Standardization of reflectance measurements in dispersed organic matter: Results of an exercise to improve interlaboratory agreement

Hackley, Paul C.; Araujo, Carla Viviane; Borrego, Ángeles G.; Bouzinos, Antonis; Cardott, Brian J.; Cook, A. C.; Eble, Cortland F.; Flores, Deolinda; Gentzis, Thomas; Gonçalves, Paula Alexandra; Filho, João Graciano Mendonça; Hámor-Vidó, Mária; Jelonek, Iwona; Kommeren, K.; Knowles, Wayne; J, Kuś; Mastalerz, María; Menezes, Taíssa Rêgo; Newman, J.; Oikonomopoulos, I.; Pawlewicz, Mark J.; Pickel, W.; Potter, J.; Ranasinghe, P.; Read, Harold; Reyes, Julito; Rodriguez, Genaro De La Rosa; Souza, Igor Viegas Alves Fernandes de; Suárez‐Ruíz, Isabel; Sýkorová, Ivana; Valentine, Brett J.

doi:10.1016/j.marpetgeo.2014.07.015

Cited by 131 publications

(48 citation statements)

References 17 publications

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“…This can be a difficult undertaking due to low concentrations of kerogen, presence of other types of organic matter (such as solid bitumen, which is not a kerogen) that have similar optical properties, vitrinite reflectance suppression, and the physical quality of the sample and its preparation (Lo, 1993;Mukhopadhyay, 1994;Lo and Cardott, 1995). Finally, interlaboratory studies to evaluate the reproducibility of VRo measurements suggested use of a common methodology improved measurement accuracy but that significant improvements were still required (Hackley et al, 2015).…”

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confidence: 99%

Assessment of Thermal Maturity Trends in Devonian–Mississippian Source Rocks Using Raman Spectroscopy: Limitations of Peak-Fitting Method

et al. 2017

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The thermal maturity of shale is often measured by vitrinite reflectance (VRo). VRo measurements for the Devonian-Mississippian black shale source rocks evaluated herein predicted thermal immaturity in areas where associated reservoir rocks are oil-producing. This limitation of the VRo method led to the current evaluation of Raman spectroscopy as a suitable alternative for developing correlations between thermal maturity and Raman spectra. In this study, Raman spectra of Devonian-Mississippian black shale source rocks were regressed against measured VRo or sample-depth. Attempts were made to develop quantitative correlations of thermal maturity. Using sample-depth as a proxy for thermal maturity is not without limitations as thermal maturity as a function of depth depends on thermal gradient, which can vary through time, subsidence rate, uplift, lack of uplift, and faulting. Correlations between Raman data and vitrinite reflectance or sample-depth were quantified by peak-fitting the spectra. Various peak-fitting procedures were evaluated to determine the effects of the number of peaks and maximum peak widths on correlations between spectral metrics and thermal maturity. Correlations between D-frequency, G-band full width at half maximum (FWHM), and band separation between the G-and D-peaks and thermal maturity provided some degree of linearity throughout most peak-fitting assessments; however, these correlations and those calculated from the G-frequency, D/G FWHM ratio, and D/G peak area ratio also revealed a strong dependence on peak-fitting processes. This dependency on spectral analysis techniques raises questions about the validity of peak-fitting, particularly given the amount of subjective analyst involvement necessary to reconstruct spectra. This research shows how user interpretation and extrapolation affected the comparability of different samples, the accuracy of generated trends, and therefore, the potential of the Raman spectral method to become an industry benchmark as a thermal maturity probe. A Raman method devoid of extensive operator interaction and data manipulation is quintessential for creating a standard method.

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Assessment of Thermal Maturity Trends in Devonian–Mississippian Source Rocks Using Raman Spectroscopy: Limitations of Peak-Fitting Method

et al. 2017

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“…Scattered types III and IV kerogen (vitrinite and inertinite) and lamellae of solid bitumen (a solid hydrocarbon) are also present. Vitrinite reflectance (VR o ) of the Green River sample is 0.31%, indicating that conditions are immature for hydrocarbon generation (Hackley et al ., ). The second sample was an organic‐rich (7 wt.% TOC) paralic shale from the Upper Cretaceous Tuscaloosa Group (lower Tuscaloosa Formation) of southern Mississippi, USA.…”

Section: Methodsmentioning

confidence: 97%

“…We used an organic‐rich [22 wt.% total organic carbon (TOC)] lacustrine oil shale from the Eocene Green River Mahogany Zone in Colorado, USA. Previous studies (Hackley et al ., ) characterized the dominant organic matter in this sample as strongly fluorescent amorphous and lamellar type I kerogen interpreted as a benthic microbial mat deposit (Fig. ).…”

Section: Methodsmentioning

confidence: 99%

Utilization of integrated correlative light and electron microscopy (iCLEM) for imaging sedimentary organic matter

Hackley

Valentine

Voortman³

et al. 2017

Journal of Microscopy

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Summary We report here a new microscopic technique for imaging and identifying sedimentary organic matter in geologic materials that combines inverted fluorescence microscopy with scanning electron microscopy and allows for sequential imaging of the same region of interest without transferring the sample between instruments. This integrated correlative light and electron microscopy technique is demonstrated with observations from an immature lacustrine oil shale from the Eocene Green River Mahogany Zone and mid‐oil window paralic shale from the Upper Cretaceous Tuscaloosa Group. This technique has the potential to allow for identification and characterization of organic matter in shale hydrocarbon reservoirs that is not possible using either light or electron microscopy alone, and may be applied to understanding the organic matter type and thermal regime in which organic nanoporosity forms, thereby reducing uncertainty in the estimation of undiscovered hydrocarbon resources.

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“…Detailed sample preparation and analysis procedures are described in the ASTM D7708 standard test method (2014) and by Hackley et al (2015). Briefly, whole-rock (WR) samples were crushed to 20 mesh (850 μm or 0.85 mm size) particles.…”

Section: Vitrinite Reflectance (R O )mentioning

confidence: 99%

“…Sample grinding and polishing were performed using Buehler EcoMet/AutoMet 250 automated polishing equipment. The sample surface should be scratch-and relief-free for reliable Ro measurements because poorly polished surfaces can lower the R o values (e. g., Hackley et al, 2015).…”

Section: Vitrinite Reflectance (R O )mentioning

confidence: 99%

Critical considerations when assessing hydrocarbon plays using Rock-Eval pyrolysis and organic petrology data: Data quality revisited

Carvajal‐Ortiz

Gentzis

2015

International Journal of Coal Geology

205

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Standardization of reflectance measurements in dispersed organic matter: Results of an exercise to improve interlaboratory agreement

Cited by 131 publications

References 17 publications

Assessment of Thermal Maturity Trends in Devonian–Mississippian Source Rocks Using Raman Spectroscopy: Limitations of Peak-Fitting Method

Assessment of Thermal Maturity Trends in Devonian–Mississippian Source Rocks Using Raman Spectroscopy: Limitations of Peak-Fitting Method

Utilization of integrated correlative light and electron microscopy (iCLEM) for imaging sedimentary organic matter

Critical considerations when assessing hydrocarbon plays using Rock-Eval pyrolysis and organic petrology data: Data quality revisited

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