Abstract:The reservoir of Xujiahe formation, lying in the central part Yuanba area, belongs to low porosity-low permeability reservoir,and the fractures in this area have important influence on the accumulation and productivity of gas. Based on the core observation, field investigation and well log interpretation, the development characteristics and controlling factors of fractures are studied systematically,according to the regional tectonic evolution. The results shows that there are tectonic fractures, diagenetic fractures and drilling-induced fractures etc. high-angle shear fractures and low-angle shear fractures caused by tectonic are most developed, which are the key types of factures. The main orientation of fractures lies on NW(290°±10°)and NE(75°±10°). Fractures in this area are poorly filled and are better in petrophysical property. The influencing factors of the fractures development mainly include rock types, rock stratum and the tectonic, etc. The development degree of fractures is different with different lithology; with the increase of layer thickness, the fracture spacing is bigger and the fracture density reduces. The development degree of fractures is sharply decreased. There is a linear relationship between the fracture and he tectonic position. With the distance more and more far away from the faults, the fracture density has a decline trend and the development degree of fractures is also sharply decreased. The comprehensive prediction results of fractures show that the developed zone of fractures is located in both sides of large-scale fault zones, including mainly YL1-YL2(excludingYL2),YB5-YL5-YB9 in the central part of the area and YB4 -H52 and YL3 in the east part of the area.