Organic petrology of peak oil maturity Triassic Yanchang Formation lacustrine mudrocks, Ordos Basin, China

Interpretation
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Abstract

An organic petrology evaluation and a determination of solid bitumen reflectance BRo were completed for organic-rich Triassic Yanchang Formation mudrocks (n=15) from the Ordos Basin, north-central China, as part of a larger investigation of “shale gas” resources. These data were integrated with information from Rock-Eval programmed pyrolysis to show that the samples are in the peak oil window of thermal maturity and that organic matter is dominated by solid bitumen with minor amounts of type III kerogen (vitrinite and inertinite) from vascular land plants. Describing a “kerogen type” for these rocks based strictly on parameters determined from programmed pyrolysis is misleading because the original organic matter has converted to hydrocarbons (present as solid bitumen), a large proportion of which may have been expelled into adjacent reservoir facies. However, based on the comparison with immature-early mature lacustrine mudrock (Garden Gulch Member of Green River Formation) and marine shale (Boquillas Formation), we suggest that the original organic matter in the organic-rich samples examined for our study may have been type I/II kerogen with hydrogen index values of >700  mgHC/g TOC.

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Publication type Article
Publication Subtype Journal Article
Title Organic petrology of peak oil maturity Triassic Yanchang Formation lacustrine mudrocks, Ordos Basin, China
Series title Interpretation
DOI 10.1190/INT-2016-0111.1
Volume 5
Issue 2
Year Published 2017
Language English
Publisher Society of Exploration Geophysicists
Contributing office(s) Geology, Energy & Minerals Science Center
Description 13 p.
First page SF211
Last page SF223
Country China
Other Geospatial Ordos basin
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