Salinity adjustment to improve the efficiency of nano glass flakes (NGFs) in interfacial tension reduction

Nanoparticles (NPs) have been recognized as the agents that can improve the oil recovery given their positive impact on the surface wettability of rocks. However, their impacts on the interfacial tension (IFT) of the two-phase fluid in a reservoir have not been widely reported. Given the significant impact of IFT on the oil recovery, it is important to develop an NPs based approach that not only alter the surface wettability but also reduce the IFT. This may be accomplished by combining nanofluids with low salinity water (LSW). In the present study, LSW and NPs are combined to study their impacts on the IFT of a two-phase flow system with water and oil. IFTs of different solutions with nano glass flakes (NGFs) and nano silica (Ns) were measured in the presence of monovalent and divalent salt ions. The results obtained were analysed using two different models as a function of time. It was found that NGFs and Ns have similar efficiency in reducing the IFT and can reveal an optimum performance once their concentration reaches 24.8% in the solution. It was observed that, unlike Ns, IFT can be further reduced by LWS in the presence of NGFs. In fact, reduction of salinity up to 3500 ppm can decrease the IFT in the NGFs solution by the salting-in effect or migration of oil components. Changing the pH of the system can also reduce the IFT, but fluctuations was observed once pH goes beyond 9. It appeared that the tension in the interface between water and oil reduces over time and the effect of adsorption time is significantly higher on the solutions with nanoparticles. It was concluded that combining NGFs with LSW not only reduces the concentration of NPs needed and can make the project economically feasible, but also favourably change the IFT during the flooding process. The findings of this study may help to understand how LSW, and nanofluids can be employed together for a better oil recovery.