Sedimentary-tectonic transition and source and reservoir rocks in three major marine cratonic petroleum-bearing basins in western China

In the context of the sedimentary-tectonic evolution of petroleum-bearing basins and from the dynamic concept of transition of basin nature, petroleum-bearing basins in western China are divided into four types. The Paleozoic Tarim, Sichuan and Ordos marine basin have similar geological evolution and a source-reservoir system. After breakup of the supercontinent, all the three basins became passive continental margins from the Sinian to Early-Mid Ordovician and failed foreland basins from the Mid-Late Ordovician to Silurian, reflecting basin-range transition between the three blocks and ocean basins on their margins. The geological response of the tectonic evolution in the craton basins are manifested in three aspects: the first is deposition of two suites of source rock on continental margins and in failed foreland basins; the second is formation of paleo-uplifts, paleo-exposures and paleo-karst and occurrence of four basin-range transition surfaces on the cratons, and the third is that the Late Paleozoic transgressive sequences overlap on the Early Paleozoic regressive sequences in the step-like form, thus resulting in the formation of source rocks below and reservoir rocks above and cap beds.