An equity raising is the "last piece of the puzzle" for FAR Ltd to begin  construction of the $US4.2 billion ($6.2 billion) Sangomar project in Senegal that will make the junior oil and gas explorer one of the ASX's largest oil producers, says chief executive Cath Norman.

Woodside Petroleum, the operator of the Sangomar joint venture, is targeting a go-ahead for development by the year-end.