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Engineering Case

Power umbilical




Orient designed, manufactured and supplied a 3km, 8.7/15kV 3× 185mm2 power link between theFPSO Nan Hai Fa Xian and the wellhead platform for the HZ21A Oil Project.


HZ21A platform is located offshore the Pearl River Mouth, South China Sea, People's Republic of China, in approximately 106 meters water depth. It is approximately 9km northwest from the existing HZ23-2 platform.


CACT Operators Group was established in 1984 and was put into production in 1990.As an enterprise engaged in offshore oil exploration, development, production, and is the first Chinese offshore oil industry to foreign cooperation bodies. Adhering the advanced management experience and business philosophy of 4 famous international company --

CNNOC, Agip (China)company (renamed for ENI China limited company) and overseas oil limited company Chevron and Texaco China company (two company joined as Chevron Texaco Corporation in 2004) . The company started the crude oil exploration , and development and production jobin Huizhou 16/08 contract area 21years ago and successfully extended the operation area to Huizhou 16/19 block in 1998.

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 25 year design life was achievable. With the exception of the copper tap, 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.

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