Diffusive and Convective Mechanisms during CO2 Sequestration in Aquifers

Abstract

CO2 emissions originated from industrial sources can be captured, transported, and stored in depleted gas/oil fields and deep saline aquifers. The transport mechanisms, occurred during CO2 sequestration in deep saline aquifers, are examined in this study. After injecting CO2 until the tolerable pressure for the aquifer is reached, the wells are closed and CO2 is deposited as free gas and soluble gas in water under the sealing rock. During injection and waiting periods, the concentration profile of CO2 within the aquifer is formed by diffusion and convection mechanisms. The Rayleigh number and mixing zone length concepts are used for investigating the effect of reservoir properties, such as dispersivity, permeability, porosity, and others on the aforementioned mechanisms. The results of convective dominant mechanism in aquifers with 1 md and 10 md permeability values are so near in that diffusion-dominated system. After 10 md, the convection mechanism begins to dominate gradually and it becomes totally convection dominated for 50 md and higher permeability values. These results are also verified by the Rayleigh number and mixing zone lengths.