Tectono-Sedimentary Evolution Since The Late Paleozoic And Natural Gas Formation In The Southern North-China Basin

The Southern North-China Basin spans the North-China plate and the southern tectonic belt of North-China plate, meanwhile, it is adjacent to the North Qinling orogen belt. Its formation and evolution is controlled by Qinling-Dabie orogen belt and affecting by the mid-Cenozoictectonic evolution of East China and the Tancheng-Lujiang fault zone. These years, Indication of oil and gas and small coal-formed oil reservoir which comes from Upper Paleozoic is founded gradually this area, which display good exploration prospect of Upper Paleozoic. Therefore, In order to evaluate condition of oil geology of Upper Paleozoic. The paper consider the Southern North-China Basins as a whole and study the Tectono-Sedimentary evolution since late palezonic and conditions of oil and gas and to solving some key geological issues related to hydrocarbon exploration in the region.The research base on the theories of plate tectonics and Continent geodynamics, use the method that petroliferous basin is analyzed integrally, dynamically and comprehensively, and the investigation in the field was combined with research indoors, Studies are mainly on classifying tectonic-sequence and the multiple stratigraphic division and correlation of important exploration target in the Southern North-China Basin;confirming tectonic environment of every tectonic era and by its control of corresponding prototype basin;analysising the overthrust tectonic system in northern Qinling-Dabie orogenic belt and essential geological elements and various geological processes of Upper Paleozoic hydrocarbon accumulation system. Some conclusions are listed as follows:The plateform cover cap of the Southern North-China Basin can be divided into six tectonic sequences. The tectonic evolution of the Southern North-China Basin can be classified in eight stages: the intercratonic depression formation phase in the setting of weak-extensional (from Late Carboniferous to Mid Permian);the inland depressed basin formation phase(from Late Permian to the Anisian Middle Triassic);the intra-cratonic bending depression and piggyback basin formation phase(from the Ladinian Middle Triassic to Late Triassic); the rift-subsidence basin formation phase(Early-Middle Jurassic);the rifted basin formation phase(from Late Jurassic to Early Cretaceous); the strike-slip basin formation phase(Late Cretaceous); the rift-subsidence basin formation phase(Paleogene) and the depression basin formation phase(from Neogene to Quaternary).The overthrust tectonic system in northern Qinling-Dabie orogenic belt in this area has the feather that it can be divided into subzones in the strike tendency and blocks in the dipping direction. which also can be divided into five episodes. LuoYi Basin and sags in the middle-northern of ZhouKou Depression were located in front of the North foremountain zone or foredeep zone,and XinYang-Heifei Basin were located on the median thrust sheet zone,which between the two thrust faults(NTH &STH).and point out that the Southern North-China Basin in Indosinian-Yanshanian is not foreland basin,but rift-subsidence basin.Based on the analysis of the tectonic-sedimentary evolution in the Southern North-China Basin,conditions of source rocks in Upper Paleozoic and reservoir-forming have been carryied on in systematic. Indicate that the exploration should give priority to gas and oil is subordinate. Lithology or tectonic- lithology trap is main exploration aim. There are five patterns of fine play zone have been found out: self-generating and self-preserving sandstone in-source assemblages;self-generating and self-preserving fracture-type limestone in-source assemblages;down-generating and up-preserving sandstone near-reservoir assemblages;up-generating and down-preserving fracture-type limestone near-reservoir assemblages;down-generating and up-preserving sandstone remote- source assemblages.