Research On Geochemistry Characteristic And Hydrocarbon Source Rock Evaluation Of Permian System In Southern Qilian Basin

Southern Qilian basin is located in the southern part of Qilian fold belt,the northern parts connect to the Middle Qilian block,the northwest part is cutted off by sinistral strike-slip Altyn Tagh fault,southwest adjacent to Qaidam basin,the Southeast is linked together with the West Qinling.The previous research of Southern Qilian area mainly focused on the Early Palaeozoic Era and the Cenozoic Era,but less on the Late Palaeozoic Era and Mesozoic Era,especially,the research level of Permian Period in this area is very poor.The paper mainly studies the deposition provenance, environment,and evaluates the hydrocarbon source rock through the method of geochemistry.the result can provide not only the useful information to the discussion of the tectonic setting and evolution of this area,but also the theoretical basis and base data to the further research of the marine facies of Permian system in Southern Qilian basin.The paper takes basin analysis as the guidance, with the basement on the existed geological research achievement, comprehensively uses region geological survey and geochemistry method,combines the outdoor survey with inside research,mainly studies the deposition provenance and environment of Southern Qilian basin,and also evaluates the hydrocarbon source rock,finally tries to find the relationship between the two sides of the study above.The research results indicate that:the marine facies and continental facies of the Permian system in Southern Qilian basin have the same provenance witch mainly is the metamorphic crystalline rock and granite in the Precambrian system that come from Middle Qilian and Longxi land mass.The deposition environment of the marine facies of Permian system is steady, the area is in a reductive,salinity-maderate,and humid shoreland environment.The hydrocarbon source rock in this area has already been at the high-over maturation stage, the organic matter type mainly is sapropelic-humic(â…¡2) and abundance is poor-medium.The hydrocarbon source rock keep a close relationship with the deposition environment,in general, the hydrocarbon source rock usually develope in humid,wet-hot,reductive,salinity-high and productivity-high environment.