Isobel Deep Oil Discovery

Rockhopper Exploration plc

"Rockhopper" or the "Company"

Drilling update - Isobel Deep oil discovery

Rockhopper Exploration plc (AIM: RKH), the oil and gas exploration and production company with interests in the North Falkland Basin and the Greater Mediterranean region, is pleased to provide the following update on the Isobel Deep Exploration well 14/20-1 (the "Well").

Rockhopper Exploration is pleased to announce an oil discovery at the Isobel Deep exploration well 14/20-1 in the North Falkland Basin, approximately 40km south of the Sea Lion field.

The Isobel Deep exploration well has been drilled to a depth of 2527m having penetrated the top of the target reservoir 2m higher than prognosis at 2503m. The bottom 24m of the Well consists of oil bearing F3 (Isobel Deep) sands. These sands were at a higher than expected reservoir pressure and this resulted in an influx of fluid (oil) into the Well. As part of the operations to remove the influx, oil was recovered at surface from the Well and appears similar in nature to Sea Lion crude. LWD ("Logging While Drilling") data collected over the first 12m of the reservoir and cuttings data to the base of the Well comprising oil stained sandstones also confirm the Well as an oil discovery.

As a result of the new geological information it has been decided to suspend operations on the Well before the planned Total Depth has been reached and to release the rig to drill in the South Falkland Basin. The Well has currently penetrated approximately one third of the mapped sand thickness at the location. The rig is expected to return to continue operations in the North Falklands Basin in August. 

Sam Moody, CEO, commented:-

"Following the discovery at Zebedee we are delighted to have made another discovery in this North Falkland Basin exploration campaign. Having retained the sub-surface lead for North Falkland Basin exploration in the farm out to Premier in 2012, I am delighted to report that our exploration team now enjoys a success rate of 9 out of 11 wells in licences PL004 and PL0032. Isobel represents a new play and significantly de-risks the entire Isobel / Elaine fan complex confirming the presence of an oil prone hydrocarbon system with moveable oil in the Isobel Deep reservoir."

Although the Well has not yet reached Total Depth the signs for the Isobel/Elaine complex so far are very encouraging and we will decide the next actions in appraising the discovery over the coming weeks while the rig is drilling to the south of the Falkland Islands."

Enquiries

For further information, please contact:

Rockhopper Exploration plc

Tel: (via Vigo Communications) - 020 7016 9571

Sam Moody - Chief Executive

Fiona MacAulay - Chief Operating Officer

Stewart MacDonald - Chief Financial Officer

Canaccord Genuity Limited (NOMAD and Joint Broker)

Tel: 020 7523 8000

Henry Fitzgerald-O'Connor

Liberum Capital (Joint Broker)

Tel: 020 3100 2227

Clayton Bush

Vigo Communications

Tel: 020 7016 9571

Peter Reilly

Patrick d'Ancona

Note regarding Rockhopper oil and gas disclosure

This announcement has been approved by Rockhopper's geological staff who include Fiona MacAulay (Chief Operating Officer), who is a Fellow of the Geological Society of London and a Member of the Petroleum Exploration Society of Great Britain and American Association of Petroleum Geologists with over 25 years of experience in petroleum exploration and management, and who is the qualified person as defined in the Guidance Note for Mining, Oil and Gas Companies issued by the London Stock Exchange in respect of AIM companies. In compiling its resource estimates, Rockhopper has used the definitions and guidelines as set forth in the 2007 Petroleum Resources Management System approved by the Society of Petroleum Engineers.