鄂尔多斯盆地西北部上三叠统延长组主要发育湖泊一三角洲沉积，是近年来石油重点勘探层系之一。长7段油页岩为烃源岩，生烃增压作用是长7段烃源岩异常高压形成的主要机制，异常高压是石油运移的主要动力。原油通过流体压裂缝、断层和叠置砂体进行运移，压力越大越有利于低渗透储层成藏。长7段烃源岩具有连续式生烃、幕式排烃、多点式充注成藏特征。包裹体均一温度、成岩特征等表明．烃源岩先向下再向上排烃，二次运移具有垂向运移为主、短距离侧向运移特征。利用声波时差测井曲线计算了长7段向下排烃厚度平均约10 in，向上排烃厚度平均约30 ITI，向下与向上排烃量之比约为l：3。

The Yanehang Formation in northwestern Ordos Basin is one of the most important exploration area which mainly developed lacustrine delta deposition．The Chang 7 oil shale is the source rock which produced high pressure during the main period of hydrocarbon generation．The overpressure is the main dynamic force for the oil migration to the low perm eability reservoirs through microfraetures faults and superposed sands．The Chang 7 sourae rock is characterized by continuous hydrocarbon-generation，episodic hydrocarbon expulsion and muhipoint injection．The source rocks firstly expeHed down to the lower reservoirs and then to the upper reservoirs according to the homogenization temperature and diagenesis and the secondary migration is mainly vertical and short lateral migration．The thickness of downward expulsion is 10 meter and the upper is 30 meter．The ratio of the upper and down hydrocarbon expulsion amount ofchang 7 is about 3:1．