Ponentes
Descripción
Geological Carbon Capture and Storage (CCS) has emerged as one of the most promising technologies for mitigating anthropogenic CO₂ emissions. Among the available geological formations, deep saline aquifers offer large storage capacity and broad geographical distribution. In these systems, solubility trapping plays a fundamental role by enhancing the dissolution of CO₂ into the resident brine, thereby increasing storage security and reducing the risk of buoyancy-driven leakage. The efficiency of this mechanism depends on density-driven convective instabilities that develop after CO₂ dissolution, producing descending fingers that enhance mass transport. However, most numerical studies assume a fixed and planar CO₂-brine interface, neglecting its possible evolution during the dissolution process. This work investigates the influence of interface motion on convective CO₂ dissolution through numerical simulations of density-driven flow in porous media. The mathematical model is based on the dimensionless Darcy-Boussinesq equations coupled with a concentration transport equation. A pressure-concentration finite element formulation is adopted, while the moving boundary is handled through an Arbitrary Lagrangian-Eulerian (ALE) framework that allows the computational mesh to follow the interface evolution according to a kinematic condition. The numerical implementation was developed in the Julia programming language and verified against the analytical solution of the purely diffusive problem, demonstrating second-order spatial convergence. The moving-interface formulation is compared with the classical fixed-interface configuration. The results show that interface motion substantially modifies the evolution of the convective instability. The onset of buoyancy-driven fingering occurs earlier than in the fixed-interface case, leading to a faster transition from diffusion-dominated transport to the convective regime. Furthermore, the moving interface produces a higher dissolution-flux plateau and a larger average mixing length, indicating enhanced solute transport within the brine. The concentration fields reveal that interface deformation promotes the coalescence of fingers into preferential descending pathways while simultaneously creating regions where convection is locally suppressed. These changes alter the spatial organization of the instability and significantly affect the overall dissolution dynamics. The results demonstrate that interface dynamics should not be neglected when modeling convective dissolution in geological carbon storage applications. By providing a more realistic representation of the CO₂-brine interface, the proposed formulation improves the understanding of the physical mechanisms governing solubility trapping and offers valuable insights for the development of more reliable predictive models for CCS. The study highlights the importance of advanced numerical methods with moving boundaries for simulating environmental fluid flow problems involving coupled transport and evolving interfaces (Lucena, R., Pontes, J., Brau, F., De Wit, A. & Mangiavacchi, N., Advances in Water Resources 197, 104904, 2025).