Study On Recycling Of The Polymer-flooding Wastewater Treatment With Ion Exchange Membrane Process

Polymer flooding process is one of tertiary oil extraction technologies. It has stepped into industrialization application period in recent years. It plays an increasingly important role in the oil exploitation, but a lot of polymer-flooding wastewater is produced per day with oil extraction together. Therefore, the treatment and reuse of wastewater becomes very significant. Experiments show that the polymer-flooding wastewater can replace fresh water to be reused to confect polymer solution after removing TDS (total dissolved solids) by electrodialysis technology. By status of the pilot-test electrodialysis equipment installation and operation in Daqing oilfield, the optimal operational conditions and removing rate of the main ions were confirmed and studied respectively, and the energy consume analyse and feasibility research were carried, which provided experimental data for using electrodialysis technology in oil-field wastewater treatment.At present, serious ion exchange membrane fouling (especially for anion membrane) is the main problem that holds back this technology's further application. Therefore, a small-scale 5-compartment electrodialysis was developed to study the effect of main fouling substances of polymer-flooding wastewater (solid suspension, crude oil and polymer) on the performance and apparent characteristics of anion membrane from microcosmic (membrane surface resistance, average current, and desalination rate, etc.) and macroscopical (Scanning Electron Microscope and atomic force microscope) views respectively, which can resolve the key problem of reducing TDS in the polymer-flooding oil-field wastewater by the method of ion exchange membranes. The experimental results show that part of solid suspension congregated on the surfaces of, even inside, anion and cation membrane so as to produce fouling, but the influence on cation membrane is worse than on anion membrane. The polymer may congregate on the surface of anion membrane, which influences the permeation of anion membrane; the crude oil can form compact oil film on the surface of, even inside, anion membrane, which results in severe fouling, but has less influence for cation membrane. The experimental data provide theoretic basis for designing and synthesizing anti-fouling membranes.This treatment technology can not only decrease environmental pollution resulted by wastewater discharge, but also achieve closed-circuit of polymer flooding wastewater during crude oil extraction. It has significant effect for protecting environment and saving water resource.