Study on the injection capacity of polymer flooding in Bohai multi-layer oil reservoir

To evaluate the injection capacity of polymer flooding in Bohai multi-layer oil reservoir specifically, the existing mathematical model for the injection capacity of polymer flooding was modified. In this modified model, the distribution characteristics of fluid saturation in the process of non-piston like poly displacement and the effects of vertical heterogeneity of multiple oil layers in the development well pattern are taken into account. Firstly, the frontal saturation of each flow zone and its related parameters in the process of displacement are calculated according to the fractional flow theory of polymer flooding, and the water saturation distribution model for polymer flooding was established. Secondly, the expression used to calculate the seepage pressure difference between injectors and producers was derived. And finally, considering the effects of vertical heterogeneity of multiple oil layers in the development well pattern, the layered flow rate and the injection capacity were characterized, and the pseudo-three dimensional, two-phase, three-composition analytic solution mathematic model for the injection capacity of polymer flooding in multiple oil layers was developed. The calculation results are in accordance with the experimental data, indicating the rationality of this calculation method. The mathematic model established in this paper can be used to predict and evaluation the commingled and layered injection capacity of multi-layer polymer flooded oil reservoirs in different development stages and it provides a new method for evaluating effectively the injection system of polymer flooding in Bohai Oil field.