Petroleum Emulsions: Mechanism, Challenges, and Chemical Resolutions

Abstract: This paper reviews the emulsion stability in chemical enhanced oi recovery (CEOR) and Steam-Assisted Gravity Drainage (SAGD) operations. Interfacial tension and interfacial rheology measurements have been performed to study the effect of the aggregation state of asphaltenes present in SAGD at the oil/water interface.   The results showed that asphaltenes self-aggregated at the interface and formed an irreversible cross-linked network of a gel, acting as a stabilizing mechanism for produced emulsions. When the interface was aged, its gel strength was much higher than the fresh interface, suggesting an explanation as to why aged emulsions are more difficult to treat. Unlike elasticity and interfacial tension measurements, it was demonstrated that film compressibility measurements can predict emulsion stability under different conditions.

The effects of alkali, polymers, surfactants, asphaltenes, resins and shear rates on emulsion stability in CEOR were also investigated by measuring the zeta potential, emulsion droplet size, interfacial tension and elastic modulus. Emulsion stability decreased with an increase in salinity or water cut. An increasing surfactant concentration, temperature, or shear rate enhanced emulsion stability. The effect of polymer on emulsion stability is complicated. Polymer can form a “bridge” between two oil droplets and decrease the emulsion stability; however, polymer can also enhance the emulsion stability via electrostatic and steric stabilization.

The test methods discussed in this paper can provide the fundamental understanding of emulsion stabilization caused by polymers, surfactants and asphaltenes and can potentially be employed to study the structure and demulsifying performance relationships of emulsion breakers (EBs).