Institute of Exploration and Development, Jilin Oilfield Company, PetroChina, Songyuan 138000, Jilin, China

The reservoir characteristics of Lower Cretaceous Yingzuilazi Formation in Sankeyushu fault depression are systematically studied based on coring and outcrop data, combining casting thin sections, scanning electron microscope, mercury intrusion, nuclear magnetic and other testing methods. The results show that the Yingzuilazi Formation in Sankeyushu fault depression was deposited in volcanic barrier lake environment, with coexisting pyroclastic sedimentary rocks and volcanic lava reservoirs. The main reservoir space consists of primary residual pores, secondary dissolution pores and fractures, with porosity of 4%~10%, permeability of less than 0.2×10^-3μm², throat radius of 0.03~0.33 μm. The heterogeneity is strong and the reservoir is greatly influenced by sedimentary microfacies type, lithology, diagenesis and the degree of development of fracture.