China Petroleum & Chemical Corporation (Sinopec) announced Thursday on its website that it will start explorations for shale gas in Southwest China through a newly-launched division.

"The new department in Sichuan Province will try to achieve a breakthrough on shale gas explorations in three years and to realize industrial explorations in five years," the announcement said.

Shale gas is an unconventional gas resource reserved in shale rocks. It has become an increasingly important source of natural gas in the United States, Canada, Europe, Asia and Australia.

Sinopec started evaluating shale gas exploration in Southwest China's Sichuan Province in April, and its annual output may hit 2.5 billion cubic meters in five years, according to the China Business News.

"Shale gas exploration will be a key part of the future development of clean energy," said Su Shulin, president of Sinopec.

China's top oil and gas refiner plans to build 2.5 billion cubic meters of shale gas production capacity by the end of 2015. And the country has set goals to produce 30 billion cubic meters of gas a year from shale, the equivalent of almost half the country's gas consumption in 2008.

Unlike the US and Canada, China lacks advanced technologies and still relies on foreign companies. Shale gas exploration cost in China is too high to be used as a commercial energy so far.

Earlier reports said Sinopec had started shale gas explorations in Guizhou and Jiangsu provinces with the oil giant British Petroleum (BP), which is consumed by political and public relations troubles as the Gulf of Mexico oil calamity worsens in the United States.

According to estimates with the International Energy Agency (IEA), the world's shale gas reserves are about 456 trillion cubic meters in total, and China's exploitable reserves are estimated at 26 trillion cubic meters. China's potential gas-bearing shales are mostly located in Sichuan Province, North China's Inner Mongolia Autonomous Region and Northwest China's Xinjiang Uyghur Autonomous Region.