BEIJING - Top oil and gas firm PetroChina raised daily output at its largest Sulige gasfield, in northern China's Ordos Basin, to 25.6 million cubic metres, up 67 percent from last July, its parent CNPC said.

The annual production capacity at Sulige, part of Changqing oilfield, is expected to quadruple from the current level at 35 billion cubic metres (bcm) by 2015, the report on website said, following the firm's plan to massively increase Changqing's total output.

PetroChina has aimed to lift oil and gas output in Changqing to 50 million tonnes of oil equivalent in 2015, replacing Daqing as its largest, despite crude output at the aged oilfield falling 3.6 percent in 2008.

At 35 bcm, Sulige would account for around half of China's total gas output in 2008, which was 76.1 bcm. (Reporting by Beijing newsroom; Editing by Jacqueline Wong)