King & Wood Mallesons (KWM) and Herbert Smith Freehills have advised on one of the most significant energy investments in Australia by a Chinese company – China National Offshore Oil Corporation's (CNOOC's) acquisition of BG Group's stake in the Australian liquefied natural gas (LNG) project Queensland Curtis.

The deal has seen CNOOC agree to acquire a 40% stake in the first production train of the project, in which it already owns a 10% stake, as well as equity in other parts of BG's Queensland interests, for $1.93bn (£1.22bn).

Herbert Smith Freehills acted for CNOOC, with a team led by Hong Kong corporate partner Hilary Lau and energy specialist partner Stuart Barrymore in Perth.

KWM, meanwhile, advised BG Group, fielding a team of six partners overseen by Hong Kong M&A partner Joshua Cole and natural resources partner Craig Rogers in Brisbane.

As part of the deal BG will supply CNOOC with five million tonnes a year of LNG from BG Group's global portfolio for 20 years from 2015.

Combined with a smaller deal agreed in 2010 with CNOOC, the latest transaction means BG Group's total committed LNG sales to China will be 8.6 million tonnes – making the company the largest supplier of LNG to the fast-growing energy market.

Recent months have seen a number of energy deals in the Asia-Pacific region as Chinese, Korean and Japanese investors look to markets such as Indonesia and Australia for their growing energy needs.

Japanese group Tokyo Electric Power Company took a stake in one of Australia's largest LNG developments earlier this month – the Chevron-backed Wheatstone Project, in the hope of securing long-term resources following the Fukushima nuclear disaster last March.

The $1bn (£621m) deal saw Australian leader Allens act opposite global duo Allen & Overy and White & Case.