Pore-scale investigations of particle migration by fluid–particle interactions in immiscible two-phase flow systems: A three-dimensional X-ray microtomography study

• Particle migration in pore-scale two-phase flow systems was visualized using X-ray CT. • The effects of interfacial tension and viscous force on particle migration were investigated. • Interface expansion strongly induced particle migration compared with film formations. • The 3D structures of injection fluid for two-phase flow systems were investigated. Understanding of particle migration by fluid–particle interactions in immiscible two-phase flow systems in porous media is crucial for subsurface applications. However, pore-scale investigations of particle migration in immiscible two-phase flow systems remain limited for three-dimensional (3D) porous media because of the complexities of fluid flow in such media. Here, we employed microfocus X-ray computed tomography (CT) to investigate the effects of interfacial tension and viscous force on particle migration during fluid–particle interactions in strong drainage and imbibition for the pore-scale process. A mixture of two differently sized particles was used as a 3D heterogeneous porous medium. The experimental conditions cover the logarithmic values of the capillary number (Log Ca ) range between −7.476 and −4.777 and of a fixed viscosity ratio (Log M ) of −0.867, which are used to simulate the carbon dioxide (CO 2 ) sequestration. The results show that particle migration significantly proceeded throughout the medium for strong drainage compared to strong imbibition. At a low injection flow rate or Log Ca , interfacial tension strongly influenced particle accumulation, altering pore networks. The combined effects of interfacial tension and viscous force enhanced particle migration with an increase in Log Ca . In strong drainage, the particles migrated with the interface expansion between the two phases. However, in strong imbibition, they were displaced along with the fluid flow because of the presence of film formations. The findings of this study improve the understanding of particle migration by fluid–particle interactions under different injection flow rates and wettability conditions in 3D heterogeneous porous media.