The Tectonic Genesis and Exploration Targets of Large Oil-Gas Fields in Tazhong Area,Tarim Basin

Tazhong uplift developed stably in its long history and its basic structure framework was controlled by Tazhong No.1 and No.2 Faults.Faults in central uplift belt and Tazhong No.10 structural belt were formed in Middle Ordovician and affected the faults developed in later stages,showing obvious multistage inherited feature.Two sets of major hydrocarbon source rocks,Cambrian-Lower Ordovician and Middle-Upper Ordovician,were deposited on the two flanks of Tazhong uplift.The complicated fault structure in Tazhong area is characterized by that: multistage thrust structure from the south to the north formed in early Paleozoic controlled the development of reef-flat complex and weathering crust karst reservoirs in marginal facies zones of Tazhong area,and improved the properties of all kinds of reservoirs,thus forming multiple sets of reservoirs differentially distributed and controlled by the structures.It remained for a long time that petroleum was in migrating and accumulating from slope to uplift and from the deep to the shallow through faults.The multistage structural evolution and reservoir configuration allow to form the Silurian-Carboniferous drape clastic structural-lithologic reservoir,the Upper Ordovician sedimentary facies controlling reef reservoir,the Ordovician weathering crust reservoir and the Cambrian dolomite lithologic reservoir,which are as four major exploration domains.The Cambrian-Ordovician carbonate reservoirs are the main targets for exploration in Tazhong area,while the Silurian Carboniferous to Clastic reservoirs are the secondary targets.