Research on the mechanism of "fluid entry profile reverse" during polymer flooding

Polymer flooding has been widely applied in China,and has made a great contribution to EOR. However,in some blocks with relatively severe heterogeneity,the phenomenon of "the reverse of fluid entry profile" has occurred,that is the high permeability zone absorbs more than in water flooding stage,while the middle and low permeability zones absorb less than in water flooding stage. Physical experiments have been conducted to study the factors affecting oil recovery efficiency. The results show that reservoir permeability contrast,relative molecular weight of polymer and the injection time of polymer solution will all have impact on the phenomenon of "the reverse of fluid entry profile". This study is helpful to improving displacement efficiency of polymer flooding.