China has produced gas hydrates in the northern part of the South China Sea, according to a government department.

The China Geographical Survey (CGS) said it managed to collect samples from the Shenhu area in the South China Sea in a test that started last week. Production of 16 Mcm/d (564.8 Mcf/d) of gas, nearly all of which was methane, was achieved from the test.

Gas hydrate, methane hydrate in particular, is a cage-like structure of crystallized ice that contain trapped molecules of methane, the main constituent of natural gas, the CGS said. If methane hydrate is either warmed or depressurized, it reverts back to water and natural gas.

According to the U.S. Department of Energy, global estimates vary but the energy content of methane in hydrates is “immense, possibly exceeding the combined energy content of all other known fossil fuels.” But no methane production other than small-scale field experiments has been documented so far such as the recent study offshore Japan.

Japan’s trade ministry on May 8 reported success in producing gas last week by extracting methane gas from methane hydrate deposits offshore Japan’s central coast.

The tests being run at two different wells are the first since 2013, when Japan achieved the world’s first-ever extraction of gas from offshore deposits of methane hydrate, a frozen gas known as “flammable ice.”

Japan’s Ministry of Economy, Trade and Industry (METI) said the methane hydrate production tests will continue for a combined four to five weeks. Japan’s first methane hydrate tests in 2013 ended abruptly after less than a week due to problems with sand flowing into the well.

Japan, which imports nearly all of its energy sources, has been aiming to launch private sector commercial production of methane hydrates by between 2023 and 2027, but METI officials have said the goal will still be a challenge as many obstacles remain to be solved.

Japan is the world’s top importer of LNG, and its need for domestic gas resources has become greater since the Fukushima nuclear crisis in 2011 shut down most of its nuclear power plants and sharply raised fossil fuel imports such as LNG and coal.

Methane hydrate is formed from a mixture of methane and water under certain pressures and conditions. India, Canada, the U.S. and China are among the countries also looking at exploiting hydrate deposits as an alternative source of energy, the trade ministry said.

A Japanese study has estimated that at least 1.1 Tcm (40 Tcf) of methane hydrates lie in the eastern Nankai Trough off the country’s Pacific coast, equal to about 11 years of Japanese gas consumption.

—Staff & Reuters Report