Thermoplastic Production Control Umbilical and ESP Power Umbilicals
The Liuhua 4-1 (LH 4-1) field is located in the South China Sea, approximately 215km from Hong Kong and 240km from Shenzhen. JDR was contracted by the China National Offshore Oil Corporation (CNOOC) to develop subsea production umbilicals and ESP power umbilicals to operate at depths from 260 to 300m. Host production facilities comprise the FPS Nanhai Tiao Zhan and the FPSO Nanhai Sheng Li.
The LH 4-1 oil field includes one production manifold for eight production wells, jumpers and an 18” Subsea Pipeline. JDR supplied three 14km ESP power umbilicals, one 14km main production control umbilical and a bridging manifold control umbilical.
LH11-1 FPS and LH11-1 FPSO were modified to meet LH4-1 production requirements. The development also allows for future expansion of the field with an additional manifold serving up to four additional wells.
Main Thermoplastic Umbilical
The LH 4-1 subsea tieback enabled utilisation of existing facilities with modifications to the FPS. The thermoplastic umbilical was optimized for hydraulic control system response and delivery of required injection chemicals. The cross section was designed with a drag diameter to the weight ratio necessary to meet dynamic mode requirements.
A thermoplastic umbilical solution was selected at FEED to minimise the project cost and maximize system reliability.
ESP Power Umbilical
Each ESP power umbilical contained three x 3 phase power circuits to service the eight wells and provide a complete spare circuit. The use of multi-triad power umbilicals reduced the number of risers, reducing complexity and minimising project cost.
The umbilical bundles were laid up on JDR’s state-of-the-art vertical lay-up machine (VLM). The VLM has a capacity of 60 tonnes per bobbin, which reduced the number of core splices thus reducing risk to the project.
Dynamic Analysis
A significant element of the contract included a dynamic riser design. It was designed by JDR’s in-house riser team, using Orcaflex software for extensive analysis. The JDR design managed a number of challenges including a requirement to model FPS rig movements during workovers of existing LH 11-1 wells directly underneath. The main umbilical and ESP power umbilical risers were optimised to provide fatigue resistance for the design life.
Riser engineering included:
- Tension/angle plots for bend stiffener design
- Calculation of FPS hang-off loads
- TDP location & arc-length
- Distribution of buoyancy modules
- Specifying tension across entire length of riser
- Specifying min/max sag/bend clearance
Umbilical Hardware
JDR’s termination hardware team designed a range of devices. Subsea equipment was designed with stand alone CP for the design life. All hardware and ancillary equipment was designed using the latest 3D CAD software. Fabrication drawings were produced from 3D models.
Hardware delivered included:
- Flexible pull-in heads
- Hang-off bodies and split clamps
- Dynamic bend stiffeners
- Buoyancy modules
- Riser base clamps
- Subsea termination units
Advanced manufacturing and complex loadout
JDR’s advanced Hartlepool facility was chosen for the LH 4-1 project as both products for the LH 4-1 project could be manufactured concurrently to reduce delivery lead time.
This was a complex loadout process as the single carousel had to contain all four umbilicals complete with topside hardware, dynamic bend stiffeners and subsea terminations. JDR’s engineering teams provided detailed packing design while JDR’s loadout team executed a safe and effective loadout. For the loadout a heavy lift vessel fitted with a temporary 2,000 tonne carousel was used to ship the umbilicals to China. Once in country, the umbilicals are transferred to an installation vessel.
Hartlepool is alongside a deep water port with immediate access to North Sea shipping lanes.
To view the case study, please click the following: CNOOC- Liuhua