Scaling Analysis of the Convective Mixing in Porous Media for Geological Storage of CO2: An Experimental Approach

Abstract

Prediction of the behavior of convective mixing and the effectiveness of this mechanism is essential for permanent sequestration of CO2 in deep saline aquifers. Simulation of the diffusion–convection mechanism at a large scale is very expensive and time-consuming; therefore, scaling relationships can be used to find suitable candidates for storage sites. In this study, scaling analysis is performed for the convective mixing of CO2 in saline aquifers based on experimental results. The scaling relationships are presented for the prediction of convective dissolution behavior. In the presented scaling analysis, different systems with a wide range of Rayleigh numbers were used. All experiments were conducted in a dissolution cell with different ranges of grain sizes. The pressure decay data are used to determine the dissolution rate of CO2, Sherwood number, and convective flux. In addition, the fraction of ultimate dissolution is calculated for each experiment to investigate the mixing regimes (convective mixing and diffusive mixing). The results indicate that the mixing of CO2 in water can be approximated by a scaling relationship for the Sherwood number and convective flux. These relations can be used in the implementation of large-scale CO2 storage in deep saline aquifers.