Polymer flooding has been widely used in the development of offshore oilfield as its significant EOR performance, which can achieve high oil recovery during the short service life of offshore platform. Effectiveness evaluation is an important aspect in polymer flooding application, and the results will affect the adjustment of polymer flooding. However, there is not too much study focusing on this field until now.

In this paper, an evaluation model was developed to estimate the effectiveness of polymer flooding. The response characteristics of polymer flooding were studied by the core flooding experiments. The comparison experiments of water flooding and polymer flooding were conducted to investigate the dynamic performance of production parameters during the flooding process. The results showed that the most significant performance is the "U" shape of water cut curve which indicate the effectiveness of polymer flooding. It also can be observed that the injection pressure and the oil recovery will increase when polymer flooding works, and their variation ranges have positive correlation with the effectiveness of polymer flooding. To get more details of geology and production parameters affect the polymer flooding effectiveness, numerical simulation model was built based on the data of Bohai oilfield. The influences of eight optimized parameters on polymer flooding effectiveness were studied by numerical simulation. Parameter sensitivity analysis was conducted by grey correlation method and the rank can be obtained according to the influence of each parameter on polymer flooding effectiveness. The results showed that mobility ratio, permeability variation coefficient and injection time are the top three parameters which indicate that they have more important influence to polymer flooding effectiveness. Then a multi-parameter response system was developed to describe the relationship between eight parameters and polymer flooding effectiveness. Consequently, a comprehensive effectiveness evaluation model was built which include the response characteristics summarization, parameter sensitivity analysis and multi-parameter response system evaluation. The effectiveness of polymer flooding can be evaluated and its key influence factors can be obtained by this model. It has been used in the evaluation of polymer flooding in Suizhong 36-1 well group in Bohai offshore oilfield in China, with inaccuracy of 7.83%.

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