Methane hydrate (MH) is one of the potential resources of natural gas. In this study, we have conducted the field scale simulation to clarify permeability characteristics and gas production behavior during MH dissociation process in marine sediments. Reservoir model is based on the field data for Nankai Trough area in the adjacent Sea of Japan, and characterized by permeability anisotropy due to alternation of strata consisting of sand and mud layers. Some simulation runs were conducted, changing the relative permeability as calculation parameter. Based on calculation results, we considered the effect of this parameter on MH dissociation and gas production behavior.


Methane hydrate is ice-like solid substance in which water molecule structure contains embedded methane molecules under low-temperature and high-pressure conditions (Sloan, 1998). When 1 m3 of MH is decomposed, about 150m3 of methane gas is produced. MH is one of the potential resources of natural gas in the near future, because the large amount of reservoir exists in marine sediments or in permafrost regions worldwide (Makogon, 1988; Okuda, 1993; Sato et. al, 2001; Sato, 2001). Some extraction methods of MH from the reservoir in marine sediments have been proposed, such as depressurization, thermal stimulation and inhibitor injection (Makogon, 1981). These are all based on the in-situ dissociation process of MH that is transformed into methane gas and water. Only methane gas can be produced from the reservoirs in marine sediments. To evaluate the productivity of methane gas from the reservoirs, it is necessary to develop the production simulator and carry out parameter study by using the simulator. Fig.1 illustrates the outline of research for MH extraction from marine sediments. Especially, it is very important to estimate the properties and the permeability of MH reservoir in such situations as dissociation and consolidation.

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