Sidetrack to Erne discovery, UK North Sea

PREMIER OIL PLC

("Premier")

Sidetrack to Erne discovery, UK North Sea

23 December 2011

As announced by Antrim Energy Inc, Premier notes the preliminary results of the Erne discovery well sidetrack, 21/29d-11Z, in the UK Central North Sea (Premier 50 per cent working interest.)

The 21/29d-11Z well, designed to appraise the Erne oil discovery in the Eocene Tay Formation, was drilled up-dip of the discovery location to a total depth of 5,142 feet. The sidetrack encountered approximately 24 feet of net oil pay and 14 feet of net gas pay in a high quality sandstone reservoir. Initial interpretation is that the 21/29d-11Z well has penetrated a separate accumulation from that in the 21/29d-11 discovery well, but further work is necessary to confirm this. The 21/29d-11Z well will now be suspended for potential future re-entry and use in the development of the Erne discovery.

Erne is situated between the Premier-operated Fyne field and the West and Northwest Guillemot fields. The East Fyne Appraisal well, which is located approximately three kilometres from the Erne discovery, is expected to spud later this month.