Fastnet will take a 100% interested in licensing option 13/3 which covers part blocks 56/6, 56/7, 56/8, 56/9, 56/11, 56/12, 56/13 and 56/14 in the Mizzen basin and the western end of the North Celtic basin.

The initial 18-month work programme over the licensing option, which has now been named the East Mizzen licensing option, will see Fastnet reprocess a minimum of 400 kilometres of existing 2D seismic.

Depending on the results of the initial work programme, the company will then have the option to agree a further work programme where it will acquire new 3D seismic during an 18-month extension to better define the size of traps tested by previous wells on the acreage.

The 56/12-1 well was drilled by Esso and Marathon in 1975 to test large structural closures at the Base Chalk, Base Kimmeridgian unconformity and within the Lower Jurassic and Triassic.

The well was drilled to a depth of 8773 feet but failed to reach the base of the Cretaceous, with analysis of the well and 2D seismic acquired much later after drilling showing the well was drilled off-structure.

Fastnet said light oil shows were present in the 56/12-1 well near the base of the Cretaceous, with geochemical analysis suggesting the oil was sourced from the same Upper Jurassic source rocks that have sourced the Barryroe oil accumulation off Ireland.

Fastnet noted that two large structural culminations were mapped to the north-west and east of 56/12-1 which could be prospective for the same basal Cretaceous sands that were encountered in the well.

It added a number of structural leads had also been identified from existing 2D seismic for which it believes the geological setting is analogous to that for the Wytch Farm oilfield in southern England.

Fastnet is already in the process of shooting 3D seismic over its Deep Kinsale asset which will be followed by another 3D shoot on its Mizzen licensing option in the North Celtic Sea.

The company said on Friday that, following the completion of the seismic programme over Deep Kinsale, the seismic vessel will move to the Mizzen and East Mizzen licensing options to acquire a contiguous 1200 square kilometres of 3D seismic.

It added that funding for the seismic over East Mizzen had already been included in its previous cost estimate for its Celtic Sea 3D seismic programme.

The East Mizzen licensing option acreage lies in water depths of up to 130 metres and covers an area of 1155 square kilometres.