Characteristics Of The Ordovician Sedimentary Facies And Favorable Exploration Zone Analysis In Southeast Area Of Sichuan Basin

The southeast area of Sichuan is located in southeast of Sichuan Basin,acrossing Sichuan,Chongqing,Guizhou,Hunan,Hubei and other provinces.Although there are sporadic oil and gas shows in the Ordovician of Sichuan Basin,but the research degree is relatively weak,and lack of awareness of the potential of oil and gas exploration in the basin,and then through to the stratigraphy,carbonate petrology,structural geology and sedimentology theory as the guide,based on field investigation and indoor,macro and micro combined method,to study the stratigraphic framework,sedimentary facies,facies marks,planar distribution rules into research of The Ordovician in southeast area of Sichuan Province,the research results of oil gas exploration in the area has certain guiding significance.We achieved the following results:(1)The formation characteristics of Ordovician in southeast Sichuan basin:In the lower Ordovician Ordovician Tongzi formation,mainly the develop dark gray mudstone,deep gray light crystal oolitic grain limestone,gray,dark gray,mud dolomite,micritic calcite dolomite;thickness of about 67-153m.The lower Ordovician Honghuayuan formation,develop deep gray bioclastic limestone and dark grey Oolitic Limestone,calcarenite;thickness of about 4-89m.The lower Ordovician Meitan formation is dominated by silty mudstone and mudstone,with a thickness of about 162-288m.The Middle Ordovician Shizipu formation,the development of gray containing marl mudstone marl;thickness of about 3-21m.The Middle Ordovician Baota formation,the development of grey bioclastic limestone,marl,marl;thickness of about 21-61m.The upper Ordovician Linxiang formation in greyish yellow and gray green in the thick layer of nodular limestone,argillaceous limestone,marl or tuberculate;thickness of about 4-20m.The upper Ordovician Wufeng formation,mainly for gray silty shale and limestone;thickness of about 2-10m.(2)Through single well logging analysis,and system measurement of peripheral outcrop,and detailed study of the facies marks of the Ordovician in the southeast area of Sichuan province,The Ordovician in Southeast Sichuan Basin divided carbonate platform?shlf and mixed platform 3 sedimentary environment.The platform is divided into 3 subfacies and 11 microphase,which are restricted platform,open platform and platform margin.The shelf is divided into shallow shelf 1 subfacies and3 microfacies corresponding.The mixed platform is divided into 1 subfacies belts and2 microfacies.(3)The study on the sedimentary evolution showing that in southeast area of Sichuan in Tongzi period mainly developed lagoon sediment,limited intraplatform point beach and open platform shoal;In the Honghuayuan sedimentary period,the relative depth of the water body in Tongzi is relatively deep,which is mainly for the open platform environment,and the distribution of the shallow sediments is wide.;Early Meitan formation,the basin occurred large-scale transgression,lithofacies transition characteristic is obvious,for mudstone and shale is covered in limestone,Lin 1 well,Dingshan 1 well,Shizhuqiliao,the region's growth and development is dominated by mudstones in argillaceous shallow shelf facies.Meitan formation in the middle depositional period,the sea level drops,lithologic conversion interface is significant,performance for argillaceous siltstone,raw limestone covered on the lower mudstone,for silty argillaceous shallow shelf and mixed product shelf deposits;The late Meitan formation,and the sea level continued to rise,development and mixed shelf diamictic platform mainly argillaceous shallow shelf;Cross Meitan formation-the Baota formation sedimentary period,basin underwent a complete eustatic cycles,basically not affected by the source,development rimmed carbonate platform.Linxiang formation sedimentary period mainly developed carbonate rock platform,which Jianshen 1 well-Sanxing 1 well-Xishuituhechang to the East,Xiushanrongxi area west of deep depression and other areas open platform shoal deposits and local development of Point Beach,such as Lin 7 wells,Dingshan 1 well bioclastic beach.And the connected wells profile of sedimentary phase contrast analysis of the characteristics and temporal and spatial distribution of each phase is studied and established the depositional model of each phase of the Ordovician.(4)Through this study,the Middle and Southeast Ordovician limestone and dolomite mainly developed in Tongzi group and red garden group.At the same time on the basis of permeability test and analysis showed that the Tongzi formation and Honghuayuan formation has a certain reservoir.The southeast area of Sichuan Province favorable exploration zones deposited mainly in the open platform shoal restricted platform Tongzi group oolitic and red garden groups.Comprehensive seismic facies,sedimentary facies,reservoir characteristics and reservoir prediction research pointed out that in Ordovician Tongzi formation of favorable reservoir zone is located in between the Lin 1 well-Dingshan 1 well-Longsheng 1 wells,the area of favorable zone is 5451.255km~2.