塔中地区C_Ⅲ油组成藏特征

POOL-FORMING CHARACTERS OF C_Ⅲ OIL-BEARINGGROUP IN CENTRAL TARIM REGION

塔中地区CⅢ 油组是塔里木盆地塔中隆起主力产层 ,由石炭系巴楚组底砂岩及泥岩构成储盖配置。海西早期运动所形成的区域性不整合 (Tg3) ,一方面使早期形成的古油气藏遭受破坏 ;另一方面使主力烃源层即中 上奥陶统停止生烃。海西末及其以后 ,中 上奥陶统二次生排烃、圈闭形成 ,是CⅢ 油组主要成藏期。多次构造变形造成石炭系褶皱 ,形成了一系列近EW向的三级构造带 ,发育大量的圈闭构造群。三级构造带的空间组合形成油气运移的汇烃脊。圈闭是否能够形成油气藏 ,取决于其是否处于汇烃脊之上。

C Ⅲ oil gas bearing group is the principal pay bed in Central Tarim Basin.It is composed of Donghe sandstone as reservoir rock and shale of Bachu Formation as sealing bed.The regoinal unconformity originated in ealier Hercynian tectonic movement did not only destroy the hydrocarbon pools formed earlier,but also stopped the main source rocks from hydrocarbon generating of Middle Upper Ordovician.Since the Late Hercynian,the main source rocks started secondary hydrocarbon generating and expelling,and trap forming stage was the main pool forming stage of the C Ⅲ group.Multi tectonic deformation resulted in a series of Carboniferous third order structural belts of east west strike and a lot of traps.The spatial arrangement of the third order structural belts formed hydrocarbon confluent ridges.The traps can develop into hydrocarbon pools or not are determined by the location whether the traps are on the ridges or not.