Pore-scale visual investigation on the spontaneous imbibition of surfactant solution in oil-wet capillary tubes

Surfactant assisted spontaneous imbibition is a feasible method for enhanced oil recovery in the reservoirs. A series of pore-scale visual spontaneous imbibition experiments of surfactant solution in oil-wet capillary tubes with six different diameters (10 mu m similar to 60 mu m) are thoroughly investigated. The results showed that the final imbibition recovery exhibited a rise and fall tendency in sequence with the increase of capillary tube diameter. The combination of the Marangoni effect and diffusion effect was the dominant power to render the oil be expelled, and the wettability alteration was principally conducive to the migration of expulsion oil. Additionally, emulsification entrainment was beneficial to imbibition recovery.