Abstract: Penglai 9-1 oilfield, which topped single structure discovery in one decade of China with proven geological reserves of 2.28×10⁸m³, was a large-scale compound oilfield discovered in Bohai sea area recently. Due to excellent source-reservoir-cap assemblage, oil reservoirs formed into an integrity reservoir,which distributed in clastic rock of Neogene and intrusive granites buried hill of Mesozoic and characterized by shallow burial depth, heavy oil quality, and huge reserve scale. Among the reserves, granites of shallow saddle accounts for 80 %. Affected by reservoir quality, reservoirs in the upper parts of granites formed stratiform-like reservoir model because of pore, fracture-pore type reservoir with good lateral continuity. Meanwhile, reservoirs in the middle-lower part of granites went with lithologic model due to facture, pore-facture type reservoirs with higher lateral heterogeneity. The discovery opened up a new field to exploration of buried hill, specified oil contribution of Shahejie Formation from southern part of Bodong depression and northern part of Miaoxi sub-sag, revealed the importance of passage system made up of active faults of long period and granites weathering crust to the oil accumulation, showed significant reference to exploration of Penglai 9-1 oilfield-like, especially granites buried hill of Mesozoic.