Study on micro remaining oil distribution of polymer flooding in Class-II B oil layer of Daqing Oilfield

During the implementation of chemical flooding, problems of slow decline of water cut and poor development effect appear in Class-II B oil layer of Daqing Oilfield. In this paper, photoetched glass models and micro CT-scanner technology are used for polymer flooding experiment with different molecular weight. Experiment are carried out by parallel displacement method to simulate the effect of interlayer heterogeneity on the residual oil distribution. The results of photoetched glass model displacement experiment show that under the condition of parallel displacement, the enhanced oil recovery of low permeability model is the largest when the molecular weight of polymer solution is 1900 × 104 Da, and the overall displacement efficiency is the best. However, the compatibility between polymer solution with molecular weight of 2500 × 104 Da and low permeability model is poor. The variations in cluster residual oil saturation is lower in low permeability model, whereas other types of residual oils are higher. Micro CT-scanner results show that there is almost no membrane and blind end residual oils after polymer flooding, which validates the low utilization ratio of membrane and blind end residual oils saturation in photoetched glass model.