Thermal evolution of graptolite and solid bitumen properties at high maturity under natural and artificial conditions

Jin, Song; Hackley, Paul C.; Sanders, Margaret M.; Jubb, Aaron M.; Luo, Qingyong

doi:10.1016/j.coal.2023.104269

Cited by 5 publications

(1 citation statement)

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“…The term “solid bitumen” is used to describe a solid or semisolid viscous petroleum phase which is observed petrographically and has well-defined optical and spectroscopic characteristics that allow it to be distinguished from other types of sedimentary organic matter. − The measured mean reflectance of solid bitumen (symbolized BR o , in %) is increasingly used as a thermal maturity proxy in source-rock reservoirs since the advent of the shale revolution in petroleum production. − This is particularly the case in North America, where source-rock reservoir production predominantly occurs from Paleozoic marine facies in which vitrinite is rare or absent . However, despite its now widespread use, many workers still attempt to link measured BR o values to an equivalent vitrinite reflectance value (symbolized VR e in %). − Vitrinite reflectance (symbolized VR o in %) is determined by measuring light reflectance from the woody remains of vascular land plants.…”

Section: Introductionmentioning

confidence: 99%

Insights on Using Solid Bitumen Reflectance as a Thermal Maturity Proxy in the Bakken Formation, Williston Basin, USA

Hackley,

Scott,

Birdwell

et al. 2024

ACS Omega

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To further refine the use of solid bitumen reflectance (BR o in %) as a measurement of thermal maturity in source-rock reservoirs, we examined its relationship to other thermal proxies in the Bakken Formation. Comparisons included criteria from programmed temperature pyrolysis, gas chromatography (GC), and Fourier transform infrared (FTIR) spectroscopy. Thirty-two organic-rich samples from the lower and upper shale members of the Devonian−Lower Carboniferous Bakken Formation were collected from eight cores across the Williston Basin, USA, at depths (∼7575−11,330 ft) representing immature through post peak oil/early condensate thermal maturity conditions based on proximity to current hydrocarbon production. Unmodified BR o values were correlated to programmed temperature pyrolysis parameters (hydrogen index, production index, and T max ), normal hydrocarbon and isoprenoid analysis of extractable organic matter (pristane/n-C 17 and phytane/n-C 18 ) from GC analysis, and peak ratios from FTIR spectroscopy (branching ratio and A-factor). Strong correlations between unmodified BR o values (not corrected to a vitrinite reflectance equivalent, VR e ) and other thermal proxies suggest that BR o can be used as a direct thermal proxy in marine Paleozoic source-rock reservoirs where vitrinite is rare or absent. Moreover, an apparent overestimation of VR e at the lowest thermal maturity investigated herein may argue against the application of BR o conversion to VR e in the Bakken Formation. Solvent extraction caused a consistent decrease in BR o when average post-extraction values from a given well were compared to BR o prior to extraction, although the decrease in mean value was not statistically significant. These results are discussed in the context of advocating for the use of unmodified BR o values as a best practice for thermal maturity determination in Paleozoic marine source-rock reservoirs.

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