水流侵蚀联合热辅助法水合物相变及分布特性

Phase Transition and Distribution Characteristics of Methane Hydrate by Heat Assisted Water Flow Erosion

天然气水合物被认为是一种未来潜在替代能源,据估计全球大约90%的水合物分布在海底沉积层中。本文考虑到海洋环境中海水资源巨大,且表层海水的温度高于水合物储层,采用海水–气两相流动结合热辅助法分解水合物,并利用核磁共振成像系统可视地分析了水合物相变特性及空间分布规律。结果表明,水合物相变首先出现在反应釜入口处,随后水合物相变前沿呈现沿水相–水合物相界面逐渐扩张的空间变化规律。此外,水合物分解速率随注入温度的升高而提高。对比发现,热辅助法结合水–气流动模式下水合物的分解速率仅为降压结合水–气流动模式下的一半,因此在水合物开采过程中可将注热、降压、水–气流动三种方法结合提高开采效率。

Natural gas hydrates(NGHs) are regarded as a potential alternative energy source, and 90% of NGHs are distributed in the seafloor sediments. Considering the huge seawater source, and the higher temperature of surface seawater than the NGHs reservoir, the heat assisted seawater-gas flow erosion was used to decompose hydrate in this study. The phase transition characteristics and spatial distribution of hydrate were analyzed visually by using magnetic resonance imaging(MRI)system. The results showed that the phase transition of hydrate first appeared at the reactor inlet,and then the phase transition front of hydrate gradually expanded along the water-hydrate interface.Additionally, the hydrate decomposition rate increased with the increasing temperature of seawater and gas. Compared with the combination mode of thermal stimulation and seawater-gas flow, the combination of depressurization and seawater-gas flow could increase the hydrate decomposition rate by about 50%, which has greater application potential on hydrate production.