Method for installing a sleeve around a portion of an underwater pipe for transporting fluids

Abstract

The invention relates to a method for installing at least one sleeve (8) around a portion of an underwater pipe (6) for transporting fluids, wherein the sleeve is formed by two half-shells, and wherein the method comprises maintaining the pipe in a substantially vertical position, arranging the two half-shells of the sleeve in a deployment system (2), positioning the deployment system at a free upper end of the pipe (6) by centring it on an axis (X-X) of the pipe, lowering the deployment system along the pipe to the desired position of the sleeve, fully closing and locking the two half-shells of the sleeve onto the pipe, and raising the deployment system back towards the free end of the pipe.

Description

Description Title of the invention: Method for installing a sleeve around a section of underwater fluid transport pipe Technical Field

[0001] The present invention relates to the general field of underwater fluid transport pipes providing the bottom-surface connection for the transfer of hydrocarbons, for example oil and gas, from underwater production wells. This type of bottom-surface connection can also be used to transfer other fluids between the surface and the seabed, such as for example treated water or carbon dioxide.

[0002] More specifically, it relates to a method of installing sleeves (such as buoyancy modules or vortex suppression modules) around a section of a subsea bottom-surface connecting pipe, as well as a system for implementing such a method. Prior art

[0003] In the field of offshore oil and gas production, subsea pipes called "risers" are pipes that are usually rigid or solid, but sometimes also flexible, providing the connection between a floating support, such as a floating production, storage and offloading unit (or FPSO for "Floating Production, Storage and Offloading"), and the seabed, particularly at great depths.

[0004] Among this type of risers, the steel catenary riser (or SCR) is known, which is a common method of connecting a subsea pipeline to a deepwater floating oil production platform. SCRs are used to transfer fluids such as oil, gas, injection water, etc. between platforms and subsea pipelines.

[0005] We also know the “Steel Lazy Wave Riser” (or SLWR) which is a steel pipe designed to allow decoupling, significantly greater than for an SCR-type riser, between the movements of the production unit on the surface and the movements of the line on the seabed. The so-called "lazy wave" configuration refers to the specific shape given to this type of subsea pipeline. In fact, this pipeline is deliberately arranged in such a way as to form one or more undulations (wave shapes) in the vertical plane, these undulations allowing increased decoupling.

[0006] These undulations are typically obtained by placing a plurality of buoyancy modules (buoy type) around a portion of the pipe that is desired to be floating, either by being spaced apart from each other (according to a distributed distribution of buoyancy), or by being joined to each other (according to a continuous distribution of buoyancy).

[0007] An SLWR pipeline has several advantages over an SCR pipeline. It reduces the mechanical stresses placed on the pipeline, which increases its lifespan and reduces the risk of failure. It allows for greater vertical or lateral offsets of the floating unit to which it is connected at the surface. In addition, it offers better protection against severe weather events such as storms, by allowing the pipeline and float to move more freely. This additional freedom is particularly important at great depths where the impact of surface and pipeline movements is greater on the stress levels in the steel.

[0008] Alternatively, subsea bottom-to-surface connecting pipelines can be constructed from single-length pipeline elements that are assembled on board the laying vessel, then connected to the already constructed pipeline section and finally lowered into the sea as they are connected. This laying can be carried out using a J- or S-shaped laying tower positioned on the laying vessel.

[0009] With the so-called J-lay, the subsea pipeline is typically lowered from the laying vessel almost vertically. This type of laying requires a substantially vertical tower onto which the individual pipeline elements are brought one after the other using a loading arm from a horizontal position on the deck of the laying vessel to be assembled and welded to the already constructed pipeline section held from the laying tower. After welding and coating to improve corrosion protection or apply thermal insulation, the new pipeline unit thus connected to the already constructed pipeline section is lowered into the sea by moving the laying vessel forward by a lead roughly corresponding to the length of the pipeline unit.

[0010] The pipe is then lowered gradually into the water and placed on the bottom, gradually joining pieces of pipe together. The welding and coating operations are typically carried out in an assembly station located below the main part of the tower and above the section of pipe being laid. The individual pipe elements are therefore typically brought by the loading arm into a vertical position in the tower above the assembly station, transferred to said tower via the (pipe gripping) grippers of said arm and those of the tower, then translated vertically to be joined at the assembly station to the section of pipe already assembled and being laid in the water.

[0011] The two types of pipes, SCR and SLWR, have the common characteristic of presenting a linear continuity of the pipe, without break in slope and therefore, due to the rigidity of the steel pipes, profiles with fairly slow variations in slope.

[0012] These two types of pipes, SCR and SLWR, connect the seabed to a surface unit through the water column and are therefore subject to underwater currents. The flow of a fluid around a cylindrical pipe is likely to generate vortices that can cause the pipe to vibrate. If these vibrations resonate with the pipe's natural modes, they can cause significant mechanical fatigue in the pipe. To prevent the formation of these vortices or significantly reduce their impact, and thus avoid the associated design constraints, anti-vortex modules can be installed at strategic locations along the pipe or even along its entire length. These anti-vortex modules are typically formed from portions of cylindrical shells to the outside of which are attached fins arranged to form propellers along the pipeline. These anti-vortex modules can be used for both SCR and SLWR risers. In the case of the latter, they are generally installed on the portion of the pipeline located above the floating section (between this section and the surface production unit). The buoyancy modules can also integrate fins enabling the anti-vortex function on their external surface.

[0013] There are several methods of installing buoyancy modules (or vortex suppression modules) around a SLWR pipeline constructed using the J-lay.

[0014] For distributed distribution on an SLWR pipeline, buoyancy modules can be pre-installed on the deck of the pipelay vessel after the pipe unit has been assembled and before it is lifted to the lay tower by the loading arm. The pipe unit is then lifted to the lay tower with its buoyancy modules closed and locked against translation and rotation on a portion of the pipe unit. This same method can also be used to install vortex suppression modules.

[0015] Although a proven method, this approach generally requires maintaining void spaces (exclusion zones) on the pipe element to allow manipulation by the loading arm and its grippers, as well as by the gripping elements (grippers) in the tower. Therefore, it is not possible to achieve a continuous distribution with this installation method.

[0016] It is also known to use a V-trolley system. This system, located for example in the assembly station of the laying tower below the tower clamps, is used to load the buoyancy modules or the vortex suppression modules onto the pipe element once the unit length section has been connected to the pipe being laid and held by the tower.

[0017] Such a system thus theoretically allows for a continuous distribution of buoyancy modules around the pipe. However, it is limited to the modules small buoyancy and vortex suppression modules (because they must pass through the tower assembly station) and it is a manual (or semi-manual) system. In addition, this system also requires space available in said assembly station, to supply modules but also to move and approach the section of pipe to be equipped. However, assembly stations can sometimes be cluttered with equipment necessary for connecting the section of pipe of unit length to the section of pipe being laid. For example, we can note the presence of the elements necessary for welding the two sections of pipe, for checking this weld or even the thermal or anti-corrosion coating after this weld. In this case, the V-Trolley system cannot be installed in the assembly station.

[0018] To achieve a continuous distribution of the buoyancy modules with an efficient laying rhythm, the semi-automatic buoy loading system described in publication W02022 / 070160 A1 was proposed. This system allows the buoyancy modules to be loaded and installed on the pipe element after it has been welded into the laying tower and thus eliminates interference problems with the laying tower and the clamps of the loading arm and the tower. However, this solution requires having a significant space available for the positioning and operations of said loading system, space that may not always be available, depending on the architecture of the vessel deck, the tower and the assembly station. For example, for the SAIPEM FDS laying vessel, this equipment could not have been used as designed because the assembly station did not allow these operations. Statement of the invention

[0019] The invention therefore aims to propose a method for installing sleeves (buoyancy modules or vortex suppression modules) which makes it possible to obtain both a distributed distribution and a continuous distribution of said sleeves and which can be used on most laying vessels.

[0020] According to the invention, this object is achieved by means of a method for installing at least one sleeve around a section of underwater fluid transport pipe, in particular an underwater pipe providing a bottom-surface connection of the Steel Catenary Riser or Steel Lazy Wave Riser type, the sleeve being formed by two half-shells each having an internal face intended to be in contact with the pipe and an external face opposite the internal face, the method comprising: a) maintaining the pipe in a mainly vertical position; b) installing the two half-shells of the sleeve in a deployment system; c) positioning the deployment system at a free upper end of the pipe by centering it on an axis thereof; d) lowering the deployment system along the pipe to reach the desired position of the sleeve; e) completely closing and locking the two half-shells of the sleeve on the pipe;and f) raising the deployment system towards the free end of the pipe.;

[0021] The method according to the invention is remarkable in that it is compatible with all methods of laying subsea pipelines with a simple adaptation of the deployment system. This method is also compatible with other sequences of laying the subsea pipeline (for example, the subsea pipeline has been partly constructed then laid on the seabed before being recovered later with another vessel for the installation of buoyancy modules).

[0022] Furthermore, the method according to the invention makes it possible to install buoyancy modules or vortex suppression modules both in a distributed distribution and in a continuous distribution.

[0023] The installed sleeves can be buoyancy modules allowing the creation of a floating section on the pipe or modules for suppressing vortices from the current and associated vibrations.

[0024] In one embodiment, the deployment system is deployed from the laying vessel that constructed the subsea pipeline.

[0025] In this case, the subsea pipeline may be constructed using a J-lay method using a J-lay tower located at the stern or bow of the lay vessel, in the center of the lay vessel, or to one side thereof, and the deployment system is deployed from the J-lay tower.

[0026] Each sleeve may be installed from the J-lay tower as the subsea pipeline is constructed. In this case, the method may further comprise the prior installation on the deck of the laying vessel of at least one buoyancy or anti-vortex module around a portion of the pipeline to be assembled onto the subsea pipeline under construction.

[0027] Alternatively, each sleeve can be installed after the section of the subsea pipeline to be covered has been fully constructed.

[0028] In another embodiment, the deployment system is operated from a vessel other than the laying vessel constructing the subsea pipeline.

[0029] Each sleeve can be installed using a work platform located at the stern, bow, center or side of the deployment system deployment vessel.

[0030] In this case, the section of the subsea pipeline to be covered can be fully constructed before being transferred to the work platform to install each sleeve.

[0031] Alternatively, the section of the subsea pipeline to be covered may be constructed by assembling several sections of pipeline, said section of the pipeline to be covered being transferred to the work platform after assembly of each section of pipeline to install at least one sleeve therein.

[0032] In yet another embodiment, the vessel implementing the deployment system is the floating production unit on which the pipeline subsea is ultimately intended to be connected to form a bottom-to-surface connection for production.

[0033] In this embodiment, sleeves forming buoyancy modules can be installed from the floating production unit to form a SLWR type pipe with one or more corrugations. In this case, the deployment system can be able to move on the floating production unit between several risers connected thereto to successively install sleeves therein.

[0034] Still in this embodiment, the deployment system can also be used to retrofit sleeves forming anti-vortex modules onto an SCR or SLWR type pipeline to address vortex and vibration problems not anticipated in the initial design of the pipeline.

[0035] The invention also relates to a system for implementing the method as defined above, comprising: - an annular cage intended to be centered on the axis of the pipe and comprising means for receiving at least one sleeve; and - means for moving the cage along the pipe.

[0036] The means for moving the cage may include a winch connected to a cable fixed to the cage.

[0037] In this case, the cable may be an electrical umbilical cable connected to a power supply and control system to provide the power and control needed locally to move the cage.

[0038] Alternatively, the means for moving the cage may include a motorization system integral with the cage to assist in moving and positioning it along the pipe. The motorization then facilitates the movement of the cage along the pipe, this movement not being achieved solely by the cage's own weight. This motorization may rely on rollers in contact with the pipe or even tracks. Brief description of the drawings

[0039] [Fig. 1] Figure 1 is a longitudinal sectional view of a module deployment system according to the invention.

[0040] [Fig. 2] Figure 2 is a sectional view along 11-11 of Figure 1.

[0041] [Fig. 3] Figure 3 is a longitudinal sectional view of a two-stage module deployment system according to another embodiment of the invention.

[0042] [Fig. 4A] to [Fig. 4K] Figures 4A to 4K represent a sequence of installation of sleeves according to an embodiment of the invention.

[0043] [Fig. 5A] to [Fig. 5K] Figures 5A to 5K represent a sequence of installation of sleeves according to an embodiment of the invention.

[0044] [Fig. 6] Figure 6 shows an example of application of the method according to the invention to an FPSO. Description of the embodiments

[0045] The invention relates to a method for installing buoyancy modules or modules for suppressing vortices from the current and associated vibrations (also called anti-vortex modules) around a floating section of an underwater fluid transport pipeline, and in particular a pipeline of the SCR (for "Steel Catenary Riser") or SLWR (for "Steel Lazy Wave Riser") type.

[0046] Typically, a SLWR subsea bottom-to-surface pipeline is a steel pipeline that is constructed using a J-lay, S-lay, or roll-lay method and features one or more corrugations (wave shapes) to provide greater flexibility and better absorption of float movement due to currents or waves.

[0047] These undulations are generally obtained by placing a plurality of buoyancy modules (buoy type) around a floating portion of the pipe, either by being spaced from each other (according to a distribution distributed buoyancy), or by being joined to each other (according to a continuous distribution of buoyancy).

[0048] Each buoyancy module typically comes in the form of two half-shells, each having an internal face intended to be in contact with the pipe and an external face opposite the internal face.

[0049] A more conventional SCR type underwater bottom-surface connection pipe will not have any undulation and will therefore have a catenary with a more direct trajectory towards the seabed, without buoyancy modules.

[0050] SCR or SLWR type pipes can also be equipped with anti-vortex modules. These are also typically formed by two half-shells to be assembled around the pipe.

[0051] Figures 1 and 2 represent an example of a deployment system 2 of the buoyancy modules for implementing the method according to the invention (the same method applies to the deployment of anti-vortex modules).

[0052] This deployment system 2 notably comprises an annular cage 4 which is intended to be centered on the axis XX of the pipe 6.

[0053] The cage 4 is provided with means for receiving a buoyancy module to be installed around the pipe. In the example of Figures 1 and 2, the receiving means are presented, for each half-shell 8a of the buoyancy module 8, in the form of a plurality of screwdrivers 10 for bolting the half-shells together, as well as pads 11 with jacks for tightening the half-shells against the pipe.

[0054] The deployment system 2 also comprises means for moving the cage 4 along the pipe 6 (from top to bottom and from bottom to top).

[0055] These means for moving the cage 4 may be in the form of a winch 12 (see figures 4A to 4K) positioned on the deployment ship of the module deployment system and on which a cable 14 is wound which is fixed to the cage 4.

[0056] For example, cable 14 may be an electrical umbilical cable that is connected to a power supply and control system (not shown in the figures) positioned aboard the deployment vessel of the deployment system.

[0057] Alternatively, the cable could be a simple control cable (e.g. using fiber optic sensors), with the cage having its own source of electrical power (batteries or other).

[0058] Alternatively, the cable could be a simple cable, with the cage having its own source of electrical power and being remotely controlled.

[0059] Instead of using a cable to move the cage, it could be autonomous in its movements, for example using motorized wheels.

[0060] The deployment system 2 also comprises guide rollers 13 for the cage 4 along the pipe 6. These guide rollers are advantageously mounted on retractable arms (not shown in the figures) which allow them to move away from the pipe as needed, for example to allow the cage to pass around a module.

[0061] Furthermore, the deployment system may also include additional rollers 15 allowing the system to roll on the sleeves 8 by guiding itself on the joint plane between the two half-shells. These additional rollers 15 make it possible, when raising the cage once the sleeve is fixed on the pipe, to help avoid leaning on the sleeves at the risk of damaging them.

[0062] Figure 3 represents another example of a deployment system 2' of the sleeves for implementing the method according to the invention. In this other example, the cage 4 of the deployment system 2' is designed to be able to accommodate two sleeves 8 at the same time, these two sleeves being positioned one above the other.

[0063] These deployment systems can be used in accordance with the invention according to several different installation methods.

[0064] In general, the installation method according to the invention comprises the following main steps: a) a step of maintaining the pipe 6 in a mainly vertical position; b) a step of installing the two half-shells 8a of the buoyancy module 8 in the deployment system previously described; c) a step of positioning the deployment system at a free upper end of the pipe by centering it on the axis XX thereof; d) a step of lowering the deployment system along the pipe to reach the desired position of the buoyancy module; e) a step of completely closing (via the pads 11) and locking (via the screwdrivers 10) the two half-shells of the buoyancy module on the pipe; and f) a step of raising the deployment system towards the free end of the pipe.

[0065] Such an installation sequence is illustrated by Figures 4A to 4K in the context of an installation of a plurality of adjoining buoyancy modules in order to obtain a continuous distribution of buoyancy. In these figures, step a) of maintaining the pipe 6 in a mainly vertical position is carried out by a deployment vessel of the module deployment system.

[0066] Preferably, step a) of the installation method is carried out on board a deployment vessel of the deployment system which is the laying vessel 16 having constructed the subsea pipeline 6.

[0067] As shown in Figure 4A, two half-shells of a first buoyancy module 8-1 stored on the laying vessel are installed in the cage 4 of the deployment system 2 which has been previously positioned at the free upper end of the pipe 6.

[0068] The deployment system 2 is then lowered along the pipe (here using a winch 12 on which a cable 14 secured to the cage is wound (figure 4B) until the desired position of the first buoyancy module 8-1 is reached (figure 4C).

[0069] As shown in Figure 4D, the first buoyancy module 8-1 is closed and locked onto the pipeline, before the empty cage 4 of the deployment system is raised to the surface (Figure 4E). Once raised onto the deck of the laying vessel (Figure 4F), a second buoyancy module 8-2 is installed inside it (Figure 4G).

[0070] The deployment system 2 is again lowered along the pipe until the second buoyancy module 8-2 is positioned above the first buoyancy module 8-1 and is joined to it (Figure 4H). The second buoyancy module 8-2 is closed and locked onto the pipe, before the empty cage 4 of the deployment system is raised to the surface (Figure 4I). The process is repeated until the desired length for the buoyancy of the pipe is obtained (see Figure 4J which shows the loading of a third buoyancy module 8-3 followed by its descent along the pipe - Figure 4K).

[0071] It will be noted that, when forming a wave shape (or undulation) on a pipe, step d) of the installation method according to the invention comprises the lowering of the deployment system, necessarily followed by a raising of the latter (in the wave). Similarly, step f) of the method provides for a lowering before the raising of the deployment system.

[0072] An alternative embodiment of the installation sequence is illustrated by Figures 5A to 5K in the context of an installation of a plurality of buoyancy modules in order to obtain a distributed distribution of the buoyancy. In these figures, step a) of maintaining the pipe 6 in a mainly vertical position is carried out by a deployment vessel of the deployment system.

[0073] In this embodiment, a fixed buoyancy module 8-1 stored on the laying vessel is positioned at the free upper end of the pipe 6 while the cage 4 of the deployment system is raised to the surface (Figure 5A). Once the cage is raised onto the vessel, the fixed buoyancy module 8-1 is locked into the cage (Figure 5B).

[0074] The cage 4 of the module deployment system is then lowered at least by the height of the fixed buoyancy module 8-1 (Figure 5C). A first sliding buoyancy module 8-2 is then loaded above the fixed buoyancy module 8-1 (Figure 5D) and is fixed to the latter by means of a cable-type fastener 18 (Figure 5E).

[0075] Cage 4 of the module deployment system is again lowered to at least the height of the sliding buoyancy module 8-2 (Figure 5F) in order to load a second sliding buoyancy module 8-3 (Figure 5G). A tether 18 allows the second sliding buoyancy module 8-3 to be fixed to the first sliding buoyancy module 8-2 (figure 5H).

[0076] The train of buoyancy modules 8-1 to 8-3 thus composed and assembled is then lowered along the pipe by lowering the cage 4 of the module deployment system until it reaches the desired position (Figure 5I). The fixed buoyancy module 8-1 is then locked onto the pipe (Figure 5J), before the empty cage 4 of the module deployment system is raised to the surface (Figure 5K).

[0077] It will be noted that in certain embodiments of the method according to the invention, the deployment vessel of the module deployment system may be the laying vessel which constructed the subsea pipeline.

[0078] Thus, in a first embodiment of the method according to the invention, the underwater pipeline is constructed using a J-laying method.

[0079] With J-laying, the pipeline is typically lowered from the pipelaying vessel almost vertically. This type of laying requires a vertical J-lay tower onto which the individual pipe sections are brought one after the other to be assembled and welded to the already constructed section of pipeline held from the laying tower. After welding and coating to improve corrosion protection or apply thermal insulation, the new individual pipe section thus connected to the already constructed section of pipeline is lowered into the sea by moving the pipelaying vessel forward by a lead roughly corresponding to the length of the individual pipe section.

[0080] In the first embodiment of the method according to the invention, the J-laying tower can be located at the stern, at the bow, in the center of the laying vessel or on one side thereof. As for the module deployment system, it is installed directly in the J-laying tower.

[0081] Still in this first mode of implementation of the process, each buoyancy module can be installed from the J-laying tower as the subsea pipeline is constructed.

[0082] In this case, the buoyancy modules of the floating section of the pipeline are installed on the deck of the laying vessel around the pipeline sections to be assembled onto the subsea pipeline under construction.

[0083] Alternatively, each buoyancy module can be installed after the floating section of the subsea pipeline is fully constructed.

[0084] In a second embodiment of the method according to the invention, the deployment vessel of the module deployment system is different from the laying vessel which constructed the subsea pipeline.

[0085] In this second mode of implementation, the subsea pipeline that has been constructed can be recovered from an abandoned position on the seabed (by the laying vessel) to install at least one buoyancy module on board the deployment vessel.

[0086] Alternatively, the subsea pipeline that has been constructed can be transferred directly from the laying vessel to the module deployment system implementation vessel to install the buoyancy module(s).

[0087] In a variant of these two modes of implementation of the method according to the invention, each buoyancy module can be installed by means of a laying platform (also called HOP for “Hang Off Platform” in English) which can be located at the stern, at the bow, in the center or on one side of the ship deploying the module deployment system.

[0088] According to this variant, the section of the subsea pipeline that is intended to be floating can be fully constructed before being transferred to the laying platform to allow the installation of each buoyancy module.

[0089] Alternatively, the section of the subsea pipeline that is intended to be floating may be constructed by assembling several pipeline sections, with the floating section of the pipeline being transferred to the laying platform after assembly of each pipeline section in order to install one or more buoyancy modules thereon.

[0090] In a third embodiment of the method according to the invention, the ship implementing the module deployment system is the unit floating production, storage and offloading (or FPSO for "Floating Production Storage and Offloading" in English) to which the subsea pipeline is ultimately intended to be connected in order to form a riser for production.

[0091] In this third implementation mode, each buoyancy module can be installed from the FPSO to form a SLWR type pipe with one or more corrugations.

[0092] Furthermore, as shown in Figure 6, the module deployment system 2 may be able to move on the FPSO 20 between several risers 22-1 to 22-4 which are connected to the FPSO pending the installation of buoyancy modules 8.

[0093] For this purpose, the module deployment system 2 can be mounted on rails 24 so that it can move along the FPSO between the different risers 22-1 to 22-4.

Claims

Claims

1. Method for installing at least one sleeve (8) around a section of underwater pipe (6) for transporting fluids, in particular an underwater pipe providing a bottom-surface connection of the Steel Catenary Riser or Steel Lazy Wave Riser type, the sleeve being formed by two half-shells (8a) each having an internal face intended to be in contact with the pipe and an external face opposite the internal face, the method comprising: g) maintaining the pipe in a mainly vertical position; h) installing the two half-shells of the sleeve in a deployment system (2); i) positioning the deployment system at a free upper end of the pipe (6) by centering it on an axis (XX) thereof; j) lowering the deployment system along the pipe to reach the desired position of the sleeve; k) completely closing and locking the two half-shells of the sleeve on the pipe;and (l) raising the deployment system towards the free end of the pipe.;

2. Method according to claim 1, in which the installed sleeves are buoyancy modules allowing the creation of a floating section on the pipe.

3. Method according to claim 1, in which the installed sleeves are modules for suppressing vortices from the current and associated vibrations.

4. A method according to any one of claims 1 to 3, wherein the deployment system is deployed from the laying vessel having constructed the subsea pipeline.

5. A method according to claim 4, wherein the subsea pipeline is constructed by a J-lay method using a J-lay tower located at the stern or bow of the laying vessel, in the center of the laying vessel or on one side of it, and the deployment system is deployed from the J-lay tower.

6. The method of claim 5, wherein each sleeve is installed from the J-lay tower as the subsea pipeline is constructed.

7. A method according to claim 6, further comprising the prior installation on the deck of the laying vessel of at least one buoyancy module or at least one anti-vortex module around a portion of pipe to be assembled on the subsea pipe under construction.

8. A method according to claim 5, wherein each sleeve is installed after the section to be covered of the subsea pipeline has been fully constructed.

9. A method according to any one of claims 1 to 3, wherein the deployment system is operated from a vessel other than the laying vessel constructing the subsea pipeline.

10. A method according to one of claims 4 and 9, wherein each sleeve is installed by means of a working platform located at the stern, bow, center or side of the deployment vessel of the deployment system.

11. A method according to claim 10, wherein the section of the subsea pipeline to be covered is fully constructed before being transferred to the work platform to install each sleeve there.

12. A method according to claim 10, wherein the section of the subsea pipeline to be covered is constructed by assembling several pipeline sections, said section of the pipeline to be covered being transferred to the work platform after assembling each pipeline section to install at least one sleeve therein.

13. A method according to any one of claims 1 to 3, wherein the vessel for implementing the deployment system is the floating production unit to which the subsea pipeline is ultimately intended to be connected to form a bottom-surface connection for production.

14. A method according to claim 13, wherein buoyancy module sleeves are installed from the floating production unit to form a SLWR type pipeline with one or more corrugations.

15. A method according to claim 14, wherein the deployment system is capable of moving on the floating production unit between several risers connected thereto to successively install sleeves therein.

16. A method according to any one of claims 13 to 15, wherein the deployment system is used to retrofit sleeves forming anti-vortex modules onto an SCR or SLWR type pipeline to address vortex and vibration problems not anticipated in the initial design of the pipeline.

17. System (2) for implementing the method according to any one of claims 1 to 16, comprising: - an annular cage (4) intended to be centered on the axis (XX) of the pipe (6) and comprising means (10) for receiving at least one sleeve (8); and - means (12, 14) for moving the cage along the pipe.

18. System according to claim 17, wherein the means for moving the cage comprise a winch (12) connected to a cable (14) fixed to the cage (4).

19. The system of claim 18, wherein the cable (14) is an electrical umbilical cable connected to a power supply and a control system to provide the power and control locally necessary for movement of the cage.

20. System according to any one of claims 17 to 19, in which the means for moving the cage comprise a motorization system integral with the cage making it possible to assist in the movement and positioning along the pipe.

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