London-based oil explorer Tullow Oil Plc confirmed a recent discovery in Ghana was the firm's largest ever.

"The Mahogany well in Ghana has provided the group's largest ever discovery," Chief Executive Aidan Heavey said.

The company added it planned to divert investment from its UK base to more promising African fields, after success with the Mahogany well in Ghana and increased optimism about its Ugandan assets.

HIGHLIGHTS Exploration --

Ghana - Mahogany discovery - recent technical work indicates that there is significant further upside potential above current market estimates and a material proportion of the trap is within the Deepwater Tano block.

Accelerated Ghana program - the Belford Dolphin drill ship has been secured to drill a further well in the Deepwater Tano block in August this year.

Ghana

The high impact Mahogany-1 exploration well offshore the Republic of Ghana was drilled to a total depth of 3,826m. The well, which represents the largest ever discovery offshore Ghana, has been suspended for potential re-entry and the drill ship moved off location on June 29.

The well has discovered a significant accumulation of 37º API oil in a large stratigraphic trap which straddles both the West Cape Three Points (Tullow 22.9%) and Deepwater Tano Blocks (Tullow 49.95%). The well has encountered a gross hydrocarbon column of 270m and net stacked pay of 95m and did not encounter a definitive oil-water contact. Pressure and sampling data from the well indicates that a production well at this location would be capable of flowing in excess of 15,000 bopd.

Since the initial discovery, additional technical work has been undertaken to tie the well data to the 3D seismic data that covers both blocks. Remapping the trap, incorporating the well data and calibrating a pronounced seismic amplitude anomaly indicate that there is the likelihood of significant further upside potential and that a material proportion of this accumulation is likely to be located within the Deepwater Tano block.

The discovery now needs to be appraised with further drilling and the joint venture plans to accelerate the program by securing the Belford Dolphin drill ship to drill a well in the Deepwater Tano block this August. Further drilling activity is also under consideration on both the West Cape Three Points and Deepwater Tano blocks for later in the year.

Tullow is also investigating the follow-on potential in the region. Technical work is ongoing to understand the implications of the Mahogany discovery for numerous other prospects in both blocks already identified on 3D seismic. The prospects will then be considered for inclusion in a campaign for this region in 2008.

Elsewhere in Ghana, an appraisal well on the North Tano (Tullow 31.5%) oil/gas discovery on the Shallow Water Tano license is planned for August.