The Ordos Basin is one of the most important hydrocarbon prolific basins in China. Based on seismic data and horizon flatterning as well as seismic balance section technique, dynamic analysis regarding the formation and the history of the migration and evolution of the Tianhuan depression was conducted. Two main results were obtained: 1) the Tianhuan Depression was primarily formed during the Late Jurassic and later its axis migrated about 30 km eastward to current position due to the impact of the late Yanshan and Xishan tectonic movements; and 2) when the axis of the depression moved near to the effective source rock area, the previous pool readjusted and the hydrocarbon migrated to and accumulated at the higher position of the west part of the Tianhuan Depression and consequently secondary structural reservoirs were formed.
