It has carried out seismic studies and has said it will start exploratory drilling this year.

This estimate comes after seismic studies of the waters and compares to a previous one of about 2 billion barrels.

Lysell added that the zone's old resource estimates had to be confirmed by new seismic studies and may prove overblown.

The location of the field has been known about for some years and seismic studies and drilling have taken a long time.

We have invested heavily in the technology to interpret the results of our seismic studies and it paying off, Mr Hough said.

Exploration firm Providence Resources says 3D seismic studies carried out on a site at Spanish Point are likely to lead to commercial development.

Also in March, guerrillas set fire to and destroyed a helicopter from a contractor hired by Argentine company Pluspetrol as engineers worked on seismic studies.