Sedimentary Facies And Reservoir Analysis On Key Outcrop Sections In Xiashihezi Formation,Permian In Ordos Basin

Ordos Basin is a large multi-cycle superimposed basin.Many large gas fields such as Sulige gas field,Mizhi gas field,Yulin gas field and Zizhou gas field have been found in the basin.The Xiashihezi 8 and Shan 2 are the main exploration sections of the Upper Paleozoic natural gas resources.Although abundant natural gas resources have been found in Xiashihezi Formation,at present,downhole data are common in petroleum production,outcrop analysis data are less.Based on the analysis of sedimentary facies,this paper explores the types of sedimentary facies in reservoir development and clarify the origin and distribution characteristics of reservoirs,which provides a good geological basis for further oil and gas exploration.In this paper,through sorting out the previous research results and regional geological background data,Pingliang section,Hancheng section and Ningwu section of the Ordos Basin are selected to carry out surveys to obtain lithological,stratigraphic thickness and paleontology data.On the basis of stratigraphic division,the types of sedimentary facies are identified by petrological marks,sedimentary structural marks,paleontological marks,geochemical marks and other sedimentary facies identification marks.It is believed that the Xiashihezi Formation develops fluvial delta facies and lacustrine facies.Two kinds of sedimentary subfacies in the delta plain,the front and a total of nine microfacies such as braided channel and underwater distributary channel can be identified.Lacustrine facies includes shore-shallow lake subfacies,shore-shallow lake sand bar and shore-shallow lake mud.Sedimentary facies models of different sections in different periods are established.By studying the petrological characteristics,physical properties,pore types and structures of the reservoirs in different sedimentary facies of Xiashihezi Formation,the reservoirs are comprehensively evaluated.It is considered that the most favorable sedimentary facies of Xiashihezi Formation in southern Ordos Basin is braided channel microfacies.