Monitoring Underground Hydrogen Storage: An Integrated Multi-Domain Framework

Underground hydrogen storage (UHS) is poised to emerge as a pivotal technology for large-scale and seasonal energy storage in future low-carbon energy systems. Nevertheless, ensuring its safe deployment necessitates implementation of monitoring strategies that account for the distinct physicochemical and microbiological characteristics of hydrogen. These characteristics cannot be directly transposed from underground gas storage (UGS) or carbon capture and storage (CCS) applications. In this study, we propose an integrated multi-domain monitoring framework for UHS developed through a thorough evaluation of European regulations; ISO and DNV standards; monitoring practices; and representative CCS, UGS, and UHS case studies. The framework includes a conceptual digital twin architecture for integrating heterogeneous monitoring data and supporting model updating, anomaly screening, and operational interpretation. It comprises five complementary monitoring domains: subsurface, near-surface, surface, remote, and digital. The integration of geophysical, geochemical, microbiological, atmospheric, and digital monitoring techniques, including 4D seismic surveys, fiber-optic sensing, hydrogen leakage detection systems, and satellite- and UAV-based observations, is a key aspect of this study. The analysis demonstrates that monitoring approaches developed for CCS and UGS provide a solid foundation for UHS but require adaptation to account for hydrogen’s high diffusivity, low viscosity, limited geochemical footprint, flammability, material compatibility issues, and potential for microbial conversion. The digital domain is proposed as an integration layer for monitoring data, model updating, anomaly screening, and decision support. Predictive and real-time capabilities require future field-scale implementation and validation. The proposed framework may provide a structured conceptual basis for the development of future UHS monitoring guidance, pilot applications, and regulatory requirements.