Flow properties of weathered crude oils and their emulsions

The present paper proposes the emulsification of weathered crude oils in wa ter as a competitive and cost effective method for reducing their viscositi es. Weathered crude oil samples were collected from major Kuwaiti oil lakes . Emulsion preparation involved using, either a nonionic surfactant or alka li, as well as both alkali and fatty acid. The obtained emulsions were char acterized by measuring the droplet size distribution of the dispersed phase using optical microscopy. Emulsion stability was also examined in terms of the system breakdown. The rheological properties were measured using a con centric cylinder rotary rheometer. The emulsion rheological behavior has be en studied as a function of composition, temperature, and shear rate. A con stitutive model was developed to characterize the pseudoplastic behavior of the crude oil and the emulsion systems. The model fitted well the experime ntal results with a correlation coefficient higher than 95%. Associated wit h the pseudoplastic behavior, viscoelastic behavior has been observed with emulsions and some oils at high shear rates. The results of this investigation indicated that the examined weathered cru de oils can be transported through pipelines as emulsions of up to 80 vol.% oil concentrations. The proposed method of treatment with NaOH and oleic a cid offers several advantages over the surfactant treatment. It exhibited c omparable rheological behavior at lower cost and less mixing energy. It als o provided higher emulsion stability, which favors oil transportation for l onger distances.