Gas source for gas hydrate and its significance in the Qilian Mountain permafrost, Qinghai

Gas source for gas hydrate is not clear yet in the Muli of Qilian Mountain permafrost. In this paper a case is illustrated in the hole of DK-2 during gas hydrate drilling; gas composition and isotopes of gas hydrate and its associated gases are analyzed; organic geochemistry on mudstone, oily shale, coal, oil & gas indications are correlated within the interval of gas hydrate occurrences; the aim is to discuss the source of gases from gas hydrate and its implication to gas hydrate exploration in the study area. Results from gas composition and isotopes of gas hydrate and its associated gases reveal that the origin of gases from gas hydrate is mainly concomitant with deep oil or crude oil in the study area. Parameters for the abundance, type and thermal evolution of organic matter in mudstone, oil shale, coal in the same interval of gas hydrate occurrence suggest that these strata, especially within gas hydrate stability zone, play little role in gas sources for gas hydrate. Reservoir pyrolysis results for oil & gas indication-bearing cores reveal that oil & gas indications are closely associated with gas hydrate within its interval, indicating that they may serve as a sign of gas hydrate in the study area. ► Gas source for gas hydrate is resolved for the first time in this paper. ► Origin of gases from gas hydrate is mainly concomitant with deep oil or crude oil. ► Oil & gas indications are closely associated with gas hydrate within its interval. ► Oil & gas indications may serve as a sign for gas hydrate in the study area.