Rockhopper Regulatory News (RKH)

Embargoed: 0700hrs 30 December 2011

Rockhopper Exploration plc

("Rockhopper" or the "Company")

14/15-4z: Completion of Sidetrack

Rockhopper Exploration plc (AIM: RKH), the North Falkland Basin oil and gas exploration company, is pleased to announce that coring and logging operations at well 14/15-4z have been successfully completed.

The sidetrack well 14/15-4z (approximately 12.5m from the main well bore), was drilled to a total depth of 2555m md. A total 115m of core was cut through the hydrocarbon bearing Beverley, Casper South, Casper and Sea Lion reservoirs bringing the total amount of core cut during the entire drilling campaign to 455m (1493ft).

Drilling of the well has completed the commitments required to earn the 60% interest and operatorship of licence PL004b.

The well will now be plugged and abandoned as planned and a further announcement will be issued when the rig is off hire.

Enquiries:

Rockhopper Exploration plc

Sam Moody - Chief Executive

Tel. +44 (0)20 7920 2340 (via M: Communications)

M: Communications

Patrick d'Ancona or Ben Simons

Tel. +44 (0)20 7920 2347

Canaccord Genuity Limited

Charles Berkeley / Henry Fitzgerald-O'Connor

Tel. +44 (0) 20 7050 6500

Notes to Editors

Rockhopper was established in February 2004 with a strategy to invest in and carry out an offshore oil exploration programme to the north of the Falkland Islands. The Company floated on AIM in August 2005 and holds a 100 per cent. interest in four offshore production licences: PL023, PL024, PL032 and PL033 which cover approximately 3,800 sq. km. Rockhopper has also farmed in (7.5% working interest) to licences PL003 and PL004, which are operated by Desire Petroleum. In addition to the original farm-in, and in consideration for drilling one well on the north-western acreage of licence PL004, known as Area 1, which contains the extension to the Sea Lion field as well as the Beverley, Casper and Casper South features, Rockhopper has farmed-in with operatorship and an aggregate 60% interest in Area 1. Rockhopper has further farmed into the north-eastern part of licence PL004 known as Area 2, which the Company believes contains the "Jayne" prospect and the eastern part of the "Beverley" prospect, with an aggregate 25% interest. Rockhopper has received the necessary regulatory approvals including consent for change of operatorship on licence PL004b (Area 1) which it now operates. These licences have been granted by the Falkland Islands government.

An extensive work programme has been carried out over a number of years on the licences operated by Rockhopper. This has included 2D and 3D Seismic and Controlled Source Electromagnetic Mapping (CSEM). In February 2010, the Ocean Guardian drilling rig arrived in Falkland waters to carry out a multi-well drilling campaign. Rockhopper drilled an exploration well on its Sea Lion prospect during April and May 2010, the result of which was the first oil discovery and Contingent Oil Resource in the North Falkland Basin. The Sea Lion

discovery was successfully tested during September 2010 and June 2011 and was the first oil to flow to surface in Falkland Islands waters. Rockhopper contracted seismic vessels MV Polarcus Asima and Nadia to carry out a 3D seismic survey over areas of licences PL024, PL032 and PL033 which were not previously defined by 3D, as well as adjacent areas. Data over the southern portion of licences PL032 and PL033 has been fast track processed and an initial interpretation has now been completed. The balance of the newly acquired 3D seismic data is still being processed and the Company expects it will be available for interpretation during January 2012.

Rockhopper Exploration plc www.rockhopperexploration.co.uk