渤中凹陷西次洼浅层晚期快速充注成藏模式

渤中凹陷西次洼新近系油气资源丰富,成藏主控因素及成藏机理研究有待深入。通过烃源岩成熟度模拟、原油地球化学及油源关系分析、流体包裹体分布特征及均一温度测定,结合断层的封闭性能及疏导体系等成藏要素的综合分析,结果表明:渤中西次洼存在沙三、沙一-沙二与东三段3套烃源岩,其中沙三段为优质烃源岩,成熟度高;该区原油成熟度普较高,为烃源岩在生油高峰及后期生成的原油,主要与沙三段烃源岩相关;渤中8区新近系储层砂岩孔隙烃与油气包裹体发蓝白色荧光,油气包裹体丰度(GOI)普遍较低,主要为一期包裹体,均一温度表明油气主要充注期为3.5 Ma B.P.、1.0 Ma B.P.以后,为晚期快速充注成藏。在新构造运动活动期,持续快速生烃、供烃能力强的烃源灶、高效的断裂输导格架,为晚期快速成藏的主控因素;"高效供烃、主断控藏、浅层聚集"为该区油气成藏模式。

Preliminary discussion on late stage rapid petroleum accumulation pattern in the western subsag of Bozhong depression,Bohai Bay,China

Through the studies of maturity simulation of hydrocarbon source rock,analysis of oil geochemistry and oil source relations,distribution characteristics of fluid inclusions and measurement of its homogenization temperatures by fluid inclusions,combined with comprehensive analysis of accumulation elements,such as fault closure and pathway systems,the controlling factors of hydrocarbon accumulation and its accumulation mechanism for Neogene reservoir in the western subsag of Bozhong depression in Bohai Bay are discussed.It reveals that there exist three sets of hydrocarbon source rocks,they are the 1st Member and 3rd Member of the Shahejie Formation and the 3rd Member of the Dongying Formation,and the 3rd Member of Shahejie Formation is high quality and high maturity.The oil maturity of hydrocarbon source rock in the area is generally high,and the crude oil is formed in the generation peak period and later period,mainly related to the 3rd Member of Shahejie Formation.The study shows that the hydrocarbon in the pores of sand reservoir as well as petroleum inclusions in the No.8 area of Bozhong display blue-white fluorescence color,with lower oil and gas inclusions abundance (GOI).These inclusions are mainly formed in one phase and the homogenization temperatures show that they occur after the time of 3.5 Ma B.P.or 1.0 Ma B.P.,indicating that the oil and gas filled and accumulated in the later period.It is considered that the main factors controlling the reservoir formation are rapid and continues generation of hydrocarbon,abundant supply of hydrocarbon source,effective fault transport system.Therefore,a reservoir forming model of highly active supply of hydrocarbon,fault controlled reservoir generation and superficial accumulation is proposed.