Speaker
Description
Wormhole formation in salt deposits threatens containment integrity in geological disposal facilities (GDF) by creating preferential pathways for radionuclide migration. While continuum models predict invasion patterns, they fail to capture formation timescales due to inadequate representation of pore-scale heterogeneity and pre-existing fractures. Pore-scale reactive transport modelling can address these limitations by explicitly resolving dissolution dynamics at the pore level. We performed simulations using GeoChemFoam, an open-source OpenFOAM-based employing a micro-continuum approach. Flow is governed by the Darcy-Brinkman-Stokes equations, with local permeability following a Kozeny-Carman relationship, while advection-diffusion equations describe reactive transport of dissolved species. Dissolution kinetics at solid-fluid interfaces were handled using the improved Volume of Solid (iVoS) approach with a fully implicit reaction solver. Simulations were conducted on micro-CT imaged fractured halite samples. Results reveal two dissolution regimes: uniform face dissolution at the inlet and localized wormhole formation at fracture intersections. Fractures concentrate flow, establishing a positive feedback cycle - increased reactant delivery accelerates dissolution, increasing permeability and further concentrating flow. Multi-fold porosity increases near the inlet propagate along wormholes, creating localized mechanical weakness. Observed dissolution patterns demonstrate the necessity of pore-scale reactive flow-based upscaling approaches.
| Country | United Kingdom |
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