Rheological Properties of Water-in-Brazilian Crude Oil Emulsions: Effect of Water Content, Salinity, and pH
2018
de Oliveira, Cesar B. Z. | Souza, W. J. | Santana, C. F. | Santana, C. C. | Dariva, C. | Franceschi, E. | Guarnieri, R. A. | Fortuny, M. | Santos, A. F.
During the crude oil production, stable water-in-oil (W/O) emulsions are generally found along the pipeline between the reservoir and surface facilities. The main objective of this work is discussing about the influence of the salinity (with NaCl at 0, 50, and 100 g·L–¹), pH (2, 6, and 10 values), and water content (variations between 8% and 65%) upon the rheological behavior of water-in-crude oil emulsions. Tests including the rotational and oscillatory rheology for assessment of profiles of viscosity, elastic and viscous modulus for the different cases were performed. Semi-theoretical models and available empirical literature models have been successfully used to fit the rheological data, enabling a better understanding of the interactions between the constituents of the samples at a colloidal level. Results presented here show that the emulsion loss modulus calculated from bulk rheological tests does not respond differently for acid, quasi-isoelectric point and alkaline aqueous phase; this modulus also has a salt content-independent behavior for crude oils with different content of resins and asphaltenes. The presence of electrolyte in the emulsions may decrease the storage modulus, once the concentration of resins and in special asphaltenes were low. For higher content of these molecules, the attractive electrostatic forces are not enough to change the interfacial tension between the macromolecules.
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