Topside travels

The North Sea platform reuse opportunity was exemplified by Perencos removal of the UK southern North Sea Welland 53/4a platform and the reappearance of its refurbished topsides earlier this year on another of the operators structures, Sanaga 01, offshore Cameroon, in shallow coastal waters.

German naval architect and offshore engineering consultant Overdick was contracted as Perencos project partner for both the Welland and Sanaga projects, having earlier earned its North Sea special solution spurs with the innovative mobile offshore application barge installed alongside the existing Trent fixed production platform, also for Perenco (OE November 2005). The Welland topsides and jacket were both removed in January 2011 and transferred to shore (OE April 2011).

Following refurbishment by Hoondert in the Netherlands, the topsides headed for West Africa on the hull of another of Overdicks innovative self-installing leg barges. The Sanaga 01 module, with its elevated hull supporting an 1800t wellhead platform, was eventually installed in 17m of water offshore Cameroon in April this year.

According to Overdick, the Sanaga facility, which has three conductors, is the first mobile offshore application barge designed with four individual legs, its foundation being created by soil penetration under platform self-weight.

The platform suspension is realised by an arrangement of heavy-duty threaded rods and anchor chains, explains Overdick managing director Klaas Oltmann.