Waxy Crude Oil Emulsion Gel: Impact on Flow Assurance

In oilfield operations, the formation of crude oil emulsions is very common and can cause significant flow assurance problems during oil production. These emulsions can be very stable as a result of the presence of polar compounds, such as asphaltenes and resins, that play the role of natural surfactants and also because of the occurrence of many types of fine solids that can form resistant films at the crude oil/water interface. Gelled waxy crude oil flows have been largely studied, and the effect of dispersed water on crude oil rheology has been well-characterized; however, little attention has been given to the potential impact of waxy crude oil emulsion gel formation. In this study, it is shown that in some waxy crude oils the presence of water above a threshold value could promote gel formation, significantly changing the viscosity of the mixture. The rheological properties of waxy crude oils were determined at different water cuts, temperatures, and shear rates, and also a chemical characterization of these waxy crude oils was carried out. Highly stable and viscous emulsions with water cuts as high as 70% and wax-oil gel emulsions were observed. Rheological flow curves show viscosity values much higher than usually obtained for other waxy crude oils. Furthermore, strong shear-thinning behavior of the crude oils and emulsions at low-temperature conditions were seen as well.