鄂尔多斯盆地庆城油田延长组页岩层系层序地层与沉积相特征OA北大核心CSTPCD

The shale succession of Yanchang Formation in Ordos Basin is rich in hydrocarbon re-sources,but its sequence framework and sedimentary facies distribution are controversial,which affects the exploration and development of shale hydrocarbon.Taking the Xi233 area of Qingcheng Oilfield as an example,this paper reconstructs the sequence stratigraphic framework and sedimentary facies distribution using core,logging,and the latest 3D seismic data.Research has shown that in the original Chang 81-Chang 32 interval of the Yanchang Formation,the strata represent a progradational superposition pattern towards the center of the lake basin,which can be divided into two long-term base-level cycles and ten mid-term base level cycles.In each mid-term cycle,the paleogeomorphology towards the basin is followed by shallow-water area,slope area and basin floor area.The shallow-water area mainly develops deltas.The slope belt develops gravity flow channels,which are distributed in narrow bands along the slope;the gra-vity flow lobe deposits are developed in the proximal basin floor,and the sand bodies are sandwiched in mud shale.The distal basin floor is mainly deep-lake shale interbedded with slump deposits.The original"Chang 7 interval"shale strata is a set of diachronous strata,which is composed of sublacustrine fan sand bodies and semi-deep to deep lake shale in the lower part of the slope belt and basin floor belt of multiple mid-cycles.This study not only plays an important guiding role in the effective development of interbedded shale oil in the Ordos Basin(optimization of development areas and deployment of horizontal wells),but also promotes the development of the theory of sequence and sedimentary evolution in depression lake ba-sins.