EPR study of kerogens from three Alaskan North Slope wells

Dickneider, Trudy A.; Whelan, Jean K.; Blough, Neil V.

doi:10.1016/0146-6380(94)00122-h

Cited by 12 publications

(2 citation statements)

References 29 publications

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“…Because the Woodford is the most thermally mature of the shales examined in this study, it is not unexpected that Woodford kerogens would exhibit a strong free radical content. EPR studies have shown a strong correlation between free radical content, vitrinite reflectance, and NMR-determined kerogen aromaticity (Dickneider et al 1995). For all other samples, T 1 H was in the range where adequate quantitation is achieved using a 1 ms contact time (Smernik and Oades 2000a,b).…”

Section: Nmr Relaxation Ratesmentioning

confidence: 98%

A solid state 13C-NMR study of kerogen degradation during black shale weathering

Petsch

Smernik

Eglinton

et al. 2001

Geochimica et Cosmochimica Acta

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Abstract-Solid state 13 C nuclear magnetic resonance (NMR) spectroscopy is used to examine kerogen composition in weathering profiles of the Monterey, Green River, Woodford, and New Albany formations. Techniques include cross polarization (CP) and Bloch decay (BD) spectral acquisition, dipolar dephasing (DD), spin counting, experiments to provide estimates of relaxation times (T 1 H and T 1 H), and proton spin relaxation editing (PSRE). It is demonstrated that CP/MAS (cross polarization/magic angle spinning) spectra obtained on isolated kerogens provide reliable characterization of kerogen composition (compared with BD spectra and whole-rock samples). Highly aliphatic (polymethylenic) kerogens are not appreciably altered during weathering. Aromatic and/or branched aliphatic kerogens accumulate oxidation products and preferentially lose aliphatic relative to aromatic carbon during weathering. No relation is observed between T 1 H times and either kerogen composition or degree of weathering; T 1 H times correlate with aromaticity. Two distinct components within kerogens are discerned by PSRE: one highly aliphatic (largely polymethylenic) component and one mixed aliphatic/aromatic component. During weathering, the highly aliphatic component remains largely unaltered, while the mixed component loses aliphatic carbon and accumulates carbonyl oxidation products. Thus it appears that kerogen weathering is dominated by two separate processes: Linear alkyl fragments are cleaved without oxidation, and aromatic/branched alkyl fragments are oxidized while attached to the kerogen macromolecule and then cleaved.

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Section: Nmr Relaxation Ratesmentioning

confidence: 98%

A solid state 13C-NMR study of kerogen degradation during black shale weathering

Petsch

Smernik

Eglinton

et al. 2001

Geochimica et Cosmochimica Acta

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“…Free radicals can be detected using the Electron Paramagnetic Resonance (EPR) method if they are maintained at steady-state . EPR has been widely used in the study of free radicals in fossil fuels, − due to its advantages, such as minor dosage, nondestructive testing, and wide detection prospects.…”

Section: Introductionmentioning

confidence: 99%

Effect of Temperature on the EPR Properties of Oil Shale Pyrolysates

Wang¹,

Ma²,

Li³

et al. 2016

Energy Fuels

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The reaction involving radical species is a key factor during the pyrolysis process used to form hydrocarbons. In this study, electron paramagnetic resonance (EPR) spectroscopy was used to characterize the properties of free radicals in the pyrolysates of oil shale. Effects of temperature on the yields and the EPR properties of thermal bitumen, shale oil, and semicoke were investigated, with the aim to understand the behavior of free radicals during the oil shale pyrolysis process. This study shows that the free radical concentrations (Ng) of shale oil and semicoke become higher with increasing temperature. The yield and Ng of thermal bitumen as an intermediate product follow the similar trends in the whole temperature range, first increasing and then decreasing. This is attributed to the competing mechnism of thermal bitumen generation and decomposition. The Ng of shale oil is lower than those of semicoke and thermal bitumen due to the coupling reaction of free radicals before the volatiles being condensed. The g-values and linewidths of thermal bitumen, shale oil, and semicoke are also affected by temperature, revealing the changing chemical structure and the surrounding environment of free radicals during the pyrolysis process.

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Temperature and time effect on the concentrations of free radicals in coal: Evidence from laboratory pyrolysis experiments

Qiu

Jin

et al. 2007

International Journal of Coal Geology

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EPR study of kerogens from three Alaskan North Slope wells

Cited by 12 publications

References 29 publications

A solid state 13C-NMR study of kerogen degradation during black shale weathering

A solid state 13C-NMR study of kerogen degradation during black shale weathering

Effect of Temperature on the EPR Properties of Oil Shale Pyrolysates

Temperature and time effect on the concentrations of free radicals in coal: Evidence from laboratory pyrolysis experiments

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