The tight gas reservoir in the central Yuanba area of Sichuan basin is one of the major breakthrough in oil and gas survey in recent years. The fractures have important influence on the migration

enrichment and production capacity of the natural gas.Based on the outcrop

core

imaging log

inclusion analysis and acoustic emission experiment data

we studied the fracture characteristics and its genesis of structural fractures in this area. The low-angle shear and high-angle shear fractures lead to the tectonic origin. The fractures have the characteristic of middle scale

minor width（sealed）

high thickness

lower density and less filled degree. The high-angle and vertical fractures have better validity. It shows that there are three fracture generations in central Yuanba area: the first stage fractures are formed in late-Yanshanian tectonic movement

NW—SE and NE—SE of plane "X" conjugate shear fractures and low section shear fractures are formed under the compression of SN tectonic stress. The maximum effective principal stress of the paleostructural stress is 18.8 MPa. The fractures in the second stage are formed in middle Himalaya tectonic movement

SN and EW of plane "X" conjugate shear fractures are formed under the compression of NE tectonic stress. The maximum effective principal stress of the paleostructural stress is 27.9 MPa. The third stage are formed in late Himalaya tectonic movement. The structural stress direction is still NE

which mainly forms NW angle section shear fractures and the maximum effective principal stress of the paleostructural stress is 38.6 MPa.