Deposition characteristics and evolution of the Cretaceous system of Chepaizi area in Junggar basin

Using drilling,logging,well logging and seismic data,we analyzed the structure of the rock and paleontology,and researched sedimentary characteristics of Cretaceous in Chepaizi area.The results showed that the Cretaceous in the study area mainly developed fan delta and lake facies,and can be further divided into fan delta plain,fan delta front and shore shallow lake subfacies,and include overwater distributary channel,backswamp,subaqueous distributary channel,subaqueous interdistributary channel,delta front sheet sand,mud flat and beach bar microfaeies.The sedimentary background is shore shallow lake,the northwest is the uplift,and provides the clastic sediments,and gradually evolved into wide slope to the east and south,detritus mainly deposited on the slopes of the shore shallow lake.From the Qingshuihe formation to the Lianmuqin formation,the sedimentary range continuously expanded.Affected by the fluctuation of lake level,climate,sediment supply and other factors,the fan delta sand body is small,beach bar sand body develops extensively,these sand bodies close to the oil source sag,are favorable area for oil and gas accumulation,and easy to form the formation of reservoir,as should be important targets for oil and gas exploration.