The Research Of The Stability Of Poly-containing Wastewater And Treatment Technology

At present, cross-linked polymer flooding is an important technique to enhance oilrecovery applied by most domestic oilfields. However, this method also brought manyproblems to the oilfield sewage treatment. It increased large amount of polymers to thewastewater, enhanced the oil-water emulsification, and increased the concentration of oil inthe wastewater. Futhermore, it brouthg huge difficulty for demulsification. Thus, a reasonabletreatment to the poly-containing sewage is crucial to oilfield development.The profile-controlling flooding technique with surfactant-polymer and crosslinkingagent was applied by Shuanghe region and Xiaermen region in Henan oilfield, and an effectiverole in enhancing oil recovery was obtained. But the polymers contained in the oilfield sewagealso brought much troublesomes to the sewage treatment. This thesis takes the oilfield sewageproduced by Team5,7,12of Shuanghe region and Xiaermen region of Henan oilfield as itsresearch objects, explores the causes influencing the stability of poly-containing wastewaterthrough detailed analysis of the water sample and adding gel and demulsifiers to the modelwater, and then flocculation and chemical oxidation method were used to study the optimumwater treatment chemicals for this poly-containing sewage.The results show that the oilfield sewage produced by these three teams is characterizedby large amount of polyacrylamide, high content of oil, strong emulsification, median contentof ions, low acidity, and high content of bacteria, and team-7is the highest of them. Analysisresults with weak gel finally indicates that the polymer creates a system of thermodynamicstability, which reduces the interfacial tension of oil-water, and promotes the strength of theinterfacial film. And this is an import factor which enhances the stability of the sewage.The experiments of flocculation and oxidation indicate that a mixed dosage of80mg/LNaClO+60mg/L ZnCl2+120mg/L PAC+3mg/L PAM at pH7.5achieve desirable treatingeffect of polymer flooding sewage produced by Shuanghe region and Xiaermen region inHenan oilfield. Through the above treatment， the CODCrin the sewage can reach the standardof secondary integrated emission；and the indexes of oil content，suspended particles，andsulfides in the sewage can reach the standard of first-level emission.