Abstract: The solid-liquid interface characteristics of oil, water and rock are critical to the imbibition behaviors of tight and shale reservoirs. Especially for the imbibitionsystem with ultralow interfacial tension and solubilization and emulsification effects. It is urgent to clarify the relationship between the interface action mechanism and imbibition behaviors. This paper is a case study of tight reservoirs in Member 7 and 8 of Yanchang Formation and shale reservoirs in Longmaxi Formation; five typical imbibition fluids were developed, including simulated formation water, basic surfactant (AES), surfactant system that can form nanoemulsion(nE-S), prefabricated nanoemulsion containing oil shell (nE)and in-situ microemulsion (mE-FS), and a systematic and deep study was carried out on interface interaction, physical simulation of imbibition, normalized recovery model, scale equation and imbibition mathematical model. The results indicate as follows.(1)mE-FS is characterized with solubilization ability and ultralow interfacial tension, and thus can significantly improve the rock surface wettability and imbibition recovery; (2)The recovery ratio of imbibition fluids is ranked as follows:mE-FS>nE>nE-S>AES>simulated formation water; (3)mE-FS imbibition recovery is linearly correlated with core permeability, i.e., the lower the permeability, the poor the imbibition effect; (4)A dimensionless time scale model with a wide range of application has been established by taking into full account interfacial tension and wettability changes; (5)Solubilization coefficient is introduced into the imbibition theory mathmatical model to establish a linear relationship between imbibition distance and time of imbibition fluids with different interface properties.