Tullow Announces Successful Appraisal of Mahogany-5 Well Offshore Ghana

June 9, 2010

Tullow Oil plc (Tullow) announces that the Mahogany-5 appraisal well has continued the successful appraisal of the area immediately to the southeast of the Jubilee Field offshore Ghana.

The results of drilling, wireline logs and reservoir fluid samples show that the well penetrated a total net oil pay of 23 metres in sandstone reservoirs over a gross interval of 51 metres. Reservoir fluid samples recovered 28-32 degree API oil and pressure data have confirmed reservoir communication with the previously drilled Mahogany-4 well.

Mahogany-5 completes the appraisal of the southeast Jubilee area and follows successes at the Mahogany-3, Mahogany-4 and Mahogany Deep-2 wells. Geoscience and engineering studies are continuing to refine the potential resource range and to advance development planning activities for this area.

The well was drilled by the Atwood Hunter rig to a total depth of 3,988 metres in a water depth of 1,149 metres. The well is located approximately 62km offshore and about 7km southeast of the Mahogany-1 well, the Jubilee discovery well.

The rig will now leave Ghana to work for another operator and will return in the fourth quarter of 2010 on a planned nine-month drilling programme in the West Cape Three Points licence.

Tullow has a 22.896% interest in the West Cape Three Points licence which is operated by Kosmos Energy.

[mappress]

Source: Tullowoil , June 9, 2010: