| Polymer flooding is an important method to enhance oil recovery which widely used at home and abroad oilfield, but its pruduced water also brings series of problems to oilfield wastewater treatment system. Compared to flooding sewage water, polymer flooding produced water had features of high viscosity, serious oil-water emulsion, and strong ability to carry suspended solids, large resistance to float or sink of oil droplets and solid particles which is hard to deal with. This article researched the factor and impact of oil content in polymer flooding, such as polymer, surfactant, suspended solids, oil-water ratio, salinity, temperature, time, pH and also. We have evaluated the use of residual polymer in polymer flooding produced water through the interior core flooding experiment and reservoir simulation tool, determined the relationship between improved recovery ratio and residual polymer content and molecular weight, and proposed two different methods of polymer flooding of sewage treatment. For the polymer flooding of sewage of low content of residual polymer and polymer molecular weight less than 500 million, because of its little value, we take the measure of re-injection or efflux after degradation of residual polymer and optimize out of best formula between inorganic flocculants and polymer degradation agents system. The sewage transmittance can reach 90.5%, oil content lower 97.26% and its viscosity is near to water viscosity after dealing with. For the polymer flooding of sewage of high concentration of residual polymer and polymer molecular weight more than 500 million, we take the measure of reserving residual polymer as much as possible and optimize out of best formula between organic flocculants, surfactant and coagulant. The sewage transmittance can reach 89.2%, oil content lower 93.55% and its viscosity retention rate reach 88.89% after dealing with which can re-injection or re-use with polymer injection.
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