青藏高原天然气水合物的形成与多年冻土的关系

Relationship between permafrost and gas hydrates on Qinghai-Tibet Plateau.

天然气水合物是一种新型清洁能源,赋存在多年冻土区和海洋沉积物等低温高压环境中。青藏高原多年冻土面积占高原总面积的一半以上,是可能的天然气水合物赋存区。根据青藏高原多年冻土条件和天然气水合物形成的热力学条件,讨论了多年冻土地温梯度、冻土厚度与天然气水合物形成的热力学条件之间的关系和青藏高原存在天然气水合物的可能性。结果表明,青藏高原多年冻土区基本具备形成天然气水合物的热力学条件,最适宜的热力学条件是多年冻土地温梯度接近或略大于多年冻土底板附近融土的地温梯度,且融土地温梯度越小,越容易形成天然气水合物。估算得到天然气水合物最浅的顶界埋深为74m左右,最深的底界埋深达上千米。

Gas hydrates are a kind of new clean energy. They are found in low-temperature and high-pressure environments in permafrost and marine sediments. The permafrost on Qinghai-Tibet Plateau, which accounts for about half of the total area of the plateau, may be a potential region of gas hydrates. According to the permafrost characteristics of the plateau and thermodynamic conditions of formation of gas hydrates, the relationships of the permafrost thermal gradients and thickness with the thermodynamic conditions of formation of gas hydrates are discussed. In addition, the possibility of the existence of gas hydrates on Qinghai-Tibet Plateau is also preliminarily analyzed. The results show that the permafrost regions on the plateau have basic thermodynamics conditions for formation of gas hydrates. The best thermodynamics condition is that the thermal gradient of permafrost is close to or slightly higher than that of thawed soils near the permafrost bottom, and the lower the thermal gradient of thawed soils, the more easily gas hydrates will be formed. It is estimated that the shallowest burial depth of the top of the gas hydrate layer is -74 m and that the deepest bottom of the layer is up to one thousand meters.