Abstract:

In the east part of the North China,there are potential carbonate source rock of sea facies of Lower Paleozoic and good coal formation source rock of Upper Paleozoic. Undergoing multiple types of superimposing process of basins with multiple episodes and different scales, and experiencing uplift, erosion and change of multiple episodes among the superimposing episodes, Paleozoic source rock in different areas has different hydrocarbon generation histories. Strata calibration and RO data indicate that there should be Triassic deposition of big thickness in Jiyang depression, and superimposing process of Triassic basins is crucial for hydrocarbon generation history of Paleozoic source rock. With basin superimposing model and evolution grade of Upper Paleozoic referred, the generation history of Paleozoic source rock is divided into three stages, Triassic as the early stage, Jurassic to Cretaceous as the middle stage, and since Early Tertiary to now as the late stage. The areas such as Jiyang depression and Dongpu sag with imbedding histories of shallow imbedding in the early stage, uplift in the middle stage and deep imbedding in the late stage have big potentials of secondary hydrocarbon generation. The balanceable surface superimposition of Upper Paleozoic basin makes RO of Lower Paleozoic  higher than Upper Paleozoic, and the difference is more than 0.3%. So in the end of Triassic, Lower Paleozoic source rock achieved hydrocarbon generation peak, which expensed the initial organic matter and reduced the potentials of secondary hydrocarbon generation to some extent.

Key words: the east part of the North China, superimposed basin, Paleozoic, hydrocarbon generation history, secondary hydrocarbon-generation