Santos Ltd got a formal bid for $1.5 billion from Quadrant Energy Pty for its Australian oil and gas fields.

Bloomberg writes that people familiar to the matter said Santos is considering Quadrant Energy's offer for its stakes in its Western Australia state fields to have a broader review of all its assets.

According to the Business Spectator, the offer from Quadrant Energy, which is a joint venture of Brookfield Asset Management and Macquarie Group, is believed to be for a 45 percent stake in Santos' gas fields located in the Carnarvon Basin. Quadrant already acquired the rest of the 55 percent earlier this year when it bought the assets from the Apache Energy.

The deal could also take 37.5 percent share in the Fletcher Finucane oil field, but both Quadrant and Santos are looking for buyers for this asset, which means a Stag oil field partnership is less likely to happen.

Reuters earlier reported that Santos rejected last week a $5.1 billion takeover proposal from ruling families of Brunei and the United Arab Emirates.

Meanwhile, Japanese trading house Marubeni Corp. is also in talks to buy 3.6 percent of Exxon Mobil Corp.'s Papua New Guinea gas plant from Santos for not less than A$1 billion.

According to people familiar with the matter, Santos is negotiating to various parties on its assets. It is not yet final on which parts of their portfolio it will sell, or whether it is better to raise equity for its divestments.

In August, Santos said it is planning strategic options and that its Chief Executive Officer David Knox would resign if the downturn in commodity prices would create concerns on the company having too much debt. Santos shares went down 1.3 percent to close at A$6.34 in Sydney.

This means its decline this year has reached 23 percent, putting the company's value at A$6.6 billion.