Experimental investigation of surfactant enhanced spontaneous imbibition in Chinese shale oil reservoirs using NMR tests

Surfactant enhanced spontaneous imbibition is an effective method to enhance oil recovery in shale reservoirs, however the mechanism is still unclear. This work attempts to investigate the effect of added surfactants on the spontaneous imbibition into shale rocks using NMR tests. Contact angles and IFT are measured to evaluate the efficiency of different surfactants in terms of wettability alteration and IFT reduction. According to the experimental results, the studied anionic surfactants perform better on the wettability alteration of shale rocks than studied nonionic surfactants, and the key factor to enhance the shale oil recovery may be wettability alteration.