The unclear understanding of the source rock characteristics for the Paleogene Dongying Formation in the Bozhong Sag leads to the lack of cognition in oil and gas exploration. This research systematically evaluated the discrepancy in geochemical characteristics of source rock intervals in the Dongying Formation based on detailed analysis using Rock‐Eval pyrolysis, total organic carbon (TOC), vitrinite reflectance (Ro), maceral components, stable carbon isotopes and biomarker parameters. It discusses the organic matter sources, depositional environment, thermal maturity and hydrocarbon generation potential in the source rock intervals of the Dongying Formation. The organic matter abundance in the third member (E3d3) and lower sub‐member of the second member (E3d2L) of the Dongying Formation is higher, with an average TOC of 2.08% and 1.03%, respectively, indicating that these source rock intervals could have good and excellent quality. The source rocks of the Dongying Formation predominately contain exinite maceral group and type II1 and II2 kerogen. The thermal evolution is mainly in the low‐mature and mature stages. The organic matter sources in the Dongying Formation are mainly dominated by mixed origin (the carbon isotope reversal of aromatics also provides a potential explanation). However, the values of 1,2,5−/1,3,6‐trimethylnaphthalene, (1,2,5,6 + 1,2,3,5)‐tetramethylnaphthalene/tetramethylnaphthalenes, methyldibenzofuran/methylphenanthrene (MDBF/MP) and dibenzofuran/phenanthrene (DBF/PHEN) parameters in the E3d3 and some samples in E3d2L decipher relatively smaller values than other source rock intervals, proving the enhancement of the contribution of lower organisms. Moreover, the terrestrial input in the bottom‐up deposition process of the Dongying Formation gradually increases. The depositional environment reveals the Dongying Formation source rocks mainly developed freshwater sulphur‐poor lacustrine facies and shallow lake‐fluvial delta facies in an open clay‐rich sedimentary environment with poor water column stratification, belonging to the typical weak oxidation–reduction depositional conditions. The comprehensive geochemical evaluation concludes that the favourable supply of lower organisms and stable clay‐rich depositional environment in the E3d3 interval of the Dongying Formation are potential explanations for the formation of lacustrine source rocks with high organic matter abundance, intermediate thermal evolution and excellent hydrocarbon generation potential, providing a good foundation for the exploration and development prospects of hydrocarbons.

中文翻译：

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渤海湾盆地渤中凹陷东营组湖相烃源岩热成熟度、有机质来源及沉积环境研究

对渤中凹陷古近系东营组烃源岩特征认识不清，导致油气勘探认识不足。本研究通过Rock-Eval热解、总有机碳（TOC）、镜质体反射率（右哦）、显微成分、稳定碳同位素和生物标志物参数。讨论了东营组烃源岩层段的有机质来源、沉积环境、热成熟度和生烃潜力。第三层段有机质丰度（E3d3）和第二个成员的下级子成员（E3d2L东营组 TOC 值较高，平均 TOC 分别为 2.08% 和 1.03%，表明该烃源岩层段品质优良。东营组烃源岩以外显岩组和II型为主1和二2干酪根。热演化主要处于低成熟和成熟阶段。东营组有机质来源主要以混合成因为主（芳烃碳同位素倒转也提供了可能的解释）。然而，1,2,5−/1,3,6-三甲基萘、(1,2,5,6 + 1,2,3,5)-四甲基萘/四甲基萘、甲基二苯并呋喃/甲基菲 (MDBF/MP) 的值E 中的和二苯并呋喃/菲 (DBF/PHEN) 参数3d3以及E中的一些样本3d2L与其他烃源岩层段相比，破译的数值相对较小，证明低等生物贡献的增强。此外，东营组自下而上的沉积过程中陆地输入逐渐增大。沉积环境揭示东营组烃源岩主要发育淡水贫硫湖泊相和浅湖河流三角洲相，处于开阔的富粘土沉积环境，水柱层理较差，属于典型的弱氧化还原沉积条件。综合地球化学评价认为，东缘地区低等生物供给良好，沉积环境稳定，富含粘土。3d3东营组层段是有机质丰度高、热演化中等、生烃潜力好的湖相烃源岩形成的潜在解释，为油气勘探开发前景提供了良好的基础。