Sedimentary Characteristics Of Es₂ Member Of The Shahejie Formation In The Shicun Fault Footwall Of The Southern Slope Of Dongying Sag And Reservoir Quality Evaluation

In this paper,taking Es₂ member of the Shahejie Formation in the Shicun Fault Footwall in the Southern Slope of Dongying sag as the research object.Based of core,borehole log,logging and seismic data,well-to-seismic integration completed fine strata classification and correlation,then the sedimentary characteristics of the study area are studied in detail,and then employing fuzzy comprehensive evaluation method,favorable sand bodies in the study area is evaluated and predicted.Es₂ member of Shahejie Formation in the Shicun Fault Footwall of the Southern Slope of Dongying sag is divided into 3 sand groups,including 1^st sand group,2^nd sand group and 3^rdd sand group.The 1^st Sand group in Es₂ member is divided into 3 small groups,and The 3^rdd Sand group in the second member is divided into 4 small layers.Because of 2^nd Sand group in the second member in the study area is relatively thin,it is not divided further the 2^nd Sand group in Es₂ member of Shahejie Formation.3 types of sedimentary facies were identified,including delta,braided river delta and lacustrine facies,and eveutally sedimentary facies model was established.The braided river delta are mainly distributed in the eastern part of the study areat,and the sediment source mainly comes from the Gangrao salient,It is characterized by developing braided river delta front subfacies,which was further divided into channel microfacies,underwater distributary bar microfacies,mouth bar microfacies,and sheet sand microfacies.The delta are mainly distributed in the Central-southwest of the study area,and the sediment source mainly comes from the Luxi uplift area,developing the delta front subfacies,which which was further divided into sedimentary micro-facies below,including underwater distributary channel microfacies,underwater distributary bar microfacies,mouth bar microfacies,and sheet sand microfacies.The lacustrine facies is mainly distributed in the northern part of the study area,including lakeshore-shallow lake subfacies and beach bar subfacies.Tthe beach bar subfacies can be further divided into sandy beach and sand bar microfacies.The N-S trending sections show that from 3^rd sand group to 1^st sand group of Es₂ member,bottom sedimentary is mainly composed of lacustrine sediments,up to the braided river delta front facies.The southern stratum is relatively thin,and the northern stratum is relatively thick.The 3^rd sand group of the second member is characterized by lacustrine sedimentation in E-W trending section,with upwardly eastern area and western area being dominated by braided delta front and delta front,respectively.In this paper,beased on fuzzy comprehensive evaluation method,combined with sandstone thickness,sandstone percentage and ervoir physical parameter,favorable sandstone was evaluated.The evaluation results indicated that 3^rd small layer of 1^st sand group in second member,1^st small layers of 3^rd sand group in the second member and 3^rd small layer of 1^stt sand group in Es₂ member are rhe most favorable reservoir.1^st small layer of 1^st sand group in Es₂ membero and 3^rd small layer of 3^rd sand group in Es₂ member are relatively poor.