In the process of immiscible displacement of a receding fluid by an invading fluid in a porous medium, one or more pores may be bypassed by the invading fluid as it advances into the medium, leaving behind some disconnected or isolated fluid clusters trapped in the porous medium. Knowledge of the morphology, distribution and mobilization of the trapped fluid clusters is required in many environmental and engineering applications, such as enhanced oil recovery or designing efficient remediation schemes for the contaminated sites by petroleum-based products. Besides, in practice, the contribution of the discontinuous phase can be economically very important, since during oil displacement, a part of it may be trapped in the reservoir, forming a discontinuous phase in the swept zone that may occupy a significant portion of the pore space even after secondary oil production. We combine simulation results obtained by state-of-art numerical tools such as OpenFoam and Lattice Boltzmann simulation with experimental data obtained by microfluidics or 4D pore-scale imaging to investigate the dynamics of phase entrapment during immiscible multiphase flow in porous media as influenced by the injection rate, particle size distribution, gravity, physical and chemical properties of the fluid, and wettability of the medium among other factors.
Figure caption. Non-wetting fluid distribution at breakthrough time (top) in a real rock sample and three different slices along the flow direction (bottom) at various viscosity ratios of (a) M=15,(b) M=10, (c) M=1 and (d) M=1/2. The invading non-wetting and defending wetting fluids and the solid skeleton are shown in blue, red and gray, respectively (see more detail in Bakhshian et al. (2019), Sci. Rep., 9, 3377, London: Nature Publishing Group).
Figure caption. Simulation results demonstrating displacement fluid front morphologies for different values of the capillary number Ca and the pore size gradients λ at the time where the invading fluid reaches the outlet (the direction of displacement is from bottom to top). The white, orange, and black colors represent invading fluid, defending fluid, and the interface, respectively (see more details in Rabbani et al. (2018), Proc. Nat. Acad. Sci., 115(19), 4833-4838).
Figure caption. Time evolution of the simulated displacement pattern as a function of the static contact angle θ in the 2D micromodel. The direction of flow is from bottom to top. Blue, red and black indicate the invading fluid, the defending fluid and the grains, respectively. The magnified image shows a map of the pressure drop Δp = p − po where p is the pressure at each point and po is the outlet pressure, for the case θ = 120°. This magnified image indicates that there is a co-existence of concave and convex interfaces, which stems from curvature reversal at the converging and diverging sections of the pore throat (see more details in Rabbani et al. (2018), Sci. Rep., 8, 15729, London: Nature Publishing Group).