Oilfield services group Petrofac rebounded on Friday, a day after heavy falls on concerns about guidance at its investor day on Thursday. "Having hit a two-year low yesterday on rumours that management was reducing long-term earnings forecasts, Petrofac has been besieged by bargain-hunters this morning," said Brenda Kelly from IG.Oil companies Royal Dutch Shell and BHP Billiton were also top risers on the FTSE 100.London Stock Exchange Group gained after Bank of America Corp. Merrill Lynch upgraded its rating to 'buy' from 'neutral'.RSA Insurance Group continued its decline; the stock has been under pressure over recent weeks after it highlighted "issues" relating to the firm's Irish operations.BAE Systems dropped from an a spike earlier in the week on the news that it had opened a titanium machining facility in Edinburgh Parks, South Australia, to support its involvement in the Lockheed Martin F-35 global supply chain.Marks and Spencer slumped after Credit Suisse said it seems very unlikely that the retailer will meet demanding forecasts in the upcoming quarter.FTSE 100 - RisersPetrofac Ltd. (PFC) 1,198.00p +3.99%Royal Dutch Shell 'B' (RDSB) 2,155.50p +2.84%London Stock Exchange Group (LSE) 1,618.00p +2.28%Royal Dutch Shell 'A' (RDSA) 2,058.00p +2.21%Persimmon (PSN) 1,179.00p +2.17%BHP Billiton (BLT) 1,854.50p +2.15%BT Group (BT.A) 371.90p +2.00%Aviva (AV.) 420.80p +1.96%British Sky Broadcasting Group (BSY) 805.00p +1.96%Mondi (MNDI) 954.50p +1.65%FTSE 100 - FallersRSA Insurance Group (RSA) 101.50p -1.55%BAE Systems (BA.) 412.20p -1.32%Burberry Group (BRBY) 1,482.00p -1.27%Centrica (CNA) 328.40p -1.20%Reckitt Benckiser Group (RB.) 4,777.00p -1.20%International Consolidated Airlines Group SA (CDI) (IAG) 359.00p -1.10%Whitbread (WTB) 3,508.00p -1.07%Marks & Spencer Group (MKS) 469.60p -0.99%Admiral Group (ADM) 1,200.00p -0.83%Next (NXT) 5,440.00p -0.55%RD