Investigation on EOR by composite surfactant-polymer (SP) flooding and streamline adjustment through well pattern encryption: A case study of Shengli’s strong heterogeneous reservoir

• The experiments utilized a hyper-scaled 2D physical model. • The formation of oil bank was captured using the electrical resistance method. • The synergistic mechanism of agent-network was explained by streamline method based on numerical simulation. To clarify the oil displacement mechanism of composite Surfactant-Polymer (SP) flooding under strong heterogeneous reservoirs, the well pattern was further encrypted to improve the well pattern utilization. First, a larger 2D physical model was established to simulate composite SP flooding under strong heterogeneous permeability conditions. Second, the locations and timing of infill wells were determined by analyzing the dynamic of the oil bank. Then, the synergistic effect experiment of composite SP flooding and well pattern encryption was carried out. Finally, based on the results of the physical simulation experiments, a numerical model of a real oilfield was used to predict the field application effect. The results show that there was still a large amount of residual oil, oil-bank, existed in the inter-well area after the composite SP flooding. If the infill wells were arranged in inter-well and opened after the pre-slug injection, the residual oil and oil bank was displaced to improve oil recovery factor. The field numerical simulation results show that opening the infill well after the pre-slug injection was indeed the most effective way to enhance oil recovery. The excessive production of high permeability production well was suppressed, and the uneven sweep of the displacing phase in the strong heterogeneity area was improved. The work can provide a theoretical basis for improving the recovery factor of chemical flooding in strongly heterogeneous oil reservoirs.