西藏羌塘盆地古油藏发现及其意义

Discovery of paleo-oil-reservoir in Qiangtang basin in Tibet and its geological significance

古油藏带位于羌塘盆地中央隆起带南部羌南坳陷比隆错 -昂达尔错地区 ,东西长 10 0km ,南北宽 2 0km ,为一狭长湿状油苗群 ,露头上岩石的颜色呈暗褐色、褐灰色 ,为中侏罗统布曲组的白云岩。沉积环境以生物礁组合为主。经对比 ,古油藏油气主要来源于下侏罗统烃源岩。生烃过程模拟反映羌塘盆地有两次生排烃过程 ,第一次发生在 14 0～ 15 0Ma ,第二次发生在 2 0Ma至现今。

Palaeo oil reservoirs are distributed in a narrow belt, 100?km long in E W direction and 20?km wide in S N direction, in Bilongco Angdarco area of Qiangnan depression in the southern part of the central uplift zone of Qiangtang basin.They are exactly a group of oil seepages.The outcropped rocks are the Middle Jurassic Buqu Fm.,dark brown and brownish gray dolomite.They are deposited mainly as biohermal complex.Correlation shows that hydrocarbons in the palaeo oil reservoirs have been sourced mainly from Lower Jurassic.Modelling of hydrocarbon generation process indicates that there have been two hydrocarbon generation and expulsion processes,one in 140- 150?Ma and another since 20?Ma. The discovery of the palaeo oil reservoir belt further verifies that Qiangtang basin has good petroleum prospect.