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

Requejo, A.G.; Gray, Nancy Ryan; Freund, Howard; Thomann, H.; Melchior, M. T.; Gebhard, L. A.; Bernardo, María; Pictroski, C. F.; Hsu, Chang Samuel

doi:10.1021/ef00032a015

Cited by 55 publications

(32 citation statements)

References 6 publications

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“…The net effect of all these changes is to narrow the chemical shift dispersion, which manifests itself as a narrowing of the resonance band. The general features of the NMR spectra for the hydrous pyrolysis residues as a function of temperature are similar to those observed for maturation of petroleum source rocks (Requejo et al 1992) and coals as a function of rank (Miknis et al 1981).…”

Section: Nmr Characterization Of Hydrous Pvrolysis Residuessupporting

confidence: 66%

Solid state 13C NMR analysis of shales and coals from Laramide Basins. Final report, March 1, 1995--March 31, 1996

Miknis¹,

Jiao²,

Zhao³

et al. 1998

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Section: Nmr Characterization Of Hydrous Pvrolysis Residuessupporting

confidence: 66%

Solid state 13C NMR analysis of shales and coals from Laramide Basins. Final report, March 1, 1995--March 31, 1996

Miknis¹,

Jiao²,

Zhao³

et al. 1998

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“…Line shapes are in- termediate between Gaussian, R~ = 1.18, and Lorentzian, R~ = 1.72, and only the oxygen partial pressure surrounding the samples slightly affects the linewidth. Unlike kerogenes [14], linewidth does not decrease monotonically and R~ does not increase at higher aromaticity. Moreover linewidth broadening cannot be attributed unequivocally to unresolved hyperfine structure of the EPR spectrum due to the adjacent aromatic H atoms with a simple relation between molecular parameters as A~ or H/C ratio (Table 1) and AHpp (Table 2).…”

Section: Electron Paramagnetic Resonance Spectroscopymentioning

confidence: 80%

“…The "average" molecule of asphaltenes is represented asa very complex aromatic core surrounded and linked by aliphatic and heteroatom chains. The investigation of molecular properties of asphaltenes has been carried out both with nondestructive techniques, particularly 1H and ~3C-NMR to obtain average molecular parameters [5][6][7], FT-IR to value differences in functional groups, chiefly hydroxyl, carbonyl and adjacent aromatic CH groups [12], solid-state NMR and EPR [13,14] to evaluate the degree of condensation and substitution of aromatic rings. Moreover, destructive techniques, such as pyrolysis/gas chromatography (Py/GC) [15,16] give interesting insights into the nature of aliphatic chains and of heteroatom speciation in asphaltenes.…”

Section: Introductionmentioning

confidence: 99%

Asphaltene radicals and their interaction with molecular oxygen: an EPR probe of their molecular characteristics and tendency to aggregate

et al. 1998

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The paramagnetic species nature of different geological o¡ asphaltenes are discussed on the basis of Electron Paramagnetic Resonance (EPR) results. Free organic radicals are present in petroleum asphaltenes but their molecular nature is poorly known owing to the multiplicity of their molecular structures which causes the appearance of a single unresolved EPR signal with a linewidth of 4-6 Gauss. In spite of the poorly resolved signals the microwave power dependence of EPR line intensities gives some insights into the nature of the aromatic rings condensation. More aromatic asphaltenes show higher saturation power of the EPR lines: this fact has been explained by a spin exchange mechanism between n-n electronic clouds of adjacent molecules, supported also by some XRD evidences. Moreover, asphaltenes in argon (not paramagnetic gas) show a maximum intensity at much lower microwave power than in oxygen atmosphere (paramagnetic gas); besides, the differences in the saturation behavior for the different asphaltenes are much more evident in oxygen atmosphere. This phenomenon is suggested to be a consequence of a weak spatial complex between aromatic moieties and oxygen molecules that deeply contribute to the relaxation pathway. Synchronous fluorescence spectroscopy confirms the difference in the size of aromatic cores in asphaltenes molecules as supposed on the basis of the saturation mechanism of EPR line intensities.

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“…The distribution of methylphenanthrenes in the extracted organic matter has been found to be related to the geothermal evolution of source rocks, and the difference in concentration of the various methylphenanthrenes has been quantitatively expressed as a Methylphenanthrene Index [MPI, 1.5(2-methyl + 3-methyl)/(Phenanthrene + 1-methyl + 9-methyl)], and used as an indicator of the geo- thermal maturity (Radke, 1987). The MPI calculated from kerogen pyrolyzates was also previously used as a geothermal parameter and found to be highly variable (Requejo et al, 1992). In this research, the MPI values calculated from the pyrolysis products show that the MPI of the alginite is 0.57, the matrix is 0.73, indicating a variation of the MPI values due to organic matter type.…”

Section: Straight Chain Aliphaticsmentioning

confidence: 65%

“…In this research, the MPI values calculated from the pyrolysis products show that the MPI of the alginite is 0.57, the matrix is 0.73, indicating a variation of the MPI values due to organic matter type. Because the pyrolysis done by Requejo et al (1992) was based on bulk kerogen samples, the highly variable MPI values might be caused by the variation of the bulk kerogen in organic composition. Phenol and alkylphenols.…”

Section: Straight Chain Aliphaticsmentioning

confidence: 99%

Organic geochemical characterization of the density fractions of a Permian torbanite

Han

Kruge

Crelling

et al. 1995

Organic Geochemistry

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Abstract--Two distinct organic components, the Botryococcus-related alginite (Reinschia) and the amorphous organic matrix, were isolated by high-resolution density gradient centrifugation (DGC) from a Permian torbanite (New South Wales, Australia). On the density profile, the alginite (1.03-1.10 g/ml) and the matrix (1.16-1.21 g/ml) appear to be two distinct peaks. With fluorescence microscopy, the alginite shows bright yellow to orange fluorescence and well-preserved algal structure, whereas the matrix has a reddish brown fluorescence of medium intensity. The H/C and O/C atomic ratios indicate that the alginite is equivalent to a Type I kerogen, whereas the matrix falls into the Type II kerogen category. The more "heavy" O and S, and less "light" H content in the matrix also helps in explaining the higher density of the matrix relative to the alginite. Flash pyrolysis-GC/MS of the CH 2 Cl2-extracted density fractions shows that the pyrolyzates of both the alginite and the matrix are dominated by normal alk-l-enes and alkanes, which range up to C3~. However, these normal hydrocarbons are relatively more abundant in the alginite than in the matrix. The alginite also produced a n-ct,co-alkadiene series which was not detected in the matrix. Compared to the alginite, the matrix pyrolyzate is enriched in Ci9~C31 straight-chain aliphatics and aromatic, phenolic and hopanoid compounds, suggesting that the matrix was formed through incorporation of degraded algal material and humic matter. The higher Methylphenanthrene Index (MPI) value of the matrix pyrolyzates relative to the alginite indicates that the MPI is affected by organic matter type.

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

Cited by 55 publications

References 6 publications

Solid state 13C NMR analysis of shales and coals from Laramide Basins. Final report, March 1, 1995--March 31, 1996

Solid state 13C NMR analysis of shales and coals from Laramide Basins. Final report, March 1, 1995--March 31, 1996

Asphaltene radicals and their interaction with molecular oxygen: an EPR probe of their molecular characteristics and tendency to aggregate

Organic geochemical characterization of the density fractions of a Permian torbanite

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