Spontaneous Imbibition and Oil Displacement Experimental Investigation in Fracture–Matrix Cores of Tight Sandstone Reservoirs

Tight sandstone reservoirs are characterized by low porosity and low permeability, which results in great difficulty in oil production and low recovery. In this work, based on fractured–matrix tight sandstone core models and field crude oil, the interfacial activity and reservoir adaptability of the oil displacement agent C-22 were evaluated. Subsequently, oil displacement agents with different interfacial tension levels were optimized and selected as control groups for subsequent oil displacement experiments. The migration behavior of crude oil in fractured–matrix cores during spontaneous imbibition and oil displacement processes using C-22 was systematically investigated, and the key development parameters for oil displacement were further optimized. The results show that C-22 exhibits excellent interfacial activity and good reservoir adaptability. An ultralow interfacial tension of 0.12 mN/m can be achieved at a concentration of 0.1 wt%, and the interfacial tension remains stable after 7 d of aging. In the oil displacement experiments, as the pressure decreases from 15 MPa to 0 MPa, the final oil recovery reaches 18.94%. Nuclear magnetic resonance analysis indicates that oil in mesopores and macropores is predominantly mobilized at the early stage, whereas oil in micropores is mainly produced at the later stage. Furthermore, the key development parameters for the oil displacement process were optimized. The optimal oil displacement performance is achieved when the interfacial tension is reduced to the 10 ^− 2 mN/m level, the concentration of C-22 is 0.2 wt%, and the shut-in time is 12 h. We expect that this study can provide valuable insights into the effective development of tight sandstone reservoirs and offer theoretical guidance for the selection of field operational parameters.