For the first half, net income rose 114 percent from the same period last year to 27.09 billion yuan, a company filing to the Shanghai Exchange showed. The company reported profit in the first quarter of 10.15 billion yuan in April.

The quarterly performance is the best since the second quarter of 2015, according to Reuters data. The gains were led by the recovery in oil prices since the middle of 2017 and stronger performance in the refining business.

The first-half results were above the lower-end of the guidance the company gave in July for a first-half result of 26.17 billion yuan to 28.17 billion yuan.

Revenue for the first six months of this year was 1.109 trillion yuan.

Second-quarter revenue was 567 billion yuan, up 17.5 percent from 482.4 billion a year earlier and its highest since the third quarter of 2014, according to Reuters calculations.

PetroChina's crude oil production in the first half rose to 437.7 million barrels, up from 435.8 million barrels in the first half of 2017.

Gas production in the first half increased 3 percent from a year earlier to 1,791 billion cubic feet.

The state firm, China's second-largest oil refiner, processed 551.6 million barrels of crude in the first six months of the year, up 16.1 percent from a year earlier, and refined fuel sales rose nearly 11 percent during the period.

Natural gas sales volumes were robust during the period but the company recorded net losses on imports of both piped supplies and liquefied natural gas (LNG) of 13.4 billion yuan, the company said.

Gas suppliers often sold supplies at a discount when imported prices were above state-regulated domestic prices.

Zhang Jianhua, PetroChina president, told a media briefing that the firm expects its natural gas production to rise 4 percent this year and increase to annual growth of between 4 percent to 5 percent in the next few years.

For all of 2018, Petrochina expects oil output to be 872.2 million barrels and crude processing volume to be 1.123 billion barrels, the company said at the briefing.

Full-year capital expenditure will be 233 billion yuan , the company said.

Strong refining margins as well as higher crude oil prices and robust gas sales have boosted the performance of China's three oil majors.

Sinopec on Monday reported its best first-half performance since it listed 18 years ago, while its smaller peer CNOOC Ltd also posted its best ever half-year net profit since the first six months of 2015.

(Reporting by Meng Meng and Aizhu Chen; Editing by Christian Schmollinger)