The fat lady isn't singing yet for the backers of Dublin-based oil and gas explorer Petroceltic International, but she's backstage and clearing her throat.

Petroceltic is for sale, unable to repay its debts of more than $200 million, and caught in a war with an activist shareholder.

It is difficult to see how existing shareholders will emerge with much, if anything, from the strategic review ongoing at the company, led by experienced industry executive Brian O’Cathain.

The markets are attaching a bearish value of barely more than £20 million to the company’s equity, which a little over a year ago was under offer for more than 20 times that price. On Tuesday, barely €3,000 worth of its shares changed hands on the Iseq, but its share price dipped more than 40 per cent. It held firm yesterday, which was good news. But at 12 cent per share.

Whoever buys Petroceltic, or its assets, will have to strike a deal involving the board, its largest and grumpiest shareholder, Worldview Capital, its banks and possibly also the Algerian government, which may have a veto over deals as it licenses Petroceltic's main asset. But a deal must be done, or the company may slip into administration.

Whether Swiss-based Worldview can come up with the money to take control, or some other foreign investor steps in, Petroceltic is shaping up to be just another sad chapter in the long, disappointing story of Irish-based exploration companies.

Providence Resources, the great white hope for indigenous exploration a few years ago, is worth even less than Petroceltic. Meanwhile, Tullow Oil, which made its name abroad, is looking vulnerable as it tries to square the circle of $27-a-barrel oil with its debts of $4 billion.

At home, the medium-term effect of such low oil prices will be another long dearth of exploration activity. Drilling off the coast will be near impossible to finance as long as a barrel of oil costs less than the drum containing it.