Seismic identification and applications of methane hydrate as a future energy source
Methane hydrate, or clathrate, is an ice-like substance consisting of methane and water that is stable at low temperature and under high pressure. It has a pentagonal dodecahedron molecular structure comprising one molecule of methane surrounded by molecules of water. It is usually found in areas with low temperatures, such as in the Arctic, in the form of methane hydrate deposits above and below the lower limit of permafrost. Hydrates are also common in deep water where the water column above 300 to 500 m water depth provides the high-pressure conditions required for their formation. Pilot experiments in recent years using methane hydrates found under land ice have shown that methane can be extracted from these deposits. As efforts to extract natural gas from methane hydrate increase, it is set to become a critical energy source, particularly for resource-poor countries such as Japan. Other countries including Canada, the US and China have also been looking into ways of exploiting methane hydrate deposits (BBC News Business, 2013). Offshore deposits present a potentially enormous source of methane which can be identified at a global scale from a large 2D and 3D seismic database. In 2012, a joint project between the United States and Japan produced a steady flow of methane by injecting carbon dioxide into the methane hydrate accumulation. The carbon dioxide replaced the methane in the hydrate structure and liberated the methane to flow to the surface (Hobart M. King). Japanese engineers have also successfully developed a depressurisation method that turns methane hydrate into methane gas (The Japan Times, 2013), setting the scene for the exploitation of this future source of energy.