Abstract:With proven reserves over 100 billion cubic meters, gas column height over 1000m and buried depth over 4000 m, Bozhong 19-6 gas field is the largest deep-buried condensate gas field recently discovered in Bohai Bay Basin, whose reservoir is large while with strong heterogeneous. Based on the 3D seismic, drilling, well logging and thin section data, the characteristics of the buried rock reservoir are clarified, and the main controlling factors of the formation of high-quality reservoir are discussed. The results show that the bedrock reservoirs is mainly composed of metamorphic granite, and the storage space is mainly structural fractures, while the dissolved pores along fractures and the crushed inter-granular holes are developed as well, resulting an average porosity of 5% and an average permeability of 6.48×10-3 μm2. Lithology, tectonic activity and weathering jointly control the formation of large-scale reservoirs: (1) 90% of the rocks in the study area are metamorphic granites with high content of feldspar minerals and high brittleness, which provide the material basis for the formation of fractures; (2) The intense compression during Indosinian period provides external power for the formation of large-scale fractures, which is the most critical factor for the development of large-scale reservoirs. The heterogeneity of reservoir plane distribution is response for the different degree of fracture development in different structural locations; (3) Long-term weathering has further improved the reservoir properties within 300 m of the upper part of the buried hill, which controlling the vertical heterogeneity of the buried hill. Those understandings have important reference significance for the future exploration of bedrock buried hill in rifting basins.