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 Niu18—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 Niu18—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.