渤海湾盆地沧东凹陷沙河街组烃源岩特征及沉积环境

Characteristics and depositional environment of source rocks in Shahejie Formation, Cangdong Depression, Bohai Bay Basin

赵少泽 李勇 程乐利 牟连刚 吴雪松 杨朋 邵崇建 袁雪花

成都理工大学地球科学学院，四川 成都 610059 成都理工大学地质学博士后科研流动站，四川 成都 610059 长江大学录井技术与工程
研究院，湖北 荆州 434023 中国石油大港油田分公司，天津 300280 东华理工大学核资源与环境国家重点实验室，江西 南昌 330013

College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China Geology Postdoctoral Research Stations, Chengdu University of Technology, Chengdu 610059, China Institute of Mud Logging Technology and Engineering, Yangtze University, Jingzhou 434023, China Dagang Oilfield Company, PetroChina, Tianjin 300280, China State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China

渤海湾盆地沧东凹陷古近系沙河街组三段烃源岩具有良好的生烃潜力，文中利用薄片、地球化学等资料，分析沙三段烃源岩特征及沉积环境，讨论烃源岩有机质富集机制和沉积环境对未熟—低熟烃源岩生烃的控制作用。结果表明：沙三段烃源岩岩性主要为灰质黏土岩、含灰黏土岩，具有较高的有机质丰度，主要为Ⅰ与Ⅱ2型有机质，含少量Ⅲ型有机质，处于未熟—低熟阶段；沧东凹陷在沙三期为半咸水—咸水环境，海侵可能是湖水咸化的原因，烃源岩沉积在缺氧还原环境之中；海侵导致的咸化水体环境可以提高湖泊生产力并促使缺氧环境形成，促进烃源岩中有机质的富集；咸化湖泊环境会促进未熟—低熟烃源岩早期生烃。该结果可为沙河街组油气勘探提供重要参考。

The source rocks in the third member of the Paleogene Shahejie Formation (Es3) in Cangdong Depression, Bohai Bay Basin have good hydrocarbon generation potential. Based on thin section, geochemical data, the characteristics of the Es3 source rocks and its depositional environment are analyzed, and the mechanism of organic matter enrichment in source rocks and controlling effect of depositional environment on hydrocarbon generation of immature to low mature source rocks are discussed. The results show that the Es3 source rocks are mainly calcareous clay rocks and calcium-bearing clay rocks, with high organic matter abundence. The organic matter is mainly type ⅠandⅡ2 , with a small amount of type Ⅲ, which is in immature to low mature stage. The Cangdong Depression was a brackish to salt water environment during Es3 period, which may be caused by marine transgression. The Es3 source rocks were deposited in an anoxic reduction environment. The saline water environment caused by marine transgression can improve lake productivity and promote the formation of anoxic environment, and then promote the enrichment of organic matter in source rocks. The saline lake environment can promote the early hydrocarbon generation of immature to low mature source rocks. The results can provide important reference for oil and gas exploration of the Shahejie Formation .

10.6056/dkyqt202205009