EA043152B1 - COMPOSITE TUBULAR ELEMENT AND METHOD FOR ITS MANUFACTURE - Google Patents

Description

The present invention relates to tubular structures intended for use in underwater environments. In particular, the invention relates to composite tubular structures for use in the oil and gas industry, such as production risers, and a method for their manufacture.

State of the art

In the past few years, various patents have been filed relating to flexible composite risers and tubing, revealing the use of relatively similar materials and designs.

Patent document WO 2013/071449 describes a glued construction containing three main areas (inner, reinforced and outer layers). Reinforced (reinforced) layers are created using helically wound tapes made of fiber-reinforced thermoplastic polymers. In addition, said patent document provides some specific data regarding suitable materials (polymers and fibers) for each layer, indicating material selection criteria in terms of thermal and/or mechanical characteristics, chemical compatibility, or requirements related to installation conditions or operating conditions.

Patent document WO 1999/67561 describes a glued construction containing three main areas (inner, reinforced and outer layers). This document describes reinforced layers that are formed using various laminates of thermoplastic or thermoset polymers reinforced with reinforced unidirectional continuous fibers. In addition, some specific data are given regarding suitable materials (polymers and fibers) for each layer and changes in the composition or microstructure in each layer in order to make them able to withstand local temperature conditions and local pressures, while optimizing material compatibility.

The design proposed in said patent document is a reinforced polymer element made from single layers of thermoplastic matrices reinforced with various fibers. In addition, the described riser design may also include intermediate layers formed from a specially selected thermoplastic polymer, from among the mentioned thermoplastic matrices, reinforced with various fibers. These layers are designed to be used as gap stops and improve thermal insulation between other layers. The presence of fiber-free sublayers will also create some slip between adjacent fiber-reinforced layers, making the pipe more flexible.

In WO 2006/059220, a composite piping system uses a composite riser to provide a lower mass conveyance section connected to the floating plant via upper and lower portions formed by metal or non-glued end piping. The described system includes a central part formed by a composite pipeline, which makes up most of the length of the riser, while its length is much greater than the length of the sections of the upper or lower end pipelines.

Patent document WO 2010/096671 describes a glued construction of a composite pipeline containing three main sections (inner, reinforced and outer layers). The reinforced middle layer is characterized by a multi-layer structure formed in the middle layer by an inner layer of composite tapes, a middle layer of thermoplastic material and an outer layer made of a harder thermoplastic, described below. For the manufacture of composite pipelines, a mobile unit is used. In addition, for each layer, some specific data are given regarding the selection of suitable materials (polymers and fibers).

WO 2010/096671 describes a composite pipeline with a thermoplastic inner layer, a tape layer glued to the thermoplastic layer, and a protective layer formed over the tape layer. Thus, the pipeline contains three layers, while the inner layer may be a layer of thermoplastic material; the middle layer may be a layer of reinforced composite tape, which may contain a fully wetted tape and may be additionally enclosed or covered on the outside with a thermoplastic; finally, the outer protective layer may be made of a thermoplastic material. In various configurations, the middle layer is in the form of a multilayer structure, in which the inner middle layer may be a layer formed by a reinforced tape of composite material, the middle layer may be a thermoplastic extrudate or film-like layer, and the outer middle layer may be a rigid layer made of harder thermoplastic.

US 2014/0041879 describes a riser that is characterized by the presence of prestressed sections (sections in tension or compression) to provide the required spatial arrangement of the riser and create an inflection point. A characteristic feature in this patent document is the presence of a local change in the composition or microstructure of the composite wall to impart a prestressed state to the specified

- 1 043152 sections of the riser, in particular the state of tension in the upper and lower sections and, accordingly, the state of compression in the intermediate section.

US 2013/0255821 describes a riser which is characterized by making walls of composite materials with a plurality of reinforcing fibers embedded in a matrix. The riser is made with a local change in the composition or microstructure of the wall made of a composite material, with a corresponding change in mechanical properties (strength, rigidity, flexural rigidity, buckling, modulus of elasticity, etc.) or thermal characteristics (thermal expansion coefficient, thermal conductivity).

CN 103465478 describes a rubber tube comprising an inner wall, an outer wall and a frame made of a knitted fabric with a three-dimensional structure. The objective of the invention is to increase the flexibility of the pipe and create a mechanically strong and shock-resistant pipe.

Knitted fabric is a fabric structure corrugated on one side. The fabric is woven from one or a plurality of fabric fibers or from a knit tape (woven from a single or a plurality of fabric fibers). Said fabric can also be obtained by weaving fabric fibers and metal wire. The only type of fiber mentioned in the patent document is aramid. The polymer used is epoxy, plastic, rubber or polyurethane.

CN 106885062 describes a transport tube made from a three-dimensionally woven fabric having a tubular shape. The pipe is characterized by the presence of a three-dimensional weaving fabric obtained from high-strength fibers and a rubber or polymer carcass. The fabric is preferably a 3D orthogonal woven fabric or a 3D woven tubular fabric using high tenacity fibers.

At present, composite tubular members such as risers, pipes, and the like, formed from the layers described in the above examples, have a disadvantage in the delamination phenomenon, which limits the mechanical strength of the tubular member and causes damage. Cracks propagate between the layers, in particular in those places where the local load is a combination of mode I - mode II. Currently, to increase the ability of the polymer matrix to elastic deformation, a local increase in toughness is carried out, but this creates an improvement only over time.

Disclosure of the essence of the invention

In accordance with the present invention, a composite tubular element is provided for use in subsea environments, wherein the composite tubular element comprises:

at least a first layer containing first fibers oriented in the x direction relative to the longitudinal axis of the tubular element, second fibers oriented in the y direction relative to the longitudinal axis of the tubular element, thus forming a two-dimensional tubular structure;

third fibers extending at least partially through the wall thickness, resulting in a three-dimensional tubular structure;

the first thermoplastic polymer, distributed with the possibility of subsequent filling them with fibers of a tubular structure and sealing (strengthening) due to this tubular structure; and a second thermoplastic polymer introduced to fill the residual pores of the tubular structure and thus form the tubular element.

In addition, according to the present invention, a method for manufacturing a composite tubular member is provided, said method including the following steps:

manufacturing a two-dimensional tubular structure comprising first fibers oriented in the x direction relative to the longitudinal axis of the tubular element, second fibers oriented in the y direction relative to the longitudinal axis of the tubular element;

introducing third fibers at least partially through the wall thickness of the tubular element, resulting in a three-dimensional tubular structure;

combining the fibers with the first thermoplastic polymer;

introducing a second polymer to fill the residual pores of the tubular structure to form a composite tubular element.

The tubular element obtained in accordance with the invention has a strong grip over the entire cross section of the tubular element. In the case of forming a plurality of layers, the tubular element preferably has an increased resistance to the effect of delamination and the propagation of cracks under the action of stresses and loads that the tubular element experiences during its use.

Alternatively, at least one of the first, second and/or third groups of fibers contains continuous fibers. Alternatively, at least one of said groups of fibers is formed from non-crimped fibers. Alternatively, one or more groups of fibers may be formed by glass fibers, optionally glass fibers of type S2. Alternatively, the fibers may be carbon, aramid, or similar suitable fibers.

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Glass fibers have an advantage in terms of mechanical stress, like, for example, carbon fibers, but have a lower Young's modulus (typically carbon fiber has a Young's modulus of about 200 GPa, while glass fiber has a Young's modulus of 70-90 GPa) . In addition, the density of glass fiber is higher than the density of carbon fiber. The use of glass fiber thus has the advantage that the drums required to transport the coiled tubulars of the present invention can be much smaller than would be the case with similar tubulars known in the art, such as a pipeline or riser. from composite materials, which reduces the cost. The stresses experienced by the coiled tubular element are reduced, which reduces the risk of damage to the tubular element prior to use.

The use of glass fibers instead of carbon fibers results in a lower rigidity of the fabricated tubular in the longitudinal direction, which has the advantage of reducing the stress on the tubular, and therefore a lower fiber content is required for such a tubular. The reduction in mechanical stress that the tubular element may experience, depending on how the third fibers are introduced through the thickness of the element, is easily achieved and does not adversely affect the performance of the tubular element.

Where the tubular can be used as part of a riser assembly, the lower longitudinal stresses achieved and the greater flexibility of the tubular means that lower riser and upper riser assemblies are subjected to lower stresses, allowing simpler structures to be used for transferring load from the riser to the wellhead or surface structure. The floats used to support the riser on the surface of the water can be reduced in size, which reduces their cost and further reduces the stresses on the riser.

Optionally, the two-dimensional tubular structure containing the first and second fibers may be formed by weaving or weaving, for example by two-dimensional or optionally three-dimensional weaving. The three-dimensional weave makes it possible to increase the mechanical resistance against loads acting in the x-direction (longitudinal direction).

Alternatively, the structure is formed from superimposed first and/or second fibers. Optionally, the first and/or second fibers are made of straight (non-crimped) fibers, if necessary, continuous fibers. Optionally, the tubular element may be formed from non-crimped fibers which include superimposed straight fibers oriented in the x and y directions. The use of non-crimped fibers makes it possible to maximize the mechanical properties of the fibers in the longitudinal x direction and in the circumferential y direction.

Alternatively, where the two-dimensional tubular structure is formed by two-dimensional (2D) weaving, fibers of different sizes may run in different directions. For example, a weave containing the first fibers, namely a weave of fibers oriented in the x direction, parallel to the longitudinal axis of the tubular element, may be thicker than weaves in other directions. Optionally, the fiber weave angle may differ from a typical quasi-isotropic three-dimensional weave having 0, +60 and -60° fiber weaves to fully provide mechanical strength along the x and z directions with respect to the longitudinal axis of the tubular. For example, the fibers of the weaves in the x-y plane of the three-dimensional braided tubular structure can be oriented at angles φ _μ φ ₂ , for example, in the range of 30 to 80° or optionally 45 to 75° with respect to the longitudinal fibers. At the discretion, the fiber content in the x, z, φι and φ ₂ directions can be changed in accordance with the requirements established for the tubular structure. Different fiber contents or fiber patterns can be used along different directions and along the longitudinal axis of the tubular structure to achieve desired mechanical characteristics such as stiffness or strength of composite materials in different directions.

Some examples of fiber content ranges for a tubular structure formed by 2D weaving include the following: fiber content in the x direction is in the range of 20-70% by volume; the content of fibers in the z direction is in the range of 1-20 vol.%; the content of the remaining fibers refers to the fibers passing along the directions φ1 and φ ₂ . For example, for a tubular element that is subject to significant stresses in the longitudinal (x) direction, the specified contents can be 60 vol.% in the x direction, 10 vol.% in the z direction, and 30 vol.% for fibers in the φ1 and φ ₂ directions . For a three-dimensional quasi-isotropic weave, which allows almost isotropic properties in the x-y plane and proper strength in the z direction, the contents of fibers oriented in the x direction can be 30 vol.%; in the direction z - 10 vol.% and in the directions φ1 and φ ₂ - 60 vol.%.

Optionally, the first and second fibers may be combined to form a pre-

- 3 043152 compacted tapes, for example of glass fibers arranged in a straight line, filled with polyether ether ketone (PEEK). At the discretion, the tapes are superimposed one on top of the other. Optionally, the ribbons may be woven or woven into a two-dimensional tubular structure. At the discretion, the width of the tapes may differ in different directions, for example, the width of the tapes containing the first fibers may be different from the width of the tapes containing the second fibers. Optionally, the number of tapes that are simultaneously woven along a given direction may be variable. Optionally, the belts are made as narrow as possible to obtain a tubular structure having a high density.

Alternatively, if the tubular structure is formed by three-dimensional (3D) weaving, the relative contents of the fibers oriented in the x, y and z directions, respectively, can be changed, for example, to obtain the desired mechanical properties of the tubular element in all directions, for example stiffness and strength in the x, y and z directions. Achieving the desired mechanical properties is most effectively ensured by weaving without crimping.

Some examples of fiber content ranges for a tubular structure formed by 3D weaving include the following: fibers in the x direction are 30-80 vol.%, fibers in the y direction are 10-50 vol.%, fibers in the z direction are 1-20 about.%. For example, for a tubular member that is subject to high stresses in the longitudinal (x) direction, the specified fiber contents may be 70 vol.% in the x direction, 25 vol.% in the y direction, and 5 vol.% in the z direction. For a tubular member which is subjected to medium stresses in the longitudinal (x) direction, said fiber contents may be 45% by volume in the x direction, 45% by volume in the y direction and 10% by volume in the z direction. For a tubular element subject to a high risk of delamination, the indicated contents may be 40 vol.% in the x direction, 40 vol.% in the y direction and 20 vol.% in the z direction.

At the discretion, in any of the directions x, y, z, φ1 and/or φ ₂ can be used fibers of various sizes.

Alternatively, the tubular structure, and hence the tubular element, may comprise more than one fiber layer. Optionally, to create a composite tubular element, the fibers can be interlaced by three-dimensional weaving with the formation of one two-dimensional layer at a time. Optionally, immediately after the formation of the final two-dimensional layer, third fibers are introduced into/through said layers. Optionally, all third fibers may extend through the wall thickness of the tubular structure. Optionally, the third fibers contain a radial component. Optionally, the third layers can be oriented at some angle relative to the longitudinal axis of the tubular structure, for example, 50-130°. Optionally, the third fibers can be oriented in the z direction, i.e. in a direction perpendicular to the longitudinal axis of the tubular structure.

The third fibers may be introduced into the two-dimensional tubular structure by stitching, z-direction reinforcing fibers, tufting, or other similar method, thereby forming a three-dimensional structure. Optionally, the third fibers are made straight. If necessary, the third fibers are made continuous. The definition of continuous fibers is a well-known characteristic in the field of composite materials. Alternatively, the third fibers may be discrete (short) fibers, in which case the length of the third fibers must be greater than the critical fiber length. The critical fiber length is a well-known parameter in the field of composite materials reinforced with discrete fibers.

Optionally, this length may be at least equal to the total wall thickness of the pipe. The use of fibers that have a length greater than the critical length ensures that the mechanical strength of the fiber is maintained. Optionally, when using stitching, z-fibre insertion, tufting techniques to achieve three-dimensional reinforcement of the tubular element, the original two-dimensional tubular structure is optionally formed by a two-dimensional structure creation method such as weaving or fiber braiding.

Optionally, in the case of fiber interlacing, a typical mandrel can be used, and the indicated operations of stitching, insertion of reinforcing fibers along the z-axis, tufting can be carried out directly on the tubular structure. The interlacing of the fibers leaves voids through which the needle can access the fibers for stitching, insertion as reinforcing fibers in the z-axis, tufting overlay, and other such operations.

In the case of using pre-reinforced tapes to form a tubular structure, the mandrel is optionally provided on its outer surface with protruding spikes, for example, hollow spikes, which are made and placed with the possibility of punching holes in the tape located in the x-y plane and making holes in the tubular structures through which stitching, z-direction reinforcing fibers or tufting can be carried out. The density of the tapes leads to the fact that the tapes are difficult to pierce with a needle during normal stitching operations, the introduction of reinforcing fibers along the z-axis, tufting, etc., and, consequently, the presence of the mentioned spikes on the mandrel

- 4 043152 provides the creation of voids through which it is possible to carry out the mentioned operations of stitching/insertion of reinforcing fibers along the z-axis/tufting.

Optionally, the tubular structure includes a first thermoplastic polymer that combines the fibers to form a polymer matrix composite. Optionally, the fibers may be pre-embedded (coated) with a thermoplastic polymer. Optionally, the fibers are mixed with a thermoplastic polymer. Optionally, the fibers and thermoplastic polymer are in the form of pre-compacted tapes having a high density. Optionally, the pre-compacted tapes can be interlaced to form a tubular structure. The weaving of the pre-compacted tapes increases the density of the fibers in the composite tubular compared to a composite tubular made from fibers not included in the tapes.

Combining the thermoplastic polymer with the fibers means that both the fibers and the thermoplastic polymer are woven or intertwined to form, for example, a tubular structure. The use of said polymer makes it possible to reduce the fiber density in the tubular structure. However, due to the preferential reduction in stiffness in the longitudinal direction of the tubular element, the longitudinal stresses acting on the tubular element are reduced, and hence the tubular element can withstand stresses at a lower fiber density.

Alternatively, sealing the tubular structure with the thermoplastic polymer is achieved by melting the thermoplastic polymer at high temperature, if desired, without pressurizing the tubular structure. The absence of pressure on the tubular structure has the advantage that the group of third fibers oriented in the direction perpendicular to the wall thickness, for example in the z direction, does not deform, and thus these fibers remain straight and retain their reinforcing qualities. In order to reduce or prevent bending or deformation of the fibers through the thickness of the layer, pores are left in the tubular structure in the process of creating a tubular structure containing a thermoplastic polymer. The resulting porosity is higher when using three-dimensional weaving or fiber weaving, followed by stitching, z-direction reinforcing fibers or tufting, and lower when using tape weaving.

As a result of melting the thermoplastic polymer at a high temperature, a three-dimensional matrix of polymer and fibers is preferably obtained. In the event that dense tapes containing fibers and a thermoplastic polymer are woven, the melting of the thermoplastic polymer provides adhesion to one another of the various layers of tapes. As a result, the porosity of the entire structure is reduced, and the resulting structure has a high density. Optionally, polyetheretherketone (PEEK), polyphenylsulfone (PPSU), polysulfone (PSU), polyetherimide (PEI), polyimide (PI), polyamidimide (PAI) or the like can be used as the thermoplastic polymer. Optionally, the selected polymer can be replaced in accordance with the intended purpose of the tubular element.

Alternatively, the thermoplastic polymer meets the following parameters:

the glass transition temperature (Tg) is in the range of 80-150°C; while the temperature T _g must be greater than the maximum operating temperature to which the tubular element will be exposed during use; for example, the polymer will be able to withstand the temperature of the produced fluid such as oil and/or gas without degrading any mechanical properties;

resistance to chemical attack by the fluid transported in the pipeline, such as oil and corrosive substances, such as hydrogen sulfide (H2S); resistance requirements are that the material, if necessary, must be resistant to fluid for a suitable minimum period of time, while being in an unstressed state, and the mechanical properties of the material, optionally, are approximately 10-15% of the original initial properties after the material is no longer exposed to the fluid;

low degree of expansion (swelling), or lack thereof, when in contact with a fluid medium, such as oil or other substances; the composite material optionally absorbs less than 1% by volume (based on the volume of the cylindrical wall); and low permeability to selected gases, such as methane CH ₄ , hydrogen sulfide H2S, etc.; optionally, the material may have a permeability coefficient of less than 10 ^-8 cm ² /s-atm.

Alternatively, the second polymer may be a thermoset polymer, but a thermoplastic polymer may also be used. Optionally, the second polymer is introduced into the tubular structure simultaneously with the melting of the first thermoplastic polymer under high temperature conditions. This allows the structure of the tubular element to be cured to the maximum density and to fill the pores remaining in the structure of the fiber and the thermoplastic polymer in a single step. Alternatively, the second polymer is introduced into the tubular structure after dispensing the thermoplastic polymer, for example by vacuum infusion.

Optionally, the second polymer has a lower Young's modulus than the matrix composite of the first polymer. The use of a second polymer to fill the pores or voids left by the formation of a composite forming a matrix from the first polymer creates the effect

- 5 043152 additional reduction in the value of the Young's modulus of the tubular element in comparison with the use of only one of the said composite. This additional reduction has the positive effect of reducing the longitudinal stresses acting along the tubular element.

Optionally, the second polymer has a low liquid viscosity value, eg <50 Poise, i. e. at a temperature at which the second polymer is introduced into the structure containing the fibers and the thermoplastic polymer. The low viscosity value preferably increases the degree of filling of voids in the tubular structure with the second polymer.

Optionally, the second polymer has a higher deformability than the composite forming the polymer matrix. This allows the second polymer to better infiltrate the tubular structure containing the fibers and the thermoplastic polymer, and thus reduce or eliminate the formation of cracks and/or porosity, which can reduce the corrosion resistance of the tubular member.

Optionally, the second polymer is an elastomer, optionally a thermoset elastomer. The advantage of a thermoset elastomer is that it has a viscosity in the molten state sufficient to fill the voids in the tubular structure. A thermoset polymer, such as a thermoset elastomer, has the additional advantage of not requiring any correspondence between the glass transition and softening temperatures of the tubular and the operating temperature of the tubular in use, which would be necessary if used as a second polymer thermoplastic polymer.

Alternatively, the second polymer expands slightly upon contact with a transport fluid such as oil, and the degree of expansion may be determined by the amount of liquid material that can be adsorbed by the polymer, preferably less than 5% by volume expansion. This is advantageous if the tubular element is used for oil and gas operations, for example as a riser. Slight expansion of the second polymer upon contact with a transported fluid, such as oil, is advantageous in this situation, as it helps, for example, to seal the inside of the riser when its inside surface of the riser is in contact with the fluid during operation. Optionally, the second polymer has a low permeability to the transported fluid; this polymer, optionally, may have a permeability coefficient of less than 10 ^-8 cm ² /s-atm.

Optionally, the second polymer has a high chemical resistance to fluid conveyed through the tubular structure, such as oil and corrosives such as hydrogen sulfide (H ₂ S), reaching levels similar to the first thermoplastic polymer. For example, the second polymer may exhibit fluid resistance for an appropriate amount of time when in a relaxed state. Optionally, the mechanical properties of the material after the cessation of exposure to the material fluid change approximately within 10% of the original values of these properties. Optionally, the second polymer has a low Young's modulus at temperatures to which the polymer will be exposed during use.

Various aspects of the present invention may be practiced singly or in combination with one or more other aspects to be appreciated by those skilled in the art. Various aspects of the invention may optionally be embodied in combination with one or more optional features of other aspects of the invention. In addition, optionally selected features described with respect to one aspect may generally be taken on their own or combined with other features of other aspects of the invention. Any object of the invention disclosed in the present description may be combined with any other object of the invention in this description to form a new combination.

Various aspects of the invention will now be described in detail with reference to the accompanying drawings. In addition, other aspects, features and advantages of the present invention will be apparent from the full description, including the figures, which illustrate a number of examples of features and embodiments of the invention. The invention is also capable of other and various examples and aspects, and certain details may be modified in various respects without departing from the scope of the present invention. Accordingly, each example given herein is to be understood as having a broad application and intended to illustrate only one possible way of carrying out the invention, and it is not intended to limit the scope of the present description and claims to this example. In addition, the terminology and phraseology used herein is used solely for purposes of description and should not be construed as limiting the scope of the invention. Expressions such as including, containing, having, incorporating, or encompassing and various variations thereof are intended to be understood broadly and cover the subject matter described below, equivalents, and additional subject matter not described herein, and are not intended to exclude other impurities, components , integers or intervals.

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Similarly, the term containing is considered to be equivalent to the terms including or having in its composition for appropriate purposes of a legal nature. Thus, it will be understood that throughout the specification and claims, except where the context otherwise requires, the word contain, or variations thereof, such as contains or containing, is intended to include the number or groups of numbers indicated, but not to exclude any another number or group of numbers.

Any description of documents, facts, materials, devices, products, etc. included in this description solely for the purpose of disclosing the features of the present invention. It is not assumed or represented that any or all of these features of the invention are known in the art or are common knowledge in the field of technology to which the present invention pertains.

In the present description, whichever compound, element or group of elements is preceded by the word comprising, it is clear that it also means the same compound, element or group of elements with the phrases consisting mainly of, having in its composition, selected from the group consisting of, including or representing, preceding the description of the disclosure of the composition, element or group of elements, and vice versa. As used herein, words are generally or not necessarily to be understood as intended to indicate optional or non-essential features of the invention that are present in certain examples, but may be omitted in other examples without departing from the scope of the invention.

All numerical values in this description should be understood as approximate. It should be understood that all singular forms of elements or any other components described herein include plural forms thereof, and vice versa. References to relationship characteristics, such as above and below, and directions, such as up, down, etc., should be understood in the context of the examples described with the arrangements of the elements shown in the drawings, and should not be understood as limiting the invention to the literal interpretation of the term, however, they should be clear to the specialist.

Brief description of the drawings

Fig. 1 is a schematic sectional view of a tubular structure in accordance with the present invention.

Fig. 2 is a tubular structure shown with an example of different fiber directions, perspective view.

Fig. 3A-C are schematic illustrations of various fiber configurations and their respective orientations within a tubular structure.

Fig. 4 is an example of an externally studded mandrel for use in perforating braided tapes to facilitate insertion and placement of fibers in the z direction in a tubular structure.

Fig. 5 shows steps in the manufacture of a tubular element in accordance with the present invention.

Implementation of the invention

In FIG. 1 and 2 show examples of a tubular structure 1, which in this case is alternatively represented as a riser, for example a production riser, a chemical injection line, a pipeline for transporting oil, water and gas, formed from various layers or threads 50, 55 of fibers extending in the x (longitudinal) directions 10 and y (circumferentially) 12. The longitudinal fibers 10 and the fibers 12 extending in the circumferential direction are intertwined with each other in the volumetric placement of the fibers and the formation of a two-dimensional (2D) structure at the same time.

In FIG. 3C shows fiber directions based on a cylindrical coordinate system in which the longitudinal fibers are directed along the z-axis and the circumferential fibers are along the θ-axis.

When the required number of threads 50, 55 is reached, continuous fibers are introduced into the tubular structure 1, passing through the thickness, for example, in the z direction 14 (in Fig. 3C this direction is shown by the axis labeled r) using the processes of stitching, tufting or introducing reinforcing fibers along the z-axis. Through-the-thickness fibers 14 create the effect of reinforcing the various threads formed from the longitudinal 10 and circumferential 12 fibers, reducing the relative movement of the layers and preventing delamination. The introduction of added fibers 14 passing through the thickness leads to the creation of a composite preform in 3D.

The addition of through-thickness fibers 14 can degrade the mechanical performance of the longitudinal 10 and circumferential 12 fibers. To reduce this effect, non crimped fibers can be used. The use of continuous straight fibers in the x10 and y12 directions improves the mechanical properties of the fibers compared to braided crimped fibers.

Fibers 10, 12, 14 are S2 type glass fibers 36 blended with PEEK fibers 37 (see FIG. 5) which have comparable mechanical strength to carbon fibers but have a lower Young's modulus of approximately 70- 90 GPa (compared to the value of Young's modulus of approximately 200 GPa for carbon fibers), which allows greater flexibility in the resulting tubular structure 1 and finished

- 7 043152 to the final product - composite pipe 90. The density of glass fibers is less than that of carbon fibers, but not more than 20%. The resulting effect on the characteristics of the composite pipe

90 is thus the minimum.

Since the composite pipe is more flexible and in this example pipe 90 is a riser, this means that the drums required to transport the coiled riser are much smaller and the mechanical stresses that the pipe 90 is subjected to due to its winding around the drum are much less value, which reduces the risk of damage to the pipe 90 and reduces costs.

In addition, the mechanical stresses acting on the pipe 90 in the longitudinal direction are related to the stiffness of the fibers and hence the stiffness of the pipe 90. If the pipe 90 is less stiff than, for example, a pipe containing carbon fibers, this means that the pipe 90 in the longitudinal direction, a smaller stress acts, and, consequently, the deterioration of mechanical properties in the longitudinal 10 and circumferential 12 fibers, i.e. in the x-y plane of the pipe, can be tolerated to a greater extent. In the case of a riser, the consequence of lower longitudinal stresses and greater riser flexural compliance is that the stresses acting on the upper riser assembly and the lower riser assembly are smaller, necessitating a simpler system to transfer the load from riser at the wellhead or surface structure. In addition, the air-filled vessel or structure that buoys the riser can be smaller, further reducing the amount of stress on the riser and reducing costs.

Fig. 3B schematically illustrates an example of fiber directions in a tubular structure 1 which is formed by a 2D weave of longitudinal 10 and circumferential 12 fibers. The requirement for high mechanical strength in the longitudinal direction (shown by the x-axis in FIG. 3B) can be met by spatial weaving and fiber size variation in different weaving directions. The longitudinal fibers 10 are thicker than the circumferential fibers 12, which in this example are oriented at an effective ±φ angle with respect to the longitudinal fibers 10. , oriented at an angle of 0, -60 and +60°. The ±φ angles can be modified according to the function of the tube 90 to maximize the mechanical properties of the fibers. In the event that the tubular structure is obtained by three-dimensional weaving, but a quasi-isotropic formation of the weave is not suitable, the braided threads in the x-y plane, for example, can be oriented at an angle φ=45-75° relative to the longitudinal fibers.

The content of fibers 10, 12, 14 in different directions of the tubular walls (x, y and z in the case of weaving as shown in Fig. 3A; x, z and ±φ where the tubular structure 1 is formed using three-dimensional weaving as shown in Fig. 3b) can be varied in accordance with the requirements for the design of the pipe and the functional purpose of the pipe 90. Thus, different contents of fibers 10, 12 and 14 will be realized in different directions of the composite workpiece, which ensures that the desired mechanical properties (stiffness and strength) are obtained. ) pipes 90 in each direction. The angles can be changed according to the production method of each thread in the tubular structure 1.

Some examples of fiber content ranges for a tubular structure 1 formed by 2D weaving, as shown in FIG. 3B include the following: fiber content in the x direction is 20-70% by volume; fiber content in the z direction - 1-20 vol.%; the remaining fibers are oriented along directions at an angle of ±φ. For example, for a tubular element that is subject to significant stresses in the longitudinal (x) direction, the contents in the x direction may be 60 vol.%, in the z direction - 10 vol.% and in the directions ±φ - 30 vol.%. For a three-dimensional quasi-isotropic weave, which allows almost isotropic properties in the x-y plane and good strength in the z-direction, fiber contents can be 30 vol.% in the x-direction, 10 vol.% in the z-direction, and 60 vol.% in the ±φ directions .

Some examples of fiber content ranges for the tubular structure 1 formed by 3D weaving, as shown in FIG. 3A include the following: the content of fibers 10 in the x direction is 30-80 vol.%, in the y direction 10-50 vol.% and in the z direction 1-20 vol.%. For example, for a tubular member 90 that is subject to significant mechanical stresses in the longitudinal (x) direction, the fiber contents may be 70% by volume in the x direction 10, 25% by volume in the y direction 12, and 5% by volume in the z direction 14. For a tubular member 90 subjected to medium longitudinal stresses and high pressure, the fiber content may be 45 vol.% in the x direction 10, 45 vol.% in the y direction 12 and 10 vol.% in the z direction 14. For pipe 90, which is subject to a very high risk of delamination, the indicated fiber contents can be 40% by volume in the x10 direction, 40% by volume in the y direction 12 and 20% by volume of fibers in the z direction 14.

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In the event that the tubular structure 1 is formed by weaving fibers, this structure 1 can be formed using a conventional mandrel 46 with a braiding ring 42 and a bobbin 44 as shown in FIG. 5. The woven fibers form voids through which fibers can be passed in the z-direction 14 in z-direction stitching, tufting, or insertion of reinforcing fibers. The first layer of mixed fibers 35 is formed on the mandrel 46 by weaving. The other layers 55 are then woven over the first layer 50, with subsequent layers being formed at will.

Alternatively, the tubular structure 1 can be created by using pre-compacted tapes instead of fibers (not shown). The ribbons are formed from PEEK impregnated S2 type glass fibers in a single line that are woven or woven to form a composite two-dimensional (2D) preform. The width of the tapes can be changed in different directions in a similar manner to the thickness of the fibers or to maximize the mechanical characteristics of the resulting pipe 90. In contrast to the weaving of fibers, the use of tapes results in a dense structure, with a narrower tape creating a denser structure than wider tape. A mandrel 20 shown in FIG. 4. The outer surface of the mandrel 40 is provided with a plurality of hollow studs 21 attached to it and facing outward. These studs 21 pierce the layers of tape and create holes for the fibers 14 to pass through them in the z direction.

After the layers 50, 55 are formed, the fibers 14 are inserted through these layers in the z-direction by means of operations 62 of stitching, tufting or inserting reinforcing fibers along the z-axis.

Upon completion of the insertion of the fibers 14 in the z direction, the layers of the resulting structure must be densified by curing the PEEK polymer mixed with the fibers to form a densified (reinforced) tubular structure 80. The densification is achieved by introducing the tubular structure 1 into the mold 74 of the polymerization device 70, shown in FIG. 5. The heating element 72 generates a high heating temperature of the tubular structure 1, while the diaphragm 78 causes pressure to be exerted on the inner circumferential surface of the tubular structure 1, resulting in a sealed structure 80.

The use of PEEK polymer is due to the fact that it meets the following requirements for the polymer used in the sealing process:

temperature (Tg) transition to a glassy state is in the range of 80-150°C; the ability to withstand the temperature of the produced fluid, such as oil and/or gas, without degrading any of the mechanical properties;

high chemical resistance to the action of the fluid transported in the pipe, such as oil and corrosive substances, such as hydrogen sulfide (H ₂ S), - the ability to resist the action of the fluid for a suitable minimum period of time when in an unstressed state, while after the termination of the impact of the fluid on the material, the physical and mechanical (strength) properties of the composite material change within approximately 10-15% relative to the original characteristics;

little or no swelling due to contact with a fluid medium, such as oil or other substances - the composite material absorbs less than 1% of the volume, based on the volume of the tubular wall; and low permeability of selected gases, such as methane CH4, hydrogen sulfide H2S, etc., which corresponds to a permeability coefficient of less than 10 ^-8 cm ² /s atm.

The densification process may leave some degree of porosity in the densified structure 80 to reduce or prevent the fibers 14 from bending in the z direction during the densification process. A second polymer may be added to the densified structure 80 to eliminate porosity. The second polymer alternatively satisfies the following requirements:

low viscosity (<50 Poise) at infusion temperature;

high chemical resistance, comparable to the chemical resistance of the compacted structure 80;

the value of the Young's modulus of the second polymer is less than the value of the Young's modulus for the densified structure 80 in the operating temperature range;

higher deformability compared to the deformability of the densified structure 80 in the operating temperature range;

slight swelling (determined by the amount of liquid substance absorbed by the composite, which should be less than 5 vol.%) due to contact with the transported fluid, such as oil or other substances; and low fluid permeability, characterized by a permeability coefficient of less than 10 ^-8 cm ² /s atm.

The second polymer is fed into the preform using a vacuum infusion technique. The densified structure 80 is placed in the preform and a vacuum is created by sucking air out of the preform using a spiral tube 92 and a vacuum tube 94. The creation of a vacuum inside the preform leads to the suction of the second polymer into the preform through the inlet 96 and the spiral tube 93 and the introduction of the second polymer into the compacted structure 80 by vacuum. The impregnation with the second polymer results in plugging the pores remaining in the sealed structure 80 and creating the end product of the pipe 90 ready for use.

In the embodiments disclosed herein, modifications and improvements can be made without departing from the scope of the invention.

Claims (25)

1. Composite tubular element for use in underwater conditions, containing: at least a first layer comprising first fibers oriented in the x direction relative to the longitudinal axis of the tubular element and second fibers oriented in the y direction relative to the longitudinal axis of the tubular element, forming together a two-dimensional tubular structure; third fibers extending at least partially through the wall thickness of the tubular element, resulting in a three-dimensional tubular structure; a composite formed by impregnating the fibers with a first thermoplastic polymer to form a polymer matrix and thereby sealing the tubular structure; the second polymer, distributed with the possibility of filling the residual pores of the tubular element and the formation of a tubular element. 2. The tubular element according to claim 1, in which the first, second and third fibers form the first, second and third groups of fibers, respectively, while the first, second and/or third groups of fibers are formed by continuous fibers. 3. The tubular element according to claim 2, in which at least one of the first, second and/or third groups of fibers is formed by non-crimped fibers. 4. Tubular element according to any one of claims 1 to 3, wherein said fibers are glass fibers. 5. A tubular element according to any one of claims 1 to 4, wherein the two-dimensional tubular structure is formed by three-dimensional weaving. 6. The tubular element according to claim 5, wherein the three-dimensional tubular structure is formed by stitching, tufting, or introducing reinforcing third fibers along the z-axis. 7. The tubular element according to claim 6, wherein the first fibers have a first thickness and the second fibers have a second thickness, wherein the thicknesses of the first and second fibers have different values. 8. Tubular element according to any one of claims 5 to 7, wherein the second fibers are oriented at angles of ±φ with respect to the first fibers, wherein the angle φ is in the range of 30-80°. 9. A tubular element according to any one of claims 1 to 8, wherein the composite tubular element comprises more than one coaxial layer of first and second fibers. 10. Tubular element according to any one of claims 1 to 9, wherein the third fibers are continuous. 11. Tubular element according to any one of claims 1 to 10, wherein the third fibers are discontinuous and the length of the third fibers is greater than the critical length of the fibers. 12. A tubular element according to any one of claims 1 to 4, wherein the three-dimensional tubular structure is formed by three-dimensional weaving or weaving. 13. Tubular element according to any one of claims 1-12, in which the first, second and third fibers form part of all the fibers that make up the composite tubular element, while the content of the first fibers is in the range of 30-80 vol.%, the content of the second fibers is in the range of 10-50 vol.% and the content of third fibers - in the range of 1-20 vol.%, while the content of the first, second and third fibers are selected in such a way that the necessary mechanical characteristics of the composite tubular element in each direction correspond to mechanical stresses, action which the tubular element will be exposed during use. 14. Tubular element according to any one of claims 1 to 13, wherein the first and second fibers are grouped in the form of pre-compacted ribbons. 15. A tubular element according to any one of claims 1 to 14, wherein the first thermoplastic polymer is incorporated into the tubular structure along with fibers to form a polymer matrix. 16. A tubular element according to any one of claims 1 to 15, wherein the first thermoplastic polymer is subjected to melting to obtain a densified tubular structure. 17. A tubular element according to any one of claims 1 to 16, wherein the second polymer is a thermoset polymer. 18. A tubular element according to any one of claims 1 to 16, wherein the second polymer is a thermoplastic polymer. 19. A tubular element according to any one of claims 17 or 18, wherein the second polymer is introduced into the tubular structure simultaneously with the first thermoplastic polymer. 20. Tubular element according to claim 17 or 18, in which the second polymer is introduced into the tubular structure - 10 043152 after sealing. 21. The tubular element according to any one of claims 1 to 20, wherein the second polymer has a modulus value Young's modulus is less than the Young's modulus of the compacted tubular structure. 22. A tubular element according to any one of claims 1 to 21, wherein the second polymer has a higher deformability than the densified tubular structure. 23. A tubular element according to any one of claims 1 to 22, wherein the second polymer is an elastomer. 24. A tubular element according to any one of claims 1-23, wherein the composite tubular element is a riser. 25. A method for manufacturing a composite tubular element, including the steps: producing a two-dimensional tubular structure comprising first fibers oriented in the x direction relative to the longitudinal axis of the tubular element and second fibers oriented in the y direction relative to the longitudinal axis of the tubular element; introducing third fibers at least partially through the wall thickness of the tubular element to obtain a three-dimensional tubular structure; forming a polymer matrix composite consisting of a first thermoplastic polymer combining fibers of a three-dimensional tubular structure; and introducing a second polymer to fill the residual pores of the tubular structure to form a composite tubular.