メタンハイドレート資源開発の現状と安全性

抄録

Gas clathrate hydrates of hydrocarbon, or methane hydrates, are regarded as a potential alternative energy resource of conventional oil and natural gas, but no technically or economically feasible production technique has been established. To consider the safety of a hypothetical gas production operation, thermodynamic nature of the material and petro-physical condition of host sediments should be considered as well as facility and devices in applied production systems. Its endothermic nature may avoid uncontrolled situation of gas hydrate dissociation process and subsequent hazards such as large-scale seafloor instability. There can be five modes of hazards related to methane hydrate, namely, 1） naturally happening gas hydrate dissociation that cause impacts of seafloor stability and climate, 2） accidental formation of gas hydrate in a flowline that prevents flow causes subsequent troubles. 3） unintentional methane hydrate dissociation by human activities and its impacts on safety of facilities and personnel, and eco-system, 4） intentional methane hydrate dissociation for gas production and impacts on safety of facilities and personnel, and eco-system, Moreover, common operational risks of offshore oil and gas drilling and production should be considered. For the first offshore production test of methane hydrate in 2013, a hazard identification work was done and recommendation from the analysis was implemented in the actual operation.