Rockhopper Regulatory News (RKH)

Embargoed: 0700hrs 9 August 2011

Rockhopper Exploration plc

("Rockhopper" or the "Company")

14/10-6 Appraisal well update

Rockhopper Exploration, the North Falkland Basin oil and gas exploration company, is pleased to provide an update on the 14/10-6 appraisal well. The third appraisal well on the Sea Lion feature was drilled 4.1km to the west of the 14/10-2 discovery well on licence PL032 (100% Rockhopper) and to a total depth of 2706m (drilled depth).

Sea Lion Main Fan Complex

·; Results at upper end of expectations

·; Well confirms significant reservoir development and hydrocarbon charge within Rockhopper's currently interpreted Sea Lion mid-case area

·; Wireline log analysis indicates Sea Lion main fan net oil pay is 36.4m (119 feet)

·; Gross reservoir interval in Sea Lion main fan is 42m (138 feet) with net to gross of 87%

·; Management interprets this well as confirming Sea Lion main fan is full to spill

·; Reservoir quality good:

- average porosity 21.6%, maximum 28.8%

·; Average Sw (water saturation) 21%

·; No oil water contact observed in the Sea Lion main fan

·; Formation pressure tests indicate reservoir at the well in communication with wells 14/10-2, 14/10-4 and 14/10-5

·; Downhole fluid samples collected confirmed as oil

·; Following this well, the board considers Sea Lion to be commercially viable

Sea Lion Lower Fan Complex

·; Well developed lower sand package (sand B15) intersected beneath oil water contact of -2477m tvdss (total vertical depth subsea) and was water wet with no shows

·; 34m (112 feet) gross reservoir package with 85% net to gross

·; Reservoir quality good:

- average porosity 20%, maximum 25.3%

·; Sand B15 showed significant thickening away from wells 14/10-2 and 14/10-5 as prognosed

·; Formation pressure tests indicate B15 sand to be in pressure communication with the Sea Lion main fan complex giving significant updip exploration potential

·; Deeper thin lower fan sands penetrated in wells 14/10-2 and 14/10-5 showing a separate deeper oil column not developed at this well location

Well 14/10-6 was designed to investigate reservoir and hydrocarbon presence within the Company's mid-case Sea Lion mapped area. 14/10-6 was the first well to penetrate the Sea Lion main fan to the west of the mapped structural low that runs north-south through Sea Lion. The well has been highly successful, proving a thick, high quality reservoir package and a substantial oil column.

Wireline logging operations have been completed. A number of mini DST (downhole Drill Stem Tests) were carried out within the main fan complex and oil was successfully flowed from the main fan. The results will now be interpreted and integrated with other wireline logging data to give an estimate of the potential well productivity. The Company does not consider it necessary to perform a full production test and the well will now be plugged and abandoned.

Once the results of this well have been integrated into the fast-track seismic covering the southern portion of licences PL032 and PL033, a further announcement will be made detailing the seismic interpretation and the implications of well 14/10-6 for management estimates of resources within Sea Lion.

Upon completion of operations on 14/10-6 the Company intends to drill an exploration well 3.3km to the North West of the discovery well 14/10-2, outside of the Sea Lion Discovery Area. The well is designed to investigate the presence of reservoir and hydrocarbon charge towards the northernmost currently mapped extent of the Sea Lion Main fan.

Sam Moody, Chief Executive, commented:

"The results of this well are at the upper end of expectations for the Sea Lion main fan complex and we are delighted to see these oil charged sands extending to the west as prognosed. The thickness and quality of reservoir encountered in the lower fan complex gives additional potential updip."

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 2340

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. 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. The shooting of this seismic has been completed and interpretation is currently underway.

Rockhopper Exploration plc www.rockhopperexploration.co.uk

NB: This statement has been approved by the Company's geological staff who include David Bodecott (Exploration Director), who is a Member of Petroleum Exploration Society of Great Britain (PESGB) and the American Association of Petroleum Geologists (AAPG) with over 30 years of experience in petroleum exploration and management, for the purpose of the Guidance Note for Mining, Oil and Gas Companies issued by the London Stock Exchange in respect of AIM companies, which outline standards of disclosure for mineral projects.