Abstract: The Songnan gas field is mainly composed of compacted volcanic reservoir with low permeability. According to the gas testing results of the Yingcheng Formation, and other data such as porosity, permeability and impedance, a reservoir classification standard was established. Based on the observation of core, thin sections and SEM, developing patterns of vesicle and fissure in four types of reservoirs have been studied. In addition, potential target reservoirs have been described and evaluated. The reservoir in Songnan gas field can be divided into four types:Type I is high yield without fracturing operation. Type II is high yield after fracturing operation. Type III is no yields before fracturing operation. Type IV is dense layer. Vesicle-fissure pattern corresponding to each reservoir type has been described. Reservoir I presents primary vesicle-microfissure reservoir pattern. Reservoir II presents secondary vesicle-microfissure reservoir pattern. Reservoir III presents primary vesicle-tectonic fissure reservoir pattern. Reservoir IV presents secondary vesicle-tectonic fissure reservoir pattern. Potential evaluation indicated that the No.2 and No.3 targets in YS1 fault block have great potential for development. This study will benefit the analysis of exploiting potentialities, and the reservoir classification standard is more suitable for the actual production situation of dense volcanic reservoir in this area.

Key words: Songnan gas field, volcanic reservoir, classification &, evaluation, favorite targets, potential for exploitation