Analysis Of Oil Shale Characteristics And Depositional Environment Of The Jijuntun Formation Of Eocene In Fushun Basin

Oil shale is an important oil and gas alternative energy sources, the growing shortage of energy now, development and utilizationof oil shale has aroused widespread concern in the world. Before the study of oil shale was to refine shale oil and related products, but also as fuel for power generation, heating and transportation, in recent years research on oil shale is mainly focused on refining shale oil,extracting useful elements in ash of comprehensive utilization and resources evaluation,etc,but the following aspects such as oil shale formation environment, ore-forming mechanism were also less.On this background,the paper selecte Fushun basin as an anatomical regions ,which exposed well,and has obvious features,the author comprehensivly use of sedimentology,sequence stratigraphy, paleolimnology, palaeoclimatology,geochemistry, paleontology and other disciplines to carry out research ,reveale the internal relations of oil shale characteristics, formation environment , the ancient lake conditions and industrial index , discusse oil shale mineralization mechanism of fault basin.The research results was not only guidance and reference significance for the Fushun oil shale exploitation and research,but has an important role on oil shale ore-forming mechanism and resource predictionforthe other fault basin . It also provide a theoretical basis for oil shale resource evaluation analogy method.Fushun Basin is located insouthern of Fushun,covers the area of E124°03′30〞-124°16′28〞,N41°57′15〞-41°59′37〞,it's a Cenozoicsemi-depressed deposition Basin. The south fault control the thickness of oil shale and oil yiled, the more near the fault side ,the thicker of the thickness , the higher of oil yiled . Oil shale occurred in the middle and upper of Jijuntun Formation, the middle part is lean ore,the upper is rich ore. The color of oil shale is dark brown, light brown,dull, oxidatived oil shale is light red for iron,generally is splintery fracture or conchoidal fracture ,horizontal bedding is developed. Single layer thickness of Oil shale ranging from 70-190 m,the average oil yield of 5.85 percent ,the highest oil yield of rich ore is13%,it has high industrial value. Oil yield positively correlated with the calorific value and volatile , but negativly correlated with the bulk density and ash . The organic matter type of lean ore is mainly II1-II2,the organic matter type of lean ore is mainly I. After research of biological markers that organic matter source is rich,both lower hydrobiont and terrigenous higher plants ,but lower hydrobiont occupied a dominant .The vitrinite reflectance(Ro) of oil shale is from 0.41% to 0.56 %,Tmax (℃) value is from 429℃to 446℃. X-ray diffraction analysis,oil shale in the composition of clay minerals is mainly kaolinite,shows that oil shale is immature - low mature stage.The author comprehensivly use of geochemistry , sequence stratigraphy , paleolimnology, sedimentology, palaeoclimatology,paleontology on oil shale formation environment ,revealed the oil shale formed in the hot -humid climate, a fresh water lake of weak reduction -reduction conditions.Sr / Ba ratio,carbon-oxygen isotope and fossils showed that oil shale deposited in freshwater lake. The redox conditions of the oil shale formation was analyzed by elements of the ratio (V / V + Ni, Ni / Co, Ni / V and Cu / Zn), rare earth elements and biomarkers ,we found oil shale of Fushun formed in the weak reduction -reduction conditions,the reduction conditions of lean ore is weaker than rich ore. Based on pollen and plant fossils features, combining distribution of minerals and trace elements ratio, identified eocene ancient climate evolution: Early eocene is warm - humid climate; mid-Eocene is hot- humid climate; late Eocene is semi-dry and semi-humid;By Professor Liu Zhaojun (1994,1997,2002) for the scheme of four division of third-order sequence, identified the lowstand system tracts,transgressive system tract,high-stand system tract to resgressive system tract of third-order sequence in Jijuntun Formation.Used geochemical methods ( trace elements content , organic carbon content and kerogen type,etc.),combined with the rock outcrop characteristics and fossils and other signs dividing sedimentary facies .we proposed lean ore formed in transgressive system tract of semi-deep lake environment, rich ore formed in high-stand system tract of deep lake environment.The study shows that structural factors,the paleoclimate factors,sedimentary facies play a significant role in oil shale mineralization . Structural factors which control the distribution of oil shale,oil yield and thickness; the paleoclimate factors and sedimentary facies directly or indirectly affect the oil shale organic matter for production, import and save: hot -humid weather conditions, A lot of nutrients into the lake ,making a lot of algae flourish, the great lake productivity,for the formation of oil shale has provided sufficient organic matter;deep lake water was stability and could maintain a certain depth,terrestrial fragments injected into fewer,and to provide a stratified lake conditions,contribute to the preservation of organic matter. Revealed that adequate supply of organic matter,steady water delimitation and terrestrial fragments injected less into lake,theses were favorable conditions for ore-forming.