メタンハイドレート開発と環境影響

Abstract

Methane hydrate (MH) is expected as a new energy resource. Meanwhile it is sometimes said in general public that the MH development has an adverse affect on global environment. However, at present, it is speculated that the environmental risks of the MH development are not thought to be any more serious than those posed by the conventional oil and gas production if the MH production will be conducted by the use of the depressurization method for the pore-filling MH deposits in sandy sediments.Phase 2 of the Japan's Methane Hydrate R&D Program began in JFY2009. From this phase, the Research Consortium for Methane Hydrate Resources in Japan (MH21) began to conduct a comprehensive environmental study along the rules of the environmental risk assessment to establish an environmental management plan for future MH development. It was identified that the environmental risk factors on the MH development are almost same as the ones on the conventional oil and gas production. Meanwhile the MH21 recognized that the following events might be the environmental risk factors for future MH development ; (1) methane leakages from the seafloor, (2) discharge of production water into the ocean, (3) seafloor subsidence, and (4) submarine landslides. To predict the severities of these events, the MH21 is currently implementing to conduct the baseline surveys, develop the numerical models, conduct the ecotoxicity tests on marine organisms and construct the environmental monitoring systems for offshore MH production test planned in JFY2012.