In view of the characteristics of high salinity of injected water,high reservoir temperature and multiple reservoir layers in Block G of Dagang K Oilfield,experiments were conducted to screen temperature⁃resistant and salt⁃tolerant polymers and surfactants.On this basis,the oil displacement efficiency of polymer solutions and polymer⁃surfactant binary composite flooding systems(hereinafter referred to as polymer/surfactant binary flooding systems) was investigated using multi‐layer core models.The results show that among the three types of polymers,hydrophobically associating polymers exhibit superior viscosity enhancement. Compared with HSY and DWS,the polymer/surfactant binary flooding system formulated with DG‐1 surfactant can reduce the interfacial tension to 10⁻³ mN/m.Under the same model layer combination,the incremental oil recovery of the polymer/surfactant binary flooding system is higher than that of the polymer solution;in particular,the incremental oil recovery of the binary flooding system is 1.43% higher in the three‐layer model with a permeability ratio of 10. Under the same flooding agent condition,the mass fraction and viscosity of polymer and surfactant in the produced fluid increase with the increase of model permeability ratio.At the same permeability ratio,a larger number of model layers leads to higher waterflooding recovery,lower chemical flooding and subsequent waterflooding recovery,while the ultimate oil recovery is similar.
