塔里木盆地古生界流体的垂向分隔性

塔里木盆地古生代寒武-奥陶纪泥岩、晚寒武世和石炭纪的膏岩层及较为致密的岩性阻碍了地层流体的垂向运移。塔里木盆地古生代经历了加里东(早、晚、末)和海西期(早、晚、末)6期构造运动,除海西末期外,其他期次的构造运动主要以升降运动和弱挤压运动为主,破坏范围局限,所产生的断层规模小,导致地层流体具有较强的垂向分隔性。塔里木盆地古生界地层水矿化度达到卤水级别,奥陶系最高,石炭系次之,志留系最低。志留系低矿化度特征得以保持,表明了古生界地层流体的分隔性强,决定了油气主要以古生界区域性不整合面为通道进行侧向运移。在剖面上,油气主要是沿生烃层系分布,在平面上,沿油气运移路径,从坳陷至隆起皆有油气分布。

Vertical compartmentalization of fluids in Paleozoic strata, Tarim Basin

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 experi- enced 6 tectonic movements,including Caledonian(early,late and last)and Hercynian(early,late and last).Ex- cept 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 mag- nitude,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 for- mation fluids have been strongly compartmentalized;as a result,most hydrocarbons would mainly migrate laterally a- long 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.