Rockhopper Regulatory News (RKH)

Embargoed: 0700hrs 11 October 2011

Rockhopper Exploration plc

("Rockhopper" or the "Company")

14/10-8 Exploration Well Update

&

Prospective Resource Update

Rockhopper Exploration plc (AIM: RKH), the North Falkand Basin oil and gas exploration company, provides the following update on the 14/10-8 exploration well (the "Well").

The Well was designed to investigate reservoir and hydrocarbon presence within the Sea Lion Main Complex ("SLMC") in an area with relatively low amplitudes, and was also an exploration well on both the Casper and Kermit prospects.

·; Casper, SLMC and Kermit sands encountered

·; Good quality thick reservoir packages encountered in all three targets, however all sands were water wet and the well is a dry hole

·; Significant 123m (404 ft) total gross reservoir package

o Casper

§ 42m gross (138 ft)

§ 63% net to gross

§ Average 19% porosity (maximum 27%)

o SLMC

§ 19m gross (62 ft)

§ 98% net to gross

§ Average 27% porosity (maximum 31%)

o Kermit

§ 62m gross (203 ft)

§ 82% net to gross

§ Average 15% porosity (maximum 24%)

·; New depth conversion indicates uplift in potential resources

The Company believes that the Well penetrated a relatively restricted area of the SLMC that appears to be separated from the rest of the SLMC by the fault to the north. The thickness of the reservoir encountered in the well has increased the Company's confidence that good quality reservoir is likely to be present in other relatively low amplitude areas within the SLMC.

Prospective Resource Update

Following wells 14/10-6 and 14/10-7 the Company has undertaken a review with its technical consultants and as a result has refined its methodology for the depth conversion of seismic data over Sea Lion. This revised method proves an improved fit to all of the wells and provided an accurate prediction from 14/10-8. It also brings an increase in gross rock volume above the OWC within the SLMC.

In addition, the results of wells 14/10-7 and 14/10-8 have successfully demonstrated that the reservoir is well developed outside the areas of high amplitudes, therefore increasing the areal extent of the low and mid case for the SLMC post well 14/10-8 even though 14/10-8 itself proved to be water wet.

Using these new data points and taking account of the relatively small area the Company believes was proven water wet by 14/10-8, new management estimates, which have been reviewed by the Company's external technical consultants, for oil initially in place within the SLMC, on Rockhopper's 100% owned acreage, are shown below:

The Company also believes that potential of 90 mmbbls remains in the Casper prospect to the west of the structural saddle.

The Well will now be plugged and abandoned as planned. The Ocean Guardian drilling unit will then drill well 14/10-9 which is located approximately 5.9 km to the south west of the 14/10-2 discovery well. The well is designed to investigate reservoir presence and hydrocarbon charge within the SLMC towards the southern edge of the Company's acreage and is also an exploration well on the Eastern side of the Casper prospect. A further announcement will be made on spudding of the well.

Sam Moody, Chief Executive, commented:

"14/10-8has provided us with further valuable information regarding Sea Lion although its main targets proved to be water wet. We continue to make progress in refining our view of the field's full potential and the optimal ways to both finance and develop it."

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. 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 before the end of 2011.

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.

mmbbls: million barrels

STOIIP: stock tank oil initially in place