Study On Oil/Water Separation Of Sewage Produced In Alkali-srfactant-polymer Flooding

Since 1990s, the Daqing Oilfield has entered into high water-cut stage, so alkali - surfactant-polymer (ASP) flooding has been tested for many times to improve oil recovery, and the results are remarkable. However, the weak alkalis, surfactants, polymers used in ASP flooding make sewage complicated, emulsify seriously, and make oil-in-water emulsion more stable, the amount of oil in water increase greatly. So it is necessary to demulsify sewage to recycle oil in it before its discharge. The purpose of this paper is to select effective demuls - ifying and flocculating agents used in demulsification treatment. Besides, a kind of water-soluble demulsifying agent, polyquaternery amine, was synthesized and its optimum synthetic formula and demulsification effect was researched.Chemical demulsification was used in the experiments of this paper to select comparat - ively effective demulsifying agents and method. The experimental results indicate that demulsifying agent SP169 has better demulsifying effects. In view of economic benefits and demulsifying effects, additive dosage of SP169 was set at 50 mg/L, and the breaking time was 2h. And this method was used to study the alone effect or synergistic effect of alkalis, polymers, surfactants in oil-displacing agent on the emulsifying state of the emulsion.After demulsified and moderated its pH, sewage was flocculated with three kinds of polymerized aluminum salt separately and then coagulated with three kinds of cationic polyacrylamide(CPAM) of different molecular weights respectively. The treatment effects were studied and the results showed that the optimum flocculating pH is 6.5, the dosage of inorganic flocculating agent, AS, is 1000 mg/L, and that of organic coagulating agent, CPAM of 12 million molecular weight, 15 mg/L. After treated, the light transmission rate of sewage is 96.8% and the treatment effect is best.To save agents and cost, and protect environment, three kinds of water-soluble reverse demulsifiers, cationic polymeric quarternary ammonium salts, were synthesized. Their performance in demulsification was compared, and the results showed that PRJ2 is most effective in demulsification treatment of sewage produced in ASP flooding. Its optimum dosage is 80 mg/L and the oil removal rate is 94.56%. Besides, the compatibility of PRJ2 and flocculating agent, PFAS, is best. And in this formula the dosage of PAFS is 800 mg/L and the oil removal rate is 94.56%. The treated sewage meets the reinjection standards and this method is a good way to save cost.