Study On High-resolution Sequence Stratigraphy And Sedimentary Facies Of He8 Sectionin Zhao 30 Wellblock,Sulige Gas Field Of Ordos Basin

The Zhao 30 wellblock is situated in the eastern Sulige Gas Field enriched with natural gas resources in the Ordos Basin. The gas reservoirs in the He8 Section of Zhao 30 wellblock are typical lithological reservoirs. The distribution of gas reservoir is mainly controlled by the spreading of sand bodies and the variation of reservoir physical property, which also are characteristics by complicated distributing of sandbodies' plane, low porosity, low permeability, low abundance, severe heterogeneity. Based on the research of predecessors,this paper study on the sequence stratigraphy and sedimentary facies characteristics of He8 Section in Zhao 30 wellblock,with the using of the theory and technology of high-resolution sequence stratigraphy and the comprehensive research methods of sedimentary facies. So it can provide a basic on the further study of favorable reservoir, and to lay a foundation of higher precision requirements in the exploration and development of gas reservoirs.The leading conclusions are as follows:Based on the comprehensive analysis of logging and cores,4 types of sequence boundaries and the(maximum) flooding surfaces have been recognized. According to correlation of the longitudinal and transverse section,2 long-term(LSC1~LSC2), 4middle-term(MSC1~MSC4), 12 short-term(SSC1~SSC12) cycle sequences can be distinguished from the He8 section. The structure types and distribution mode of long-term, middle-term and short-term cycle sequences have been analyzed and described.According to the principle of high-resolution sequence stratigraphic correlation,we choose the sequence boundary and flooding surface of long-term cycle sequence as the optimum position of isochronous stratigraphic correlation,and the middle-term cycle sequence as the correlation unit, and then, establish the chrono-stratigraphic frameworks of He8 section, Zhao 30 wellblock.Studythe identification marks of sedimentary faciesbased on the comprehensive analysis of logging and cores.And Characteristics of the Sedimentary Facies have been concrete analyzed and described.The sedimentary system of He8 section, Zhao30 wellblock is mainly composed of river system. The sedimentary environment had suffered the transformation from braided river to transitional of braided-meanderingriver to meandering river. During the sedimentary period of the second section of lower He8 to second section of upper He8, the Zhao 30 wellblock had developed the typical braided river facies, and the sedimentary period of first section of upper He8 had developed meandering river facies.With the using of sequence lithofacies and paleogeography mapping, we choose the middle-term cycle sequence as the units of the sand body thickness contour,sandstone/strata contour, the diagram of sedimentary facies. Makes clear the sequence lithofacies and paleogeography characteristics and evolution characteristics of He8 section in Zhao 30 wellblock in this paper.