Investigation of fluid-fluid interaction between surfactant-ion-tuned water and crude oil: A new insight into asphaltene behavior in the emulsion interface

Abstract

This research aims to investigate the fluid-fluid interaction between surfactant-ion-tuned water and crude from a macroscopic and molecular point of view. In this regard, the surfactant solutions with the bases of distilled water, seawater, Mg folded seawater, Ca folded seawater, and Sulfate folded seawater were mixed with the crude oil to produce the emulsion phase. The Cetyltrimethyl Ammonium Bromide (CTAB), Sodium Dodecyl Sulfate (SDS), Cocamidopropyl betaine (CAPB), and Tween 80 were used as representatives of each type of surfactant. The rheological tests and Interfacial tension (IFT) of the oil phase were investigated, as well as the molecular characterization of oil phase asphaltene using analytical techniques, such as Nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), and Energy Dispersive X-ray (EDX). The rheological tests and the IFT measurements indicated that both the large and small hydrocarbons are adsorbed in the emulsion phase. Besides, regardless of the surfactant type, asphaltenes have more affinity to be adsorbed in the emulsion phase, where the water base is seawater and magnesium-rich water. The structural data given by the NMR technique showed that more aromatic asphaltenes with shorter associated aliphatic chains have more affinity to adsorb into the emulsion phase. For instance, while the average fused ring number was 9, the average number of the fused ring was 8 for the asphaltenes extracted from seawater-based surfactant solution (Tween 80-CTAB- CAPB). In addition, according to the FTIR index, the asphaltene with high sulfoxide and carbonyl functional group and low alcoholic bonds have more potential to interact with the surfactant. The results of this study could give molecular insight into the fluid–fluid interaction between the surfactant solution and crude oil, providing a new base for the selection of the surfactant-ion composition to improve oil recovery.