InterPore2025

Anomalous Transport in Dissolving Porous Media: Transitions Between Fickian and Non-Fickian Regimes

19 May 2025, 15:05

1h 30m

Poster Presentation (MS08) Mixing, dispersion and reaction processes across scales in heterogeneous and fractured media Poster

Speaker

Jingxuan Deng

Description

Mineral dissolution is a key geologic process that can control many natural processes and human activities. Depending on the interplay between advection, diffusion, and reaction rates, mineral dissolution can produce various dissolution patterns, such as wormholing and uniform dissolution. The resulting changes in pore structure directly influence the flow field, which in turn control solute transport behavior. In this study, we conducted numerical modeling of mineral dissolution and solute transport in pore networks to investigate how initial network heterogeneity and dissolution regimes affect transport dynamics.

Dissolution of porous media is simulated using a 2D pore network model in which a porous media is represented as a series of interconnected cylindrical tubes with diameters getting enlarged in proportion to local reactant consumption. The heterogeneity is introduced in a network by assigning initial diameters to the tubes from log-normal distribution. The networks were subjected to varying dissolution regimes, from homogeneous to wormholing, resulting in changes in network heterogeneity. To investigate and analyze the impact of dissolution on the transport behavior, passive tracer transport simulations were performed using particle tracking.

Our findings show that dissolution significantly influences transport behavior by modifying the network's heterogeneity. In the wormholing regime, formation of highly conducting flow channels and stagnation zones increases network heterogeneity, resulting in the transition from Fickian to non-Fickian transport in networks with initially homogeneous structures. Conversely, in the uniform regime, reactant extensively homogenize the pore network and the flow field, leading to the transition from non-Fickian to Fickian transport, even in networks with high initial heterogeneity. We investigate the detailed mechanisms governing the transitions and show that the transitions could be predicted based on the initial network heterogeneity and Damköhler number.