Reservoir-forming history of Ordovician reservoir at Well Tazhong 45 in the northern slope of Tazhong uplift

The difference of sterane and terpane distribution indicates that the source of Tazhong 45 well Ordovician reservoir oil is different from the other oil of Tazhong 10, 11, 35 well on the North slope of Tazhong uplift. Correlation between oil and source rock shows that the Ordovician reservoir oil of Tazhong 45 well is derived mainly from Cambrian source rock. According to the occurrence and structural feature of CaF_2, it can be inferred that the No.I fault activity maybe response for the generation of CaF_2.Integrated with the result of oil-source correlation, and the occurrence of bitumen with different reflection ratio and different fluorescence, it can be deduced that perhaps there are three phase oil charging to the Ordovician reservoir of Tazhong 45 well: that is in the Early Ordovician, Permian and Cretaceous. And the oil yielded in the Permian from the source rock of Cambrian-Lower Ordovician in the west of Manjiaer Depression and in the North Slope of Tazhong Uplift is the dominant section of the current reservoir.