Comprehensive Study of the Efficiency of Low-Concentration Nanoemulsions with Diesel Fuel for Enhanced Oil Recovery

This article presents the results of experimental studies examining the effectiveness of low-concentration nanoemulsions for enhanced oil recovery (EOR). The maximum volume concentration of diesel fuel in the emulsions did not exceed 1% by volume. The volume concentration of the emulsifier ranged from 0.05% to 0.4%. A method for preparing stable nanoemulsions was developed. The colloidal stability, viscosity, interfacial tension, wettability, and capillary imbibition rate of low-concentration nanoemulsions were studied. Filtration experiments were conducted to study oil displacement on microfluidic chips simulating a porous medium and core samples. This is the first systematic study of the properties of nanoemulsions containing diesel fuel. It was demonstrated that the developed emulsions have high potential for EOR. It was shown that increasing the emulsifier concentration reduces the contact angle from 35 to 16 degrees and halves the surface tension coefficient. Experiments studying the capillary imbibition of oil-saturated cores with nanoemulsions also confirmed their ability to reduce interfacial tension and improve rock wettability. Oil displacement efficiency during capillary imbibition increases by 22%. Filter tests on microfluidic chips and core samples confirmed the high efficiency of the developed nanoemulsions. Increasing the emulsifier concentration in the emulsion to 0.4% increases the displacement efficiency from 32% for water displacement to 57% for nanoemulsion displacement. Core tests showed that additional injection of nanoemulsions significantly increases the oil displacement efficiency by 10–14%, depending on the emulsifier concentration in the nanoemulsion. It was also established that the use of an aqueous solution of an emulsifier without a hydrocarbon phase does not provide such a significant increase in the displacement coefficient as in the emulsion composition.