Molecular dynamics simulations about isotope fractionation of methane in shale nanopores

Zhang, Wenjun; Shen, Baojian; Chen, Yilin; Wang, Tengxi; Chen, Wei

doi:10.1016/j.fuel.2020.118378

Cited by 22 publications

(18 citation statements)

References 73 publications

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“…In addition, the specific enthalpy of 13 CH 4 molecules is lower than that of 12 CH 4 molecules at both valley and peak points, which indicates that 12 CH 4 molecules have higher energy to leave the adsorption layer and transport within the nanopores than 13 CH 4 molecules. The difference in energy of molecules causes carbon isotope fractionation of methane, 9,73 and it is more pronounced in OPs, which could cause more obvious isotope fractionation. 3.3.5.…”

Section: Correlation Between Kn and Isotope Fractionationmentioning

confidence: 99%

“…4 Zhang et al investigated the fractionation of 12 CH 4 and 13 CH 4 molecules in organic nanopores using molecular dynamics (MD) simulations, and the results showed that isotope fractionation was more obvious in micropores. 9 In addition to pore size, the pore type (OP and IPs) is also a key factor affecting isotope fractionation. Experiments have shown that the characteristics of isotope fractionation are controlled by the shale component content (i.e., pore type).…”

Section: Introductionmentioning

confidence: 97%

“…Isotope fractionation is the phenomenon of differences in chemical or physical behavior of isotopic molecules . In shale gas reservoirs, isotopic variations can arise from a variety of physical and chemical processes such as adsorption/desorption, dissolution, and diffusion. − The adsorption/desorption effect can result in a partitioning of the methane isotopologues because a methane molecule with a 13 C atom ( 13 CH 4 ) has higher adsorption energy compared with a methane molecule with a 12 C atom ( 12 CH 4 ) .…”

Section: Introductionmentioning

confidence: 99%

“…Li et al conducted isothermal adsorption–degassing experiments and found that the amplitude of carbon isotope fractionation was larger in shales with smaller average pore sizes . Zhang et al investigated the fractionation of 12 CH 4 and 13 CH 4 molecules in organic nanopores using molecular dynamics (MD) simulations, and the results showed that isotope fractionation was more obvious in micropores . In addition to pore size, the pore type (OP and IPs) is also a key factor affecting isotope fractionation.…”

Section: Introductionmentioning

confidence: 99%

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Carbon Isotope Fractionation during Shale Gas Transport through Organic and Inorganic Nanopores from Molecular Simulations

Wang

Zhao

et al. 2021

Energy Fuels

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Carbon isotope fractionation is a promising method to predict gas-in-place content and evaluate the shale gas production stage. In this study, molecular simulations are conducted to investigate fractionation characteristics of 12CH4 and 13CH4 in high-Kn (Knudsen number) flows (Kn > 0.1) within organic and inorganic pores under shale reservoir conditions (353 K, 5–25 MPa). The results show that isotope fractionation is more obvious (i.e., the difference in transport capacities between 12CH4 and 13CH4 is larger) in organic pores than in inorganic pores. Methane adsorption capacity and surface roughness of pore walls are two major reasons. High-coverage adsorption in organic pores reduces the effective pore size, and the Knudsen diffusion becomes significant. Moreover, the specular reflection of molecules occurs frequently on the smooth surfaces of organic pores, which enlarges the difference in isotope diffusion capacity. Indeed, the difference in energy (specific enthalpy) transport of methane isotopes in organic and inorganic pores is the intrinsic reason for fractionation. Furthermore, the fractionation level is positively correlated with Kn due to the enhanced contribution of Knudsen diffusion and surface diffusion in high-Kn flows. In addition, the isotope fractionation level decreases as pore size increases because Kn and the contribution of the adsorbed phase to the total molar flux reduce in a large pore. Our findings and related analyses may help us to understand isotope fractionation in different pore types and sizes from the atomic level and assist future applications in engineering.

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Section: Correlation Between Kn and Isotope Fractionationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Carbon Isotope Fractionation during Shale Gas Transport through Organic and Inorganic Nanopores from Molecular Simulations

Wang

Zhao

et al. 2021

Energy Fuels

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“…It was revealed that the variation of nanopore throat size greatly changed the energy for methane entering and escaping through the throat, which resulted in desorption hysteresis. In addition, Zhang et al 23 conducted MD simulations to investigate the transport mechanisms of methane isotopologues ( 12 CH 4 and 13 CH 4 ) in CNTs with various diameters at 353 K, and found that 13 CH 4 with a stronger adsorption affinity possessed a lower desorption rate. As it is easy for methane molecules of high kinetic energy to be released from nanopores, temperature is also a very important factor for shale gas desorption.…”

Section: Introductionmentioning

confidence: 99%

Effect of external pressure on the release of methane through MFI zeolite nanochannels

Cheng

2020

RSC Adv.

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Molecular Dynamic Simulations of Proton and Water Transport Mechanism in a Nafion Pore

2023

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Herein, nonequilibrium molecular dynamics simulations are conducted to study the hydraulic permeation and vehicle transport of protons in proton exchange membranes (PEMs) with different structures. The results indicate that water molecules and hydronium ions are transported in porous PEMs in the form of clusters. Water molecules are more concentrated in the bulk areas of pores, whereas hydronium ions had a high‐density profile near the pore surface areas since sulfonate ions of the side chain exhibit a stronger adsorption effect on hydronium ions. Due to the confined pore size, the slip flow of water molecules and hydronium ions occurs near the pore surfaces and it becomes more significant as side chain separation or pore size increases. As pore size decreases, the reduction of movement region and the deep attractive potential near the pore wall lower the specific enthalpy due to enhanced molecule‐wall collisions. In addition, the transport diffusivity coefficients of positively charged hydronium ions are smaller than that of water molecules due to the stronger Coulomb interactions and hydrogen bonding with negatively charged side chains. Transport diffusivity coefficients of water molecules and hydronium ions increase as pore size and side chain separation increase.

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Molecular dynamics simulations about isotope fractionation of methane in shale nanopores

Cited by 22 publications

References 73 publications

Carbon Isotope Fractionation during Shale Gas Transport through Organic and Inorganic Nanopores from Molecular Simulations

Carbon Isotope Fractionation during Shale Gas Transport through Organic and Inorganic Nanopores from Molecular Simulations

Effect of external pressure on the release of methane through MFI zeolite nanochannels

Molecular Dynamic Simulations of Proton and Water Transport Mechanism in a Nafion Pore

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