It was proposed that the advanced⁃treatment of polymer⁃flooding produced water and realized the re⁃injection requirements. The feasibility and potential of further deep filtration treatment of wastewater containing polymer after ordinary treatment were studied by numerical simulation. The available advanced⁃filtration process pattern was established and optimized based on the distribution of oil droplets and suspended solid particles, the concentrations oil and suspended solid in filtered water, and the removal rates of oil and suspended solid. The results indicated that the advanced⁃filtration process pattern with "double graded⁃media + three graded⁃media" could further improve filtration performance depended on hydraulic and interfacial effects. The removal rates of oil and suspended solid reached 87.78% and 87.11%, respectively. The oil content and suspended solids of filtered water were controlled within 5 mg/L required for deep water treatment. This is a potential filtration process model for advanced treatment of polymer⁃containing wastewater, and also provides a basis for effectively dealing with water quality problems in tertiary oil recovery by chemical flooding in oilfields.

Granular layer filtration is widely used in the treatment system of oilfield produced water, and water distribution of granular layer filter which directly affects the purification effects of produced water plays the same significant role as the selection and arrangement of granular layer. The model of filter was built and unstructured grids were generated by Gambit. The flow rate field in the model was calculated by Fluent combined with DPM model. Based on the DPM model in Fluent software, a numerical simulation of pressure field distribution, filtration pressure drop along the axis, pathlines of particles, and particles distribution and aggregation behaviors were simulated and calculated. Then, water distribution characteristic in pressure filter of produced water was described, and optimization of water distribution process was realized. The results showed that the good performance of water distribution was obtained and the pressure drop in the filter with sieve tubes was reduced by 30.56% compared with the filter with slots. Furthermore, the filter with nine sieve tubes was optimized by its excellent water distribution characteristic. Such a numerical simulation method can provide effective support for optimization of filtration process and purification of produced water.