抄録
Up-to-date information on methane hydrates was reviewed from the view point of new energy in the ocean. At first, a history of hydrate discovery was briefly introduced. The phase diagram and the crystal unit structure were classified by considering the cavity of water cages and that of the guest molecules. The distribution on the earth, the depth of the sediments containing methane hydrates, and the estimated mass of methane hydrate were theoretically discussed by considering the phase diagram of methane+water. The origin of natural gases was divided into two types, biogenic and thermogenic. Then, the identification and measuring of gas composition and isotope contents were introduced. Finally, the activity of a national project named“The Research Consortium for Methane Hydrate Resources in Japan”and our contribution were also described, and the exploitation programs at the seabed in the offshore of Honshu island, Japan, were considered.
