Abstract:

Abstract:  In the north of the Tazhong Area in Tarim Basin, a large condensate pool of reefflat facies and a large karst weathering crustal oilgas field have been discovered, which demonstrates a breakthrough in the oilgas exploration in carbonate rocks of Ordovician marine faciesBy using organogeochemical indexes combined with the analysis of the evolution of tectonicsedimentation some good results have been achieved in the study of the effective hydrocarbon source rock and the accumulation processBut as the exploration depth increases, the complexity of fluid distribution becomes a more and more prominent problemThrough the research on the Ordovician oilgas accumulation in the north of the Tazhong Area by dating and analysing the natural gas components and their isotopes, we could sum up the mode of pool formation in Tazhong as follows: There were three periods of formation and two periods of adjustment; oilcharging occurred in the early stage and gasinjection occurred in the later stage; oilgas accumulated in multifashion and oilbearing rocks were widespreadIt is confirmed that the natural gas is mainly the oilcracked gas in the Tazhong Area and it is emphasized that the gasinjection in the later stage is the key to the formation of the largescale gas field in Tazhong

Key words:

Key words: nonhydrocarbon; Ordovician; Tazhong Area; crude oil cracked; gas cutting; multiple hydrocarbon accumulation