Pore-level foam generation, propagation, and sweep efficiency were visualized using silicon-wafer micromodels with an accurate representation of sandstone pore structure, grain shapes and sizes based on thin-section analysis. Foam generation by snap-off was observed both in the interior of the porous network (rectilinear snap-off) and at permeability discontinuities between fracture and porous matrix. Lamella creation by the two snap-off mechanisms identified here resulted in different foam textures. During foam injection for enhanced oil recovery, microvisual data revealed that the aqueous phase advanced as film flow along water-wet grains whereas discontinuous gas bubbles were located in the center of pores. Foam injection significantly enhanced sweep efficiency in fractured systems in terms of greater pore occupancy by gas and larger contact area with displaced fluid compared to continuous gas injection.