Hydrocarbon mixture and CO2 adsorptions in A nanopore-bulk multiscale system in relation to CO2 enhanced shale gas recovery

Wang, Yingnan; Jin, Zhehui

doi:10.1016/j.cej.2020.128398

Cited by 22 publications

(12 citation statements)

References 89 publications

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“…The density of the CO 2 component shows the density peaks on the boundary of the kerogen wall, suggesting that CO 2 has a stronger adsorption ability than CH 4 on the kerogen, which reveals that CO 2 is an effective component to reduce the CH 4 adsorption, and CO 2 has been widely applied on the development of shale gas accordingly. 56,57 However, the H 2 O component presents a density enrichment, and it seems impossible that H 2 O tends to adsorb on an organic surface, which cannot be observed in the ideal organic model (CNTs and graphene layers). The reason is that the oxygen atoms in kerogen walls and H 2 O molecules can form hydrogen bonds.…”

Section: Resultsmentioning

confidence: 99%

Mechanism Analysis of Shale Gas Adsorption under Carbon Dioxide–Moisture Conditions: A Molecular Dynamic Study

2022

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In recent decades, shale gas, which has been regarded as a source of clean energy, is gradually replacing conventional energy. Shale gas adsorption in carbon dioxide (CO2)–moisture systems has been discussed in many previous studies; however, the intrinsic mechanism has not been clarified yet. In this work, the molecular dynamic (MD) method is adopted to study the adsorption behaviors of shale gas adsorption in the realistic kerogen nanoslit. The spatial density distributions of shale gas and different components have strong inhomogeneity. To reveal the heterogeneous adsorption mechanism, the potential of mean force (PMF) distributions of shale gas components are calculated on different target positions for the first time. The water (H2O) component prefers to adsorb on the oxygen-enriched position, as a result of the strong molecular polarity and hydrogen bond interactions. The CO2 component tends to adsorb on the carbon-rich site, which is the result of combining the van der Waals interaction and molecular polarity with kerogen walls. The potential energy contours are computed to verify the affinities between different components and the kerogen surface, and the potential energy difference can be observed between the bulk phase and adsorbed phase, which corresponds to the density and PMF analyses. The sensitivity analysis is also carried out to verify the above mechanism explanation. Higher temperature facilitates the desorption of shale gas, and higher pressure leads to more adsorption quantity. In the larger pore space, because of more content of H2O and CO2 molecules, the adsorption amount of methane (CH4) decreases. More content of CO2 is conducive to the desorption of shale gas, verified by cases in various component proportions.

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Section: Resultsmentioning

confidence: 99%

Mechanism Analysis of Shale Gas Adsorption under Carbon Dioxide–Moisture Conditions: A Molecular Dynamic Study

2022

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“…Further, the length scale relevant to shale gas storage and recovery can be comfortably explored using modern MD techniques and computing facilities. For these reasons, MD simulations have seen considerable applications in shale gas research or, more broadly, in unconventional hydrocarbon research. − From published works and our own experience, MD simulations are especially useful in three areas: (1) to furnish the thermodynamic and transport properties of nanoconfined fluids for continuum models, (2) to explore, discover, and understand new pore-scale phenomena, and (3) to guide the development of new pore-scale continuum models and validate them. MD works in these areas help better understand and predict shale gas storage and recovery at the pore scale, thus benefiting field-scale simulations.…”

Section: Primer Of Shale Gas and MDmentioning

confidence: 99%

Review on Pore-Scale Physics of Shale Gas Recovery Dynamics: Insights from Molecular Dynamics Simulations

et al. 2022

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Reliable prediction of gas recovery from shale formations is essential for achieving the full potential of shale gas. A distinguishing feature of shales is that nanoscale pores dominate their porosity. Hence, confinement and fluid−wall interactions modulate shale gas storage, transport, and recovery, which are neglected in conventional gas recovery models. Because these nanoscale effects can be simulated using molecular dynamics (MD), related works have proliferated. Here, we review MD modeling of shale gas recovery at the pore scale. The design and simulation protocols of MD systems for studying gas recovery are surveyed first. Then, the gas recovery in three scenarios, i.e., recovery of single-component gas, recovery of multicomponent gas, and gas recovery involving multiphase flows, are reviewed. In particular, works exploring and elucidating new pore-scale phenomena and guiding and validating new pore-scale continuum models are highlighted. Finally, we recommend best practices in MD shale gas studies and suggest several research directions.

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“…On the other hand, due to the continuous depletion of conventional natural gas reservoirs, shale gas has become an important natural gas source. − For example, in the United States, ∼80% of total dry natural gas production was from shale formations in 2020 . Unlike conventional reservoirs, surface adsorption plays a dominant role in shale gas due to the presence of a significant amount of nanosized pores in shale media. − Shale rocks are heterogeneous complex structural and mineralogical systems consisting of inorganic matters (calcites, quartz, pyrites, clays, etc.) and organic matters. , Kerogen is the main constituent of organic matters, which generates hydrocarbons via chemical decomposition .…”

Section: Introductionmentioning

confidence: 99%

“…and organic matters. , Kerogen is the main constituent of organic matters, which generates hydrocarbons via chemical decomposition . It is also the main methane storage site as methane adsorption capacity in shale rocks has shown a positive correlation with the total organic carbon (TOC) content. ,, Therefore, the accurate characterization of surface area in kerogen nanoporous media becomes utterly important in the prediction of shale gas-in-place (GIP). ,, …”

Section: Introductionmentioning

confidence: 99%

“…10,12,13 Therefore, the accurate characterization of surface area in kerogen nanoporous media becomes utterly important in the prediction of shale gas-in-place (GIP). 8,9,14 The Brunauer−Emmett−Teller (BET) theory has been widely used to obtain surface area by characterizing the N 2 adsorption isotherms at 77 K in various porous media: the socalled BET surface area (S BET ), including activated carbon, 15 coal, 16 metal organic frameworks (MOFs), 17−19 silica, 20−22 zeolite, 23 etc. It is also one of the standard methods to obtain surface area in shale rocks 9 and isolated kerogen.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Energetical and Geometrical Heterogeneity of Kerogen on BET Surface Area Characterization and Methane Adsorption

2022

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Surface area is an important parameter for the estimation of methane (CH4) adsorption in shale nanoporous media. Kerogen, as the main constituent of shale organic matters, has exceptionally high surface area due to extensive nanoscale pores. The Brunauer–Emmett–Teller (BET) method has been extensively used to characterize the surface area of various porous materials. However, its applicability for the surface area characterization of kerogen mesopores has not been investigated yet. In this work, the effect of geometrical and energetical heterogeneity on N2 adsorption isotherms and the subsequent BET surface area (S BET) characterization is studied by using grand canonical Monte Carlo simulations. We find that N2 adsorption sites are mainly within the “basin” and “valley” regions on kerogen surfaces, while in the “ridge” regions, its adsorption rarely takes place at 77 K from 0.005 to 0.05 bar. On the other hand, surface chemistry shows a significant effect on external potential and N2 adsorption amount. In addition, while S BET agrees well with geometric surface area (S geo) in graphite mesopores, in kerogen and pseudokerogen mesopores, S BET is generally lower than S geo. Interestingly, for our samples, S BET correlates well with CH4 excess adsorption in kerogen mesopores at 333.15 K and 300 bar, outperforming S geo. This work provides some crucially important fundamental understanding about the S BET characterization of kerogen mesopores which can guide the prediction of CH4 adsorption capacity in kerogen nanoporous media and the estimation of shale gas-in-place.

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Hydrocarbon mixture and CO2 adsorptions in A nanopore-bulk multiscale system in relation to CO2 enhanced shale gas recovery

Cited by 22 publications

References 89 publications

Mechanism Analysis of Shale Gas Adsorption under Carbon Dioxide–Moisture Conditions: A Molecular Dynamic Study

Mechanism Analysis of Shale Gas Adsorption under Carbon Dioxide–Moisture Conditions: A Molecular Dynamic Study

Review on Pore-Scale Physics of Shale Gas Recovery Dynamics: Insights from Molecular Dynamics Simulations

Effect of Energetical and Geometrical Heterogeneity of Kerogen on BET Surface Area Characterization and Methane Adsorption

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