青海木里三露天冻土天然气水合物气源性质研究

Study on the Nature of Gas Source for Permafrost-associated Gas Hydrate in Sanlutian of Muli,Qinghai

祁连山木里地区自2008年首次钻获到天然气水合物实物样品以来,其气源问题一直成为焦点。此次重点对神华青海能源开发有限责任公司投资项目实施的青海木里三露天天然气水合物系列钻井的岩心解析气的组成与甲烷碳及氢同位素、岩心顶空气的组成等进行了分析,结合不同钻井天然气水合物本身的气体组成和甲烷碳及氢同位素特征,进一步探讨了该区天然气水合物气源的成因与性质。结果显示:研究区内气源为混合成因,其中东部地区气源以微生物成因气为主,并混合少量热成因气;中西部地区气源以热成因气为主,其热解气具有原油裂解气特征,少部分具微生物改造气特征,同时还混合有部分微生物气及少量煤成气。

Since the first drilling discovery of gas hydrate samples in Muli of Qilian Mountain permafrost in 2008, the gas source problem has become the focus. On the basis of previous work, the analysis of gas composi- tion and methane carbon and hydrogen isotopes in adsorbed gases from cores, and of gas composition in head- space gas from cores was conducted in the paper. Those samples were collected from the gas hydrate drillings which were invested by Shenhua project in Sanlutian of Mull. Combined with gas composition and methane car- bon and hydrogen isotope feature of gas hydrate in the relevant drillings, the analytical results are to further ex- plore the genesis and properties of gas source for gas hydrate in this area. The results show that the gas source in the study area is of mixed genesis. The gas source is mainly composed of microbial gas partially mixed with a small amount of thermo-genic gas in the eastern part of the study area. The gas source is mainly composed of thermo-genie gas and secondarily of some microbial gas with a small amount of coal-derived gas in the middle to east of the study area. The thermo-genic gas is characteristic of crude oil cracking gas, and partly of microbial transformation gas.