Abstract: Based on the rock core observation,logging data, well drilling data and image logging data, the characteristics of fructures in Carboniferous volcanic reservoirs, at the zone 9, Kramay oilfield is studied. The result indicates: fractures in the volcanic reservoisr are well developed，they are mainly structural fractures formed in the tectonic movement, most of them are filled with some kinds of solid minerals, which impact fractures′ validity to oil accumulation and migration. There are reticulate and heterotropic fractures, most of them are small scale, main fracture direction is Northwestern, consistent with main structural direction. According to the characters and cause of formation, the fractures are classified comprehensively. By studying the relation of fractures and tectonic movement, it is recognized that there are 4 periods of fracturing, corresponding with the tectonic movement. Finally, the influencing factors of fracture developing are studied, and it is indicated that characters of rocks and structural locations are main factors influencing the fracture′ developing.

Key words: carboniferous reservoir, volcanic rock, fracture, characteristic, influencing factors