Combustible ice extracted from seabed

Mainland scientists have extracted samples of combustible ice - a vast potential energy source - from below the floor of the South China Sea, a central government agency announced yesterday.

Energy analysts said the exploitation of the ice, a kind of natural gas hydrate, could ease China's energy dependence on oil and coal.

The extraction of the volatile ice last month also made China the fourth country to achieve the feat, along with the United States, Japan and India.

Zhang Hongtao , deputy director of the China Geological Survey Bureau, said yesterday that on the morning of May 1, China for the first time succeeded in collecting samples of combustible ice from the northern part of the South China Sea.

China has spent nine years and 500 million yuan on combustible ice research, and a preliminary survey indicates that the volume of natural gas hydrate in the sea's continental shelf could be as much as 10 billion tonnes of oil equivalent.

Professor Yu Xinghe , from the China University of Geosciences, who took part in the project, said the gas hydrate was likely to become a replacement for existing oil and gas energy sources.

Professor Yu said about 164 cubic metres of natural gas could be produced from one cubic metre of natural gas hydrate. But he said difficulties in exploitation and application meant it would take 20 or even 30 years for the gas hydrate to be used in industrial and civil applications.

Professor Yu also said that use of the gas hydrate had environmental side effects.

'It may bring environmental disasters. The gas hydrate is in the sea floor and when the combustible ice is exploited and becomes a gas, it may trigger geological movements similar to tsunami,' he said.

But he said mainland scientists were mainly focusing their efforts on detecting the gas hydrate, rather than the fuel's applications.

Professor Yu said the research bill so far was 500 million yuan, but the state had put aside 810 million yuan for the project.

The researchers would also work on three other areas, including how the gas hydrate came to be in the South China Sea, a low-latitude and hot area, in contrast to the high-pressure, high-latitude areas where it normally forms.

Natural gas hydrate usually exists in seabed or tundra areas. It is formed by natural gas and water in conditions of high pressure and low temperature. It looks like ice and can be lit up like solid ethanol, hence the name 'combustible ice'.

PetroChina, the nation's biggest oil producer, announced last month that it had made a discovery in an offshore oilfield in Bohai Bay with proven reserves equal to about 10 per cent of the country's oil and gas reserves.