Sedimentary Facies Characteristics And The Sandstone Distribution Of Chang 9 Oil Reservoir In Jiyuan Area, Ordos

Jiyuan area is located in the northwest of Ordos basin, it spans Tianhuan depression and Shanbei slope in regional tectonic structure. Yanchang formation was divided into 10 oil layers from its bottom to its top. Chang 9 oil layer was deposited in the early period of Yanchang, and it experienced the initial depression and long-period subsidence of the ancient lake.Guided by the modern sedimentary geology and petroleum geology, based on the collection, comprehensive analysis and summary to the previous results of the study area, through the field survey, core observation, the analysis of logging data and test data, and seismic facies analysis and sandstone thickness prediction of Chang 9 reservoir, this paper elaborated the types and characteristic of the sedimentary facies of Chang 9 reservoir, and described the sandstone distribution in chang 91 and chang92 sedimentary period.The study results show that it developed braided-delta plain subfacies, which was divided into distributary channel and interdistributary area mainly in Jiyuan area. There were also other microfacies found in Jiyuan such as natural levee, crevasse, mash and flood plain. There mainly is sandstone in braided distributary channel, and clay in interdistributary area. Affected by paleocurrent and provenance, sedimentary facies in Jiyuan significantly shows differently in northwest and northeast, resulting in the sandstone extension which is mainly in two direction, NW-SE(Lingwu- Yanchi area) and NE-SW(Anbian area). The sandstone distribution in surface during Chang 91 is similar with Chang 92 sedimentary period. But the main sandstone zones in Chang 91 and Chang 92 are different in size, and the scale of interdistributary area in different period is different either.