Water/oil emulsion and asphaltene instability in different formations during low-salinity waterflooding: an experimental study

Abstract

Previous studies have extensively investigated the effects of salinity on asphaltene behavior at the water-oil contact surface during Low-salinity waterflooding. However, the influence of rocks has often been overlooked. This study investigates the impact of rock type (calcite/quartz) on these phenomena in the presence of various brines (Formation Water (FW), Sea Water (SW), 2 and10 times diluted SW (2DSW, 10DSW), Distillated Water (DW)). UV-Vis spectroscopy was used to assess the asphaltene separation from fresh or aged bulk oil with brine, by using the "indirect method". Microscopic analysis of water droplet size was performed to evaluate emulsion stability. The results demonstrate that the UV-Vis absorbance for fresh oil is approximately 13.6 and that decreases to 11, 10.5, and 10.5 for the 2DSW/oil, calcite/SW/oil, and quartz/2DSW/oil emulsions, respectively. Additionally, the results show that for rock/FW/oil emulsion, compared to quartz, calcite presence increases asphaltene precipitation/deposition by about 38 wt.%. Furthermore, the findings reveal that, across all salinities, the average size of water droplets is larger when calcite is present than quartz, suggesting greater instability in the calcite. These outcomes align with the results of Interfacial tension (IFT) measurement, FTIR spectral analysis of oil, and zetapotential determination for suspended calcite/quartz particles in different brines.