Hong Kong: Petro-China Co Ltd, the world's most valuable oil and gas producer, posted a disappointing 3.7 per cent rise in second-half earnings after refining losses and over $6 billion in special taxes took the shine off soaring global prices and rising output.

Crude oil prices jumped more than a third in July-December to nearly $96 a barrel, and have since topped $111 on tight supply, geopolitical risk and a weak dollar.

International oil majors from ExxonMobil Corp to Royal Dutch Shell have posted record levels of profitability.

Analysts say PetroChina's income would take another hit this year from so-called windfall taxes - which increase as international oil prices rise - and widening refining losses. It paid 44.58 billion yuan ($6.31 billion) in windfall levies in 2007, 54 per cent more than in 2006.

This year, the company said that it will continue to search at home and abroad for resources, with an aim to increase overall oil and gas production by seven per cent to 1.189 billion barrels-of-oil-equivalent in 2008, exceeding last year's 4.8 per cent increase. It plans to set aside 132.3 billion yuan for exploration and production in 2008.

The largest of China's energy triumvirate, which includes top Asian oil refiner Sinopec Corp and offshore specialist CNOOC Ltd, said July-December net profit rose to 63.8 billion yuan versus 61.54 billion yuan.