ORIGINAL RESEARCH article
Front. Earth Sci.
Sec. Geochemistry
Volume 13 - 2025 | doi: 10.3389/feart.2025.1627767
Classification of Crude Oil and Its Correlation with Terrestrial Plant Inputs Across Different Areas in the Xihu Depression, East China Sea Shelf Basin: Insights from Organic Geochemical Evidence
Provisionally accepted
- 1Key Laboratory of Marine Mineral Resources, Ministry of Natural Resources, Guangzhou Marine Geological Survey, Guangzhou, China
- 2National Engineering Research Center of Gas Hydrate Exploration and Development, Guangzhou Marine Geological Survey, Guangzhou, China
- 3School of Energy Resources, China University of Geosciences, Beijing, China
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Organic geochemical analyses were performed on 41 light crude oil samples sourced from various structural zones within the Xihu Depression. The results indicate that the oils are enriched in biomarkers reflecting substantial contributions from terrestrial higher plants, particularly tricyclic diterpanes and their aromatized derivatives originating from angiosperms, gymnosperms, and ferns.In contrast, aquatic organism-derived biomarkers were present in relatively low concentrations.Significant variations in the composition of these biomarkers across different structural zones were observed, as reflected in ratios such as isopimarane/nC20, isopimarane/(isopimarane+16β(H)phyllocladane), 1,2,5-trimethylnaphthalene/1,3,6trimethylnaphthalene, and 1,7-dimethyl-phenanthrene/(retene+1,7-dimethylphenanthrene). Statistical analysis of these compositional differences allowed for the classification of the crude oils into four distinct groups, reflecting varying relative inputs from angiosperms, gymnosperms, and ferns.Correlations between specific aliphatic and aromatic hydrocarbon fractions were also identified using comprehensive gas chromatography-mass spectrometry data. An index, formulated as the ratio of (isopimarane+1,7-DMP)/(retene+16β(H) phyllocladane), is proposed to assess the relative contributions of gymnosperm versus fern precursors to the light crude oils from the Xihu Depression.Higher values of this index indicate a greater gymnosperm contribution. A positive correlation between this index and δ 13 Coil values further supports the significant role of gymnosperm resins in hydrocarbon generation within the Xihu Depression.
Keywords: Biomarkers1, organic matter source2, organic geochemistry3, diterpanes4, oil classification5
Received: 13 May 2025; Accepted: 16 Jun 2025.
Copyright: © 2025 Jiang, Guo, Hou and Cheng. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Ruibo Guo, National Engineering Research Center of Gas Hydrate Exploration and Development, Guangzhou Marine Geological Survey, Guangzhou, China
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