1. College of Earth Sciences, Jilin University, Changchun 130061, China;
2. Key Laboratory for Evolution of Past Life and Environment in Northeast Asia(Jilin University), Ministry of Education, Changchun 130026, China;
3. Exploration and Development Research Institute, Liaohe Oilfield Company, CNPC, Panjin 124010, Liaoning, China

Based on the observation and description of drilling cores and thin sections, the authors explored the formation mechanism,development characteristics and controlling factors of dissolution pores in the reservoirs through casting thin section analysis, scanning electron microscope analysis and surface porosity measurement combined with oil-gas-bearing information from drilling data. The results show that 14 sub-types of 4 basic rock types are developed in the pyroclastic rocks in the study area. The tuff-type reservoirs have the highest facial porosity (5.6%~9.5%), and the effective pores in the reservoirs are mainly secondary dissolution pores (averaging 89.6% of the total pores). 6 sub-types of 3 types of dissolution pores were identified. Different rock fabrics leads to differential dissolution of rock compositions. The dissolution components mainly consist of interstitial materials (zeolite, calcite) and crystal fragment, and followed by debris and breccia. Early cementing is favorable for the preservation of primary intergranular pore space and is an important prerequisite for the formation of secondary dissolution pores. Tectonic fractures enhance pore connectivity. Organic acids produced during the hydrocarbon generation of the overlying source rocks of the Jiufotang Formation provide a source of dissolution fluid. Under the eruptive interface is the favorable reservoir development area.