The potential amount of methane in natural gas hydrate is enormous, with current estimates at 10 exagrams (10,000 gigatons) of methane carbon. Inventory reports point to clathrates being present in at least 44 regions worldwide. Initial estimates, from a US Geological Survey, suggest carbon deposits in hydrates are double the size of all known oil, gas and coal reserves3 .
Methane clathrates can be found either beneath the seafloor or underneath Arctic permafrost.
Potential for use
Nations are trying to match the shale gas revolution in North America and make energy independence a reality. Clathrates could represent a future source of hydrocarbon fuel and whilst shale is only found in certain parts of the globe, methane hydrates are found under most sea beds. In order to extract the gas, specialised equipment must be used to drill into and depressurise the hydrate deposits in order to separate the methane from the ice. The gas is then collected and piped to the surface.
Clathrates are more stable at a higher temperature than LNG (-20o C vs. -162o C) and there has been discussion around converting natural gas into clathrates rather than liquidation, saving on refrigeration and energy costs. However, conversion factors currently mean this is an economically unviable option.
Barriers to use
Extraction is an issue; in the majority of sites, deposits are likely to be too dispersed for economic extraction. Despite their abundance, most hydrates are located either in colder environments or deep underwater; where it is currently too difficult and too expensive to drill5 . Other problems facing commercial exploitation are detection of viable reserves and development of the technology for extracting methane gas from the hydrate deposits.
Methane is a greenhouse gas, and discharge of large amounts of methane into the atmosphere would contribute to extreme climate change6 . Explorers must find a way to avoid releasing large quantities of methane from hydrates into the air and the ocean. Methane traps heat so effectively it is about 10 times more potent than carbon dioxide as a greenhouse gas7 .
Burning the natural gas on extraction would produce a massive amount of CO2; researchers have considered the possibility of pumping the CO2 back into the undersea lattices after methane extraction to create a carbon neutral process. This was trialled by Conoco-Phillips in the North Slope of Alaska in 2012 and has been proven technically possible but currently not a viable option8 .
Latest news – Japan
On the 12th March 2013, Japan reported it had successfully extracted natural gas from frozen methane hydrate off its central coast, in a world first. The gas field is about 50km away from Japan's main island, in the Nankai Trough. Engineers used a depressurisation method that turns methane hydrate into methane gas. Production tests are expected to continue for about two weeks.
A survey of the gas field is being run by state-owned Japan Oil, Gas and Metals National Corporation (JOGMEC). A team including Oil & Natural Gas Corp., India’s biggest energy explorer, will drill off the east coast this year and try to produce the fuel, according to two officials at the regulator Directorate General of Hydrocarbons9 .
A Japanese study estimated that at least 1.1tn cubic metres of methane hydrate exist in offshore deposits. This is the equivalent of more than a decade of Japan's gas consumption10 . Government officials have said that they aim to establish methane hydrate production technologies for practical use within five years.
The US is currently funding 14 different research projects into the energy source and India’s biggest energy explorer (Oil and Natural Gas Corp.) is close behind Japanese developments11 . Following Japan’s recent success, it is evident that more will follow in an attempt to mimic North America’s shale gas phenomenon.
By Caroline Knight
2. Also called methane hydrate, natural gas hydrate, fire ice