Significant progress in oil-gas exploitation has been made in the Nanpu depression of the Bohai Bay Basin, China. Discovery of the Nanpu oil field has made the Nanpu depression one of the most oil-rich depressions in the basin. Voluminous sampling and analysis display that the Shahejie Fm (Es) of Paleogene, especially the third member of Shahejie Formation (Es3x) has developed excellent source rocks with TOC up to 5％, a thickness of effective source beds about 250m and vitrinite reflectance (Ro) of above 0.8％. The amorphous body and phycoplast is the important source of organic material in source beds and of great potential for hydrocarbon generation. The studies suggest that ① the Nanpu depression is oil-rich depression and has good conditions for hydrocarbon accumulation; ② the development of premium oil source rocks in the Shahejie Formation (Es) is the material base for hydrocarbon accumulation; ③ Neotectonic movement led to the development of faultage in main depression, in favor of conduction effectively; ④ shallow fan dalta and fluvial facies depositional system, thickly and wide distributed sand layer and good physical property is beneficial to large-area accumulation; ⑤ one suite of thick and widely distributed basalt, developed over the premium sandstone reservoir of Guantao Formation, constitutes high-quality caprock. All the features mentioned above are important factors for rich accumulation of oil and gas in the Nanpu depression.%渤海湾盆地南堡凹陷近年来油气勘探取得重大突破,发现了南堡大油田,南堡凹陷成为渤海湾盆地油气富集程度最高的富油凹陷之一.通过大量的采样分析工作,发现了南堡凹陷古近系沙河街组特别是沙三4亚段发育高丰度的优质烃源岩,TOC高达5%以上,有效烃源岩厚度在250m左右;镜质体反射率(Ro)在0.8%以上,无定形体和藻质体是烃源岩中有机质的重要来源,该烃源岩具有巨大的生烃潜力.研究认为,南堡凹陷属于富油凹陷,油气成藏条件优越:沙河街组沙三段优质烃源岩的发育是油气藏形成的物质基础;新构造运动导致主洼区油源断层发育,利于高效输导;浅层扇三角洲与河流相沉积体系发育,砂层厚度大、分布广,储集物性好,利于大面积成藏;馆陶组发育一套厚度大、分布广的玄武岩,构成了优质盖层,这些因素是造就南堡凹陷油气异常富集的重要条件.另外,该区油气成藏要素匹配较好,成藏时间较晚;成藏要素空间上有效组合,明化镇组-馆陶组浅层组合、沙河街组和东营组中层组合、奥陶系古潜山深层组合等三套含油层系在垂向上相互叠置,复式聚集,决定了南堡凹陷成为渤海湾盆地的富油凹陷.
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