JDR designed, manufactured and supplied a 2.4 km, 3 x 500mm2 8.7/15(17.5) kV power, optical and chemical injection link between the FPSO Raroa and the wellhead platform for the OMV Maari Field.
Described as the largest undeveloped offshore oil field in New Zealand, the Maari development, operated by OMV (New Zealand) Ltd, is located some 80 km offshore Taranaki, New Zealand in 102m of water. The field holds proven and probable reserves in excess of 50 million barrels of oil. The development includes an unmanned Wellhead Platform (WHP) housing the wellheads of 5 production and 3 injection wells, linked via subsea flowlines to a Floating Production, Storage and Offloading (FPSO) vessel anchored 1.5 km away.
The dynamic section of the umbilical is installed in a lazy-s configuration alongside flexible risers which transfer product from the Well Head Platform to the FPSO. The risers and umbilical then pass over a buoyed mid water arch (MWA) which is tethered to the sea bed. The configuration also includes dynamic bending stiffeners at the FPSO turret J-tube hang off and a hold-back structure at the seabed where the static umbilical section begins. The umbilical static section is installed in a J-tube at the WHP.
Dynamic analysis of the system was performed during the design phase in order to obtain tension and curvature profiles under expected worst-case sea states and to ensure that clashing between adjacent lines was minimal. Additional lead ballast was added to the dynamic umbilical section in order to fine-tune its diameter to weight ratio and match adjacent flowlines and risers.
Based on the tension and bending profiles, additional umbilical fatigue analysis was undertaken to ensure that the required 15 year design life was achievable. With the exception of the lead ballast, a solution was provided where both the dynamic and static umbilical armoured sections were identical and continuous eliminating the need for a transition between the two sections. Special hose liner was used to accommodate a design temperature forseen within the turret of 90°C.
The hoses within the bundle are used for chemical transportation and design life compatibility with the liner at this temperature was a key parameter for the project team. JDR continuously develops advanced hose liners capable of withstanding increasingly demanding conditions.. The requirement for diverless installation also presented unique challenges for the umbilical termination designs. In particular, the bend stiffener at the FPSO turret J-tube required a special automatic latching mechanism.