Role of asphaltenes and resins at the interface of petroleum emulsions (W/O): A literature review

The challenge of water-in-oil (W/O) emulsions in oil recovery processes is a key focus in current research. This literature review explores the role of natural emulsifiers, specifically asphaltenes and resins found in crude oil, in stabilizing these emulsions at the water-oil interface. Utilizing RStudio software, bibliometric research was conducted in Science Direct, Web of Science, and Scopus databases. Relevant articles were analyzed to showcase the evolving understanding of asphaltenes and resins interaction mechanisms with water droplets in an oily medium. Numerous factors influencing the interfacial activity of asphaltenes and resins were identified, including aromaticity, organic acid presence, pH, asphaltene aggregate size, salt content, asphaltene size relative to resins, asphaltene structure, and functional groups in both compounds. Emphasis was placed on asphaltenes as the primary agents for emulsion stabilization, validated through bottle tests and optical microscopy. Resins were identified as crucial for reducing interfacial stress (IFT), as confirmed by IFT and Interfacial Forces Viscosity tests. However, disagreements persist, attributed to the compounds diverse compositions and structures. Various techniques were employed for studying these compounds actions in emulsions, such as small-angle neutron scattering, critical electric field, IFT, viscosimetry/rheometry, bottle tests, and optical microscopy. Resin and asphaltene characterization predominantly used gas chromatography (GC), infrared (IR), and elemental analysis. This work serves as a foundational resource for future studies, encompassing theoretical concepts, demonstrated mechanisms, the current research landscape, and commonly used techniques in this field. It addresses the potential variability of these compounds and contributes to understanding their roles in emulsion stabilization and interfacial stress reduction.