Submarine pipeline anchor and double-layered submarine pipeline

Abstract

This invention provides a subsea pipeline anchor and a double-layer subsea pipeline, relating to the field of offshore oil and gas transportation technology. It addresses the shortcomings of existing subsea pipeline anchors, which are solid steel structures with high thermal conductivity. When used in double-layer subsea pipelines requiring high insulation performance, cold spots easily form at the anchor, leading to poor crude oil fluidity and increased risk of freezing during pipeline shutdowns. Furthermore, existing anchors are also heavy. The device comprises an inner ring, an outer ring, and a perforated structure. The outer ring is located outside the inner ring, and the outer ring and inner ring are connected by the perforated structure, which has internal cavities. This invention reduces the thermal conductivity of the subsea pipeline anchor while ensuring structural strength, improving insulation performance and enhancing the economy and safety of subsea pipelines, especially double-layer subsea pipelines transporting high-pour-point crude oil, during long-term operation.

Description

Technical Field

[0001] This invention relates to the field of offshore oil and gas transportation technology, and in particular to a subsea pipeline anchor and a double-layer subsea pipeline. Background Technology

[0002] Anchors are one of the key components of a double-layer subsea pipeline system. Their main functions include: connecting the inner and outer pipes and transmitting loads; converting the double-layer pipe into a single-layer pipe; and dividing the continuous annular space between the double-layer pipes into independent annular spaces.

[0003] Conventional subsea pipeline anchors are solid steel structures with high thermal conductivity. At the connection points of double-insulated pipe anchors, localized low temperatures easily form due to the low thermal resistance of the anchors themselves and the use of low-thermal-resistance insulation materials around them. When used in double-layer subsea pipelines with high insulation requirements, such as those transporting high-pour-point crude oil, cold spots can easily form at the anchors, leading to the following adverse effects: 1. Increased crude oil viscosity leads to decreased fluidity, increased transport resistance, and reduced economic viability; 2. If the crude oil temperature drops too quickly during a shutdown, the risk of solidification increases, and in severe cases, it may even block the subsea pipeline.

[0004] In existing technologies, there are methods to enhance thermal insulation performance by setting up an air extraction structure to achieve a vacuum state in the annular cavity of the double-layer pipeline. However, the anchor body is still a cylindrical structure, and the heat conduction area is not substantially reduced, resulting in limited improvement in thermal insulation performance. At the same time, there is also the problem of heavy anchor weight. Summary of the Invention

[0005] The purpose of this invention is to provide a subsea pipeline anchor and a double-layer subsea pipeline, to solve the problems of existing subsea pipeline anchors, which are solid steel structures with high thermal conductivity. When used in double-layer subsea pipelines with high insulation requirements, cold spots easily form at the anchor, leading to poor crude oil fluidity and increased risk of solidification during pipeline shutdown. Furthermore, existing anchors are also heavy. The various technical effects of the preferred solutions provided by this invention are detailed below.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides a submarine pipeline anchor, comprising an inner ring, an outer ring, and a perforated structure, wherein the outer ring is disposed outside the inner ring, the outer ring and the inner ring are connected by the perforated structure, and the perforated structure has a cavity inside.

[0007] Preferably, the outer ring and the inner ring are arranged coaxially.

[0008] Preferably, the thickness of the lattice structure is equal to the net gap between the outer ring and the inner ring.

[0009] Preferably, at least one axial end face of the outer ring is a first welding end face for welding connection with the outer tube of the subsea pipeline; At least one axial end face of the inner ring is a second welding end face for welding connection with the inner tube of the subsea pipeline.

[0010] Preferably, the first welding end face and the second welding end face are offset from each other in the axial direction of the anchor.

[0011] Preferably, the axial length of the outer ring is greater than the axial length of the inner ring.

[0012] Preferably, the cross-sectional shape of the lattice in the lattice structure is circular, elliptical, regular polygonal, or irregular.

[0013] Preferably, the lattice structure is a honeycomb structure, and the cross-sectional shape of the lattice is a regular hexagon.

[0014] Preferably, the apertures of each cell in the lattice structure are equal or unequal.

[0015] The present invention provides a double-layer subsea pipeline, comprising an inner pipe and an outer pipe, and an anchor disposed between the inner pipe and the outer pipe, wherein the anchor is the aforementioned subsea pipeline anchor.

[0016] The subsea pipeline anchor provided by this invention includes an inner ring, an outer ring, and a perforated structure. The outer ring is located outside the inner ring, and the outer ring and the inner ring are connected by the perforated structure. The perforated structure has a cavity inside, which overcomes the shortcomings of conventional subsea pipeline anchors, such as high thermal conductivity, poor insulation performance, and heavy weight. While ensuring structural strength, it reduces the thermal conductivity of the subsea pipeline anchor, improves insulation performance, and has the advantage of light weight. This improves the economy and safety of subsea pipelines, especially double-layer subsea pipelines transporting high-pour-point crude oil, during long-term operation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a first embodiment of the submarine pipeline anchor of the present invention; Figure 2 Is adopted Figure 1 The double-layered subsea pipeline is connected by subsea pipeline anchors. Figure 3 This is a schematic diagram of the structure of Embodiment 2 of the submarine pipeline anchor of the present invention; Figure 4 Is adopted Figure 3 The double-layered subsea pipeline is connected by subsea pipeline anchors.

[0019] In the diagram: 1. Outer ring; 2. Inner ring; 3. Hole grid structure; 4. Outer tube; 5. Inner tube; 6. Thermal insulation material; 7. Weld. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] Example 1 Figure 1 This is a structural schematic diagram of this embodiment, as shown below. Figure 1 As shown, the present invention provides a submarine pipeline anchor, including an inner ring 2, an outer ring 1, and a perforated structure 3. The outer ring 1 is disposed outside the inner ring 2, and the outer ring 1 and the inner ring 2 are connected by the perforated structure 3. The perforated structure 3 has a cavity inside.

[0022] By setting a hollow grid structure 3 between the inner ring 2 and the outer ring 1, the traditional solid steel connector is replaced, significantly reducing the metal's thermal conductivity cross-sectional area and cutting off the solid thermal bridge path. The closed cavity inside the grid structure 3 accommodates static air. Utilizing the characteristic that the thermal conductivity of air is much lower than that of steel, a thermal barrier is formed, effectively suppressing heat loss at the anchor. At the same time, while removing excess material to form cavities, the grid structure 3 maintains a continuous spatial configuration, significantly reducing the anchor's self-weight compared to a solid structure. Despite the significant weight reduction, it exhibits excellent specific strength and specific stiffness, meeting the application requirements.

[0023] As an optional implementation, the outer ring 1 and the inner ring 2 are arranged coaxially. This ensures that the annular gap between the outer ring 1 and the inner ring 2 is uniform in the circumferential direction, facilitating the uniform filling of the perforated structure 3 and avoiding insufficient support due to excessively large local gaps or assembly interference due to excessively small gaps. Furthermore, the coaxial arrangement facilitates processing and reduces manufacturing costs.

[0024] When in use, the coaxial structure ensures that the stress is symmetrically distributed in the circumferential direction when subjected to radial pressure and axial load transmitted from the inner and outer pipes of the submarine pipeline, avoiding the generation of eccentric bending moment and improving the load-bearing stability and fatigue resistance of the anchor.

[0025] As an optional implementation, the thickness of the perforated structure 3 is equal to the net gap between the outer ring 1 and the inner ring 2. This ensures that the perforated structure 3 is tightly connected to the outer ring 1 and the inner ring 2 in the radial direction, with no gaps, allowing the internal pressure load borne by the inner ring 2 to be effectively and continuously transferred to the outer ring 1 through the perforated structure 3, avoiding interruption of stress transmission. Simultaneously, the thickness of the perforated structure 3 being equal to the net gap restricts the radial deformation space of the perforated structure, preventing buckling or collapse of the perforated structure wall under high pressure, thus ensuring structural integrity in deep-sea high-pressure service environments. Furthermore, while ensuring connection strength, setting the thickness of the perforated structure 3 to be equal to the net gap between the outer ring 1 and the inner ring 2 allows the perforated structure to occupy the maximum volume within a limited radial space, thereby providing the maximum thermal insulation cross-sectional area.

[0026] It is understood that the lengths of the inner ring 2, outer ring 1, and perforated structure 3 in this embodiment can be adjusted according to usage requirements to meet different needs. Similarly, the diameter and wall thickness of the inner ring 2 and outer ring 1, as well as the shape and size of the perforations in the perforated structure 3, can also be set according to usage requirements.

[0027] As an optional implementation, at least one axial end face of the outer ring 1 is a first welding end face for welding connection with the outer tube 4 of the subsea pipeline; at least one axial end face of the inner ring 2 is a second welding end face for welding connection with the inner tube 5 of the subsea pipeline.

[0028] By setting welding end faces on the inner ring 2 and outer ring 1 respectively, and using anchors as intermediate connectors, independent welding connections between the inner pipe 5 and outer pipe 4 in the double-layer subsea pipeline are achieved, which also enables a reliable transition from a double-layer pipeline to a single-layer pipeline. Furthermore, the welding end faces ensure that the inner pipe 5 and inner ring 2, and the outer pipe 4 and outer ring 1 are connected as a complete metallic continuum, ensuring the airtightness of the pipeline's annular space and preventing seawater intrusion or leakage of the internal medium.

[0029] The first and second welding faces in this embodiment are the same as the fully automatic or semi-automatic welding processes commonly used in submarine pipeline laying. There is no need to change the welding equipment and operating procedures on the existing pipelaying vessel, which has good engineering applicability.

[0030] To ensure a more uniform stiffness distribution across all cross-sections of the anchor, preferably, in this embodiment, the first and second welding end faces are staggered along the axial direction of the anchor. This arrangement prevents stress concentration points from concentrating on the same vulnerable cross-section when subjected to alternating loads, such as vortex-induced vibration, significantly improving the overall fatigue life of the anchor. Simultaneously, the staggered weld placement facilitates weld inspection; for example, during radiographic or ultrasonic testing, it avoids interference between film or waveform, eliminates blind spots, and facilitates accurate assessment of weld quality.

[0031] By setting the axial length of the outer ring 1 to be greater than that of the inner ring 2, axial misalignment of the welded end faces is ensured. This structure, where the inner ring 2 is shorter and the outer ring 1 is longer, allows the outward extension of the outer ring to shield the weld seam of the inner ring, buffering the risk of external seawater and mechanical collisions during the laying process.

[0032] Figure 2 Is adopted Figure 1 A schematic diagram of the structure of a double-layer subsea pipeline connected by subsea pipeline anchors, as shown in the figure. Figure 2 As shown, in this embodiment, the two ends of the subsea pipeline anchor are respectively connected to double-layer pipes, that is, the two axial end faces of the outer ring 1 are the first welding end faces for welding to the outer pipe 4 of the subsea pipeline; the two axial end faces of the inner ring 2 are the second welding end faces for welding to the inner pipe 5 of the subsea pipeline.

[0033] As an optional implementation, the cross-sectional shape of the lattice in the lattice structure 3 can be circular, elliptical, regular polygonal, or irregular. In actual production and use, the cross-sectional shape of the lattice in the lattice structure 3 can be selected according to different usage requirements such as actual seabed depth and temperature difference.

[0034] In this embodiment, a honeycomb structure is selected, with the cross-sectional shape of the pores being regular hexagons. Under the same unit density and wall thickness, its out-of-plane compressive strength and in-plane shear strength are significantly higher than those of circular or rectangular pores, effectively resisting the pressure of deep-sea hydrostatic water. Furthermore, the honeycomb structure maintains geometric stability throughout its entire lifespan, and its closed hexagonal cavities can persistently retain static air, ensuring no degradation in thermal insulation performance over long-term service. Moreover, the regular hexagons can completely fill a planar space without gaps, resulting in a denser arrangement than circular pores for the same insulation effect, with less material waste and lower production costs.

[0035] Specifically, the apertures of the individual cells in the perforated structure can be equal or unequal. Based on the radial temperature gradient distribution of the anchor, where the temperature is higher near the inner tube and lower near the outer tube, unequal apertures can be used. For example, smaller apertures in the inner layer increase strength, while larger apertures in the outer layer increase insulation, achieving functional gradient. The arrangement of unequal apertures can break the convective vortex scale within the perforated cavity, more effectively suppressing air micro-circulation compared to uniform large apertures, further reducing the convective heat transfer coefficient.

[0036] Alternatively, smaller apertures can be used in stress concentration areas of the anchor, such as near the weld end, to enhance local structural strength, while larger apertures can be used in non-load-bearing areas to reduce weight, thus achieving fine control.

[0037] Understandably, the perforations in perforated structure 3 can also adopt different shapes depending on different usage needs, such as one part being circular and another part being regular hexagonal. Generally, for ease of production, perforations with the same structure are selected.

[0038] like Figure 2 As shown, during the laying of the subsea pipeline, the inner pipe of the double-layer subsea pipeline is first welded to the inner ring 2, and then the outer pipe of the double-layer subsea pipeline is welded to the outer ring 1. The space between the inner pipe 5 and the outer pipe 4 is filled with insulation material 6. After transportation begins, the interior of the subsea pipeline will be filled with oil and gas media. Compared with conventional subsea pipeline anchors, by adopting the perforated structure 3, the heat-conducting metal area between the inner ring 2 and the outer ring 1 is reduced, thus reducing heat loss. At the same time, the internal cavity of the perforated structure 3 is filled with air, which is a natural heat-insulating material with a thermal conductivity much lower than that of metal, further reducing heat loss and saving materials. It has the advantages of being lightweight, high-strength, and rigid, which significantly reduces the thermal conductivity of the overall structure and greatly improves the insulation performance.

[0039] Example 2 Figure 3 This is a structural schematic diagram of this embodiment, as shown below. Figure 3 As shown, unlike Embodiment 1, in this embodiment, one of the axial end faces of the outer ring 1 is a first welding end face for welding connection with the outer tube 4 of the subsea pipeline; and one of the axial end faces of the inner ring 2 is a second welding end face for welding connection with the inner tube 5 of the subsea pipeline.

[0040] Figure 4 Is adopted Figure 3 A schematic diagram of the structure of a double-layer subsea pipeline connected by subsea pipeline anchors, as shown in the figure. Figure 4 As shown, in this embodiment, the two ends of the subsea pipeline anchor are connected to a double-layer pipe and a single-layer pipe, respectively.

[0041] This subsea pipeline anchor overcomes the shortcomings of conventional subsea pipeline anchors, such as high thermal conductivity, poor insulation performance, and heavy weight. It reduces the thermal conductivity area and thermal conductivity, improves insulation performance, and has the advantages of light weight, high strength, and high rigidity. This enhances the economy and safety of subsea pipelines, especially double-layer subsea pipelines transporting high-pour-point crude oil, during long-term operation.

[0042] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A subsea pipeline anchor, characterized in that, It includes an inner ring, an outer ring, and a perforated grid structure, wherein the outer ring is disposed outside the inner ring, the outer ring and the inner ring are connected by the perforated grid structure, and the perforated grid structure has a cavity inside.

2. The subsea pipeline anchor according to claim 1, characterized in that: The outer ring and the inner ring are arranged coaxially.

3. The subsea pipeline anchor according to claim 1, characterized in that: The thickness of the lattice structure is equal to the net gap between the outer ring and the inner ring.

4. The subsea pipeline anchor according to any one of claims 1-3, characterized in that: At least one axial end face of the outer ring is a first welding end face for welding connection with the outer tube of the subsea pipeline; At least one axial end face of the inner ring is a second welding end face for welding connection with the inner tube of the subsea pipeline.

5. The subsea pipeline anchor according to claim 4, characterized in that: The first welding end face and the second welding end face are offset from each other in the axial direction of the anchor.

6. The subsea pipeline anchor according to claim 5, characterized in that: The axial length of the outer ring is greater than the axial length of the inner ring.

7. A subsea pipeline anchor according to any one of claims 1-3, characterized in that: The cross-sectional shape of the lattice in the lattice structure is circular, elliptical, regular polygonal, or irregular.

8. A subsea pipeline anchor according to claim 7, characterized in that: The lattice structure is a honeycomb structure, and the cross-sectional shape of the lattice is a regular hexagon.

9. A subsea pipeline anchor according to claim 8, characterized in that: The apertures of each cell in the lattice structure may be equal or unequal.

10. A double-layer subsea pipeline, comprising an inner pipe and an outer pipe, and an anchor disposed between the inner pipe and the outer pipe, characterized in that: The anchor is the subsea pipeline anchor as described in any one of claims 1-9.

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