The delayed buy back has led to questions as to what Shell plans to do with the cash.

While Shell said it would be using the cash to manage its balance sheet and to invest in upstream operations, the Shell ledger is already more than A$6 billion larger, due to a range of asset sales according to analyst SG Securities.

"The decision not to buy back more shares will raise investor concerns, while fears of an acquisition would accentuate," said SG.

Australia's LNG contract with Guandong province in China is thought to have eased the concerns the federal government had about the influence of Shell possibly stifling the growth prospects of the North West Shelf venture.

Woodside shares have risen almost 30% from their low at $10.10 in March to trade at $13.30 today.