层序地层格架中优质烃源岩分布与控制因素——以歧口凹陷古近系为例

Distribution and Controlling Factors of High-quality Hydrocarbon Source Rock in Sequential Stratigraphic Framework——Taking Paleogene System in Qikou Depression for Instance

在层序地层学研究的基础上,应用有机地球化学等手段开展歧口凹陷古近系层序地层格架中烃源岩成烃环境研究,探讨优质烃源岩分布规律及主控因素。歧口凹陷古近系可以划分为3个二级层序,不同层序地层中均发育多套有效烃源岩,但烃源岩非均质性强。根据古环境、古生态、古气候等方面的差异性将不同层序划分为6种沉积有机相类型,其中近源—咸化湖—强还原—植源藻源相优质烃源岩最为发育。纵向上,优质烃源岩主要发育于断陷湖盆稳定湖泛期,尤其是SQEs32上部—SQEs31、SQEs1下上部—SQEs1中;横向上受物源条件和水体环境的控制,优质烃源岩在歧口凹陷南部较为发育;沉积环境和成烃环境共同控制优质烃源岩空间发育。

Based on the sequential stratigraphic research, this paper is focused on the environment for hydrocarbon source rock of the Paleogene System in the sequential stratigraphic framework of Qikou Depression by means of organic geochemistry, studying the distribution law and controlling factors of high-quality source rock. The Paleogene System in Qikou Depression can be divided into three secondary sequences. A number of sets of effective source rock developed in the strata of different sequences, but source rock is strongly heterogeneous. The different sequences are divided into six types of sedimentary organic facies according to the differences in the palaeoenvironment, palaeoecology and palaeoclimate. Of those types, the high-quality source rock of near source- saline lake- strong reduction atmosphere- plant and algal source facies developed most. Vertically, high-quality source rock developed mainly in the faulted lacustrine basin in the stable lake fl ooding period, particularly in the upper part of SQEs32- SQEs31, the upper part of SQEs1 lower- SQEs1 middle. Horizontally, high-quality source rock development mainly in the southern part of Qikou Depression because it was controlled by the conditions of material sources and the environment of water bodies. The sedimentary and sourcing environments controlled space development of highquality source rock in common.