Kerogen thermal maturity and content of organic-rich mudrocks determined using stochastic linear regression models applied to diffuse reflectance IR Fourier transform spectroscopy (DRIFTS)

Craddock, Paul R.; Prange, Michael; Pomerantz, Andrew E.

doi:10.1016/j.orggeochem.2017.05.005

Cited by 40 publications

(19 citation statements)

References 39 publications

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“…Without direct sampling of cerean material, carbonaceous (C) chondrite meteorites and insoluble organic matter (IOM) extracted from them, as well as other types of refractory organic matter, may act as useful material analogs for organics on Ceres (De Sanctis et al, 2017;McSween et al, 2017;Moroz et al, 1998;Vernazza et al, 2005). Laboratory measurements of such materials exhibit correlations between NIR spectral features and independently measured H/C ratios and total organic content (Craddock et al, 2017;Kaplan & Milliken, 2016, 2018, and by applying these relationships to Dawn VIR data we provide new constraints on the abundance, composition (H/C), and potential origin of aliphatic compounds on Ceres. terrestrial kerogen (Alexander et al, 2017;Gilmour, 2003;Pizzarello et al, 2006;Schmitt-Kopplin et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

New Constraints on the Abundance and Composition of Organic Matter on Ceres

Kaplan

Milliken

Alexander

2018

Geophysical Research Letters

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Near‐infrared reflectance spectra from the Dawn mission at Ceres were recently found to exhibit a 3.4 μm absorption indicative of the presence of aliphatic organic compounds. Constraints on abundance and composition of these organics are necessary to inform discussions of their origin. We model reflectance spectra of organic‐bearing regions on Ceres using laboratory spectra of insoluble organics of known composition extracted from terrestrial sedimentary rocks (i.e., kerogens) and carbonaceous chondrite meteorites (i.e., insoluble organic matter, IOM). The 3.4 μm aliphatic organic absorptions observed in Dawn near‐infrared data are stronger than those observed in lab spectra of carbonaceous chondrites, and modeling requires 45% to 65% spectral fraction of IOM to fit spectra from Ceres. The spectral fraction of kerogen necessary to fit the same Ceres spectra ranges from 5% to 15% depending on the hydrogen to carbon ratio of the kerogen. Any proposed mechanism of organic delivery or formation on Ceres should explain the presence of highly concentrated IOM or why the composition is distinct from meteorite‐derived IOM if lower organic abundances are considered more plausible.

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Section: Introductionmentioning

confidence: 99%

New Constraints on the Abundance and Composition of Organic Matter on Ceres

Kaplan

Milliken

Alexander

2018

Geophysical Research Letters

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“…When investigating the molecular structure of kerogen, different kinds of techniques are usually used, such as element analysis, solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy (Vandenbroucke and Largeau, 2007). Several kerogen structural models have been built based on the qualitative or semiquantitative information provided by these methods (Requejo et al, 1992;Orendt et al, 2013;Craddock et al, 2017;Hackley et al, 2017;Longbottom et al, 2017;Stock et al, 2017). In addition, these 3D kerogen models have been used in methane adsorption and micropore structure analysis (Huang et al, 2017).…”

Section: Molecular Structure Of Kerogen In the Longmaxi Shale: Insighmentioning

confidence: 99%

Molecular Structure of Kerogen in the Longmaxi Shale: Insights from Solid State NMR, FT‐IR, XRD and HRTEM

Wang

Zhu

Liu

et al. 2019

Acta Geologica Sinica (Eng)

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Kerogen plays an important role in shale gas adsorption, desorption and diffusion. Therefore, it is necessary to characterize the molecular structure of kerogen. In this study, four kerogen samples were isolated from the organic-rich shale of the Longmaxi Formation. Raman spectroscopy was used to determine the maturity of these kerogen samples. Highresolution transmission electron microscopy (HRTEM), 13 C nuclear magnetic resonance ( 13 C NMR) , X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were conducted to characterize the molecular structure of the shale samples. The results demonstrate that VR eqv of these kerogen samples vary from 2.3% to 2.8%, suggesting that all the kerogen samples are in the dry gas window. The macromolecular carbon skeleton of the Longmaxi Formation kerogen is mainly aromatic (f a '=0.56). In addition, the aromatic structural units are mainly composed of naphthalene (23%), anthracene (23%) and phenanthrene (29%). However, the aliphatic structure of the kerogen macromolecules is relatively low (f al * +f al H =0.08), which is presumed to be distributed in the form of methyl and short aliphatic chains at the edge of the aromatic units. The oxygen-containing functional groups in the macromolecules are mainly present in the form of carbonyl groups (f a c =0.23) and hydroxyl groups or ether groups (f al O =0.13). The crystallite structural parameters of kerogen, including the stacking height (L c =22.84 Å), average lateral size (L a =29.29 Å) and interlayer spacing (d 002 =3.43 Å), are close to the aromatic structural parameters of anthracite or overmature kerogen. High-resolution transmission electron microscopy reveals that the aromatic structure is well oriented, and more than 65% of the diffractive aromatic layers are concentrated in the main direction. Due to the continuous deep burial, the longer aliphatic chains and oxygen-containing functional groups in the kerogen are substantially depleted. However, the ductility and stacking degree of the aromatic structure increases during thermal evolution. This study provides quantitative information on the molecular structure of kerogen samples based on multiple research methods, which may contribute to an improved understanding of the organic pores in black shale.

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“…The disappearance of the D band in the uppermost stage of maturity also verifies this phenomenon. (A) The same plot using data from other sources (red circles) [5,85,86], including samples in this study (blue circles) with R 2 75%; (Right) HI for data from other sources was calculated based on the definition, as they did not report HI directly. Note the negative correlation that corresponds to less hydrogen content of organic matter by increasing aromaticity.…”

Section: Pi = S1mentioning

confidence: 99%

“…Correlating S1 and S2 with G and D band positions, provides us with a path to correlate the PI from Rock-Eval with PI derived from Raman signals based on the definition of PI (Equation (3)), Figure 15. Data from other sources (red circles) [5,85,86], including samples in this study (blue circles) with 78% R 2 . PI data from other sources were calculated based on the definition, as they did not report PI directly.…”

Section: Pi = S1mentioning

confidence: 99%

Evaluating Molecular Evolution of Kerogen by Raman Spectroscopy: Correlation with Optical Microscopy and Rock-Eval Pyrolysis

Khatibi

Ostadhassan

Tuschel³

et al. 2018

Energies

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Vitrinite maturity and programmed pyrolysis are conventional methods to evaluate organic matter (OM) regarding its thermal maturity. Moreover, vitrinite reflectance analysis can be difficult if prepared samples have no primary vitrinite or dispersed widely. Raman spectroscopy is a nondestructive method that has been used in the last decade for maturity evaluation of organic matter by detecting structural transformations, however, it might suffer from fluorescence background in low mature samples. In this study, four samples of different maturities from both shale formations of Bakken (the upper and lower members) Formation were collected and analyzed with Rock-Eval (RE) and Raman spectroscopy. In the next step, portions of the same samples were then used for the isolation of kerogen and analyzed by Raman spectroscopy. Results showed that Raman spectroscopy, by detecting structural information of OM, could reflect thermal maturity parameters that were derived from programmed pyrolysis. Moreover, isolating kerogen will reduce the background noise (fluorescence) in the samples dramatically and yield a better spectrum. The study showed that thermal properties of OM could be precisely reflected in Raman signals.

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Kerogen thermal maturity and content of organic-rich mudrocks determined using stochastic linear regression models applied to diffuse reflectance IR Fourier transform spectroscopy (DRIFTS)

Cited by 40 publications

References 39 publications

New Constraints on the Abundance and Composition of Organic Matter on Ceres

New Constraints on the Abundance and Composition of Organic Matter on Ceres

Molecular Structure of Kerogen in the Longmaxi Shale: Insights from Solid State NMR, FT‐IR, XRD and HRTEM

Evaluating Molecular Evolution of Kerogen by Raman Spectroscopy: Correlation with Optical Microscopy and Rock-Eval Pyrolysis

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