Formation Mechanics And Distribution Forecast Of Carbonates Paleokarst Reservoir In T₇～4 Interface From Central Tarim Basin

T₇⁴ interface is the important seismic reflection interface, representing a large scale plane of unconformity, in Central Tarim Basin, the high-produced oil-gas fluid, in the Ordovician carbonates paleokarst under it, has been got. Profoundly realizing the mechanics of Formation and development of Carbonates Paleokarst reservoir has important theoretical and practical significance.Based on the result of division of sedimentary facies and analyses of sediment evolutive sequence, we rerun the Paleokarst topographical features of Central Tarim Basin in T₇⁴ interface times, divide it's variety , analyse the plane spreading rules and major Controlling factors and Formation mechanics of different Paleokarst topographical features units.Guided by the hydrogeology theory, we get the Paleohydrogeology stages of object strata , analyse the characteristics of Paleohydrodanamic field and Paleohydrochamistry field and the relation of they with development of reservoir pore space of Paleocave and migration and accumulation of oil/gas, simply discuss the trend of conservation and development of Paleokarst, and forecast the distribution of Carbonates Paleokarst reservoir in T₇⁴ Interface.The central conclusions as follows:(1)As the important unconformity interface of Central Tarim Basin, it's development went through five stages, the development course of ground water, in Carbonates aquifer rock series of Ordovician under it, 6 hydrogeology ages and 10 hydrogeology subages.(2)In T₇⁴ interface times, the characteristics of landform and topographical features of Central Tarim Basin is high west , low east, high centre portion and low around, landform degree of slope of the west and east of centre portion is slow and that of the south and north steep;based on the topographical features, we may recognize three Paleokarst topographical units,Paleokarst highland, Paleokarst slope and Paleokarst valley ,Paleokarst topographical units, holding different Paleokarst development characteristics , are all spreading from west to east.(3)Karstification regions and preservation trend under burial condition are tentatively studied with the chemical thermodynamics of water-rock interaction. The original reservoir pore space of Paleocave of limestone is easily preserved and that of dolomite isn't in the modern burial condition.(4)The development of paleocast is mainly controlled by the fector of rock types, tectonics, palaeoclimate , paleotopographic and Paleohydrogeologic condition. sequence stratigraphic research suggest that the development of Carbonates Paleokarst reservoir is controlled by the different grade of sequence Interface.(5)Under T₇⁴ Interface of Central Tarim Basin, the areas where the karstification and fractures were well developed and the favorable reservoir can be forecasted are near central fault zone and beside the south and north of it.