OTC 20506Deepwater Pipeline and Riser Installation by the Reel-Lay Method S N Smith and A J Clough, Subsea 7 Copyright 2010, Offshore Technology Conference This paper was prepared for presentation at the 2010 Offshore Technology Conference held in Houston, Texas, USA, 3–6 May 2010. This paper was selected for presentation by an OTC program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material does not necessarily reflect any position of the Offshore Technology Conference, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Offshore Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of OTC copyright. Abstract The reel-lay method is generally the most effective way of installing infield subsea flowlines and risers particularly for sizes up to around 16 inch. This paper describes one of the most advanced reeled pipeline installation vessels in the world, the Seven Oceans, and the variety of pipelines and risers that she has installed including the welding and inspection of high fatigue life SCRs and sour-service flowlines. The paper goes on to present various recent developments for reeled installation including HFI pipe, PE lined pipe, mechanically lined pipe, clad flowlines and SCRs, high strength pipe, hybrid risers and electrically heated-traced flowlines. These show the continuing attraction of reel-lay for ever more technically demanding work and that for options such as electrically heat-traced flowlines that reeling will be the main vessel based installation method. 1. Introduction 1.1 Vessels The reeled pipelay concept has been in use since the Pipelines Under the Ocean (PLUTO) project across the English Channel (Purvis, 1946). The reel ship Apache (Anon, 1979) is a notable name in the development of the technology and was first operated in 1979. Other reel lay vessels followed including the Skandi Navica (Clarkson, 2006) now named as Seven Navica. Another notable vessel was the Deep Blue (De Soras & Cruickshank, 2000) and more recently the Seven Oceans. Other reeled vessels also exist but the characteristics of these main ones are given in Table 1. Vessel Name Vessel Type Length Breadth Depth Draught Reel Hub Diameter Reel Capacity Installed Power DP Power Accommodation Top Tension Crane ROVs Apache Rigid Reel Lay 122.91m 23.34m 8.69m 5.55m 16.44m 2,000te 15.09MW 10.74MW 95 156te [197te including back tension to reel] 27te - Table 1:- Reel Lay Vessel Main Characteristics Seven Navica Rigid Reel Lay 108.53m 22.00m 9.00m 7.17m 15.00m 2,200te 12.60MW 9.80MW 72 Deep Blue Rigid Reel Lay 206.50m 32.00m 17.80m 10.00m 19.50m 2 x 2,700te 33.60MW 25.60MW 160 Seven Oceans Rigid Reel Lay 157.30m 28.40m 12.50m 7.50m 18.00m 3,500te 18.90MW 15.85MW 120 205te 550te 400te 60te Option 400te 2 x 3,000m 400te 2 x 3,000m The pipe lay rate is controlled during the lay operation by a single linear tensioner with a 400te dynamic capacity (500te holding capacity). and fracture toughness testing simulating the end of life case in the engineering critical assessment.2 Spooling & Welding One of the main attractions of reel-lay is that all the welding and inspection can be done onshore in well controlled conditions at the spool base off the vessel critical path. or statistical sorting with an ID/OD machining operation.75 mm for flowlines. when clients specify tight and onerous fabrication or fatigue requirements. The steel mills can reliably supply this up to around 10inch diameter but above this. can be pre-fabricated ready for spooling prior to the vessel arrival. the actual delivered tolerance tends to creep out to around 1. For SCRs even tighter tolerances are beneficial and help deliver the required fatigue life. 2. The pipe hang off clamp is installed below the ramp at the stern of the vessel and has a holding capacity of 600te.25 mm can be obtained with upset forged ends such as the so-called PURE ends (Premium Upset Riser Ends). Additional strain age testing is commonly carried out replicating the strain levels imposed during reeling and installation. 1. Welding operations are generally automatic in order to replicate high mechanical integrity in each pipeline girth weld. She was contracted in May 2005 and delivered complete in July 2007. For a typical flowline ± 1. Fig. With HFI pipe the mills can supply to a tighter tolerance over a larger range of sizes. Spool bases are typically laid out so that long stalks.3 Pipe Specifications To optimise the production process the installation contractor typically requires tight end tolerances for the pipes to supplement the clients specifications to reduce mis-match and reduce the time and space required for end-sorting and alignment operations prior to welding.4 mm and for thicker deeper water pipe there does tend to be increased mill rejections on the larger sizes.500te of rigid pipe and laying in water depths down to 3.2 OTC 20506 1. Some seamless mills are also currently promising ± 0. This can be carried out by full scale simulated reeling trials. typically about 1 km long. Tolerances of ± 0. 1 Simulated Reeling Trial 1.000m. The vessel is capable of carrying up to 3. see Fig. as used on the MARS project (by others). . or a replication of the cyclic strain on small test strips. Transcheit. core diameter of 18m and a usable width of 10m. The pipe is stored on a midships mounted reel recessed into the vessel with a flange diameter of 28m. Seven Oceans The Seven Oceans with her constituent equipment is illustrated in Fig. lead to lower installed costs. 2009.0 mm on the ID is specified. The spooling itself is a rather unique operation in which the stalks are loaded on to the ship by bending them plastically around the reel. 2009) but it does of course mean that the extra loading has to be considered during the critical engineering assessment and establishment of weld acceptance criteria. For welding the generally adopted approach is to ensure that the pipeline girth weld overmatches the strength of the parent pipe material. weld consumables typically require yield strengths in the order of pipe material SMYS + 15ksi. In order to ensure this. Although some of these operations lead to higher mill procurement costs they can. The analysis and technology for this are well known and is constantly being refined (Denniel. This additional testing is generally applied to weld procedure qualification. 2. The stern mounted pipelay ramp can be inclined forward to suit the departure angle of the pipe catenary for the water depth and fleets across the vessel to match the transverse position of the pipe departing the reel. with seamless pipe. The smaller wire enables the numerous smaller jobs to be more readily handled on deck and subsea. In DP operations. Further details can be found in Smith & MacGregor. MacGregor et al 2009. The aft deck of the vessel between the reel and the ramp has an area of 650m² and has a strength rating of 10te/m². The storage winch is capable of storing 3.000m of 119mm wire. Smith et al 2009. above the level of the bridge. two drop-down azimuth thrusters and a tunnel thruster. a PLET manipulator and a PLET line-up tool. three in each of the two engine rooms. The secondary A&R system has an 80te rating. Each ROV has an independent LARS and umbilical allowing operations in 3. 2 Seven Oceans General Arrangement The main offshore mast crane is installed on the port side of the vessel just aft of amidships and has a main hook with capacity of 400te at 16. The deck thickness has been increased to 25mm to allow for wastage associated with repeated seafastening of items and subsequent removal and there are no fuel tanks immediately below the main deck so that hot work is facilitated. In transit. Two work class ROVs are installated in a hangar situated at the aft end of the superstructure. The Seven Oceans has a diesel electric propulsion system with power supplied by six diesel electric generator sets. For planned (or unplanned) laydown of the pipe. A helideck suitable for Sikorsky S-61 or Super Puma is situated forward. An auxiliary crane with a capacity of 40te at 14m radius is installed amidships on the starboard side of the vessel and two 12te cranes are installed aft to facilitate pipelay operations. The system has DP Class II notation but the as-fitted specification is well in excess of the requirements making the vessel well suited for work adjacent to platforms such as SCR hand-over operations. station keeping is assured by the three stern azimuth thrusters and at the bow.OTC 20506 3 PLETs are handled using a dedicated PLET handling system. a 450te A&R system is installed. . propulsion is provided by three stern azimuth thrusters.5m radius and a 50te whip line. Each generator can run on either MGO or IFO to reduce costs.000m water depth. This system consists of a deck mounted rail system. Fig. 2006. High mechanical integrity. Tables 2 and 3 show the mechanical properties achieved on SCR projects with this process.59 1.6mm Fig.67 1. 3. Pipeline & Risers Installed by Seven Oceans 3. The welding method adopted was pulsed hot wire automated GTAW.100 metres was the first project for Seven Oceans and its lines were installed in Autumn 2007 around 30 months from the announcement of the build programme. The welding of these SCRs presented significant challenges due to the stringent acceptance criteria.625” (193.6km). Location Weld Metal Weld Metal Weld Metal HAZ HAZ HAZ Test Temperature -5°C -5°C -5°C -5°C -5°C -5°C As Welded CTOD (mm) 1. All test values given are averages of three.1 Blind Faith The Blind Faith development in the Eastern Gulf of Mexico in water depths between 1. This was selected for two main reasons:High weld quality.625” (193.7mm) x 20.69 1.4mm 7.62 Table 2 CTOD Values Note: Specification Requirements: 0.980 and 2. .83 1. The main scope of work was the engineering.50 Post Reeled CTOD (mm) 1.63 1. 3 Seven Oceans on Blind Faith Further details of the general installation work are given by Hensley 2008 and are illustrated in Fig.7mm) x 25. The SCRs were as follows: 2 x SCRs in API 5L X60 7.70 1.51mm minimum average Location Test Temperature As Welded Charpy Impact (J) Post Reeled Charpy Impact (J) Weld Metal HAZ -18°C -18°C 425 408 434 431 Parent Material -18°C 412 436 Table 3 Charpy Impact Values Note: Specification Requirements: As welded 41 J minimum average.51 1.55 1.4 OTC 20506 3. Post reeling 53J minimum average Both of these sets of results show clearly that the reeling process has no detrimental effect on these mechanical properties.77 1. procurement and installation of 14km of rigid flowlines (14km) and two Steel Catenary Risers (2.72 1. 2 Tombua Landana Tombua Landana situated in Block 14. .9mm diameter with wall thickness from 17. . 22. offshore Brazil.4mm.2 x 10” production flowlines.1 steel tube umbilical and flying leads. 3.9mm diameter. Resistance to sulphide stress corrosion cracking was established by first cyclic strain ageing (at strain levels duplicating the installation of the worst case scenario) then testing in accordance with NACE TM 0177 with solution B and four point bends in accordance with EFC-16.t. .1 mm diameter.10 x flexible jumper.600 and 2. . These tests were carried out at 85% of the specified minimum yield strength of the base material. On the second the pipes were X60 all 323. 4 Welding at the spoolbase in Luanda. installation of 4 manifolds and 25 rigid jumpers.OTC 20506 5 3.1 x 12” water injection line.1 x 6” gas lift line. . Installation in progress is shown in Fig.1 x 8” test flowlines.2mm w.5mm to 25. All the reeled flowlines were installed by the Seven Oceans after fabrication at the Luanda spoolbase (see Fig. Welds had to comply with NACE MR 0175 / ISO 15156. The scope was split between 2008 and 2009. The scope included the following:.000 metres including the world’s first lazy wave SCRs (Hoffman et al 2010). Angola with comparatively shallow water depths between 270 and 370 metres is another example of a project with extensive reeled flowline installation. On the first the API 5L X65 pipes ranged from 273.t. to 323.6mm w. .4 BC10 BC-10 is located in the Campos Basin. The scope of work was the engineering fabrication and installation of - 11 pipelines totalling approximately 130km 7 steel catenary lazy wave risers totalling approximately 21km. in water depths between 1. . Fig. 28. 4) where the production welding was 100% done by Angolan welders. This demonstrates that welds can meet the requirements for sour-service after reeling. 3 dynamic and 2 static umbilicals totalling approximately 55km. 5.1 x 6 slot production manifold.10 x pipeline end terminations. 3.1 x 6 slot water injection manifold. .3 Sour Service Flowlines In Brazil two projects have been reel layed in which the flowline welds had to be qualified for sour service. offshore Cabinda. . 6” x 15.9mm -1 off API 5L X65. see Fig. 5 Seven Seas and Seven Oceans working together on project BC-10. 2003. weld profiles. pulsed hot wire automated GTAW was used again with pulsing Fig. The approach of one operator is described in Kopp et al. The allowable weld defect size was on the limits of detectibility with current AUT systems. 6 were as follows. 12” x 19. Fig. allowable defect size. 8. 8 Weld Schematic focused at the bevel to ensure full fusion at each side wall. -6 off API 5L X60. and correct interpretation of inspection results.6 OTC 20506 Fig. Of particular relevance here all 130km of flowlines were reeled as were the 7 lazy wave SCRs.1mm Fig. 7 Installing VIV Strakes Welding Torch Oscillation Pulse Weld For BC10. 6 Lazy Wave SCR Schematic Obtaining the required fatigue life for SCR welds is a considerable challenge and requires attention to all aspects of production and inspection including miss-match of pipe ends. . The main particular of the SCRs as shown in Fig. Production welding rates increased significantly and spurious cut-outs reduced during the project due to close liaison with the client and the use of on site macro sectioning and evaluation to help calibrate the AUT results. in various circumstances. bespoke sizes. 2009) thus confirming the attraction of HFI pipes for reeled installation. The tensioner pads can be made from different materials. New Technology for Reeled Installation 4. The majority of the pipes installed have been seamless carbon steel such as API X52. X60 or X65. Before describing these we should first mention some important internal technology. 9. µ 12" PP Coated Pipeline during Initiation 402mm OD PP 365mm OD PP Frictional Safety Factor = 1. offer benefits over seamless pipe in terms of reduced lead times. 4. tighter dimensional control. 10. HFI pipe had previously been installed by reeling however due to a lack of historical mechanical integrity data a test programme was undertaken comprising trials and subsequent material testing on nine pipes with three pipe grades (X52. However other options to offer more cost effective solutions or to cater for more aggressive fluids and other operating requirements are being developed.42 Tensioner Track Loading.2 Tensioner Pads For a reel lay ship the top tension is generally provided by one or more tensioners and the tensioner pads squeezing against the pipe are the actual interface. Project specific testing is not generally necessary but there is a considerable bank of test data and FE model results on physical behavior of different pad designs. have different geometries and have different support shoes and the frictional coefficient can vary with contact pressure as well as with type and quality of the pipe coating. good mechanical properties and chemistry resulting in excellent weldability. Fig. kn/m per track Fig. and resulting frictional performance as shown in Fig. reduced costs. All tests were satisfactory (McCann & Rodger.OTC 20506 7 4. 10 Friction Curves 4. Fig. . After full scale simulated reeling trials a number of mechanical tests were carried out including charpy impact tests and CTOD tests.3 HFI Welded Pipes HFI (High Frequency Induction) welded pipes can. X60 and X65).1 General Reeled installation of pipelines has been in use for a considerable number of years. 9 FE Model of Tensioner Pad Friction Coefficient. 4 PE Lined Pipe Polymer lined pipe has been reel laid on a number of projects. utilizing sealing plugs as used previously on certain riser installation activities. After reeling simulation extensive testing showed no degradation of the material properties even after wrinkling of the liner. 2010. (Campbell. For such fields it is possible to use CRA (Corrosion Resistant Alloy) materials such as 13% Chrome. 10. Super Duplex. 11 Perfect pipe after reeling with low internal pressure Fig. One of the largest such lines was a 16” water injection line which had a swagelined PE100 liner and Weldlink connectors. metallurgically clad pipes. A detailed operational procedure has been developed to reliably maintain the internal pressure during the spooling on and offshore pipelay operations. see Fig. see Fig. A number of such lines have been installed by S lay and approximately 100kms included in nine pipeline bundles (a recent bundle project is described by Leggett & Simons. Two tests have been conducted to date with both samples reaching 20 million cycles.9mm wall thickness. In order to extend the use of these pipes a programme of reeling trials and mechanical testing has been undertaken to address the main concerns of the maintenance of material properties during reeling and potential wrinkling of the liner. Mechanically lined pipes are attractive because the line pipe costs are significantly lower than metallurgically clad pipes. In further work it was established that reeling under a low internal pressure of around 25 bar prevented the formation of any wrinkles thus maintaining perfect pipe characteristics. 4. or mechanically lined pipes such as BuBi pipe. Further details are given in Mair et al. 11. 12 Fatigue Tests In an extension to this work to allow BuBi pipe to be used for reel-layed risers some preliminary fatigue testing has been conducted on samples of the pipe after reeling. see Fig.5 Mechanically Lined Pipe An increasing number of fields have fluid properties which would severly limit the life of carbon steel linepipe material. Carbon Steel Outer Pipe Weld Cladding Typically Inconel 625 50mm Nominal 3mm liner Fig. 18. X65 Pipe with a 3mm Alloy 825 liner with approximately 50mm long weld overlay at the end.8 OTC 20506 4. 2009). 2009). 10 Schematic of BuBi pipe Fig. Duplex. These tests will be run to destruction and further full scale fatigue testing will be carried out in 2010. . The test pipe was 273mm OD. 12. In addition an FE model was produced which accurately predicts the overall performance. t. 2006. The clad pipe being used is X65.uration was used with an internal gas purge which produced a very even and controlled weld root profile. There has been considerable work done on improving the fatigue life (eg Atkins et al. This. Considerable work has been done on this. The weld procedure is a development of that used on BC10. This weld solution has been tested fully in accordance with DNV OS-F101 with strain age charpy impacts down to -40°C. Darcis et al. for example Kristoffersen et al. Fig. A narrow closed gap weld conFig. 2009 and Kan et al. One such project includes 35km of 12” and 10” diameter clad production flowlines and 7km of 10” diameter carbon steel gas injection flowlines. Two parallel projects are therefore being undertaken to develop suitable weld procedures and then conduct full-scale fatigue testing. 16: Root Profile . 14: Welding in Progress should be J Layed. however. see Fig. One refinement of SCRs is to use weight optimized design (Karunakaran. Pulsed hot wire automated GTAW was used with an Inconel 625 weld consumable. Fig.6 Reeled Clad Flowlines and DEH Clad flowlines are currently being installed by the Reel lay method.4. Lillig et al. It is increasingly becoming required to use Clad pipe for SCRs particularly in the highly fatigue sensitive areas around the touch-down point and at the critical top sections because H2S is reported to degrade the fatigue properties of C-Mn steel by a factor of 10-20 in life while clad pipes are reported to have a performance close to or as good as in air. most importantly for reeled installation. 318mm OD. that no effect from previous reeling of the hammer-peened specimens was observed. 2009). 25mm w. 15: Weld Section Full scale fatigue testing will be conducted in 2010. 2008 concludes that hammer peening of the OD gave a significant fatigue improvement and also. 13.7 Clad SCRs A number of SCRs have been installed by reeling as described in Sections 3. with Alloy 825 Cladding. The objective is to qualify a reeled Clad SCR. 14. 2005.OTC 20506 9 4. is not universally accepted and some Operators are currently requiring that clad sections in an SCR Fig. Fig. 13 DEH Cable Installation by Skandi Navica 4. Fig. 15 and 16. 2005) and another is to use lazy wave SCRs as on BC10 as described in Section 3. In addition a Direct Electrical Heating (DEH) cable will be attached to one of the flowlines (which is part of the above). Fig. In the first phase a PIP design has been developed with ITP using Izoflex insulation system. Fig. 17 Seven Seas J Lay Module 4. 2009) and a suite of J-Lay equipment installed on Seven Seas.8 J-Lay Separate work has also been done on J-Lay welding. 4. A logical evolution of the current technology is to enhance the thermal performance as far as practicable.56W/m²K Cool Down 30 hours to 35ºC 95 hours to 35ºC Table 5 As an example of the latter.3W/m²K 0. From the reeling point of view the main issue is ensuring that the pipeline girth weld overmatches the strength of the parent pipe material. This is being done in a number of phases. Karunakaran et al 2009. b) enhancing thermal performance for the benefit of the client. 4. see Fig.6W/m²K OD 318 mm 367 mm 496 mm Insulation Izoflex Aerogels P U Foam Table 4 Insulation Aerogel Izoflex U 1. which can potentially be used for those applications for which reeling is not accepted but is outwith the scope of this paper. 17. The lower wall thickness can reduce top tension for the installation contactor. reducing top tensions and allowing longer lengths on a vessel reel. given specified pipe diameters.10 Hybrid Risers Hybrid risers such as SLORS and Grouped SLORS. Table 4 gives an example of the former based on an inner pipe OD of 236mm and U=0. The riser pipes themselves can be readily reeled and vessels such as Seven Oceans. (Chong et al. in which the crane capacity matches the top tension capacity.11 Pipe in Pipe. reduce the size of buoys on SLORS and CORS type risers and reduce the loads on the production vessel. 18 Grouped SLOR a) to reduce the outer pipe diameter for a specified thermal performance thus reducing material costs. are ideal vessels to install such systems. see Fig.10 OTC 20506 4. Fig. At present we have qualified weld procedures with girth weld metal yield strengths of 109ksi (750MPa) with consumables having Nickel contents less than 1% and hardness limits within that required for sour service. for a nominal 6” x 10” PIP Table 5 clearly shows the very impressive performance of the Izoflex system. Enhanced Thermal Performance It is well known and reasonably straightforward to install standard PIP flowline by the reel-lay method. 18.9 High Strength Steel With increasing water depths and increasing occurrence of HP/HT developments there is an increasing potential benefit in using higher strength steels particularly for risers. are an attractive field development option. This can be used in two different methods. 19 . It is also suitable for long step-out distances. see Fig. The ETHF is also useful for producing waxy oils. Conclusions The reel lay method is a well established way of installing in-field flowlines and risers. 20 EHTF Tests. of the project lifetime. 4. Electrical heating systems have been used elsewhere and several projects have been installed with DEH (Direct Electrical Heating) cables. Fig. 19. centralisers are not required giving a significant further improvement in thermal performance. Contractors and Suppliers. Acknowledgements The authors would like to thank Subsea 7 for permission to publish this paper. Full scale construction trials have also been performed at a spool base to demonstrate that it is entirely practicable to build stalks with no centralisers. 20. Electrically Heat Traced Flowlines As a next step in improving thermal performance a number of trials have been done with electrical trace heating (EHTF).OTC 20506 11 Full scale testing has been done both before and after reeling on a 6” x 10” design using a specially constructed thermal test rig at Herriot Watt University. Bench tests/bending trials were conducted which confirmed FE model results and demonstrated that the mechanical integrity of the wires was unaffected by the reeling process. Bending trials also showed that with the Izoflex material. None of it would have been possible without the help of colleagues at Subsea 7 in preparing the paper and also a whole range of onshore and offshore personnel who executed the projects as well as Clients. with high wax appearance temperatures. However the EHTF technology combined with Izoflex performance only requires approximately one tenth of the power of a DEH system which is a considerable advantage. The thermal performance was only reduced by 5-10% due to reeling which can clearly be allowed for in the design process. because of its strength in compression. . or a significant part.10 Pipe in Pipe. It should be noted that because of the continuous wires in the PIP annulus this technology can only realistically be laid by the reel-lay method or in towed bundles. This paper demonstrates that the technology can be extended to provide further cost effective solutions and solutions for ever more challenging fields. 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