Norwegian oil company Statoil said yesterday it had abandoned another exploratory well off the northwest coast of Ireland. It is understood that the company has spent around £20 million sterling (€28.6 million) on the project.

Statoil Exploration Ireland capped and abandoned the well on the Cong Prospect, 32 miles northwest of Co Mayo, after no oil or gas was found.

"We didn't find anything," said a Statoil spokeswoman.

She said the company was analysing core samples taken from the well to determine if the surrounding area merited further exploration.

"The plugging of the Cong well is obviously disappointing," said Mr John Conroy, general manager of Statoil Ireland. "However, we were always cautious in our outlook because experience has told us that drilling offshore Ireland remains an outside bet in terms of discovering a significant commercial find."

The abandonment is another setback for petroleum exploration in the region. Statoil plugged another well in the Porcupine Basin off the Irish coast in 2001 after finding nothing.

"This is what would be regarded as a frontier area," said Prof Pat Shannon, professor of petroleum geology at University College Dublin and past chairman of the Institute of Petroleum. He said that, of the wells in the area, "one in 10 statistically might be expected to be a discovery".

Prof Shannon said the failure to find anything at the specific drilling site did not necessarily rule out that petroleum might be found elsewhere nearby.

Sources close to the Statoil project said the company and its partners had invested close to £20 million in the well. That is more than the €17 million Statoil said it would cost to complete the drilling when the project began in July. Sources said the final cost was higher because favourable weather conditions allowed drilling to continue longer than expected.

Statoil owns a 49.9 per cent stake in the Cong Prospect, which lies under 400 metres of water in the Sylne Basin.