Abstract: The volcanic rocks of the Early Cretaceous Yingcheng Formation are the main reservoir rocks in the Qingshen gas field of the Songliao Basin. Reservoir space is classified as fissure and pore, the latter is premier and the former serves as main tunnels for fluid migration. There are 4 types of reservoir spaces, and the most common one is combined disoloved emposieu and micropore. By mercury penetration analyzing of volcanic samples, capillary pressure curves are on a scale from Ⅰ to Ⅴ. Volcanic breccias and breccias lava developing from volcanic conduit, vesicle rhyolith developing from intrafacies on top of effusion facies, and pyromeride or pearlite from inner zone intrafacies of intruded facies，are suggested to be the best reservoirs. Their sorting coefficient is from 0.3 to 2.6, coarse skewness， maximum pore throat’s radius is 4.9 μm, thus being of better reservoir’s physical properties. In all the ways, reservoir's pore structure of the region is featured by dominance of micropore throat, big proportion of pore and throat and wider distribution range. These reservoirs need commonly extensive fracture treatment so that commercial gas flows can be gained.

Key words: Songliao Basin, volcanic reservoir, micro-fabrics, feature parameter