The Structural Types and Depositional Characteristics of Carbonate Platform in the Cambrian-Ordovician of Tarim Basin

Tarim basin underwent the ramp carbonate platform of early-middle Cambrian,rimmed shelf carbonate platform of late Cambrian-early middle Ordovician,isolated carbonate platform in the early period of late Ordovician,and drowned carbonate platform in the middle-late period of late Ordovician.The different carbonate platform has distinct diversities in the section structure,platform edge feature and facies constitution,and controls the types and features of facies in the different regions and the upgrowth condition and the distribution rule of source rock,reservoir and caps.Through the sequence stratigraphy study of the seismic and loggings,4 types of carbonate platform structure have been established and 5 sequence-facies models been summarized.During carbonate platform evolvemeot,two periods of platform slope are developed: The first platform slope is formed in Cambrian-early middle Ordovician,controlled by Well Kunan 1,WellMancan 1,WellTadong 2 route,represents arc belt toward the west.The second platform slope is formed in the late Ordovician,constrained by Well Kunan 1,WellMancan 1,WellTazhong 1 and WellTangcan 1,represents arc belt toward the east.The shifting and variation of the slope reveals the change of carbonate platform types.