Marathon Petroleum, which owns the Kinsale gas field, is understood to be among the bidders for a stake in the Corrib gas field located off Achill Island.

The Norwegian company Saga Petroleum is considering several bids for part of its 40 per cent share in the field, which has the potential to be one of the largest finds ever made in Irish waters.

Saga is selling more than a quarter of its stake in the field, with bids expected to start at $28 million (€26.4 million). A spokesman for Saga said the most suitable bid would be selected within two to three weeks.

The valuation of Corrib is based on potential reserves of some 1.2 trillion cubic feet of gas.

The company is selling part of its stake because of a worldwide asset sell-off after recent poor results. It intends to retain at least 25 per cent of its share in Corrib, which enters its final testing phase in the next fortnight.

The other shareholders in the Corrib field are Statoil, which recently entered an alliance with the ESB and holds 15 per cent and Enterprise Oil (45 per cent), which has been carrying out test drilling at the site.

A spokesman for Marathon refused to comment on whether it was among the bidders but said it was always looking for international exploration opportunities.

Marathon, headquartered in Houston, Texas, has generated significant revenues from its reservoirs at Ballycotton and Kinsale, off the Cork coast, but these are expected to run dry in five years.

It is understood that businessman Mr Declan Ganley is also interested in buying into the Corrib field. His company, Grande Portage, is currently bidding for IFI, one of the largest gas users in the State. A spokesman for Mr Ganley declined to comment.

Enterprise Oil is preparing to begin final testing on the Corrib and a nearby well called Shannon.