Microscopic flow and reactive transport in the subsurface are fundamental to understanding the coupled physical, chemical, and biological processes governing subsurface environments. These processes play a critical role in sustainable water resource management, groundwater contamination control and remediation, geological carbon storage, and subsurface energy exploitation. With the escalating impacts of global climate change and anthropogenic activities, interactions among physical and chemical processes in geological media have grown increasingly complex. Consequently, research on flow and reactive transport has emerged as a vibrant and rapidly evolving frontier. A dedicated session entitled “Microscopic Flow and Reactive Transport in Geological Media” was featured at the “2025 International Symposium on Subsurface Reactive Transport” successfully held in Changchun, China, September 19-21, 2025. The symposium served as a platform for interdisciplinary collaboration and knowledge exchange, providing new perspectives and establishing a solid foundation for future scientific cooperation in the field of subsurface reactive transport.

In order to examine the heterogeneous nucleation and growth dynamics of mineral precipitation in reactive transport systems, as well as the evolution of key upscaling parameters, such as porosity and permeability, this study employs a model that integrates pore-scale reactive transport with arbitrary Lagrangian-Eulerian method. This model incorporates a heterogeneous probabilistic nucleation process based on classical nucleation theory, which is used to parametrically simulate the nucleation and growth processes of individual mineral particles within the reactive transport. The findings indicate that fluid velocity, along with nucleation and mineral growth rates, plays critical roles in determining the pattern and spatial distribution of precipitates. Nucleation promotes irregularities in the precipitate pattern and reduces the influence of flow on the spatial distribution of precipitate formation across particle surfaces. Precipitation on the surface of a single mineral particle within a pore channel is more accurately governed by a power law model, which captures the evolutionary relationship between porosity and permeability in porous media with periodic structures.

The exploitation of natural gas hydrates is in essence the process of hydrate dissociation from the solid phase into the gas and liquid phases, which is a complex problem involving phase transition and gas-water multi-phase flow. Permeability is a useful parameter for characterizing the flow capacity of sediments, and the pore-structure changes caused by hydrate dissociation make this parameter characterized by spatial and temporal evolution. Clayey silt sediments form the hydrate accumulation reservoir in the South China Sea, whose lithological characteristics (shallow buried deep, poor permeability, and low cementation) are unfavorable to fluid flow, leading to difficulties in the production prediction of clayey silt hydrate-bearing sediments. In this paper, the mutual feed-back mechanism between pore-structure and permeability during hydrate dissociation was clarified using the lattice Boltzmann model method. Core-scale seepage experiments were carried out to validate the dynamic evolution of permeability relationship. The permeability calculation module of Tough+Hydrate code was developed to quantitatively describe the evolution of this relationship, and the first hydrate production test in the Shenhu area was evaluated to validate the applicability of pore- and core-scale study at the site scale. This study clarifies the dynamic evolution mechanism of permeability during hydrate dissociation, and establishes a permeability evolution model in a S-shape suitable for clayey silt hydrate-bearing sediments.