Geological controlling factors of gas hydrate occurrence in Qilian Mountain permafrost,China

In order to search after the control of geological factors over gas hydrate storage in Qilian Mountain permafrost,the grain size,fault fracture zone and permafrost properties of DK-2 to DK-6 borehole core samples have been discussed in detail.It has been considered that the gas hydrate occurrence in the study area is principally controlled by regional main faults,which can offer fluid channel for deep gas source.And the small fault and fracture zone could provide part of the fluid source and storage space.The source of gas mainly consists of deeper thermogenic gas.In addition,the main particle size fraction bearing gas hydrate is different in varied sedimentation,and local coarse clastic sediment can supply favorable storage space.Moreover,not only the thickness,but also the strata of permafrost are important for the existence of gas hydrate.A favorable grain size of cap rock is probably conductive to the occurrence of hydrate.Besides,the Jiangcang Formation may also have a certain degree of facies-control role to gas hydrate.