Dispersed organic matter from pre-Devonian marine shales: A review on its composition, origin, evolution, and potential for hydrocarbon prospecting

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389005%3A_____%2F25%3A00616485" target="_blank" >RIV/61389005:_____/25:00616485 - isvavai.cz</a>

Result on the web

<a href="https://www.sciencedirect.com/science/article/pii/S0012825224003556" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0012825224003556</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.earscirev.2024.105027" target="_blank" >10.1016/j.earscirev.2024.105027</a>

Result language

angličtina

Original language name

Dispersed organic matter from pre-Devonian marine shales: A review on its composition, origin, evolution, and potential for hydrocarbon prospecting

Original language description

The pre-Devonian shales are important natural archives, preserving extensive information on paleobiology, paleoenvironment, and paleoecology, and also acting as important hydrocarbon source rocks for both unconventional and conventional petroleum systems. In China, however, most of the pre-Devonian shales are post- mature, resulting in a gradual convergence in the chemical composition and structure of organic matter (OM). This convergence complicates OM identification under optical microscope, making it challenging to trace its genesis and evolution due to similar optical characteristics. Additionally, the absence of true vitrinite particles poses an additional challenge in the evaluation of thermal maturity of these shales, a challenge that has persisted for decades. This study compares detailed optical characteristics and genesis of selected OM types, namely, graptolite, vitrinite-like maceral (VLM), solid bitumen (SB) in the pre-Devonian shales to improve identification and differentiation between these macerals. The physicochemical evolution of OM is reviewed based on the naturally and artificially matured samples, with emphasis on the organic petrology and petroleum production in some of the most extensively studied pre-Devonian shales globally. VLM and graptolites exhibit higher reflectance and stronger anisotropy than co-occurring in-source SB, with their reflectance as indicators to evaluate OM maturity in these marine shales. VLM can be distinguished from SB by its elongate and syndepositional occurrence, and from graptolites by the characteristic biological structures of graptolite. The origin of VLM is hypothesized to be a product of early diagenetic anaerobic biodegradation of lamalginite and/or bituminite in the Precambrian shales, although its origin in the Cambrian shales remains unclear. On the other hand, in-source SB is derived from the transformation of liptinites or from the cracking of the residual petroleum, or a combination thereof. Graptolites are associated with high total organic carbon (TOC), S1, S2, and hydrogen index (HI) contents, with kerogen predominantly classified as Type II-III, indicating significant hydrocarbon generation potential. Notably, in-source SB plays a significant role in gas generation. In the early mature pre-Devonian shales, OM mainly consists of lamalginite and bituminite, whereas in-source SB becomes the dominant OM in the postmature pre-Devonian shales. Non-granular graptolites are commonly observed in the Ordovician-Silurian Wufeng-Longmaxi shales, contributing significantly to OM. A comparison of naturally and artificially matured samples suggests that low-maturity liptinites transform into SB as thermal maturity increases. This finding is essential for reconstructing the original composition and hydrocarbon potential of these economically significant marine shales.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10505 - Geology

Project

<a href="/en/project/EF16_019%2F0000728" target="_blank" >EF16_019/0000728: Ultra-trace isotope research in social and environmental studies using accelerator mass spectrometry</a><br>

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Earth-Science Reviews

ISSN

0012-8252

e-ISSN

1872-6828

Volume of the periodical

261

Issue of the periodical within the volume

February

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

27

Pages from-to

105027

UT code for WoS article

001405441600001

EID of the result in the Scopus database

2-s2.0-85212953511