Synergistic effects of CTAB and low salinity brines on asphaltene behavior and emulsion stability in clay rich sandstone reservoirs

Improving oil recovery in sandstone reservoirs with higher concentrations of clay particles (clay-rich) presents a persistent challenge, especially in heavy oil extraction. Although low-salinity water flooding has been investigated for sandstone reservoirs, the synergistic effects of heavy oil molecular composition, cationic surfactants (e.g., cetyltrimethylammonium bromide, CTAB), clay particles, and ion-tuned brines on emulsion stability and oil recovery remain poorly understood. This study investigated the molecular behavior of asphaltene under the synergistic effects of CTAB and low salinity water flooding in clay-rich systems. Advanced experimental techniques, including interfacial tension (IFT) measurements, viscosity analysis, and zeta potential assessment, revealed that sulfate-enriched seawater (SW5d.3SO4) in the presence of clay and CTAB hindered asphaltene migration. However, cation-enriched seawater (SW5d.3Mg) promoted asphaltene migration, increasing IFT by ~ 18 mN/m to 48.23 mN/m and decreasing viscosity by approximately 351.3 cP to 249.5 cP. ATR (Attenuated total reflection)-FTIR (Fourier transform infrared spectroscopy) analysis demonstrated that sulfate-rich brines preferentially mobilized less-polar components, whereas cation-rich brines reduced the polar content of the oil phase. Additionally, (SW5d.3Mg) increased the asphaltene onset point precipitation (AOP) by 11% and reduced asphaltene concentration by ~ 5%, enhancing flow assurance. These findings provide critical insights into emulsion stabilization mechanisms and fluid-rock interactions, offering a sustainable strategy to optimize low-salinity water flooding with CTAB for enhanced heavy oil recovery in sandstone reservoirs.