Rheological study of crude oil/water interface - The effect of temperature and brine on interfacial film

It is of fundamental importance for the petroleum industry to promote the coalescence of water droplets that may be dispersed in oil. Therefore, it is necessary to understand the rheological properties of the water/oil interface, which is straightly related to emulsion stability. This work aimed to present a practical approach about water/oil interface in realistic systems, i.e., using a crude oil and water or brine solution, the last one with the same composition of the water produced along with the oil production. Thus, it was investigated the water/crude oil and brine/crude oil interfaces in terms of their rheological properties at temperatures ranging from 30 °C to 60 °C. The interfacial rheological measurements were performed by the oscillatory pendant drop technique. The results indicated that temperature has a negligible effect on the interface properties; however, the salt content in the water phase resulted in an increase in the viscous modulus between 30 °C and 60 °C. The interfacial viscous and elastic moduli were shown to be dependent on the droplet oscillation period. Despite the elastic modulus being almost the same for water and brine, for the brine system the viscous modulus was significantly higher than that observed for water.