(ShareCast News) - Oil and gas companies Premier Oil and Rockhopper Exploration announced the termination of a joint venture drilling contract with Ocean Rig in the Falklands.They said the termination followed "a number of material operational issues" at the Eirik Raude rig during the term of the contract to date."As a result, Premier will no longer be drilling the Chatham exploration well during the current campaign. However, we are in discussions with the Falkland Islands Government regarding the possibility of drilling this prospect in the future."Rockhopper Exploration, which has interests in the North Falkand Basin and Greater Mediterranean region said the drilling of Chatham well will now be deferred until the Seal Lion pre-development drilling campaign.Rockhopper's chief executive officer Samuel Moody said: "Whilst it is a shame not to be able to drill Chatham as part of this campaign the resources added at the Zebedee location, along with the potentially very significant discoveries in the Isobel/Elaine area, mean that from a sub surface perspective this has been a hugely successful campaign."At 1426 GMT, Premier Oil shares were up 8.3% to 32.22p, while Rockhopper was down 6.7% to 25.43.