Going under the sea for 'fire in ice'

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Last updated at: (Beijing Time) Monday, December 22, 2003

Going under the sea for 'fire in ice'

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Going abroad may not be a new experience for Chen Duofu, a much travelled scientist based in South China's Guangdong Province. But his visit to the United States last May turned out to be exceptional.

He was invited by Cornell University to join a scientific expedition in the Gulf of Mexico. During the 10-day trip, Chen and his American fellows took a mini submarine 500 metres below the surface to watch a wonder of nature: gas hydrate, a crystalline solid lying in seabeds, which many scientists believe may be the source of the next generation of energy for the human race.

Chen claimed to be the first scientist from the Chinese mainland to have had such a close encounter with gas hydrates in a natural setting.

He described them as glowing beautifully when illuminated in the orange light from the submarine. Chen said the trip was an exciting, long-cherished dream that came true.

"We have seen man-made gas hydrates before in labs, but never in their natural environment," Chen said.

"Quite a few Chinese scientists have ventured into this research area, but none have had the opportunity and facilities to see them deep in the sea before."

In the Gulf of Mexico, the Americans placed cameras in the seabed near the hydrates to monitor their every change. In China, not a single block of such hydrates has been located so far despite increasing evidence of their existence in the nation's eastern and southern seas.

"We are latecomers," Chen said. "Yet more and more people at home have come to realize its value as the next generation of energy."

The call for advancing research and the investigation of gas hydrates has become louder at home over the past month.

Two international symposiums on gas hydrates were held in Guangzhou and Beijing in a matter of only 30 days, followed by the initiation of China's first scientific gas hydrates project, Chen revealed.

The project, initiated by several research institutes in Guangdong Province, has won support from the Chinese Academy of Sciences, China's top scientific research body, and will formally begin soon, Chen said.

"The academy's approval of the project came very swiftly, only several months after our application," he said.

"Normally, such an application could take a couple of years to get reviewed and approved."

In addition, the Ministry of Land Resources has also moved quickly to push for possible exploration of the gas in the South China Sea.

"They have been in contact with us for co-operation," said Chen, a researcher at CAS' Guangzhou Institute of Geochemistry.

Such a quick reaction reflects the country's rising concern about its sustainable energy supply over the next century, for which the gas may prove the answer, Chen said.

New dimensions

With the economy growing steadily, energy shortages have been looming in China. Since early this year, an increasing number of regions have been struck by shortages - something unseen for years.

And around the globe, rising energy consumption is obvious.

A US government report suggests humans consume 4 billion tons of coal and 2.5 billion tons of oil each year, and the amount continues to increase at 3 per cent per annum.

At such a rate, the proved coal deposits may only sustain humans for another 200 years, the report noted.

If the consumption increases, which is very likely given the steady increase of the global population, the deadlines will come sooner than expected, experts warn.

Humans should look beyond traditional fossil fuels such as coal and oil for new energy sources, of which the most promising are helium, hydrogen and gas hydrates, said Jin Xianglong, a leading Chinese oceanographer.

Gas hydrate, known as "fire in ice," has stood out in recent years as a clean and bountiful energy supply.

Scientists worldwide have been committed to the research of gas hydrates in the hope they will succeed coal and other fuels by the middle of this century.

A gas hydrate consists of crystalline blocks each of which are formed by a gas molecule surrounded by a cage of water molecules.

Its structure makes it similar to ice, except that it is stabilized by the guest gas molecule within the cage of water molecules.

Many gases have molecular sizes suitable to form hydrates, including such naturally occurring gases as carbon dioxide, hydrogen sulphide and several low-carbon-number hydrocarbons. But most marine gas hydrates that have been analyzed are methane hydrates.

"Methane hydrates are probably the best candidates for the next generation of energy," Jin pointed out. He has on more than one occasion called for greater research efforts in the field in China.

When extracted and placed under normal atmospheric pressure, the gas hydrates break up as the highly concentrated methane escapes.

Theoretic calculations prove that gas hydrates are perfect energy concentrators. The breakdown of a unit volume of methane hydrate can produce about 160 unit volumes of gas.

Based on geological surveys conducted by scientists worldwide over decades, it is estimated that methane hydrates may contain twice the amount of the carbon found in all of the world's coal, oil and non-hydrate natural gas combined.

Many countries have invested huge funds in projects to survey and research the physical and chemical properties of this miraculous matter.

The unusual association of two molecules in a solid substance without bonding has intrigued scientists since the first production of chlorine hydrate almost two centuries ago.

However, the subject appeared to be purely academic until solid hydrate was found to be plugging natural gas transmission lines in the 1930s.

Then, in the 1960s, naturally occurring methane hydrate was observed in Siberian gas reservoirs.

As knowledge about natural methane hydrate grew, scientists realized that, given the ubiquity of both methane and water in nature, methane hydrates could be present in vast quantities in any environment with suitable pressures and temperatures.

So far, most of the gas hydrates have been found in sea-floor sediments at least 500 metres below the surface, with the rest in the permafrost area in polar regions.

However, they may not be able to exist beyond a depth of 1,000 metres, where the relatively high temperature and pressure breaks up gas hydrates, releasing the methane.

The coexistence of gas hydrates with sea-floor sediments has inspired scientists to identify their location and distribution across the global ocean floor.

The possible reason, scientists suggest, is that most gases in hydrates are biogenic methane generated by bacteria from organic erosion, while sea-floor sediments serve as a shield against oxidation.

Over the past three decades, expeditions to polar regions and deep-water continental shelves all over the globe have consistently reported discoveries of methane hydrate.

China's efforts

China did not start initiating such research and surveying until the 1990s, when scientists in association with several related governmental agencies conducted surveys in continental shelters along the nation's eastern coast.

Latest exploration of the South China Sea's seabed has found sufficient evidence to suggest a vast hydrate reserve, Chen said.

"The evidence gathered so far is good enough," he said, "but the problem is we have not yet obtained a block of such hydrates from the seabed. We need to go there to get them."

Several countries have taken the lead in the search, Chen admitted.

As early as the 1980s, countries like the United States, the former Soviet Union and Japan had drawn up their long-term programmes to survey and research gas hydrates close to their territories.

Surveys of the sea floor of the Atlantic Ocean to the east of the United States in 1995 found, for the first time, gas hydrate reserves suitable for commercial drilling.

Japan has invested huge funds searching the sea floor for gas hydrates since 1994 and established a state commission in 1995 to continue seabed surveying.

Japan, Canada and the United States recently completed the world's first trial drilling of gas hydrates in Canada, a major step toward the large-scale mining of the resource.

About two years ago, China's Ministry of Science and Technology asked the National Society of Energy Research to conduct a gas hydrate study.

The study triggered a series of symposiums and increased social concerns about the issue.

Chen said the initiation of their project is merely a starting point for long-term research and investigation.

"It will take more than 20 to 30 years to complete," he said.

The length of the project is based on the technologies related to the prospecting, exploration and application of hydrates, as they still need to be greatly enhanced.

Taking the exploration and application of gas hydrates as an example, a few approaches have been developed to transform hydrates into gases, but the costs are still too high for industrial use.

Even if the technological barriers are removed, it does not necessarily mean that exploration can start immediately.

There is still the concern about the impact of exploration on the global environment, which had been ignored until recently.

Theoretical calculations have found that the exploration of methane hydrates might have a greater impact on the global climate than carbon dioxide does in respect to the greenhouse effect.

And worldwide observations have found emissions of methane into the air at a rate of 0.9 per cent annually, or three times that of carbon dioxide.

In addition, large-scale exploration of methane hydrates may substantially change the geological structure of the sea floor where they exist.

All these issues have to be taken into account and carefully assessed when considering taking the next steps, Chen said.

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