Accumulation mechanism of natural gas hydrate in the Qilian Mountain permafrost, Qinghai, China

Qilian Mountain is the only permafrost area in China where natural gas hydrates have been obtained through scientific drilling. Many studies performed on regions from perspectives of sedimentology and petroleum geochemistry, especially reservoir forming conditions exploration methods. However, there are still more divergences its evolutionary process, time, accumulation mechanism. In this study, a total 500 core samples were collected hydrate drilling wells DK-8, DK13-11, DK12-13 permafrost. Gas components, carbon isotopes methane, organic (TOC), chloroform bitumen “A,” concentrations kerogen element, vitrinite reflectance ( Ro ) analyzed. The results show that hydrocarbon source rocks Middle Jurassic Muli formation Upper Triassic Galedesi good rocks, with content “A.” at mature stage matters, matter types mainly Ⅱ 1 2 peak generating crude oil immense petroleum-associated gas. Also, highly stage, producing offering efficient for hydrate, Ⅲ . Laboratory experiments numerical analysis indicate has experienced three phases: migration aggregation Late to Early Cretaceous, overall uplift Miocene Pliocene, free deposits Quaternary. experimental sources, thickness, structural played key role controlling occurrence distribution hydrates.