Pore characteristics heavily influence the gas storage mechanisms in gas shales. For a deep understanding of the pore structure characteristics, the fractal analysis was performed through low-pressure nitrogen (N 2 ) adsorption experiments on 5 shale samples collected from Gondwana and Assam basins of India. The characteristics of low-pressure N 2 adsorption isotherms revealed the mesoporous nature of the shale samples. It can be observed that N 2 adsorption was dominated by van der Waals forces until the relative pressure (P/P o ) reached ≈0.45, and later, it was dominated by surface tension thereby dividing the adsorption curve into 2 regions at P/P o ≈ 0.45. Fractal dimensions (D) were estimated using the Frenkel−Hasley−Hill (FHH) method in the abovementioned 2 regions separately. The fractal dimensions were further correlated with the shale constituents and different pore characteristic parameters. Results indicate that fractal dimensions are positively correlated with the BET specific surface area (BET-SSA) and quartz content. However, fractal dimensions negatively correlated with the TOC, CO 2 micropore volume, and average pore diameter. Comparison of the fractal dimensions with the shale pore characteristics suggested that the selected shale samples are highly nonhomogeneous and are dominant with complex micropores and mesopores.
Hydrogen can act as a potential alternative to fossil fuels; however, storage of this energy source is a challenge to overcome. Researchers have been concentrating on geological hydrogen storage in sandstones and shales. Gas in the latter porous rock is primarily stored in the adsorbed phase, to which inorganic minerals, like montmorillonite, illite, and kaolinite, contribute significantly. In this work, the adsorption of gaseous hydrogen on different clay and clay minerals has been studied experimentally at low-pressure−low-temperature (LPLT, 77 K) and high-pressure− high-temperature (HPHT, 313 K) conditions. Further, the pore characteristics of the selected clay samples have been analyzed using low-pressure N 2 (77 K) and CO 2 (273 K) adsorption. Scanning electron microscopy (SEM) images of the samples have been utilized to study their morphology, particle sizes, and pore structures. The role of pore structure parameters on hydrogen adsorption at LPLT and HPHT has been investigated. Through these investigations, it has been found that the specific surface area and micropore volume positively affect hydrogen adsorption and the average pore width affects it negatively. Further, the applicability of some well-known adsorption models, like Langmuir, Freundlich, Toth, and Sips, has been investigated. It has been found that the Langmuir model gives a poor fit in both experimental conditions. The Toth and Sips models are good at LPLT as well as HPHT conditions.
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