Geologic Hydrogen -- From Chemo-Mechanics to Economics

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 H? 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 H? 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 H? 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 H? generation in partially serpentinized rocks and it demonstrates that stress suppresses serpentinization reactions, thereby reducing H? generation rates.

Finally, using H? 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.

Speaker: Mengu Hu, Lawrence Berkeley National Laboratory