Study on the sedimentary facies of the member 3 and 4+5 of Yanchang Formation in Jiyuan area

Jiyuan area,in southern Ordos Basin,is located at the structure unit between Shanbei Slope and Tianhuan Depression.The exploratory degree is low here,thus,the study on depositional system,sedimentary facies,reservoir distribution,traps accumulation,and the hydrocarbon enrichment of the member 3 and 4+5 of Yanchang Formation is not enough.Based on the outcrop,core and well log data,the lithologic characteristics,well log form and sedimentary microfacies are analyzed.The result shows that the member 3 and 4+5 are mainly composed of delta and lacustrine depositional systems,which can be further divided into two subfacies and five microfacies.According to the distribution and evolution rule of the sedimentary microfacies,the depositional model of the study area can be obtained.