Methane hydrates, which are ice like materials and constructed with methane and water molecules, are spread widely under permafrost and deep water areas. It is thought that methane hydrates are ones of occurrence type of methane and can be future energy resources.BSR (bottom simulating reflector) occurs at the basement of GHSZ (gas hydrate stability zone) and therefore it is used to detect occurrences of methane hydrates in deep waters using reflection seismic data. At the same time, BSR is only the first step for methane hydrate exploration because BSR does not provide information about thickness, saturation and type of methane hydrate bearing zone. From the viewpoint of resource exploration, practical methods to analyze details of methane hydrate resource fields have been required.We constructed an effective strategy to delineate methane hydrate concentrated zones, of which reservoir are turbidite sand bodies, utilizing four following indicators in 3D seismic data: (A) BSR, (B) turbidite sequence (above BSR), (C) strong seismic reflectors and (D) relatively higher interval velocity, suggesting methane hydrate concentrated sand layers. It enabled us to delineate methane hydrate concentrated zones and evaluate their rock volume successfully in the eastern Nankai Trough as similar as prospects and leads in conventional oil and gas fields are delineated by geological and geophysical approaches.
In general LNG chain is economically feasible for natural gas reserve with sizable volume over several Trillion Cubic Feet (TCF) and long distant transportation projects. Feasibility studies reported so far have appeared that Natural Gas Hydrate （NGH）chain (production, ocean transportation, and re-gasification) had economical advantage, particularly under a certain condition with suitable size of gas reserve and transportation distance.
In industrial and commercial facilities, gas composition must be carefully maintained during storage and transportation to guarantee the gas quality. In this study, we investigated composition of gas in hydrate phase formed from city gas and gas phase. As a result, it was found that the thermodynamic stability is greatly influenced by the heavier components, such as ethane, propane and iso-butane that are contained in a natural gas and a city gas. Also it was found that the equilibrium line of hydrates with methane as the main component was shifted to the low-pressure and high temperature side. Especially, in the formation of mixed gas hydrates, it was shown that inclusion rate of methane, the main ingredient, is comparatively low.
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