A theoretical study of crude oil emulsions stability due to supramolecular assemblies

A main issue in the oil extraction and transportation is the presence of emulsions that are formed due to the physiochemical characteristics of the brine and the oil. The emulsions exhibit an increase in viscosity in comparison to the oil and it is strongly related to the water content and disperse phase morphology, this effect implies a decrease in the oil production due to oil mobility reduction, problems in the transportation, damage to the formation, among others. Experimental evidence of the properties of the emulsions for a heavy Mexican oil is presented where the disperse phase morphology directly relates with viscosity and the presence of a mechanically irreducible emulsion is confirmed. In the crude oil, the components responsible to give stability to these emulsions are mainly the asphaltenes whereas in the brines are the divalent ions, both affected by the presence of acids. In this work, a Density- Functional-Theory study was performed in order to determine the effects that the molecular structure of asphaltenes, oil acidity and calcium chloride have on the stability of water-in-oil emulsions. The aqueous environment was simulated through the Conductor-like Screening Model solvation approach. The experimental observations correlates with the conclusions which supports the idea that the presence of salts and an acidic environment promotes the increase of the viscosity and the formation of stable emulsions.