- Design review
- Evaluation (technical & commercial) and Support during procurement stage
- Reel lay method development
- Static & Dynamic installation analysis (utilizing standard analytical softwares e.g. OrcaFlex) to determine operational and weather criteria, including installation loads, tension requirement, stress/strain limits, etc.
- Installation vessel & equipment selection – feasibility, capacity and availability
- Installation procedure development depending on field layout / constraints
- Pull-in / Tie-in procedures
- Interface with specialist subcontractors and manufacturers
- Field engineering & operation support
- Pre-commissioning support
- Cost benefits study and estimation, schedule, lay rate
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.. more on cable, umbilical & flexible..
Cable and Umbilical
Cable and umbilical are the life lines of the subsea/ offshore field. They provide electrical power, hydraulics and fibre-optic communications in order to energize, control and enable crucial data exchange between subsea trees and instrumentations between facilities. These are all bundled into the multi-function steel tube umbilical or multiplex cable.
The transportation and installation methods are almost identical to flexible flowlines (transported in reels or transpooled onto carousel) except that most of these have end termination boxes to suit either topside or subsea. These items are mostly long lead and should be handled with care.
Flying leads with special mateable connectors are also used for connection subsea and can be packed onto reel, pallets or coiled in figure “8” deployment frame.
The cable or umbilical will either be pulled-in to the topside via J-Tube or I-tube available on the platform structure. For some cases, the cable or umbilical be pulled-in to the shore side. Depending on the water depth, tidal condition and access, the cable lay anchor barge or vessel will be positioned along the lay route for connection to pull rigging of shore winch.
Cable and umbilical are normally buried after they are being installed using trenching machine. Specialist equipment selection should be done taking into account the reliability and efficiency.
Flexibles are commonly used for subsea tie back to floaters and offer advantages to rigid pipelines especially for dynamic risers application. It is also cost effective as compared to procuring steel pipes form mills in small quantity for short length, small diameter pipeline project. Flexible flowlines are designed based on Client’s project requirements and product properties. These are then manufactured, tested and packed onto reels by specialist vendors in factory environment. The reels are then transported to the site supply base for loading onto the flexible lay vessel.
The flexible flowlines can be loaded onboard based on multiple scenarios:
- Multiple reels can be shipped using Heavy Lift Vessel (HLV) from manufacturer to mobilization base to save installation vessel transit time. These reels can then be loaded onboard installed separately using reel hub drive system or multiple under rollers.
- The multiple reels can be mobilized at site base and then transpooled onto the flexible lay vessel’s carousel
- Flexible lay vessel can sail to manufacturing yard and transpool directly onto the available carousel onboard
- Flexible flowlines are spooled on portable/ liftable carousel, which will then be transported via Heavy Lift Vessel (HLV) and installed onto the flexible lay vessel. Most of the time this scenario applies when the site location is in another region
Flexible lay can be carried out using simple horizontal system (chute) or vertical lay system (lay tower) depending on water depth and lay tension.
Based on field layout design or host platform, the flexible flowlines will have to be installed over Mid Water Arch (MWA), riser support structure or pulled in to via I-tubes/ FPSO turret. For subsea end the flowline may come with bolted flange end termination or diverless connector for tie-in.
Various accessories have to be installed as well including buoyancy modules, uraducts, hold-back tethers, bend restrictors, etc. Handling of the flowlines, terminations and accessories should be planned out carefully to avoid damage which can delay the start up operations.
Also read our special publication on ‘A useful application of vessel motion data in cable installation operations‘