威利斯顿盆地巴肯组泥页岩排烃效率地质研究

为了弄清造成威利斯顿盆地巴肯组泥页岩相对含油量低,而致密砂(灰)岩中含油量高的原因,对巴肯组泥页岩的排烃特征进行研究具有重要的意义。本文在油气勘探相关资料的分析基础上,结合薄片鉴定和地球化学分析方法,探讨了巴肯组泥页岩的排烃特征。结果表明,巴肯组泥页岩的高排烃效率是造成巴肯组中段致密层段相对含油量高、而泥页岩相对含油量较低的根本原因。巴肯组泥页岩产率指数与其有机碳含量的明显不匹配,可溶有机质族组成的低饱/芳值以及巴肯组中段粉砂质白云岩强荧光性都说明巴肯组泥页岩发生过大量的排烃。泥页岩的生烃增压引起的超压诱导泥页岩产生的微裂缝与干酪根网络构成了石油初次运移的通道,也利于泥页岩排烃。

Geological research on hydrocarbon expulsion efficiency of shale in Bakken Formation in the Williston Basin

To find out the cause of relatively low oil content of the shale and high oil content in dense zone in bakken formation in the Williston basin, is of great significance in order to reveal the characteristics of hydrocarbon expulsion of shale in bakken formation. Through the detailed analysis of basic geological data of petroleum exploration, combined the methods of thin section and geochemistry, the characteristics of hydrocarbon expulsion of shale in bakken formation is discussed. The results are showed as below: high hydrocarbon expulsion efficiency of shale is the root cause of relatively high oil content in the middle dense zone and low oil content of shale. The dismatches between production rate index and organic carbon content, the low ratio of saturated hydrocarbon and aromatic hydrocarbon of soluble organic matter, as well as strong fluorescence of silty dolomite in the middle bakken group, suggest that the shale in bakken formation have happened a lot of hydrocarbon expulsion. Microfracture and kerogen network inducted by overpressure caused by hydrocarbon-generating pressurization of shale constitutes the channel of the oil primary migration, and is also conducive to hydrocarbon expulsion of the shale.