| Titre | The diagenetic continuum of steroid hydrocarbon transformation from early diagenesis into the oil window |
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| Auteur | Synnott, D P; Schwark, L; Dewing, K ; Percy, E L; Pedersen, P K |
| Source | Geochimica et Cosmochimica Acta vol. 343, 2023 p. 137-155, https://doi.org/10.1016/j.gca.2022.12.013 |
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| Année | 2023 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20220605 |
| Éditeur | Elsevier |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.gca.2022.12.013 |
| Media | papier; numérique; en ligne |
| Formats | pdf |
| Sujets | matières organiques; maturation thermique; géochimie |
| Illustrations | diagrammes schématiques; coupes transversales; cartes de localisation; graphiques |
| Programme | Les géosciences de l'énergie Ressources d'énergie propre - réduire les risques environnementaux |
| Diffusé | 2023 02 01 |
| Résumé | (disponible en anglais seulement)
Steroids and their derivatives are ubiquitous in the sedimentary rock record, where they are widely applied as biological or geochemical markers to determine
organic facies as well as thermal maturation of bitumen and oils covering the diagenetic to catagenetic stages. The diagenetic continuum from early diagenesis into catagenesis of steroids has not been extensively studied despite the importance of
these reactions in influencing the successive continuum of late diagenetic transformations. This study utilizes a stratigraphically constrained transect of 9 wells from the Upper Cretaceous Second White Specks and Belle Fourche formations of
south-central Alberta, Canada ranging in thermal maturity from 0.2 %VRE to 0.8 %VRE. Biomarkers were examined from 69 samples from 8 wells and thermal maturity was determined from 87 samples from 9 wells using HAWK programmed pyrolysis analysis.
Relative and absolute abundances of regular sterane, diasterene, diasterane, monoaromatic steroid, and triaromatic steroid biomarkers and changes in the proportions of steroid compound classes were determined and evaluated for thermal maturity.
Additionally, isomerization ratios within each of the compound classes were examined with increasing thermal maturation. Rearranged diasterenes initially dominate the steroidal hydrocarbons, followed by diasteranes in the late diagenetic and
catagenetic stages and at peak oil maturity (0.8 %VRE) diasteranes were most abundant. The relative abundance of a steroid is initially controlled by its rate of production or isomerization from a biological precursor, but at higher thermal
maturities selective catagenetic destruction alters the relative abundance of steroid classes, with aromatic steroids and regular steranes being degraded or expelled earliest. Thermal maturity parameters based on the isomerization of regular
steranes, and the aromatization of monoaromatic steroids are effective thermal maturity indicators in specific but overlapping ranges beginning at 0.2 %VRE. This work represents a novel examination of a natural thermal maturity transect and helps to
consolidate our understanding and application of the diagenetic transformations of steroid compounds. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Cet article décrit comment un groupe commun de molécules organiques, appelées stéranes, change lorsqu'elles sont enfouies dans des roches
sédimentaires. Certains changements dans la structure des stéranes sont dus à l'augmentation de la température, mais d'autres changements sont dus aux microbes qui mangent les stéranes et à la réaction avec les minéraux argileux. |
| GEOSCAN ID | 331516 |
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