EXPERIMENTAL STUDY OF THE RHEOLOGY AND STABILITY BEHAVIOUR OF SURFACTANT STABILIZED WATER-IN-OIL EMULSION

Abstract

Formation water almost always comes out with crude oil production. Under extreme mixing and high turbulence provided by pumps, valves, chokes and pipelines in the production system, water and oil can mix to form highly stable and viscous emulsions. These emulsions create flow assurance and separation problems in deep water production facilities because of the increasing viscosity with water fraction. In order to predict the changes in viscosity and stability with time it is important to understand the flow behavior of these emulsion in pipelines. It is also important to understand how the acid and bases interact with the other surface active components to stabilize emulsion. This thesis focuses on characterizing the behavior of surfactant stabilized crude oil emulsion with regards to stability, viscosity, total acid and base number. The outcome of this study will be used to study the flow of emulsions in pipelines under different conditions. A reproducible emulsification protocol was established. Experimental data showed that span85 surfactant produces very stable emulsion with the crude oil. Increasing the surfactant concentration only stabilizes the emulsion up to certain amount before additional amount destabilizes the emulsion. Adding surfactant at low concentration reduces the viscosity of the emulsion by as much as 75% when compared to emulsion without any surfactant. Viscosity of the emulsion plays a significant role in emulsion stabilization. Viscosity profile with increasing total acid number shows a minimum beyond which the viscosity increases with increasing total acid number. For a given water fraction, there is a range of total acid number where the acid stabilizes the emulsion. Outside of this range the acid destabilize the emulsion.