Impact of intrinsic layered heterogeneity on CO2 convective-reactive dissolution in saline aquifers

The heterogeneity of saline aquifers significantly influences CO 2 dissolution efficiency and convective-reactive transport dynamics, which still remains insufficiently understood. To address this knowledge gap, this study systematically evaluates the effects of three intrinsic layered heterogeneities (i.e., porosity, permeability, and reactant content) in saline aquifers on both the convective mixing behavior of CO 2 plumes and the chemical dissolution of CaCO 3 . These investigations are conducted using a newly developed convective-reactive transport model. The results demonstrate that, compared to homogeneous aquifers, layered heterogeneity with decreasing porosity or reactant content significantly enhances CO 2 convective-reactive transport, leading to faster CO 2 full mixing with brine and complete CaCO 3 dissolution. In contrast, increasing porosity or reactant content with depth exhibits a negative effect on CO 2 dissolution efficiency. Permeability layered heterogeneity in aquifers inhibits CO 2 convective-reactive dissolution compared to homogeneous aquifers. Distinct CO 2 -plume migration patterns emerge in different layered heterogeneous saline aquifers, primarily characterized by fingering, channeling, and compaction flow regimes. Additionally, the results also suggest that the evolution of Da number during CO 2 dissolution process can be adopted to evaluate the CO 2 dissolution efficiency. The findings of this work can provide a reference for screening the heterogeneous saline aquifers suitable for efficient CO 2 dissolution. • Porosity/reactant decreasing-layered heterogeneity accelerates the CO 2 dissolution. • Permeability-layered heterogeneity delays the CO 2 convective-reactive dissolution. • Varying developing patterns of CO 2 plume are observed in different saline aquifers. • A synthetical index is proposed to select the saline aquifers for CO 2 dissolution.