Reeled pipelay has normally been used in fully developed and matured offshore oil and gas field areas with close proximity to onshore support, onshore logistics, and with short offshore transit distance to onshore spoolbases for loading the pipeline stalks onto the reel. This activity normally requires comprehensive planning both onshore and offshore, and is often on the pipelay’critical path.
New discoveries in remote locations, such as the Brazilian pre-salt and post-salt developments, often have long transit times from established spoolbases and port facilities, rendering certain reeled lay scenarios uneconomical. To reach the postsalt and pre-salt reservoirs in Brazil and West Africa and the Miocene and Lower Tertiary subsalt in the Gulf of Mexico, it is necessary for operators to drill wells in deep and ultra-deep water in increasingly remote regions.
This presents a challenge for operators as subsea construction services are not always readily available in remote locations and thus have to be mobilized from established regions. This also creates a logistical challenge, as most of these areas do not have spoolbase and shorebase support facilities within a reasonable transit distance.
Specifications
The Lewek Constellation is an innovative, state-of-the-art, DPI 3, iceclass pipelay vessel that not only has the ability to install multiple risers, flowlines, flexibles, umbilicals, and platforms in a field, but also can do so in remote locations. The vessel has a multi-lay system and heavylift capabilities. By using a portable reel system, the vessel is able to stay in the field or in close vicinity, thus taking reeling operations off the critical path and maximizing the vessel’s operational time.
The vessel’s multi-lay system (MLS) is comprised of an 800Te tiltable tower, a 60Te pipeline end termination (PLET) handling system for large PLETs, and a 1200Te A&R system. The tower has dual 400Te tensioners, a straighter for handling pipe-in-pipe flowline systems with outer pipe up to 16in. outer diameter (OD), a 900Te hang-off module (HOM), and a movable/adjustable work platform along the tower. The tower can be adjusted from 60° to 90° to accommodate pipe laying from shallow water to ultra-deepwater. The A&R system has two 600Te traction winches and a 125Te secondary winch.
In rigid reel lay, the vessel can apply up to 800Te of dynamic top tension on flowlines and rigid risers up to 16in. nominal OD. In flexible mode, the vessel and lay system can accommodate sizes up to 24in. nominal OD, while applying 400Te and 430Te of top tension, respectively.
Spooling barge
The pipelay vessel will use a spooling barge with a ballasting system to manage the heel and trim of the reels. The barge will be outfitted with a spooling system that includes a fleeting roller track assembly, a fleeting tensioner, a reel cradle assembly and winches. The barge will be moored at the quayside where the pipe stalk will be pulled over the stern using the winch, through the fleeting tensioner and across the rolling support assemblies, as pipe is spooled onto the reels. Once spooling is completed for a reel, the spooling spread will be fleeted into position for spooling of the next reel. Upon completion of all spooling operations, the reel barge will be towed to the Lewek Constellation to complete the offshore reel transfer.
The reels will be brought offshore to the pipelay vessel at a favorable location. The vessel will then use its heavy-lift system to offload empty reels and load full reels. This reduces the project time by taking reeling off the critical path and by removing the transit time back to the spoolbase to pick up additional product.
Heavy-lift system
The 3,000Te crane at the stern of the vessel can be used for heavy lifts of large manifolds, platforms, and topsides. To transfer the reels from the barge, the vessel will use the 3,000Te crane. The reels will have a weight of about 850Te empty and about 2100Te fully loaded.
Once a reel is transferred onto the pipelay vessel, the reels are moved into position using the reel skidding systems (RSS). The RSS moves the reels both transverse and longitudinally along an “H” shaped track on the main deck. This allows loaded reels to be moved into position for reeling operations and empty reels to be moved to a storage position for offloading.
The reel drive system (RDS) is situated forward of the main crane and is used to drive the reels during pipelay. The RDS will also maintain the back-tension during pipelay.
Hang-off module
The hang-off module (HOM) provides up to 900Te of tension on the pipe during pipeline tie-in, termination, and abandonment operations. The HOM is located inside of the moonpool and has forward and aft fleeting capabilities that allow for stowage during transit. A workstation can be moved into place when the pipe is in the HOM. The work station is used for welding and coating activities; it can be moved out of the firing line during pipe transfers or installation of large structures.
PLET handling system
The PLET handling system (PHS) is used to move either first- or secondend PLETs up to 60Te into position and alignment for welding operations. The PLET will be upended using the 80Te deck crane and placed onto the PHS. Grippers 
are then engaged to prevent the PLET from rotating while on the PHS. The PLET handling system is then skidded into position on the firing line. Once the PLET is in position, hydraulic arms rotate the PLET to match the inclination angle of the lay tower.
The vessel has two 1250Te carousels in its hold. When in flexible mode, product is guided over chutes through the tensioner. The carousels can handle flexible pipe and umbilical ranging from 4-24in. OD.
In addition to the heavy-lift crane, the vessel has an 80Te telescopic crane and an auxiliary hoist capable of handling 10Te at any reach. The 80Te crane is used for auxiliary deck operations, PLET handling and mobilization/demobilization of the vessel.
The vertical reels used on the vessel are a standard design with a capacity of 1200Te per reel. Standard reels ease the handling and moving of reels to and from the vessel. Optimizing reel packing is important for the efficiency of a given pipelay campaign.
The vessel has a high top tension capability to lay pipe in deep and ultra-deep water. The maximum installation depths for pipe ranging in outer diameter from 8-16in. with varying wall thicknesses are shown in Figure 6. The sizes of pipe are bound by the minimum reelable wall thickness, the minimum wall thickness to resist collapse, according to DNV-OS-F101, and the maximum static top tension of 640 Te.
Pipelay comparison
Traditional reel lay piplay vessels have spooling operations occurring on the critical path, because they have to transit to a spoolbase to reel pipe. By using portable reels, it is possible to take spooling operations off critical path. A typical schedule has been developed to compare the duration of a deepwater pipelay project performed by a traditional reel lay vessel and a project completed by the new vessel, Figure 7.
Having a continuous pipelay campaign allows pipelay to be done more quickly. This can be ideal for remote locations close to the Arctic, by minimizing weather downtime. Project duration is shortened by about 12 days compared with the traditional reel lay pipe vessel schedule.
Project execution
With the heavy-lift crane and multilay system, the Lewek Constellation is a “one stop shop.” For a typical offshore development, the vessel is capable of lifting and installing topsides, as well as the entire subsea field. The vessel can install a rigid or flexible riser, weld the flowline to the riser, lay the flowline, and terminate the line with a PLET. The vessel also has the deck space to perform post metrology welding and field joint coatings of pre-fabricated of rigid jumpers. The jumpers can then be installed directly from the deck of the vessel using the vessel crane. The multi-lay system gives the vessel the ability to install umbilicals and flexible flowlines. Two work-class ROVs can assist with pre-commissioning activities.
The vessel’s ability to reconfigure from pipelay, to flexible and umbilical lay, allows for the installation of field developments with multiple flowline and umbilical products. Furthermore, the vessel can reconfigure to heavy-lift mode to install large manifolds, subsea pump stations and fixed platforms.
By using the vessel to install an entire field development, the need for additional vessels is minimized, thereby reducing the chance of a schedule slip and increased cost from multiple mobilizations and transits to remote locations. OE
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