Abstract: Based on the core, logging, lab testing and seismic data, by means of theory of sedimentology and reservoir geology, four sedimentary facies are classified in the upper part of fourth member of Shahejie formation in Bonan sag as fan delta facies, near?shore subaqueous fan facies, beach bar facies and lake facies, their distributions of each system tract are discussed, and eight favorable reservoir bodies are ascertained, such as sandstone beach bar in Luojia nose?like structural belt, fan delta front in the ramp belt, reef in Yidong fault belt, sandy limestone beach bar in the ramp belt, limestone beach bar in the ramp belt, fan delta front in the steep slope belt, fan delta plain in the ramp belt and fan prodelta in the ramp belt. Based on these, four favorable areas are predicted, they are the fan delta front area in the steep slope belt, the reef area in Yidong fault belt, the sandstone beach bar area in Luojia nose?like structrual belt, and the mixing areas of fan delta-limestone beach bar-sandy limestone beach bar in the ramp belt