Document Type : Research Paper
Authors
(Laboratory of Research and Methodology Development for Petroleum Analysis), Chemistry Department, Federal University of Espírito Santo (UFES), Goiabeiras, Vitória, ES, Brazil
Abstract
Due to stability problems, petroleum emulsions are still considered a major challenge for the industry. Heavy oil contains high levels of polar compounds and forms highly stable emulsions that are difficult to treat. The aqueous phase of these emulsions, composed of formation water (FW), has high salinity, and these salts can influence the behavior of the emulsions differently. Therefore, the main objective of this study was to evaluate the effect of different saline species on the stability of heavy-oil emulsions. The emulsions were prepared by adding increasing volumes (0.1, 1.0, 10, 20, and 30% w/v) of an aqueous phase containing deionized water (DW), FW, and saturated saline solutions. The emulsions were homogenized at 5,000 rpm for 3 min. The relevant factors were evaluated, including salt type, gravitational separation, temperature, droplet size distribution (DSD), and interfacial tension. The results revealed that emulsions prepared with some acid pH salts and high ionic strength showed kinetic instability with separation from 3.33 to 21.17% of the aqueous phase after 15–25 days of preparation. In contrast, the others remained stable after 30 days, even heating up to 80 °C. Concerning the average DSD, emulsions with acid pH salts showed higher values (1.67±0.36 to 9.03±2.81 µm), whereas lower values (1.09±0.23 to 4.83±1.06 µm) were found in emulsions with DW. The interfacial tension of the dehydrated oil increased in the presence of the salts, especially those with acid pH and high ionic strength, presenting values from 5.37±0.43 to 22.37±0.77 mN/m. Conversely, basic saline solutions decreased the interfacial tension considerably to values below 0.01 mN/m. These results can contribute to a better understanding of heavy oil W/O emulsions stability, considering water phase properties such as pH, ionic strength, and ionic radius of the cation..
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