Potential application of a fruit-based natural deep eutectic solvent for water-in-crude-oil emulsification process for enhancing oil recovery and upstream oil applications

The growing demand for oil underscores the importance of efficient tertiary recovery methods. Among these, chemical enhanced oil recovery (CEOR) stands out due to its cost-effectiveness and lower capital investment. Natural deep eutectic solvents (NADES), composed of environmentally friendly and biodegradable components, offer a sustainable alternative to conventional toxic chemicals used in CEOR. This study explores the use of a citric acid/fructose/water NADES formulation for stabilizing emulsions of light crude oil and water, a critical factor for improving oil recovery efficiency. Key variables investigated include the number of moles of water used in NADES preparation, the water dilution ratio, and the molar ratios of citric acid to fructose (CA/Fr) and vice versa (Fr/CA). The study found that although water used in NADES preparation contributes to its structure, its quantity had little effect on emulsion stability. In contrast, optimal water dilution and adjusted CA/Fr molar ratios significantly improved both emulsion stability and viscosity. Injection of the NADES formulation led to effective emulsion stabilization using seawater and brine. Moreover, the NADES injection reduced interfacial tension from 19 to 5.02 mN/m and contact angle from 72° to 30.8°, promoting a water-wet condition favorable for oil displacement. These findings were further validated by rheological tests, which demonstrated increased viscosity and emulsion stability. Overall, this study highlights the potential of NADES as a sustainable, high-performance solvent in CEOR, offering both environmental and operational advantages for future oil extraction technologies.