Petrofac was the best performing blue-chip stock on Monday morning after the oil fabrications giant reported results that were ahead of expectations.In mid-December the company had indicated that net income for 2009 would be at least $330m and it comfortably beat that figure with net income of $353.6m.Last week the company announced plans to hive off its UK Continental Shelf assets into a new company, EnQuest, to be formed with Swedish oil and company Lundin Petroleum.Oriel Securities has retained its 'add' recommendation after the results, having previously argued that the EnQuest deal would lead to an 'upward re-rating' as a result of lower exposure to exploration and production. The broker thinks the shares will hit a range of 1000p - 1050p once the EnQuest deal goes through.Evolution Securities takes a more lukewarm view and thinks investors should wait until the demerger takes place before considering whether to invest. It has a 'neutral' rating on the stock.