An evaluation of kerogen molecular structures during artificial maturation

Liang, Tian; Zou, Yan–Rong; Zhan, Zhigang; Lin, Xiangui; Shi, Jun; Peng, Ping’an

doi:10.1016/j.fuel.2019.116979

Cited by 32 publications

(33 citation statements)

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“…The analysis of chemical and physical properties of kerogen will aid in improved atomistic representations for use in unconventional gas extraction simulations and in following maturation transformations. Kerogen composition and structure varies widely however, being impacted by the source material, preservation during deposition, and maturation. , Multiple analytical approaches can be used to evaluate the kerogen chemical structure, including spectroscopies and NMR approaches, , image processing of HRTEM micrographs, , and degradative evaluations utilizing thermal cracking. , Physical evaluations are also performed as micropores are the main location for gas storage and are affected by the kerogen macromolecular structure. , …”

Section: Introductionmentioning

confidence: 99%

Molecular Structure Evaluation and Image-Guided Atomistic Representation of Marine Kerogen from Longmaxi Shale

et al. 2021

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Atomistic representations of kerogen, which appropriately capture chemical and physical properties, will aid in unconventional gas extraction and in following maturation transformations. Here, the structure of an overmature kerogen (from Longmaxi shale) was investigated using HRTEM, 13C NMR, XPS, and CO2 sorption evaluations. The fringe property distributions of length, angle, tortuosity, and stacking were quantified from seven HRTEM micrographs. The fringe lengths were estimated and were equivalent in size to benzene (31%), naphthalene (22%), phenanthrene (10%), 2 × 2 rings (22%), and 3 × 3 rings (9%). The stacking was limited with 10% of fringes being within a stack. However, the fringes were well aligned with 44% (range of 33–54%) of the total fringe length within a 45° angle in the major direction. The aromaticity (fa ′) was 82.2%, with aliphatic and carbonyl carbons accounting for 13.9 and 3.9%, respectively. The kerogen micropore volume was 0.06 mL/g. An image-guided construction strategy, Fringe3D, and Packmol were used to generate an atomistic structural representation that was geometry-optimized (C853H601O45N13S4). The structure incorporates the elemental compositions, carbon forms, heteroatom functionality, and aromatic molecule alignment, stacking, and curvature to generate a chemically and physically appropriate macromolecule (the model contains six macromolecules) within a small unit volume (23.5 × 23.5 × 23.5 Å).

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Section: Introductionmentioning

confidence: 99%

Molecular Structure Evaluation and Image-Guided Atomistic Representation of Marine Kerogen from Longmaxi Shale

et al. 2021

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“…Kerogen structure is not well-characterized owing to its complexity and heterogeneity; therefore, it is difficult to interpret the structure of kerogen through any single technical method. A variety of chemical methods, including Fourier transform infrared spectroscopy (FTIR), 13 C NMR, Raman spectroscopy (RS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), have been broadly utilized to obtain structural parameters of kerogen in different hydrocarbon generation stages. 17−21 For these experimental methods, 13 C NMR and FTIR are the most versatile and effective tools.…”

Section: Introductionmentioning

confidence: 99%

“…A variety of chemical methods, including Fourier transform infrared spectroscopy (FTIR), 13 C NMR, Raman spectroscopy (RS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), have been broadly utilized to obtain structural parameters of kerogen in different hydrocarbon generation stages. 17−21 For these experimental methods, 13 C NMR and FTIR are the most versatile and effective tools. Since carbon atoms are the most important part of the kerogen structure, 13 C NMR can reveal the bond environment and linkage of the aliphatic/aromatic carbon groups as well as their subgroups.…”

Section: Introductionmentioning

confidence: 99%

“…17−21 For these experimental methods, 13 C NMR and FTIR are the most versatile and effective tools. Since carbon atoms are the most important part of the kerogen structure, 13 C NMR can reveal the bond environment and linkage of the aliphatic/aromatic carbon groups as well as their subgroups. 5,22,23 FTIR is another useful technique for providing parameters for the relative content of distinct functional groups containing hydrogen, carbon, and oxygen.…”

Section: Introductionmentioning

confidence: 99%

“…Carbon dioxide adsorption experiments were utilized to determine the micropore structures of extracted kerogen samples in tectonically deformed Longmaxi shale. HRTEM, FTIR, and 13 C NMR experiments were also applied to obtain the chemical structures of kerogen in these Longmaxi shale samples. Specifically, the fringe length and orientation distributions of kerogen were extracted and analyzed.…”

Section: Introductionmentioning

confidence: 99%

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Chemical Structure Transformations in Kerogen from Longmaxi Shales in Response to Tectonic Stress as Investigated by HRTEM, FTIR, and ¹³C NMR

Shang

Tang

et al. 2021

Energy Fuels

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Kerogen molecular structure controls the micropore (<2 nm diameter) evolution in shale and exerts a significant impact on shale gas adsorption, desorption, and diffusion. However, the influence of tectonic deformation on kerogen structure and organic micropores needs intensive study. Our study mainly focuses on the transformations in the extracted kerogen structure and organic micropores of Longmaxi shale during tectonic deformation. Vitrinite reflectance measurement (VRM) and Raman spectroscopy (RS) were utilized to determine the maturity of organic matter. Organic pore network attributes of kerogen samples were estimated using CO2 adsorption experiments. High-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), and 13C nuclear magnetic resonance (13C NMR) were utilized to interpret the kerogen molecular structures of these samples. VRM and RS results show that Longmaxi shale has reached the wet gas window. Adsorption analyses of CO2 indicate that kerogen samples in shale with strong deformation have larger micropore volume and surface area (<2 nm). 13C NMR and FTIR results reveal that the tectonic stress may promote the shedding of aliphatic carbon. HRTEM images exhibit that aromatic rings with a size of 3 × 3 account for the largest proportion in all kerogen samples, which indicates that the kerogen samples have reached a high thermal evolution level, consistent with the Raman experiment. For weakly deformed shale samples, 66.5 and 88.8% of the total number of aromatic rings in LZ-1 and LZ-4 kerogen belong to the major direction (within a 45° range). In the most strongly deformed sample, LZ-2, distribution orientations of aromatic fringes are dispersed and primarily concentrated at 15–105°. Such disorientation of nanometer-sized polyaromatic layers in the strongly deformed sample creates a nanopore network in organic matter (OM) that increases the micropore volume and surface area. These findings from integrated approaches can provide a new perspective of adsorbed gas enrichment in the complex tectonic areas.

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Research on type I kerogen molecular simulation and docking between kerogen and saturated hydrocarbon molecule during oil generation

et al. 2023

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An evaluation of kerogen molecular structures during artificial maturation

Cited by 32 publications

References 48 publications

Molecular Structure Evaluation and Image-Guided Atomistic Representation of Marine Kerogen from Longmaxi Shale

Molecular Structure Evaluation and Image-Guided Atomistic Representation of Marine Kerogen from Longmaxi Shale

Chemical Structure Transformations in Kerogen from Longmaxi Shales in Response to Tectonic Stress as Investigated by HRTEM, FTIR, and ¹³C NMR

Research on type I kerogen molecular simulation and docking between kerogen and saturated hydrocarbon molecule during oil generation

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An evaluation of kerogen molecular structures during artificial maturation

Cited by 32 publications

References 48 publications

Molecular Structure Evaluation and Image-Guided Atomistic Representation of Marine Kerogen from Longmaxi Shale

Molecular Structure Evaluation and Image-Guided Atomistic Representation of Marine Kerogen from Longmaxi Shale

Chemical Structure Transformations in Kerogen from Longmaxi Shales in Response to Tectonic Stress as Investigated by HRTEM, FTIR, and 13C NMR

Research on type I kerogen molecular simulation and docking between kerogen and saturated hydrocarbon molecule during oil generation

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Chemical Structure Transformations in Kerogen from Longmaxi Shales in Response to Tectonic Stress as Investigated by HRTEM, FTIR, and ¹³C NMR