内蒙古西部雅布赖盆地侏罗纪沉积-构造演化及油气勘探方向

Jurassic depositional-tectonic evolution in the Yabulai basin,western Inner Mongolia,China and direction of petroleum exploration

雅布赖盆地侏罗系为本区主要的勘探目的层。整个侏罗系表现为一个沉积水体由浅—深—浅的演化过程。中—下侏罗统青土井群自下而上划分为3段:第一段为断陷早期沉积的扇三角洲相;第二段为河流、湖盆发育时期产生的冲积扇、扇三角洲、滨浅湖、半深湖亚相等沉积;第三段是在湖泊范围明显增大时期形成的扇三角洲—半深湖亚相沉积。上侏罗统沙枣河组为盆地萎缩时期形成的滨浅湖、冲积扇—河流沉积。认为青土井群二段、三段是主力烃源岩。结合区域构造演化和圈闭条件分析,认为萨尔台凹陷为有利的勘探区,黑沙构造带、黑茨湾地层不整合带为较有利的勘探区带。

The Jurassic is the main exploration target in the YabulaI basin. The whole of the Jurassic in the area witnessed a process of evolution of a depositional water body from shallow→deep→shallow. The Mid-Lower Jurassic Qingtujing Group may be divided in ascending order into three intervals： the first interval is the fan delta facies deposited in the early stage of downfaulting; the second interval is alluvial fan, fan delta, lakeshore and shallow lake and semi-deep lake subfacies deposits formed during the development of rivers and lake basins; and the third interval is fan delta and semi-deep lake subfacies deposits formed during the expansion of the lake basin. The Upper Jurassic Shazaohe Formation is lakeshore-shallow lake and alluvial fan-alluvial deposits formed during the recession of the basin. The authors think that the second and third intervals are major hydrocarbon source rocks. Based on the above-mentioned analysis, combined with an analysis of the tectonic evolution and trap conditions, the authors conclude that： the Sartai subbasin is a favorable exploration area and the Heisha tectonic zone and Heiciwan stratigraphic unconformity zone are relatively favorable for oil exploration.