2 Deepwater Installation Tasks
2.1 Introduction
Floating Production Systems (FPS) is widely considered as the most practical and commercially attractive solution for the development of Deepwater (500m-1500m) and ultra Deepwater (1500m-3000m) oil and gas reserves.
Depending on the hydrocarbon reservoir characteristics, the X-mas trees can be either in surface (“dry” completion) or subsea completed.
In general FPS such as TLP, SPAR and Deep Draft Semi-submersible will serve the 'dry tree' configuration. The ‘wet tree’ configuration would rather used FPSO and semi-submersible platform to remotely control the subsea production & injection system.
2.2 Installation Tasks
The most comprehensive and field proven Deepwater architecture is the use of surface-controlled subsea trees, tied-back to a moored FPS (FPSO, semi-submersible) by means of flowlines, risers and control umbilical.
Such Deepwater development scenarios will typically require the following main installation tasks:
Transportation and installation of mooring lines, e.g. combination of chains, steel wires and/or synthetic ropes, anchors or piles.
Topside lifting of process modules onto the FPS.
Towing and mooring of FPS and oil export offloading buoy including installation of OOL (as the case may be)
Lifting and installation of subsea foundations, templates, manifolds and production systems (Production Well Jumper, Injection Well Jumper, XT, Spool).
Laying of flowlines and risers
Laying of control umbilical
Tie-ins of subsea structures by means of jumper, spools and flying leads, e.g. trees to manifold, to flowlines
UFR pre-commissioning
SPS commissioning, etc
Decommissioning of surface and subsea structures.
2.3 Lifting Requirement
Topside process modules are generally designed to be within the existing heavy lift crane vessel capabilities, which can range from 3000tons up to 14000tons capacity (e.g. SSCV Saipem 7000, Heerema Thialf, Heerema Balder, Cnooc Lanjing, Subsea 7 Borealis…). The existing heavy lift vessels (see Annex 01) are well adapted and in sufficient number to address these needs.
Float-over are commonly used for fixed structure.
For the installation of subsea structures and because of the water depth, the general practice is to lift the subsea structures (of some 500 tons) on surface with the vessel crane and to cross-haul it (under water) to a deck winch (with sufficient cable length) which will then lower the subsea structures to the deep seafloor.
2.4 Laying Requirement
The development of new Deepwater oilfields uses generally small to medium diameter pipelines, e.g. 6”-14” nominal outside diameters.
Export pipelines (mainly gas trunkline) with larger diameters of 20" to 30" and heavy wall to prevent hydrostatic collapse, will impose large laying tension (above 500tons) which only few lay vessels have the capabilities with (see section Section 7.2, “Pipe Lay Vessels”).
The following corresponds to the current track records in Deepwater pipe-lay operations:
12”OD Canyon Express pipeline laid by Saipem ‘FDS’ in 2230m of water depth.
10”OD Enterprise MC920 (GoM) pipeline laid by Allseas ‘Solitaire’ in 2275m of water.
28”OD Mardi Gras (GoM) pipeline laid by Heerema ‘Balder’ in 2100m of water depth
24”OD Blustream (Black Sea) pipeline laid by Saipem ‘7000’ in 2150m of water depth
32”OD TurkStream (Black Sea) pipeline laid by Allseas ‘Audacia’ in 2200m of water depth
24”OD Appotamox (GoM) pipeline laid by Allseas ‘Audacia’ in 2195m of water depth
18”OD Sapinhoa Norte (Brazil) pipeline laid by Saipem ‘FDS2’ in 2200m of water depth
18” OD Kaombo (Angola) pipe in pipe laid by Balder in 1950m of Water depth
