Abstract
Determining the origin of light oil presents a significant challenge due to the diversity of genetic types and the limitation of conventional biomarkers. Diamondoid hydrocarbons, characterized by their thermal stability and enrichment in high maturity oil, are considered effective indicators for elucidating generation mechanisms and secondary alteration processes of light oils. In this study, the diamondoid distributions are examined in light oil samples from various regions (i.e., Wushi, Bozi, Dabei, Keshen, Kela, Dina, Dibei, Tuzi, Tudong, Yangtake, Yingmai, Hongqi, and Yaha) in the Kuqa Depression of the Tarim Basin, Northwest China, to discern the origin of the oils. Diamondoids concentrations and ratios in the Kuqa oils show significant variations, indicating two dominant source rock types and various maturity levels. Total diamondoid concentrations (including adamantanes, diamantanes, and triamantanes) vary from 141 to 19,137 ppm. Notably, the light oils from the Kela and Tuzi regions exhibit unusually high diamondoid concentrations (> 9000 ppm), while those from Yingmai, Hongqi, Yaha, Wushi, Keshen, and Tudong regions have relatively lower concentrations (< 2000 ppm). Employing our previously developed source facies discriminant model based on multivariate statistical analysis of multiple diamondoid indices, we suggest that the light oils from the Kela, Keshen, Yangtake, and Yaha regions are originated from lacustrine shales. In contrast, the other studied samples are inferred to primarily derive from coaly source rocks. Meanwhile, our maturity prediction model indicates that the maturity of the Kuqa oils ranges from 0.81 to 2.44 EASY%Ro. The highest maturity is found in the Kela light oils (2.3–2.5 EASY%Ro), while the lowest maturity is observed in the samples from the Wushi, Yingmai, and Hongqi areas (0.8–1.1 EASY%Ro). The formation mechanisms for some samples with anomalous diamondoid distributions are also explored. The Kela light oils, distinguished by their high maturity, abundant diamondoids, and relatively high biomarker concentrations, demonstrate a mixed origin with a notable contribution from highly mature condensates derived from the maturation of lacustrine kerogens. The Tuzi coal-derived oils, exhibiting moderate maturity (1.25% EASYRo) and characterized by elevated adamantane concentrations coupled with inconsistently relatively lower diamantane concentrations, are inferred to be condensates underwent evaporative (or migration) fractionation during upward migration from deeper reservoirs. Our findings corroborate the potential application of diamondoids as previously suggested. In summary, the diamondoid hydrocarbons provide a robust methodology for elucidating the origins, thermal maturity, and formation mechanisms of light oils, particularly within highly mature systems.
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The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.
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Acknowledgements
This work is financially supported by the National Science and Technology Major Project (Grant No. 2025ZD1400500), National Natural Science Foundation of China (Grant No. 42272164), Natural Science Foundation of Guangdong Province (Grant No. 2025A1515010879), and Basic and Applied Basic Research Project of Guangzhou City (Grant No. 2024A04J4751).
Funding
This work is financially supported by the National Science and Technology Major Project (Grant No. 2025ZD1400500), National Natural Science Foundation of China (Grant No. 42272164), Natural Science Foundation of Guangdong Province (Grant No. 2025A1515010879), and Basic and Applied Basic Research Project of Guangzhou City (Grant No. 2024A04J4751).
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H. Z. Z.: Data curation, investigation, validation, resources, writing- original draft, writing-review and editing. Y.W.S.: Data curation, investigation. Y.L.: Conceptualization, funding acquisition, methodology. Y.F.Z.: Data curation, investigation. Y.Q.X.: Conceptualization, funding acquisition, supervision. K.Z.: Data curation, investigation. B.C.L.: Data curation, investigation. W.M.J.: Data curation, funding acquisition, methodology, visualization, writing- original draft, writing-review and editing. All authors reviewed the manuscript.
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Zhang, H., Sun, Y., Li, Y. et al. Application of diamondoids in source and maturity evaluation of light oil: a case study from the Kuqa Depression of the Tarim Basin, NW China. Sci Rep (2026). https://doi.org/10.1038/s41598-026-38619-z
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DOI: https://doi.org/10.1038/s41598-026-38619-z
