Analysis on correlation and adaptability of factors affecting polymer flooding efficiency

Polymer flooding is a complex and systematic project with multiple targets. To sort the influence factors in sequence is valuable to implement and adjust the polymer flooding. By regarding the polymer flooding as a gray system, the gray correlation analysis method is used to analyze the effect of various factors on polymer flooding, as a result, the main factors affecting the polymer flooding is identified. Statistics is taken on the development effect of eight polymer flooding blocks in Henan Oilfield. The permeability variation coefficients are selected, and nine factors including the formation pressure are identified as the dominant ones. Based on the analysis, the factors are sorted in a descending order: the injecting rate, the formation pressure, the permeability variation coefficient, the formation water salinity, the injection pore volume, the size of broken plug, the permeability, the oil viscosity, and the water cut before polymer flooding. A series of conceptual models are established for the analysis of the adaptability of the polymer flooding. It is shown that the oil recovery based on polymer flooding increases more slowly as the injecting rate increases. The polymer flooding response changes at the specific polymer effective viscosity, and the polymer flooding reaches its best response when permeability variation coefficient equals 0.7.