Asphaltene induced W/O emusilon: False or true?

Tight brine-in-oil emulsions and related high viscosities are common oil field problems experienced in mid- to late-life. Emulsions can have a detrimental effect on water separation efficiency, and costs for injection equipment and demulsifier chemicals are high. It is commonly assumed that asphaltenes play a dominant role in emulsion formation, although in some crudes it was found that resins play a role in emulsion formation, especially the carboxylic acids. For the asphaltenes, polarity, and crude oil aromaticity play an important role in their interactions at the oil-water interface, and to a lesser degree the brine pH. For the resins, pH plays an important role, as carboxylic groups are mostly active when de-protonated. In this article, we studied the role of asphaltenes in oil/water emulsions by application of Critical Electrical Field measurements in topped oil and de-asphalted topped oil. The emulsion stability was measured for a range of water cuts (from 2 to 60%), brine pH, temperature, and shear rates.