Complex displacement behavior during foaming gas drainage in 2D microfluidic networks

Foam injection, which can significantly reduce gas mobility and improve sweep efficiency, has been used as an enhanced oil recovery (EOR) technique for decades. In this work, a mechanistic pore network model is proposed to simulate foam propagation in porous media. The model includes wettability through critical pressures for pore filling events and tracks the motion of gas-water interface during foam propagation process. It also allows a quantitative assessment of the thermodynamic and flow properties of foam, such as mobilization pressure gradient, invasion morphology, and foam texture evolution.Our results show that the inclusion of wettability impacts the evolution of the capillary pressure signal, and the mobilization pressure gradient. Both increasing foam texture and reducing contact angle provide a similar effect on the invasion morphology: a transition from the regime of capillary fingering to compact displacement as indicated by fractal dimension and finger width. The effect of disorder depends on its coupling with wettability and foam texture: increasing disorder decreases the pattern compactness; decreasing contact angle or increasing foam texture smooths the gas-water interface, hence increasing compactness, leading to small sensitivity of the emergent pattern to disorder. The comparison between simulations and experiments shows that the proposed model is able to capture the relevant pore-level events that characterize the foaming gas drainage process in a microfluidic device filled with vertical posts and is reliable to be used for providing information needed for parameters in mechanistic foam simulators that are not accessible in conventional laboratory experiments.