But Roc said the commerciality of the well would not be known until all the subsurface data has been collected and analysed.

Aigrette-1 was drilled to a total depth of 4803m. However, the JV has now decided to deepen the well by a further 203m to continue exploration of the Cretaceous section, where the oil column was encountered.

At 6am (local time) yesterday, the Atwood Hunter rig was continuing to drill in an 8½-inch hole at a depth of 5052m.

Aigrette-1 lies in about 1380m of water, about 43km northwest of the 2003 Pelican-1 gas discovery and 193km north-northwest of the Chinguetti oil field.

Operator Dana Petroleum has a 36% interest in the project, while Gaz de France has 27.85%, Hardman 16.2%, Woodside 15% and Roc Oil Company 4.95%.