Abstract

Geologic hydrogen, including both naturally occurring and stimulated, is a promising primary energy resource. The Earth is a natural laboratory where hydrogen can be observed from surface features (e.g., springs, fairy circles) and subsurface structures (e.g. geothermal wells, chromite mines). The Earth is also a natural factory where both natural and stimulated hydrogen can be generated through water–rock reactions such as serpentinization -- a highly complex set of coupled chemo-mechanical processes (Hu, 2025a). The development of geologic hydrogen can be accelerated significantly by leveraging decades of technologies developed in industries such as geothermal (Hu et al., 2026), with a key distinction of H₂ generation.

In this talk, Hu will present several major factors that control the economics of stimulated geologic hydrogen: the efficiency of H₂ extraction and injection strategies, stress-mediated reaction rates, fracture density, and water consumption and regional water availability. First, a novel cyclic injection approach that enhances H₂ extraction will be introduced. This technology exploits the interplay between two-phase flow and fracture geometry and has been tested using both numerical modeling and laboratory experiments.

To investigate the chemo-mechanical controls on H₂ generation, a previously developed modeling framework, NMM–Crunch (Hu et al., 2021), has been extended to account for stress-mediated mineral dissolution and growth within a new unified chemo-mechanical rate law. The model has been applied to simulate H₂ generation in partially serpentinized rocks and it demonstrates that stress suppresses serpentinization reactions, thereby reducing H₂ generation rates.

Finally, using H₂ generation rates obtained from experiments (Hu, 2025b) at different temperatures with varying fracture densities and across multiple length scales, Hu conducted a techno-economic analysis of stimulated geologic hydrogen for two potential sites in CA with different water supply scenarios. The results show that reaction rates, controlled primarily by fracture density, as well as regional water availability and supply, are both critical factors governing the cost of stimulated geologic hydrogen. These findings highlight key interdisciplinary research areas needed for the future success of geologic hydrogen.

Bio

Dr. Mengsu Hu is a Staff Scientist at the Lawrence Berkeley National Laboratory. Her research focuses on multiscale numerical modeling and machine learning for analyzing coupled thermal-hydro-mechanical-chemical (THMC) processes from fundamental Earth science to subsurface engineering systems. Since 2024, Dr. Hu has led multiple projects on geologic hydrogen, studying cyclic injection for economic and seismic safe geologic hydrogen generation and production (funded by ARPA-E), anisotropic stress control on serpentinization (funded by BES), and pathways from enhanced geothermal systems to stimulated geologic hydrogen (newly funded by GTO). Dr. Hu is serving on the Board of Directors of American Rock Mechanics Association (ARMA). Since 2022, she has been invited to serve on the Editorial Board for Rock Mechanics and Rock Engineering (Associate Editor), PNAS Nexus of the National Academy of Sciences (NAS), Journal of Rock Mechanics and Geotechnical Engineering, International Journal of Rock Mechanics and Mining Sciences, and Geomechanics and Geophysics for Geo-Energy and Geo-Resources. In 2022, Dr. Hu was selected as a participant of National Academy of Engineering (NAE) U.S. Frontiers of Engineering (FOE) symposium.

Research/Related Papers

Hu, M. (2025a). Geologic hydrogen production: Geomechanics, reactive fluid transport, and induced seismicity. In Frontiers in Geologic Hydrogen, National Academies Meeting. Link

Hu, M., Schill, E., Rutqvist, J., Steefel, C., & Weber, A. (2026). From enhanced geothermal systems (EGS) to stimulated geologic hydrogen. DOE GTO Report, Lawrence Berkeley National Laboratory, Berkeley, CA.

Hu, M., Steefel, C. I., & Rutqvist, J. (2021). Microscale mechanical–chemical modeling of granular salt: Insights for creep. Journal of Geophysical Research: Solid Earth, 126(12), e2021JB023112.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021JB023112

Hu, M. (2025b). Toward economic and seismic-safe geologic hydrogen. October 10, 2025, Warren Distinguished Lecture Series, University of Minnesota, Minneapolis, MN, United States.
https://cse.umn.edu/cege/events/toward-economic-and-seismic-safe-geologic-hydrogen