WO2024175995A1

WO2024175995A1 - Subsea umbilical composite tube and method of manufacture

Info

Publication number: WO2024175995A1
Application number: PCT/IB2024/000066
Authority: WO
Inventors: Mariana SOCARICEANU; Alan Rutherford; Anh-Tuan DO; Thomas EPSZTEIN; Dragos NISTOR; Lee Smith
Original assignee: Technipfmc Subsea France
Priority date: 2023-02-20
Filing date: 2024-02-20
Publication date: 2024-08-29
Also published as: GB2627442A; GB202302391D0

Abstract

The present invention relates to a subsea umbilical composite tube for use in subsea umbilical system such as the transportation of fluids such as hydraulic, chemical injection fluids and gas, and a method of manufacture thereof. In particular, a subsea umbilical composite tube comprising at least a thermoplastic liner, a composite reinforcement layer, and a thermoplastic cover.

Description

SUBSEA UMBILICAL COMPOSITE TUBE AND METHOD OF MANUFACTURE

The present invention relates to a subsea umbilical composite tube for use in a subsea umbilical and cable systems, such as the transportation of fluids such as hydraulic, chemical injection fluids and gas, as well as in other energy industries. The present invention also relates to a method of manufacture thereof, and apparatus therefor, and a subsea umbilical comprising such a composite tube.

Background

As industry moves towards climate reduction targets and the focus sharpens on green energy production and other gas transportations and/or storage under a low cost format, there is an increasing need for a new alternative umbilical fluid conduit made of composite materials. Composite tubes are becoming an alternative to conventional fluid conduit such as steel tubes or hoses.

There are currently two technologies used for fluid conduits; super duplex stainless steel tube and thermoplastic hoses.

(i) Super Duplex Stainless Steel (SDSS) umbilical tube exhibits several disadvantages such as: weight, corrosion risk (including AC corrosion), restricted fatigue life, limited accumulated plastic strain (limitation from bending stiffness characteristics, maximum degree of strain which an un-pressurised tube can sustain in a single operation is 2.5%, up to reaching a maximum of 20% accumulated plastic strain (APS), high cost and long lead time for delivery.

(ii) Thermoplastic hoses have some weaknesses also such as low collapse resistance, delay in response time, no strength (armour wire and strength members required to withstand the load) but are typically 20% cheaper than steel tube and in general, are manufactured in half of the lead time compared with steel tube. Hoses are typically constructed of high strength fibres such as aramid, dacron, or nylon, laid down in a geodesic pattern onto a substrate plastic liner tubular structure, or mixed with a low modulus binder such as rubber, to carry pressure loads and to exhibit good bending flexibility, but a hose has very limited ability to carry compressive, tension and torsion loads or external pressure. The use of composite tubes is still being considered, and hitherto any use in the oil and gas industry is only designed for large diameter tubes generally being >38mm, and small bore composite tubes are not yet used in umbilical application. There is no composite tube in small bore diameter for use as a fluid conduits in an umbilical system able to undertake or deal with the issues of small bends, working under various pressure ranges, and at elevated temperatures, that occur in the oil and gas industry.

One object of the present invention is to minimise or overcome these problems.

Summary

According to one aspect of the present invention, there is provided subsea umbilical composite tube comprising at least a thermoplastic liner, a composite reinforcement layer, and a thermoplastic cover.

According to another aspect of the present invention, there is provided a method of manufacturing a subsea umbilical composite tube comprising at least the steps of: providing a thermoplastic liner; adding a composite reinforcement layer over the thermoplastic liner; and adding a thermoplastic cover over the composite reinforcement layer to form a subsea umbilical composite tube.

According to another aspect of the present invention, there is provided apparatus for manufacturing a subsea umbilical composite tube comprising at least a thermoplastic liner, a composite reinforcement layer comprising a plurality of fibres and a thermoplastic or thermoset matrix, and a thermoplastic cover, the apparatus comprising a plurality of bobbins arranged to be rotatable in relation to the thermoplastic liner, and able to wind or to braid, or both wind and braid, continuously, the fibres around the thermoplastic liner.

According to another aspect of the present invention, there is provided a subsea umbilical comprising at least one subsea umbilical composite tube as defined herein, i.e. comprising at least a thermoplastic liner, a composite reinforcement layer, and a thermoplastic cover, and intended for use in the transportation of a fluid such as oil, gas, CO2, hydrogen gas, hydrogen sulfide,

Description of the drawings

The present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:-

Figure 1a is a perspective view of a cross-section of a subsea flexible composite tube according to one embodiment of the present invention:

Figure 1b is a part-open view of a section of the subsea flexible composite tube of Figure 1a;

Figures 1c and 1d are similar perspective and part-open views of a subsea flexible composite tube according to a first particular embodiment of the present invention;

Figures 1e and 1f are similar perspective and part-open views of a subsea flexible composite tube according to a second particular embodiment of the present invention;

Figure 2a is a perspective view of a cross-section of a subsea flexible composite tube according to another embodiment of the present invention:

Figure 2b is a part-open view of a section of the subsea flexible composite tube of Figure 2a;

Figure 3a is a perspective view of a cross-section of a subsea flexible composite tube according to another embodiment of the present invention;

Figure 3b is a part-open view of a section of the subsea flexible composite tube of Figure 3a;

Figure 4a is a perspective view of a cross-section of a subsea flexible composite tube according to another embodiment of the present invention;

Figure 4b is a part-open view of a section of the subsea flexible composite tube of Figure 4a;

Figure 5 is a flow diagram of a selection process for pull forming useable as part of a method of manufacture according to another embodiment of the present invention;

Figures 6a and 6b are schematic and perspective views of a method of manufacture according to another embodiment of the present invention; and Figure 7 is a cross-section of a subsea flexible composite tube umbilical according to an example of the present invention.

Detailed description of the invention

As described above, a problem with the use of composite tubes is that they are still being explored for use in many industries, in particular in the field of the oil and gas industry but also in new energy markets such as Carbon Capture, Utilization and/or Storage (CCUS), hydrogen sulfide transportation, or hydrogen transportation, or storage thereof. Subsea composite tubes need to achieve the same standards as existing steel tubes and thermoplastic hoses, as any accidental performance issues can lead to catastrophic results.

The uses include those being fully subsea, and those also being partly above sea, such as to a ‘topside’ facility or connection.

In particular, it is desired to provide small-bore thermoplastic composite tubing that can be manufactured in a continuous and seamless manner in a low cost format.

According to one aspect of the present invention, there is provided a subsea umbilical composite tube comprising at least a thermoplastic liner, a composite reinforcement layer, and a thermoplastic cover.

The composite tube is subsea for the use wholly or substantially or partly under water, particularly in many parts of various subsea industries, including the oil and gas industries, and for new energy markets such as Carbon Capture, Utilization and/or Storage (CCUS), hydrogen sulfide transportation, or hydrogen transportation, or storage thereof.

Thus, the present invention extends to a subsea umbilical composite tube as defined herein for use in the transportation of a fluid in any of the oil, gas, CO2, hydrogen gas, hydrogen sulfide, carbon capture, industries, for example for the transportation of a hydrocarbon oil, a hydrocarbon gas, CO2, hydrogen, or hydrogen sulfide. The subsea umbilical composite tube may be used as such, or may be part of a larger pipeline or umbilical or bundle. Thus, the present invention extends to a subsea umbilical comprising at least one subsea umbilical composite tube as defined herein.

For example, the subsea umbilical composite tube may be used in a submarine line that is for example a flexible pipe, in particular built according to the standards API 17J (Specification for Unbonded Flexible Pipe, 4th edition - May 2014) and API RP 17B (Recommended Practice for Flexible Pipe, 5th edition - May 2014) established by the American Petroleum Institute. As used herein, the term “flexible pipe” may also refer to an Integrated Production Bundle (IPB) product. The IPB is a flexible production riser that features thermal insulation layers, additional hoses/tubes for gas lift or other services, active heating through electric cables, and fluid temperature monitoring with optical fibres.

Alternatively and preferably, the subsea umbilical composite tube is part of a subsea umbilical as defined in ISO 13628- 5 “Petroleum and natural gas industries — Design and operation of subsea production systems — Part 5: Subsea umbilicals” published in December 2009 by the International Organization for Standardization, API 17E “Specification for Subsea Umbilicals”, 5th Edition - July 2017 and API RP 17A “Design and Operation of Subsea Production Systems - General Requirements and Recommendations”, 6th Edition - May 2022, established by the American Petroleum Institute, and IEC60183:2015, January 2015, IEC60840:2020, May 2020 and/or IEC63026:2019, December 2019, established by the International Electrotechnical Commission (IEC).

A subsea umbilical for use in the offshore production of hydrocarbons generally comprises a group of one or more types of elongated active umbilical components as a bundle arrangement, such as electrical cables, optical fibre cables, hydraulic and/or injection fluids lines like SDSS tubes and/or thermoplastic hoses for fluid transport, strength and/or weight members like rod or rope made of steel or carbon fibres and, fillers; the umbilical is over-sheathed and, when applicable, armoured for mechanical strength. Umbilicals are typically used for transmitting power, signals, hydrocarbons, and/or working fluids (for example for fluid injection, hydraulic power, gas release, etc.) to and from a subsea installation. The subsea umbilical cross-section is generally circular, the elongated elements being wound together either in a helical or in a S/Z pattern. In order to fill the interstitial voids between the various umbilical elements and to obtain the desired configuration, filler components may be included within the voids.

The subsea umbilical is designed to operate in static (seabed) and/or dynamic (hang off catenary for Floating Production Storage and Offloading vessels or platforms) conditions. Both service conditions experience high tensile load during installation, but once a static umbilical has been laid in the seabed, it is exposed only to internal and external pressure and will not be subjected to continuous cyclic motions. Meanwhile, dynamic umbilicals are subjected to high tensile loading and fatigue mechanisms due to the motion of the vessel or the platform. Therefore, dynamic and fatigue analysis are carried out to evaluate fatigue performance of the product and evaluate its life span when use in dynamic application.

Subsea umbilicals are now being installed at increasingly deeper water depths, commonly being deeper than 2000 m. Such umbilicals therefore have to be able to withstand the increasingly severe loading conditions during their installation and their service life. To overcome the problem of harsh operational conditions, it is known to use conventional hydraulic conduits such as SDSS tubes or thermoplastic hoses. The current umbilical design of the Applicant is based on two technologies for fluid conduits namely the Super Duplex Stainless Stell tubes and the thermoplastic hoses, but these products exhibit some drawbacks mentioned hereabove.

As used herein “subsea umbilical” may also include, for example, a steel/thermoplastic tube electrohydraulic umbilical, Integrated Service/Production Umbilical (ISU™ I IPU™) and subsea power umbilical/cable. An Integrated Service Umbilical is an umbilical that integrates tubes/hoses (1 inch - 4 inches range; i.e. 25,4mm to 101 ,6mm) for fluid service, e.g. bulk methanol, or gas lift, placed around the central core.

The present invention will allow the manufacturing of composite umbilical tubes in small bore sizes but not limited to (smaller more changeable, bigger diameter much easier to produce), spoolable under a low-cost format for use in the subsea umbilical.

One of the advantages of using composite tube within the umbilical structure will be that the overall umbilical will be three to four times lighter than a conventional steel tube umbilical, which will benefit the umbilical bundle installation in terms of installation tension (top side tension will be minimized) on the installation fleet from which the umbilical will be installed. The use of metallic tubes obviously increases the overall weight of the subsea umbilical, especially during laying at increasingly deeper water depths. As the weight of the umbilical increases, more of the total stress capacity of the umbilical must be devoted to tensioning stresses during laying, so that less of the total stress capacity is available for any bending stresses. Heavier umbilicals require more robust handling equipment, such as winches, spools, clamps, tensioners, etc.

Another important advantage of using composite tube within the umbilical structure is flexibility and improved fatigue. Any increase in the use of metallic tubes or tubing also decreases the flexibility of the umbilical, whilst the umbilical should still have sufficient flexibility to be ‘reelable’ or ‘spoolable’ with conventional equipment, etc. Reeling is the most convenient form of pipeline transportation and laying, generally from a reel in the reel-laying method known in the art. As explained above the conventional SDSS steel tube exhibits limitation from bending stiffness characteristics, maximum degree of strain which an un-pressurised tube can sustain in a single operation is 2.5% and can reach a maxim of 20% accumulated plastic strain (APS) before it is going to permanent plastic deformations impacting the product life cycle. Unfortunately, the repeated spooling and use of steel tubing causes fatigue damage that can suddenly cause the steel coiled tubing to fracture and fail. The repeated bending of steel coiled tubing into and out of plastic deformation induces irreparable damage to the steel tube body leading to low-cycle fatigue failure.

In addition, the new fluid conduit made of composite materials provides improved mechanical properties such as flexibility, pressure retention, resistance to impact, wear with excellent corrosion resistance, long service life under a reduction in weight and cost. The composite tubes are lightweight and exhibits improved fatigue resistance compared with steel tubes, allowing the composite tube to be spooled and un-spooled from a reel or a carousel multiple times without limiting the lifespan of product as could happen on a conventional super duplex stainless-steel tube (no APS limits which is a very important factor for using composites instead of steel material). Furthermore, the light weight given by a composite tube reduces the overall weight of the umbilical, improving the manoeuvre, transportation and the installation of the full product which will reduce cost and also the CO2 footprint. The composite tube offers the potential to exceed the performance limitations of steel tube, thereby increasing the service life of the tube and extending operational parameters. Also, the new product will eliminate the AC corrosion risk which currently steel tube is susceptible. The composite tube will be able to sustain its own load therefore, no additional strength members or load bearing ropes will be required element of the umbilical construction. The overall product will be made in a cheaper format (up to 20% cheaper than SDSS tube) depending upon materials and application under improved lead time (25-50% time delivery improvement).

The present invention provides a composite tube which is capable to be bundled into an umbilical structure along with other umbilical constituents such as (hoses, steel tubes, cables, strength members, optical fibres) capable of repeated spooling and bending which does not suffer from the limitations of steel tubing and is highly resistant to chemicals.

The use of composite umbilical tube allows the individual composite tube element and also the overall umbilical to be spooled and unspooled multiple time without exhibiting any plastic deformation.

In further addition, there is an increased material cost for using super duplex stainless-steel material for conventional steel tube, the price of allowing elements (Ni, Cr, Mo) increased substantially over the past. The composite tube material selection and fabrication process is driven by a cost and lead time reduction while overcoming steel tube and hoses technical challenges.

The other type of conventional umbilical uses conventional hydraulic hoses. The hose generally consists of a plastic liner reinforced externally by a wrapping of aramid fibres, and an outer wrapping of plastic. However, this arrangement is less secure against aggressive or corrosive fluids, deep water depths, high pressure and elevated temperature and leading to some limited application, despite being of less weight than the use of metallic tubes. Hoses have low collapse resistance, delay in response time, no strength, therefore will need armour wires or strength members to take the load from the hoses.

Overall the composite tube yields a lighter umbilical that is easier to handle than a comparable conventional umbilical incorporating only steel tubes with advanced and enhanced hydrostatic pressures and mechanical properties such as dynamic loading and fatigue. All these key advantages make the composite tubing particularly suited for use in the Oil and Gas industry as part of an umbilical construction to transport fluids or perform other operations traditionally carried out with steel tubing or hoses.

The subsea composite tube can withstand internal pressures in ranges >5,000psi (> 3.4 x 10⁷ Pa), working pressure up to 10000psi (6.89 x 10⁷ Pa), and burst at more than 30000psi (2.07 x 10⁸ Pa). The subsea composite tube can operate in ultra-deep waters (2000m WD) and is able to sustain collapse resistance of 300bar - 350bar (3 x 10⁷ Pa - 3.5 x 10⁷ Pa).

Optionally, the subsea composite tube is flexible, so as to provide a tube which can be spooled or reeled on to a suitable drum, reel or carousel to assist storage and/or transportation and/or laying for use in the subsea umbilical application. Forming a flexible tube assists spooling and unspooling the composite tube from a reel, significantly improving and increasing quality and speed of transportation and laying, particularly in long lengths in as subsea environment.

The subsea composite tube of the present invention exhibits distinctive characteristics such as improving burst and collapse pressure, improved load sharing capacity, while still being able to be reeled or spooled on to a suitable drum, reel or carousel. The manufacturing costs are also less than a conventional subsea steel tube.

The thermoplastic liner of the composite tube may be a thermoplastic liner known in the art, and may have a particular function or functions, in particular to provide a conduit for a fluid such as oil or gas, which can be corrosive. In one embodiment of the present invention, the thermoplastic liner is a subsea flexible composite tube wherein the thermoplastic liner is one or more of the group comprising: Nylon 11 , Nylon 12, PE such as high density polyethylene (HDPE); medium density polyethylene (MDPE), cross-linked polyethylene (XPLE) and polyethylene raised temperature I bimodal polyethylene (PERT).

The thermoplastic liner may be formed in a manner known in the art to provide a continuous and seamless tube, and may have a thickness in the range 1.0mm to 5.0mm, such as 1 mm, 1.25mm, 2mm, 3mm, 4mm and 5mm. The thermoplastic liner may have a thickness in the range of 1.25mm to 5.0mm. The thermoplastic liner may have a thickness in the range of 1 .25 to 2.0mm.

The composite reinforcement layer of the composite tube of the present invention provides the functions of strength and stiffness for the composite tube, as well as withstanding the pressures that may be exerted on the thermoplastic liner during passage of fluids through the composite tube. In this way, the composite reinforcement layer provides or achieves the advantages of using conventional or traditional steel tubes or thermoplastic hose lines, whilst still withstanding the harsh loads and environments typical in subsea use, locations and industries, including the loads under static and dynamic applications. The composite reinforcement layer may have a thickness in the range of 1.0 to 8.0mm. The composite reinforcement layer may have a thickness in the range of 1 ,5mm to 4.5mm.

The composite reinforcement layer of the composite tube of the present invention also provides improved mechanical properties over conventional tubes, such as improved flexibility and pressure retention, along with corrosion resistance and long service life. Other benefits of the present invention include: providing a composite tube capable of carrying corrosive fluids, even at high temperatures, without causing corrosion in the composite tube; providing a coiled tube having less weight than a steel tube; and providing a coiled tube capable of withstanding higher internal pressure levels and higher external pressure levels (i.e. collapse resistance) without losing tube integrity. Improved flexibility allows the composite tube of the present invention to be more easily spooled and unspooled from a reel or a drum or a carousel. The flexibility allows the composite tube to be spooled and unspooled multiple times, without limiting the lifespan of the product, in contrast to a conventional steel tube that would not allow multiple bending and unbending without product stresses and thus possible failure. Thus, the composite reinforcement layer of the composite tube of the present invention can be laid, re-laid or re-used multiple times, so that the composite tube can have a substantial longer service life than that of conventional steel tube. Furthermore, the flexibility of the composite tube of the present invention improves its manoeuvrability, its transportation, and its quality and quickness of installation (being laid), which further reduces high cost of laying.

The composite reinforcement layer of the composite tube of the present invention also provides a reduction in the weight and cost of the overall composite tube compared with conventional tubes. As such, the composite tube of the present invention can also better sustain its own weight or load, being lighter than traditional steel umbilical tubes. This reduces or even avoids the need for additional strength members or load bearing ropes to be required as part of the load bearing requirements of larger or longer subsea umbilical constructions.

In particular, the subsea composite tube of the present invention is lighter than a comparative Super Duplex Stainless Steel (SDSS) umbilical tube providing the same functionality. A lighter tube improves many aspects of installation, including speed, as well as requiring less support in use. For example, a subsea composite tube of the present invention can be a free hanging catenary umbilical between topside and seabed locations.

The composite tube of the present invention can be recognised as having the advantages of being comparatively lightweight compared to known steel umbilical tubes and thermoplastic hoses, whilst exerting improved fatigue resistance, and also being able to be spooled and unspooled multiple times, within the product lifespan. As the composite tube of the present invention can exceed the performance limitations of known steel umbilical tubes, the composite tube increases the service life of the composite tube in use, and extends its operational parameters. For example, as the composite tube is capable of withstanding higher external pressure levels (i.e. collapse resistance) without losing tube integrity, it can be used as deeper water depths than conventional steel umbilical tubes.

The composite tube of the present invention will also avoid the AC or microbial corrosion risk which conventional steel tubes are susceptible to. In addition, the fibres, the matrix, and the liner used in the composite tube can make the tube impervious to corrosion and resistant to chemicals used in subsea umbilical application.

The composite reinforcement layer of the composite tube of the present invention may be one or more of the group comprising glass fibres or carbon fibres, embedded in a thermoplastic or thermoset matrix. Glass fibres, carbon fibres or both, provide a combination of improved tensile strength and low weight, and can be used to reinforce thermoplastic or thermoset matrices in a manner known in the art.

Optionally, the carbon fibres (CF) or the glass fibres (GF) could be unidirectional and/or continuous in the matrix.

The carbon fibres (CF) or the glass fibres (GF) have a length longer than 100m, and optionally longer than 1000m.

Fibres in the composite reinforcement layer are preferably positioned to withstand internal and external pressures, and to provide low bending stiffness. Such fibres could also be either braided or wound in different orientations, via continuous pulforming manufacturing process (as example pulwinding or pulbraiding).

Such fibres and their orientation could also be selected to provide or improve the desired mechanical characteristics for the composite reinforcement layer and for the subsea umbilical composite tube.

In one embodiment of the present invention, the composite reinforcement layer comprises fibres oriented at an angle between 45° to 70° relative to the length or a longitudinal axis or horizontal line of the tube, preferably at an angle in the range 52° to 58°, and more preferably 55°. All angles listed herein can be +/-. Where the composite reinforcement layer comprises more than one layer, each such layer may have fibres at the same or a different angle.

In one embodiment of the present invention, the composite reinforcement layer comprises a fibre volume fraction of 30-70%, preferably a fibre volume fraction of 40- 60%, such 50% fibre volume of fibres, embedded in a thermoplastic or thermoset matrix.

The present invention is not limited by the nature of the thermoplastic matrix or the thermoset matrix.

In one embodiment of the present invention, the thermoplastic matrix is one or more of the group comprising: Nylon (PA) or Polyethylene (PE).

In one embodiment, the composite reinforcement layer is carbon fibres embedded in a thermoplastic matrix, wherein the thermoplastic matrix is Nylon (PA). In another embodiment, the composite reinforcement layer is carbon fibres embedded in a thermoplastic matrix, wherein the thermoplastic matrix is Polyethylene (PE).

In another embodiment of the present invention, the thermoset matrix is one or more of the group comprising: vinyl ester and epoxy.

In one embodiment of the present invention, the subsea umbilical flexible composite tube of the present invention has a composite reinforcement layer comprising carbon fibres embedded in a Polyethylene (PE) matrix. Such a composite layer may comprise individual carbon fibres, or commingled yarns or unidirectional tapes. Commingled yarns are hybrid structures in which two different materials in the form of fibers are mixed to form continuous-filament yarns. Commingled yarns of reinforcing and thermoplastic fibres can achieve lower-cost manufacturing of complex-shaped composite parts, due to reduced impregnation times and applied pressures during processing.

The selection of composite materials will be part of the design selection made by the designer and manufacturer, taking into account various design parameters such as the composite tube dimensions, the location of the composite tube in use, the fluid to be transported by the composite tube, the expected external conditions of the composite tube (including static and dynamic application), any other environment concerns, and the expected cost. The composite tube designing and the method of manufacturing can be based on many factors known to the person skilled in the art, and not further described herein.

The skilled person is also aware of many feed stocks that could be used to form the composite tube of the present invention, their relative costs, as well as various manufacturing processes. The following list provides a number of examples, without limitation, of manufacturing feed stocks and manufacturing process combinations that could be used to form the composite reinforcement layer of the composite tube of the present invention.

Optionally, the composite reinforcement layer of the subsea umbilical composite tube comprises a series of combined composite layers. Optionally, two or more of a series of combined composite layers have different geometries along the length of the subsea umbilical composite tube.

For example, the subsea umbilical composite tube of the present invention could comprise either two or three or four combined composite layers, with at least two of the combined composite layers having different geometries along the length of the subsea umbilical composite tube. The different geometries could be in the form of differences in the speed, winding, orientation, timing, thickness, etc. of each combined composite layer onto the liner.

The subsea umbilical composite tube could be formed with multi-braided or multiwound structured layers, which exhibit anisotropic characteristics, with enhanced burst pressure characteristics, collapse pressure characteristics, increased bending characteristics, tensile loads, and compression loads.

In one embodiment of the present invention, the composite reinforcement layer has a composite braided structure formed of two or three or more fibres or tapes braided or wound in particular orientations and embedded in a matrix. A first structural layer could helically or axially extend along the longitudinal axis of the liner. A second braiding layer could then be added thereover clockwise and helically oriented relative to the first structural layer, or relative to the longitudinal axis of the liner. A third braiding fibre could then be added thereover counter-clockwise and helically oriented relative to the first structural fibre, or relative to the longitudinal axis of the liner.

Optionally, the subsea umbilical composite tube of the present invention comprises a pulformed composite reinforcement layer, discussed in more detail hereinafter. For example, the subsea umbilical composite tube has either a pulbraided composite reinforcement layer or a pulwinded composite reinforcement layer.

The thermoplastic cover of the composite tube of the present invention provides an oversheath, to prevent wear and mechanical damage to the composite tube in terms of handling, laying, and then once installed. The size, thickness and nature of the thermoplastic cover may be the same as known in the art. The thermoplastic cover thickness range can be in the range between 1mm to 2mm. The thermoplastic cover includes the use of known materials such as HDPE, which can be applied in a continuous coating manner to the outside of the composite reinforcement layer in a manner known in the art. The tube oversheath is used for mechanical protection, wear and insulation.

In another embodiment of the present invention, the subsea flexible composite tube comprises at least a thermoplastic liner, a composite reinforcement layer, and a thermoplastic cover, bonded together to form a solid fully bonded structure.

The subsea flexible composite tube can be a fully bonded structure in the manner of all layers being bonded together to obtain a single solid wall thickness, and each layer cannot move relatively to each other when the flexible composite tube is put under any stress or strain, such as spooling or bending.

Optionally, the at least thermoplastic liner, composite reinforcement layer, and thermoplastic cover are bonded together using one or more of the group comprising: adhesive, adhesive film, mesh, chemical bonding, mechanical bonding and natural bonding.

That is, the bonding together the layers of the subsea flexible composite tube may include one or more additional bonding means or processes, such as using adhesive or an adhesive film, a mesh, or a chemical process or a mechanical process. Examples of suitable adhesives include epoxy adhesive, polyurethane, acrylics, etc, and examples of a suitable mesh include a monofilament polyester textile.

Alternatively, the bonding together of the layers of the subsea flexible composite tube may be achieved using natural bonding, that occurs by bringing together, typically using heat and/or pressurisation, the thermoplastic liner, composite reinforcement layer and/or the thermoplastic cover, to form a fully bonded structure. Natural bonding can occur when the nature and/or materials of two neighbouring layers are sufficiency similar as to naturally bond together during manufacture. For example, by selecting the same or sufficiently similar polymer material for the liner and/or the composite reinforcement polymer matrix and/or the cover.

Optionally, the subsea flexible composite tube of the present invention includes one or more additional layers. Such one or more additional layers may assist the properties of the composite tube, including both mechanical and chemical properties. For example, an additional layer may be selected from the group comprising: pressure barrier, pressure retention layer. A pressure barrier layer can prevent external pressure from being directly applied to the outer surface of the inner liner, thereby preventing exterior pressure from collapsing the inner liner. A pressure barrier layer can be formed of an impermeable or non-impermeable material such as either polymeric film (including polyester), thermoplastic, thermoset film, elastomer or a non-bonded braiding layer.

The present invention can provide and use a thermoplastic liner which can be provided at any length and be formed in a seamless manner. This can provide a continuous and seamless liner.

The present invention can provide and use a thermoplastic cover which can be provided at any length and be formed in a seamless manner. This can provide a continuous and seamless cover.

As such, the present invention can be provide a continuous, or a seamless, or a continuous and seamless composite tube, for any length required. This provides better assurity to the user, by avoiding or minimising the need for any joins or joints for the length of composite tube required in a subsea location or industry.

Because a thermoplastic liner for the present invention can be achieved with any relative thickness, and a composite reinforcement layer can be provided with a suitable thickness designed to achieve the parameters of the composite tube in use, and a thermoplastic cover can be applied as a heat-formed coating around the composite reinforcement layer, the present invention can provide a composite tube which can have a bore of less than 1.5 inches (38mm). The provision of non-steel tubes for use in many subsea locations, in particular in subsea industries for transporting particular fluids such as corrosion inhibitors, methanol, paraffin inhibitors, hydrocarbons, hydrogen, seawater, etc. has not previously been achievable where the bore of the tube is less than 1.5 inches (38mm).

Optionally, the subsea umbilical composite tube has a bore of 0.5 inches (12.7mm) or % inches (19.05mm). A small or smaller bore size allows the composite tube of the present invention to be used where tighter bends or bending is required. This may be a requirement in fluid conduits in umbilical systems.

Thus, the present invention can provide a composite tube which is not only less expensive than traditional steel tubes and thermoplastic hoses, but has improved fatigue resistance, whilst being able to have a relatively small bore diameter still able to withstand various pressure ranges and elevated temperatures.

In particular, the present invention provides a subsea flexible composite tube being a fluid-transporting subsea flexible composite tube.

The present invention includes a method of manufacturing a subsea flexible composite tube comprising at least the steps of: providing a thermoplastic liner; adding a composite reinforcement layer over the thermoplastic liner; and adding a thermoplastic cover over the composite reinforcement layer to form a subsea flexible composite tube.

Providing a thermoplastic liner is known in the art. Thermoplastic liners can be formed of any suitable dimensions, including any suitable bore and/or wall thickness, in a continuous and seamless manner. Suitable materials for a thermoplastic liner for use in the present invention are discussed above.

The composite reinforcement layer can be provided over the thermoplastic liner in various manufacturing processes such as pulwinding or pulbraiding, including pulforming methods such as pultrusion. The composite reinforcement layer can also be added over the thermoplastic liner using other laying manufacturing processes, such as Automated Tape Laying (ATL).

Pultrusion uses continuous unidirectional fibres (typically in the form of tows, rovings or tapes) impregnated with a thermosetting resin and fed into a heated die to be shaped into the desired cross section and cured into a finished product. As the material progresses through the die, the applied heat triggers the cure reaction, and the resulting solid product is pulled through the die by a pulling device.

The process aims to produce a cured part before the product exits the die. The pulling speed is therefore related to the curing kinetics of the resin system being used and the die length. For epoxy based products, the pulling speeds is around 200 mm/min. With epoxy-based systems, full cure is not normally achieved before the part exits the die, and post-curing operations need to be considered (either on- or off-line).

An uninterrupted manufacturing process is preferred. The use of a pulforming process such as pulwinding or pulbraiding, allows the addition of the composite reinforcement layer to be achieved in a continuous, or seamless, or continuous and seamless manner, and typically in a low cost format. Further, the use of a pulforming process to apply the composite reinforcement layer does not limit the size of the composite tube that can be formed, in particular where the bore of the tube is less than 1.5 inches (38mm). Thus, the present invention can form small-bore thermoplastic composite tubes.

The addition of the composite reinforcement layer over the thermoplastic liner provides a method of adding a reinforcement such as a glass fibre or carbon fibre, to be embedded or commingled in a thermoplastic or thermoset matrix. Various processes or methods are known to provide a reinforcement fibre matrix that can be formed for example from a commingled yarn, or from prepreg or towpreg tapes or fibres, or using other forms of extrusion. These methods can achieve a continuous and seamless method of forming a final composite reinforcement layer around the thermoplastic liner.

Optionally, the step of adding a composite reinforcement layer over the thermoplastic liner comprises at least the steps of: providing one or more sets of fibres; providing a thermoplastic or thermoset matrix; combining the or each set of fibres with the thermoplastic or thermoset matrix to form one or more combined composites layers; and pulforming the combined composites layer(s) over the thermoplastic liner.

The or each set of fibres may be provided with a thermoplastic or thermoset matrix therewith, or to be combined with the thermoplastic or thermoset matrix as part of the method of manufacture. The sets of fibres can be provided as fibres per se, or as part of prepreg, hybrid or towpreg tapes, or commingled yarns.

Optionally, the method of manufacturing comprises providing a plurality of sets of fibres in series, i.e. each set of fibres is provided in series. Optionally, each set of fibres is provided alongside a thermoplastic or thermoset matrix to form each combined composites layer.

Optionally, the method of manufacturing comprises providing a plurality of sets of fibres simultaneously, i.e. all the fibres are provided in a way that each set forms a composite layer with an associated thermoplastic or thermoset matrix.

Preferably, the method of manufacturing comprises providing a plurality of sets of fibres, and a thermoplastic or thermoset matrix for each set of fibres. Optionally, the thermoplastic or thermoset matrix for each set of fibres is provided alongside, or in pre-combination with, the fibres.

Optionally, the provision of the sets of fibres and the thermoplastic or thermoset matrix provides a consolidation of the fibres and matrix on the thermoplastic liner, optionally as a series of structured layers.

Optionally, the method of manufacturing comprises more than one repeat process to add all of the series of combined composites layers to form the final composite reinforcement layer.

Optionally, the method of manufacturing includes a heating step, a pressure step, or heating and pressure steps, as part of or after combining the or each set, or as part of or after combining all sets, of the fibres and thermoplastic or thermoset matrix to form each combined composites layer. Optionally, the heating and pressure steps are either as a first heating step followed by a pressure step, or as a combined heating and pressure step.

Optionally, any pressure step in the method of manufacturing is provided by contact, such as contact via rollers or via vacuum.

Optionally, any heating or pressure steps assists impregnation of the fibres by the thermoplastic or thermoset material of the matrix, and bonding of the combined composite layers with the thermoplastic liner.

Optionally, the step of pulforming the combined composites layers over the thermoplastic liner includes simultaneous parallel winding of each combined composites layer around the thermoplastic liner.

Alternatively or additionally, the step of pulforming the combined composites layers over the thermoplastic liner includes simultaneous parallel braiding of each combined composites layer around the thermoplastic liner.

In one embodiment of the present invention, the step of adding a composite reinforcement layer over the thermoplastic liner comprises at least the steps of: providing a plurality of sets of fibres and thermoplastic or thermoset matrix in the form of pre-impregnated fibres to form a plurality of combined composites layers; pulforming the combined composites layers over the thermoplastic liner; heating and optionally pressuring the combined composites layers to form the composite reinforcement layer.

Optionally, any heating step is followed by a cooling step.

Optionally, the composite reinforcement layer is provided as a series of prepreg, hybrid or towpreg tapes, or as a series of prepreg, hybrid or towpreg yarns, or commingled yarns. Optionally, such tapes have a width in the range from 2.0mm to 20.0mm, and a thickness in the range from 0.2mm to 2.0mm. Optionally, any commingled yarns used in the present invention have a diameter in the range from 1.0mm to 12.0mm. Optionally, the method of manufacturing as defined herein is to form a subsea umbilical composite tube as defined herein.

Optionally, the method of manufacturing may further comprise a bonding process or adding a bonding layer between the thermoplastic liner and the composite reinforcement layer.

Optionally, the method of manufacturing may further comprise a bonding process or adding a bonding layer between the composite reinforcement layer and the thermoplastic cover.

Optionally, the method of manufacturing may include both of the bonding processes or bonding layers described above, to provide a final solid fully bonded structure. As described herein, the bonding layer may be in the form of an adhesive, mesh, or surface treatment that could be applied between the thermoplastic liner and the structural layer provided by the composite reinforcement layer.

Optionally, the composite reinforcement layer is added in the method of manufacture using pulforming. A pulforming manufacturing process allows relative easy changing of the fibre material orientation, as well as changing the ratio of fibres in relation to the matrix, to allow the manufacturer to achieve the desired mechanical and physical characteristics for the composite layer, and thus to the final subsea flexible composite tube. Thus, pulforming provides a flexible process to the manufacturer, whilst also providing a high process stability, and a high output at a low cost.

Many resin types may be used in pultrusion including polyester, polyurethane, vinyl ester and epoxy. But the technology is not limited to thermosetting polymers. Pultrusion has been successfully used with thermoplastic matrices such as polybutylene terephthalate (PBT), polyethylene terephthalate (PET) either by powder impregnation of the glass fibre or by surrounding it with sheet material of the thermoplastic matrix, which is then heated.

The pulforming process can include the use of commingled yarns, tapes or towpreg filaments, to be added preferably in a braided or winded manner, directly on to the thermoplastic liner, creating a fully bonded product using braiding or winding appliances positioned in front of a pultrusion apparatus or device.

Thus, the present invention also provides apparatus for manufacturing a subsea flexible composite tube comprising at least a thermoplastic liner, a composite reinforcement layer comprising a plurality of fibres and a thermoplastic or thermoset matrix, and a thermoplastic cover, the apparatus comprising a plurality of bobbins arranged to be rotatable in relation to the thermoplastic liner, and able to wind or to braid, or both wind and braid, continuously, the fibres around the thermoplastic liner.

Optionally, the apparatus for manufacturing of the present invention is able to vary one of more of the group selected from: number of bobbins, angle of the bobbins relative to the thermoplastic line; size of the fibres or prepreg tapes on the bobbins; speed of the winding or braiding, speed of both the winding and the braiding.

Optionally, the apparatus for manufacturing comprises the bobbins able to provide the fibres in the form of fibres, commingled yarns or pre-preg tapes.

Optionally, the apparatus for manufacturing is able to provide pulforming or pultrusioning of the composite reinforcement layer around the thermoplastic layer.

The composite tube of the present invention also provides a lower CO2 footprint than a conventional tube or umbilical.

Overall the composite tube can be used as, or for, or in, a lighter weight umbilical. The lighter weight composite tube is therefore easier to handle than a conventional umbilical incorporating only steel tubes. With the advantages of enhanced hydrostatic pressures and enhanced mechanical properties under dynamic loading and fatigue, the composite tubing is particularly suited for use in the oil and gas subsea situations, such as but not limited to as part of an umbilical construction to transport fluids or perform other operations traditionally carried out with steel tubing or hoses.

The composite tube of the present invention may be capable of withstanding internal pressures of greater than 3,000psi (20.7MPa) design pressure, and preferably greater than 5,000psi (34.5MPa) design pressure. The composite tube of the present invention may be capable of withstanding a burst pressure or burst phenomenon of up to 30,000psi (207MPa). The composite tube of the present invention may have a <1.5” (38mm) Nominal bore designed for deep I ultra-deep waters (1000m to 2000m water depth).

The composite tube of the present invention can be designed to carry a variety of fluids, such as, for example, hydraulic oil, hydraulic fluid such as water and glycol, methanol for hydration suppression, or hydrogen or various other types of fluids used in umbilicals hydraulic lines.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings. Figure 1a shows a first subsea flexible composite tube 10 comprising a thermoplastic liner 12 as a Layer 1 , a composite reinforcement layer 14 as a Layer 2, and a thermoplastic cover 16 as a Layer 3. Examples of Layers 1 , 2 and 3 are set out in the following table.

Figure 1b is a part cut-away section of Figure 1a from a different perspective, showing the subsea flexible composite tube 10 having the inner thermoplastic liner 12, the surrounding composite reinforcement layer 14, and the surrounding thermoplastic cover 16. Figure 1b shows the inner bore or diameter 15 of the composite tube 10, which can be < 1.5 inches (38mm), such as

inch (12.7mm) or % inch (19mm).

Figures 1c and 1d show a first particular embodiment of the present invention. Figures 1c and 1d show similar perspective and part-open views as Figures 1a and 1b of a subsea flexible composite tube 10a, comprising a thermoplastic liner 12a, a composite reinforcement layer 14a based on glass fibres and HDPE, and a HDPE thermoplastic cover 16a. Figure 1d shows the inner bore or diameter 15a of the composite tube 10a.

Figures 1e and 1f show a second particular embodiment of the present invention. Figures 1e and 1f show similar perspective and part-open views as Figures 1a and 1 b of a subsea flexible composite tube 10b, having comprising a thermoplastic liner 12b, a composite reinforcement layer 14b based on carbon fibres and PA or HDPE, and a HDPE thermoplastic cover 16b. Figure 1f shows the inner bore or diameter 15b of the composite tube 10b.

Figures 2a and 2b show different views of a second subsea flexible composite tube 20 embodiment, comprising a thermoplastic liner 22, a first additional bonding layer 24 between the liner 22 and a composite reinforcement layer 26, a second additional bonding layer 28 between the composite reinforcement layer 26 and a thermoplastic cover 29. The nature of these first and second interface (adhesive) layers 24 and 28 is to improve the bonding between the liner 22 and the composite reinforcement layer 26, and between the composite reinforcement layer 26 and the thermoplastic cover 29. The first bonding layer 24 provides a mechanism for bonding the liner 22 to the composite layer 26 such that the liner does not collapse under high external pressures. The thermoplastic liner 22, composite reinforcement layer 26, and thermoplastic cover 29 may be the same as those described hereinabove.

Figure 3a shows a third subsea flexible composite tube 30 comprising a thermoplastic liner 32, a composite reinforcement layer 36 and a thermoplastic cover 39. Figure 3a also shows a bonding 34 between the thermoplastic liner 32 and the composite reinforcement layer 36, being for example an adhesive or an adhesive film. Figure 3a also shows a pressure retention layer 38 such as kevlar-aramid layer between the composite reinforcement layer 36 and the thermoplastic cover 39. The thermoplastic liner 32, composite reinforcement layer 36, and thermoplastic cover 39 may be the same as those described herein above.

The pressure retention layer 38 such is typically a braided kevlar-aramid armoring layer.

Figure 3b is a part cut-away section of Figure 3a from a different perspective, showing the subsea flexible composite tube 30 having the inner thermoplastic liner 32, the surrounding composite reinforcement layer 36, and the surrounding thermoplastic cover 39. Figure 3b shows the inner bore 35 of the composite tube 30, which can be < 1.5 inches (38mm).

Figures 4a and 4b show different views of a fourth subsea flexible composite tube 40 embodiment, comprising a thermoplastic liner 42, additional bonding layer 44 between the liner and the reinforcement layer which is used to create a seal between layers a composite reinforcement layer 46, additional bonding layer 48 applied between the composite reinforcement layer 46 and the thermoplastic cover 49. The nature of these additional bonding (adhesive) layers can favour the chemical or mechanical boding between layers creating a sealed structure. The interface layer 44 or 48 improves the bonding between the liner 42 and the composite layer 46 or between the composite reinforcement layer 46 and the thermoplastic cover 49, increasing the adhesion and creating a latching between layers.

Figure 5 is a flow diagram of option pathways that can be selected by a manufacturer in a method of manufacturing a subsea flexible composite tube according to the present invention. The manufacturer and designer will have considered the function required for the composite tube, along with the desired shape and materials, and whether the composite tube is to be used in a greater umbilical structure and/or alongside other umbilical components in the subsea industry, in particular in fluid transportation in an oil and gas industry.

The designer and manufacturer will consider the characteristics of what materials are desired to be used, the shape and size of the subsea flexible composite tube, as well as the minimum thicknesses required alongside consideration of overall costs. From this, the method of manufacturing can be a known laying procedure for adding the composite reinforcement layer over a thermoplastic liner, but is preferably based on a pultrusion process, in particular pulforming.

Pulforming is a manufacturing process known in the art, which can be provided as pulwinding or pulbraiding, and which can be used for the manufacturing of continuous and seamless thermoplastics and thermosets, especially in the form of small bore tubes in a low cost format.

Using a thermoset matrix in Figure 5 provides a low viscosity material, wherein fibres to be embedded in the thermoset matrix can be wetted in a bath. The wetting can be provided using a suitable bath or chamber, and/or use an injection box as described in more detail hereinafter.

Using a thermoplastic matrix in Figure 5 provides the manufacturer with a choice of either a reactive process based on using a catalyst or activator as required (usually to improve the viscosity), followed by reaction injection moulding (RIM) pultrusion.

Alternatively, there is a non-reactive thermoplastic manufacturing process, which may use various alternatives as the feed stock, including prepregs or towpregs in the form of polymer filaments, or the use of polymer powders or polymer melts.

A thermoplastic matrix typically has a higher viscosity than a thermoset matrix. The use of drums or bobbins with pre-impregnated tapes or yarns, typically being hybrid or commingled yarns combining the reinforcement in the thermoplastic fibres, allows the use of pre-heating zones before pulling the feed stock through a suitable heated die and then cooling. The thermoplastic feedstock can be provided in the form of filaments which can be braided or winded directly onto the thermoplastic liner, creating a fully bonded product using braiding or winding appliances positioned in front of the pultrusion machine.

Figures 6a and 6b show a series of braiding decks 52, each braiding deck 52 having a series of bobbins of braiding heads providing a series of prepreg filaments 54 as part of a thermoplastic pulforming process 50, in order to add the filaments 54 in a winding and braiding nature around a prior formed thermoplastic liner 56 provided from a payoff drum 51 .

Each braiding deck 52 simultaneously provides its set of fibres and associated thermoplastic or thermoset matrix, in the form of the prepreg filaments 54, over the thermoplastic liner 56, to thereby form a combined composites layer. Figures 6a and 6b show two braiding decks 52 to provide two combined composite layers added in series over the thermoplastic liner 54. The combination of liner 54 and composite layers then pass through pultrusion tensioners 62, a heating chamber 58, and a cooling die 60, to provide a final form of the thermoplastic liner and composite reinforcement layer added therearound, which can be reeled onto a take up drum 64. The heating chamber 58 may include pressure rollers and/or a vacuum to assist the forming of the composite reinforcement layer.

In this way, the multiple braiding heads of each braiding deck will each apply one composite layer of braided composite to the liner. This can achieve faster fabrication as the forming product is not required to pass the same production line again for a subsequent layer, so that multiple decks result in a more efficient production.

Optionally, a thermoplastic liner could pass through one or parts of the processing discussed hereinabove and/or as shown in Figures 6a and 6b, to add additional combined composite layers and/or to increase the heating and/or pressuring, to provide the final form of the composite reinforcement layer.

In Figure 7, a subsea composite tube umbilical is shown. The subsea umbilical comprises a plurality of components in a bundle arrangement, including one or more hydraulic lines formed of composite tubes of the invention (ref. C and D), at least one electrical cable (ref. A), at least one strength / weight member (ref. B) which can be a steel strand, a steel or a carbon rope/rod, a plurality of spacers I fillers to maintain the overall structure organisation, or combinations thereof.. A multitude of composite tubes in various bore sizes up to 1/2” bore can be used in the same umbilical crosssection in combination with other various umbilical components. For example, Figure 7 shows an umbilical cross-section comprised of only composite tubes as hydraulic lines part of the same umbilical construction (8 x 12.7mm (1/2”) Nominal Bore and 6 x 19.05mm (3/4”) Nominal Bore) in conjunction with two electrical cables and three strength/weight members. In an alternative embodiment of a subsea umbilical of the invention (not shown), the umbilical comprises a plurality of weight or strength members interspersed with a plurality of composite tubes or a mixture of thermoplastic hoses, steel (i.e. SDSS) tubes and composite tubes. Furthermore, in certain cases where it is required or desirable, other components like optical fibre, hollow fillers, etc. can be added to the bundle.

The final combination of composite reinforcement layer and thermoplastic liner can then be passed to a suitable thermoplastic covering station (not shown), known in the art and able to provide a raised temperature thermoplastic in the form of a coating former around the composite reinforcement layer, followed by a suitable cooling process to form the final subsea flexible composite tube (not shown). And finally being coiled on a movable reel (not shown).

In the present invention, a braiding process of comingled yarns or preimpregnated tapes allows for the cost-effective production of composite tube due to its high degree of automation. One of the key design parameters of braided composite tube is the angle of the fibres with respect to the longitudinal 0° axis. The pulforming manufacturing processes (pulwinding or pulbraiding) exhibits a high process speeds, easy productivity, excellent load adaption, and flexibility, making it more cost- effective than the Automated Tape Lay-out (ATL) conventional manufacturing method used for making subsea oil and gas tubes.

Benefits of the present invention include:

Improved flow assurance with improved response time as the composite tube is stiffer and may have less volumetric expansion than an thermoplastic aramid reinforced hose. Improved collapse resistance compared with a conventional thermoplastic aramid reinforced hose.

Improved bore roughness compared with a conventional SDSS tube.

Reduction in weight compared with a conventional steel tube. Less weight improves product weight limitation on reels and improves umbilical installation, thus requiring smaller installation vessels, smaller lifting equipment’s, etc. - which will reduce CO2 emissions as overall. Reduced weight also reduces the conventional need for umbilical buoyancy modules, improving the umbilical Free Hanging catenary.

Claims

1 . A subsea umbilical composite tube comprising at least a thermoplastic liner, a composite reinforcement layer, and a thermoplastic cover.

2. A subsea umbilical composite tube as claimed in claim 1 wherein the thermoplastic liner is one or more of the group comprising: Nylon 11 , Nylon 12, Polyethylene (PE), Cross-linked Polyethylene (XPLE) and Polyethylene-Raised Temperature (PE-RT).

3. A subsea umbilical composite tube as claimed in claim 1 or claim 2 wherein the composite reinforcement layer is one or more of the group comprising: glass fibres or carbon fibres embedded in a thermoplastic matrix or a thermoset matrix.

4. A subsea umbilical composite tube as claimed in claim 3 wherein the thermoplastic matrix is one or more of the group comprising: Nylon (PA), Polyethylene (PE)

5. A subsea umbilical composite tube as claimed in claim 3 or claim 4 wherein the composite reinforcement layer comprises carbon fibres or glass fibres embedded in a thermoplastic matrix, such as Nylon or Polyethylene thermoplastic matrix.

6. A subsea umbilical composite tube as claimed in claim 3 wherein the thermoset matrix is one or more of the group comprising: vinyl ester and epoxy.

7. A subsea umbilical composite tube as claimed in any one of the preceding claims wherein the composite reinforcement layer comprises a series of combined composite layers.

8. A subsea umbilical composite tube as claimed in claim 7 wherein two or more of the series of combined composite layers have different geometries along the length of the subsea umbilical composite tube.

9. A subsea umbilical composite tube as claimed in claim 8 comprising either two or three or four combined composite layers, and wherein at least two of the combined composite layers have different geometries along the length of the subsea umbilical composite tube.

10. A subsea umbilical composite tube as claimed in any one of the preceding claims having a pulformed composite reinforcement layer.

11. A subsea umbilical composite tube as claimed in claim 10, having either a pulbraided composite reinforcement layer or a pulwinded composite reinforcement layer.

12. A subsea umbilical composite tube as claimed in any one of the preceding claims wherein the thickness of the composite reinforcement layer is in the range of 1 mm to 8mm, preferably in the range of 1 ,5mm to 4.5mm.

13. A subsea umbilical composite tube as claimed in any one of the preceding claims wherein the thermoplastic liner, composite reinforcement layer, and thermoplastic cover, are bonded together to form a solid fully bonded structure.

14. A subsea umbilical composite tube as claimed in claim 13 wherein the thermoplastic liner, composite reinforcement layer, and thermoplastic cover, are bonded together using one or more of the group comprising: adhesive, adhesive film, mesh, mechanical bonding and natural bonding.

15. A subsea umbilical composite tube as claimed in any one of the preceding claims further comprising one or more additional layers selected from the group comprising: a pressure barrier and a pressure retention layer.

16. A subsea umbilical composite tube as claimed in any one of the preceding claims wherein the bore of the subsea umbilical composite tube is less than 1.5 inches (38mm).

17. A subsea umbilical composite tube as claimed in claim 16 wherein the bore of the subsea umbilical composite tube is either 1/2 inches (12.7mm) or % inches (19.05mm).

18. A subsea umbilical composite tube as claimed in any one of the preceding claims wherein the subsea umbilical composite tube is seamless.

19. A subsea umbilical composite tube as claimed in any one of the preceding claims being a fluid-transporting subsea umbilical composite tube.

20. A method of manufacturing a subsea umbilical composite tube comprising at least the steps of: providing a thermoplastic liner; adding a composite reinforcement layer over the thermoplastic liner; and adding a thermoplastic cover over the composite reinforcement layer to form a subsea umbilical composite tube.

21. A method of manufacturing as claimed in claim 20 further comprising a bonding process or adding a bonding layer between the thermoplastic liner and the composite reinforcement layer.

22. A method of manufacturing as claimed in claim 20 or claim 21 further comprising a bonding process or adding a bonding layer between the composite reinforcement layer and the thermoplastic cover.

23. A method of manufacturing as claimed in any one of claims 20 to 22 wherein the composite reinforcement layer is added using pulforming, optionally using pulbraiding or pulwinding.

24. A method of manufacturing as claimed in any one of claims 20 to 23 wherein the step of adding a composite reinforcement layer over the thermoplastic liner comprises at least the steps of: providing one or more sets of fibres; providing a thermoplastic or thermoset matrix; combining the or each set of fibres with the thermoplastic or thermoset matrix to form one or more combined composites layers; and pulforming the combined composites layer(s) over the thermoplastic liner.

25. A method of manufacturing as claimed in claim 24 comprising providing a plurality of sets of fibres in series or simultaneously.

26. A method of manufacturing as claimed in claim 24 or claim 25 comprising providing a plurality of sets of fibres and a thermoplastic or thermoset matrix for each set of fibres.

27. A method of manufacturing as claimed in any one of claims 24 to 26 including a heating step, a pressure step, or heating and pressure steps, as part of or after combining the or each set of fibres, or as part of or after combining all sets, and the thermoplastic or thermoset matrix to form each combined composites layer.

28. A method of manufacturing as claimed in claim 27 having heating and pressure steps, either as a first heating step followed by a pressure step, or as a combined heating and pressure step.

29. A method of manufacturing as claimed in claim 27 or claim 28 wherein any pressure step is provided by contact, via rollers or via vacuum.

30. A method of manufacturing as claimed in any one of claims 24 to 29 wherein the step of pulforming the combined composites layers over the thermoplastic liner includes simultaneous parallel winding of each combined composites layer around the thermoplastic liner.

31 . A method of manufacturing as claimed in any one of claims 24 to 29 wherein the step of pulforming the combined composites layers over the thermoplastic liner includes simultaneous parallel braiding of each combined composites layer around the thermoplastic liner.

32. A method of manufacturing as claimed in any one of claims 20 to 31 wherein the composite reinforcement layer is provided as a series of prepreg, hybrid or towpreg tapes.

33. A method of manufacturing a subsea umbilical composite tube as defined in any one of claims 1 to 19.

34. Apparatus for manufacturing a subsea umbilical composite tube comprising at least a thermoplastic liner, a composite reinforcement layer comprising a plurality of fibres and a thermoplastic or thermoset matrix, and a thermoplastic cover, the apparatus comprising a plurality of bobbins arranged to be rotatable in relation to the thermoplastic liner, and able to wind or to braid, or both wind and braid, continuously, the fibres around the thermoplastic liner.

35. Apparatus as claimed in claim 34 able to vary one or more of the group selected from: number of bobbins, angle of the bobbins relative to the thermoplastic line; size of the fibres on the bobbins; speed of the winding or braiding, speed of both the winding and the braiding.

36. Apparatus as claimed in claim 34 or 35 wherein the bobbins provide the fibres in the form of fibres, commingled yarns or pre-preg tapes.

37. Apparatus as claimed in any one of claims 34 to 36 able to pulform or pultrude the composite reinforcement layer around the thermoplastic layer.

38. Apparatus as claimed in 37 able to pulwind or pulbraid the composite reinforcement layer continuously and seamlessly around the thermoplastic layer.

39. Apparatus as claimed in any one of claims to able to provide a subsea composite flexible tube as defined in any one of claims 1 to 19.

40. A subsea umbilical comprising at least one subsea umbilical composite tube as defined in any one of claims 1 to 19.

41 . A subsea umbilical composite tube as claimed in any one of claims 1 to 19 for use in the transportation of a fluid such as oil, gas, CO2, hydrogen gas, hydrogen sulfide.

42. A subsea umbilical as claimed in claim 40 further comprising one or more electrical cables, optical fibre cables, hydraulic lines, strength members or combinations thereof.

43. A subsea umbilical as claimed in any one of claims 40 to 42 wherein the subsea umbilical is an Integrated Production Bundle (IPB) product.

44. A subsea umbilical as claimed in any one of claims 40 to 42 wherein the subsea umbilical is an Integrated Service Umbilical (ISU).

45. A subsea umbilical as claimed in any one of claims 40 to 42 wherein the subsea umbilical is an Integrated Production Umbilical (IPU).