Abstract: In Gudong oilfield, after enhanced water injection and enhanced production over ten years, the water cut of main development units has risen as high as 95%. In order to reduce water cut and increase the oil output, a polymer flood pilot experiment in industrial scale has been carried out in the field. for five years since 1994. In view of characteristics of the oilfield such as the relatively simple structure, the unique pay zone, high heterogeneity, loose cementation of pay zone, good lithophysic properties, high viscosity of crude oil, high salinity of formation water, etc., a two-stage plug injection plan has been designed on the basis of laboratory study and numerical simulation. After inplementation, the plan obtained evident results: the water cut of oil wells decreased by 5.6% in average, oil production rate increases by 326 tons per day, and it is expected total ultimate recovery may increased by 6.5%, so the economic benefit is significant. All problems which occurred during the experiment are settled by adopting corresponding measures. The successful pilot experiment has shown bright future for larger scale application of polymer flood in shengli oilfield.

Key words: Gudong oilfield, polymer, recovery factor, industry, experiment