Demulsification mechanism of simulated liquid production in the polymer-surfactant flooding process

As a new type of oil displacement agent, the compound of polymer-surfactant has a strong ability of increasing viscosity, emulsifying, etc. Results of the field test showed that the polymer-surfactant flooding can enhance oil recovery by 18.8% above water flooding. Field test showed that compared with polymer flooding, the settling time of the produced liquid of polymer-surfactant flooding is longer, and dehydrated electricity is higher, so it is more difficult to handle the produced fluid which has a higher requirement for adaptability of dehydration system of water and polymer flooding. To improve the matching techniques of polymer-surfactant flooding and get a satisfied demulsification result to ensure the produced liquid of polymer-surfactant is separated effectively, the demulsification and demulsification mechanism is studied. The results showed that, the demulsification effect of the non-ion polyether demulsifier is better than the cation polyether demulsifier, and the demulsification effect of the HLX-2 demulsifier which is a non-ion polyether demulsifier is the best. When the concentration of the HLX-2 demulsifier is 50mg/L, the oil content in water is 257mg/L, the water cut in oil is 28%, and the demulsification ratio is 92.5%. Increasing the content of the polymer-surfactant, the oil-water interfacial shear viscosity is increased, the demulsification is more and more difficult, and the demulsification effect of the HLX-2 demulsifier is getting worse and worse. Results showed that, polymer-surfactant molecule in the oil-water interface was replaced by the demulsifier HLX-2, and the interfacial shear viscosity and interfacial elastic modulus was reduced, and the stability of the emulsion was declined. Increasing the concentration of the demulsifier HLX-2, the replacement role enhanced. So the demulsification mechanism of the nonionic polyether demulsifier is that interface membrane is replaced. After the molecule of the demulsifier replaced the emulsifier, the strength of interfacial film was reduced, and the molecular of the demulsifier can also “catch” a few emulsion droplets, resulting in more than one droplet was coalesced, and the purpose of fast-breaking was achieved.