CO₂ Plume Migration With Gravitational, Viscous, and Capillary Forces in Saline Aquifers

In this study, we attempt to consider three forces of gravitational, viscous and capillary forces, simultaneously when CO₂ is injected in saline aquifers. In order to conduct it, we propose a dimensionless group in the form of combination of Capillary number and Bond number. This dimensionless group is a function of CO₂ saturation, in which the pattern of CO₂ flow regimes can be determined. By the analysis of the acquired each trapping mechanism from flow regimes, optimum CO₂ injecting scheme can be designed for maximizing the solubility and residual trappings as stable mechanism. With utilizing the proposed dimensionless group, we conducted several numbers of simulations using 2D vertical heterogeneous system with respect to CO₂ flow rate, interfacial tension between CO₂ and water, and brine salinity. From the simulation results, when gravitational and viscous forces with respect to capillary force are described by two individual dimensionless groups of Capillary number and Bond number, CO₂ saturation profiles are variously generated. These are not satisfactory correlations in the dependence of CO₂ saturation on Capillary number and Bond number for the variable terms of density differences between CO₂ and water and CO₂ injection rates. With the proposed dimensionless group, the universal profile of CO₂ saturation was obtained in describing CO₂ flow behaviors for the variables. Thus, considering two variables of density differences and CO₂ injection rates simultaneously, that is, when three forces considering at the same time, more realistic CO₂ flow behavior can be analyzed. This study helps to determine the most secure conditions of CO₂ injection and storage according to building the pattern of CO₂ flow regimes which is classified by the range of a dimensionless group.