Study On Nitrogen Foam Flooding In Uniform Mobility For EOR After Polymer Flooding

Polymer flooding has been an important enhanced oil recovery method adopted at the later stage of oilfield development in China. However, due to the effect of reservoir heterogeneity, there is still about 40%-50% remaining oil kept in oil-bearing formation after polymer flooding, and how to further enhance recovery factor after polymer flooding and keep the oil-field sustained development has become the focus of research at present. This paper develops the technology of nitrogen foam flooding after polymer, and nitrogen foam flooding technology of is an effective improved oil recovery method for heterogeneous reservior at the later stage of development, and a series of studies and field experiments has been done in recent years. But it is at development stage and needs deep study in mechanisms of foam flow in porous media, influential factor and applicability. Wherefore, it is very necessary to further study the foam flow in heterogeneous reservoir and the effect of foam flooding after polymer flooding.Based on foamer's foaming ability and stability, through laboratory experiment, several foamers used in oil field were evaluated through experiment, and affecting factors of foaming ability and stability is analysed. Through homogeneous physical model, the effects of gas-liquid ratio, permeability, injection rate and oil saturation on nitrogen foam flow law in porous media were studied systematically.Using uniform design, the effects of gas-liquid ratio, permeability, injection rate on resistance factor are studied comprehensively and the relationship of resistance factor is established.Through simulating heterogeneous reservoir with different permeability contrast, the displacement process of foam flooding after polymer flooding is experimental studied, and the effect on mobility regulatory of foam in heterogeneous reservoir caused by permeability contrast is analysed. Through simulating heterogeneous reservoir with oil saturation distribution, the effect on mobility regulatory of foam in heterogeneous reservoir caused by oil saturation distribution is analysed. Through simulating major reservoir of Daqing oilfield, the displacement process of multislug foam flooding is experimental studied, and the result indicates that injecting advancely accordant viscosity slug can effectively resist gas breakthrough in high permeability zone,and can more effectively adjust mobility contrast of foam in heterogeneous reservoir.With the nuclear magnetic resonance technology, the paper researches the distribution area of bore diameter in which oil is sweepouted of polymer flooding and foam flooding under different processes and various heterogeneity conditions.