Friday saw PetroChina Co., China's biggest listed oil firm by capacity, revealing a fall of 7.2% in its first-half net profit from a year earlier, the blame of which goes to lower oil prices and weaker energy demand.

The second half of the year will also see the world's oil market dealing with uncertainties, predicts the Beijing-based company. However, the company, while considering China's thirst for energy, said the top priority will be upstream exploration, particularly outside the country.

Recently, government approval to invest in Nippon Oil Corp.'s Osaka refinery was obtained by the state-owned PetroChina Co., thus marking the nearing of another overseas refinery stake acquisition.

On Friday, it was revealed by the National Development and Reform Commission, China's top economic planner, that it had passed the approval; however, it gave no further details.

In the latest billions-of-dollars overseas energy and resource-related takeovers by cash-rich Chinese companies, Asia's oil and gas bigwig PetroChina has gone in for a $1.02 billion (1.47 billion Singapore dollars) acquisition of Keppel Corp's 45.5 percent stake in Singapore Petroleum Company (SPC).