Abstract: The diagenesis of volcanic rocks in Yingcheng Formation was classified as the early diagenesis and late diagenesis based on the observation of outcrop, well core, thin section and the analysis with scanning electric microscope. The early diagenesis includes corrosion, vaporization of volatile matter, isovolumetric condensing crystallization, pene-contemporaneous hydrothermal precipitation and crystallization, fusion, condensing constriction, differentiation condensing crystallization and the early impaction-cementation. The late diagenesis includes filling, devitrification, metasomatism, mechanical impaction and pressure solution, cementation and dissolution. The early diagenesis mainly influences the development of primary pore and the late diagenesis mainly influences the development of secondary pores. The pene-contemporaneous hydrothermal precipitation and crystallization, the early impaction-cementation, the filling, the mechanical impaction and pressure solution and cementation will harm the porosity and permeability of volcanic reservoir. The porosity and permeability will be improved after the vaporization of volatile matter, the isovolumetric condensing crystallization, the condensing constriction and dissolution.

Key words: Songliao Basin, Yingcheng Formation, volcanic reservoir, diagenesis, porosity and permeability