Sedimentary Environment Analysis And Source Rock Evaluation Of The Middle- Upper Triassic In Jimsar Area, Xinjiang

Junggar Basin is located in northern China's Xinjiang, a gigantic basin which contains oil and gas deposition and it is surrounded by folded mountains, there have been rich oil and gas. In the Junggar Basin, there are been developing many sets of hydrocarbon source rocks, and the study work of people was concentrated on the source rock of Permian system Jurassic and Cretaceous of basin, and the study of the Triassic hydrocarbon source rocks in the Junggar Basin were relatively few. Most of scholars took the theories of sedimentary and sequence stratigraphy as guidances, combine data such as seismic, logging and core with Triassic hydrocarbon source rocks in the Junggar Basin to study, and have obtained some understanding. The studies of sedimentary environment and sedimentary facies also took stratigraphy Lithological's characteristics as a reference, the study of using geochemical characteristics of the depositional environment is to study the sedimentary environment is weak.This paper was based on the field geological survey and combined with the sedimentation method, through collected examples in the research area,to test and analyzed the trace elements, rare earth elements and organic geochemistry, studied sedimentary characteristics, sedimentary environment in the Middle-Upper Triassic of Jimsar area, Junggar Basin,Sedimentary environment, and evaluated the Middle-Upper Triassic hydrocarbon source rocks, which provided the basic data for the further study of the Triassic hydrocarbon source rocks and the evaluation of oil and gas resources in the Junggar Basin.The study results demonstrated that the Karamay Formation in the Jimsar area of the Junggar Basin is mainly formed by a delta-shore shallow lake sedimentary system composed of medium-fine sandstone and the former delta mudstone in the delta front subterranean diversion channel.The Huangshanjie Formation is mainly thin limestone and mudstone, the total water body of the Karamay Formation to the Haojiagou Formation is characterized by a shallow depth and a shallow change. The main material of the sediments in the study area is mainly derived from the upper crust.The source material of the source area is dominated by the felsic rock, and the source area is mainly characterized by the continental island arc. It shows that the middle and late Triassic in the study area are in the slow sedimentation state, There is no strong structural change in the structural background. In the Middle and Upper Triassic, the paleoclimatic climate changes from humid to arid, and the paleoenvironment is a weak return to the freshwater - brackish water, which is conducive to the preservation of organic matter. The organic matter abundance in the Karamay group and the Huangshanjie Formation in the Jimsar area is poor - medium source rock grade, the organic matter type is ?2 and ?, and the organic matter is in the mature stage of mature maturity. Based on the previous data, it is considered that the source rocks of Karamay and Huangshanjie Formation in the study area have certain hydrocarbon generation potential.