Production, Transportation and Storage of Natural Methane Hydrate

日本专属经济区深海海底下发现大量甲烷水合物。天然气水合物（NGH）颗粒输送技术正在开发中，用于从小型气田经济地生产天然气。本研究探讨深海甲烷水合物生产-运输-储存系统的可行性，使系统更有效地引入NGH颗粒运输。从能源安全的角度，对天然气水合物颗粒储存的可行性进行了研究，首先将开发系统划分为：1）钻井和生产; 2）浮式生产系统; 3）NGH生产; 4）装载-运输-卸载; 5）储存; 6）再气化。建立了各工序要素的成本估算公式，明确了整个系统的成本构成。其次，对实现该系统所需的基本技术进行了研究，明确了NGH生产过程的成本在总成本中所占的比重。在天然气价格大幅上涨之前，浮式生产系统本身的经济可行性并不高。发现了一种新型的NGH，其分解率非常低。阐明了非球形颗粒和双球形颗粒体系的填充率特征，阐明了振动对填充率的影响。还澄清了NGH颗粒在-85℃温度下不溶于甲烷气体气氛。对于储罐，研究了储罐内的传热情况，并对储罐进行了规划。从热平衡的角度分析了储料堆的可行性。

A large amount of Methane Hydrate has been discovered below the seafloor of deepsea of Exclusive Economical Zone of Japan. Transportation technology of Natural Gas in terms of Natural Gas Hydrate (NGH) pellet is under development for economical production of Natural Gas from small scale Gas fields. This research investigated feasibility of Production-Transportation-Storage system of deepsea Methane Hydrate by making the system more efficient introducing the NGH pellet transportation. The feasibility of stockpile of Natural Gas in terms of NGH pellet was also investigated from energy security point of view.Firstly, development system was grouped into processes, 1)Drilling and production, 2)Floating production system, 3)Production of NGH, 4)Loading-Transportation-Unloading, 5)Storage and 6)Regasification. Cost estimation formulas were formulated for elements of each process and the composition of cost of total system was clarified. Secondly elementary technologies necessary to realize the system were investigated.It was clarified that cost of NGH production process occupies a large potion in the total cost. It was also clarified that economical feasibility of floating production system itself is not so high under the cost of Natural Gas price before the recent steep rise of price. New type of NGH which shows very low rate of decomposition was discovered. Packing fraction characteristics of non-sphere pellet and two-sphere-size pellets system were clarified and effect of vibration on filling ratio was clarified. It was also clarified that NGH pellet is not dissolved in methane gas atmosphere at temperature of -85℃. For stockpile, heat transfer in the stockpile tank was investigated and the tank was planned. It was shown that the stock pile is feasible from view point of heat balance.