TECTONO-SEDIMENTARY EVOLUTION AND OIL ACCUMULATION IN THE YISHU GRABEN,NORTHEASTERN CHINA

The study of basin geometry,filling paterns and sequences and regional tectonic framework of the Eogene basins reveals that the Yishu Graben,recognized as an incipient rift basin,is ascribed to a part of the Cenozoic rift systems in northeastern China.which is developed poorer than the Liaohe rift basin system,but better than northern Jiayi Graben.The rift basin has gone through four stages that are nearly simultaneous and synchronous with the evolution of other Cenezoie rift basins in northeastern China.They are prerifting uplift and erosion stage(Late Cretaceous to Paleocene),ex-tensional faulting and intense subsidence stage(Eocene),filling stage(Oligocene),and late reworking stage(end of Eogene).
The Eogene continental deposits 5000m and more thick in the Yishu Graben are believed to be the excellent source beds and reservoir rocks.The tectono-sedimentary evolution has created a wide range of the traps which are characterized by abundant occurrence but relatively small scale.The composite oil fields tend to be formed in the favourable locus for oil accumulation.