Study on the performances of emulsifying active sub-fractions in polymer-flooding produced water and its treatment

By the investigation of the differences in the composition and concentration of sub-fractions and content of partially hydrolyzed polyacrylamide(HPAM)in polymer flooding produced water between two areas (Gudao2# and Gudao5#) of Gudao oilfield,the effect laws of the interactions among the sub-fractions and between the sub-fractions and HPAM on the stability of the simulated emulsion are studied.And according to the study on the influences of emulsified active oil component and HPAM on the effect results of different treatment agents,some measures for the treatment of the polymer-flooding produced water are presented.The results show that the contents of HPAM and the polar substances extracted by CHCl3 and the sub-fraction SF31 whose acid value is the highest among six sub-fractions in the produced water of Gudao2# are higher than those in the produced water of Gudao5#.The strong interaction between HPAM and the polar sub-fractions such as SF31 and SF42 is observed,and it is shown that the emulsion is extremely stabile and the oil content in the produced water is high when the mass concentration of HPAM is more than 200 mg·L-1.The emulsion is more stable when the mass concentration is more than 1 800 mg/L and Zeta-potential becomes positive as the mass concentration is more than 7 000 mg·L-1 in the present of HPAM.Therefore the interaction between HPAM and salt is a key factor to impact the treatment efficiency of the polymer-flooding produced water.Because of the strong synergistic flocculation between cationic polyacrylamide (CPAM,as flocculant) and HPAM contained in the produced water,the CPAM has a better treatment result for the polymer flooding produced water in Gudao oilfield than other flocculants such as PAC and PDMDAA.