Experimental study of density-driven convection effects on CO₂ dissolution rate in formation water for geological storage

Permanent storage of CO₂ in saline aquifers is known as one of the best methods for carbon dioxide sequestration. Understanding the role of convection in CO₂ dissolution of saline aquifers - which affects the long-term fate of the injected CO₂ and the security of storage - is extremely important. In this paper, two types of experiments are performed; first, visualization experiment in Hele-Shaw cell and second, quantitative experiments at elevated pressure. These experiments are used to investigate the effect of Density-Driven Convection (DDC) on CO₂ dissolution rate in saline aquifers. For this aim; first, visualization test is performed in a Hele-Shaw cell to observe convective instabilities and its effect on dissolution rate. Afterward, quantitative tests are performed, in which four parameters are calculated: Total Dissolution, Diffusion Dissolution (DD), Convection Dissolution (CD), and CO₂ Convective Flux (F_CO2). Through employing these parameters, the behavior of convection and its effects on CO₂ dissolution rate based on the scaled experiments is shown, and two scaling relationships one between Rayleigh and Sherwood number and the other one between CO₂ Convective Flux and Rayleigh number are developed. Such scaling relationships provide an estimation of the maximum convective dissolution of CO₂ in saline aquifers which would be useful for assessing suitable CO₂ storage sites.