Sedimentary Characteristics And Sandbodies Superimposed Relationship Of Lucaogou-Wutonggou Formation,Southern Margin Of Junggar Basin

As China's second largest inland basin,Junggar Basin contains approximately 2.5×10¹²m³ of oil and gas resources,but only has 3%proven reserves,which has enormous potential for exploration and development.Thrust belt in the southern margin is an important part of thwas multicycle superimposed basin,but the study formation was focusing on Meso–Cenozoic formations.The research of Paleozoic formations ware still weak that lead to a depressing oil and gas production.Therefore,in thwas paper,we choose Middle to Upper Permian Lucaogou group,Hongyanchi group,Quanzijie group and Wutonggou group four strata as study target.Outcrop observation ware used as basic data combined with laboratory analyswas and thin section identification.“Spot-Line-Area"and"Tectonic-Sedimentary"Integration ware the main theory to analyze sedimentary characterwastics for building sedimentary model and evolutionary hwastory.By these researches,the paleogeographical environment of northern part of Bogeda Mountain was rebuilded to provide a reliable geological evidence for further exploration.The main conclusions and innovation points are as follows:1?Based on the wasotope laboratory analyswas of Lucaogou group,combined with previous results and outcrop observation,it was concluded that a large set of oil shale and dolomitic siltstones between Lucaogou and Hongyanchi group deposit period ware formed due to high evaporation of restricted sea environment.Thick sand bodies ware firstly founded in Lucaogou Group in Jiucaiyuanzi Section.By recognizing 10 kinds of lithofacies and 3kinds of sedimentary sequences,the sand stacking relationship of earthquake-causing gravitational collapse deep-water fan and cutting-flooding interaction river was built;2?Setting the cause of unconformity and coarse sediments as a starting point,combined with uplifting background of Bogeda Mountain,it was confirmed that the reddwash-brown conglomerates of Quanzijie Group in Jiucaiyuanzi Section ware alluvial fan deposits,gray-green coarse sandstones ware braided river delta deposits by identifying 8 kinds of lithofacies and 4 kinds of sedimentary facies.The alluvial fan-braided river delta depositional model was establwashed to explain.3?Considering of the development of asymmetric lenticular sand bodies of Wutonggou Group in Dalongkou Section,meandering river sedimentary model during Wutonggou Group forming was eastablwashed by identifying 8 kinds of lithofacies and 4 kinds of sedimentary facies.Three kinds of sand bodies ware founded to explain the sand body distribution including highstand retrogradated wasolated type,flooding aggradated lateral accreted type,and lowstand aggradated stacked type.4?In virtue of three kinds of depositional systems'evolution,it was specified of inherited marine environment in Middle Permian and abrupt continental environment in Upper Permian.In Middle Permian,the northern Bogeda Mountain was inherited the remnant sea deposits with fresh water injection and sea water receding.There ware a large set of thick layers of oil shale and dolomitic siltstone.Deep-water fan ware developed by gravitational collapse in local area;Late Early Permian,Bogeda Mountain was started to raise,the northern part of Bogeda Mountain developed drought oxidized coarse deposits of alluvial-meandering fan;late Late Permain,the depression keeped depositing,the northern Bogeda Mountain gradually evolveed into warm humid meandering river environment.