天然气水合物体系动态演化研究(Ⅲ):水合物的产生、聚集和分解

Researches on dynamic evolution of gas hydrate system (Ⅲ): Formation, accumulation and decomposition of gas hydrate

从天然气水合物的产生、聚集和分解,分析天然气水合物的动态演化过程.沉积压实、地温梯度、构造运动以及深部流体对水合物产生的效率起决定作用.根据流体的运移和天然气水合物在水合物稳定带中的分布状况,天然气水合物的聚集可以分为构造聚集、地层聚集和混合聚集三种模式.当由于各种原因引起海底温压条件变化时,天然气水合物会发生分解.水合物也会在水体中上浮,在这个过程中,水合物的分解速率能高出其溶解速率二至三个数量级.海底泥火山、甲烷气柱、甲烷气裂缝、双似海底反射等大量的证据,都有助于揭示天然气水合物体系的动态演化的特征.弄清楚天然气水合物的动态演化过程对于我们未来对这种潜在能源的开发利用,并分析其在全球变化、碳循环以及海底滑坡中所起的作用有着相当重要的意义.

In this paper, we analyze the dynamic evolution of gas hydrate based on its formation, accumulation and decomposition. Sedimentation/compaction, geothermal gradient, tectonic movements and deep fluid play a critical role in the formation of gas hydrate. According to the mode of fluid migration and gas hydrate concentration within GHSZ, gas hydrate accumulations are distinguished as structural accumulation, stratigraphic accumulation and combination accumulation. When the temperature-pressure condition of sea floor changes due to kinds of reasons, gas hydrate will decompose. Gas hydrate may rise through seawater. During this course, the dissociation rate of gas hydrate can be 2 to 3 orders of magnitude greater than the dissolution rate. Submarine mud volcanoes, methane plumes, methane vents, double bottom-simulating reflections(dBSR) and other evidences can help to uncover the characteristics of the dynamic evolution of gas hydrate. To make clear the dynamic evolution of gas hydrate will shed light on the exploration and use of this potential energy in the future and analyses of its influence on global climate change, carbon cycle and submarine slides.