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.

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