(6e) Phase Behavior of H2+Gas+Brine Systems and H2 Dissolution Kinetics Under Subsurface Storage Conditions: Experiments and Thermodynamic Modeling

As part of the energy transition, the widespread deployment of hydrogen in the energy and transportation sectors requires the implementation of storage infrastructures adapted to the needs. Such infrastructures must guarantee a stable flow of hydrogen between production and consumption periods, and constitute a strategic reserve in case of potential disruptions in production or supply [1]. Although large-scale storage of pure hydrogen in salt caverns has been successfully practiced for decades for non-energy purposes, hydrogen storage in saline aquifers (used primarily for natural gas storage) has not yet been practiced [2]. Storage in deep aquifers offers the advantage of better geographic availability and flexibility and enormous storage capacity [1].

Laboratory tests and field feedback (historically through town-gas storage) have shown that hydrogen can participate in geochemical and microbiological reactions in the subsurface, particularly in aquifers [3]. In addition, hydrogen has different dissolution and mobility characteristics than natural gas. However, some preliminary studies have indicated a good potential of using saline aquifers for the storage of pure hydrogen or in mixture with natural gas [4]. Further research and experimentation are necessary to confirm these findings. Understanding the thermophysical properties of hydrogen is crucial in determining whether most of the injected hydrogen can be recovered, or whether a significant amount would be lost due to factors such as dissolution, diffusion, biogeochemical reactions, or leakage, which could limit the economic viability of storage. Moreover, the sizing of the surface facilities depends on the pressure/Temperature conditions of the gas and its quality after withdrawal. Thus, accurately quantifying the water content in the gas phase (which can occur du to humidification of the stored gas by water evaporation) is of great importance.

In this work, the phase behavior of H₂+gas+brine systems are studied experimentally and by modeling. The solubility of H₂ and co-solubility (CO₂, CH₄, H₂) in brine is measured by a volumetric/gravimetric method at high pressure and at different temperatures and salinities [5-6]. At these conditions, which are representative of the thermodynamic conditions of underground storage, the composition of the gas phase and in particular the water content is measured by gas chromatography and by coulometric Karl-Fischer titration. The effects of temperature, pressure and salting-out (due to the presence of salts) on the mutual solubilities are accurately correlated/predicted by different thermodynamic models (gamma-phi and phi-phi approaches [5]). Furthermore, the dissolution kinetics is also studied by measuring the diffusion coefficient of H₂ in water and brine by the pressure-decay method, and the data are processed by an adequate diffusivity model.

References

[1] Muhammed, Nasiru Salahu, et al. "A review on underground hydrogen storage: Insight into geological sites, influencing factors and future outlook." Energy Reports 8 (2022): 461-499.

[2] Underground Hydrogen Storage. GaffneyCline (2022)

[3] Heinemann, Niklas, et al. "Enabling large-scale hydrogen storage in porous media–the scientific challenges." Energy & Environmental Science 14.2 (2021): 853-864.

[4] Panfilov, Mikhail. "Underground and pipeline hydrogen storage." Compendium of hydrogen energy. Woodhead Publishing (2016). 91-115.

[5] Kerkache, Halla, et al. " Solubility of H2 in water and NaCl brine under subsurface storage conditions: measurements, molecular simulations and thermodynamic modeling." International Journal of Hydrogen Energy, (in press, 2023).

[6] Chabab, Salaheddine, et al. " A thermodynamic modelling to predict the bubble-point pressure from available information (T, GLR) from geothermal processes to prevent degassing". European Geothermal Congress (2022), Berlin.