青藏高原祁连山与乌丽冻土区水合物成藏条件研究

Gas Hydrate Accumulation Conditions between Qilian Mountain and Wuli Permafrost Region in Qinghai-Tibetan Plateau

为了探讨青藏高原祁连山和乌丽冻土区天然气水合物成藏条件的异同之处,对其温压场特征、大地构造位置、气源条件等进行了对比分析。结果显示:二者所具有的温压场条件均适合天然气水合物的形成,尤以乌丽冻土区最好;在大地构造位置、沉积地层、气源成因以及保存条件等方面二者却存在着较大的差别,祁连山冻土区构造活动较弱,天然气及天然气水合物的保存条件较好,而乌丽冻土区构造活动较强,持续时间更久,深大断裂更发育,不利于天然气及天然气水合物的保存;祁连山冻土区天然气水合物气源主要为有机成因的烃类气体,而乌丽冻土区钻井岩心和湖水中的气体主要为无机成因的CO2。构造活动与气源成因可能是影响祁连山和乌丽冻土区天然气水合物成藏的主要因素。

In order to study the similarities and differences of gas hydrate accumulation conditions in Qilian Mountain and Wuli Permafrost Region in Qinghai-Tibetan Plateau,its geotectonic location,temperature and pressure conditions and genetic types of gas sources were studied and compared.The results showed that the temperature and pressure conditions there were suitable for gas hydrate formation,the condition of Wuli Permafrost Region was the best.However, there existed considerable differences in geotectonic locations,sedimentary formation,source genesis and its gas sources origins and preservative conditions between Qilian Mountain and Wuli Permafrost Region.Comparatively speaking,the tectonic activities of Qilian Mountain Permafrost Region were weaker,the preservative conditions for gas and gas hydrate was better.While in Wuli Permafrost Region,its tectonic activities were stronger with longer sustaining time and the development of deeper and bigger faults,which was not beneficial for the preservation of gas and gas hydrate.The gas hydrate in Qilian Mountain Permafrost Region was hydrocarbon gases belonging to organic origin,while the gas sources of cores and lake water from Wuli Permafrost Region were carbon dioxide of inorganic origin.Therefore,the studied results show that the tectonic activities and genetic types of gas sources are main factors influencing the gas hydrate accumulation in Qilian Mountain and Wuli Permafrost Region.