Dilatational elasticity moduli of water-crude oil interfaces using the oscillating pendant drop

The oscillating pendant drop instrument was used to measure the dilatational elasticity modulus and dynamic interfacial tension of 21 crude oils and condensates originating from different production fields. The samples were diluted in different heptane/toluene solvents at concentrations of 0.002, 0.01, and 0.02 mL oil/mL solvent. Both the solvent composition and oil concentration were found to have a great influence on the measurements. Higher aromaticity solvents reduced the interfacial activity of the natural surfactants in the crude oil. Different time dependences in the build up of the elastic interfaces for the crude oils were also found. The samples have also been subjected to SARA analysis and TAN (Total Acid Number) determination, and the results have been correlated to the oscillating pendant drop measurements. Especially the influence of the crude oil surfactants, resins, and asphaltenes, on the interfacial properties was studied. Indications of both interfacial active and non-interfacial active asphaltenes were found. Asphaltene interfacial coverage values of 2.3 and 3.1 mg/m(2) have been reported.