demonstrate that 5000 ppm KCl provided the most stable system with microbubbles in the size range predominantly larger than 50–100 μm. For enhancement of system robustness, two solid-phase additives were incorporated: natural gilsonite at 100 and 500 ppm, and Fe₃O₄ nanoparticles at 500 ppm (which is equivalent to 0.05 wt%). Combination of 100 ppm gilsonite and Fe₃O₄ exhibited optimum improvement in CGA stability. Physicochemical properties of the optimized systems in contact with heavy crude oil were examined in the final phase. Among all the tested salts, MgCl₂ exhibited lowest IFT (39.02 dynes/cm) and contact angle (20.58°), and shows enhanced oil-wettability alteration. This in-depth study not only provides new insights into salinity, nanoparticle, and natural additive synergistic impacts on CGA behavior but also paves the way for the development of specially formulated CGA formulations for the use in enhanced oil recovery from high-salinity reservoirs.