Tullow Oil Plc — Significant Oil Discovery Offshore Ghana

LONDON, June 18 /PRNewswire/ — Tullow Oil plc (Tullow) announces that the high impact Mahogany-1 exploration well drilled on the West Cape Three Points licence offshore the Republic of Ghana has discovered a significant light oil accumulation based on the results of drilling, wireline logs and samples of reservoir fluid.

The well, which is drilling in water depths of 1,320m, has been drilled to a depth of 3,683m and has to date, encountered a gross hydrocarbon column of 270m with 95m of net stacked pay. It is planned to drill to a total depth of approximately 4,200m to test further prospective horizons. Upon reaching the target depth, the well will be suspended pending further evaluation and additional appraisal drilling will be required. The Mahogany-1 well will be tested at a later date as part of the appraisal programme.

The Mahogany discovery, a Santonian turbidite stratigraphic trap, opens a new play fairway in the Tano Basin. The structure straddles both the West Cape Three Points and Deepwater Tano licences in which Tullow has interests of 22.9% and 49.95% respectively. Tullow is also the operator of the Deepwater Tano licence.

The Mahogany-1 well was drilled using the “Belford Dolphin” – a dynamically positioned fifth-generation deepwater drillship. This is the first exploration well to be drilled under the West Cape Three Points seven- year exploration agreement and follows a 1,076 sq km 3D seismic survey on the block in 2005.

Commenting today, Aidan Heavey, Chief Executive of Tullow said:

“The discovery of oil in the Mahogany well represents a major event for the Republic of Ghana and for Tullow. Based on evidence to date, ultimate reserves are likely to be materially in excess of previous estimates, with some high-potential zones still to be drilled. We look forward to working with our partners to realise the full potential of Mahogany and our additional prospects in the region”

Conference CallAidan Heavey (CEO) will host a conference call at 9.30 a.m. GMT today. Please dial-in 10 minutes before the start time. A replay facility will be available from 1pm. The details for accessing the live call and the replay are as follows:

               Live Event                   Replay Facility available from                                                      1 pm GMT    UK Participants      020 7806 1950    UK Participants      020 7365 1827   Irish Participants    01 655 8885     Irish Participants    01 659 8321   Other Participants  +44 20 7806 1950  Other Participants  +44 20 7365 1827                                            Access Code          2405197#   

Aidan Heavey (CEO) will also host a conference call for North American followers at 11:00 a.m. (EDT) today. Please dial-in 10 minutes before the start time. A replay facility will be available from 12 pm (EDT). The details for accessing the live call and the replay are as follows:

       Live Event (11:00am EDT)              Replay Facility available                                                  from 12pm (EDT)    US Participants  +1 480 629 9564     US Participants   +1 303 590 3030                                          Access Code         3748790#    For further information contact:   Tullow Oil plc (+44 20 8996 1000)   Aidan Heavey   Tom Hickey   Chris Perry    Notes to Editors  

Tullow is a leading independent oil & gas, exploration and production group, quoted on the London and Irish Stock Exchanges (symbol: TLW) and is a constituent of the FTSE 250 Index. The Group has interests in over 120 exploration and production licences across 23 countries and focuses on four core areas: Europe, Africa, South Asia and South America.

Tullow’s European interests are primarily focused on gas in the UK Southern North Sea where it has significant interests in the Caister-Murdoch System and the Thames-Hewett areas and operates over 70% of its production.

In Africa, Tullow has exploration and production in Gabon, Cote d’Ivoire, Congo (Brazzaville), Mauritania and Equatorial Guinea and a large gas field development and appraisal programme in Namibia. Tullow also has exploration programmes in Mauritania, Senegal, Cameroon, Uganda, Congo (DRC), Tanzania, Madagascar, Angola and Ghana.

In South Asia, Tullow has exploration and production in Pakistan and Bangladesh and high impact exploration activities in India.

In South America Tullow has high impact exploration interests in Trinidad and Tobago, French Guiana, Suriname and the Falkland Islands.

For further information please refer to our website at http://www.tullowoil.com/

Tullow Oil plc

CONTACT: Aidan Heavey, Tom Hickey or Chris Perry, +44 20 8996 1000, allof Tullow Oil plc

Web site: http://www.tullowoil.com/