Abstract: In order to clarify the development characteristics and main controlling factors of high-quality reservoirs in the Fourth Member of Dengying Formation in Penglai gas zones,based on the analysis of reservoir lithology and porosity-permeability properties,the main controlling factors of high-quality reservoir development are systematically studied and the reservoir deposition and formation model are established by drilling core,rock slice observation,logging and physical property test.The results show that the dominant reservoir rocks of the Fourth Member of Dengying Formation are algae concretion dolomite,algae stromatolite, and algae laminated dolomite.The main reservoir space is formed by dissolution pores and microfractures.The diameter of dissolution pores decreases toward the bottom of the reservoir, and three types of reservoirs are developed:matrix pores, dissolution pores,and dissolution pore-microfractures.The dissolution pore-microfracture type is concentrated in the upper part of the Fourth Member of Dengying Formation;the dissolution pore type is mainly developed in the middle and upper part;the matrix pore type is concentrated in the lower part.The reservoir as a whole has the characteristics of low porosity and ultra-low permeability.Vertically, the mound base and mound core are developed as high-quality reservoir layers.Supergene freshwater dissolution,buried hydrothermal dissolution and hydrocarbon migration organic acid dissolution in Tongwanian jointly promote the development of dominant reservoirs and control the intensity and mode of dissolution.The fault can provide a channel for infiltration and migration of fluids, connect isolated pores,accelerate the development of karstification, and control the intensity of karstification and the spatial distribution of dissolution pores.Based on the characteristics of reservoir space and vertical distribution,starting from the genetic mechanism,three types of reservoir development models of vertical and horizontal superimposed seepage fracture solution and horizontal hyporheic layer solution of the surface mixed karst body of the Fourth Member of Dengying Formation in Penglai gas zones are established.The results have certain reference significance for the efficient development of the Fourth Member of Dengying Formation in Penglai gas zones.

Key words: algal dolomite, mound-beach body, karstification, developmental model, Fourth Member of Dengying Formation, Penglai gas zone