Studying Of Stratigraphic Rocks, Lithofacies Palaeogeographical And Source Rock Of Carbon-Permain In The Central And Southern Xing'an Range

On the basis of lots of field investigation, region data analysis and previous researches, this article is mainly upheld by the theory of sedimentology, using the firsthand quantitative information which was obtained from the measured sections. And it was also based on the analysis of paleontology, petrology and sedimentary facies, Combined with the geochemical analysis of the source rock to predict the oil and gas prospect zone. The main cognitions and conclusions of this thesis are as follows:1,According to the stratigraphic subregion and sedimentary type, it initially established 4 carboniferous-permian stratigraphic columns; meanwhile, the stratigraphic column in Aohan Qi of Chifeng city represents the stable deposits of the Northern China Block; the stratigraphic column in West Ujimqin and Linxi county represents the relatively stable intermediate massif and deposits after plate closed; the stratigraphic column in Ke'erqin(Horqin) Youyi Qianqi represents the activity deposits of the ocean trough; the stratigraphic column in Jalaid Qi represents the stable deposits of the southern Siberia plate.2,According to the study of key fossils, it established 3 biological stratigraphic sequences based on the fusulinid, meanwhile, the stratigraphic framework of the region was roughly established comparing with the domestic and foreign strata to determine the stratigraphic age. Through the system of previous fossil acquisition, the new understanding of strata contrast are as follows:the fusulinid was first discovered in Aohan Qi, such as Eostaffella sp, Pseudostaffella and Profusulinella et al, which provides an important paleontology basis for the stratigraphic age and biological stratigraphic division and tectonic study, among which, a fusulinid combination in the early Carboniferous and two fusulinid combinations in the later Carboniferous has established, it is conducted that the time of the Northern China Block and Siberia plate close should be after Carboniferous; Four fossil combinations has established for Amushan Formation, which clear the sedimentary of the Xiaodushanzi Period to Longlin Period. The appearance of the Pseudoschwagerina—Sphaeroschwagerina combination is the beginning of the Permian. There are 2 fusulinid zones and 2 coral zones and 2 brachiopods in the Middle Permian. Through the contrast of the regional paleontology, it conducted that the Hinggan-Inner Mongolia trough developped from the Inner Mongolia to the central Jilin. The conchostracans was first discovered in Linxi Formation, such as Palaeolimnadia sp., Huanghestheria sp et al. The Huanghestheria—Cornia—Pemphicyclus zone was established and the Lixi Formation was divided into six lithologic sections. Taohaiyingzi Formation was equivalent to the fourth section of Linxi Formation and Lu D1 well to the fifth section. It is speculated that the regression begun from west to east, seawater allwithdrew from the Inner Mongolia and remained in central Jilin.3,Many Late Paleozoic reefs have been discovered recently in Hinggan-Inner Mongolia area. There reefs are in different places and different positions, which are Baijiadian Formation, Benbatu Formation in West Ujimqin, Amushan Formation in West Ujimqin and Sijiashan-Liutiaogou Formation.. These reefs obviously possess broad scopes, distinctive features and developed reef-facies. They contained five reef-building communities and were constructed in four periods. Reefs with Colonial Coral-alga Combined Frames have been mainly discovered at Yangjiazhangzi and Jiadaogou of the Aohan Qi; Reefs with branchy Coral-Crinoid Combined Frames are mainly found at West Ujimqin; Reefs with bryozoan Frames are discovered in the Jalaid Qi. Strata of each reef-facies have a big thickness and contain rich asphalt remains. Overlapping and heteropic layers are constituted by huge thicknesses of dark oil-gas origin-rocks. Evidences prove that the working area has a excellent perspective of oil-gas exploration.4,Based on 20 measured and observed outcrop sections, the rock types and sedimentary environments of the Carbon-Permian in the Central and Southern Grate Xing'an Ranges are studied, and the sedimentary model is recognized. It also identify Marine sedimentary environments in Later Carbonferious-Middle Permian. The platform is developped in the Marine sedimentary. The platform are divided into clastic rock platform and carbonate platform. The clastic rock platform are further divided into coarse clastic rock platform, shallow-water fine clastic rock platform and deep-water fine clastic rock platform. Carbonate platform can be divided into the ford, reef and open platform. It also identify slope sedimentary environments which representative deep-water basin. There are primarily slow slope in this area. Lacustrine facies are almost in Later Permian, which are divided into shore-shallow lacustrine and semi-deep lake facies. The semi-deep lake mudstone are developping in Linxin-Suolun area. The distribution of lake mudstone are spread under the Songliao Basin in NE-WS. As the result of dark mudstone can be good hydrocarbon source rocks, this formation can be the target zone for the future oil and gas exploration.5,It initially identified that the strata rock in study area is mainly normal sedimentary rocks, continental clastic rocks, carbonate and pyroclastic rocks. The preliminary investigation indicates that it exists four source rock layers from carbonic to Permian in the area, from upper to lower including: Upper Permian, middle Permian, Upper carbonic-lower Permian and lower carboni. Among them, the Upper Permian (Linxi formation) and middle Permian (Wujiatun formation) spread widely in the area, the max monolayer thickness of the black muddy rock from which gets to several hundred meters and the accumulated thickness from several hundred meters to several kilometers. The organic carbonate under 0.6% for Linxi Formation and Wujiatun Formation are 51.20% -95.8% and 88.2% -92.3% differentially, 0.6% -0.91% and 0.78% -1.01% on average differentially; The content of sapropelitci group in Wujiatun Formation is about 60% , so the type of organic is typeⅡ2. The content of sapropelitci group in other Formation is under 50% , so the type of organic is typeⅢ. The Ro of Linxi Formation and Wujiatun Formation is 1.3% -2.0% and 1.0% -2.0% differentially, so the mudstone was high mature-over mature. The main organic geochemical indexes (the organic carbonate, the maturity and the type of kerogen) reflect the source rock from the two formations gets the rank of middle to good and has the potential of generating high mature gas, condensate gas and mature medium oil. In summary, the two formations are the main generating hydrocarbon layers in the Carbonate-Permian of the Songliao and peripheral area. In addition with the reservoir including reef flat limestone and the detrital sandstone in some formations of this area, they form the Paleo-source/Paleo-reservoir Typed reservoirs, which shows the good prospect of oil and gas resource.The Later Paleozoic (Carbon-Permian) strata of this region are well developped with very thick and dark mudstone and carbonate. The main part of the Later paleozoic atrata did not undergo regional metamorphism. Oil-gas signs were discovered in some horizons of these strata. Thus, the Late Paleozoic marine strata in the Northeast China would possess great potential in oil-gas resources, being an important new layer for oil-gas exploration in the near future.