Microfluidic insights into microbial impacts on hydrogen flow in underground hydrogen storage

Underground hydrogen storage, involving periodic injection and extraction of hydrogen gas, serves as a crucial approach for achieving energy peak shaving and accommodating large-scale renewable energy. However, microorganisms residing underground may undergo metabolic reactions when stimulated by hydrogen, producing gases and altering rock surface properties. This could potentially influence hydrogen migration and storage behavior, yet the underlying mechanisms remain poorly understood. To address this, this study introduces microbial reactions within a microfluidic chip and combines hydrogen displacement experiments under varying pressure differentials to reveal two distinct phenomena by which microbial activity influences hydrogen flow pathways. It was observed that when microbially produced gas communicates with hydrogen, it triggers a readjustment of flow pathways and accelerates the advancement of the hydrogen front. In addition, when microbially produced gas forms stable gas mass downstream in the pore network, it induces shifts in dominant flow pathways. Contact angle measurements further confirm that microbial metabolism significantly reduces pore surface wettability, though this wettability change exhibits pronounced spatial heterogeneity. Displacement results under varying pressure differentials reveal that at low pressures, reduced capillary resistance facilitates sweep range and higher hydrogen saturation. Conversely, at high pressures, viscous flow dominates; weakened wettability accelerates breakthrough while inhibiting lateral branch development, ultimately reducing overall saturation. This study provides novel experimental evidence for understanding microbe-flow interactions during underground hydrogen storage.