A multiscale study of the coupling effects of H₂S impurity and dissolution reactions on convective mixing in CO₂ geological storage

In the present work, a multi-scale study of density-driven flow in CO₂ geological storage coupled with H₂S impurity and solid–liquid chemical reactions is conducted. Linear stability analysis is first performed to predict the initial interfacial instability at Darcy scale. The nonlinear simulations based on the lattice Boltzmann method (LBM) are further conducted to capture more information of the long term mixing behaviors at pore scale. The results of theoretical analysis and numerical simulations demonstrate that the miscible interface stability and convective mixing processes are determined by the competition among the gravitational instability and the reaction-infiltration instability. As the chemical reaction intensifies, the system gradually becomes dominated by reaction-infiltration instability from gravitational instability. The presence of H₂S could suppress the gravitational instability but enhance the infiltration instability, thus, it has completely different effects under slow and fast reaction conditions. This investigation could improve our understand for the coupling effects of CO₂ and H₂S on the miscible interface stability and density-driven convective mixing process, which is significative for engineering of geological storage of CO₂.