Microscopic scale interactions of water ions at crude oil/water interface and their impact on oil mobilization in advanced water flooding

In this study, we performed interfacial shear rheology, surface potential and oil droplets coalescence time measurements to investigate microscopic scale interactions of various individual water ions at both air-water and crude oil-water interfaces. The measured interfacial rheology data indicated completely different interfacial behavior at crude oil-water interface when compared to air-water interface due to the presence of crude oil functional groups. Viscous dominated response was observed at crude oil-water interface for all brine compositions. Lower interfacial viscous modulus was observed for certain key ions such as calcium, and magnesium. The interfacial viscous modulus was found to be substantially much higher for sulfates, besides exhibiting some elasticity. The surface potential was gradually decreased by replacing seawater with calcium only brine. The better surface activity with seawater can be attributed to adsorption of more key water ions at the surface.