Diffusive transport of gases in saturated nanopores: Caprock leakage from a molecular simulation perspective

Benazzouz, B.K.; Ho, Khac Hieu; The, Nguyen Phuoc; Hoang, Hai; Galliéro, Guillaume

doi:10.1016/j.jngse.2021.104383

Cited by 3 publications

(8 citation statements)

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“…This concentration is higher than the typical gas solubility measured in bulk water under ambient conditions. 77 However, the recent study of Benazzouz et al 17 indicates that the solubility of methane and ethane increases under confinement and become comparable with the concentration used in this study. The molar ratio of 1% has been widely used in previous MD simulations and provides a good agreement with the experimental data.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The increasing demand for energy over the years has led to the demand of gas storage in geological reservoirs. For example, the geological storage of CO 2 gas has been considered a sustainable option for sequestration of anthropogenic CO 2 emissions. − Over the years, H 2 storage in underground aquifers has been considered a viable solution for renewable energy storage. − These trapped gases have the potential to migrate into and through the water-saturated pore space of the sealing geological medium (caprock), a phenomenon called caprock leakage. − Therefore, understanding gas transport through such systems is crucial for quantifying the efficiency of the geological sealing medium.…”

Section: Introductionmentioning

confidence: 99%

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Mobility of Dissolved Gases in Smectites under Saturated Conditions: Effects of Pore Size, Gas Types, Temperature, and Surface Interaction

et al. 2022

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In a nuclear waste repository, the corrosion of metals and the degradation of the organic material in the waste matrix can generate significant amounts of gases. These gases should be able to migrate through the multibarrier system to prevent a potential pressure build-up that could lead to a loss of barrier integrity. Smectite mineral particles form a tortuous pore network consisting of larger interparticle pores and narrow interlayer pores between the platelets of the smectite minerals. These pores are normally saturated with water, so one of the most important mechanisms for the transport of gases is diffusion. The diffusion of gases through the interparticle porosity depends on the distribution of gas molecules in the water-rich phase, their self-diffusion coefficients, and the tortuosity of the pore space. Classical molecular dynamics simulations were applied to study the mobility of gases (CO2, H2, CH4, He, and Ar) in Na-montmorillonite (Na-MMT) under saturated conditions. The simulations were used to estimate the gas diffusion coefficient (D) in saturated Na-MMT as a function of nanopore size and temperature. The temperature dependence of the diffusion coefficient was expressed by the Arrhenius equation for the activation energy (E a). The predicted D values of gases were found to be sensitive to the pore size as the D values gradually increase with increasing pore size and asymptotically converge to the gas diffusion coefficient in bulk water. This behavior is also observed in the self-diffusion coefficients of water in Na-MMT. In general, H2 and He exhibit higher D values than Ar, CO2, and CH4. The predicted E a values indicate that the confinement affects the activation energy. This effect is due to the structuring of the water molecules near the clay surface, which is more pronounced in the first two layers of water near the surface and decreases thereafter. Atomic density profiles and radial distribution functions obtained from the simulations show that the interaction of the gas with the liquid and the clay surface influences mobility. The obtained diffusion coefficient for different gases and slit pore size were parameterized with a single empirical relationship, which can be applied to macroscopic simulations of gas transport.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mobility of Dissolved Gases in Smectites under Saturated Conditions: Effects of Pore Size, Gas Types, Temperature, and Surface Interaction

et al. 2022

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“…The hydrogen leakage through the caprock mainly includes two aspects, which are H 2 breakthrough when the storage pressure exceeds the nanopore capillary pressure and gas dissolution into the caprock. A few recent studies have evaluated the H 2 breakthrough pressure by studying the H 2 wettability, and the results showed that the breakthrough pressure for hydrogen storage is not a concern. , However, the gas dissolution through the caprock can be noticeably enhanced as a result of the nanoconfinement effect of the caprock nanopores, inducing a remarkable H 2 loss during UHS. , However, the H 2 loss by dissolution in the caprock clay pores is still unclear. Moreover, the injected H 2 is mixed with the cushion gas of CH 4 in the reservoir formation during UHS, but the impact of CH 4 on the H 2 dissolution in the saturated caprock nanopores remains unknown and needs further study before the implementation of UHS.…”

Section: Introductionmentioning

confidence: 99%

“…Both mechanisms have been observed for CH 4 and CO 2 , but the mechanism is still unclear for H 2 dissolution in the nanopores. Benazzous et al found that the local density of CH 4 close to the surface of caprock pores is about 15 times the bulk solubility as a result of adsorption, while the density in the pore middle is similar to the bulk solubility . The properties of the pore surface also change the gas dissolution mechanism.…”

Section: Introductionmentioning

confidence: 99%

“…A few recent studies have evaluated the H 2 breakthrough pressure by studying the H 2 wettability, and the results showed that the breakthrough pressure for hydrogen storage is not a concern. 5,6 However, the gas dissolution through the caprock can be noticeably enhanced as a result of the nanoconfinement effect of the caprock nanopores, 7 inducing a remarkable H 2 loss during UHS. 8,9 However, the H 2 loss by dissolution in the caprock clay pores is still unclear.…”

Section: Introductionmentioning

confidence: 99%

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Molecular Simulation of H₂ Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage

Zhang,

Luo,

Yang

et al. 2023

Energy Fuels

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Hydrogen has been regarded as an important clean energy source in recent years. The depleted reservoir has been recognized as an economic geological site for hydrogen storage as a result of its large storage capacity. However, the caprock sealing safety of the reservoir must be considered before underground hydrogen storage. To investigate the hydrogen loss in the caprock, we have studied the H 2 dissolution in the caprock water-saturated kaolinite nanopores using molecular simulations in this work. The H 2 /CH 4 mixture dissolution in the caprock nanopores was also studied to investigate the effect of the CH 4 cushion gas on the H 2 dissolution. The results showed that the H 2 dissolution can increase by up to 27 times the bulk solubility under the impact of nanoconfinement enhancement, and the gas loss through the caprock is mainly by the smaller water-saturated pores. The maximum solubility of H 2 and CH 4 occurs at the 0.55 and 0.6 nm pores, respectively. For the 0.5−0.55 nm pores, the dissolved H 2 density exceeds CH 4 at the H 2 fraction above 50%. As the pore size increases to 2.0 nm, the H 2 and CH 4 solubility is comparable as the nanopore confinement effect gradually becomes weak. However, as the H 2 fraction increases to 80%, the H 2 dissolution dominates over CH 4 , even in the 2.0 nm pore. With the increase of the pore size, the water molecules gradually occupy the strong adsorption sites near the surfaces; thus, the gas molecules start to accumulate in the pore middle. The cushion gas of CH 4 adopts various molecular angles in the pores, which are 50°and 130°in the 0.55 nm pore and tripod and inclined angles of 70°and 110°in the 1.0 nm pore. However, the dissolved H 2 molecules are always perpendicular toward the pore surface, which is not affected by the pore size and water molecules. Under the influence of brine, the solubility of H 2 and CH 4 decreases and the impact of brine is more noticeable in larger pores. The high brine salinity helps to reduce the H 2 loss in the caprock nanopores.

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Modeling Solubility Induced Elemental Fractionation of Noble Gases in Oils

Hoang,

Ho,

Battani

et al. 2025

Geochimica et Cosmochimica Acta

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Diffusive transport of gases in saturated nanopores: Caprock leakage from a molecular simulation perspective

Cited by 3 publications

References 51 publications

Mobility of Dissolved Gases in Smectites under Saturated Conditions: Effects of Pore Size, Gas Types, Temperature, and Surface Interaction

Mobility of Dissolved Gases in Smectites under Saturated Conditions: Effects of Pore Size, Gas Types, Temperature, and Surface Interaction

Molecular Simulation of H₂ Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage

Modeling Solubility Induced Elemental Fractionation of Noble Gases in Oils

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Diffusive transport of gases in saturated nanopores: Caprock leakage from a molecular simulation perspective

Cited by 3 publications

References 51 publications

Mobility of Dissolved Gases in Smectites under Saturated Conditions: Effects of Pore Size, Gas Types, Temperature, and Surface Interaction

Mobility of Dissolved Gases in Smectites under Saturated Conditions: Effects of Pore Size, Gas Types, Temperature, and Surface Interaction

Molecular Simulation of H2 Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage

Modeling Solubility Induced Elemental Fractionation of Noble Gases in Oils

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Molecular Simulation of H₂ Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage