陕北气区形成中的再次运移

陕北斜坡中部下奥陶统顶部侵蚀带里所发现气藏的天然气，主要来自下奥陶统本身的烃源岩．烃源岩有三个生烃中心，分布在中央古隆起的南、西北和东北方．于二叠纪末，生烃中心的有机质进入成熟阶段，发生了生油过程，经运移就近聚集到中央古隆起中，形成巨大的含油区．在三叠纪至第三纪间，随着鄂尔多斯盆地的形成，中央古隆起湮没在陕北斜坡中，原油被裂解成为天然气，并且发生了再次运移，形成了陕北气区．

Secondary Migration in Forming of North Shaanxi Gas Area

The gas discovered at the top of Lower Ordovician Series erosion zone located in the centralpart of the slope of North Shaanxi ,is mainly from the hydrocarbon source rocks of this period. The hydrocarbon source rocks werc generated in thrce gencrating centres :the south ,the northwest and the northeast of the central paleohigh. In the end of Permain period ,the organic matter in the three centres matured and migrated ,then accumulated in the central paleohigh to form a large oil-bearing area. With Eerduosi Basin forming in the periods of Triassic and Tertiary ,the ceniral palcohigh was annihilated in the slope of North Shaanxi,where the crude was cracked into gas,and the gas migrated secondarily to create North Shaanxi gas area.