PCI.L Regulatory News (PCI)

Petroceltic International plc

Drilling update on AT-5z Horizontal Section

Petroceltic International plc ("Petroceltic" or "the Company"), the upstream oil and gas exploration and production company focused on the Middle East, North Africa and the Mediterranean, is pleased to announce that well AT-5z has completed drilling at a total depth of 2421 metres along hole, and has a horizontal section in the main Ordovician reservoir of 376.5 metres. Good gas shows have been encountered throughout the reservoir section.

The horizontal section will now be evaluated by drillpipe conveyed logging tools. A multi-stage completion will be run on completion of the logging. The company expects to suspend the well for testing by 24th May 2011, with test results expected in June.

Press Enquiries to:

Brian O'Cathain/ Alan McGettigan, Petroceltic International Tel: +353 (1) 421 8300

Philip Dennis/Jenny Renton, Pelham Bell Pottinger Tel: +44 (20) 7861 3919

Joe Murray / Joe Heron, Murray Consultants Tel: +353 (1) 4980300

Hugh McCutcheon / John Frain, Davy Tel: +353 (1) 679 6363

Dr. Dermot Corcoran, Head of Exploration, Petroceltic International plc, is the qualified person who has reviewed and approved the technical information contained in this announcement. Dr. Corcoran has a B.Sc in Geology, a M.Sc. in Geophysics, and a Masters degree in Business Administration, all from the National University of Ireland, Galway. He also holds a Ph.D in Geology from Trinity College, Dublin. Dr. Corcoran has over 20 years experience in oil & gas exploration and production, and has previously worked at ExxonMobil, the Petrofina Group, and Statoil.

Notes to Editors:

Petroceltic International plc is a leading Upstream Oil and Gas Exploration and Production Company, focused on the Middle East, North Africa and Mediterranean area, and listed on the London Stock Exchange's AIM Market and the Irish Sock Exchange's ESM Market. The Company has exploration assets in Algeria, Tunisia and Italy. Petroceltic is in a unique position in Algeria, operating a significant licence in partnership with Sonatrach the state oil company, one of only two AIM listed companies to enjoy this position.

The Ain Tsila discovery was made by Petroceltic in 2009 and was reported by IHS/Herold as the 10th largest discovery made worldwide in 2009.

A diagram depicting the location of the AT-5 and AT-5Z well location within the Isarene permit in included as slide 24 of the "oil barrel" presentation on the company's website, www.petroceltic.ie.