| Polymer flooding has been commonly used in enhanced oil recovery technology during high water cut development period in oil field. Research members domestic and abroad on tertiary oil recovery have proved that polymer solution is a kind of viscoelastic fluid by using numerical simulation, physical simulation, and NMR technique. The existing results show that: Polymer flooding can enhance oil recovery not only by enlarging swept area but also by enhancing oil-displacing efficiency through its viscoelasticity.Therefore, it is necessary to have deep-going research on rheological properties of polymer solution in its flooding process, enrich the existing oil displacement mechanism of polymer flooding, and on this basis we can optimize and improve the current polymer flooding program, tap the latent of remaining oil. as much as possible in polymer flooding, improving ultimate recovery and extending oil fields's life.Most of the current block of Daqing Oilfield has entered ultra-high water cut or polymer flooding stage, some of these are even close to the end of polymer flooding,how to carry out follow-up development has become a serious problem. The scheme of high concentration and high molecular weight polymer flooding aiming at P I 1-2 oil layer in the sixth oil production factory of Daqing Oil Field is proposed based on past water flooding and polymer solution flooding develop experiences, laboratory experiment and field test.In this paper, the following main tasks were carried out: the study of the rheology of high concentration polymer solution through theoretical analysis and instrumental detection methods, the study of factors influencing viscoelasticity of polymer solution such as polymer concentration,molecular weight ,shear rate based on polymer solution's rheology,and the laboratory physical simulation experiment such as Seepage Characteristic and oil displacement experiment.The experimental results show that:Polymer solution has a viscoelasticity and elastic effects should be higher than the viscous effect; The better the water quality ,the higher the polymer concentration and molecular weight,the better will the polymer's viscoelastic property be; The injection of high concentration and high molecular weight polymer solution is feasible; On reservoir cores with K 1000×10-3μm2,the polymer solutions prepared in fresh water( mother liquor )with 5000mg/L can be used on the base that it can be injected,however,lower concentration of polymer polymer solutions prepared in fresh water or high concentration polymer solution prepared in produced water should be used if problems sunch as economic investment and disposal of sewage must be in consideration; At different combinations injection programs for oil layers with K 1000×10-3μm2 and 1700×10-3μm2, displacement effects is good when the first plug has a high concentration which indicates that high concentration of pre-slug of polymer assured plugging lager cores effectively, making following slugs transferd to flooding remaining oil of smaller cores Oil Displacement Efficiency of combination injection model in two different level penetrate rate core are both not ideal,even worse than that only polymer injected which is because that the cores used for combination injection model experiment are homogeneous, causing the faileure of combination injection's control effect, further study should be carried out on mechanism of this and exploring of combination injection model that is properd to homogeneous core.
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