Method for installing a sleeve around a section of a submarine fluid transport pipeline

Abstract

Method for installing a sleeve around a section of a subsea fluid transport pipeline. The invention relates to a method for installing at least one sleeve (8) around a section of a subsea fluid transport pipeline (6), the sleeve being formed by two half-shells. The method comprises maintaining the pipeline in a predominantly vertical position, installing the two half-shells of the sleeve in a deployment system (2), positioning the deployment system at a free upper end of the pipeline (6) by centering it on an axis (XX) thereof, lowering the deployment system along the pipeline to reach the desired position of the sleeve, fully closing and locking the two half-shells of the sleeve onto the pipeline, and raising the deployment system back towards the free end of the pipeline. Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for installing a sleeve around a section of a submarine fluid transport pipeline. Technical field

[0001] The present invention relates to the general field of subsea pipelines for transporting fluids that provide a seabed-to-surface connection for the transfer of hydrocarbons, for example oil and gas, from subsea production wells. This type of seabed-to-surface connection can also be used to transfer other fluids between the surface and the seabed, such as treated water or carbon dioxide.

[0002] It relates more specifically to a method of installing sleeves (such as buoyancy modules or vortex suppression modules) around a section of a subsea bottom-to-surface pipeline, as well as a system for implementing such a method. Previous technique

[0003] In the field of offshore oil and gas production, subsea pipelines called "risers" 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 riser, the steel catenary riser (SCR) is a well-known 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] The "Steel Lazy Wave Riser" (or SLWR) is also known. This steel pipe is designed to allow significantly greater decoupling than an SCR-type riser between the movements of the production unit on the surface and the movements of the line on the seabed. The "lazy wave" configuration refers to the specific shape given to this type of subsea pipe. This pipe is deliberately arranged to form one or more undulations (shape waves) in the vertical plane, these undulations enabling increased decoupling.

[0006] These undulations are typically obtained by placing a plurality of buoyancy modules (buoy type) around a portion that is desired to be afloat. of the pipe, 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 offers several advantages over an SCR pipeline. It reduces the mechanical stresses exerted on the pipeline, thereby increasing its service life and reducing the risk of failure. It allows for greater vertical or lateral offsets of the floating unit to which it is connected at the surface. Furthermore, it provides better protection against severe weather phenomena such as storms, by allowing the pipeline and the float to move more freely. This additional freedom is particularly important at great depths where the impact of surface and pipeline displacements on stress levels in the steel is greater.

[0008] Furthermore, subsea seabed-to-surface pipelines can be constructed from unit-length pipeline sections that are assembled on board the laying vessel, then connected to the section of pipeline already constructed, and finally lowered into the sea as they are joined. 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 method, 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 sections are brought one after the other by means of a loading arm from a horizontal position on the deck of the laying vessel to be assembled and welded to the section of pipeline already constructed and held from the laying tower. After welding and the application of a coating to improve corrosion protection or provide thermal insulation, the new individual pipeline section, thus connected to the section of pipeline already constructed, is lowered into the sea by moving the laying vessel forward by a distance roughly corresponding to the length of the individual pipeline section.

[0010] The pipeline is therefore gradually lowered into the water and deposited on the seabed by progressively joining sections of pipeline to it. 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 pipeline being laid. The individual pipeline sections are therefore typically brought by the loading arm in a vertical position into the tower above the assembly station, transferred to said tower via the (pipe-gripping) clamps of said arm and those of the tower, and then moved vertically to be joined at the assembly station to the section of pipeline 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 pipelines, SCR and SLWR, connect the seabed to a surface unit through the water column and are therefore subject to submarine currents. The flow of a fluid around a cylindrical pipeline is likely to generate vortices that can cause the pipeline to vibrate. If these vibrations resonate with the pipeline's natural modes, they can lead to significant mechanical fatigue in the pipeline. To prevent the formation of these vortices or significantly reduce their impact, and thus avoid the associated design constraints, anti-vortice modules can be installed at strategic locations along the pipeline or even along its entire length. These anti-vortice modules are typically formed from cylindrical shell sections to the outside of which fins are attached, arranged to form propellers along the pipeline.These anti-vortex modules can be used for both SCR and SLWR type risers. In the case of the latter, they are generally installed on the portion of piping located above the floating section (between this section and the surface production unit). The buoyancy modules can also incorporate fins providing an anti-vortex function on their external surface.

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

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

[0015] Although this is a proven method, this approach generally requires maintaining empty spaces (exclusion zones) on the guide element to allow handling by the loading arm and its grippers, as well as by the gripping elements (grippers) in the tower. Therefore, continuous distribution cannot be achieved with this installation method.

[0016] It is also known to use a V-shaped trolley system (called "V-Trolley"). This system, located for example in the assembly station of the laying tower below its clamps, is used to load the flow modules stability or vortex suppression modules on the pipe element once the unit length section has been connected to the pipe being laid and held by the lathe.

[0017] Such a system theoretically allows for a continuous distribution of buoyancy modules around the pipeline. However, it is limited to small buoyancy modules and vortex suppression modules (because they must pass through the tower assembly station), and it is a manual (or semi-manual) system. Furthermore, this system also requires available space in the assembly station, both for supplying modules and for moving around and approaching the section of pipeline to be equipped. Assembly stations can sometimes be congested with equipment necessary for connecting the unit-length section of pipeline to the section being installed. For example, the presence of equipment necessary for welding the two sections of pipeline, for inspecting this weld, or for applying the thermal or anti-corrosion coating after welding.In this case, the V-Trolley system cannot be installed in the assembly station.

[0018] To achieve continuous distribution of buoyancy modules with an efficient laying rate, the semi-automatic buoy loading system described in publication WO2022 / 070160 A1 has been proposed. This system allows the buoyancy modules to be loaded and installed onto the conduit element after it has been welded into the laying tower, thus eliminating interference problems with the laying tower and the clamps of the loading arm and the tower. However, this solution requires significant space available for the positioning and operation of the loading system, space which is not always available, depending on the architecture of the boat deck, the tower, and the assembly station. For example, for the SAIPEM FDS laying boat, this equipment could not have been used as designed because the assembly station did not allow for these operations. Description of the invention

[0019] The invention therefore aims to propose a method of installing sleeves (buoyancy modules or vortex suppression modules) which allows for both a distributed and a continuous distribution of said sleeves and which is usable on most laying vessels.

[0020] In accordance with the invention, this objective is achieved by means of a method for installing at least one sleeve around a section of a subsea fluid transport pipeline, in particular a subsea pipeline providing a seabed-to-surface connection of the type Steel Catenary Riser or Steel Lazy Wave Riser, the sleeve being formed by two half-shells each having an inner face intended to be in contact with the pipe and an outer face opposite the inner face, the process comprising:

[0021] a) maintaining the pipe in a predominantly vertical position;

[0022] b) the installation of the two half-shells of the sleeve in a deployment system;

[0023] c) positioning the deployment system at a free upper end of the conduit by centering it on an axis of the conduit;

[0024] d) the descent of the deployment system along the pipe to reach the desired position of the sleeve;

[0025] e) the complete closure and locking of the two half-shells of the sleeve onto the pipe; and

[0026] f) the raising of the deployment system towards the free end of the conduit.

[0027] 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 was partially constructed and then laid on the seabed before being recovered later with another vessel so that buoyancy modules could be installed on it).

[0028] Furthermore, the method according to the invention allows buoyancy modules or vortex suppression modules to be installed in a distributed manner as well as in a continuous distribution.

[0029] 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.

[0030] In one embodiment, the deployment system is deployed from the laying vessel that constructed the subsea pipeline.

[0031] In this case, the underwater pipeline can be constructed using a J-laying method with a J-laying tower located at the stern or bow of the laying vessel, in the center of the laying vessel or on one side thereof, and the deployment system is deployed from the J-laying tower.

[0032] Each sleeve can be installed from the J-laying tower as the subsea pipeline is constructed. In this case, the method may further include the prior installation on the deck of the laying vessel of at least one buoyancy or anti-vortex module around a section of pipeline to be assembled onto the subsea pipeline under construction.

[0033] Alternatively, each sleeve can be installed once the section to be covered of the subsea pipeline is fully constructed.

[0034] In another embodiment, the deployment system is implemented from a vessel different from the laying vessel constructing the subsea pipeline.

[0035] Each sleeve can be installed by means of a work platform located at the stern, bow, center or side of the deployment vessel of the deployment system.

[0036] In this case, the section to be covered of the subsea pipeline can be entirely constructed before being transferred to the working platform to install each sleeve.

[0037] Alternatively, the section to be covered of the subsea pipeline can be constructed by assembling several pipeline sections, said section to be covered of the pipeline being transferred to the working platform after assembly of each pipeline section to install at least one sleeve.

[0038] In yet another embodiment, the deployment system implementation vessel is the floating production unit to which the subsea pipeline is ultimately intended to be connected to form a seabed-to-surface link for production.

[0039] In this embodiment, sleeves forming buoyancy modules can be installed from the floating production unit to form an SLWR-type conduit with one or more corrugations. In this case, the deployment system can be adapted to move along the floating production unit between several risers connected to it in order to successively install sleeves.

[0040] Still in this embodiment, the deployment system can also be used to install a posteriori sleeves forming anti-vortex modules on an SCR or SLWR type pipeline to remedy vortex and vibration problems not foreseen during the initial design of the pipeline.

[0041] The invention also relates to a system for implementing the process 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.

[0042] The means for moving the cage may include a winch connected to a cable fixed to the cage.

[0043] In this case, the cable may be an electrical umbilical cable connected to a power supply and a control system to provide the necessary power and control locally to move the cage.

[0044] Alternatively, the means for moving the cage may include a motorization system attached to the cage to assist in movement and positioning along the pipe. The motorization then facilitates the dismantling The cage is positioned along the pipeline, and this movement is not achieved solely through the cage's own weight. This propulsion system can utilize rollers in contact with the pipeline or even tracks. Brief description of the drawings

[0045] [Fig.1] Fig.1 is a longitudinal cross-sectional view of a module deployment system according to the invention.

[0046] [Fig.2] The [Fig.2] is a cross-sectional view along ILII of the [Fig.l].

[0047] [Fig.3] Fig.3 is a longitudinal cross-sectional view of a deployment system two-story modules according to another embodiment of the invention.

[0048] [Fig.4A] to [Fig.4K] Figures 4A to 4K represent a sequence of sleeve installation according to an embodiment of the invention.

[0049] [Fig.5A] to [Fig.5K] Figures 5A to 5K represent a sequence of sleeve installation according to an embodiment of the invention.

[0050] [Fig.6] Fig.6 shows an example of application of the method according to the invention to an FPSO. Description of the implementation methods

[0051] The invention relates to a method of installing buoyancy modules or vortex suppression modules from current and associated vibrations (also called anti-vortex modules) around a floating section of a subsea fluid transport pipeline, and in particular a pipeline of type SCR (for "Steel Catenary Riser") or of type SLWR (for "Steel Lazy Wave Riser").

[0052] Typically, a subsea bottom-to-surface connection pipeline of the SLWR type is a steel pipeline which is constructed according to a J-laying, S-laying or uncoiling method and which has one or more undulations (shape waves) in order to allow greater flexibility and better absorption of float movements due to currents or waves.

[0053] These undulations are generally obtained by placing a plurality of buoyancy modules (buoy type) around a floating portion of the pipe, either spaced apart from each other (according to a distributed distribution of buoyancy), or joined together (according to a continuous distribution of buoyancy).

[0054] Each buoyancy module typically takes the form of two half-shells, each having an inner face intended to be in contact with the pipe and an outer face opposite to the inner face.

[0055] A more conventional SCR-type underwater seabed-surface connection pipeline will not have any undulation and will thus present a catenary with a more direct trajectory towards the seabed, without buoyancy modules.

[0056] SCR or SLWR type conduits can also be equipped with modules Anti-vortex devices. These are also typically formed from two half-shells to be assembled around the pipe.

[0057] Figures 1 and 2 represent an example of a deployment system 2 of the buoyancy modules for the implementation of the method according to the invention (the same method applies to the deployment of anti-vortex modules).

[0058] This deployment system 2 includes in particular an annular cage 4 which is intended to be centered on the axis XX of the conduit 6.

[0059] The cage 4 is equipped 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, 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 jack pads 11 for clamping the half-shells against the pipe.

[0060] The deployment system 2 also includes means for moving the cage 4 along the conduit 6 (up and down).

[0061] These means for moving the cage 4 may take the form of a winch 12 (see figures 4A to 4K) positioned on the deployment vessel of the module deployment system and on which is wound a cable 14 which is fixed on the cage 4.

[0062] For example, cable 14 may be an electrical umbilical cable which is connected to a power supply and a control system (not shown in the figures) positioned on board the deployment vessel of the deployment system.

[0063] Alternatively, the cable could be a simple control cable (for example using fiber optic sensors), the cage being equipped with its own source of electrical power (batteries or other).

[0064] Alternatively, the cable could be a simple cable, the cage being equipped with its own source of electrical power and being remotely controlled.

[0065] Instead of a cable as a means to move the cage, it could be autonomous in its movements thanks, for example, to motorized wheels.

[0066] The deployment system 2 further includes guide rollers 13 of the cage 4 along the conduit 6. These guide rollers are advantageously mounted on retractable arms (not shown in the figures) which allow them to move away from the conduit as needed, for example to allow the cage to pass around a module.

[0067] Furthermore, the deployment system may also include additional rollers 15 allowing the system to roll over the sleeves 8, guided by the joint between the two half-shells. These additional rollers 15 help prevent the cage from bearing down on the sleeves during retraction once the sleeve is fixed to the pipe, thus avoiding damage.

[0068] Figure 3 represents another example of a 2' sleeve deployment system for the implementation of the method according to the invention. In this other example, the cage 4 of the deployment system 2' is designed to accommodate two sleeves 8 at the same time, these two sleeves being positioned one above the other.

[0069] These deployment systems can be used in accordance with the invention using several different installation methods.

[0070] In general, the installation method according to the invention comprises the following main steps: a. a stage of maintaining the pipe 6 in a predominantly 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 conduit by centering it on the XX axis of the conduit; d. a descent stage of the deployment system along the pipeline to reach the desired position of the buoyancy module; e. a complete closing step (via the pads 11) and locking (via the screws 10) of the two half-shells of the buoyancy module onto the pipe; and f. a step of raising the deployment system towards the free end of the pipe.

[0071] Such an installation sequence is illustrated in Figures 4A to 4K for the installation of a plurality of contiguous buoyancy modules to obtain a continuous buoyancy distribution. In these figures, step a) of maintaining the conduit 6 in a predominantly vertical position is carried out by a deployment vessel of the module deployment system.

[0072] Preferably, step a) of the installation process is carried out on board a deployment vessel of the deployment system which is the laying vessel 16 which constructed the subsea pipeline 6.

[0073] As shown in [Fig.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 level of the free upper end of the pipe 6.

[0074] The deployment system 2 is then lowered along the pipe (here using a winch 12 on which is wound a cable 14 attached to the cage ([Fig.4B]) until it reaches the desired position of the first buoyancy module 8-1 ([Fig.4C]).

[0075] As shown in [Fig. 4D], the first buoyancy module 8-1 is closed and locked onto the pipe, before the empty cage 4 of the deployment system is raised to the surface ([Fig. 4E]). Once raised onto the deck of the laying vessel ( [Fig.4F]), a second buoyancy module 8-2 is installed inside it ( [Fig.4G]).

[0076] 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, flush against it ([Fig. 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 ([Fig. 4I]). The process is repeated until the desired length for the pipe buoyancy is achieved (see [Fig. 4J], which shows the loading of a third buoyancy module 8-3 followed by its descent along the pipe - [Fig. 4K]).

[0077] It should be noted that, during the formation of a wave (or undulation) on a pipe, step d) of the installation method according to the invention includes lowering the deployment system, necessarily followed by its ascent (within the wave). Similarly, step f) of the method involves lowering the deployment system before it is raised.

[0078] An alternative embodiment of the installation sequence is illustrated in Figures 5A to 5K for the installation of a plurality of buoyancy modules to obtain a distributed buoyancy distribution. In these figures, step a) of maintaining the conduit 6 in a predominantly vertical position is carried out by a deployment vessel of the deployment system.

[0079] In this embodiment, a fixed buoyancy module 8-1 stored on the laying vessel is positioned at the free upper end of the conduit 6 while the cage 4 of the deployment system is raised to the surface ([Fig. 5A]). Once the cage is raised on the vessel, the fixed buoyancy module 8-1 is locked into the cage ([Fig. 5B]).

[0080] The cage 4 of the module deployment system is then lowered to at least the height of the fixed buoyancy module 8-1 ([Fig.5C]). A first sliding buoyancy module 8-2 is then loaded above the fixed buoyancy module 8-1 ([Fig.5D]) and is fixed to the latter by means of a cable-type attachment 18 ([Fig.5E]).

[0081] The cage 4 of the module deployment system is lowered again to at least the height of the sliding buoyancy module 8-2 ([Fig. 5F]) in order to load a second sliding buoyancy module 8-3 ([Fig. 5G]). A fastener 18 allows the second sliding buoyancy module 8-3 to be attached to the first sliding buoyancy module 8-2 ([Fig. 5H]).

[0082] The train of buoyancy modules 8-1 to 8-3, thus assembled, is then lowered along the pipeline by lowering the cage 4 of the module deployment system until it reaches the desired position ([Fig. 51]). The fixed buoyancy module 8-1 is then locked onto the pipeline ([Fig. 5J]), before the cage 4 void of the module deployment system is not brought back to the surface ([Fig.5K] )•

[0083] It should 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 that constructed the subsea pipeline.

[0084] Thus, in a first embodiment of the process according to the invention, the underwater pipeline is constructed according to a J-laying method.

[0085] With J-laying, the pipeline is typically lowered from the laying vessel almost vertically. This type of laying requires a vertical J-laying tower onto which the individual pipeline sections are brought one after the other to be assembled and welded to the section of pipeline already constructed and held from the laying tower. After welding and the application of a coating to improve corrosion protection or provide thermal insulation, the new individual pipeline section, thus connected to the section of pipeline already constructed, is lowered into the sea by moving the laying vessel forward by a distance roughly corresponding to the length of the individual pipeline section.

[0086] In the first embodiment of the method according to the invention, the J-shaped laying tower can be located at the stern, the bow, the center of the laying vessel, or on one side thereof. The module deployment system is installed directly in the J-shaped laying tower.

[0087] Still in this first method of implementing the process, each buoyancy module can be installed from the J-shaped laying tower as the subsea pipeline is being constructed.

[0088] In this case, the buoyancy modules of the floating section of the pipeline are installed on the deck of the laying vessel around the portions of pipeline to be assembled on the subsea pipeline under construction.

[0089] Alternatively, each buoyancy module can be installed once the floating section of the subsea pipeline is fully constructed.

[0090] In a second embodiment of the method according to the invention, the deployment vessel for the module deployment system is different from the laying vessel that constructed the subsea pipeline.

[0091] In this second embodiment, the underwater 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.

[0092] Alternatively, the underwater 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).

[0093] 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 deployment vessel of the module deployment system.

[0094] According to this variant, the section of the subsea pipeline which is intended to be floating can be fully constructed before being transferred to the laying platform to allow the installation of each buoyancy module.

[0095] Alternatively, the section of the subsea pipeline intended to be floating can be constructed by assembling several pipeline sections, 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.

[0096] In a third embodiment of the method according to the invention, the vessel for implementing the module deployment system is the floating production, storage and offloading unit (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.

[0097] In this third embodiment, each buoyancy module can be installed from the FPSO to form an SLWR-type conduit with one or more undulations.

[0098] Furthermore, as shown in [Fig.6], the module deployment system 2 can be capable of moving 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.

[0099] 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

Demands

1. A method for installing at least one sleeve (8) around a section of a subsea pipeline (6) for transporting fluids, in particular a subsea pipeline providing a seabed-to-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 inner face intended to be in contact with the pipeline and an outer face opposite the inner face, the method comprising: a. maintaining the pipeline in a predominantly vertical position; b. installing the two half-shells of the sleeve in a deployment system (2); c. positioning the deployment system at a free upper end of the pipeline (6) by centering it on an axis (XX) thereof; d. lowering the deployment system along the pipeline to reach the desired position of the sleeve; e.the complete closure and locking of the two half-shells of the sleeve onto the pipe; and f. the raising of the deployment system towards the free end of the pipe.

2. A method according to claim 1, wherein the installed sleeves are buoyancy modules enabling the creation of a floating section on the pipe.

3. Method according to claim 1, wherein the installed sleeves are modules for suppressing vortices arising 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 that constructed the subsea pipeline.

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

6. Method according to claim 5, wherein each sleeve is installed from the J-laying tower as the subsea pipeline is constructed.

7. Method according to claim 6, further comprising 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 pipeline under construction.

8. Method according to claim 5, wherein each sleeve is installed once the section to be covered of the subsea pipeline is fully constructed.

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

10. A method according to any 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 to be covered of the subsea pipeline is entirely constructed before being transferred to the working platform for the installation of each sleeve.

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

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

14. A method according to claim 13, wherein sleeves forming buoyancy modules are installed from the floating production unit to form an SLWR-type conduit 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 install su- cessively of the sleeves.

16. A method according to any one of claims 13 to 15, wherein the deployment system is used to install a posteriori sleeves forming anti-vortex modules on an SCR or SLWR type pipeline to remedy vortex and vibration problems not foreseen during 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 receiving means (10) for 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 include a winch (12) connected to a cable (14) fixed on the cage (4).

19. System according to 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 necessary locally for the movement of the cage.

20. System according to any one of claims 17 to 19, wherein the means for moving the cage include a motorization system attached to the cage to assist in movement and positioning along the conduit.

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