"To break the monopoly will bring more investors and openness in the market, which will raise operational efficiency in future and thus benefit the whole gas industry," said Wang.

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China's urbanization is creating huge demand for natural gas. The country is the world's third-biggest user of the fuel. Consumption rose 13.9 percent to 167.6 billion cubic meters in 2013, according to the report from the China National Petroleum Corp's Economics and Technology Research Institute.

Duan Zhaofang, a natural gas expert with CNPCETRI, estimated gas consumption in 2014 will reach 186 billion cu m, an 11 percent increase. That requires not only more output from upstream exploration, but also increasing investments in pipelines to deliver gas to households, Wang said.

"Such huge investment in pipeline construction needs diversified investors," she said.

Public figures show the construction cost of the First West-East Gas Pipeline was 140 billion yuan and the second pipeline 150 billion yuan.

China is making great efforts to fight corruption and several senior officials from PetroChina have been caught in the dragnet. Wang said scaling down the company will help prevent corruption.

PetroChina's Chairman Zhou Jiping said in April the company will open up six sectors to social and private hands: pipeline construction; nonproducing reserves; unconventional oil and gas development; refining; overseas business; and natural gas utilization.

The aim is to boost the competitiveness and influence of State-owned enterprises.