Abstract: The Permian coalformed gas reservoir in the Suligemiao area is characterized by heterogeneity, secondary pore and abundant nonstable tuff fillings. The simulative experiment shows that tuff fillings is obviously dissolved under the acid conditions. And with higher acid concentration, the dissolving ability of tuff fillings is intensive. However, the simulative experiment reflects only the dissolution of tuff fillings under open water environment. But under enclosed burial water environment, because the dissolvable products can not be discharged in time and acid becomes weaker, the dissolution of tuff fillings can not be processed fully and tuff fillings is preserved well. The secondary pores induced by dissolution of tuff fillings may improve the storage capacity of reservoir, but they also destroy the interconnection of reservoir to some extent. This is just the reason why the Permian coalformed gas reservoir under study is heterogeneous and is of very low permeability.

Key words: Suligemiao area, coalformed gas reservoir, tuff fillings, dissolution, secondary pore