Investec has reiterated its buy rating on oilfield services giant Petrofac, following the group's pre-close trading update in which it said it expects to deliver like-for-like (LFL) profit growth in 2011 of at least 20%."Petrofac continues to make good progress on all fronts and we maintain our positive stance on the stock. Into the medium term the newly-created Integrated Energy Services (IES) division could offer meaningful growth and returns, within five years this segment could become as large as the whole group was during FY10, in our view."The broker says that while the order book may have "unwound" slightly (from $10.8bn in September to $10.6bn expected at the end of the year), it remains relaxed given the strong revenue visibility for Petrofac's engineering and construction acitivities.The target price of 1,705p and other forecasts are put under review until a conference call with the firm.The stock was among the best performer of the day on Tuesday, rising 5.39% to 1,447p by 12:33.BC