渤海湾盆地沾化凹陷湖相泥页岩地球化学特征及有机质富集规律

Geochemical characteristics of lacustrine shale and enrichment mechanism of organic matter in Zhanhua Sag,Bohai Bay Basin

以渤海湾盆地沾化凹陷罗69井沙三下亚段湖相泥页岩为研究对象,在层序地层框架下,研究了不同体系域湖相泥页岩的地球化学特征,阐明了沉积环境的演化过程及有机质富集规律,为非常规页岩油有利目标的识别提供理论支持。测井与岩性组合揭示沙三下亚段层序自下而上分为湖侵体系域、早期高位体系域和晚期高位体系域。生产力和保存条件是有机质富集的控制因素,二者缺一不可。较高的生产力和较好的保存条件共同决定了早期高位体系域最有利于有机质富集,也为其成为良好的页岩油开发层系提供了良好的物质基础。

The lacustrine shale in the lower part of the third member of Shahejie Formation(Es3)in well L69 in the Zhanhua Sag of Bohai Bay Basin was studied.The geochemical characteristics of lacustrine shale in different system tracts were analyzed in a framework of sequence stratigraphy.The evolution process of sedimentary environment and the enrichment mechanism of organic matter were clarified,which provided theoretical support for the identification of favorable targets of unconventional shale oil.The combination of logging and lithology reveals that the sequence of the lower Es3 can be divided into transgression,early highstand and late highstand system tracts from bottom to top.Productivity and preservation conditions are the controlling factors of organic matter enrichment.The higher productivity and better preservation conditions together determine that the early highstand system tract is the most favorable organic matter accumulation interval,which provides a good material basis for a good shale oil development target.