US energy leader LeBoeuf Lamb Greene & MacRae and Herbert Smith have bagged roles advising coveted Asian power giant CNOOC on its $2.3bn (£1.3bn) acquisition of a 45% stake in a Nigerian oil and gas field as Chinese companies step up the hunt for foreign acquisitions.

The deal will see CNOOC, the Chinese state-owned energy giant, buy a significant stake in the Apko field, the offshore field owned by South Atlantic Petroleum. The acquisition is the second largest overseas investment by a Chinese company to date.