Operations Update

Tullow Oil PLC 06 May 2008 News release Operations Update - Successful Mahogany-2 appraisal well 6 May 2008 - Tullow Oil plc (Tullow) announces that the Mahogany-2 well, which is being drilled to appraise the Jubilee field offshore Ghana, has intersected a significant column of light oil. Results of drilling, wireline logs and samples of reservoir fluid, indicate that Jubilee is a single continuous stratigraphic trap extending at least 11km to the Hyedua-1 discovery well in the adjacent Deepwater Tano licence. Mahogany-2, which lies in the West Cape Three Points licence, is the first appraisal well on the Jubilee field and is targeting the Turonian turbidite sandstones encountered in the Mahogany-1 and Hyedua-1 discovery wells. The well has encountered a gross reservoir interval of 243 metres, containing 63 metres of high quality stacked reservoir sandstones, and net hydrocarbon-bearing pay of 50 metres. Results of logging and pressure testing indicate that the combined hydrocarbon columns are in excess of 600 metres. Analysis of the oil samples from the Mahogany-1 discovery well had suggested the potential for a gas cap at the Mahogany-2 location. No gas cap has however been encountered in this well thereby indicating the potential for the Jubilee field to extend further up-dip of this location. A limited flow test will now commence on Mahogany-2 to determine potential production rates from these excellent quality reservoirs and to collect further oil samples for analysis. Testing is expected to take approximately four weeks and the well will then be suspended for use as a potential development well. Mahogany-2 has been drilled to a total depth of 3,443 metres by the Songa Saturn drillship in water depths of 1,080 metres. Three more Jubilee appraisal wells are planned for 2008 and will be drilled by the Blackford Dolphin semi-submersible. The next Jubilee appraisal well, Hyedua-2, is expected to commence in July in the adjacent Deepwater Tano licence in which Tullow has a 49.95% interest. Tullow has a 22.9% interest in the West Cape Three Points licence. Other partners include Kosmos Energy (Operator 30.875%), Anadarko Petroleum (30.875%), the E.O.Group (3.5%), Sabre Oil & Gas (1.854%) and the Ghana National Petroleum Corporation (GNPC) (10% carried interest). Tullow is the Unit Operator of the Jubilee field. Commenting today, Aidan Heavey, Chief Executive of Tullow said: 'The confirmation that Mahogany-2 is in communication with both Mahogany-1 and Hyedua-1, reinforces our interpretation that Jubilee is a major discovery and is likely to lead to a material upgrade of current resource estimates. We will continue our appraisal and development programme over the remainder of 2008 with the overall objective of achieving first production in 2010.' For further information contact: Tullow Oil plc Citigate Dewe Rogerson Murray Consultants (+44 20 8996 1000) (+44 20 7638 9571) (+353 1 498 0300) Aidan Heavey Martin Jackson Joe Murray Tom Hickey Kate Delahunty Ed Micheau 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 100 Index. The Group has interests in over 100 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. The company also has interests offshore the Netherlands and Portugal. In Africa, Tullow has exploration and production in Gabon, Cote d'Ivoire, Mauritania and Equatorial Guinea and two large appraisal and development programmes in Ghana and Uganda. Tullow also has exploration interests in Mauritania, Senegal, Congo (DRC), Tanzania, Madagascar, Namibia and Angola. 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 and Suriname. For further information please refer to our website at www.tullowoil.com This information is provided by RNS The company news service from the London Stock Exchange

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