Method of installing a sleeve around a section of subsea fluid transport pipe

Abstract

Method for installing a sleeve around a section of underwater fluid transport pipe The invention relates to a method for installing at least one sleeve (8) around a section of underwater fluid transport pipe (6), the sleeve being formed by two half-shells, the method comprising maintaining the pipe in a mainly 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 pipe (6) by centering it on an axis (XX) thereof, lowering the deployment system along the pipe to reach the desired position of the sleeve, completely closing and locking the two half-shells of the sleeve on the pipe, and raising the deployment system towards the free end of the pipe. Figure for abstract: Fig. 1.

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] 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-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, we know the steel catenary riser (or SCR for "Steel Catenary Riser" in English) which is a common method of connecting a subsea pipeline to a deep-water floating oil production platform. SCRs are used to transfer fluids such as oil, gas, injection water, etc. between platforms and subsea pipelines.

[0005] Also known is the "Steel Lazy Wave Riser" (or SLWR) which is a steel pipe designed to allow a 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 pipe. Indeed, this pipe is deliberately arranged in such a way as to form one or more undulations (shaped waves) in the vertical plane, these undulations allowing the 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 floating. of the pipe, either by being spaced 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] A SLWR pipe has several advantages over an SCR pipe. It reduces the mechanical stresses placed on the pipe, 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 pipe and float to move more freely. This additional freedom is particularly important at great depths where the impact of surface and pipe movements is greater on the stress levels in the steel.

[0008] Furthermore, the underwater bottom-surface connecting pipes can be constructed from elements of unit length of pipe which are assembled on board the laying vessel, then connected to the portion of pipe already constructed and finally lowered into the sea as they are connected. This laying can be carried out by means of 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 practically 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 portion held from the laying tower. After the welding operations and the application of a coating to improve corrosion protection or to apply thermal insulation, the new individual pipeline element thus connected to the already constructed pipeline portion is lowered into the sea by moving the laying vessel forward by a lead corresponding generally to the length of the individual pipeline element.

[0010] The pipe is then lowered gradually into the water and placed on the bottom by gradually joining pieces of pipe there. The welding and coating operations are typically carried out in an assembly station located under the main part of the tower and above the portion 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) clamps of said arm and those of the tower, then translated vertically to be joined at the assembly station to the portion 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 which can cause the pipe to vibrate. If these vibrations resonate with the natural modes of the pipe, they can cause significant mechanical fatigue in the pipe. To avoid 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 of portions of cylindrical shells to the outside of which fins are attached, arranged to form propellers along the pipe.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 J-lay.

[0014] For distributed distribution on an SLWR pipeline, the buoyancy modules may be pre-installed on the deck of the laying vessel after 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 closed and locked in translation and rotation on a portion of the pipeline element. This same method may also be used to install vortex suppression modules.

[0015] Although a proven method, this approach generally requires maintaining empty 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. It is therefore not possible to achieve a continuous distribution with this installation method.

[0016] It is also known to use a V-carriage system (called "V-Trolley"). This system, located for example in the assembly station of the laying tower below the latter's grippers, 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 thus makes it possible in theory to obtain a continuous distribution of the buoyancy modules around the pipe. 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. In addition, this system also requires having the space available in said assembly station, to supply modules but also to move and approach the section of pipe to be equipped. However, the 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, it is possible to 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 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 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 is not necessarily always available, depending on the architecture of the ship deck, the tower and the assembly station. For example, for the SAIPEM FDS laying ship, 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 aim is achieved by means of a method of 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 type Steel Catenary Riser or Steel Lazy Wave Riser, 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:

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

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

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

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

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

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

[0027] The method according to the invention is remarkable in that it is compatible with all methods of laying subsea pipes with a simple adaptation of the deployment system. This method is also compatible with other sequences of laying the subsea pipe (for example, the subsea pipe has been partly constructed then laid on the seabed before being recovered later with another vessel so that buoyancy modules can be installed therein).

[0028] 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.

[0029] The installed sleeves may 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 subsea pipeline may be constructed in 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 thereof, and the deployment system is deployed from the J-lay tower.

[0032] 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 pipeline to be assembled onto the subsea pipeline under construction.

[0033] Alternatively, each sleeve may be installed after the section of the subsea pipeline to be covered has been fully constructed.

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

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

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

[0037] Alternatively, the section of the underwater pipeline to be covered may be 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.

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

[0039] 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.

[0040] Still in this embodiment, the deployment system can also be used to retrospectively install 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 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.

[0042] The means for moving the cage may comprise 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 power and control locally necessary for moving the cage.

[0044] Alternatively, the means for moving the cage may comprise a motorization system integral with the cage to assist in moving and positioning along the pipe. The motorization then makes it easier to move the cage. placement of the cage along the pipe, this movement not being done solely thanks to the cage's own weight. This motorization can rely on rollers in contact with the pipe or even tracks. Brief description of the drawings

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

[0046] [Fig.2] [Fig.2] is a sectional view along ILII of [Fig.l].

[0047] [Fig.3] [Fig.3] is a longitudinal 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 installation of sleeves according to an embodiment of the invention.

[0049] [Fig.5A] to [Fig.5K] Figures 5A to 5K represent a sequence of installation of sleeves 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 embodiments

[0051] 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.

[0052] Typically, a SLWR type subsea bottom-to-surface pipeline is a steel pipeline that is constructed using a J-lay, S-lay, or unrolled lay method and has one or more undulations (wave shapes) to provide greater flexibility and better absorption of float movement 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 by being spaced from each other (according to a distributed distribution of buoyancy), or by being joined to each other (according to a continuous distribution of buoyancy).

[0054] Each buoyancy module is typically 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.

[0055] 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.

[0056] SCR or SLWR type pipes can also be equipped with modules anti-vortex. These are also typically formed of 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 implementing the method according to the invention (the same method applies to the deployment of anti-vortex modules).

[0058] This deployment system 2 notably comprises an annular cage 4 which is intended to be centered on the axis XX of the pipe 6.

[0059] 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.

[0060] 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).

[0061] These means for moving the cage 4 may be in the form of a winch 12 (see FIGS. 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.

[0062] For example, the cable 14 may be an electrical umbilical cable that is connected to a power supply and 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 (e.g. using fiber optic sensors), with the cage provided with its own source of electrical power (batteries or other).

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

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

[0066] 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.

[0067] Furthermore, the deployment system may also comprise 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.

[0068] [Fig.3] represents another example of a system for deploying 2' 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.

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

[0070] Generally speaking, 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 XX axis 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 complete closing (via the pads 11) and locking (via the screwdrivers 10) of 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.

[0071] 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 the buoyancy. In these figures, step a) of maintaining the pipe 6 in a mainly vertical position is carried out by a ship deploying the module deployment system.

[0072] 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.

[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 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 a cable 14 secured to the cage is wound ([Fig.4B]) until the desired position of the first buoyancy module 8-1 is reached ([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 and is joined to 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 buoyancy of the pipe is obtained (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 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.

[0078] An alternative embodiment of the installation sequence is illustrated by FIGS. 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 ship 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 pipe 6 while the cage 4 of the deployment system is raised to the surface ([Fig.5A]). Once the cage is raised onto the vessel, the fixed buoyancy module 8-1 is locked in the cage ([Fig.5B]).

[0080] The cage 4 of the module deployment system is then lowered at least by 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 fastener 18 ([Fig.5E]).

[0081] The cage 4 of the module deployment system is again lowered at least by 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 makes it possible to fix the second sliding buoyancy module 8-3 on the first sliding buoyancy module 8-2 ([Fig.5H]).

[0082] 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 ([Fig.51]). The fixed buoyancy module 8-1 is then locked onto the pipe ([Fig.5J]), before the cage 4 empty module deployment system is raised to the surface ([Fig.5K])•

[0083] 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 having constructed the subsea pipeline.

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

[0085] With J-laying, the pipeline is typically lowered from the pipe-laying vessel practically vertically. This type of laying requires a vertical J-laying tower onto which the individual pipe elements are brought one after the other to be assembled and welded to the already constructed pipe portion held from the laying tower. After welding and applying a coating to improve corrosion protection or apply thermal insulation, the new individual pipe element thus connected to the already constructed pipe portion is lowered into the sea by moving the pipe-laying vessel forward by a lead corresponding generally to the length of the individual pipe element.

[0086] In the first embodiment of the method according to the invention, the J-laying tower may 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.

[0087] Still in this first mode of implementation of the method, each buoyancy module can be installed from the J-laying tower as the subsea pipeline is 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 pipeline portions to be assembled on the subsea pipeline under construction.

[0089] Alternatively, each buoyancy module may be installed after 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 of the module deployment system is different from the laying vessel having constructed the subsea pipeline.

[0091] In this second embodiment, 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.

[0092] 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) therein.

[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 ship deploying the module deployment system.

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

[0095] Alternatively, the section of the subsea pipeline that is intended to be floating may 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 therein.

[0096] In a third embodiment of the method according to the invention, the vessel 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 pipe 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 a SLWR type pipe with one or more corrugations.

[0098] Furthermore, as shown in [Fig.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.

[0099] For this purpose, the module deployment system 2 can be mounted on rails 24 in order to be able to 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: a. maintaining the pipe in a mainly 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 pipe (6) by centering it on an axis (XX) thereof; d. lowering the deployment system along the pipe to reach the desired position of the sleeve; e.the complete closing and locking of the two half-shells of the sleeve on 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 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. The method of claim 4, wherein the subsea pipeline is constructed in 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 to one side thereof, 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 sections of pipeline, said section of the pipeline to be covered being transferred to the work platform after assembling each section of pipeline 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 pipe with one or more corrugations.

15. A method according to claim 14, wherein the deployment system is adapted to move on the floating production unit between several risers connected thereto to install suc- sleeves.

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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