OISIN Fanning has said a gas field off the west coast being explored by his San Leon Energy company could contain more gas than Shell's controversial Corrib field.

Fanning, chairman of the London-quoted company, said seismic exploration of its Slyne prospect about 100km off the Atlantic coast had just finished but he believed the field could contain up to three trillion cubic feet of gas. About half the gas could be recovered. Extensive scrutiny of the seismic data will now get underway before any test drilling of the site begins.

"It is on trend with the Corrib field and we think it is as big, if not bigger. The rough stuff coming through is very positive. That Atlantic area is very positive for Ireland. It is like the North Sea 30 years ago. There is definitely oil and gas there," Fanning told the Sunday Tribune last week.

The company owns 50% of the Slyne field with the rest owned by Lundin Petroleum. Fanning said test drilling would begin next year.

As the cost of drilling is around €120m, San Leon will bring in a major international oil and gas company to finance the testing, diluting its stake in the gas field.

Fanning said the availability of offshore oil rigs had increased since exploration ceased in the Gulf of Mexico following the BP Deepwater Horizon disaster.

"We will bring big partners who have much bigger pockets than ours and reduce our percentage holding in the field," he said.

Shares in San Leon have fallen 22% this year, giving the company a value of £59m (€72m) at the close of trading last week.

The company raised £3.1m (€3.8m)from investors earlier this month to fund its exploration costs. In addition to the Slyne field it is also looking for oil and gas in Poland and Morocco.