The Study Of Sequence Stratigraphy And Sedimentary Characteristics Of Lower Ordovician In The North Slope Of Tazhong Area In Tarim Basin

the north slope of Tazhong area in Tarim Basin located in the central part of central uplift belt in the Tarim Basin. The purpose layer is Yingshan Formation and Penglaiba Formation of Lower Ordovician. Considering the exploration situation of the study area, based on the sequence stratigraphy, structural geology, sedimentary petrology, deeply discussed the rock types, sedimentary facies features, sequence stratigraphy characteristics and reservoir characteristics. Combined with the seismic data, logging data and the single well sequence data, established the sequence stratigraphic framework, studied the distribution of sedimentary facies in the sequence framework, draw the Seismic facies and sedimentary facies planar graph based on the system tracts, analyzed the main control factors and laws, Summarized the sedimentary model, and preliminary study the reservoir characteristics and the control factors in the framework of sequence.Influenced by the early Caledonian and Hercynian movement, the Ordovician north slope of Tazhong area has formed the sedimentary framework with depression and uplift. in the early Ordovician period, because of the low water and the dry climate, restricted platform is widely developed.Based on the sequence stratigraphy,combined with the study of sedimentary background, the rock stratum, seismic stratigraphy analysis,we can identify 1 uplift unconformity sequence interface of the secondary SSB1(T80), and 2 erosive unconformity sequence interface of the three levels,include SB2(T78)and SB3(T76),their are two inner sequence levels in the Yingshan Formation and Penglaiba Formation, they are mfs1 and mfs2,we an divide it into two third-order sequences(SQ1,SQ2), 6 four-order sequence. Based on the research of well profile and sedimentary facies,study on the sequence stratigraphic framework sedimentary facies and its controlling factors,Establish study area sequence and sedimentary evolution models. Finally form the sedimentary facies plan, and reveals the sedimentary facies distribution.The Ordovician of tazhong North Slope sequence formation and controling factors are tectonic subsidence, sea-level changes provenance and paleo-climatic conditions. The main performance on the control function of tectonic movement is the influence in the sequence boundary and the sedimentary paleogeomorphology; Sea level fluctuation control the formation of three-level sequence boundary and succession of sequences within the system domain; the sufficience of provenance canaffect the thickness and the physical property of sequence; Paleo-climate change is affecting the changes of carbonate platform facies types and locations.Tazhong North Slope area experienced the impact of multi period tectonic movement and sea level changes, form the different levels of sequence boundary,develop exposure and erosion discontinuous interface, corresponding to the different time when different levels of corrosion develop, which is an important factor that control the formation of the high quality dolomite reservoir in later Ordovician,the Tazhong north slope.