A mechanistic study of emulsion flooding for mobility control in the presence of fatty acids: Effect of chain length

Abstract

Emulsion flooding is a promising method for enhanced oil recovery (EOR). The static and dynamic behavior of the emulsions is greatly influenced by the nature of the applied surfactant. In this work, the effect of fatty acids, as natural surface-active agents, and their chain length on the emulsion behavior was investigated in both bulk and porous media. A panel of the fatty acids with different chain lengths (6 < C < 18) was applied at constant concentration and pH. Upon the static stability tests, emulsion stability at the optimum value of chain length (C14) was increased by two orders of magnitude. Under the optimal condition, the hydrogen bonding between dissociated and undissociated fatty acids and the tail-to-tail adsorption of fatty acids enhanced the interface coverage. Moreover, interfacial tension was minimum in this case (35.8 mN/m). Additionally, a series of rheological measurements were conducted to examine the dynamic behavior of the emulsion. Two distinct regions were distinguished based on the shear rate. At the low shear rates, a linear relationship was observed between shear rate and shear stress, indicating a solid-like behavior of the emulsions. The effect of the fatty acid chain length on the hydrodynamic interactions was more evident at higher shear rates. Finally, the flooding experiments revealed that there is an excellent consistency between static and dynamic tests. Based on these results, a four-fold increment was recorded in the apparent viscosity of the emulsion in the optimum condition.