- Design review
- Evaluation (technical & commercial) and Support during procurement stage
- Pipelay method selection and development (S-Lay, J-Lay, Reel-Lay or Tow)
- Static & Dynamic pipelay analysis (utilizing standard analytical softwares e.g. OFFPIPE, OrcaLay, MSC PipeLay) to determine operational and weather criteria, including installation loads, tension requirement, stress/ strain limits, etc.
- Installation vessel selection – feasibility, capacity and availability
- Pipelay procedure including initiation methods and sequence (bowstring, horizontal hang-off, Dead Man Anchor, Pile, Sheave, Shore Pull, mid-point tie-in, etc.) depending on field layout/ constraints
- Spool / Riser / Jumper Tie-in method: Diver or diverless connection
- Interface with specialist subcontractors required for welding, Field Joint Coating (FJC), NDT and Engineering Critical Assessment (ECA)
- Field engineering & operation support
- Pre-commissioning support
- Cost benefits study and estimation, schedule, lay rate
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.. more on rigid pipelay ..
Rigid pipelines are the main conduits of offshore fields in order to transport the hydrocarbon products or for water/gas injection to boost production. These pipelines can connect between surface platform to platform (via riser), subsea tie back to platform/ floating system or even to onshore facilities.
These are the few installation methods used in the industry:
- S-Lay: this is most commonly used for shallow water pipelay (from shore pull) to intermediate water depth (200 m) and can be utilized in steep S-Lay configuration up to deep water above 2000 m. This depends on the installation vessel’s design (anchor barge or DP vessel), thruster capacity, tensioner capacity and stinger design.
- J-Lay: this is a specialized method because a custom built J-Lay Tower is required. J-Lay can offer alternative solutions for deep water field development as the J shape catenary has no overbend; thus lower tension capacity is required. The pipe joints are then pre-welded onshore/ offshore (off critical path) as double, triple, quad or hex joints to increase productivity. J-Lay method also offers advantage for handling large subsea PLETs/ mid line structures/ Steel Catenary Riser (SCR) with flex/ stress joints without going through S-Lay firing line.
- Reel Lay: this method was first invented for transporting fuel supply across the English Channel during World War II. It offers high lay rate as the “stalks” or “strings” are pre-fabricated at onshore spool base (off vessel critical path) and then reeled onto the reel lay vessel. The reel lay vessel will then sail to site for pipelay and needs to return to the spool base for next reeling upon completion. Stalks fabrication onshore means that the critical activities like sensitive welding process for Corrosion Resistant Alloy (CRA) lined or Steel Catenary Riser (SCR) pipes with stringent misalignment criteria can be done in controlled environment. With recent development, portable reels can be used , strings spooled on shore and then transported on cargo barge to site for loading onto the reel lay vessel (with the requirement of heavy lift crane). The pipeline goes through process of plastic deformation during reeling and straightening during unreeling. Thus this limits the pipe diameter (currently 16 inch) and wall thickness that can be installed with this method.
- Tow method: some projects may utilize this method depending on project economics, design and field layout. Riser tower or integrated pipe bundles can be fabricated, tested onshore, towed and then submerged in controlled manner on site.
For subsea field the pipelines are normally terminated with Pipeline End Terminations (PLET) either on one or both sides. These PLETs are then connected via jumpers/ spools to manifolds and subsea trees as part of the subsea architecture.
Each installation method offers own advantages / disadvantages. Detailed study has to be carried out on a project to project basis from initial concept to installation phase.