The Research Of Upper Paleozoic Thermodynamics Features In Northeast China

Late Paleozoic marine strata developed in the Northeastern of China. In the Early and Late Carboniferous and Permian marine strata developed widely and great thickness in the Songliao, Erlian basins. In the Early Carboniferous strata appeared many of bioclastic limestone and marble of bioclastic limestone in the southern of Songliao basin basin, containing a large number of biological debris. In the area southwest developed no deterioration or the low level of deterioration Upper Paleozoic carbonate rock. In the basal Carboniferous Basin - Permian gas reservoir and a number of oil and gas has been discovered by Jilin oilfields. In a conclusion,Late Paleozoic strata still have the ability of hydrocarbon in the northeast area.Paleozoic strata develop in the northeast region and the thermal evolution level of the Northeast region is a key issue about whether the Paleozoic hydrocarbon and exploration have potential or not. Our concern is: Northeast region characteristic of thermal field since Upper Paleozoic; erosion calculation in key areas of basin,ancient depositional burial history and thermal history reconstruction.We will study the tectonic fault zone, the distribution characteristics of micro-plate,since Late Paleozoic volcanic activity, development of times and distribution, contacting the regional heat flow field changes, which of all is to help understand the effect from thermodynamic background.Regional thermal field: the correspondence of the Moho surface and the overlying tectonic units shows that the upper mantle asthenosphere magma intrusion which generates the convection of mantle material, is the main driving force of plate movement; the Moho-discontinuity that have a difference depth in different zones of Northeast region will have significant effects on the thermodynamic characteristics of the Paleozoic crust.Magmatic activities: after the Hercynian epoch magmatic activity, especially in the Mesozoic, including Indo-Chinese and Yanshanian epoch,has some effect on the thermal field of the Early Paleozoic. Among them, the Indo-Chinese epoch magmatic rocks are mainly distributed in Heilongjiang Yichun - Shangzhi and the eastern region of Jilin Province. The magmatic rocks from Yanshanian epoch are intensive, more times than others and the biggest scope and scale of magmatic activity since Paleozoic. Especially in the eastern of Songliao basin and Daxinganling formed a large area of igneous rock distribution,which have important implications on the thermal evolution of the Paleozoic strata. Finally, Himalayan epoch magmatic activity is relatively small, volcanic rocks are mainly distributed in the eastern of Northeast China inculding Changbai Mountains and the Dunmi fault zone, Xilinhot - Chifeng area in the central part of Erlian Basin, partial located in Nenjiang- Wudalianchi area of the northern part of Northeast China.Thermal field characteristics of the Upper Paleozoic:the Upper Paleozoic thermodynamic characteristics present is the present temperature of high value of Songliao basin is distributed mainly in parallel with the north-northeast to the central belt of the basin, in which the maximum current temperature up to above 220℃. To the basin margins, ground temperature decreases radually the Upper Paleozoic thermodynamic distribution characteristics present is apparent under the control of the image depth of the Moho surface.In the middle of the basin, the Moho surface depth is shallower, and heat flow values is higher,so deeply buried of the Paleozoic strata present a higher temperature in the middle of the basin.Upper Mesozoic thermal field characteristics is the top of Upper Palaeozoic strata in the central basin area is paleotemperature maximum area, the direction to the edge of basin, the ancient temperature decreases radually. Most of the paleotemperature is bove 250℃and the adjacent areas of Songliao basin is less than 250℃, while the central region come up to 280℃and more. The maturity of organic material has reached in the stage of generation of the high maturity dry gas,while most areas in central basin have entered a post mature stage which has a little potential for hydrocarbon.The Upper Paleozoic thermal history analysis: According to Yanming Tong, "using the method of vitrinite reflectance recovering the thickness of eroded strata", which has a estimated respectively about the thickness of eroded strata from the Paleozoic-Cretaceous unconformity and Shahezi—Yingcheng formation through Four-deep 1 well in the northern basin.Conclusion, in the northern basin,after Carboniferous-Permian period, the structure uplift caused a denudation about 1436m, while after Shahezi formation, the uplift of Yingcheng period caused a denudation about 832m.Thermal history analysis: By the test data of vitrinite reflectance from Four-deep 1 well which drilled Paleozoic,we can calculate the biggest paleotemperature which different layers has suffered and obtain geothermal gradient is 5.3℃/ 100m through the graphical improvements invented by Karweil about maturity of sedimentary organic matter, temperature and heating time.Application of TTI index about the combined effect of time -temperature we analyse thermal history of Four-deep 1 well in Paleozoic,It began to have oil generation about 231Ma (equivalent to the late Middle Triassic), started natural gas from 212Ma (equivalent to the Late Triassic); the end of oil generation was 182Ma (equivalent to early Jurassic), stopped natural gas by 165Ma (equivalent to the mid-Jurassic); started secondary hydrocarbon generation 100Ma(equivalent to the late Early Cretaceous Quantou development of), the end of secondary hydrocarbon generation was 84Ma (equivalent to the mid-late Yaojia formation of the Late Cretaceous). Secondary hydrocarbon might have an important influence on the filling of stratigraphic hydrocarbon reservoir before the Yaojia stratigraphic. The Late Paleozoic strata of the Songliao basin presenced two or three times of hydrocarbon in the Early and Middle Cretaceous.