北黄海东部次盆地层序地层格架中烃源岩发育特征与影响因素

北黄海东部次盆地是我国海域勘探程度较低的一个盆地，钻探已发现该盆地发育中、上侏罗统巨厚暗色泥岩，但目前对该盆地烃源岩的研究尚较薄弱，精细评价该盆地的烃源岩对后续勘探部署具有重要意义。本文利用多口钻井实测数据和地震、测井资料，在层序地层学研究的基础上，应用有机地球化学和有机岩石学等方法，对中、上侏罗统不同层序和同一层序不同体系域中的烃源岩特征进行综合研究，并探讨烃源岩的分布规律及影响因素。东部次盆地烃源岩非均质性特征明显：中侏罗统J₂SQ1和J₂SQ2层序均以半深湖-深湖相、滨浅湖相暗色泥岩为主，烃源岩有机碳质量分数总体较高（w（TOC）>1.0%），但生烃潜力指数（w（S₁+S₂））和氢指数（I_H）均很低，且有机质类型差，表明研究区有机质丰度高的烃源岩并非都是生烃能力高的烃源岩，整体为中等-差烃源岩。上侏罗统J₃SQ1层序中的烃源岩主要为三角洲前缘和滨浅湖相泥岩，有机质丰度较低，不同体系域发育的均是中等-差烃源岩；J₃SQ2层序主要为半深湖-深湖相暗色泥岩，具有厚度大、质纯和横向分布广的特点，但不同体系域中烃源岩的w（TOC）变化很大（0.5%~5.3%），其中优质烃源岩主要发育在J₃SQ2层序中的高位体系域和湖侵体系域中，厚度0~104 m，而低位体系域中发育的则是中等烃源岩，该套优质烃源岩是东部次盆地内最主要的一套油源岩。研究认为，层序地层格架和沉积相控制了东部次盆地烃源岩的空间展布范围，陆源有机质的输入与湖盆原位生物生产力的匹配关系控制了烃源岩的质量，湖盆水体的含氧量与盐度在一定程度上控制了有机质的保存。综上所述，北黄海东部次盆地属于中低丰度的含油气盆地，应在优质烃源岩发育区及其邻区寻找有利勘探目标。

Development and Influencing Factors of Source Rock in Sequential Stratigraphic Framework in the Eastern Sub-Basin,North Yellow Sea

The eastern sub-basin of the North Yellow Sea is an area with low degree of exploration, in which the Middle and Upper Jurassic dark mudstone is the main source rocks. The detailed evaluation of source rocks is very important for further exploration. Based on the sequence stratigraphy, by use the methods of organic geochemistry and organic petrology, the integrated study was conducted for the geochemical characteristics of the Jurassic source rocks in different sequences and different system tracts of the same sequence, and then the distribution law and main influencing factors of source rocks were discussed. The Middle and Upper Jurassic source rocks have high heterogeneity in the eastern sub-basin. The lithology of the source rocks is mainly dark mudstones of semi-deep lacustrine, deep lacustrine, and shore-shallow lacustrine in J₂SQ1 and J₂SQ2. Though these source rocks have high w(TOC), low w(S₁+S₂) and I_H,and the type of organic matter is poor, so these source rocks don't have high hydrocarbon generation potential in this basin. In general, the quality of the Middle Jurassic source rocks is medium to poor. The lithology of source rocks is mainly dark mudstones of delta front and shore-shallow lacustrine in J₃SQ1. The source rocks of J₃SQ1 have low w(TOC), and all of them are poor source rocks in different system tracts. The lithology of source rocks is mainly dark mudstone of semi-deep lacustrine, deep lacustrine in J₃SQ2, which is characterized by large thickness, high purity, and wide horizontal distribution. The w(TOC) of source rocks ranges from 0.5% to 5.3% in various system tracts of J₃SQ2. The high-quality source rocks are mainly developed in the high stand system tracts and extent system tracts, which are the most important oil source rocks in the eastern sub-basin. The studies indicate that the range of distribution is controlled by the sequential stratigraphic framework and the sedimentary facies. The quality of source rocks is controlled by the terrestrial matter input and the primary organic matter production of the lake basin. The preservation of organic matter is controlled by the oxygen content and salinity of lake water to a certain degree. In conclusion, the eastern sub-basin of the North Yellow Sea is an oil and gas bearing basin with medium-low abundance. The favorable exploration targets should be found in the high-quality hydrocarbon source rocks.