Electrocoalescence of surfactant and polymer stabilised droplet pairs

Chemically enhanced oil recovery (cEOR) uses surfactants to create microemulsions by reducing interfacial tension (IFT) and polymers to increase fluid viscosity, enhancing production efficiency. This process results in a complex emulsion that requires separating oil and water to avoid refinery issues. Electrocoalescers are commonly used in this separation but struggle with complex emulsions. This study investigates how the concentration of surfactants and polymers, both individually and together with brine, affects the fundamentals of the electrocoalescer performance. Here, we show the relationship and dependency of the electric field, electrocapillary number (Ca<inf>E</inf>), and cone angle (?) on surfactant and polymer concentration. The results of over 1000+ drop-drop experiments indicate that the solution’s conductivity significantly affects electrocoalescence compared to interfacial tension and droplet viscosity. We found for DI water-based droplets, E<inf>crit</inf> = 4200 V/cm, (CaE)<inf>crit</inf> = 0.065, and ?<inf>crit</inf> = 27?; HPAM (2000 ppm) slightly reduces these to E<inf>crit</inf> = 3600 V/cm, (CaE)<inf>crit</inf> = 0.056, and ?<inf>crit</inf> = 21?, with no further change when mixed with SDS, while SDS alone causes an exponential drop, reaching E<inf>crit</inf> = 1200 V/cm, (CaE)<inf>crit</inf> = 0.02, and ?<inf>crit</inf> = 16? at 3000 ppm. With brine as the base solvent, values decrease further. HPAM (2000 ppm) yields E<inf>crit</inf> = 1050 V/cm, (CaE)<inf>crit</inf> = 0.005, and ?<inf>crit</inf> = 12?, while SDS (3000 ppm) gives E<inf>crit</inf> = 725 V/cm, (CaE)<inf>crit</inf> = 0.01, and ?<inf>crit</inf> = 12?. The findings of this study can be used to understand how complex emulsions are handled in the electrocoalescer. © 2025 Elsevier B.V.