PetroSA is to begin drilling the F-O gas field off the southern coast of South Africa by the end of 2011 to maintain offshore production.

PetroSA CEO Everton September told Bloomberg that the drilling tender is expected to close at the end of this month.

The project is in the approval phase and is expected to cost about $1bn.

The F-O development may hold one trillion cubic feet of gas and will supply the refinery at Mossel Bay, which lies 390km east of Cape Town.

The field will begin production in April 2013 and is expected to remain operational until 2020.