Prioritize coal-bed gas exploitation

BEIJING -- China should give priority to the exploitation of coal-bed gas rather than shale gas, an energy expert has suggested.

Coal-bed gas exploitation is a more urgent initiative to follow, to save energy resources and ease air pollution, said Pan Wei'er, deputy director of the Science and Technology Committee of China Zhigong Party Central Committee, in an article published in China Economic Weekly.

Related reading: China to increase coal-bed methane output

Pan said, technically and financially, coal-bed gas extraction is more feasible than that of shale gas.

According to Pan, China's annual coal output has already exceeded three billion metric tons, allowing for some 20 billion cubic meters of coal-bed gas into the air every year. If all this wasted gas was used, it would match the annual generation of the Three-Gorges Dam, which is world's top hydropower station.

Coal-bed gas, non-conventional natural gas lying in coal seam, can rapidly dissipate once a colliery is exploited.

Pan said more coal-bed gas is being wasted because China's coal output keeps increasing by 200 million tons every year.

However, shale gas lies in shale, which makes it harder to lose provided the shale has not been exploited.

"Coal-bed gas extraction is of greater urgency," Pan noted in the article. "The reason is that we may not exploit shale gas over the coming decades, but there is little possibility that we do not mine coal."

China's environmental problem is intensified as a result of coal-bed gas emissions, said Pan, citing that the green house effect of coal-bed gas is 21 times as much as that of carbon dioxide.

The Chinese government had planned a total of 5 billion cubic meters of coal-bed gas to be surface mined in 2010. However, only 1.5 billion cubic meters was achieved, less than one third of the planned volume.

The US, as the second largest coal producer in the world, surface mines 60 billion cubic meters of coal-bed gas annually, even though its annual coal output barely meets one third of China's.

Pan explained that, compared with shale gas exploitation, China has fewer technical challenges in coal-bed gas exploitation.

Related reading: Will China embrace a shale gas boom?

Coal-bed gas is buried no deeper than 2,000 meters below the surface, while shale gas is averaged at 2,000 to 4,000 meters deep. In addition, coal seam is much easier to crack than shale terrane.

Another advantage of coal gas exploitation is that it can reduce gas explosions in mines, he said.

In 2011, China's mine gas explosions caused 533 deaths, topping the rest of the world, for which the main reason was that coal-bed gas was not sufficiently extracted.

The Chinese government has set a target for 2015 to reduce the number of mine accidents and deaths by at least 40 percent from the level of 2010. Related research shows that if coal-bed gas is explored ahead of coal mining, the explosion rate would drop by 70 to 85 percent.

Pan affirmed that promoting the development of unconventional natural gas is of significance to the country, as China still runs an unhealthy energy structure.

Statistics showed that coal accounts for 70 percent of the gross energy output and consumption in China. And the proportion of natural gas is 20 percentage points lower than the average level of the world, with unconventional gas even lower.

Full exploitation of coal-bed gas would sharply improve the country's energy structure, he said.