Heterogeneity effects on gravity current migration and mixing in porous media

CO₂ sequestration is a promising method to mitigate anthropogenic CO₂ emissions. When CO₂ is injected into a saline aquifer, its buoyancy leads to the formation of a gravity current that migrates laterally, while CO₂ dissolves into the underlying brine, creating a high-density mixture that can trigger fingering instabilities. In this study, we investigate the migration of this gravity current and the mixing of CO₂ with brine in heterogeneous porous media. Heterogeneity is modeled using horizontally stratified media and multi-Gaussian log-normal permeability fields, characterized by the variance of the log-permeability and its correlation length. We examine how heterogeneity influences the time-evolution of the gravity current and CO₂-brine mixing by analyzing factors such as dissolution fluxes, residual buoyant mass, the length of the CO₂-brine interface, interface width, and mixing volume. Additionally, we explore the impact of different Rayleigh numbers, correlation lengths, and variances on mixing behavior. Our findings aim to enhance the understanding of CO₂ storage in geological formations.