TIMING OF HYDROCARBON GENERATION AND MIGRATION AND DETERMINATION OF MIGRATION DIRECTION AS WELL AS EXPLORATION DIRECTION IN THE ORDOS BASIN

On the basis of vitrinite reflectance,K-Ar ages and apatite fission-track data,the time of hydrocarbon generation and migration,migration direction and hydrocarbon exploration direction are discussed starting with the reconstruction of the subsidence and uplift history and geothermal history of the Ordos Basin.The major time of hydrocarbon generation and primary and secondary migration was in 170～160 Ma(the end of the Middle Jurassic).After 23 Ma(the Miocene),a regional secondary migration of the second phase took place.All kinds of traps in the middle and eastern parts of the basin,especially the crust of weathering at the top of the Ordovician,belong to favourable targets for exploration.And the traps on the eastern side may be more favourable.