Reinforcement for flexible pipe with a disposable composite profile section and a reinforcing strip

Description

[0001] The present invention relates to longitudinal tensile reinforcement layers (generally called armor) for a flexible tubular pipeline for transporting petroleum fluids. The flexible pipeline can be used in offshore oil and gas production.

[0002] The flexible pipes covered by the present invention are formed from a series of concentric and superimposed layers and are described as unbonded because these layers exhibit a certain degree of freedom of movement relative to one another under bending stress. These flexible pipes comply, among other things, with the recommendations of the standards API 17J "Specification for Unbonded Flexible Pipe" (4th edition, May 2014) and API 17B "Recommended Practice for Flexible Pipe" (5th edition, May 2014) published by the American Petroleum Institute. The constituent layers of the flexible pipes include, in particular, polymer sheaths that generally provide a sealing function, and reinforcing layers designed to withstand mechanical stresses and formed by windings of metal strip, metal wire, various bands, or profiles of composite materials.

[0003] These flexible pipelines are used, in particular, to transport hydrocarbons such as oil or gas from subsea equipment located on the seabed, for example, a wellhead, to a floating production unit on the surface. Such pipelines can be deployed at great depths, commonly more than 2,000 meters, and must therefore be able to withstand hydrostatic pressures of several hundred bars. Furthermore, they must also be able to withstand the very high pressure of the hydrocarbons being transported, which can also reach several hundred bars.

[0004] When the flexible pipeline is in operation, it can be subjected to significant static and dynamic loads, which can lead to fatigue. The most severe loads are generally observed in the upper section of risers connecting the seabed to the surface. In this area, the flexible pipeline is subjected to high static tensile stress due to its weight, compounded by dynamic tensile and transverse bending stresses caused by the movements of the floating production unit under the influence of swell and waves. For the section of the flexible pipeline extending along the seabed (flowlines), the applied loads are primarily static.

[0005] The most commonly used unbonded flexible pipelines in the offshore oil industry generally comprise, from the inside out, an inner carcass made of a profiled stainless steel strip wound helically with a short pitch in turns stapled to one another, said inner carcass serving primarily to prevent the flexible pipeline from being crushed under the effect of external pressure, an inner sealing sheath made of polymer, a pressure arch made of at least one shaped metal wire stapled and wound helically with a short pitch, said pressure arch serving to resist the radial forces related to the internal pressure, layers of tensile armor formed of long-pitch helical windings of metal wires or composite profiles, said layers of tensile armor being intended to resist the longitudinal forces to which the flexible pipeline is subjected,and finally, an external sealing sheath designed to protect the reinforcing layers from seawater. In this application, a short-pitch winding is defined as any winding with a helix angle whose absolute value is close to 90 degrees, in practice between 70 and 90 degrees relative to the longitudinal axis of the flexible pipe. A long-pitch winding, on the other hand, refers to any winding whose helix angle is less than or equal to 55 degrees in absolute value relative to the longitudinal axis of the flexible pipe.

[0006] The internal carcass provides the flexible pipe with sufficient collapse resistance to withstand high external pressures, particularly hydrostatic pressure when the flexible pipe is submerged at great depths (1000m, or even 2000m, or more), or the external contact pressures experienced during handling and installation operations at sea. A flexible pipe with an internal carcass is called a rough bore pipe because the innermost element is the internal carcass, which forms a rough bore due to the gaps between the metal coils of the stapled strip.

[0007] The primary function of the pressure arch is to allow the inner sealing liner to withstand, without bursting, the pressure exerted by the petroleum fluid transported in the pipeline. The outer face of the inner sealing liner bears against the inner face of the pressure arch. The pressure arch also contributes to improving the crush resistance of the inner casing, particularly by limiting the potential for deformation of the inner casing under hydrostatic pressure.

[0008] The primary function of tensile reinforcement layers is to resist longitudinal forces, particularly those related to the suspended weight of the flexible pipeline when it is installed on the seabed from a surface-laying vessel. In the case of a riser pipeline permanently connecting a seabed installation to a floating surface equipment, these longitudinal forces related to the suspended weight are constantly exerted. When the pipeline is submerged at great depths, the longitudinal forces related to the suspended weight during installation and / or operation can reach several hundred tons.

[0009] Tensile reinforcement layers are generally made of metal or a composite material. Metallic tensile reinforcement, traditionally used for axial reinforcement of flexible pipelines, presents a weight problem at great depths. Indeed, depending on the application, there may be a depth beyond which increasing the cross-section of the steel reinforcement increases the line's own weight more than it increases the axial strength of the flexible pipeline. The load at the top of the riser during production or the flowline during installation then exceeds its capacity. Installation of the line becomes impossible because the suspended weight exceeds the load-bearing capacity of the installation equipment.

[0010] For several years, work has been underway to replace these metal wires with composite material profiles, which have the advantage of a much lower density, and therefore mass, than metals. These composite material profiles must, among other things, comply with the recommendations of the standard document DNV-OS-C501 "Composite Components" (November 2013) published by Det Norske Veritas. The reduction in mass achieved in flexible structures has numerous consequences: it allows, with the same installation vessel, the installation of flexible cables at greater depths; it also allows the use of installation vessels with a smaller installation capacity, potentially resulting in reduced installation costs; finally, the reduction in mass of flexible cables used as risers (lines connecting the seabed to the floating surface unit) can affect the sizing of the floating units.In contrast, composite tensile armor has lower compressive strength than metallic tensile armor, which poses a problem for loads on the seabed, dominated by significant external pressure.

[0011] The composite materials discussed for longitudinal reinforcement applications consist of continuous reinforcing fibers (typically carbon, glass, or aramid fibers) embedded in a polymer resin (thermosetting, thermoplastic, etc.). Current research focuses primarily on a carbon fiber composite material with a thermosetting epoxy matrix, but this is not the only approach.

[0012] Although other manufacturing processes are possible for this type of material, pultrusion has been chosen for the production of composite armor. Pultrusion allows for the easy production of very long products with fibers oriented longitudinally to achieve maximum strength in that direction. When only fibers are oriented longitudinally, it is called a unidirectional composite.

[0013] The advantage of unidirectional composites is their very high mechanical strength along the fiber direction, but conversely, their disadvantage is their low transverse strength. Indeed, although primarily stressed in the longitudinal direction, the reinforcements of flexible pipes also undergo forces in the transverse directions (transverse bending, compression within the thickness of the composite profile, and torsion of the composite profile) both during the manufacturing of the flexible pipe in the reinforcement wire stage and subsequently during service.

[0014] The transverse stresses experienced by the reinforcement can result in longitudinal cracks, particularly when the composite profile is pressed onto the flexible hose during loading. This is because transverse loads only affect the polymer resin matrix, which has a low elongation at break. Figures 1a and 1bThese figures respectively illustrate the initial configuration of the unidirectional composite profile and the bonding of the unidirectional composite profile to the flexible pipe during loading. In these figures, reference D2 indicates the bonding direction of the reinforcement wire, and reference D1, a transverse direction. For such a profile, a fracture initiation point (AR) can form during the bonding of the profile to the flexible pipe, particularly at the outer surface of the reinforcement.

[0015] Patent EP 1066485 (equivalent to WO 99 / 49259) proposes a solution to address the risk of transverse cracking by adding a film to at least one face of the composite profile forming the reinforcement. This film, also called mat, is a layer of non-woven fibers that has the advantage of not having a preferred reinforcement direction and a low fiber volume ratio. The mat is added to at least one face of the reinforcement to mechanically strengthen it against the bending and torsional stresses it experiences during the reinforcement stage of flexible pipe manufacturing. Furthermore, the mat improves the reinforcement's resistance to abrasion between profiles. For reasons of improved abrasion resistance and cost, the mats used to date have been made from aramid fibers.

[0016] There are two limitations to the use of mat layers to reinforce unidirectional composites in the transverse directions: Since the fiber content is low and the fibers are randomly oriented, the reinforcement effect of this layer is weak, and it is even weaker as the profile thickness increases, and since aramid fibers are hygroscopic, the environment of the flexible hose ring (presence of water, gas, high temperatures) can lead to a degradation of the properties of this layer in service.

[0017] To overcome these drawbacks, the present invention relates to a composite reinforcement for flexible pipes. The reinforcement comprises a composite profile and a reinforcing tape. The composite profile is formed of longitudinally oriented reinforcing fibers embedded in a polymer resin matrix. The reinforcing tape is formed by a woven tape comprising fibers impregnated in a polymer material, such that the weft yarn of the reinforcing tape is orthogonal to the longitudinal direction of the profile, and the warp yarn of the tape is parallel to the longitudinal direction of the profile.Thus, the reinforcing tape comprising fibers along these directions makes it possible to improve the transverse behavior of the armor and to avoid the initiation of breaks, while guaranteeing mechanical properties (in particular longitudinal resistance and transverse resistance), a size and a mass suitable for the manufacturing and use constraints of a flexible pipe. The device according to the invention

[0018] The invention relates to a flexible conduit reinforcement comprising a composite profile and at least one reinforcing tape, said composite profile being made of continuous reinforcing fibers embedded in a polymer resin, said composite profile having a substantially rectangular cross-section, and said reinforcing tape being bonded to at least one face of said composite profile. Said reinforcing tape is a woven tape comprising fibers impregnated in a polymer material, said reinforcing tape being formed such that the weft yarn of said reinforcing tape is substantially perpendicular to the longitudinal direction of said composite profile, and such that the warp yarn of said reinforcing tape is substantially parallel to the longitudinal direction of said composite profile.

[0019] Advantageously, from 50 to 90%, and preferably from 60 to 80%, of said fibers of said reinforcing tape are included in said warp yarn of said reinforcing tape.

[0020] Advantageously, the fiber volume percentage of said reinforcing tape is greater than 40%, and preferably 60%.

[0021] According to one embodiment, said fibers of said reinforcing tape are carbon fibers.

[0022] According to an implementation, the thickness of said reinforcing tape is between 5 and 50% of the thickness of said armor, preferably between 10 and 30% of the thickness of said armor.

[0023] According to one aspect, said armor includes a reinforcing strip arranged on the upper face of said composite profile.

[0024] According to a characteristic, said armor includes two reinforcing strips arranged on the upper and lower faces of said composite profile.

[0025] According to one embodiment option, said reinforcing tape is attached to said composite profile by sheathing, by gluing, or by simultaneous lamination with said polymer resin of said profile during the manufacture of said composite profile.

[0026] According to an implementation, said armor has a longitudinal stiffness greater than 70% of that of the reference unidirectional armor and preferably greater than 80%.

[0027] Preferably, the fiber volume percentage of said composite profile is between 50 and 80%.

[0028] According to one embodiment, said fibers of said composite profile are oriented only along the longitudinal direction of said composite profile.

[0029] Furthermore, the invention relates to a flexible conduit for transporting a petroleum effluent, said flexible conduit comprising at least one pressure sheath and at least one layer of tensile armor comprising armors according to one of the preceding characteristics, said layer of armor being placed outside said pressure sheath. Brief presentation of the figures

[0030] Other features and advantages of the composite armor according to the invention will become apparent from the following description of non-limiting examples of implementations, with reference to the figures attached and described below. THE Figures 1a and 1b The diagrams already described illustrate, respectively, the initial configuration of the unidirectional composite profile and the plating of the unidirectional composite profile onto a flexible pipe during loading. figure 2 illustrates an armor according to one embodiment of the invention. The figure 3illustrates a flexible driving system including armor according to the invention. Detailed description of the invention

[0031] The present invention relates to a flexible conduit reinforcement, in particular a tensile reinforcement or tensile reinforcement. The reinforcement comprises a composite profile and at least one reinforcing tape. A reinforcement is defined as a flat element whose length is very large compared to its other dimensions: width and thickness. The reinforcement may have a substantially rectangular cross-section. The composite profile is also a flat element whose length is very large compared to its other dimensions. The composite profile may have a substantially rectangular cross-section. According to the invention, the composite profile may be a unidirectional composite profile: the composite profile consists of yarns or strands comprising a set of continuous reinforcing fibers embedded in a polymer resin, the reinforcing fiber strands being oriented solely along the longitudinal direction of the profile.Thanks to the unidirectional composite, the composite profile, and a fortiori the armor, has high mechanical resistance in the direction of the fibers, i.e. in the longitudinal direction of the armor.

[0032] According to the invention, the reinforcing tape is bonded to at least one face of the composite profile. Advantageously, the reinforcing tape can also be a flat element whose length is very large compared to the other dimensions. The reinforcing tape can have a substantially rectangular cross-section. The reinforcing tape is a woven tape comprising continuous fibers assembled into yarns or strands, impregnated in a polymer material. According to the invention, the reinforcing tape is formed such that the weft yarn of the reinforcing tape is substantially perpendicular to the longitudinal direction of the composite profile (in other words, the weft yarn of the reinforcing tape is parallel to the width of the weave), and such that the warp yarn of the reinforcing tape is substantially parallel to the longitudinal direction of the composite profile (in other words, the warp yarn is parallel to the length of the weave).The weft yarn is a yarn in a fabric oriented across the width of the fabric (and therefore the reinforcing tape). Its opposite is the warp yarn, oriented along the length of the fabric (and therefore the reinforcing tape). It is the interlacing of these two yarns that creates a fabric. This design of the reinforcing tape allows for fibers in both the longitudinal and transverse directions, which improves the transverse behavior of the weave and prevents the initiation of breaks, while maintaining high mechanical strength along the longitudinal direction of the weave. The reinforcing tape preferably covers the entire width of the composite profile. Furthermore, the reinforcing tape can extend over virtually the entire length of the composite profile.

[0033] To optimize the transverse strength of the armor, the distribution of fibers in the reinforcing tape can be as follows: 50 to 90%, and preferably 60 to 80%, of the fibers of the reinforcing tape are included in the warp yarn of the reinforcing tape, and 10 to 50%, and preferably 20 to 40%, of the fibers of the reinforcing tape are included in the weft yarn of the reinforcing tape.

[0034] A low fiber distribution value in the warp yarn of the reinforcing tape is more effective in terms of transverse reinforcement of the weave. However, weaving the tape is more difficult and time-consuming, and therefore less economical.

[0035] The thickness of the reinforcing tape can vary up to almost the entire thickness of the armor if the entire armor is reinforced in the transverse direction, but it is preferable to apply the tape to only a portion of the armor thickness. Depending on the embodiment, the thickness of the reinforcing tape can represent from 5% to 50% of the total armor thickness, and preferably, the thickness of the reinforcing tape represents from 10% to 30% of the total armor thickness, in order to optimize the use of unidirectional tape, particularly for longitudinal strength and for armor cost reasons.In another embodiment of the invention, the total thickness of the reinforcing tape is substantially equal to the thickness of the armor and is formed by the superposition of several layers of a thickness less than the total thickness of said tape, such that the sum of the thicknesses of said layers is substantially equal to the thickness of the armor. This superposition of layers can be viewed as a superposition of several thin reinforcing tapes, for example, a few microns thick. For example, the superposition comprises between one and ten layers, preferably between two and five layers.

[0036] According to one feature of the invention, the reinforced weave with a reinforcing tape can have a longitudinal stiffness greater than 70% of that of the reference unidirectional weave, and preferably greater than 80%, to obtain good mechanical properties in the longitudinal direction of the weave. Stiffness is the characteristic that indicates the resistance to elastic deformation of a body. To achieve this, the thickness of the reinforcing tape and the distribution of fibers along the warp direction can be chosen to optimize the mechanical properties in the longitudinal direction of the weave, while significantly reinforcing it in the transverse direction.

[0037] According to one embodiment of the invention, the fiber volume percentage of the reinforcing tape can be greater than 40%, preferably between 55% and 65%, and most preferably approximately 60%. The fiber volume percentage is defined as the ratio of the volume occupied by the fibers to the total volume of the reinforcing tape. Such a fiber volume percentage in the reinforcing tape allows for good mechanical properties and ensures that the reinforcing tape retains its protective and load-transfer functions. In particular, a fiber volume percentage of 60% provides a good compromise between mechanical properties and the protective function of the reinforcing tape.

[0038] According to one embodiment of the invention, the fibers of the reinforcing tape can be glass, aramid, carbon, high-modulus polyethylene, etc. For example, glass fiber isolates the carbon and prevents bonding with the steel, thus preventing galvanic corrosion. Aramid fiber also provides electrical insulation and gives the reinforcement high tribological properties. Preferably, the fibers of the reinforcing tape can be carbon fibers for reasons of chemical inertness, particularly in applications for flexible pipes, for their good specific mechanical properties (relative to their density), and for economic reasons. Furthermore, carbon fibers avoid the degradation problems that can occur with aramid fibers, especially hygrothermal degradation.

[0039] Preferably, the strands (or yarns) formed by assembling fibers and reinforcing tape have different diameters. The strand diameter depends on the number of fibers it contains. Typically, a strand comprises several thousand fibers, this number of fibers being symbolized by the number K. For example, a strand composed of 12,000 fibers is called "12K".

[0040] In the present invention, the diameter of the rovings can, for example, vary between 1K and 48K, preferably between 3K and 12K. Thus, the different pairs of "warp yarns / weft yarns" (or "weft yarns / warp yarns") that can be considered for the production of the reinforcing tape are, for example, of the type "3K / 3K", "3K / 6K", "3K / 12K", "6K / 6K", "6K / 12K" and "12K / 12K".

[0041] Advantageously, a weft yarn with a maximum diameter of 6K is chosen to facilitate the weaving of the reinforcing tape.

[0042] The polymer material of the reinforcing tape, in which the fibers are impregnated, can be chosen from a thermoplastic or thermosetting polymer. In one embodiment, the polymer material can be a thermosetting resin such as an epoxy, vinyl ester, or cyanate resin, or a thermoplastic resin such as a polyolefin, polyamide, fluoropolymer, polyaryletherketone (PAEK), or polyphenylene sulfide (PPS). Preferably, the polymer material chosen for the reinforcing tape can be the same as that of the polymer resin of the unidirectional composite profile, which improves the overall cohesion. Advantageously, in an embodiment of a reinforcing tape formed by the superposition of several layers, the same polymer material is chosen for each layer to improve cohesion between them.

[0043] The composite profile can be made of continuous reinforcing fibers selected from carbon, glass, aramid fibers, embedded in a polymer resin, in particular thermosetting or thermoplastic, especially an epoxy, vinyl ester, cyanate resin, etc. or a thermoplastic type resin such as a polyolefin, a polyamide, a fluorinated polymer, a polyaryletherketone (PAEK), a polyphenylene sulfide (PPS), etc.

[0044] The fiber content in the composite profile can range from 50% to 80%. This fiber content in the composite profile allows it to meet the constraints imposed by flexible pipes, particularly in terms of longitudinal strength.

[0045] According to one embodiment of the invention, the tensile reinforcement comprises two reinforcing strips bonded to the upper and lower faces of the composite profile. This forms a three-layer reinforcement, which ensures symmetry and requires no special precautions during installation to ensure correct orientation.

[0046] When the armor consists of a single reinforcing strip (two-layer armor), the reinforcing strip is bonded to the upper face of the composite profile. This construction with a single reinforcing strip allows for a simplified construction of the armor and makes it possible to reinforce only the face of the composite profile that is likely to show signs of incipient failure (see below). figure 1b ).

[0047] According to one embodiment of the invention, a reinforcing strip can be attached to at least one lateral face (or both lateral faces) of the composite profile. This structure provides mechanical protection to the composite profile against wear that can occur between the different composite profiles forming the tensile reinforcement layer.

[0048] According to one embodiment of the invention, the reinforcing tape is bonded to the composite profile by sheathing, gluing, or simultaneous lamination with the polymer resin of the composite profile during the manufacturing of the composite profile. Preferably, the bonding between the reinforcing tape and the composite profile is achieved by simultaneous lamination of the different consecutive layers in order to optimize the cohesion of the different layers.

[0049] Advantageously, in the embodiment of the invention in which the reinforcing tape is formed by the superposition of several layers, the implementation of the tape is also carried out by simultaneous layering.

[0050] There figure 2 illustrates, schematically and without limitation, a traction tack according to one embodiment of the invention. figure 2This is a partial, three-dimensional view (since the entire length of the armor is not shown) of an armor 1. The armor 1 has a substantially rectangular cross-section. The armor 1 comprises a composite profile 2 and a reinforcing tape 5. The composite profile 2 and the reinforcing tape 5 have substantially rectangular cross-sections. The composite profile 2 is a unidirectional composite profile, whose fibers 4 are oriented only longitudinally, that is, along the longitudinal direction L of the armor 1. The fibers 4 are embedded in a polymer resin 3. The reinforcing tape 5 is bonded to the upper surface of the composite profile 2. The reinforcing tape 5 comprises fibers impregnated in a polymer material.The reinforcing tape 2 is formed such that the weft yarn of the reinforcing tape 5 is substantially perpendicular to the longitudinal direction L of the composite profile 2, and such that the warp yarn of the reinforcing tape 5 is parallel to the longitudinal direction of the composite profile 2. The reinforcing tape 5 covers the entire length and width of the composite profile 2.

[0051] Other alternative embodiments may be envisaged. For example, the armor 1 may include a second reinforcing strip 5 attached to the underside of the composite profile 2.

[0052] A flexible approach according to prior art is represented, schematically and without limitation, by the figure 3This conduit consists of several layers, described below from the inside out. The flexible conduit is unbonded and meets the specifications defined in the API 17J standard.

[0053] The internal casing 6 consists of a short-pitch helical metal strip. It is designed to resist crushing under the effect of external pressure applied to the pipe.

[0054] The internal sealing sleeve 7 is made by extruding a polymer material, generally chosen from polyolefins, polyamides and fluorinated polymers.

[0055] The pressure arch 8 made of stapled or interlocking metal wires ensures resistance to internal pressure in the pipe.

[0056] According to the illustration of the figure 3The tensile armor layers 9 are made up of wires (armor) wound helically at angles whose absolute value with respect to the longitudinal axis of the flexible pipe is between 20 degrees and 55 degrees. The pipe advantageously comprises two superimposed and crossed layers of tensile armor 9, as shown in the figure 3 For example, if the inner layer of tensile armor is wound with a helix angle of 30 degrees, the outer layer of tensile armor is wound with a helix angle of -30 degrees. This angular symmetry helps to balance the pipe's torsion, reducing its tendency to rotate under tensile stress.

[0057] When the two overlapping and crossed layers of tensile armor 9 are wound with a helix angle substantially equal to 55 degrees, the pressure arch 3 can optionally be omitted as the helix angle of 55 degrees gives the layers of tensile armor 4 good resistance to internal pressure.

[0058] The external sealing sheath 10, also made by extruding a polymer material, forms an external protection for the pipe.

[0059] The conduct represented by the figure 3 is of the "rough bore" type, meaning that the fluid circulating in the pipe is in contact with the internal casing 6.

[0060] Alternatively, the driving style can be of the "smooth bore" type. In this case, the driving style represented by the figure 3It does not have an internal casing 6. The polymer sheath 7 is in direct contact with the fluid circulating in the pipe. The polymer sheath 10 is watertight. External pressure forces are supported by the arch 8.

[0061] The invention further relates to a flexible conduit comprising at least one pressure sheath and at least one mechanical reinforcement element. In this application, the term "mechanical reinforcement element" refers to all the layers of reinforcement used to resist the longitudinal stresses of the flexible conduit. According to the invention, the flexible conduit comprises at least one layer of reinforcement including composite reinforcements as described above. Furthermore, the flexible conduit according to the invention may advantageously include at least one of the other layers of the flexible conduit described with reference to the figure 3including an inner casing, an outer sealing sheath, a pressure vault and / or other additional layers. Preferably, the flexible hose according to the invention is of the unbonded type and meets the specifications defined in the normative document API 17J.

[0062] The use of composite armor according to the invention makes it possible to reduce the weight of the flexible conduit compared to metallic armor. Furthermore, the longitudinal and transverse strength of the composite armor according to the invention prevents breakage and degradation of the armor during use.

[0063] The present invention is adapted for flexible riser-type pipelines, for flexible flowline-type pipelines, and for flexible oil offloading line (OOL)-type pipelines that allow the unloading of petroleum fluids between a floating production, storage, and offloading (FPSO) unit and an offloading buoy.

[0064] The invention is particularly suited to a flexible conduit for great depths, for which the tension at the head of the conduit is the most severe load for the dimensioning of the armor. Application example

[0065] The characteristics and advantages of the armor according to the invention will become clearer upon reading the application example below.

[0066] The primary application of the invention is a flexible pipeline reinforcement for transporting petroleum effluent. This flexible pipeline can traverse a water column, connecting subsurface installations (wells) and a surface platform (such a flexible pipeline is called a "riser"). In deep water, this pipeline is subjected to significant mechanical stresses due to its weight and the movements of the platform, which is always afloat. Reducing the weight of this pipeline not only lowers the stresses applied to it but also reduces the suspended weight that the platform must support. There are cases where the dimensions of the flexible pipeline and the water depth are such that only a composite-reinforced flexible pipeline is feasible, for example, the "top riser" (i.e., the upper portion of the flexible pipeline).For this example, it is a flexible pipe with an internal diameter of 9" (approximately 228.6 mm) sized for an internal operating pressure of 553 bars (approximately 55.3 MPa) and a water section of 2,140 m.

[0067] The critical loads that the top riser must withstand correspond to the top load (connection to the platform) and the bottom load (connection to the bottom riser, i.e., the lower portion of the flexible pipe). The top load combines the internal pressure (production line), the tension due to the suspended weight, and the bending due to platform movement, the latter two not being constant. The bottom load combines the external pressure (depressurized line) and the tension due to the weight of the bottom riser; the sum of these two forces the reinforcements into compression due to the inverse bottom effect.

[0068] The prior art solution for this case is a flexible hose with four layers of unidirectional composite reinforcement with a cross-section of 14 x 1.65 mm, and a fiber volume fraction (Vf) of 68%. Two new reinforcement structures according to the invention are proposed here (cross-section 14 x 2.08 mm, Vf = 60% for the reinforcing tape and the composite profile): Example 1 (not in accordance with the invention): a reinforcing tape, with a fiber distribution in the warp yarn k = 0.89 (89%), Example 2 (in accordance with the invention): a three-layer composed successively of a first reinforcing tape with k = 0.7, a composite profile, and a second reinforcing tape with k = 0.7, the respective thicknesses of the three layers being 0.39, 1.30, and 0.39 mm, Example 3 (in accordance with the invention): a two-layer composed successively of a composite profile, and a reinforcing tape with k = 0.7, the respective thicknesses being 1.30 and 0.78 mm, and the reinforcing tape being placed on the outer surface of the composite profile.

[0069] These solutions were designed to provide the same axial stiffness to the flexible pipe. For each solution, the stresses and the R-value of the reinforcement are calculated for the top and bottom loads of the flexible pipe, using a numerical model that fully accounts for the multiaxial nature of the loads.

[0070] The maximum value of the failure factor R is given for the different solutions in Table 1. The wire is considered broken for R ≥ 1. The factor R is calculated from the stress state and the breaking limits in each direction of the wire. Table 1 - Maximum breaking strength factor for different armor structures Armor R max Previous art: unidirectional armor with Vf = 68% 1.33 Example 1 1.13 Example 2 0.86 Example 3 0.80

[0071] Reducing the fiber content significantly lowers the Rmax value compared to the previous art armor example, but it remains close to 1. However, using a three-layer, and especially a two-layer, allows the Rmax value to be reduced even further, falling below 0.9, and consequently preventing armor failure.

[0072] Thus, reinforcing the existing unidirectional composite profile with woven tapes or, more generally, fabrics, improves the transverse strength of the reinforcement while maintaining satisfactory longitudinal properties. In particular, it is possible to sufficiently reinforce the reinforcement to prevent longitudinal cracking.

Claims

1. Flexible pipe for transporting a petroleum effluent, said flexible pipe including at least one pressure sheath (7) and at least one tensile armour ply (9) comprising armours (1), said armour ply (9) being placed outside said pressure sheath (7), the armours including a composite profile (2) and at least one reinforcing strip (5), said composite profile (2) being made of continuous reinforcing fibres (4) embedded in a polymer resin (3), said composite profile (2) having a substantially rectangular cross section, and said reinforcing strip (5) being secured to at least one face of said composite profile (2), characterized in that said reinforcing strip (5) is a woven strip comprising fibres impregnated in a polymer material, said reinforcing strip (5) being formed such that the weft thread of said reinforcing strip (5) is substantially perpendicular to the longitudinal direction (L) of said composite profile (2), and such that the warp thread of said reinforcing strip (5) is substantially parallel to the longitudinal direction (L) of said composite profile (2).

2. Flexible pipe according to Claim 1, wherein 50% to 90%, and preferably 60% to 80%, of said fibres of said reinforcing strip (5) are included in said warp thread of said reinforcing strip (5).

3. Flexible pipe according to either of the preceding claims, wherein the fibre volume ratio of said reinforcing strip (5) is greater than 40%, and is preferably 60%.

4. Flexible pipe according to one of the preceding claims, wherein said fibres of said reinforcing strip (5) are carbon fibres.

5. Flexible pipe according to one of the preceding claims, wherein the thickness of said reinforcing strip (5) is between 5% and 50% of the thickness of said armour (1), preferably between 10% and 30% of the thickness of said armour (1).

6. Flexible pipe according to one of the preceding claims, wherein said armour (1) comprises a reinforcing strip (5) arranged on the upper face of said composite profile (2).

7. Flexible pipe according to one of the preceding claims, wherein said armour (1) comprises two reinforcing strips (5) arranged on the upper and lower faces of said composite profile (2).

8. Flexible pipe according to one of the preceding claims, wherein said reinforcing strip (5) is secured to said composite profile (2) by sheathing, by bonding or by simultaneous lamination with said polymer resin of said profile during the manufacture of said composite profile (2).

9. Flexible pipe according to one of the preceding claims, wherein said armour (1) has a longitudinal stiffness greater than 70% of the longitudinal stiffness of the reference unidirectional armour, and preferably greater than 80%.

10. Flexible pipe according to one of the preceding claims, wherein the fibre volume ratio of said composite profile (2) is between 50% and 80%.

11. Flexible pipe according to one of the preceding claims, wherein said fibres (4) of said composite profile (2) are oriented only in the longitudinal direction (L) of said composite profile (2).