Geological Conditions of Oil and Gas Enrichment in Carbonate Reservoirs of Tazhong Area,Tarim Basin

The Tazhong paleo-uplift is a multiple oil-gas accumulation play,and medium-large scale reservoirs have been found in the Carboniferous,Silurian,Ordovician and Cambrian Systems.The achievements in oil-gas exploration and exploitation and the researches on its petroleum geology show that large scale reef flat deposit of Tazhong No.1 slope-break zone,large weathering crust of the karst reservoir are the most important exploration areas for large and oversize oil-gas fields.First,the inherited paleo-uplift is the foundation of oil-gas migration and accumulation;Second,multiple charging sites and multistage pump type charging are the key factors for wide distribution and local enrichment of oil and gas in marine carbonate reservoirs of the Tazhong area;Third,multiple pore-cave-fracture carbonate reservoirs of high quality are the preconditions for large scale unconventional condensate oil-gas fields.In a word,the Upper Ordovician reef flat deposit and the Lower Ordovician weathering crust karst reservoir are important exploration areas,where oil and gas are widely distributed in lateral and vertical directions.