Effect of water salinity on oil/brine interfacial behaviour during low salinity waterflooding: A mechanistic study

In recent years, controlling the salinity and composition of the injected water has become an emerging enhanced oil recovery (EOR) technique, often described as low salinity (LS) waterflooding. This work is done with the intention to contribute to the ongoing discussions about LS waterflooding mechanism(s). For this purpose, a series of different experiments were conducted. At first, the effect of salinity on the interfacial tension (IFT) and the contact angle was evaluated with a crude oil sample. Then to achieve more accurate results in observing oil/water interface, similar IFT experiments were also carried out on a synthetic oil containing asphaltenes. Thereafter, microscopic visualization using glass micromodel was performed on the interface of the synthetic oil sample and brines. Four brine solutions including Sea Water (SW), it's dilutions and formation water (FW) were used for various experiments. Finally, to investigate the presented mechanism by other authors, a series of Environmental Scanning Electron Microscopy (ESEM) analysis on the synthetic oil was carried out to understand better the phase behaviour after contacting both synthetic oil and water phases from the micromodel experiment. Based on the existing mechanism, there exists an optimal concentration beyond which dilution is no longer an effective process.