关键词: 地层流体, 油气成藏, 古生界, 塔里木

Abstract:

Cambro-Ordovician mudstones,upper Cambrian and Carboniferous gypsum rocks and the relatively tight lithologies have blocked the vertical migration of formation fluids in Tarim basin.In Paleozoic,Tarim basin experienced 6 tectonic movements,including Caledonian(early,late and last)and Hercynian(early,late and last).Except the last stage of Hercynian,all the other tectonic movements were mainly of elevation and subsidence movements and weak eompressional movements,thus they are characterized by limited destruction scopes and faults of small magnitude,resulting in strong vertical compartmentalization of formation fluids.The salinity of Paleozoic formation water in Tarim basin is of brine water level,which is the highest in the Ordovician,the next is in the Carboniferous,while that in the Silusian is the lowest.Preservation of the low salinity features in Silurian indicates that the Paleozoic formation fluids have been strongly compartmentalized;as a result,most hydrocarbons would mainly migrate laterally along the Paleozoic regional unconformities.Vertically,hydrocarbons are mainly distributed along the source beds, while laterally they are distributed both in depressions and uplifts along the migration pathways.

Key words: formation fluid, hydrocarbon accumulation, Paleozoic, Tarim basin