Study on Changes of Gas-Hydrate under Various Geological Processes
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摘要: 天然气体水合物是一种准稳定态的物质, 对引起温-压条件变化的各种地质作用是非常敏感的.沉积与剥蚀、海平面升降、冰期与间冰期等地质过程改变着海底环境温-压状况, 控制了沉积物中水合物的形成、保存与分解.快速沉积(尤其是海底滑坡和泥火山喷发等带来的瞬间堆积)、海平面上升、高纬地区冰期等使海底环境朝着增压、降温的方向变化, 有利于气体水合物形成与保存; 而迅速剥蚀、海平面下降、上覆冰体移除引起水合物分解.水合物的分解可以是渐渐的气体溢出, 也可以是猛然的气体喷发, 这取决于温度上升及压力降低的速度.气体水合物的“爆炸式”分解在海底表面可留下“圆坑状”地貌特征.地质过程中同一地区频繁的温-压波动可引起水合物中乙烷成分相对增加.Abstract: Gas hydrates are quasi stable and sensitive for the changes of pt conditions under various geological processes. Deposition or erosion, sea level fluctuation and the exchange of glacier interglacier alter the pt conditions on sea floor, so that affect the formation or dissociation of gas hydrates. Sudden depositing (especially accumulating by submarine sliding and mud volcano erupting), sea level rising and glacier occuring in high latitude usually make the pressure higher and the temperature lower. These are propitious for the formation and existence of gas hydrate; on the contrary, quickly eroding, sea level dropping and removing of ice cover usually cause the dissociation of gas hydrates. The dissociation can take place gradually or explosively, depending on how fast the pressure drops or the temperature increases. The "explosive dissociation" brings a lots of "pockmmarks" on the sea floor. A consequence of frequently varying pt conditions in an area enriches ethane in gas hydrates.
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Key words:
- gas hydrates /
- pt condition change /
- existence /
- dissociation
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图 1 气体水合物温-压相图
Fig. 1. Temperature-pressure stability fields for hydrate of different compositions
图 2 海平面变化过程中水合物温-压状态变化轨迹
Fig. 2. Evolutionary tracks of temperature-pressure under sea-level changes
图 4 瞬间堆积与剥蚀过程中水合物的温-压状态变化轨迹
Fig. 4. Evolutionary tracks of temperature-pressure under sudden accumulation and erosion
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