Tullow Oil

Onyina-1 exploration well finds water bearing reservoirs

Press Release   •   Oct 21, 2010 10:11 BST

21 October 2010 - Tullow Oil plc (Tullow) announces that the Onyina-1 exploration well in the Deepwater Tano licence offshore Ghana encountered water bearing reservoirs.

The Onyina-1 well was drilled to explore a large, high-risk, Campanian prospect between the Tweneboa and Jubilee fields in the northeast of the Deepwater Tano Licence. It intersected 49 metres of good quality sandstone reservoir, on prognosis, however they were water bearing at this location.

The Sedco-702 dynamically positioned semi-submersible rig drilled Onyina-1 to a total depth of 2,730 metres in water depths of 828 metres. On completion of operations, the rig will move to the Jubilee Unit to assist in the preparations for first oil later in 2010.

Tullow (49.95%) operates the Deepwater Tano licence and is partnered by Kosmos Energy Ghana (18%), Anadarko Petroleum (18%), Sabre Oil & Gas (4.05%) and the Ghana National Petroleum Corporation (GNPC) (10% carried interest).

Commenting today, Angus McCoss, Exploration Director, said:

"The negative test of the Campanian reservoirs in the Onyina prospect enables further refinement of our exploration and relinquishment strategy offshore Ghana. Good quality Campanian reservoir sands were found as predicted, however the lack of hydrocarbons at this location highlights the high risks of charging and trapping oil in this secondary play.

Our main focus remains on the lower risk primary play, the deeper more prospective Turonian reservoirs, where we have had such outstanding success with Jubilee, Tweneboa and Owo."

FOR FURTHER INFORMATION CONTACT:

Tullow Oil plc
(+44 20 8996 1000)
Angus McCoss
Chris Perry
James Arnold    Citigate Dewe Rogerson
(+44 207 638 9571)
Martin Jackson
George Cazenove Murray Consultants
(+353 1 498 0300)
Joe Murray
Ed Micheau


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 100 Index. The Group has interests in over 85 exploration and production licences across 22 countries and focuses on four core areas: Africa, Europe, South Asia and South America.

In Africa, Tullow has production in Gabon, Côte d'Ivoire, Mauritania, Congo (Brazzaville) and Equatorial Guinea and two large appraisal and development programmes in Ghana and Uganda. Tullow also has exploration interests in Gabon, Côte d'Ivoire, Liberia, Sierra Leone, Mauritania, Senegal, Congo (DRC), Tanzania, Madagascar, Namibia and Angola.

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 area. The company also has interests offshore the Netherlands.

In South Asia, Tullow has exploration and production in Pakistan and Bangladesh. In South America, Tullow has exploration interests in Guyana, French Guiana and Suriname.

For further information please refer to our website at www.tullowoil.com <file://www.tullowoil.com> .