Date of Award
2025
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Doctor of Philosophy
School
School of Engineering
First Supervisor
Stefan Iglauer
Second Supervisor
Alireza Keshavarz
Third Supervisor
Eirini Goudeli
Abstract
This thesis presents a comprehensive compilation of experimental and simulation data gathered across diverse geological conditions. The aim is to offer valuable insights into subsurface storage of hydrogen (H2), carbon dioxide (CO2) and other greenhouse gases like methane (CH4) The storage process involves a complex mix of components, including rock fabric, gas, and ubiquitous water. The collected data for these components specifically explores H2 and wettability and adsorption across various earth minerals. Additionally, the thesis provides essential data on CH4 adsorption in shale samples and water adsorption in shale samples. Furthermore, it evaluates CO2 wettability and interfacial properties within basaltic rocks.
This study explores the H2-wettability of illite surfaces via molecular dynamics simulations. An illite layer was created through a supercell approach, augmented by a vacuum layer to ensure accuracy, while water was modeled using the SPC/E model, and H2 molecules were introduced into the vacuum space to attain the required The wettability of illite surfaces is quantified by contact angle calculations directly from simulation trajectories at various pressure and temperature (conditions. 300 and 343 K and5 MPa, 10 MPa, 20 MPa, and– 30 MPa). Contact angles were determined using the MATLAB code to understand wettability changes under varying pressures. The results indicated that illite is strongly hydrophilic, contact angle calculations indicate to illite surface, ranging from 36° to 51° at 300 K and 31° to 41° at 343 K. The contact angles increase with pressure due to stronger intermolecular interactions between H2 and illite, but decrease with temperature due to weaker intermolecular interactions. H2-caprck sealing efficiencies were also predicted, they ranged from 243 to 201 m at 300 K and 230 to 205 m at 343 K, due to illite’s contact angle wettability transition. The employed methodology for water contact angle and sealing capacity calculations offers a practical alternative to experimental measurements.
Physisorption can contribute to hydrogen subsurface storage. However, hydrogen physisorption at the surface of geological samples is mostly unknown. We are unaware of previous studies that investigate H2 Physisorption in wide range of pure inorganic and organic earth minerals. Knowledge about H2 Physisorption is required to evaluate the suitability of underground H2 storage. We thus evaluated H2 physisorption on common earth minerals, including illite, kaolinite, quartz, calcite, and kerogen via lab experiments and Grand Canonical Monte Carlo (GCMC) simulations at temperature ranging between 273 to 373 K and pressure ranging between 5 MPa to 40 MPa. The simulation results, including densities and H2 adsorption uptakes, are in agreement with experimental results. The quantity of adsorbed hydrogen ranked as: illite > kerogen > kaolinite > quartz > calcite; and Gibbs energy change, enthalpy change, and isosteric heat energy indicated that H2 adsorption spontaneity increases as illite > kerogen > kaolinite > calcite > quartz. We conclude that H2 adsorption is high on the high-surface-area materials (clays or kerogen), and that H2 adsorption on earth minerals could improve the effectiveness of subsurface H2 storage.
Water sorption isotherms were measured at relative humidity ranging from 10% to 99% and temperature of 90°C. Shale fractal properties were then evaluated and capillary pressure (ranging from 1.70 to 386 MPa ) were obtained using Kelvin relationship. The results show that Mancos shale, from the US, adsorbed more absorbed water due to its high clay concentration and low TOC. However, Wolfcamp shale, from the US, has the lowest TOC and clay concentration, adsorbing the lowest amount of water. There is little hysteresis between adsorption and desorption isotherms explaining water retention phenomenon in some shales. The obtained fractal dimension values ranged between 2.45 and 2.76 and average of 2.56 indicating irregular pore surface and complex pore structure. All shale sample's capillary curves were fitted to Brooks & Corey and van Genuchten models with nonlinear regression. The fitting coefficient, R2, which represents the proportion of variance, for Brooks & Corey fits ranged from 0.90 to 0.97 for imbibition and 0.85 to 0.98 for drainage, while R2 for the van Genuchten model ranged from 0.94 to 0.99 for both imbibition and drainage. Thus, the proposed method can be used to measure capillary pressure-saturation relationships in gas shales.
Understanding surface properties such as wettability and CH4/shale interfacial tension (IFT) is essential to decipher CH4 productivity and hydrocarbon-in-place estimates. However, these factors are poorly understood due to lack of data despite their importance. We thus measured the equilibrium contact angle (θe), reflecting the degree of wetting for shale/CH4/water systems, and determined the governing interfacial tensions. In particular, water/CH4, water/shale, and CH4/shale IFTs are determined at pressures 0.1, 5,10,15, and 20 MPa and temperatures 303.15, 323.15, 343.15, and 373.15 K. Shale samples from Eagle Ford and Mancos were used to examine the effect of treating the shale samples with Cetyltrimethylammonium ammonium bromide (CTAB, a cationic surfactant) on contact angle and IFTs. Finally, excess CH4 adsorption on the shale surfaces was determined before and after adding CTAB surfactant. The results showed that shale/CH4/water equilibrium contact angles (θe) increased with pressure but decreased with temperature. The Eagle ford sample exhibited a contact angle of 138°. In comparison, the Mancos shale sample exhibited 97°, both at 20 MPa and 373.15 K. These contact angles suggest that Eagle Ford shale is more CH4-wet than Mancos shale due to the higher TOC of Eagle Ford shale (4.95 wt.%, while Mancos shale had a TOC = 1.02 wt.%). Water/CH4 IFT decreased from 71.47 mN/m to 56.02 mN/m as pressure and temperature increased from 0.1 MPa, 303.15 K to 20 MPa, 373.15 K. Shale/CH4 IFT also decreased with increasing pressure and temperature. Finally, CTAB surfactant treatment increased contact angles but reduced water/CH4, water/shale, and CH4/shale IFT. CTAB also reduced the amount of adsorbed CH4 and increased the amount of free CH4, which implies improved CH4 recovery from shale reservoirs.
In this study, we have experimentally investigated basalt/CO2 interfacial tension under various pressures ranged from 4 MPa to 17 MPa and at temperatures of 308° K and 333° K. Our findings suggest that, as expected, Basalt/CO2 interfacial tension decreases as the pressure increases. At a given temperature, the maximum height of CO2 that can be trapped by Basalt rocks decreases with IFT of CO2/Basalt systems. Furthermore, the results also indicate that the maximum height (h max) of trapped CO2 increases with temperature (at 308 K, h max reached about 35 m, while at 333 K h max reached 40 m). We also found that there is remarkable relationship between Basalt/CO2 IFT and CO2 density (ρ) at 308 K and 333 K. The introduced relationship could serve as a handy tool to give a quick prediction of IFT CO2/Basalt in basaltic formation or other CO2/Solid systems.
This thesis advances subsurface gas storage by addressing key factors affecting geological interfaces’ interaction with several components including H2, CH4, water and CO2. Notably, it is one of the earliest research projects to contribute to the body of literature by developing a methodology to assess H2 wettability through molecular simulation. It examines the wettability of illite surfaces for H2 storage, physisorption of hydrogen on various minerals, water sorption in shales, interfacial tensions impacting CH4 recovery, and CO₂ storage in basaltic rocks. By analyzing these factors through simulations and experiments, the research provides insights into improving storage efficiency, safety, and effectiveness in geological formations, thereby supporting the transition to cleaner energy sources and climate change mitigation.
DOI
10.25958/fg5e-xb32
Access Note
Access to this thesis is embargoed until 22nd March 2030
Recommended Citation
Abdulelah, H. (2025). Interactions with geological interfaces: Hydrogen, carbon dioxide, methane and water for sub-surface storage. Edith Cowan University. https://doi.org/10.25958/fg5e-xb32
