The Research Of Palaeozoic Thermal History And Its Oil-Gas Geological Significance In Zhoukou Depression

The Zhoukou depression is a part of Cainozoic Era superimposed basin which formed on the stabilize cratonic. The Paleozoic group experiences Indo-Chinese, Yanshan and the Himalayas tectonic movement with varying degrees of transformation. Nowadays (The distribution plane of thermal evolution between Zhoukou depression and neighbouring area paleozoic is different) , but the thermal evolution of Zhoukou depression's formation mechanism and process is not clear. In addition, The paleozoic group of Zhoukou depression have good conditions for hydrocarbon generation, but yet has not found the reservoir of the source of paleozoic source rocks. Therefore, the research for the paleozoic group of Zhoukou depression's thermal evolution history and geological significance of oil and gas has a certain scientific and practical significance. In my paper, I insist on the principle of "overall, dynamic, comprehensive" to analyse oil and gas basin and take the thermal evolution of Zhoukou depression and the paleozoic group of neighbouring area as a main line. We study the burial history of Paleozoic, the characteristic of the thermal evolution, stages of the thermal evolution's division, temperature characteristic for ancient, now ground and so on. We also dynamically simulate the thermal evolution history and hydrocarbon generation history at the Paleozoic area, and evaluate favorable hydrocarbon-generating area of Paleozoic group in Zhoukou depression. We mainly obtain the following several understandings:1. The evolution for the Paleozoic group of Zhoukou depression is divided into Triassic,Early-Middle Jurassic, Late Jurassic-Early Cretaceous, Late Cretaceous- Paleogene and Neogene-Quaternary. In Triassic period it is mainly regional subsidence, In Jurassic-Early Crataceous it become as difference evolution stage, In Cenozoic it become as fault depression stage.2. The average geothermal gradient is 2.44℃/100 m. The value of average heat flow is 48.4 mW/m~2 in Zhoukou depression. The geothermal field of studied area belongs to the transitional type between the hot basin in eastern and cold basin in western China. The controlling facors are the lithospheric thickness, structural characteristics, groundwater activities.3. The characteristics of overall thermal evolution distribution at the Zhoukou depression and the Paleozoic group of neighboring area is " North higher than south ". The space distribution of Paleozoic thermal evolution is very different in different areas. The Paleozoic experienced the late Jurassic-early cretaceous tectono-thermal event in north depression zone(such as Luyi bag), and reached to the highest stage of thermal evolution, and it's geothermal gradient reached to 5.3℃/100m. The formation background have relationship with the Tai-kang thermal structure. The central-southern part's thermal evolution degree is relatively lower than Luyi bag, its thermal evolution action mainly is buried-warming effect. Southern depression zone and most of central depression zone reach to the highest thermal evolution stage in late triassic, It's geothermal gradient reached to 3.6～3.9℃/100m. The Tanzhuang-Shenqiu Paleozoic bag reach to the highest thermal evolution stage in late cretaceous, and its geothermal gradient reached to 4.3℃/100m.4. Combining subsidence histroy of research area and the geothermal field, the paleozoic hydrocarbon generated histroy and termal evolution histroy have be simulated in Zhoukou area. We figured out that The Zhoukou depression have two type of hydrocarbon generated, one is early hydrocarbon generated and early, secondary hydrocarbon generated. Integrated the characteristic of hydrocarbon source rock, tectonic development history and termal evolution histroy, we valuated the Paleozoic generation as three degree. the most favorable zone of hydrocarbon generation are in east area of Tanzhuang-shenqiu bag. The more favorable zone of hydrocarbon generation are in southern area of Luyi bag, west area of Tanzhuang-shenqiu bag as well as middle-west of Niqiuji bag, and the source rocks in Xiangcheng bag have poor hydrocarbon generation potential.