Study on the Adsorption Phenomenon in Shale With the Combination of Molecular Dynamic Simulation and Fractal Analysis

Zhang, Liehui; Li, Jianchao; Du, Jiapei; Zhao, Yulong; Xie, Chunyu; Tao, Zhengwu

doi:10.1142/s0218348x18400042

Cited by 26 publications

(16 citation statements)

References 43 publications

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“…The kerogen slit nanopore had smooth surfaces. Zhang et al 54 placed more than 100 different mature kerogen fragments in one large simulation box and performed MD simulations to create the kerogen matrix. Then, the kerogen slit nanopore was created by deleting atoms and bonds for a 20, 50, and 100 Å slit thickness.…”

Section: ■ Introductionmentioning

confidence: 99%

Methane Adsorption and Self-Diffusion in Shale Kerogen and Slit Nanopores by Molecular Simulations

2018

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Shale gas has redefined the energy landscape in the world. The scientific community makes efforts to exploit shale gas resources with minimum environmental impact. Shale gas is mainly located in micropores and mesopores of shale rocks. Molecular simulations provide insights into the kerogen structure frameworks and hydrocarbon and nonhydrocarbon adsorption on the kerogen-accessible surface. In this work, a new method is introduced to create kerogen slit nanopores from the molecular scale with different surface roughness. The hybrid molecular dynamics-grand canonical Monte Carlo (MD-GCMC) simulations are used to investigate methane adsorption in a rigid and flexible kerogen matrix and slit nanopores at three different temperatures and various pressures. Molecular dynamics simulations are used to study CH4 mobility in the flexible kerogen matrix and slit nanopores. Our simulation results show that the kerogen matrix is a dynamic system in which a coupling may exist between gas adsorption and kerogen matrix structure deformation. The chemical composition and flexibility of kerogen molecules affect adsorption and self-diffusion in the kerogen matrix. Surface roughness and chemical composition have a significant effect on adsorption in the kerogen slit nanopores. The effect of kerogen molecular flexibility on self-diffusion in slit nanopores may not be significant. Our work is based on type II-A kerogen macromolecules, but our methodology for creating kerogen slit nanopores can be used for other types of kerogen molecules.

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Section: ■ Introductionmentioning

confidence: 99%

Methane Adsorption and Self-Diffusion in Shale Kerogen and Slit Nanopores by Molecular Simulations

2018

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“…Moreover, adsorbed gas and dissolved gas can be transformed to the other under proper circumstances. Therefore, it can be roughly seen as one type in some cases [48,64].…”

Section: Dissolved Gasmentioning

confidence: 99%

Review of Formation and Gas Characteristics in Shale Gas Reservoirs

et al. 2020

Self Cite

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An accurate understanding of formation and gas properties is crucial to the efficient development of shale gas resources. As one kind of unconventional energy, shale gas shows significant differences from conventional energy ones in terms of gas accumulation processes, pore structure characteristics, gas storage forms, physical parameters, and reservoir production modes. Traditional experimental techniques could not satisfy the need to capture the microscopic characteristics of pores and throats in shale plays. In this review, the uniqueness of shale gas reservoirs is elaborated from the perspective of: (1) geological and pore structural characteristics, (2) adsorption/desorption laws, and (3) differences in properties between the adsorbed gas and free gas. As to the first aspect, the mineral composition and organic geochemical characteristics of shale samples from the Longmaxi Formation, Sichuan Basin, China were measured and analyzed based on the experimental results. Principles of different methods to test pore size distribution in shale formations are introduced, after which the results of pore size distribution of samples from the Longmaxi shale are given. Based on the geological understanding of shale formations, three different types of shale gas and respective modeling methods are reviewed. Afterwards, the conventional adsorption models, Gibbs excess adsorption behaviors, and supercritical adsorption characteristics, as well as their applicability to engineering problems, are introduced. Finally, six methods of calculating virtual saturated vapor pressure, seven methods of giving adsorbed gas density, and 12 methods of calculating gas viscosity in different pressure and temperature conditions are collected and compared, with the recommended methods given after a comparison.

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“…The desorption amount is far less than the adsorption amount, and then hysteresis loop appeared. There are significant differences in the development morphology and connectivity of small pores and the adsorption of nitrogen is not fully enclosed [18].…”

Section: Low-pressure Nitrogen Adsorption-desorption Experimentsmentioning

confidence: 99%

“…where P is the equilibrium pressure; V is the volume of adsorbed gas corresponding to equilibrium pressure P; P 0 is the saturation pressure, K is the slope of the logarithmic curve, which is related to the adsorption mechanism and K = D − 3; C is a constant. If the pores has fractal characteristics, lnV and ln(ln(P 0 /P)) will have a linear relationship [18].…”

Section: Principle and Fractal Dimension Calculation Processmentioning

confidence: 99%

Fractal Characterization of Nanopore Structure in Shale, Tight Sandstone and Mudstone from the Ordos Basin of China Using Nitrogen Adsorption

Li¹,

Gao²,

Fang

et al. 2019

Energies

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The characteristics of the nanopore structure in shale, tight sandstone and mudstone from the Ordos Basin of China were investigated by X-ray diffraction (XRD) analysis, porosity and permeability tests and low-pressure nitrogen adsorption experiments. Fractal dimensions D1 and D2 were determined from the low relative pressure range (0 < P/P0 < 0.4) and the high relative pressure range (0.4 < P/P0 < 1) of nitrogen adsorption data, respectively, using the Frenkel–Halsey–Hill (FHH) model. Relationships between pore structure parameters, mineral compositions and fractal dimensions were investigated. According to the International Union of Pure and Applied Chemistry (IUPAC) isotherm classification standard, the morphologies of the nitrogen adsorption curves of these 14 samples belong to the H2 and H3 types. Relationships among average pore diameter, Brunner-Emmet-Teller (BET) specific surface area, pore volume, porosity and permeability have been discussed. The heterogeneities of shale nanopore structures were verified, and nanopore size mainly concentrates under 30 nm. The average fractal dimension D1 of all the samples is 2.1187, varying from 1.1755 to 2.6122, and the average fractal dimension D2 is 2.4645, with the range from 2.2144 to 2.7362. Compared with D1, D2 has stronger relationships with pore structure parameters, and can be used for analyzing pore structure characteristics.

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Study on the Adsorption Phenomenon in Shale With the Combination of Molecular Dynamic Simulation and Fractal Analysis

Cited by 26 publications

References 43 publications

Methane Adsorption and Self-Diffusion in Shale Kerogen and Slit Nanopores by Molecular Simulations

Methane Adsorption and Self-Diffusion in Shale Kerogen and Slit Nanopores by Molecular Simulations

Review of Formation and Gas Characteristics in Shale Gas Reservoirs

Fractal Characterization of Nanopore Structure in Shale, Tight Sandstone and Mudstone from the Ordos Basin of China Using Nitrogen Adsorption

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