Characterization and demulsification of produced liquid from weak base ASP flooding

Weak base alkali-surfactant-polymer (ASP) flooding technology has been applied in Daqing oilfield to enhance oil recovery. The effects of ASP on the characteristics of oil droplets in produced liquid were investigated. Surfactant can decrease interfacial tension (IFT) and zeta potential, making main contribution to the stability of oil droplets. Weak alkali (Na₂CO₃) can decrease IFT and polymer can decrease zeta potential, resulting in stable oil droplets in produced liquid. The produced liquid from weak base ASP flooding is easier to treat than that from strong base ASP flooding. A mixed demulsifier GFD410-8 was prepared and used to enhance oil–water separation in produced liquid. When the demulsifier dose of 50 mg/kg was used to demulsify the simulated produced liquid with the concentrations of alkali 2000 mg/kg, surfactant 600 mg/kg and polymer 600 mg/kg, water volume and water content after 30 min settling were less than 30% and 1000 mg/L, respectively. The demulsifier also greatly decreased water content in oil phase and oil concentration in water phase for actual produced liquid from oil well. The demulsification mechanism was also investigated in terms of IFT and zeta potential.