R e p r o d u c e d with p e r m issio n o f th e co p y r ig h t o w n e r . F u rth er rep ro d u ctio n p roh ib ited w ith o u t p e r m issio n .

The primary objective of this work was to determine the effect of emulsified water on the onset and the amount of asphaltene precipitation from diluted crude oils. Asphaltene precipitation yields were measured from an Athabasca bitumen and a Gulf of Mexico crude oil diluted with n-heptane. The experiments were performed with and without emulsified water added to the oils. Yields were compared to determine the effect of the emulsified water. At dilution ratios above the onset of precipitation for dewatered oils, yields were observed to be same for both dewatered oils and oils emulsified with water. Hence, the presence of water had no detectable effect on the solubility of asphaltenes in a crude oil. However, asphaltenes adsorbed on the surface of emulsified water droplets were removed with the water droplets and reported as yield below the onset. The secondary objective of this work was to analyze the compositional differences between the asphaltenes precipitated at the onset condition, asphaltenes adsorbed onto the interface, and bulk asphaltenes. On the basis of CHNSO analysis, it was found that there is no compositional difference between these three different asphaltenes. ■ INTRODUCTIONOne of the flow assurance issues in the oil industry is asphaltene precipitation from crude oils. Asphaltenes can be precipitated when the oil experiences changes in pressure, temperature, and composition. Usually, crude oil samples with no or very little water (typically around 0.5 wt %) are used for asphaltene phase behavior modeling or assessing the risk of asphaltene precipitation in the laboratory. However, crude oils are almost always co-produced with formation water and also with injected water during secondary or enhanced oil recovery processes. In the case of bitumen extraction processes, a large amount of water is used for froth treatment, and therefore, water-in-oil emulsion formation is unavoidable. When present, water is usually emulsified in the oil but can also have an appreciable solubility at sufficiently high temperatures (generally above 250°C). The effect of the presence of water on the measured onset and yield of precipitated asphaltenes is not understood. The focus of this study is to investigate only the effect of emulsified water on asphaltene precipitation from diluted crude oils.Most of the investigations on the effect of water on asphaltene precipitation have focused on solubilized water. Solubilized water may affect asphaltene self-association, which, in turn, can affect asphaltene precipitation. Andersen et al. 1 tested this idea with calorimetric measurements of asphaltene association. A sample of dewatered toluene was placed in a calorimeter, and an asphaltene−toluene solution was added. The amount of heat absorbed because of the addition of the solution was measured and related to the aggregation behavior. The experiment was then repeated with an asphaltene−toluene solution containing trace amounts of water (∼0.047 wt %). The data indicated a change in the amount of heat absorbed with a change in ...