Predicting adsorbed gas capacity of deep shales under high temperature and pressure: Experiments and modeling

Zhou, Shangwen; Wang, Hongyan; Li, Bobo; Li, Shuangshuang; Sepehrnoori, Kamy; Cai, Jianchao

doi:10.46690/ager.2022.06.05

Cited by 23 publications

(16 citation statements)

References 30 publications

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“…This is because increasing the pressure results in more molecules striking the surface, favouring the adsorption process. Moreover, the loading of all three gases increases sharply at low pressures (0-4 MPa) and gradually slows down, which is in agreement with previous similar studies [25,40]. This can be explained by the fact that on the solid surface, there are a certain number of adsorption sites that can adsorb gas molecules.…”

Section: Influence Of Pore Sizesupporting

confidence: 91%

“…An adsorption model is essential for describing the adsorption process and determining the maximum adsorption amount. For this reason, numerous adsorption models, that are based on various theories, including monolayer adsorption, multilayer adsorption and micropore filling, have been developed over the years [25]. The data obtained from molecular simulations were fitted with two commonly used isotherm models, Langmuir and Freundlich.…”

Section: Data Analysis: Adsorption Isothermsmentioning

confidence: 99%

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Adsorption and Displacement of Methane in Carbon Nanoslits: Insights from Molecular Simulations

Bekeshov¹,

Ashimov²,

Wang³

et al. 2022

Preprint

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Shale gas and coalbed methane are energy sources that partly or even mainly consist of methane stored in an adsorbed state in the pores of the organic-rich rock and coal seams. In this study, the graphene nanoslit model is employed to model the nanometer slit pores in shale and coal. The Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) modelling methods are used to investigate the mechanisms of adsorption and displacement of methane in the slit pore. It was found that the CVFF forcefield resulted in the largest adsorption amount, while the PCFF forcefield resulted in the least. The COMPASS and COMPASS II force fields led to similar results. As the width of the slit pore increases, the adsorption amount of gas molecules increases, and the number density profile of adsorbed methane molecules alters from a single adsorption layer to multi-adsorption layers. The minimum slit pore width at which methane molecules can penetrate the slit pore was found to be 0.7 nm. Moreover, it is demonstrated that by lowering the temperature, the adsorption rate of the methane increases since the adsorption is an exothermic process. Enhancing methane recovery was investigated by the injection of gases such as CO2 and N2 to displace the adsorbed methane. The comparison of adsorption isotherms of gas molecules provided the following order in terms of the amount of adsorption: CO2&gt;CH4&gt;N2.

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Section: Influence Of Pore Sizesupporting

confidence: 91%

Section: Data Analysis: Adsorption Isothermsmentioning

confidence: 99%

Adsorption and Displacement of Methane in Carbon Nanoslits: Insights from Molecular Simulations

Bekeshov¹,

Ashimov²,

Wang³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…In addition, Milliken et al [ 31 ] cautiously pointed out that the development of OM-hosted pores within Marcellus shales does not display a dependence on thermal maturity in the gas window, but rather on the heterogeneity of OM types. Formation of OM-hosted pores may also be dependent on OM compositions during thermal evolution, because the hydrocarbon generation temperatures, the kerogen decomposition rates, and the chemical compositions vary for the organic particles in different source rocks [ 39 , 40 ]. Therefore, the importance of OM types in the generation of OM-hosted pores has also been a controversial subject.…”

Section: Resultsmentioning

confidence: 99%

Microstructural Analysis of Organic-Rich Shales: Insights from an Electron Microscopic Study by Application of FIBSEM and TEM

et al. 2022

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Matrix-related pores play a significant role in controlling hydrocarbon production in organic-rich shales. Multiple matrix-related pore types of typical marine shales in the Sichuan Basin have been visually investigated and identified by transmission electron microscopy (TEM) on ultra-thin sections and by focused ion beam-scanning electron microscopy (FIBSEM) on polished sections. OM-hosted pores seem universal and range in sizes from below 1 nm to hundreds of nanometers and they are not homogeneously developed and distributed, which is mainly determined by thermal maturity and OM composition. Mineral-hosted pores are defined by mineral frameworks and occur in open spaces related to ductile or rigid grain fabric. The four porous mineral types that occur are clay intrapores, carbonate solvopores, pyrite interpores, and quartz interpores, and they range in size from less than 1 nm to more than several microns. Aggregate-hosted pores are predominantly associated with clay-organic aggregates, pyrite-organic aggregates, clay-pyrite aggregates, and clay-organic-pyrite aggregates. The most common aggregate-hosted pore networks are defined by clay-organic aggregates, and the pores are largely developed between the clay and organic layers and may be the important adsorption spaces for methane. Fracture-related pores include microchannels and microfractures of various sizes and shapes and they could play a key role in providing hydrocarbon migration pathways. FIBSEM and TEM show direct evidence that OM-hosted pores and fracture-related pores contribute more to the effective pore network and the excellent reservoir quality, whereas poor reservoir quality may come from aggregate-hosted pores.

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“…Porous matrixes can be further divided into organic matter and inorganic matter. As nanopores inside the organic matter have extremely large internal surface area with strong affinity to methane, up to 20–85% of total shale gas initially in place could be adsorbed gas. − The production of this gas in place is strongly influenced by shale permeability. During the gas extraction process, reservoir pressure gradually declines, leading to an effective stress increase, rock compaction, and intrinsic permeability change.…”

Section: Introductionmentioning

confidence: 99%

A Review of Swelling Effect on Shale Permeability: Assessments and Perspectives

et al. 2023

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The significant effect of gas sorption induced swelling on shale permeability has been observed through laboratory measurements and explained through permeability models over the past decades. However, there are lab observations that cannot be explained by these models. This knowledge gap prompts this review. Our goal is to form perspectives on how to resolve this gap through assessing the role of swelling on shale permeability. This goal is achieved through the following three steps: (1) collection of experimental shale permeability data measured under both constant effective stress and constant confining pressure conditions; (2) collection and classification of shale permeability models under the influence of gas sorption induced swelling strains; (3) assessments of co-relations between shale permeability data and permeability models. On the basis of all assessments, we conclude that the discrepancies between model predictions and laboratory measurements depend on the relation between bulk and pore swelling strains, pore size scales, and consistencies of strain treatments in the experiments and models. Models assuming that bulk swelling strain is different from pore swelling strain can better explain lab observations than those assuming that they are the same. When the pore size transitions from the micron-scale to the nano-scale, the effect of swelling on shale permeability gradually diminishes. The inconsistencies between how swelling strains are measured in the lab and treated in the models are common in the literatures and affect the discrepancies between model predictions and lab observations. On the basis of these assessments, we form our perspectives: (1) transformation between bulk and pore swelling strains should be characterized and incorporated both for experiments and in permeability models; (2) shale multiscale pore structural characteristics should be characterized when assessing the swelling effect on shale permeability; (3) the time-dependent nature of swelling strain and permeability evolution should be incorporated into future experiments and permeability models.

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Predicting adsorbed gas capacity of deep shales under high temperature and pressure: Experiments and modeling

Abstract: gas capacity of deep shales under high temperature and pressure:

Cited by 23 publications

References 30 publications

Adsorption and Displacement of Methane in Carbon Nanoslits: Insights from Molecular Simulations

Adsorption and Displacement of Methane in Carbon Nanoslits: Insights from Molecular Simulations

Microstructural Analysis of Organic-Rich Shales: Insights from an Electron Microscopic Study by Application of FIBSEM and TEM

A Review of Swelling Effect on Shale Permeability: Assessments and Perspectives

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