| The Upper Ordovician Lianghtag Formation is the main oil and gas production layer of the Ordovician carbonate rocks in the Tarim Basin.Accompanied by increasing extent of exploration and development,detailed study in Lianglitag Formation has been reported in regions.However,due to the variousness of Lianglitag Formation thickness and lithology among zones,the study of the stratigraphic distribution and sedimentary facies distribution of the Lianglitag Formation in Tarim Basin is still missing.This paper focused on this issue,based on multidisciplinary theories such as paleontological history,tectonics,logging geology,seismic stratigraphy,petroleum geology,carbonate sedimentary science.etc,via,outcrops,microscopic chip,sampling and analysis data,as well as drilling,logging,test oil,logging and geophysical data,combined with macroscopic and microscopic methods,summarized the stratigraphic distribution characteristics of the Upper Ordovician Lianglitai Formation in the whole basin Petrological characteristics,sedimentary facies types and distribution laws.Moreover,sedimentary facies plane distribution and pattern of the Upper Ordovician Lianglitag Formation in the Tarim Basin was established via single factor analysis and multi-factor comprehensive mapping method based on the study above.Tarim Basin is divided into four subregions,Taklimakan-Tongguzibazi subregion,the Keping subregion,Queerqueke-Tadong subregion and Luoxi subregion,based on lithology and lithofacies of the Ordovician strata.Before the Late Ordovician,The sedimentary facies of the Taklimakan-Tongguzibazi subregion Lianglitag Formation are mainly platform facies sedimentary,migrating to basin facies sedimentary afterwards,Queerueke-Tadong subregion are basin facies sedimentary during the whole Ordovician.In terms of,Keping subregion transtion from platform facies sedimentary to shelf-basin facies sedimentary started after the Ordovician Yingshan Formation.Luoxi subregion started from Late Ordovician,transiting from platform facies sedimentary to shelf-basin facies sedimentary.The sedimentary period of Upper Ordovician Lianglitag Formation is the main biological reef age of Ordovician in Tarim Basin.Lianglitag Formation which is the stratum of the biogenic reef community,mainly distributes in the Taklimakan-Tongguzibazi Formation,and divided into five sections in the Bachu-Tazhong area,with formation thickness ranging from 0-1270m;while in Tabei area,it is divided into three sections,whit formation thickness ranging from 0-200m;lithology is mainly open platform,platform edge and slope sedimentary limestone.Queerqueke Formation in Queerqueke-Tadong and Luoxi subregion are basin facies,thinner thickness,mudstone and sandstone lithology.In Keping subregion,Yingan formation and Qilang formation is the slope-basin facies,with relatively thinner thickness and,mudstone and argillaceous limestone lithology.Based on the comprehensive analysis of sedimentary facies,single well,flat distribution and wellbore combination,three isolated platforms of sedimentary pattern are shown in the Tarim basin during the sedimentary formation of Lianglitag Formation.Which is,they are Tabei platform,Bachu-Tazhong platform and Tangnan platform in order from north to south,whit slope platform outside sre and basin facies deposition.In the basin,from west to east,open platform-platform edge-slope-basin facies sedimentary changes to landscape and flat;from north to south,platform edge-slope-platform edge-open platform-platform edge-slope-basin-slope-platform edge-open platform fades sedimentary shows landscape and flat tendency.In the end,sedimentary facies model of the platform-platform edge-slope-basin is established in the Tarim Basin. |
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