Viscosity of Water-in-Oil Emulsions from Different American Petroleum Institute Gravity Brazilian Crude Oils

Abstract

Water-in-oil (W/O) emulsions are very common in oil field operations and are formed as a result of energy input from turbulence caused by the flow in the production pipelines, pumps, and valves. Understanding emulsion rheological behavior is crucial to deal with flow assurance issues. This paper presents and discusses a series of rheological experiments carried out with synthetic emulsions formulated with 126 Brazilian crude oils with American Petroleum Institute (API) gravity ranging from 13° to 35°. This rheological study includes viscosity dependence upon the shear rate, temperature, and water volume fraction. The results show that crude oils with similar API gravity and viscosity can generate emulsions with very different viscosities (8–50 mPa s at 50 °C around 25° API gravity, for example) and different maximum water content limits. Besides, W/O emulsions that are prepared with either light (API gravity of >35°) or heavy (API gravity of <13°) crude oils are the emulsions observed to be the more diffi...