Analysis of Underground Hydrogen Storage Efficacy in Porous Media Using a Coupled Hydrodynamical-Biochemical Modeling Approach

Summary Underground hydrogen storage (UHS) in porous media (such as depleted gas reservoirs and saline aquifers) offers a promising solution for large-scale, long-term energy storage, yet its safety and efficiency are strongly influenced by subsurface microbial activity. The current reactive transportation modeling approach employs the Arrhenius formulation or the Monod kinetic approach to model the microbial metabolism process. However, oversimplifications could be introduced because they assume microbial reactions occur instantaneously when certain conditions are met. To address this issue, we propose an improved Monod kinetic model incorporating an exponential lag recovery factor to describe microbial adaptation from dormancy to exponential growth and then a fully coupled multiphase, multicomponent simulation framework that integrates flow, transport, and microbial reaction kinetics to quantify hydrogen migration, consumption, and conversion processes. The framework further couples advection, dispersion, and chemotaxis to simulate microbial migration, spatial aggregation, and biofilm evolution within porous media. The validity of the model is confirmed by comparing against physical experimental data and results generated by a commercial simulator software package. Comparative case studies indicate that advection, dispersion, and chemotaxis affect microbial distribution and reaction intensity: Chemotaxis enhances local hydrogen-microbe coupling, increasing hydrogen consumption from 2% to 7–8% within a time period of 1,080 days, whereas the lag phase suppresses early metabolism, reducing losses to around 1%. Biofilm accumulation induces cumulative porosity reduction and potential permeability loss. The results demonstrate that microbial metabolism could be one of the working gas loss mechanisms and methane produced from the reaction could bring impurities to the produced gas.