Geochemical Effects on Storage Gases and Reservoir Rock during Underground Hydrogen Storage: A Depleted North Sea Oil Reservoir Case Study

Motaz Saeed, Prashant Jadhawar* (Corresponding Author), Stefano Bagala

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)
7 Downloads (Pure)


In this work, geochemical modelling using PhreeqC was carried out to evaluate the effects of geochemical reactions on the performance of underground hydrogen storage (UHS). Equilibrium, exchange, and mineral reactions were considered in the model. Moreover, reaction kinetics were considered to evaluate the geochemical effect on underground hydrogen storage over an extended period of 30 years. The developed model was first validated against experimental data adopted from the published literature by comparing the modelling and literature values of H2 and CO2 solubility in water at varying conditions. Furthermore, the effects of pressure, temperature, salinity, and CO2 % on the H2 and CO2 inventory and rock properties in a typical sandstone reservoir were evaluated over 30 years. Results show that H 2 loss over 30 years is negligible (maximum 2%) through the studied range of conditions. The relative loss of CO2 is much more pronounced compared to H 2 gas, with losses of up to 72%. Therefore, the role of CO2 as a cushion gas will be affected by the CO2 gas losses as time passes. Hence, remedial CO2 gas injections should be considered to maintain the reservoir pressure throughout the injection and withdrawal processes. Moreover, the relative volume of CO2 increases with the increase in temperature and decrease in pressure. Furthermore, the reservoir rock properties, porosity, and permeability, are affected by the underground hydrogen storage process and, more specifically, by the presence of CO2 gas. CO2 dissolves carbonate minerals inside the reservoir rock, causing an increase in the rock's porosity and permeability. Consequently, the rock's gas storage capacity and flow properties are enhanced.
Original languageEnglish
Pages (from-to)323-337
Number of pages15
Issue number2
Publication statusPublished - 18 May 2023

Bibliographical note

This study was funded by the Net Zero Technology Centre, UK under the Hydrogen Innovation Grant scheme.

Data Availability Statement

Data used in this work can be shared privately upon request.


  • underground hydrogen storage
  • geochemical modelling
  • energy transition


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