China’s largest listed oil company PetroChina has launched a joint bid with Royal Dutch Shell to acquire Australian natural gas producer Arrow Energy, the Wall Street Journal reported. The US$3 billion bid would boost Shell’s position in the natural gas sector two years after the company purchased 30% of Arrow’s coal-bed gas assets. Australia’s significant volume of coal-bed gas, which is found in coal seams, has raised interest with a number of international companies. The gas was for a long time considered a hazard, but its value as an alternative energy source has ballooned in recent years, attracting US$16 billion in investment in 2008 alone. Both Shell and PetroChina have been reluctant to discuss the potential deal, with Shell only willing to admit that it is participating in discussions.