Geochemical Characteristics Of Lowr Cretaceous Source Rocks In Taricuo Region,Tibet

Taricuo Region is an important development area of marine sedimentary reservoirs in Cuoqin basin,and the lower Cretaceous strata in the area are considered as important source rocks in Cuoqin basin.Based on the theory of sedimentary geology and organic geochemistry,this paper has carried out field geological survey,profile measurement,and analysis of indoor source rocks in the Lower Cretaceous(including Langshan Formation and Donnie Formation)The sedimentary characteristics and organic geochemical characteristics of the two sets of source rock(Langshan Formation and Donnie Formation)in the Cretaceous are mainly obtained:The sedimentary characteristics and lithofacies of the study area were determined by using the measured data of the field profile.The main sedimentary types of the Lower Cretaceous in the Cheking area were a set of shallow carbonate carbonate facies sediments,which were rich in biological The Donnie Formation is a set of terrigenous clastic rocks and carbonate rocks that are mainly developed in the delta facies.According to the data analysis of organic geochemical samples of hydrocarbon source rock in the study area,mainly through the organic carbon in the lower Cretaceous source rocks(TOC),chloroform bitumen "A",the vitrinite reflectance(Ro)and pyrolysis peak temperature(Tmax),kerogen maceral,carbon isotope composition and detection research the content of machine elements detection of data processing and analysis,results showed that Langshan formation carbonate rocks about 90% of the sample has reached the level of source rocks,the overall display Duoni formation is poor source rock and has not reached the standard of hydrocarbon source rocks.The organic matter types of the lower Cretaceous hydrocarbon source layer are ?2-?: the organic matter type in the Langshan Formation is mainly ?2 type,and the Doney group is?2-?type.The degree of thermal evolution is in the mature and high mature stage,and the maturation stage of the Langshan Formation is higher than that of the Doni Formation..It is concluded that the hydrocarbon generation potential of Langshan Formation is better than that of Doni Formation.The biosafety compounds of the Lower Cretaceous source rocks are comprehensively analyzed.The parent material of the Langshan Formation is mainly composed of lower aquatic organisms,which is the salt water reduction environment with deep water body.Aquatic organisms,but also part of the contribution of higher plants,formed in the water deep,low salinity brackish water environment.The maturity of the two groups has reached a mature boundary.On the other hand,the maturity of the source rocks of the Langshan Formation is higher than that of the Dorni Formation source rocks.