| The research area is Tazhong area which is in the center of the Tarim basin. Based on the tectonic setting of this area and guided by sedimentary petrology, sedimentary theory, the sedimentary facies and characteristics of which were studied and described with core,thin-section,well-log and seismic data.The restricted platform, the open platform, the margin of platform and the shelf or basin facies were identified and depicted.On that basis the author of this paper studied the features of the stratigraphy sequence in this region guided by the conception and theory of P.R.Vail'sseismicstratigraphysequence, chronostratigraphy,petrostratigraphy, Isotopic stratigraphy ,iostratigraphy and so on multidisciplinary stratigraphy and towards the standardization of sequence stratigraphy. Ten sequence boundaries and some important surfaces in the sequence and 9 sequences were recognized with the integration core, well-log and seismic data in the area.5 well tie profiles and 5 main seismic profiles, and a lot of cross line were selcted to interpret and depict the feature of each sequence,surely Well and seismic constrains each other.By studing the specific stratal stacking patterns and bounding surfaces, and consists of a tract of correlatable depositional systems and the interplay of accommodation and sedimentation , a sequence stratigraphic framework of the Ordovician in Tazhong area of Tarim basin was established.Sedimentary facies in each sequence were detailedly studied and according to the sedimentary characteristics of every sequence, SQ3, SQ4, SQ5, SQ6 was selected to map sedimentary phase plane in accordance with sequence, but SQ7 in accordance with systems tract.The Khattak uplift became rudiment uplift in the early Caledonian, mainly shaped in the medium-term period of Caledonian and formalized of early Hercynian. Those tectonic movements had significant impact on sedimentary, sequence and reservoir reconstruction of Ordovician by fractures and unconformity whicth caused. The interval-entropy map and strontium isotope ratios trends of the Ordovician in the area show that sea level of the Ordovician overall increased. Drill core, well logging, and seismic profiles shows SQ1-SQ2 mainly developed thick layer of restricted platform limy dolomite, dolomitic limestone deposition, was conformable contacted with underlying Furongian of Cambrian. SQ3 and SQ4 major developed constraints - open platform facies platform margin and slope - shelf sediments Only developed in north-east and south-east sub region of the study area. Occurred after deposition of SQ5 the mid-â… screen Caledonian tectonic movement eroded most of strata of SQ5, even denuded SQ3 and SQ4 in the structural high position. The residues are open platform ,platform margin and slope to basin facies, wells drilled in this sequence are mainly distributed in deep water areas in platform margin transition zone, such as Tangcan 1, Tz88 Gulong1, Tz 29 wells, Z41,Z2 wells. Then, the sea-level rise, low position in the area such as platform margin slope and the continental shelf to basin area deposited SQ6'gray and crimson knollenkalk deposits, the sequence only drilled by Gulong 1, Tz88 , Tangcan 1 Well, Tz29 well. When SQ7 deposited the area was isolated platform, widely developed open platform and platform margin, including reefs, reef flat, carbonate sands and other favorable carbonate reservoir facies which are parallel to the platform edge or locate in energetic area in open platform. In south and north of the area was shelf and basin facies such as Tangcan1 and Glong1,Tz34,Tz33,Shun1 well area.Then, the mid-â…¡screen movement of Caledonian eroded the strata of SQ7 differently even the underlying strata.And then Large-scale transgression happened, carbonate platform demised, SQ8 and SQ9 were mainly shelf and basin facies.some area saw turbidite basin facies such as Tz29,Gulong1,Tangcan1well and so on.Then the mid-â…¢screen movement of Caledonian and the early Hercynian movement changed those strata.The author hold that from the sequence SQ1 to SQ4 of Ordovician in the Tazhong area belonging to the stable aggradation's sequences, are chiefly controlled by eustatic sea level change, while the sequence SQ5 to sequence SQ9 belonging to the tectonic drowning sequences are mainly controlled by regional tectonic movement because of generally eustatic sea level rise.At last, based on the previous study results about the controlling factors of Ordovician carbonate reservoir in the area and the characteristics of Sedimentary and sequence and Combined with the configuration among generating rock,reservoir and cap and with the generating conditions of oil-gas reservoir, that favorable reservoir are mainly distributed in burial hill with karsted well and fractured in the central study area and high-energy sedimentary facies in south and north Slope zone with well karst and fracture.
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