Characteristic Research Of Sedimentary Facies And Hydrocarbon Source Rocks Of Key Sections In The North Margin Of Upper Yangtze

The Yangtze region, including Sichuan, most of Guizhou Province ,eastern Yunnan and western Hunan Province, is China's most developed regions of sedimentary rocks. Margin of the Yangtze across Sichuan, Shaanxi, Chongqing and along the border, is located in the Sichuan Basin, northeast, north east-west Qinling orogenic belt, west of Songpan - Ganzi orogenic belt and the North East to the Longmen Shan nappe, east To Daba North West - South East to arc nappe, south of slow deformation zone for the Sichuan Basin. Study area is located on the margin of the Yangtze, the regional tectonic Daba Mountains in northern Sichuan and Sichuan foreland basin between the slope of uplift, north Micangshan thrust uplift and wangcang South River tectonic zone, east, eastern Sichuan steep tectonic belt, south Yilong Pyeongchang flat belt. In this paper, the area of the Late Sinian Dengying 3 Siduan and Palaeozoic sedimentary profile 16 sedimentary facies and different times, different structural nature of the source rock strata a systematic sample, source rock characteristics. Major work, knowledge and results summarized as follows:1,Collection, and analysis of the Yangtze platform of a large number of data available, in this based on the margin of the Yangtze geological setting, sedimentary, tectonic, stratigraphic analysis and synthesis of order and conduct a re-understanding.2,Collection, collation, comparison of the upper margin of the Yangtze important regional Paleozoic strata and the study area.3,Paleozoic strata in the study area is a set of mainly carbonate strata, among them, absolute advantage in limestone, dolomite less. Limestone structure in accordance with its components and some special causes can be further divided into: Particles– micrite,Reef limestone,Turtle crack limestone,Nodular limestone,Gravity flow limestone,etc. Dolomite can be divided micritic dolomite and silty dolostone, according to grain size. Also exposed are clastic rocks.It can be further divided into conglomerates, sandstones, siltstone, clay (shale). Most cherts occur in the lower part of Lower Cambrian and Upper Permian, black, dark gray thin - mainly in the layer.4,Study area is mainly Cambrian continental shelf, platform depositional environment. Carbonate tidal-flat facies in Daba Mountain front for the next temple typical dam section; Open platform facies to section Micangshan front wangcang region represented; Platform margin slope facies Wanyuan in front of Daba mounta in profile to represent the source region. On the system Ordovician Wufeng Formation - Silurian system Longmaxi under the lower part of the land shed basin facies are sedimentary subfacies; Wufeng Late Ordovician carbonate platform of development before the main phase. Silurian to normal littoral and shallow marine clastic and carbonate rocks deposited mainly , the Silurian missing. Longmaxi (shuanghechang group ) is mainly deep water shelf or land shed basin, shallowing upward sedimentary.Rojak Ping group (Xujiaba group) is mainly shallow shelf and littoral facies. Permian sedimentary facies mainly include: coastal marsh facies sedimentary facies restricted platform, open platform, platform margin reef facies, carbonate ramp and basin phase.5,In combination with the source rocks are in the characteristics of a high - mature understanding and predecessors, this selection TOC content is 0.3% of mudstone, carbonate content of 0.2% TOC, as the lower limit of effective source rocks, hydrocarbon source rocks in the area that is under the limit. Thus obtained on the margin of the Yangtze effective source rocks are Lower Permian strata Maokou, Lower Silurian Longmaxi, Upper Ordovician Wufeng formation, Upper Ordovician Linxiang formation, Lower Cambrian Guo Jiaba formation, Lower Cambrian Shui Jingtuo formation.6,According to carbon isotope geochemistry of kerogen and kerogen maceral characteristics Mirroring comprehensive analysis, on the margin of the Yangtze main living hydrocarbon source rocks are relatively strong typeⅠ,Ⅱ1 type. Vitrinite reflectance, pyrolysis peak temperature Tmax, H / C atomic ratio and the color of kerogen indicate that source rocks of the region are at high - over mature stage.In the region to over-mature source rocks in the main hydrocarbon source rock, but did not reach Chen Jinping, who raised "Dead line of oil and gas production" Ro value of 3.0%, still has the ability to produce oil and gas.7,From the lithology, source rock organic matter abundance, organic matter type, maturity of organic matter and organic geochemical studies on the preliminary evaluation of source rocks. Lower Cambrian black shale and Lower Permian carbonate rocks in the vicinity of the Yangtze margin are of widespread, thick, high abundance of organic matter, organic matter type is good, the region's main source rock strata; Lower Silurian and Upper Ordovician black shale though much thickness, but the high abundance of organic matter in some areas there may be a favorable section of hydrocarbon source rocks; Upper Ordovician Linxiang group are not widely distributed, low abundance of organic matter, little hydrocarbon potential. Comprehensive evaluation that the Lower Cambrian and Lower Permian is the main source area strata; Lower Silurian and Upper Ordovician, there may be beneficial in some areas of hydrocarbon source rock section.8,Certain depositional environment of sediments can only have certain combinations of organic matter in these sediments is the material basis for the formation of oil and gas. Therefore, the innate distribution of source rocks is determined by characteristics of sedimentary facies. According to the study area of the Lower Cambrian, Upper Ordovician, Lower Silurian, Lower Permian four Paleozoic marine source rock studies, obtained in the study area five kinds of favorable hydrocarbon source rocks of sedimentary facies: Deep muddy continental shelf, deep shelf carbonate facies, deep silicon phosphorus basin with the Gulf lagoon, offshore basin swamp.