Under the control of Yidong fault zone, many kinds of oil reservoirs are formed in the north of Sikou sag. Meanwhile, because of the significant tectonic differences exist between the north and the south structures of Yidong fault zone, the reservoir-forming patterns are quite different. Therefore, studying reservoir-forming conditions and patterns has the important significance for further hydrocarbon exploration. Based on the data of core, well logging, well drilling, and seismic analyses, the reservoir-forming conditions and patterns of Yidong fault zone are discussed. The results show that due to abundant source rocks, good reservoir-cap assemblage, and sealing property, the reservoir-forming conditions are quite superior, and many lithologic reservoirs and structural lithologic reservoirs are formed, that have the pattern feature of "turbidite fan" and distribute along the faulted zone. The feature of the fourth member of Shahejie Formation (Es₄) are that the reef limestone lithologic reservoirs are developed upon the south fault terrace, and clastic structural lithologic reservoirs are formed in the north part. In the third member of Shahejie Formation (Es₃), some small nearshore subaqueous fan, turbidite fan structural lithologic reservoirs, and turbidite channel lithologic reservoirs are developed. Nevertheless, fan delta and sandy beach bar structural lithologic reservoirs are mainly developed in the second member of Shahejie Formation (Es₂).