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Impact of CO2 impurity in hydrogen gas on wetting characteristics of carbonate minerals; new insights and implications for hydrogen geo-storage in saline aquifers
Citation Link: https://doi.org/10.15480/882.15355
Publikationstyp
Journal Article
Date Issued
2025-09-01
Sprache
English
Author(s)
Dalal Isfehani, Zoha
TORE-DOI
Journal
Volume
129
Article Number
117274
Citation
Journal of Energy Storage 129: 117274 (2025)
Publisher DOI
Scopus ID
Publisher
Elsevier
The effectiveness of Underground Hydrogen Storage (UHS) as a long-term solution for sustainable green energy
relies on secure containment in geological formations and optimized storage and retrieval processes, where fluidrock
interactions, particularly the wettability of the rock, play a crucial role. Additionally, the pre-injection of a
cushion gas, such as CO2, to maintain sufficient pressure for hydrogen (H2) withdrawal can influence wettability.
This study employed the tilted plate method to examine contact angle hysteresis of the wetting phase (water) on
a carbonate rock substrate, measuring advancing and receding contact angles in the presence of various H2-CO2
mixtures ([0.30 CO2 + 0.70 H2], [0.50 CO2 + 0.50 H2, 0.70 CO2 + 0.30 H2]) at pressures (500, 1200, 2000, and
3000 psi) and temperatures (50 ◦C and 80 ◦C). Further analyses using AFM (Atomic Force Microscopy) and EDS
(Energy Dispersive X-ray Spectroscopy) were conducted to assess the effects of CO2 impurity on the carbonate
rock surface. Our findings indicate that while pressure has minimal effect on the wetting properties of the
carbonate substrate, higher temperatures make the surface more water-wet. More importantly, CO2 concentration
plays a critical role in system wettability, as increasing the CO2 mole fraction from 30 % to 70 % significantly
reduces the water-wetness of the carbonate surface. Specifically, the rock remains water-wet under
reservoir conditions when CO2 is 50 % or less, with contact angles between 42◦ and 65◦, whereas at higher CO2
levels, it shifts toward neutral wettability, with contact angles ranging from 80◦ to 100◦. AFM and EDS analyses
indicate that changes in surface roughness and elemental concentration due to CO2 exposure contribute to these
wettability variations. As a result, at lower CO2 concentrations because of more water-wet state of the surface
and higher IFT, a higher gas column height and storage capacity is acheivable, whilst stronger snap-off effect and
hence more trapped gas during water imbibition process, impairs the hydrogen recovery efficiency. The opposite
applies at higher CO2 levels. Thus, optimizing CO2 concentration is a key factor in balancing the storage capacity
and the recovery efficiency. The findings of this work enhance our understanding of hydrogen geo-storage
mechanisms in carbonate reservoirs with CO2 as a cushion gas, supporting more reliable predictions for underground
hydrogen storage projects.
relies on secure containment in geological formations and optimized storage and retrieval processes, where fluidrock
interactions, particularly the wettability of the rock, play a crucial role. Additionally, the pre-injection of a
cushion gas, such as CO2, to maintain sufficient pressure for hydrogen (H2) withdrawal can influence wettability.
This study employed the tilted plate method to examine contact angle hysteresis of the wetting phase (water) on
a carbonate rock substrate, measuring advancing and receding contact angles in the presence of various H2-CO2
mixtures ([0.30 CO2 + 0.70 H2], [0.50 CO2 + 0.50 H2, 0.70 CO2 + 0.30 H2]) at pressures (500, 1200, 2000, and
3000 psi) and temperatures (50 ◦C and 80 ◦C). Further analyses using AFM (Atomic Force Microscopy) and EDS
(Energy Dispersive X-ray Spectroscopy) were conducted to assess the effects of CO2 impurity on the carbonate
rock surface. Our findings indicate that while pressure has minimal effect on the wetting properties of the
carbonate substrate, higher temperatures make the surface more water-wet. More importantly, CO2 concentration
plays a critical role in system wettability, as increasing the CO2 mole fraction from 30 % to 70 % significantly
reduces the water-wetness of the carbonate surface. Specifically, the rock remains water-wet under
reservoir conditions when CO2 is 50 % or less, with contact angles between 42◦ and 65◦, whereas at higher CO2
levels, it shifts toward neutral wettability, with contact angles ranging from 80◦ to 100◦. AFM and EDS analyses
indicate that changes in surface roughness and elemental concentration due to CO2 exposure contribute to these
wettability variations. As a result, at lower CO2 concentrations because of more water-wet state of the surface
and higher IFT, a higher gas column height and storage capacity is acheivable, whilst stronger snap-off effect and
hence more trapped gas during water imbibition process, impairs the hydrogen recovery efficiency. The opposite
applies at higher CO2 levels. Thus, optimizing CO2 concentration is a key factor in balancing the storage capacity
and the recovery efficiency. The findings of this work enhance our understanding of hydrogen geo-storage
mechanisms in carbonate reservoirs with CO2 as a cushion gas, supporting more reliable predictions for underground
hydrogen storage projects.
Subjects
Carbon dioxide | Carbonate mineral | Contact angle | Cushion gas | Hydrogen geo-storage | Wettability
DDC Class
620.11: Engineering Materials
530.43: Gas Physics
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