JDR engineered, manufactured and supplied the dynamic catenary umbilical systems for two major projects located offshore China in the Bohai Bay oil field development around 160 km east of Tianjin.
Custom-designed production umbilicals, injection and chemical umbilicals in combination with integrated electro-optic transmission cables were installed on both the CFD 11 oil field, operated by Anadarko Petroleum, and BZ 25, operated by CNOOC/Chevron.
Both projects represent innovative engineering and product development of dynamic, high technology umbilical and cable systems.
These systems provided the vital connection between the Floating Production, Storage and Offloading (FPSO) vessels and the fixed tower Wellhead Platforms. JDR’s dynamic catenary umbilicals were supplied to APL Norway for installation on both the CFD 11 oil field, operated by Anadarko Petroleum, and BZ 25, operated by CNOOC/Chevron. Production flows to the FPSO via flexible jumpers while power and water injection are exported from the vessel to the platforms via two 8MW subsea cables for the power and a 16in line for injection.
CATENARY UMBILICALS AND CABLES DESIGN OVERVIEW
The JDR cables form the dynamic portion of an electro-optical network used to transmit medium voltage power and communications from the FPSO to the wellhead platforms. Multiple cables were provided for each SYS with power and signal components grouped into separate umbilicals. JDR designed and fitted mechanical terminations on individual cables to facilitate hook up to the FPSO and SYS.
The innovative design of the mechanical terminations enabled efficient umbilical pull-in and hang-off. Umbilical tail lengths as long as 18 metres were routed to the SYS slip rings and special protection clamps were placed over the umbilical jackets to prevent excess wear during dynamic motion over the chutes. Large bend strain reliefs (BSRs) were attached to the base of the mechanical terminations in to provide a smooth bend transition to the armored umbilical section.
JDR performed current rating calculations for each medium voltage circuit; the umbilical for CFD 11 had a nominal operating voltage (Uo) of 10.5 kV, while the umbilical for BZ 25 had a nominal operating voltage rating (Uo) of 26.8 kV. The phase conductors were insulated with EPR and a triple extrusion process was used for simultaneous application of the conductor screen, insulation and insulation screen.
DYNAMIC CATENARY ANALYSIS
During the engineering design phase for both projects, dynamic catenary analysis was performed by APL prior to installation to ensure that the JDR umbilicals would not clash with adjacent flexible risers during extreme weather conditions. The analysis was based upon 100 year typhoon conditions with 5 metre significant wave heights. Component fatigue and reliability were key factors driving umbilical and termination design, ensuring the products achieved optimum performance from day one and throughout their design life.