Pore-scale two-phase filtration in imbibition process through porous media at high- and low-interfacial tension flow conditions

This study provides new insights into pore-scale two-phase filtration during imbibition process through porous media under the high- and low-interfacial tension (IFT) flow conditions. First, the distribution and configuration of imbibing wetting and non-wetting phases in primary imbibition (free spontaneous imbibition or wetting process) is depicted. Second, the detailed pore-scale topology, structure, distribution, and configuration of different phases together with the pore-scale displacement mechanisms in primary drainage (i.e., desaturation of continuous wetting phase or de-wetting process), secondary imbibition (i.e., controlled spontaneous imbibition or desaturation of continuous non-wetting phase in high-IFT flow condition), and tertiary imbibition (i.e., forced imbibition or mobilization of discontinuous trapped non-wetting phase in low-IFT flow condition), are expounded. Finally, the advance of the displacement front and flow pattern configuration in secondary and tertiary imbibition is demonstrated and discussed. Furthermore, in tertiary imbibition, the blob size distribution of the displacing wetting phase, formation of the secondary displacement front and wetting film before breakthrough of the displacing wetting phase, rate-dependency of the advance of secondary displacement front and wetting film, interruption of the wetting film flow within wetting film region, pore-level phenomena within the wetting film region, and role of wetting film in pore-scale displacement mechanism are elucidated.