A thermodynamic model for LLE behavior of oil/brine/ionic-surfactant/alcohol co-surfactant systems for EOR processes

In this paper application of a thermodynamic model based on NRTL method combined with Debye–Huckel activity coefficient model for electrolyte solutions to represent liquid–liquid-equilibrium (LLE) behavior of systems containing oil, brine and ionic surfactants is investigated. Results are presented in terms of phase split and compositional analysis and compared with experimental data. The effect of degree of dissociation of salt and surfactant in water on the model prediction is also examined. Parameters of Peng–Robinson Equation of State are also determined for such LLE calculations and the methods have been compared with two sets of experimental data. In the second data set, the system contains alcohol co-surfactant in addition to oil, brine and a petroleum sulfonate anionic surfactant. Investigated models may be suitable for evaluation and simulation of chemical EOR projects.