Abstract: Baka gas field Located in the northern sag of Tuha basin,lower Jurassic tight sandstone reservoir of Badaowan formation is an important gas-producing reservoir.Based on whole exploration and development of Baka gas field,in combination with well logging,mud logging and core data,the analytical research on color and lithology of sedimentary rocks,of sedimentary structure and logging facies has been carried out.The results indicate the main sedimentary facies of lower Jurassic Badaowan formation is braided river delta facies,mainly with braided river delta front subfacies,main-ly developing five kinds of sedimentary microfacies,underwater distributary channel,interchannel,mouth bar,braided river prodelta mudflat and marsh.On the basis of wellto-well profile facies study,sedimentary facies plane distribution characteristics of typical small layers has been described and the sedimentary facies model of Badaowan formation has been established finally.