Deep sea non-adhesive flexible riser

Abstract

The invention relates to a deep sea non-adhesive flexible vertical pipe which comprises a framework layer, a first sealing layer, a first isolation layer, a first compression-resistant layer, a second compression-resistant layer, a second isolation layer, a first tensile layer, a second tensile layer and a second sealing layer which are sequentially arranged from inside to outside. The relative slippage distance of two adjacent circles of steel belts of the first compression-resistant layer in the axial direction of the vertical pipe is L1, the relative slippage distance of two adjacent circles of steel belts of the second compression-resistant layer in the axial direction of the vertical pipe is L2, L1 is smaller than L2, the steel belt winding helix angle of the first compression-resistant layer is alpha 1, the steel belt winding helix angle of the second compression-resistant layer is alpha 2, and alpha 1 and alpha 2 are different; the winding direction of the steel belt of the first tensile layer is opposite to the winding direction of the steel belt of the second tensile layer. The internal and external pressure resistance of the flexible vertical pipe is improved, and meanwhile the flexible vertical pipe can cope with complex working conditions.

Description

Technical Field

[0001] This invention relates to the field of marine mining technology, and in particular to a deep-sea non-adhesive flexible riser. Background Technology

[0002] In the field of offshore oil and gas extraction technology, flexible risers, as the core transportation equipment connecting offshore extraction platforms and subsea wellheads, are widely used in oil and gas resource transportation operations. Among them, deep-sea non-bonded flexible risers have become the mainstream choice for oil and gas extraction in shallow and mid-deep sea areas due to their excellent flexibility and environmental adaptability.

[0003] However, as offshore oil and gas exploration and development gradually advances into ultra-deep-sea areas (water depths exceeding 1500 meters and transport pressures exceeding 50 MPa), existing flexible riser technologies are increasingly revealing numerous defects and shortcomings. Specifically, existing deep-sea non-bonded flexible risers typically employ single-layer spirally wound and interlocked irregularly shaped steel (Z-shaped or C-shaped steel) as a pressure-resistant armor structure to achieve pressure-bearing functionality. This technical solution can, to some extent, meet the oil and gas transport needs in shallow and mid-deep-sea areas (water depths less than 1500 meters). However, in ultra-deep-sea environments, where water depths exceed 1500 meters and transport pressures can exceed 50 MPa, coupled with complex conditions such as low temperatures and strong ocean currents, existing flexible risers struggle to withstand extreme internal and external pressures and complex conditions. This can easily lead to pipeline failures, resulting in safety hazards such as oil and gas leaks. Consequently, they are ill-suited to the oil and gas transport needs of ultra-deep-sea areas, severely hindering the advancement of ultra-deep-sea oil and gas exploration and development.

[0004] Improving the resistance of flexible risers to internal and external pressures while enabling them to cope with complex working conditions is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] Therefore, the present invention provides a deep-sea non-adhesive flexible riser, which improves the resistance of the flexible riser to internal and external pressure and enables it to cope with complex working conditions.

[0006] To solve the above-mentioned technical problems, the present invention provides a deep-sea non-adhesive flexible riser, comprising: A skeleton layer is used to resist radial pressure; The first sealing layer is a sealing tube extruded and formed on the outside of the skeleton layer, used to transmit the medium inside; The first isolation layer is a low-friction coefficient material disposed on the outside of the first sealing layer; The first pressure-resistant layer is a steel strip spirally wound around the outside of the first isolation layer. The two adjacent turns of the steel strip in the first pressure-resistant layer are interlocked to resist radial pressure. The second compressive layer is a steel strip spirally wound around the outside of the first compressive layer. The steel strips at adjacent ends of the second compressive layer are interlocked to resist radial pressure. The second isolation layer is a low-friction coefficient material disposed on the outside of the second compressive layer; The first tensile layer is a steel strip spirally wound around the outside of the second insulating layer to resist axial tensile force; The second tensile layer is a steel strip spirally wound around the outside of the first tensile layer to resist axial tensile force; The second sealing layer is a sealing tube extruded and formed on the outside of the second tensile layer, used to isolate the external medium; The winding direction of the steel strip in the first pressure-resistant layer is the same as that in the second pressure-resistant layer. The relative sliding distance between two adjacent turns of the steel strip in the first pressure-resistant layer along the axial direction of the riser is L1, and the relative sliding distance between two adjacent turns of the steel strip in the second pressure-resistant layer along the axial direction of the riser is L2, where L1 is less than L2. The spiral angle of the steel strip winding in the first pressure-resistant layer is α1, and the spiral angle of the steel strip winding in the second pressure-resistant layer is α2, where α1 and α2 are different. The winding direction of the steel strip in the first tensile layer is opposite to that in the second tensile layer.

[0007] In one embodiment of the present invention, L1 is 2-3 mm and L2 is 5-8 mm.

[0008] In one embodiment of the present invention, the difference between α1 and α2 is 10°-20°.

[0009] In one embodiment of the present invention, α1 is 50°-60° and α2 is 30°-45°.

[0010] In one embodiment of the present invention, the steel strips of the first compressive layer and the second compressive layer are both Z-shaped steels, wherein the height of the cross section of the Z-shaped steel is h and the width is w, where h is 10-20 mm and w is 8-15 mm.

[0011] In one embodiment of the present invention, the steel strips of the first compressive layer and the second compressive layer are both high-strength alloy steels with a yield strength of not less than 600 MPa and a tensile strength of not less than 700 MPa.

[0012] In one embodiment of the present invention, the steel strips of the first tensile layer and the second tensile layer are both flat steel, and the thickness of the steel strips of the first tensile layer and the second tensile layer is 3-15mm.

[0013] In one embodiment of the present invention, the steel strips of the first tensile layer and the second tensile layer are both high-strength alloy steels with a yield strength of not less than 800 MPa and a tensile strength of not less than 900 MPa.

[0014] In one embodiment of the present invention, the friction coefficient of the first isolation layer and the second isolation layer is not greater than 0.15.

[0015] In one embodiment of the present invention, the materials of the first isolation layer and the second isolation layer are polytetrafluoroethylene or ultra-high molecular weight polyethylene.

[0016] Compared with the prior art, the above-mentioned technical solution of the present invention has the following advantages: The deep-sea non-adhesive flexible riser of the present invention, firstly, includes a first pressure-resistant layer and a second pressure-resistant layer. Adjacent steel strips in both the first and second pressure-resistant layers can be interlocked, enabling the pipeline to effectively resist internal and external pressures under ultra-high pressure environments, reducing the risk of deformation and breakage; secondly, the relative sliding distance between adjacent steel strips in the second pressure-resistant layer along the riser axial direction is greater than that in the first pressure-resistant layer, and the deformation capacity of the second pressure-resistant layer is superior to that of the first pressure-resistant layer, making the flexible riser more flexible. The normal deformation and stress distribution of the riser during bending extend the pipeline's long-term service life. Furthermore, the different spiral angles of the steel strip winding in the first and second pressure-resistant layers of the flexible riser create an "interlaced coverage" effect, allowing the steel strips in the second layer to fill the gaps between the steel strips in the first layer, ultimately improving the overall pressure resistance, sealing, and structural stability of the flexible riser. In addition, the flexible riser includes a first and second isolation layer, reducing frictional resistance between layers and allowing the pipeline to maintain good flexibility even under ultra-high pressure environments, facilitating installation and use. The deep-sea non-adhesive flexible riser of this invention significantly improves its resistance to internal and external pressures, enabling it to cope with complex working conditions. Attached Figure Description

[0017] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0018] Figure 1 This is a schematic diagram of a partial peeling of the deep-sea non-adhesive flexible riser in this invention; Figure 2 This is a partial longitudinal section diagram of the deep-sea non-adhesive flexible riser in this invention.

[0019] Explanation of reference numerals in the accompanying drawings: 1. Skeleton layer; 2. First sealing layer; 3. First compressive layer; 4. Second compressive layer; 5. First tensile layer; 6. Second tensile layer; 7. Second sealing layer. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0021] See Figure 1 and Figure 2 As shown, this invention provides an embodiment of a deep-sea non-adhesive flexible riser.

[0022] The aforementioned deep-sea non-bonded flexible risers include: Skeleton layer 1, used to resist radial pressure; The first sealing layer 2 is a sealing tube extruded and formed on the outside of the skeleton layer 1, used to transmit the medium inside. The first isolation layer (not shown in the figure) is a low friction coefficient material disposed on the outside of the first sealing layer 2. The first pressure-resistant layer 3 is a steel strip spirally wound around the outside of the first isolation layer. The two adjacent turns of the steel strip in the first pressure-resistant layer 3 are interlocked to resist radial pressure. The second pressure-resistant layer 4 is a steel strip spirally wound around the outside of the first pressure-resistant layer 3. The steel strips at adjacent ends of the second pressure-resistant layer 4 are interlocked to resist radial pressure. The second isolation layer (not shown in the figure) is a low friction coefficient material disposed on the outside of the second compressive layer 4. The first tensile layer 5 is a steel strip spirally wound around the outside of the second isolation layer to resist axial tensile force; The second tensile layer 6 is a steel strip spirally wound around the outside of the first tensile layer 5, used to resist axial tensile force; The second sealing layer 7 is a sealing tube extruded and formed on the outside of the second tensile layer 6, used to isolate the external medium; The winding direction of the steel strip in the first compressive layer 3 is the same as that in the second compressive layer 4. The relative sliding distance between two adjacent turns of the steel strip in the first compressive layer 3 along the axial direction of the riser is L1, and the relative sliding distance between two adjacent turns of the steel strip in the second compressive layer 4 along the axial direction of the riser is L2. L1 is less than L2. The spiral angle of the steel strip winding in the first compressive layer 3 is α1, and the spiral angle of the steel strip winding in the second compressive layer 4 is α2. α1 and α2 are set differently. The winding directions of the steel strips in the first tensile layer 5 and the second tensile layer 6 are opposite.

[0023] Specifically, the skeleton layer 1 is the inner basic structure of the deep-sea non-bonded flexible riser. Its core function is to resist radial pressure, provide radial support for the overall structure of the riser, and ensure the stability of the pipeline foundation.

[0024] The first sealing layer 2 and the second sealing layer 7 are both extruded sealing tubes. The first sealing layer 2 is used to ensure the stable transmission of the internal oil and gas medium, and the second sealing layer 7 is used to isolate the intrusion of external media such as seawater and prevent the internal structure from being corroded.

[0025] The first pressure-resistant layer 3 and the second pressure-resistant layer 4 are structural layers that resist radial pressure (internal pressure and external pressure). Both are interlocking steel strips wound in a spiral. Two adjacent steel strips can interlock to form an "interlocking" structure, which improves the pressure-bearing capacity and enables the pipeline to effectively resist internal and external pressure under ultra-high pressure environment, reducing the risk of deformation and breakage.

[0026] The axial relative sliding distance, also known as the bending clearance, refers to the maximum distance that two adjacent steel strips can move relative to each other along the axial direction of the riser. A larger axial relative sliding distance makes bending easier, while a smaller distance makes bending more difficult, resulting in stronger structural rigidity but also greater susceptibility to fatigue damage due to stress concentration during bending. When a flexible riser bends, if the bending performance of the second pressure-resistant layer 4 is less than that of the first pressure-resistant layer 3, the second pressure-resistant layer 4 cannot effectively release the stress generated by bending and swaying, and may even damage the first pressure-resistant layer 3. Setting the relative sliding distance between adjacent steel strips of the first pressure-resistant layer 3 along the axial direction of the riser to be greater than that of adjacent steel strips of the second pressure-resistant layer 4 ensures normal deformation and stress distribution during the bending process of the flexible riser, thereby extending the long-term service life of the pipeline.

[0027] Regarding the spiral angle, it refers to the angle between the steel strip and the riser axis when the steel strip is spirally wound. Whether it's the first pressure-resistant layer 3 or the second pressure-resistant layer 4, when the steel strip is spirally wound, there will inevitably be a small gap between adjacent turns of steel strip (determined by the winding process, steel strip width, and spiral angle). For existing single-layer pressure-resistant layers, these gaps become "weak points in pressure resistance"—under extreme pressure in the ultra-deep sea, pressure tends to concentrate at the gaps, potentially leading to gap widening or even causing failures such as localized pipe subsidence and media leakage. In this invention, the first pressure-resistant layer 3 and the second pressure-resistant layer 4 have the same winding direction but different spiral angles. This design allows the winding trajectories of the two steel strips to form a "staggered" arrangement. When the trajectories intersect, the steel strip of the second pressure-resistant layer precisely covers the gap between adjacent steel strips of the first pressure-resistant layer, forming a "no dead angle" double-layer surround structure, improving the overall pressure resistance, sealing performance, and structural stability of the flexible riser.

[0028] The first and second isolation layers are made of materials with low coefficient of friction. Their core function is to reduce frictional losses between adjacent structural layers and ensure smooth relative movement between the layers.

[0029] The first tensile layer 5 and the second tensile layer 6 are structural layers that resist axial tensile forces, both consisting of spirally wound steel strips. They are used to counteract the axial tensile forces on the riser in its suspended state in deep sea, preventing the pipeline from stretching, deforming, or breaking due to excessive axial stress. Specifically, deep-sea risers are suspended installations and must withstand the enormous axial tensile forces generated by their own weight, the weight of the internal medium, and additional operational loads (such as platform swaying and ocean current drag) over long periods. The double-layered, counter-winding tensile layers form a "balanced load-bearing system." If the two tensile layers are wound in the same direction, the tensile force will concentrate on the steel strip in one direction, easily leading to overload and breakage of a single layer. However, with counter-winding, the axial tensile force can be evenly distributed to both layers of steel strips. The combined force of the two layers increases the overall tensile limit, preventing the failure of a single tensile layer due to excessive local load.

[0030] Through the above technical solution, firstly, the flexible riser includes a first pressure-resistant layer and a second pressure-resistant layer. Adjacent steel bands in both the first and second pressure-resistant layers can interlock, enabling the pipeline to effectively resist internal and external pressures under ultra-high pressure environments, reducing the risk of deformation and breakage. Secondly, the relative sliding distance between adjacent steel bands in the second pressure-resistant layer along the riser's axial direction is greater than that in the first pressure-resistant layer. The deformation capacity of the second pressure-resistant layer is superior to that of the first pressure-resistant layer, ensuring that the flexible riser undergoes normal deformation and stress reduction during bending. The flexible riser features a force distribution system, which extends the long-term service life of the pipeline. Furthermore, the spiral angles of the steel strips wound in the first and second pressure-resistant layers are different, creating an "interlaced coverage" effect. This allows the steel strips in the second pressure-resistant layer to fill the gaps between the steel strips in the first pressure-resistant layer, ultimately improving the overall pressure resistance, sealing performance, and structural stability of the flexible riser. In addition, the flexible riser includes a first and second isolation layer, reducing frictional resistance between layers and ensuring the pipeline maintains good flexibility even under ultra-high pressure conditions, facilitating installation and use.

[0031] In this embodiment, L1 is 2-3 mm and L2 is 5-8 mm.

[0032] Specifically, regarding the range of L1, if L1 < 2 mm, the slippage allowance of the steel strips in the first pressure-resistant layer is too small, which will lead to excessive compressive stress between the steel strips when the riser bends and swings, easily causing fatigue fracture in the long term. If L1 > 3 mm, it will destroy the integrity of the inner first pressure-resistant layer, making it impossible to form a stable pressure dispersion system, resulting in a decrease in radial pressure bearing capacity. A range of 2-3 mm can provide basic flexibility for the riser (adapting to attitude adjustments in deep-sea operations) while ensuring the close cooperation of the inner first pressure-resistant layer 3, ensuring uniform transmission of pressure load. L1 can be 2 mm, 2.5 mm, or 3 mm.

[0033] Regarding the range of L2, if L2 < 5 mm, the slippage margin of the second pressure-resistant layer 4 is insufficient, which will limit the overall bending capacity of the riser, resulting in excessive structural rigidity and susceptibility to damage due to stress concentration in the dynamic environment of deep sea. If L2 > 8 mm, excessive slippage between the steel strips of the second pressure-resistant layer 4 will reduce the synergy of the two pressure-resistant layers, and the outer second pressure-resistant layer 4 will not be able to effectively assist the inner first pressure-resistant layer 3 in bearing pressure. A range of 5-8 mm can meet the requirements for adapting to large deformations of the outer layer. L2 can be 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, or 8 mm.

[0034] With the above technical solution, L1 is 2-3 mm and L2 is 5-8 mm, which can ensure that both the first compressive layer 3 and the second compressive layer 4 can be bent, and can also adapt to the large deformation requirements of the second compressive layer 4, thereby improving the overall flexibility.

[0035] In this embodiment, the difference between α1 and α2 is 10°-20°.

[0036] Specifically, the difference between α1 and α2 determines the coverage effect of the gap between the steel strips in the first compressive layer 3. If the difference is too small (<10°), the winding trajectories of the two steel strips are close, and the second compressive layer 4 cannot fully fill the natural gaps in the first compressive layer 3, leaving weak points in the pressure-bearing structure and causing pressure concentration. If the difference is too large (>20°), the trajectories of the two steel strips will overlap excessively, easily causing mutual compression and interference, which will damage the integrity of the interlayer structure. Only by controlling the difference within a reasonable range of 10°-20° can the second compressive layer 4 accurately cover the gaps in the first compressive layer 3, forming a double-layer pressure-bearing system without dead angles.

[0037] Through the above technical solution, the difference between α1 and α2 is controlled within 10°-20°, which can avoid "insufficient coverage overlap" (gap still exists) caused by too small an angle difference, and also avoid "mutual squeezing of steel strips" (damage to interlayer structure) caused by too large an angle difference. This ensures the coverage effect while guaranteeing the synergistic stability of the first and second compressive layers.

[0038] In this embodiment, α1 is 50°-60°, α2 is 30°-45°, and the difference between α1 and α2 is 10°-20°.

[0039] Specifically, α1 is 50°-60°, making the steel strip winding of the first compressive layer 3 closer to "lateral wrapping," and the extension direction of the gap between adjacent steel strips more radial. Specifically, it can be set to 50°, 51°, 52°, 53°, 54°, 55°, 56°, 57°, 58°, 59°, or 60°. α2 is 30°-45°, making the steel strip winding of the second compressive layer 4 closer to "longitudinal extension," and the extension direction of the gap between adjacent steel strips more axial. Specifically, it can be set to 30°, 31°, 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39°, 40°, 41°, 42°, 43°, 44°, or 45°. When the two trajectories intersect, the steel strip of the second compressive layer 4 will precisely cover the gap between adjacent steel strips of the first compressive layer 3. This "outer layer covering the inner layer gap" design improves the uniformity of pressure resistance by eliminating weak points in the single-layer pressure resistance, allowing extreme pressures (over 50MPa) in the ultra-deep sea to be evenly transmitted to both pressure resistance layers, avoiding structural failure caused by local pressure concentration. On the other hand, it enhances sealing protection: filling the gaps reduces the risk of seawater, oil, and gas media intruding into the inner structure through the gaps. Combined with the isolation and sealing layers, it further improves the riser's corrosion and leakage resistance. Moreover, it strengthens the overall structural integrity; the staggered coverage of the two steel strips creates a "mesh-like integrated structure" rather than two independent layers, improving the riser's resistance to deformation under complex conditions such as strong ocean current disturbances and bending.

[0040] The above technical solution, with α1 being 50°-60° and α2 being 30°-45°, can not only improve the uniformity of compressive strength, but also enhance sealing protection and strengthen the overall structural integrity.

[0041] In this embodiment, the steel strips of the first compressive layer 3 and the second compressive layer 4 are both Z-shaped steels. The height of the cross section of the Z-shaped steel is h, and the width is w, where h is 10-20mm and w is 8-15mm.

[0042] Specifically, Z-shaped steel strip refers to steel strip with a Z-shaped cross-section. The hook of the Z-shaped steel strip can precisely interlock with the groove of the adjacent steel strip to form a stable interlocking structure, which can effectively transmit radial pressure and prevent the double-layer pressure-resistant layer from separating or misaligning under extreme pressure.

[0043] The cross-sectional area h of the Z-shaped steel strip is set to 10-20mm to provide sufficient radial load-bearing cross-section, ensuring that it does not undergo plastic deformation under extreme pressure exceeding 50MPa in ultra-deep sea conditions. If h < 10mm, the radial stiffness of the steel strip is insufficient, making it susceptible to deformation under pressure. If h > 20mm, the weight of the steel strip is too large, increasing the overall load on the riser and potentially causing spatial interference with adjacent isolation layers and tensile layers, affecting the smoothness of interlayer movement. Specifically, h can be 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, or 20mm.

[0044] The cross-section w of the Z-shaped steel strip is set to 8-15mm to allow the hooks of adjacent Z-shaped steel strips to form a sufficient interlocking depth with the grooves, improving the shear resistance of the interlocking structure and preventing interlocking failure under strong ocean current disturbances. If w < 8mm, the interlocking depth is insufficient, and the interlock is prone to detachment. If w > 15mm, the lateral coverage of the steel strip is too large, which will lead to excessive overlap of adjacent steel strips during spiral winding, increasing bending resistance and reducing the flexibility of the riser. Specifically, w can be 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, or 15mm.

[0045] The above technical solution uses Z-shaped steel strips with the same cross-sectional dimensions for the first and second pressure-resistant layers, which simplifies the production process and reduces procurement and processing costs. At the same time, setting the size of the Z-shaped steel strips within a certain range takes into account both the pressure-bearing capacity and flexibility of the flexible riser.

[0046] In this embodiment, the steel strips of the first compressive layer 3 and the second compressive layer 4 are both high-strength alloy steels with a yield strength of not less than 600 MPa and a tensile strength of not less than 700 MPa.

[0047] Specifically, a yield strength ≥ 600 MPa ensures that the steel strip will not undergo plastic deformation (permanent deformation) under extreme pressure. If the yield strength is below 600 MPa, the steel strip is prone to local indentation and bending under pressure, compressing the interlocking structure and causing the pressure-resistant layer to fail. A yield strength above 600 MPa allows the steel strip to maintain its original shape and stably bear radial pressure loads. Strong ocean currents in ultra-deep seas can cause the riser to oscillate, causing the pressure-resistant layer steel strip to bear not only radial pressure but also composite stresses such as interlayer shear force and axial tensile force. A tensile strength above 700 MPa can prevent the steel strip from breaking due to excessive composite stress, ensuring that the double-layer interlocking structure does not disintegrate.

[0048] Through the above technical solution, the yield strength of the steel strip of the first compressive layer and the steel strip of the second compressive layer is not less than 600MPa and the tensile strength is not less than 700MPa, so that the first compressive layer and the second compressive layer have sufficient mechanical strength.

[0049] In this embodiment, the steel strip of the first tensile layer 5 and the steel strip of the second tensile layer 6 are both flat steel, and the thickness of the steel strip of the first tensile layer 5 and the steel strip of the second tensile layer 6 is 3-15mm.

[0050] Specifically, the core function of the first tensile layer 5 and the second tensile layer 6 is to bear the axial tensile force (its own weight + the weight of the medium + dynamic load) in the suspended state of the deep-sea riser. On the one hand, the flat steel surface is flat, and when spirally wound, it can form a tight fit with the inner second isolation layer and the outer second sealing layer, avoiding the gap caused by irregular cross-section, reducing interlayer shear force, and ensuring structural stability. At the same time, the flat surface can reduce wear on adjacent isolation layers and extend the service life of the interlayer structure. On the other hand, the flat steel has no complex hooks or groove structures, and when wound in reverse, it will not have the "interference and jamming" problem like that of Z-shaped steel strips. It can flexibly adjust the winding angle to ensure that the two tensile layers are evenly distributed and the force is balanced, giving full play to the advantage of "reverse counteracting torsional stress".

[0051] The minimum thickness of the flat steel is 3mm to ensure the tensile strength of the foundation. The maximum thickness of the flat steel is 15mm to control the overall weight and ensure flexibility. If the thickness is greater than 15mm, the weight of the tensile layer will increase significantly, leading to an increase in the overall load on the riser. This will not only increase the load-bearing pressure on the top platform but also exacerbate its own axial tensile force, potentially causing overloads in other structures such as the pressure-resistant layer and sealing layer. At the same time, excessively thick flat steel will increase the rigidity of the riser but reduce its flexibility in bending and swaying, making it unable to adapt to the attitude adjustment requirements of complex dynamic working conditions in the deep sea.

[0052] Through the above technical solution, the first tensile layer and the second tensile layer are made of flat steel with a thickness of 3-15mm, which improves the tensile properties of the first tensile layer and the second tensile layer.

[0053] In this embodiment, the steel strip of the first tensile layer 5 and the steel strip of the second tensile layer 6 are both high-strength alloy steels with a yield strength of not less than 800 MPa and a tensile strength of not less than 900 MPa.

[0054] Specifically, a yield strength ≥ 800 MPa ensures that the tensile layer does not undergo plastic deformation (permanent deformation) under long-term rated axial tensile force. If the yield strength is below 800 MPa, the flat steel is prone to tensile deformation under continuous tension, leading to relaxation of the tensile layer and subsequent overall sinking and structural misalignment of the riser. A yield strength of ≥ 800 MPa allows the flat steel to maintain its original shape, stably bearing axial loads and ensuring the stability of the riser suspension. A tensile strength ≥ 900 MPa is required to withstand extreme impact loads and prevent fracture failure. Scenarios such as towing by strong ocean currents in ultra-deep seas and emergency adjustments to the platform's attitude will generate instantaneous impact tensile forces. A tensile strength of ≥ 900 MPa allows the flat steel to withstand such instantaneous overloads and avoid direct breakage. If the tensile strength is insufficient, fracture is likely to occur under impact loads, leading to the disintegration of the entire riser structure and causing serious safety accidents.

[0055] Through the above technical solution, the yield strength of the steel strip of the first tensile layer and the steel strip of the second tensile layer is not less than 800MPa and the tensile strength is not less than 900MPa, so that the first tensile layer and the second tensile layer have sufficient mechanical strength. In this embodiment, the friction coefficient of the first and second isolation layers is not greater than 0.15.

[0056] Specifically, the core functions of the first and second isolation layers are to reduce frictional losses between adjacent structural layers and ensure smooth relative movement. If the coefficient of friction is greater than 0.15, a large sliding friction force will be generated during the relative movement between the layers. Long-term repeated friction will lead to wear on the surfaces of adjacent structural layers (such as the first sealing layer and the first pressure-resistant layer on both sides of the first isolation layer, and the second pressure-resistant layer and the first tensile layer on both sides of the second isolation layer). A coefficient of friction ≤ 0.15 can significantly reduce the sliding friction force, reduce the wear rate of the sealing layer and the alloy steel strip surface, and avoid sealing layer rupture (causing media leakage) and alloy steel strip corrosion (reducing compressive / tensile strength) due to isolation layer failure, thereby extending the overall service life of the riser.

[0057] The above technical solution sets the friction coefficient of the first and second isolation layers to no more than 0.15, ensuring the flexibility of the flexible riser.

[0058] In this embodiment, the materials of the first and second isolation layers are polytetrafluoroethylene or ultra-high molecular weight polyethylene.

[0059] Specifically, the first and second isolation layers are made of polytetrafluoroethylene (PTFE) or ultra-high molecular weight polyethylene (UHMWPE). These two materials are the optimal choice for low friction and resistance to extreme environments. In addition to their low coefficient of friction, both possess excellent low-temperature resistance (withstanding temperatures as low as 0-10℃ in the ultra-deep sea) and corrosion resistance (resisting the erosion of chloride ions and sulfides in seawater and oil and gas media). They will not age or crack due to the extreme environment of the deep sea and can maintain stable low-friction performance over a long period of time. Specifically, the first and second isolation layers mentioned above are spiral wound layers or extruded pipes.

[0060] Through the above technical solution, the materials of the first and second isolation layers are polytetrafluoroethylene or ultra-high molecular weight polyethylene, ensuring the flexibility and service life of the flexible riser.

[0061] In this embodiment, the second sealing layer is made of a polymer material with good weather resistance and wear resistance.

[0062] Specifically, the ultra-deep sea environment presents complex climatic / environmental factors such as low temperatures (0-10℃), high pressure (pressures exceeding 150MPa at depths exceeding 1500 meters), and strong corrosion (seawater containing high concentrations of chloride ions and residual media from oil and gas leaks). To adapt to this environment, polymers with excellent weather resistance (such as modified polyolefins and fluororubber) can maintain long-term chemical stability without aging, cracking, softening, or other performance degradation, thus preventing damage to the sealing barrier due to material failure.

[0063] The following are the specific dimensions of the flexible riser in this embodiment: Thickness of each layer: First sealing layer: 10mm; First isolation layer: 2mm; First compressive strength layer: 15mm; Second compressive strength layer: 15mm; Second isolation layer: 2mm; First tensile strength layer and second tensile strength layer: 10mm; Second sealing layer: 5mm.

[0064] The steel strips of the first and second compressive layers have a cross-sectional height h=15mm and a cross-sectional width w=12mm. The spiral angle of the steel strip winding of the first compressive layer is α1=55° and the spiral angle of the steel strip winding of the second compressive layer is α2=45°. The axial relative displacement distance between two adjacent turns of the steel strip in the first compressive layer is 2.5mm and the axial relative displacement distance between two adjacent turns of the steel strip in the second compressive layer is 6mm.

[0065] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A deep-sea non-adhesive flexible riser, characterized in that, include: A skeleton layer is used to resist radial pressure; The first sealing layer is a sealing tube extruded and formed on the outside of the skeleton layer, used to transmit the medium inside; The first isolation layer is a low-friction coefficient material disposed on the outside of the first sealing layer; The first pressure-resistant layer is a steel strip spirally wound around the outside of the first isolation layer. The two adjacent turns of the steel strip in the first pressure-resistant layer are interlocked to resist radial pressure. The second compressive layer is a steel strip spirally wound around the outside of the first compressive layer. The steel strips at adjacent ends of the second compressive layer are interlocked to resist radial pressure. The second isolation layer is a low-friction coefficient material disposed on the outside of the second compressive layer; The first tensile layer is a steel strip spirally wound around the outside of the second insulating layer to resist axial tensile force; The second tensile layer is a steel strip spirally wound around the outside of the first tensile layer to resist axial tensile force; The second sealing layer is a sealing tube extruded and formed on the outside of the second tensile layer, used to isolate the external medium; The winding direction of the steel strip in the first pressure-resistant layer is the same as that in the second pressure-resistant layer. The relative sliding distance between two adjacent turns of the steel strip in the first pressure-resistant layer along the axial direction of the riser is L1, and the relative sliding distance between two adjacent turns of the steel strip in the second pressure-resistant layer along the axial direction of the riser is L2, where L1 is less than L2. The spiral angle of the steel strip winding in the first pressure-resistant layer is α1, and the spiral angle of the steel strip winding in the second pressure-resistant layer is α2, where α1 and α2 are different. The winding direction of the steel strip in the first tensile layer is opposite to that in the second tensile layer.

2. The deep-sea non-adhesive flexible riser according to claim 1, characterized in that, L1 is 2-3 mm, and L2 is 5-8 mm.

3. The deep-sea non-adhesive flexible riser according to claim 1, characterized in that, The difference between α1 and α2 is 10°-20°.

4. The deep-sea non-adhesive flexible riser according to claim 1, characterized in that, α1 is 50°-60°, and α2 is 30°-45°.

5. The deep-sea non-adhesive flexible riser according to claim 1, characterized in that, Both the steel strip of the first compressive layer and the steel strip of the second compressive layer are Z-shaped steels. The height of the cross section of the Z-shaped steel is h, and the width is w, where h is 10-20mm and w is 8-15mm.

6. The deep-sea non-adhesive flexible riser according to claim 1, characterized in that, Both the steel strips of the first and second compressive layers are high-strength alloy steels with a yield strength of not less than 600 MPa and a tensile strength of not less than 700 MPa.

7. The deep-sea non-adhesive flexible riser according to claim 1, characterized in that, Both the steel strip of the first tensile layer and the steel strip of the second tensile layer are flat steel, and the thickness of the steel strip of the first tensile layer and the steel strip of the second tensile layer is 3-15mm.

8. The deep-sea non-adhesive flexible riser according to claim 1, characterized in that, Both the steel strip of the first tensile layer and the steel strip of the second tensile layer are high-strength alloy steels with a yield strength of not less than 800 MPa and a tensile strength of not less than 900 MPa.

9. The deep-sea non-adhesive flexible riser according to claim 1, characterized in that, The coefficient of friction of the first and second isolation layers is no greater than 0.

15.

10. The deep-sea non-adhesive flexible riser according to claim 1, characterized in that, The materials of the first and second isolation layers are polytetrafluoroethylene or ultra-high molecular weight polyethylene.

Images