The Rheology of Heavy Crude Oils And Their Emulsions

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Abstract
Emulsions of heavy crude oil-in-distilled water were formed using a rotational turbine mixer with Triton X-100 as an emulsifier. The rheological characteristics of two heavy crude oils and their emulsions were studied using concentric cylinder Gild cone and plate rotational viscometers. The effects of shear rate and temperature on the flow characteristics of distilled water-m-oil emulsions and the effect of shear rate on the flow characteristics of oil-in-distilled water were determined. The results show that emulsions exhibit Newtonian flow behaviour at low dispersed phase concentrations and pseudo plastic behaviour at higher concentrations, In addition, the viscosity is shown to be only slightly time dependent at higher shear rates. It was noted that a large discontinuity in the viscosity occurs at disperse phase concentrations of 30 to 40% Of the distilled water-in-oil emulsions. This may have been caused by a minor inversion of the water-in-oil emulsion to a dual water-ill-oil-in- water emulsion. The viscosity of the dual emulsion would be lower because the water forms the continuous external phase. Introduction In the past emulsion properties and emulsions themselves have only been of minor interest in enhanced oil recovery technology. With the major trendto improved oil recovery schemes., the use of emulsions to increase oil recovery has sparked interest to further understand emulsion behaviour flow properties. Emulsion science has been developed by a range of industries, from paints to cosmetics and from foods such as milk products to pesticides. The rheologic properties and characteristics of emulsions have been of interest because of the many applications of emulsions. The oil producing industry can no longer merely consider emulsions to be dealt with when they occur. Many researchers are now seeking to apply emulsions to improve the recovery of oil. The study of the rheological properties of crude oils and their emulsions was the broad objective of this study. Specific objectives included:The determination of the rheology of both water-in-oil and oil-in-water emulsions of crude oil and distilled water.The demonstration that emulsion viscosity can be dependent on the shear rate because of non-Newtonian behaviour. More specifically, the emulsion can be non-Newtonian at some concentration and Newtonian at other concentrations.Relating the emulsion viscosity as a function of shear rate, temperature and disperse phase concentration. Apparatus and Experimental Procedure; The two heavy crude oils used in this study were: Epping Crude Oil and Cold Lake Crude Oil. The Epping Crude Oil had an API gravity of about 11.8 degrees and viscosity of about 50 000 mPa.s at 21°C (and 1.0 5−1). The crude oil was proudced in May 1976 and dewatered and dried in February 1978. The long period of storage resulted in an alteration of some of its properties (specifically, aging increased the viscosity of the oil by slow oxidation with air).The original (1976) viscosity measured was 1120 mPa.s at 40°C (and 0.89 s−1) for the dried crude oil.

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