Numerical modeling of multiphase biogeochemical processes during hydrogen leakage in shallow aquifers

Abstract

This study develops a numerical framework to investigate the impacts of hydrogen leakage from subsurface storage on shallow aquifers. The model describes multiphase flow and biogeochemical processes, including microbial hydrogen consumption, with CO 2 speciation treated at thermodynamic equilibrium and microbial reactions governed by kinetic rate laws. The system is formulated as a coupled set of partial differential equations combined with ordinary differential equations. A fully implicit finite volume scheme is implemented in DuMu X . Microbial activity is modeled using the thermodynamic formulation of Jin and Bethke, compared with a classical Double Monod model. Numerical investigations assess their effects on hydrogen consumption, biochemical consistency, and leakage-driven hydrogen migration. The results highlight the role of microbial processes in hydrogen attenuation: over a two-year period, about 3.5% of injected hydrogen is consumed, with metabolic pathways exhibiting spatial and temporal variability. These results provide valuable insights for underground hydrogen storage risk assessment and monitoring.