Fracture networks as reactors
Résumé
Flow and transport in fractures play a central role in a broad range of geochemical and biological reactions involved in water quality, deep microbial life, CO2 sequestration, waste storage, and energy extraction/storage in the subsurface. Fractures are present at all scales and constitute complex flowing networks where dissolved chemical species are transported, interact with the rock matrix, mix and react. These reactive transport dynamics involve key elements that fundamentally differ from conventional well-mixed reactors, including broad residence time distributions (e.g. Kang et al. 2015), fracture-matrix exchanges and fluid-rock reactions (e.g. Hoffmann et al. 2020, Osorio-Leon et al. in press), localized mixing and reaction hot spots (e.g. Bochet et al. 2020), and dynamic network evolution through dissolution/precipitation, bioclogging and reaction-induced fracturing (e.g. Renard 2021). In this presentation, we will discuss recent field observations and new conceptual models that contribute to establish the effective properties and dynamics of fracture networks as biogeochemical reactors.