Evaluation of interfacial properties due to the effect of dispersing agents on Brazilian medium crude oil

Abstract

Through the Deepwater Horizon oil spill accident in 2010, around 7.000 m3 of chemical dispersants were applied to a subsea blowout until the release of crude oil to the environment was ended. Since then, chemical dispersion has become one of the major capabilities for oil spill response around the world. Because of this relevancy, this article aims at expanding the current knowledge of interfacial phenomena related to chemical dispersants application at oil spills, with focus in a representative Brazilian crude oil which has never before been assessed with this purpose. Therefore, first this oil was characterized, and a weathering process was simulated by preparing samples with different distillation and emulsification features. After this, samples dispersion effectiveness’s was evaluated using a low-energy method and a commercial product: Corexit EC9500A. Because only the fresh oil condition result was considered satisfactory, its interfacial behavior was investigated with more details. First, the interfacial tension was investigated as a function of water salinity and dispersant concentration. Dynamic interfacial tension was measured individually for dioctyl sodium sulfosuccinate (DOSS), Tween 80 and Span 80, the main components many of current commercial chemical dispersants. Finally, the partition coefficients and dilational rheology parameters were evaluated for different concentrations and conditions. The individual surfactants behavior assessment results published in this paper will allow further comprehension of the interfacial behavior in this specific oil-water system, thus providing data for future researches aimed at optimizing chemical dispersion effectiveness for similar crudes produced in maritime sea basins of Brazil and also supporting regulators in the decision-making process necessary for protecting environmental resources during an oil spill. A future paper will explore mathematical correlations between chemical dispersion effectiveness and surfactants’ mixture ratios, emulsions’ stabilities and other interfacial properties of some Brazilian crude oils.