Abstract
Enhancing oil recovery in clay-rich sandstone reservoirs remains a critical challenge, particularly for heavy oil extraction. Although low salinity water flooding has been widely investigated, the synergistic potential of combining cationic surfactants, such as cetyltrimethylammonium bromide (CTAB), with low salinity water to improve emulsion stability and, consequently, oil recovery in such reservoirs has received limited attention. This study pioneers a novel experimental approach to investigate the simultaneous impact of CTAB and smart water flooding on heavy oil recovery in clay-rich systems. By exploring the interplay between ion-tuned water and CTAB, we uncover new insights into their combined influence on emulsion behavior, interfacial properties, and oil mobilization. In this regard, the interfacial tension (IFT) and zeta potential values for sulfate-enriched seawater containing CTAB were approximately 15.2 mN/m and 6.4 mV, respectively, lower than those of magnesium-enriched seawater. This indicates enhanced interfacial activity and clay surface modification. Emulsion stability tests revealed that reduced ion concentrations, especially in sulfate-enriched aqueous solutions, significantly enhanced emulsion stability. This was illustrated by an extended emulsion separation time of approximately 70 min under these conditions. Moreover, fourier transform infrared spectroscopy (FTIR) analysis of the separated oil phases from the emulsion revealed a notable reduction in polar components in oil exposed to cation-rich water, while non-polar components were more prevalent in oil contacted with sulfate-enriched water. The contact angle measurements indicated that sulfate-enriched seawater (SW2d.2SO4) exhibited the lowest contact angle (31°) among all brine solutions. These findings provide insights into the mechanisms of emulsion stabilization and the role of oil components, offering a transformative perspective on optimizing smart water flooding with cationic surfactants for improved heavy oil recovery in clay-rich reservoirs.