The Organic Geochemical Characteristics Of Middle Permian Lucaogou Formation Oil Shale In The Southern Edge Of Junggar Basin

As an important unconventional resource, oil shale has received wide attention because of the rising intense of China’s yearly dependence on foreign oil and gas resources. China is rich in oil shale resources and the proved oil shale resources of Junggar Basin has reached 4×108t. Based on the previous researches and field observation and indoor analysis, this paper evaluates the abundance, type and maturity of organic matter, and discusses the oil shale’s parent material source, depositional environment, causes and hydrocarbon potential in Lucaogou Formation by combining the stratigraphic correlation, sedimentary environment and petrologic feature analysis and the Rock-Eval analysis and gas chromatography- mass spectrometry analysis. This thesis could provide a basis for the exploration and development of oil shale in the study area.The study area of Junggar Basin is a kind of inland lake with freshwater and occasional brackish intervention in the sedimentary period of forming Milldle Permian Lucaogou Formation. The major sedimentary facies are shore lacustrine, shallow lacustrine, and semi-deep to deep lake.Among Rock-Eval analysis parameters of oil shale, mean TOC and mean potential of generating hydrocarbon(S1+S2) are 8.68% and 40.81mg/g respectively, indicating that the oil shale is dominated by medium grade. The hydrogen index, parent material type and degradation rate reflect its good organic matter type, mainly II1 Kerogen. The average maximum pyrolysis peak temperature(Tmax) is read 439℃, implying the poor maturity of organic matters. Organic matters are mainly in the evolution stage from low-maturity to maturity. Rock-Eval analysis parameters show that oil shale of Lucaogou Formation enjoys great potential of generating hydrocarbon.The biomarker parameters of Oil shale extracts of m(∑n C21-)/m(∑n C22+), m(Pr)/m(n C17)-m(Ph)/m(n C18) ratio diagram and C27-C28-C29 sterane triangular relationship diagram show that the oil shale was forming in weak reduction- reducing environment, the type of organic matter is mainly humic- sapropelic, and the hydrocarbon precursor mainly from algae and other lower aquatic organisms.Oil shale of Lugoucao Formation is in the evolution stage from low-maturity to maturity. This can be seen from m(Ts)/m(Tm), C3117α-homophopane m[22S/(22S+22R)], m(moretane)/ m(hopane), C29 gonane ββ/(ββ+αα) and αααC29 gonane 20S/(20S+20R).In this study area, shallow depth of burial, stable seam distribution, abundant amount of resources and large hydrocarbon potential make the development prospects be good. Oil shale of Middle Permian from Lucaogou Formation in the southern edge of Junggar Basin is suitable to exploit by remote mining method with open pit mining and dry distillation on the ground making shale oil.