LAUSR

Abstract The Rayleigh convection induced by dissolved CO2 in saline aquifers is significant for CO2 permanent storage. In this paper, the lattice Boltzmann method (LBM) with external forces was established to simulate such the convection in NaCl, KCl, MgCl2 and CaCl2 solutions. The simulation was performed in two kinds of conditions, the one was the same concentration of salt, and another was the same concentration of Cl-, at 298.15 K, 1.00 atm. The results showed that the order of convection appearance in four salt solutions was: KCl＞NaCl > MgCl2>CaCl2 in 1 mol·kg-1 (M) salt solution. However, it was a little different in the condition of the same concentration of Cl-, the order was: KCl > MgCl2>CaCl2>NaCl. This was mainly because a bigger density difference between brine and CO2-saturated solution could enhance convective instability. The magnitude of convective velocity and mass transfer rate was 10-5 and 10-6 m∙s-1, respectively. Furthermore, the mean dissolution rate was around 2 times larger than that at the onset of convection. In addition, we found that the onset convection would be delayed as salt concentration increased. Our results have a practical guidance for a further experimental design and industrial application on CO2 geological separation in saline aquifers.