Production, Transportation and Storage of Natural Methane Hydrate

在日本专属经济区深海海底发现了大量的甲烷水合物。为实现小型气田天然气的经济生产，正在开发天然气水合物颗粒输送技术。本研究通过引入天然气水合物颗粒输送，提高深海甲烷水合物生产-运输-储存系统的效率，探讨了该系统的可行性。从能源安全的角度探讨了以天然气水合物颗粒储存天然气的可行性。首先，将开发系统分为1)钻井和生产，2)浮式生产系统，3)天然气水合物生产，4)装载-运输-卸载，5)储存和6)再气化。对各工序要素制定了成本估算公式，明确了整个系统的成本构成。其次，研究了实现该系统所需的基本技术。明确了天然气水合物生产过程成本在总成本中所占比重较大。此外，在近期天然气价格大幅上涨之前，浮动生产系统本身的经济可行性并不高。发现了一种分解速率极低的新型天然气水合物。阐明了非球形球团和双球形球团系统的充填率特性，阐明了振动对充填率的影响。在-85℃的温度下，天然气水合物球团在甲烷气体气氛中不溶解。对于储存罐，研究了储存罐的传热特性，并对储存罐进行了规划。从热平衡的角度出发，论证了堆垛的可行性。

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.