Exploration drilling update

PREMIER OIL PLC

("Premier")

Exploration drilling update

23 April 2013

Oil discovery at Bonneville, UK

Premier is pleased to announce that both the Bonneville exploration well (28/9a-6) and its side track (28/9a-6z) have discovered oil. The Bonneville prospect is located four kilometres south of the Burgman discovery on the Catcher licence in the UK Central North Sea.

The Bonneville well was drilled to a total depth of 4,481 feet true vertical depth subsea (TVDSS). The well encountered a gross oil column of 66 vertical feet in the Tay interval with an estimated net oil pay of 26 feet. The Bonneville well was subsequently sidetracked to the Bonneville East prospect. The sidetrack was drilled to a total depth of 4,441 feet TVDSS and encountered 34 feet of net oil pay in an overall gross oil column of 175 vertical feet in the Tay interval.

The Bonneville discoveries are in excellent quality reservoirs with average porosities of approximately 30 per cent. Initial sampling indicates that the API of the oils in Bonneville is of similar quality to that established at the nearby Burgman discovery which was 25 degrees API.

The estimated oil in place from the Bonneville discoveries is approximately 30 million barrels which is in line with pre-drill predictions. It is anticipated that the discoveries will be tied back to the Catcher field development.

The WilPhoenix rig will now move to the West of Shetland to start development drilling at the Premier-operated Solan project.

Gas discovery at Matang, Indonesia

The Matang-1 exploration well on Block A Aceh (Premier 41.67 per cent equity) in Indonesia has discovered gas and will now be tested.

The Matang-1 well, which has been drilled to a depth of 7,893 feet true vertical depth, penetrated a gross gas column in the Upper Bampo Limestone formation (the primary reservoir target) of at least 90 feet. The base of the gas column has not been encountered.

While drilling the primary reservoir target, losses into the formation and gas influx into the well occurred. As a result, the decision was taken to suspend the well and to test the reservoir interval drilled to date to obtain flow rate and gas quality information.

Premier will provide further information in May once the results of the test are known.

Luno II, Norway

Testing of the Luno II discovery (Premier 30 per cent equity) in Norway has commenced and results are expected before the end of the month.

Simon Lockett, Chief Executive Officer, commented:

"We are delighted with the strong start to our 2013 exploration drilling programme with the previously announced discovery at Luno II and now the discoveries at Bonneville and Matang. We look forward to the outcome of the test programmes at Luno II and Matang while the Bonneville discoveries will be tied back to our important Catcher area development, which is targeted for project sanction by year-end."

Notes to editors

The partners in the Catcher licence are Premier (Operator, 50 per cent), Cairn Energy (30 per cent) and Wintershall (20 per cent).

The partners in Block A Aceh are Medco (Operator, 41.67 per cent), Premier (41.67 per cent) and Japex (16.66 percent).

The partners in PL 359 in Norway are Lundin (Operator 40 per cent), Premier (30 per cent) and Statoil (30 per cent).