Factors and Kinetics Related to the Formation of Heavy Oil-in-Water Emulsions

Oil-in-water emulsions provide an essential contribution to enhanced oil recovery by acting as oil displacement and conformance control systems. However, the dominant factors affecting their emulsification and kinetics are unclear. The emulsification rate is usually defined in terms of changes in the torque, conductivity, or particle size over time, which results in inaccurately calculated emulsified oil amounts. Therefore, the effects of temperature, pH, and NaCl concentration on the emulsified mass and droplet sizes of aqueous emulsions of Jin8-7 and Chen373 oil with octadecyl amine ethoxylate ether as an emulsifier were investigated. The results showed that the formation of oil-in-water emulsions of Jin8-7 and Chen373 under different conditions occurred via a two-stage mechanism: rapid emulsification and emulsion maturation. The emulsified oil mass rapidly increased during the rapid emulsification period and plateaued during the emulsion maturation period. This indicates that the emulsified oil mass largely depended on the short rapid emulsification period. It was also found that increasing the temperature and pH were more conducive to the emulsification of Chen373 oil with a high viscosity and high asphaltene content. The optimal NaCl concentration was determined to be 2% and 4% for Chen373 and Jin8-7 oil, respectively, based on the emulsification mass during the rapid emulsification period. The droplet size decreased first and then increased during the emulsification process under most experimental conditions. A second-order kinetics model for emulsification was proposed, in which the evolution of emulsified oil mass calculated with time agreed with the experimentally measured values. This study can provide theoretical guidance for the implementation of chemical cold production of heavy oil in oilfields.