PetroChina Co, the country's biggest oil and natural gas producer, is on course to surpass its target of 2.6 billion cubic meters (bcm) of shale gas production in 2015 from fields in Sichuan province.

"Based on the production of our test wells, we are very confident to achieve or even beat our estimates for 2015," Xie Jun, deputy general manager of unit Southwest Oil & Gasfield Co, said last week.

PetroChina aims to produce 5 bcm by 2017 and 12 bcm by the end of the decade, Xie said. Output this year may reach 200 million cubic meters and large-scale commercial production will begin in the first quarter of next year, he said.

The company has nine shale gas exploration rights in Sichuan and Chongqing. Four have started or are close to commercial production.

PetroChina will invest 13 billion yuan ($2.1 billion) on Sichuan shale gas exploration and production this year and the first half of next year. Drilling cost per well in the region is about 65 million yuan at present, said Zhou Zhibin, deputy general manager at Southwest Oil &Gasfield. He expected the cost to decline with large-scale drilling and better understanding of the geology.

The company has about 3.9 trillion cubic meters of shale gas reserves in Sichuan and Chongqing, of which 1.5 bcm are buried in areas less than 4,000 meters deep. It will concentrate on exploring the fuel in those relatively easy depths in the short term, Xie said.

China halved its target of producing 60 bcm by 2020 because of geological challenges. It plans to produce 6.5 bcm of shale gas by 2015.