(92c) Experimental Study and Molecular Thermodynamic Modeling of Winsor Type III Systems in Enhanced Oil Recovery (EOR)

Conventional modeling approaches for surfactant-oil-water systems in the “surfactant flooding” enhanced oil recovery (EOR) technique involve empirical correlations that require considerable experimental data and are not predictable for new systems [1]. Conversely, a straightforward molecular thermodynamic approach has been successfully used to describe the phase behavior of a variety of self-assembled systems including pure and mixed nonionic/ionic micelles and vesicles [2-4]. The ideal EOR formulations are surfactant-oil-salt water-alcohol mixtures that forms microemulsions (Winsor type III systems), which have an ultralow interfacial tension allowing them to reach deep into reservoir capillaries [1]. We show in this work how the key variables including alkane carbon number, salinity, surfactant type including tail alkyl chain length and head group characteristics, surfactant and alcohol concentration, and temperature can be used within the Blankschtein framework to predict attractive new W III systems. This study investigates three model n-alkane oil components (C₆, C₈ and C₁₀), sodium chloride as the salt, polyoxyethylene glycol monoether nonionic surfactants, and n-alkanol co-surfactants. Phase behavior formulation scans, in which one of the key variables is systematically changed in a series of prepared mixtures allowed to settle in graduated cylinders, are performed to identify formation and extent of the microemulsion phase for several combinations of variables.

[1] Salager, J.-L., Forgiarini, A. M., and Bullon, J., How to Attain Ultralow Interfacial Tension and Three-Phase Behavior with Surfactant Formulation for Enhanced Oil Recovery: A Review. Part 1. Optimum Formulation for Simple Surfactant-Oil-Water Ternary Systems, J. Surfact. Deterg., 16, 449-472 (2013).

[2] Puvvada, S., and Blankschtein, D. Molecular Thermodynamic Approach to Predict Phase Behavior and Phase Separation of Micellar Solutions. I. Application to Nonionic Surfactants, J. Chem. Phys., 92, 3710-3724 (1990).

[3] Yuet, P.K., and Blankschtein, D. Effect of Surfactant Tail-Length Asymmetry on the Formation of Mixed Surfactant Vesicles, Langmuir, 12, 3819-3827 (1996).

[4] Shiloach, A., and Blankschtein, D. Measurement and Prediction of Ionic/Nonionic Mixed Micelle Formation and Growth, Langmuir, 14, 7166-7182 (1998).