The typical lateral accretion packages develop in the second member of Yinggehai Formation. There are large unexploited reserves with large risks in development in such areas. Based on the analysis of the seismic，well logging and mud logging data，the distribution characteristics and formation mechanism of the lateral accretion packages were studied. The study result shows that the lateral accretion packages in gas groupⅢa formed when the water flowed to the south of gas formation along the low position area and migrated laterally due to the underwater terrain highland in the period of deposition.The lateral accretion packages in gas groupⅡa formed due to the lateral migration of muddy channel，which can be classified into low bending packages and high bending packages in the depositional period. The high bending lateral accretion packages distribute in the terminal channel and the low bending packages distribute in the upstream channel. Combined with the analysis of drilling and seismic data，it is found that inner sandbodies in the packages has poor gas bearing property，and the top sand bodies are connected to some extent. The top of the lateral accretion packages should be considered when a well is deployed.