Abstract:  Thin sandstone and mudstone interlayers with low permeability were identified and classified in the Bashijiqike Formation of the Dalaoba Condensate Gas Field based on well logging data. Standards for well logging identification were established to describe the spatial distribution features of interlayers. Gas pools in the Bashijiqike Formation were controlled by sedimentary environment. In the southwest, mudstone interlayers of type Ⅰ₂ developed, characterized by small thickness and poor continuity. In the east, physical interlayers of type Ⅱ₂ developed, characterized by big thickness and stable distribution. According to MDT logging pressure data, production well water breakthrough time and gas/ water inversion relationship, the sealing capacity of interlayers in the Bashijiqike Formation was judged. Both of the two types of interlayers were proved capable for sealing. The gas pools were condensate ones with boundary water rather than bottom water.