Study On The Sequence Lithofacies Paleogeography Of Upper Ordovician Lianglitage Formation In Tazhong Area,Tarim Basin

The Ordovician strata in Tazhong area had a large thickness,and the upper Ordovician Lianglitage Formation has been of the main reservoir for oil and gas in Tazhong carbonate platform.In previous research,the studies of the Lianglitage Formation mainly based on the lithologic stratigraphic section and third order sequence stratigraphy framework.This paper mainly focuses on the detailed high-frequency cyclic sequences framework research and the forth order parasequence group cyclic sequences lithofacies palaeogeography research.In this research,using the method of concentrated drilling core and cuttings conodont sample analysis of the Lianglitage Formation,and proof the Lianglitage Formation in the Tazhong area deposited continuously without hiatus,and establish the stratigraphic framework of the Lianglitage Formation which can be compared through the all Tazhong area.Through the analysis of the lithology and lithofacies and sedimentary sub facies and meter scale cycles of the Lianglitage Formation drilling cores in the Tazhong platform different sedimentary area,clear and definite the sedimentary sub facies classification of the Tazhong Lianglitage formation,and draw the Lianglitage Formation different sedimentary sub facies image log curves chart board.Based on the sedimentary sub facies image log chart board,using the whole well segment image log data,carry out the high frequency cyclic sequences overlay relationship research.Include using the image log to identify the different meter scale cycle types of the Lianglitage Formation,and meter scale cycle stack into fifth order cyclic sequence,and fifth order cyclic sequence stack into forth order cyclic sequence.Through the research of the image log high frequency cyclic sequences between the different area,establish the Lianglitage forth order cyclic sequences stratigraphic framework in Tazhong area,and make sure the dominant sedimentary facies of the nine forth order parasequence group cyclic sequences(Sq9-Sq1)between the different Tazhong area.And first time use the forth order parasequence group cyclic sequences as the base drafting unit,drawing the every(Sq9-Sq1)forth order cyclic sequences period sedimentary facies distribution map.Then system study the different sedimentary period sedimentary facies distribution and depositional pattern characteristics.And the third order relative sea-level change control effect on the forth order relative sea-level change.The Lianglitage high energy platform marginal reef facies oil and gas reservoir has strong lithology heterogeneity,and mainly controlled by different level relative sea-level changes in Lianglitage sedimentary period and the Tazhong No.1 slope break intensity tectonic activity.The different level relative sea-level changes control the change water level of the Lianglitage Formation sedimentary period,and then control the sedimentary facies distribution pattern,and the strength of the Tazhong No.1 slope break intensity tectonic activity between the different Tazhong area control the high energy banding platform marginal development models of the Lianglitage Formation.