火山断陷型湖盆细粒沉积岩有机质富集模式——以松辽盆地梨树断陷下白垩统沙河子组二段下亚段为例  

Organic matter enrichment model of fine-grained rocks in volcanic rift lacustrine basin:A case study of lower submember of second member of Lower Cretaceous Shahezi Formation in Lishu rift depression of Songliao Basin,NE China

作　　者：谢环羽 姜在兴[1] 王力 薛欣宇 XIE Huanyu;JIANG Zaixing;WANG Li;XUE Xinyu(School of Energy Resources,China University of Geosciences,Beijing 100083,China;China National Offshore Oil Limited Corporation-Zhanjiang,Zhanjiang 524057,China;School of Marine Sciences,Sun Yat-sen University,Zhuhai 519082,China)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]中海石油(中国)有限公司湛江分公司,广东湛江524057 [3]中山大学海洋科学学院,广东珠海519082

出　　处：《石油勘探与开发》2024年第5期1067-1079,1091,共14页Petroleum Exploration and Development

基　　金：国家科技重大专项(2017ZX05009-002);国家自然科学基金面上项目(41772090)。

摘　　要：以松辽盆地梨树断陷下白垩统沙河子组二段下亚段(简称沙二下亚段)沉积特征为例,采用有机岩石学、主微量元素及生物标志化合物分析等方法,探讨火山断陷型湖盆细粒沉积岩有机质富集条件及富集模式。研究结果表明,沉积古环境的变化控制沙二下亚段不同岩相类型的垂向分布,并将其划分为上、下两部分,下部主要发育块状长英质泥岩夹含生屑长英质泥岩,上部主要发育纹层状长英质页岩和纹层状细粒混积页岩;下部有机质干酪根类型以Ⅱ2—Ⅲ型为主、上部以Ⅰ—Ⅱ1型为主,且总体呈现出上部有机碳含量较下部增高的特征。分析认为,火山断陷型湖盆有机质富集的主要条件为:①持续增强的裂陷作用是导致古水深加大的直接因素,基准面上升使深水沉积范围随之扩大,泥页岩发育规模相应增大;②相对强烈的水下火山喷发与裂陷作用具有同时性,火山活动可为湖盆提供大量营养物质,有利于藻类的勃发,并导致Ⅰ—Ⅱ1型干酪根生产力较高;③相对干旱的古气候导致河流淡水及陆源物质(包括陆源高等植物Ⅲ型干酪根)输入减少,形成高盐度、缺氧分层的水体,咸水湖盆有利于有机质保存。在此基础上,建立的火山断陷型湖盆细粒沉积岩有机质富集模式,对深化松辽盆地沙河子组乃至中国东北地区同期火山断陷型湖盆细粒沉积岩有机质富集机制的地质认识,具有一定的参考借鉴意义。Based on sedimentary characteristics of the fine-grained rocks of the lower submember of second member of the Lower Cretaceous Shahezi Formation(K1sh2 L)in the Lishu rift depression,combined with methods of organic petrology,analysis of major and trace elements as well as biological marker compound,the enrichment conditions and enrichment model of organic matter in the fine-grained sedimentary rocks in volcanic rift lacustrine basin are investigated.The change of sedimentary paleoenvironment controls the vertical distribution of different lithofacies types in the K1sh2 L and divides it into the upper and lower parts.The lower part contains massive siliceous mudstone with bioclast-bearing siliceous mudstone,whereas the upper part is mostly composed of laminated siliceous shale and laminated fine-grained mixed shale.The kerogen types of organic matter in the lower and upper parts are types II2–III and types I–II1,respectively.The organic carbon content in the upper part is higher than that in the lower part generally.The enrichment of organic matter in volcanic rift lacustrine basin is subjected to three favorable conditions.First,continuous enhancement of rifting is the direct factor increasing the paleo-water depth,and the rise of base level leads to the expansion of deep-water mudstone/shale deposition range.Second,relatively strong underwater volcanic eruption and rifting are simultaneous,and such event can provide a lot of nutrients for the lake basin,which is conducive to the bloom of algae,resulting in higher productivity of types I–II1 kerogen.Third,the relatively dry paleoclimate leads to a decrease in input of fresh water and terrestrial materials,including Type III kerogen from terrestrial higher plants,resulting in a water body with higher salinity and anoxic stratification,which is more favorable for preservation of organic matter.The organic matter enrichment model of fine-grained sedimentary rocks of volcanic rift lacustrine basin is established,which is of reference significance to the underst

关 键 词：细粒沉积岩 有机质来源 裂陷作用 火山活动 下白垩统沙河子组 梨树断陷 松辽盆地 

分 类 号：TE121[石油与天然气工程—油气勘探]