黄河口凹陷烃源岩特征及其在层序地层格架中的分布

Characteristics of hydrocarbon source rock in Huanghekou sag and its distribution in sequence stratigraphic framework

基于钻井和实测资料对研究区进行有机地化和沉积学分析,总结典型富生烃凹陷黄河口凹陷3套湖相烃源岩的特征及沉积背景,以此为基础进行层序研究,探讨黄河口凹陷古近系湖相烃源岩有机质丰度评价指标随沉积旋回的演变和层序构型的不同所表现出来的变化趋势,预测优质烃源岩在层序地层格架中的分布规律。结果表明,沙三及沙一段均为好烃源岩,东二下—东三段为中—好的烃源岩,3套烃源岩有机质类型均以Ⅱ型为主;沙一段烃源岩发育于咸化水体的浅湖环境,东二下—东三段和沙三段烃源岩发育于淡水—微咸水中稳定的浅湖—深湖相沉积;地层中泥岩质量含量达60%以上时,烃源岩具较高的有机质丰度;优质烃源岩主要发育在以基准面上升半旋回为主的层序类型中,基准面上升和下降半旋回相当的层序类型中次之,在以基准面下降半旋回为主的层序类型中最次,且几种层序类型中的有机质丰度高值均出现在最大湖泛面附近。

According to the analysis of organic geochemistry and sedimentology based on the well and test data,the characteristics and depositional setting of three sets of Paleogene lacustrine source rocks in Huanghekou sag are comprehensively analyzed.On this basis,study on sequence stratigraphy is carried,varied trends of assessment indices of organic matter abundance according to evalution of dimentary cycle and sequence framework and the distribution of source rocks in the Eogene sequence stratigraphic framework of Huanghekou sag are discussed.The results show that source rocks which lie in Shahejie 3 Member and Shahejie1 Member are both in good level,and the source rocks of lower Dongying 2 and Dongying 3 Member are in a medium to good level.Three sets of source rocks are all in aⅡtype of organic matter.Source rocks of Shahejie1 Member developed in a saline water environment in stable shallow lacustrine,source rocks of Shahejie1 Member and lower Dongying 2 and Dongying 3 Member developed in a fresh to brackish water environment in stable shallow to deep lacustrine.There are good source rocks when content of mudstone is above 60%.The good source rocks are mainly formed in the sequence type which are mainly made up of base level rising half cycle,and the high value of organic matter abundance appear near maximum flood surface.