Abstract: The He8 Formation develops a set of excellent accumulation conditions,and is an important succeeding layer in the Jingbian gas pools.But the sandstone is tight,and its physical properties are not good.According to study on the characteristics of petrology,sedimentary microfacies and diagenesis,and so on,the following under-standings were obtained.The He8 Formation is low porosity and ultra-low permeability reservoir.The secondary intergranular pores are the main pore space.And the pore texture is not preferable.The distribution of reservoir is controlled by the deposition,but the deferent of physical properties is not remarkable in varies sedimentary microfacies.And mechanical compaction is a main factor which reduced the porosity in the He8 Formation.The kaolinite and chlorite had dual contribution to porosity,and the dissolution of aluminosilicate and carbonate is the controlling factor for high-quality reservoir development.