青海祁连山冻土区天然气水合物的气源条件及其指示意义

祁连山木里冻土区天然气水合物的气源条件还不清楚,这直接影响到下一步的勘查方向。文章试图以DK-2天然气水合物钻孔为例,从天然气水合物及其相关气体组成与同位素特征入手,对比分析天然气水合物产出层段的泥岩、油页岩、煤、油气显示等有机地球化学特征,探讨该区天然气水合物的气源条件及其对天然气水合物勘查的指示意义。该区天然气水合物所在层段的泥岩、油页岩、煤的有机质丰度、类型、热演化程度等参数显示,它们不能成为天然气水合物的主要气源岩层;结合天然气水合物及相关气体组成与同位素特征,判断该区天然气水合物的气体来源可能主要为深部石油(原油)伴生气或深部气源岩层的成熟-过成熟气;该区油气显示现象与天然气水合物密切伴生,或可作为天然气水合物的指示标志。

Gas source conditions for gas hydrate in Qilian Mountain permafrost of Qinghai and their implications

Gas source conditions for gas hydrate in Muli of Qilian Mountain permafrost are not clear, which will obviously affect the direction of its further exploration. With a case study of the gas hydrate in drill hole DK-2, the authors investigated organic geochemical features of mudstone, oil shale, coal, oil and gas indications in relation to the gas hydrate, in consideration of gas composition and isotopic characteristics of gas hydrate and its relevant gas. The aim of this study is to discuss gas source conditions for gas hydrate and their implications for gas hydrate exploration in the study area. Parameters for the abundance, type and thermal evolution of organic matter in mudstone, oil shale and coal in the same interval of gas hydrate indicate that they failed to become the major gas source rock for gas hydrate. In combination with gas composition and isotopic characteristics of gas hydrate and its relevant gases, the authors hold that the gas source for gas hydrate was mainly from deep oil (crude oil) associated gases or from mature to highly mature gases of deep source rock in the study area, and that oil and gas indications are closely associated with gas hydrate, which may serve as a sign of gas hydrate in the study area.