Pore level foam generation in the presence of residual oil in porous media

•Corner flow, liquid accumulation into pore throat to cause snap-off is studied from the pore-scale level.•Pores might be occupied by emulsified, trapped oil that restricts back flow of the wetting phase to cause snap-off.•In the absence of external pressure gradient, liquid accumulation times are longer when residual oil is present.•Drier pores that exhibit larger capillary pressure exaggerate the effect of residual oil on the liquid accumulation times.•The rate of generation of the lamellae is reduced as much as four times when residual oil is present.•Hindered generation in a micromodel. Snapped-off gas bubble coalesces with its neighbor because the lamellae cannot traverse snapped-off oil. The black arrow indicates the pore throat where snap-off occurs. (a) through (c) wetting fluid flow back, (d) and (e) lamella moves across the snapped-off oil in the pore body, and (f) after rupture. CO2 sequestration into depleted oil and gas reservoirs is gaining traction as one of the enablers of the energy transition. Foaming the injected CO2 has the potential to increase the amount of trapped CO2 in the porous medium. In this paper, we study the effect of trapped, emulsified oil on the requirement for the geometrical criterion for Roof snap-off in a porous medium. We extend an existing hydrodynamic pore-level model to describe the wetting-liquid accumulation in an appropriately-sized pore in the presence of oil. The effect of oil on liquid flow is simulated by adjusting the pore shape to be asymmetrical as observed in microfluidic experiments with residual oil. We alter the boundary and initial conditions of the problem to test various scenarios. Specifically, four cases are presented. The liquid accumulation is presented when the amount of wetting liquid volume connected to the pore is altered through changing the boundary conditions (cases 1 and 2). Moreover, the effect of drier surrounding medium and/or drier pores is also tested by increasing either the capillary pressure surrounding the pore or the capillary pressure of the pore itself (cases 3 and 4). We find that the presence of residual oil affects the liquid accumulation times when there is no external liquid pressure gradient applied. Additionally, residual oil presence makes the Roof snap-off criterion for liquid accumulation stricter. That is, the size of pore constrictions that allow snap off, as gauged by the ratio of throat to body size, decreases. To augment our pore-level study, we use a statist