Plexus, the specialist oil and gas wellhead engineer, says new contract wins and repeat business from old customers drove profits in the six months to the end of December.Turnover increased 24% over the period of 2010 to £9.3m, while earnings before interest, tax depreciation and amortisation (EBITDA) grew 17% to £3.0m. Profits before tax increased 33% to £1.5m. The interim dividend has been increased by 11.4% to 0.39p per share.Since the year end Plexus has raised £6.2m in a share placing.Plexus is now aiming to produce a new type of subsea wellhead, to build on the success of its "friction-grip" land based system.The group's Chief Executive, Ben van Bilderbeek said: "there is an increasing recognition that Plexus has the potential to become a leading specialist oil and gas wellhead services company that will offer a new wellhead standard for surface and in time, subsea applications."Shares in the firm had gained 5.3% by 10:08; the stock is now 59.7% up on the start of the year.BS