Basin Superimposed Relationship And It's Influence On The Hydrocarbon Accumulation Conditions Of Upper Paleozoic In Linqing Depression

LinQing Depression is a Meso-Cenozoic composite and superimposed basin, and it′s late Paleozoic basin strcture was disintegrated. The upper palaeozoic Coal source rocks distribution, burial history, thermal evolution, and hydrocarbon-generating history have obvious differences in different tectonic position; the main reason is that composite relationship between prototype basins of different types generated in the early and later tectonic epochs. Therefore, restoring prototype basin in different geological period and ascertaining the composite relationship of prototype basins has the important practical significance for Upper Paleozoic petroleum exploration.According to the division results of structural strata, the main tectonic transformation period of LinQing Depression were divided into eight stages: Carboniferous-Permian, Early-middle Triassic, late Triassic epoch, Jurassic Period, Early Cretaceous, Late Cretaceous, Paleogene, Neogene-Quaternary. LinQing Depression′s regional structural framework trend is northeast, and it's basin structure is characterized by graben-horst structure and west faulting and east overlapping. Stretch tectonic style is the main structure style, and stretch-slip, compression, inversion structure style appears in some local areas. Basin-controlling fault and all the NWW directional faults began to active in Early Cretaceous, others faults most began to active in Paleogene, NWW and nearly EW directional faults adjusted stretching deformation and separated the basin structural framework during Paleogene active stage; Balanced cross section technique showed that LinQing Depression experienced five different stages since the uplift in Late Triassic: stretching and subsiding in Jurassic, violent stretching in Early Cretaceous, compression and tectonic uplift in Late Cretaceous; violent stretching in Paleogene, slight stretching in Neogene-Quaternary.The formation and structural evolution of LinQing Depression were controlled by dynamical mechanism of the plate movement, lithospheric thinning and activity of deep fault. The result of restoring prototype basin shows the basin evolution of LinQing Depression includes Late Paleozoic cratonic basin cycle, Early-Middle Triassic intracratonic basin stage, Late Triassic uplift and denudation process( nearly north-south-trending compressional stress ), Jurassic intermontane depression period, Early Cretaceous faulted basin stage, Late Cretaceous wholly lifting and local sinking state, Paleogene intensively faulting and sinking period, Neogene-Quaternary post- rifting depression phase.Based on the superimposed relationship between Mesozoic and Cenozoic prototype basins, the superposition units of the LinQing Depression were classified, and the hydrocarbon accumulation conditions of Upper Paleozoic of different superposition units were analysed, as the result showed thatâ…¡4 unit (erosion(J) to erosion(K₁) to erosion(K₂) to subsidence(E)),â…¡1 unit ( subsidence(J) to subsidence(K₁) to erosion(K₂) to subsidence(E)) were relatively favorable hydrocarbon accumulation area, and thenâ… unit (continuous subsidence),â…¡2 unit (subsidence(J) to subsidence(K₁) to erosion(K₂) to erosion(E)) comed second,â…¡3 unit(subsidence(J) to erosion(K₁) to erosion(K₂) to subsidence(E)),â…¢unit (continuous erosion) accumulation conditions were the worst.