ESR assessment of kerogen maturation and its relation with petroleum genesis

Bakr, M.; Aoki, Masahiko; Sanada, Yuzo

doi:10.1016/0146-6380(90)90104-8

Cited by 27 publications

(13 citation statements)

References 3 publications

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“…Spin density has been shown to increase monotonically with increasing maturity in solvent-extracted kerogens. 18 Similar trends have been reported for both artificially-and naturally-matured samples.16,70 A reversal in the carbon radical density at elevated maturities reported in earlier studies18,70-72 was not observed in the Duvernay samples. These reversals are generally observed at maturities approaching 2.0% vitrinite reflectance, a level which has not been reached by any of the Duvernay samples examined.…”

Section: Methodssupporting

confidence: 76%

See 1 more Smart Citation

Maturation of petroleum source rocks. 1. Changes in kerogen structure and composition associated with hydrocarbon generation

Requejo¹,

Gray²,

Freund³

et al. 1992

Energy Fuels

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Section: Methodssupporting

confidence: 76%

“…An exchange narrowing mechanism has previously been invoked to account for the decrease in EPR line width with increasing maturation. 18 The exchange interaction becomes more significantly enhanced if aromatic moieties are more highly associated, as expected in more mature kerogens.…”

Section: Methodsmentioning

confidence: 88%

Maturation of petroleum source rocks. 1. Changes in kerogen structure and composition associated with hydrocarbon generation

Requejo¹,

Gray²,

Freund³

et al. 1992

Energy Fuels

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“…This effect is due to the gradual decrease of heteroatom content as well to a decrease of the H/C ratio, which causes the T 1e value to increase because the exchange interaction becomes more significant within more ordered aromatic moieties, as expected for the more mature samples. The measured maturation trend in the line width for petrographic constituents of bituminous coals is opposite to the trend observed for kerogen . The most plausible explanation for the lack of consistency is the difference in summary effect of molecular structure and intermolecular interactions in these materials.…”

Section: Resultsmentioning

confidence: 61%

“…Namely, with maturation there is a concomitant decrease of heteroatom content as well as an increase in the average aromatic core size accompanied by a higher degree of association of aromatic moieties. An exchange-narrowing mechanism has been invoked to account for the decrease in EPR line width with increasing kerogen maturation . However, an increase in the association of the polyaromatic core would disable electron delocalization, which leads to the increased electron−electron interaction reflected in line broadening.…”

Section: Resultsmentioning

confidence: 99%

EPR Studies on Petrographic Constituents of Bituminous Coals, Chars of Brown Coals Group Components, and Humic Acids 600 °C Char upon Oxygen and Solvent Action

Czechowski

Jezierski

1997

Energy Fuels

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Free radicals were characterized in petrographic constituents of bituminous coals and in chars from brown coal components by EPR. The change in free radical concentration on oxidation of humic acid 600 °C char from humodetritous brown coal with gaseous 10% oxygen at 330 °C was evaluated. Spin concentration in the petrographic constituents from a bituminous coal increases in the order liptinite < vitrinite , inertinite. Increasing maturity of each petrographic constituent correlates with an increase in spin concentration and decrease in g-value. Heat treatment of brown coal group components (bitumens, cellulose, lignin, humic acids, and residual coal) leads to the formation of free radicals up to a temperature of about 550 °C and to their sharp disappearance at higher temperatures. Strongly marked maxima in the spin concentration of the chars are observed at atomic H/C ratios in the range 0.40-0.42 and O/C ratios in the range 0.08-0.10. Increasing heat treatment temperature causes a steady decrease in g-value from about 2.0040 to 2.0025. Treatment of the 600 and 700 °C chars with organic solvents resulted in an increase in their spin concentration. This effect was particularly strong in the case of treatment with tetralin and naphthalene. Burning off humic acid 600 °C char with 10% oxygen at 330 °C leads to a decrease in spin concentration in oxidized products. Structural units associated with elevated char free radicals density were more prone to oxidation and presumably are peripheral polyaromatic skeletons of lower structural ordering.

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“…The radicals and other highly reactive products that are not able to find sites to react with remain in the kerogen. Similarly, it has been demonstrated experimentally 65,66 that demineralized kerogens contain uncoupled electrons at concentrations of 10 17 −10 19 cm −3 . The newly developed reaction sites (e.g., carbon radicals) can also satisfy their reactivity through covalent bond formation with hydrogen atoms present in the kerogen or with olefinic moieties formed by β scission.…”

Section: Energy and Fuelsmentioning

confidence: 65%

Reactive Molecular Dynamics Simulation of Kerogen Thermal Maturation and Cross-Linking Pathways

2017

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Molecular dynamics simulations were performed with a ReaxFF reactive force field to investigate bond breaking and bond formation mechanisms during the thermal maturation of three kerogens and potential cross-linking pathways toward the formation of three-dimensional (3D) quasi-infinite molecular networks (cross-linked kerogen macromolecules). Starting with small ensembles of high molecular mass models for immature type I Green River Shale kerogen (kerogen 1-I), top of the oil window type II kerogen (kerogen 2-L), and low maturity type III kerogen (kerogen 3-L), low molecular mass species including H2O, C2H4, and C3H6 were produced as the maturities of the remaining kerogens increased. Highly reactive fragments, which are not detected in pyrolysis experiments, were also produced. Further, the cross-linking mechanisms in the newly developed polymeric kerogen networks appear to be highly complex, and covalent C–S, C–O, and C–C bonds were the primary cross-links that structurally bond kerogen monomers together. The trends observed in the simulated thermochemical transformation of kerogen and the kerogen cross-linking pathways are consistent with theoretical and experimental studies reported in the scientific literature. Reactive force field molecular dynamics simulation provides a potentially valuable approach to the development of realistic three-dimensional models for kerogen molecular networks. However, the conversion of kerogen molecules into a 3D cross-linked molecular network was low (the density of the intermolecular cross-links was low).

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ESR assessment of kerogen maturation and its relation with petroleum genesis

Cited by 27 publications

References 3 publications

Maturation of petroleum source rocks. 1. Changes in kerogen structure and composition associated with hydrocarbon generation

Maturation of petroleum source rocks. 1. Changes in kerogen structure and composition associated with hydrocarbon generation

EPR Studies on Petrographic Constituents of Bituminous Coals, Chars of Brown Coals Group Components, and Humic Acids 600 °C Char upon Oxygen and Solvent Action

Reactive Molecular Dynamics Simulation of Kerogen Thermal Maturation and Cross-Linking Pathways

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