Abstract: Based on core observation, thinsection analysis, physical property testing, fracture statistics, fluid inclusions analysis and fracture fractal research, it is concluded that there are four types of metamorphic rocks in the Archean Ciyutuo buried hill. Biotite feldspar gneiss is the main type of reservoir rock with mostlydeveloped fractures; the fractures in biotite potassic feldspar gneiss were less developed while altered lamprophyre and biotie hornblendite granulite could not serve as reservoir rocks. The main reservoir spaces in Archean are mainly tensional, steeply dipped fractures oriented in NE and NW directions and microcracks formed in the middle or the Late Mesozoic. Parts of tension-shear fractures were formed in the Late Paleogene Period. Small and micro fractures are the most developed fractures in the buried hill reservoir, whose width and areal porosity are positively related. The main controlling factors on fracture development in the Archeozoic reservoir of Ciyutuo buried hill involve the lithology, fault, depth, weathering, dissolution, magmatic intrusion, fissure assemblages and so on.

Key words: fracture, reservoir character, Archeozoic, controlling factor, Ciyutuo buried hill, Liaohe