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Interfacial Properties of Water–Crude Oil Systems Using the Oscillating Pendant Drop. Correlations to Asphaltene Solubility by Near Infrared Spectroscopy

Abstract The interfacial rheological properties of 21 crude oils and condensates have been studied by the use of an oscillating pendant drop apparatus. The crude oils and condensates were diluted in heptane/toluene solvents in order to simulate the interfacial concentrations of surfactants in real water‐in‐crude oil emulsions. Both the effect of varying the solvent composition and the crude oil concentration in the solvents has been studied. Near infrared (NIR) spectroscopy was utilised to produce a measure of the asphaltene aggregation state of the crude oil solutions. At low oil concentrations the most elastic interfaces were produced in highly aliphatic solvents due to the high interfacial activity of the indigenous crude oil surfactants, the resins and asphaltenes, in such solvents. At higher oil concentrations in aliphatic solvents this effect was contradicted by the formation of larger, and less interfacially active asphaltene aggregates. When comparing the interfacial elasticity of the individual crude oils at equal solvent conditions no clear correlation between the amount of resins and asphaltenes in the samples, and the measured interfacial elasticity was found. This indicates that not only the amounts, but also the chemistry of the interfacially active components of crude oils to a large extent determines the interfacial rheological properties.