Conference Agenda

A specialized workflow incorporating two innovative computing algorithms has been developed to understand and quantify natural hydrogen generation through the serpentinization of ultramafic rocks. This approach integrates geological, geophysical, structural, and petrophysical parameters. The area is divided into three critical zones: Surface, Shallow, and Deep. The Surface layer provides insights into hydrogen presence and migration paths. Detailed exploration of the reservoir and its seal is enabled by the Shallow layer, while the Deep layer focuses on the mechanisms behind hydrogen formation. Semi-circular structures indicative of natural hydrogen are detected by the NHSD (Natural Hydrogen Seeps Detection) algorithm, which applies deep learning to satellite imagery. In the Shallow layer, the reservoir seal is assessed using geological and geophysical modeling, which also examines the presence of fractures that act as migration paths. In the Deep layer, models employing gravity and magnetic data inversion, together with temperature distributions in a 3D model, target conditions favorable for serpentinization. The QNHG (Quantifying Natural Hydrogen Generation) algorithm calculates daily hydrogen production by scaling laboratory experiments to field conditions. This algorithm considers factors such as production rates, water/rock ratios, serpentinization front velocity, temperature, and fracture systems in peridotites—all adjusted to the characteristics of the study area. This refined system offers a comprehensive method for characterizing natural hydrogen environments, adaptable to various geological settings.

Hydrogen is regarded as an important part of our future emission free energy mix. Naturally occurring hydrogen could be a good candidate for the pursued energy mix as it does not need to be produced in an energy-intensive way. Many hydrogen seeps have been studied to characterise the concentrations and fluxes of the emanations and link these to the underlying rocks. Different multi-disciplinary methods are necessary to characterize the different aspects of a hydrogen generation system. However, further research into the hydrogen production potential of various rocks and settings is necessary. In our study, we applied numerical modelling to a 2D cross section in northern Bavaria (Münchberger Masse, Münchberg Massif) and integrated our current geological knowledge on the formation of the Münchberg Massif as well as literature data and own new measurements on rock samples. Based on the collected data we calculated several scenarios of hydrogen formation and transport during the geological evolution of the area and for the present day situation using the software TerrantaLab & TerrantaFlow. Possible hydrogen-generating rocks are the serpentinites and orthogneisses of the Münchberg Massif. Carboniferous granites of the Fichtelgebirge, which outcrop adjacent to the Münchberg Massif, could also generate hydrogen at greater depths. We present several scenarios of hydrogen formation to gain a better understanding of the decisive processes for natural hydrogen generation in the study area.

Hydrogen is expected to become a keystone of the energy transition to reach climate neutrality. In the future hydrogen economy, underground hydrogen storage (UHS) will become an integral part of the European hydrogen infrastructure.

The German hydrogen demand is expected to increase from 2030 on and a hydrogen storage demand of ca. 10% of the annual hydrogen demand is estimated. To meet this storage demand, existing storage capacity needs to be converted and new capacity installed. While current natural gas storage is mainly seasonal, hydrogen storage needs to be more dynamic to meet a growing hydrogen demand on the one hand and a fluctuating supply of green hydrogen on the other hand.

Next to operational challenges, underground hydrogen storage in salt caverns and porous reservoirs also faces several research challenges.Geochemical and microbiological processes in geological formations and their impact on hydrogen quality, storage integrity and reservoir performance are some of the main R&D demands for the safe implementation of UHS.

The BGR project "Generation, Migration and Degradation of Hydrogen – BiMiAb-H2" was developed to enable a quantitative investigation of the influence of geochemical and microbial processes on reservoir performance and caprock integrity.

This paper provides an overview of expectations and potentials for UHS in Germany and current research at BGR to address some of the remaining research questions.

To enable large-scale underground hydrogen storage, porous rock formations can complement the storage space of salt caverns, which currently are investigated in first pilot tests in Germany. In porous rocks, mainly sandstone formations, several reactions and processes might impart on the storage of H₂.

Here we present first data for five formations with an in depth petrographical and mineralogical characterization as well as experimental investigations with high partial pressures of H₂ under near in situ pressure-temperature-conditions. The formations investigated include Tertiary sandstones (Bunte Niederrödern Schichten, Chatt), Tertiary limestone (Lithothamnienkalk), the Triassic Solling Sandstone and the Permian Wustrow and Schneverdingen Sandstone. For each formation, small diameter core plugs and thin sections were prepared from core samples for petrophysical and petrographic characterisation. One part of each core section has been crushed and milled, the pulverized rock material analysed for mineralogical and geochemical composition. In addition, the rock material was investigated in high-pressure experiments and the consumption of hydrogen quantified over a duration of 2 to 4 weeks. Overall, the hydrogen oxidation by H₂-fluid-mineral surface reactions is limited; several mineralogical factors responsible for the oxidation are evident. Additional experiments investigating the kinetics of individual reactions, e.g. of iron oxides present in the rock material, complement the first assessment of geochemical reactions in these possible storage formations.

Underground hydrogen storage (UHS) in geological reservoirs is proposed as a technically feasible solution to balance mismatch between supply and demand in emerging markets. However, unique hydrogen properties and coupled flow mechanisms require new investigations to fully understand transport and storage of hydrogen in porous media across scales. Here we use microfluidics to investigate the effect of gas type and injection rate on flow patterns, saturation and connectivity of the gas phase. We visually observe that gas flow is characterized by capillary fingering, further confirmed by fractal dimension analysis. At lower injection rates, the gas saturation after drainage appears to increase with gas viscosity, with lower hydrogen saturation compared to methane and nitrogen. The maximum gas saturations (39–46 %) were achieved at higher injection rates, showing no clear correlation to gas type. However, the high-rate injections lead to undesired outcomes in terms of formation of disconnected gas ganglia, mostly pronounced for nitrogen. We identify an optimal injection rate to achieve maximum gas saturation with the least amount of disconnected gas.