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Data Release for Application of Raman spectroscopy as thermal maturity probe in shale petroleum systems: insights from natural and artificial maturation series (2018)

December 17, 2021

Raman spectroscopy was studied as a thermal maturity probe in a series of Upper Devonian Ohio Shale samples from the Appalachian Basin spanning from immature to dry gas conditions. Raman spectroscopy also was applied to samples spanning a similar thermal range created from 72-hour hydrous pyrolysis (HP) experiments of the Ohio Shale at temperatures from 300 to 360 Celcius and isothermal HP experiments lasting up to 100 days of similar Devonian-Mississippian New Albany Shale. Raman spectra were treated by an automated evaluation software based on iterative and simultaneous modeling of signal and baseline functions to decrease subjectivity. Spectra show robust correlation to measured solid bitumen reflectance (BRo) values and were therefore used to construct logarithmic regression relationships for calculation of BRo equivalent values. Raman spectra show considerable differences between natural samples and HP. residues with similar measured BRo values, indicating as-yet undetermined differences in carbon chemistry. We speculate this result may be due to differences in the sampling interactions of Raman vs. reflectance measurements, and the incomplete nature of maturation reactions in the time-limited hydrous pyrolysis residues. Samples used in this study are similar in organic assemblage (dominantly solid bitumen) to other commonly exploited North American shale petroleum systems, i.e., Bakken, Barnett, Duvernay, Fayetteville and Woodford shales. Therefore, results presented herein may be broadly applicable to other important shale plays. However, caution is suggested and Raman spectroscopy as a thermal probe may need individual calibration in each shale play due to differences in solid bitumen carbon chemistry. Samples were collected and tested between 2013 and 2018, in studies preformed by Ryder et al., 2013; Hackley and Lewan, 2018; Hackley et al., 2017; Yang et al., 2017; Hackley and Lundsdorf, 2018. Citations Ryder, R. T.; Hackley, P. C.; Hossein, A.; Trippi, M. H. Evaluation of thermal maturity in the low maturity Devonian shales of the northern Appalachian Basin.… Hackley, P. C.; Lewan, M. D., Understanding and distinguishing reflectance measurements of solid bitumen and vitrinite using hydrous pyrolysis: implications to petroleum assessment. American Association of Petroleum Geologists Bulletin 2018, 102, 1119-1140. Hackley, P. C.; Walters, C. C.; Kelemen, S. R.; Mastalerz, M.; Lowers, H. A., Organic petrology and micro-spectroscopy of Tasmanites microfossils: applications to kerogen transformations in the early oil window. Organic Geochemistry 2017, 114, 23- 44. Yang, J.; Hatcherian, J.; Hackley, P. C.; Pomerantz, A. E., Nanoscale geochemical and geomechanical characterization of organic matter in shale. Nature Communications 2017, 8, (1), 2179. Hackley P.C. and Lunsdorf N.K. Application of Raman Spectroscopy as Thermal Maturity Probe in Shale Petroleum Systems: Insights from Natural and Artificial Maturation Series Energy & Fuels 2018 32 (11), 11190-11202