北黄海盆地东部坳陷中生界烃源岩特征

摘要

The Eastern Depression is the biggest depocenter in North Yellow Sea basin,and the study on its petroleum geology is still in a stage of early exploration.The distribution,geochemistry and thermal evolution were primarily analyzed for the hydrocarbon source rocks in the depression,indicating that:(1) There are two sets of main source rocks in the depression,i.e.Mesozoic Middle Jurassic and Upper Jurassic,and the organic matter in the former is mainly from terrigenous higher plants and predominated by Type Ⅲ kerogen,with its organic carbon content in middle and HI below 200mg/gTOC; (2) The organic matter in the Upper Jurassic source rock is a mixture of terrigenous higher plants and aquatic lower organisms and characterized by the coexistence of Type Ⅱ and Ⅲ kerogen,forming some local excellent sourcerock intervals with high organic carbon and average HI of 500mg/gTOC; (3) These two sets of source rocks have been into the threshold of hydrocarbon generation and are capable of generating some oil and gas in the main part of the depression,showing a good potential of petroleum exploration.%东部坳陷是北黄海盆地内最大的一个沉积坳陷,目前对该区的油气地质条件研究尚处于勘探早期.对该区烃源岩分布、地球化学特征和热演化特征作了初步分析,结果表明:东部坳陷内主要发育2套烃源岩,即中生界中、上侏罗统烃源岩；中侏罗统烃源岩母质以陆源高等植物为主,主要为Ⅲ型干酪根,有机碳含量中等,氢指数多在200 mg/gTOC以下；上侏罗统烃源岩母质为高等植物和低等水生生物混杂,兼有Ⅱ型和Ⅲ型干酪根,局部发育有机碳含量高、氢指数平均为500mg/gTOC的良好烃源岩；东部坳陷主体部位的2套烃源岩现今均已进入生烃门限,具备一定的生油气潜力,具有良好的油气勘探前景.