Oil and gas services group Petrofac reported a strong first half but investors punished the firm for not giving them even more.The company stuck with its prediction of full year net profit growth of at least 15% in 2012.But investors judged the company harshly, pushing shares in the FTSE 100 firm down 4.6% in early trading."Even though earnings per share beat, the market hasn't been told anything positive it didn't already know," said David White, a trader from SpreadEX."Some analysts are citing the number of delayed contracts awarded in Onshore Engineering and Construction as a reason to temper the full year 2013 outlook," he added.Chief Executive Ayman Asfari said over the past few months there had been delays in certain contract tender processes with a number of anticipated awards moving from 2012 into 2013. "Whilst these delays impact the expected level of 2012 new orders for Onshore Engineering & Construction, we continue to expect our strategy to deliver earnings growth in 2013 and beyond," he said. "As a result, we remain confident of achieving our target of more than doubling our recurring group 2010 earnings by 2015."Revenues at Petrofac were up 20% to $3.2bn, with earnings per share up 32% to 94.8c.Pre-tax profits rose to $412.5m, from $300m the year before.Petrofac declared an interim dividend of 21 cents per share, an increase of 20.7% on the first half of 2011.Going forward, the firm said it remained confident of achieving a target of more than doubling recurring 2010 group earnings by 2015.