Perenco UK is expanding operations at the Trent field complex in the UK southern gas basin. This month, a new unmanned gas compression platform was due to be bridge linked to Trent’s existing production installation. Keppel Verolme built the new facility at its yard in Rotterdam - previously, the company was better known for conversions, repairs, and modifications to drilling rigs, pipelay barges, and other floaters.
Tony Chong Heong, COO of the parent company Keppel O&M, said this job signified a successful re-entry for Keppel Verolme (formerly known as Verolme Botlek) into the offshore new construction market.
The new Trent platform is known as the Mobile Offshore Application Barge (MOAB). Consultants Overdick in northern Germany performed the basic design and detail engineering, with Tribon software applied for detailed fabrication engineering. The MOAB is a self-installing facility, allowing Perenco UK to transport the platform to its location in 48.6 m of water, without the need for a heavy offshore construction barge. Overdick’s design has proven suitable for multiple relocations during the platform’s operational life. Two others are in service currently for Talisman offshore Malaysia.
Main advantages of the MOAB are:
• Low cost relocation using the reversed suction operation to float free from the seabed
• Temporary strand jack system provided on a rental basis
• Topsides fully installed and pre-commissioned prior to float-out to offshore location
• Economic both in terms of re-use and final decommissioning.
Keppel Verolme has assembled the 500 tonne steel hull, and the legs and suction cans (1,500 tonne of steel in total) in a dry-dock. The hull was placed on a special dock block arrangement, allowing erection of the legs, fitted with suction cans, from a horizontal to a vertical position. The hull was then connected in the lower position to provide buoyancy during float-out.
Following un-docking and shifting afloat to a deepwater quayside, Keppel Verolme personnel outfitted the MOAB with the Perenco-supplied Solar gas compressors and process package. The platform, with its 900 tonne payload, is designed for 100-year return storm conditions.
Keppel Verolme built the self-installing MOAB platform in its yard in Rotterdam.
For the installation, the MOAB will employ a temporary lifting (strand jack) system to lower the legs to the seabed and to elevate the hull’s main deck to the required level above the sea surface. Rotterdam-based Smit, the transportation and installation contractor, will then insert ‘super bolts’ in place of the strand jacks and clamps to connect the hull and substructure at the correct elevation. Suction piles have been set to achieve the required foundation fixation. The operation will be reversed for future removal or relocation of the platform.
The MOAB’s hull is self-floating with the substructure attached. Its four pre-installed legs will be connected to the hull. These legs have a main outer diameter of 2 m, are braced underwater, and are supported on suction piles.•
