Fracture characteristics and its hydrocarbon accumulation significance of tight sandstone reservoir in DY Region of west Sichuan

Fractures play an important role in the formation of Xujiahe Formation tight sandstone gas reservoir in DY Region.Through the core description and the logging interpretation,this paper identifies that the tectonic fractures with high angle mainly developed in the 3rd Member of Xujiahe Formation and the fracture strike is northwest trending in the south of study area and east-west trending in the north of study area.The degree of filling is not high.The occurrence,degree of development and space distribution of fractures are closely related to hydrocarbon migration and accumulation.Fractures not only improve the reservoir property,but also improve the infiltration capacity of reservoir.Through the study of fracture characteristics and the regional tectonic stress field,it is considered that there are two stage fractures which formed in the late Indochinese epoch and Himalayan Ⅲ period respectively.The first stage fracture is one of channels for gas migration and accumulation,and the second one is the main channel of re-adjustment and enrichment of gas when the palaeohigh becomes fault block trap due to Himalayan movement destructiveness.