We conducted a pore network modeling study of the influence of different fluid and rock properties on gas migration under the influence of gravitational forces. Transitions from continuous, capillary-dominated flow, through gravitationally biased fingering and discontinuous braided migration, to discontinuous dispersive (bubbly) flow were investigated using both small-scale (1-cm) and macro-scale (100-cm) networks. Our simulation results were found to closely match a wide range of published experimental observations and the model is the first to comprehensively explain the influence of several pore-scale properties on buoyancy-driven migratory patterns. We found a transition from continuous, compact, capillary-dominated flow to discontinuous “dispersive” flow as the relative strength of buoyancy forces increased. We found that the governing regime is strongly affected by the mean capillary radius, pore-size distribution variance, gas–liquid interfacial tension, and the underlying connectivity of the porous medium. We also investigated the implications of these system properties and associated boundary conditions for air sparging efficacy.

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