Abstract:Taking the low permeability tight reservoir of Chang 6 as the research object, two self-made surfactants S1 (with strong modification wettability) and S2 (ultra-low interfacial tension) with different interfacial properties were selected. Their static and dynamic permeability effects were characterized by NMR, and their oil displacement process was studied by 2.5-dimensional micro model, The EOR effect and mechanism of surfactants with different interfacial properties are analyzed. The results show that both S1 and S2 have good enhanced production effects. Imbibition is a process in which water enters small pores to replace oil to large pores. Surfactants can greatly promote the production of small pores; During oil flooding, the dominant channel is obviously formed, which can realize wettability reversal, and has additional imbibition effect, which greatly increases the sweep volume and oil washing efficiency, and can disperse the crude oil into small scale state. Among them, the S1 capillary with stronger wettability ability is more powerful and has a higher degree of mobilization of small holes, but the recovery rate is slower, but the additional imbibition during displacement is stronger, which can achieve ultra-low interfacial tension.The S2 with ultra-low interfacial tension can achieve smaller oil phase flow resistance, faster imbibition speed, and faster recovery to reach equilibrium.