In an oil-and-gas bearing basin, release of pore fluid from source rocks caused by diagenesis generally affect remarkably the diagenesis of sandstones. This paper investigates the characteristics of diagenetic minerals in source rocks of the Upper Unit of the Fourth Member and the Lower Unit of the Third Member of the Shahejie Formation, and the sandstones of the Lower Unit of the Third Member of the Shahejie Formation in the Niuzhuang Sub-sag. In the sandstones sampled from the wells near to south of Niul8-Niu20 Fault, cements mainly are ferrodolomite, chlorite and chlorite/smectite, bearing high contents of Ca, Mg, Fe, and Sr. It is suggested that diagenetic fluids are enriched by Ca, Mg, and Fe, which is apparently similar to the pore fluid from the source rock of the Upper Unit of the Fourth Member of the Shahejie Formation. Thus, it is deduced that the oils in these sandstones should be migrated from the Upper Unit of the Fourth Member of the Shahejie Formation. Whereas, in the sandstones from the north of Niul8-Niu20 Fault, secondary cements are ferroan calcite and only a few chlorite/smectite. This suggests that the influence of the fluids derived from the Upper Unit of the Fourth Member of the Shahejie Formation get weak while the contribution from the Lower Unit of the Third Member of the Shahejie Formation is dominatedly. As ferrodolomite and chlorite can be found in a few sandstone samples, it is considered that the oil in this area may be sourced from the Lower Unit of the Third Member of the Shahejie Formation with a few mixture from the Upper Unit of the Fourth Member of the Shahejie Formation.%在含油气盆地中,烃源岩在成岩演化过程中排出的孔隙流体对砂岩储层的成岩作用有着重要的影响.本文对牛庄洼陷沙四上烃源岩、沙三下烃源岩及沙三段砂岩中成岩特征进行了分析研究.在牛18-牛20断层附近及其南侧井位中,砂岩胶结物以铁白云石、绿泥石和绿/蒙混层矿物为主,含有较高含量的Ca、Mg、Fe、Sr等元素,说明该成岩期的孔隙流体中富含Ca、Mg、Fe等元素,且盐度较高,这与沙四上烃源岩排出的孔隙流体具有明显的相似性,推测其成岩流体可能主要来自沙四上烃源岩.而在牛18-牛20断层北侧,砂岩胶结物以含铁方解石为主,绿泥石和绿/蒙混层矿物仅少量存在,可见沙四上烃源岩的影响有所减弱,而沙三下烃源岩的贡献明显增加,可以认为其成岩流体为沙四上和沙三下烃源岩的混源.
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