CN116368062A

CN116368062A - Improved floating offshore structure

Info

Publication number: CN116368062A
Application number: CN202180074232.XA
Authority: CN
Inventors: 伊兹莉娜·伯特·M伊克巴尔; 法齐·奥马尔·巴谢尔B奥斯曼; 克里斯蒂安·哈里亚迪·吉桑; 扎哈里·A·拉扎克; 李秀英; 弗兰克·亚当; 弗兰克·达尔豪斯; 哈毕勒·约亨·格罗斯曼; 卡斯滕·亨赫奥弗; 迈克尔·拜尔
Original assignee: Petroliam Nasional Bhd Petronas
Current assignee: Petroliam Nasional Bhd Petronas
Priority date: 2020-10-01
Filing date: 2021-10-01
Publication date: 2023-06-30
Also published as: KR20230104144A; US20230415855A1; JP2023545026A; WO2022071793A1; EP4222047A1

Abstract

A mooring connector comprising: a linkage comprising a plurality of hinge components, adjacent hinge components of the linkage being engaged with a pin joint and arranged to pivot about a first axis at the pin joint; wherein at least one pin joint within the linkage is arranged to pivot about a second axis, the second axis being orthogonal to the first axis.

Description

Improved floating offshore structure

Technical Field

The present invention relates to supporting offshore installations, including floating offshore structures such as wind turbines and offshore oil and gas exploration and production.

Background

Installation of offshore structures, in particular tension leg platforms, is a highly capital intensive structure and also involves high operational costs.

It is therefore beneficial to increase the effectiveness of current designs of support systems for such structures.

Disclosure of Invention

In a first aspect, the present invention provides a mooring connection comprising: a linkage comprising a plurality of hinge components, adjacent hinge components of the linkage being engaged with a pin joint and arranged to pivot about a first axis at the pin joint; wherein at least one pin joint within the linkage is arranged to pivot about a second axis, the second axis being orthogonal to the first axis.

In a second aspect, the present invention provides a gravity anchor for an offshore structure, the gravity anchor comprising: a base for contacting the seabed; an interference member arranged to protrude from the base and arranged to be embedded in the seabed.

In a third aspect, the present invention provides a substructure for an offshore structure, the substructure comprising: an inlet and an outlet, both of which are positioned above the horizontal plane; the inlet and outlet being in fluid communication via an air flow path; the air flow path having at least a portion below a horizontal plane; wherein the air flow path is in thermal communication with the water and is arranged to transfer heat from the air flow to the water.

It should be appreciated that while each aspect may be used with a floating platform, each aspect may equally be used alone. Accordingly, a designer of a floating platform may improve the construction and/or operation of the floating platform by using any one or a combination of the various aspects described above, and achieve results that are superior to platforms according to the prior art. Thus, the use of any of these aspects of the invention is not dependent on the use of any other aspect.

Drawings

The invention will be further described with reference to the accompanying drawings, which illustrate possible arrangements of the invention. Other arrangements of the invention are possible and, thus, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

FIGS. 1A and 1B are isometric views of a connector according to one embodiment of the invention;

FIGS. 2A and 2B are isometric views of an adapter plate according to various embodiments of the present invention;

figures 3A-3C are isometric views of a tension leg platform connector according to another embodiment of the invention;

FIGS. 4A and 4B are various views of a gravity anchor for an offshore structure according to one embodiment of the invention;

FIGS. 5A and 5B are various views of a gravity anchor for an offshore structure according to another embodiment of the present invention;

FIG. 6 is an isometric view of a gravity anchor for an offshore structure according to another embodiment of the invention;

FIG. 7 is a schematic view of a tower base of an offshore wind turbine system according to one embodiment of the invention.

Detailed Description

For floating offshore structures, the fixed connection of the mooring lines to the hull is typically accomplished via a gusset or equivalent. For such a connection, the eye plate may represent a weak link where the crack may propagate. The eye plate connection may also be weak in out-of-plane moments. Thus, for long-term high-strength load-cycling applications with random loading (and thus cyclic loading also on their weaker axes), eye-plate connections may not be suitable.

Fig. 1A and 1B show an alternative arrangement with mooring line securing

connections

5, 65 for connection to a tension leg platform 10 (TLP). The connector 5 comprises a linkage having a plurality of hinge parts, each hinge part being hingedly connected to an adjacent part by a pin joint. The hinge component of the connector 5 of fig. 1A comprises a pair of adapter plates 20, each adapter plate 20 being connected at a first end 35 to a mooring line 15 and at an opposite second end to a TLP interface 25.

As shown in fig. 2A and 2B, the adapter plate 20 may be short 105 or long 110, and may be manufactured to any prescribed length. Each adapter plate includes parallel plates with pin joints at each end for connection with adjacent hinge members within the linkage.

In accordance with the present invention, the TLP interface 25 is engaged with a twisted Y-link 30. The Y-shaped link includes bifurcated flanges at a first end for receiving a single flange therebetween. At opposite ends, the Y-shaped link has a single flange. The Y-shaped links differ from the prior art in that each end pivots about an

orthogonal axis

50, 55, 60. The Y-link then connects 40 to the adapter plate 20 to transfer the tensile load from the interface 25 to the mooring line 15. Thus, regardless of the direction of movement of the structure, it is free to rotate about the two

main axes

50, 55, 60 in the horizontal plane and thus redistribute the load from the weaker axis and thus provide articulation about each horizontal axis.

Fig. 1B shows another embodiment according to the present invention. Here, the connection 65 connects 80 to an eye plate 70 for the foundation system for engaging the seabed. The present invention is foundation independent and can be combined with any foundation system such as piles, suction cans and gravity anchors. The connector 65 of fig. 1B differs from the connector 5 of fig. 1A in that, while both share twisted Y-

links

30, 75 according to one embodiment of the invention, the connector of fig. 1B includes a twisted H-link 85 that replaces the adapter plate of fig. 1A. Similar to the Y-shaped links, the H-shaped links have bifurcated flanges at each opposite end. However, according to this embodiment, similar to the Y-shaped links, the pin joint connection pivots about an orthogonal axis at each end. It will be noted that the twisted H-shaped link 85 used in fig. 1B can be used for the connector in fig. 1A as well. Thus, the combination of the twisted H-link and twisted Y-link provides additional hinge points about the horizontal

main axes

90, 95, 100 and is thus a beneficial improvement over the connection of fig. 1A.

When considering conventional TLP configurations, tendons are commonly employed as mooring lines. Not only is initial capital expenditure significant, corrosion problems and general maintenance represent a significant lifecycle cost.

To this end, in one embodiment, the TLP includes applying composite and/or polymer type ropes/lines as tendons for the TLP. The fibers of the composite material can be Kevlar, aramid, polyester, HDPE, PP, nylon, ultra-high molecular weight polyethylene or carbon.

In addition to superior corrosion resistance, composites and polymer ropes with specific gravities close to 1 are buoyant or only slightly negative. The buoyancy benefits of polymeric ropes represent a reduction in the size of other components due to the dead weight of the rebar resulting in over-design and widespread installation of the offshore structure, resulting in an overall reduction in capital expenditure and offshore operational risks.

As shown in fig. 3A-3C, the connection 120 to the TLP 115 also allows full movement of the

adaptor plates

122, 125, 130 and enables the horizontal stowage of 122 to reduce draft requirements and enable shallow water areas.

Gravity-based anchor designs are not suitable for use on seafloors with soft clay and soft soil. The main problems faced are the settlement and slippage of the gravity anchors, which will cause the floating structure to become inoperative, lost positioning or become unstable and pose a risk to assets in its vicinity, such as many pipelines and oil and gas development areas of subsea cables present in its vicinity. Significant slippage of the gravity anchors can lead to catastrophic disasters, leading to pipeline or cable breaks. On the other hand, if a fully closed skirt is used to enhance lateral stability (and vertical load bearing capacity), there may be challenges associated with proper soil consolidation, soil draining from under the gravity-based anchors due to immediate settling, coupling pumping effects, which may hamper proper "seating" of the gravity anchors and cause significant long term behavioral uncertainty. This is especially true for thick layers of soft topsoil which contain a high proportion of soil, clay and/or peat, without the need for site preparation of shallow foundations. Figures 4 to 6 show various embodiments of gravity anchors according to the present invention, which aim to solve these problems.

In overcoming the problem of lateral movement when engaging soft soil on the seabed, the present invention comprises a number of interference members arranged to increase the lateral resistance of the gravity anchor, thereby impeding sliding. The interference member is arranged to be embedded in the soft soil of the seabed and thus to cause a greater interference with the soil of the seabed by a larger bearing surface than the friction of the base of the gravity anchor alone.

In fig. 4A and 4B, the interference member is provided as a plurality of planar steel plates/reinforced concrete plates, or a skirt 145 protruding from the base of the gravity anchor central portion 142, and is disposed on the outer circumference around the gravity anchor central portion 142. The skirt is arranged to embed into the seabed 160 when the base of the gravity anchor contacts the seabed. Thus, the sliding of the gravitational anchor 140 is resisted 165 by the bearing surfaces of the

skirt members

145, 155.

In alternative embodiments the skirt may be a single member on each side of the gravity anchor, however in this embodiment each skirt member includes a slit 150 separating the

skirt members

145, 155 through which soft soil of the seabed may flow. These slots 150 allow soil particles to flow out or drain immediately after settling and consolidation so that the gravity anchors 140 find an equilibrium position relative to the seabed. This feature is particularly important in the case of soft soils such as clay, mud and/or peat. Having the gravity anchors according to the present invention reach an equilibrium position allows for better and more predictable embedding in soft soil, which reduces the risk of excessive differential settlement and unpredictable long-term consolidation.

In another embodiment, an additional skirt member 185 may be mounted to the gravity anchor base 170, not just around the perimeter, to provide greater resistance 180 against lateral sliding and bottom stability. The precondition for this feature is that the additional skirt member has a depth less than or equal to the peripheral skirt. In addition to providing greater resistance 180 and bottom stability against sliding, additional skirt members 185 may be included for structural reinforcement or stiffening purposes of the gravity anchor base 170. For this purpose, although additional skirt members may be provided to prevent or limit lateral movement, reinforcing skirt members may be used on the underside of the central portion, these reinforcing skirt members being provided to add reinforcement and thus may not be aligned to prevent or limit lateral movement, but rather to provide structural functionality.

Further, the gravity anchors 140 may benefit from the assistance of buoyancy bags for loading and/or transporting the gravity anchors to open waters via wet towing to meet the draft or wealth depth (UKC) requirements of a dock/port/dockside/channel/shallow water.

Fig. 5A to 5C show another embodiment using an interference member. In this embodiment, the interference member is a protrusion 190 protruding downward from the base 170 of the gravity anchor central portion 142. The protrusion 190 may be relatively narrow to more easily penetrate the seabed and achieve penetration of the gravity anchor. The protrusions may be tubular/square/rectangular piles, rods, reinforcing bars, and other rigid structural members of sufficient diameter to maintain integrity and enable the protrusions to be smoothly embedded into the seabed 160.

It will be appreciated that the protrusion may be more easily embedded in the seabed than the skirt member. Thus, the number of lugs used will depend on the balance between the lateral resistance 200 and the ability to embed under the weight of the gravitational anchor 140.

In another embodiment, the tab 194 may be in sliding engagement with the gravity anchor central portion 142, wherein the central portion 142 has an aperture 192, and the aperture 192 may include a conduit that allows sliding of the tab 192 relative to the central portion 142. The sliding may then be controlled by using a shear clip 195 mounted to each tab 194. It should be appreciated that the consistency of the seabed may vary around the gravitational anchor 140 and thus some protrusions may encounter greater penetration resistance than others. If the soil of the seabed in one area is much stiffer than the soil of the other area, the protrusion 194 may buckle and potentially damage the gravity anchor 140. Furthermore, the gravity anchors may not sit flush on the seabed due to lack of penetration of the one or more protrusions that are not fully embedded. Thus, in this further embodiment, the shear clip 195 may be knocked against the axial force applied to each tab. For example, the release force of each shear clip 195 may be rated to be equal to the weight of the gravitational anchor divided by the number of lugs. The security factor may or may not be applicable. Such safety factors may include preventing the shear clip from releasing upon impact, and thus creep factors may also be employed to prevent the gravity anchor from releasing upon contact with the seafloor.

If one of the projections 205A exceeds the rated force due to harder soil resisting penetration, the shear clip will release and push the unperforated length 205B of the projection upward, allowing the gravity anchor to sit flush on the seabed. It will be noted that even the partially penetrated protrusion 205A may still provide the sliding resistance 210. In yet another embodiment of the present interference member invention, a gravity anchor 140 is shown in FIG. 6, the gravity anchor 140 having a plurality of protrusions 215 protruding upward from the top 220 of the gravity anchor central portion 142. In this embodiment, the gravity anchors are intended to be placed on the seabed first, and then a mechanical force is applied to each protrusion to force each protrusion to penetrate into the seabed. The mechanical application of force may be as simple as a collar of steel or concrete arranged to sit on the protrusion and embed the protrusion by self weight, mechanical impact or vibration. Alternatively, each protrusion may be individually hammered or otherwise driven/forced into the seabed.

In equatorial/tropical countries, the water part of the offshore structure comprising the drilling platform and the wind turbine tower may experience undesired heat accumulation due to high ambient temperature, solar radiation etc. In addition to the safety hazards associated with heat, this is also disadvantageous for temperature sensitive devices such as converters/batteries, etc. Conventional solutions to date involve energy intensive options such as air conditioning systems/HVAC.

Fig. 7 shows an embodiment in which a substructure of an offshore platform may be used as a heat exchanger. In this case, the substructure includes support reinforcing members 230, hangers 235, and anchors 240. It is known to include cavities within structural members for cost-effective construction. By providing a fluid path through the cavities of the various

structural components

230, 235, 240, the air flow may be captured 250 and arranged to flow 255 into the inlet 262 from above sea level to below sea level 245. As the air flow passes through the cavity, the substructure acts as a heat exchanger to the area of the cooler water interface, dissipating heat to expel the cooler air 260 from the outlet 264. The flow of cooling air may then be used to cool the entire structure, as well as cool sensitive components within the offshore structure.

The trapped air may be able to direct wind into the substructure either naturally or forcibly. For example, a movable shutter may be used, which is arranged to rotate into the direction of the wind and direct the air flow downwards into the substructure.

Alternatively, a fan along the fluid path may draw an air flow into the substructure.

In addition, the substructure may be modified or specialized to provide fins and other heat exchange means to optimize heat dissipation from the hot air to the cooler substructure. This may for instance be in the form of a dual purpose structural member in the case of a floating structure, whereby the hull stiffener serves a dual purpose, both as a structural stiffener and as a cooling fin/protrusion.

Claims

1. A mooring connector comprising:

a linkage comprising a plurality of hinge components, adjacent hinge components of the linkage being engaged with a pin joint and arranged to pivot about a first axis at the pin joint;

wherein at least one pin joint within the linkage is arranged to pivot about a second axis, the second axis being orthogonal to the first axis.

2. A mooring connection as claimed in claim 1, wherein one of the linkage members is a Y-shaped link comprising bifurcated double flanges at a first end and a single flange at an opposite end, each end forming a pin joint arranged to pivot about axes orthogonal to each other.

3. A mooring connection as claimed in claim 1 or 2, wherein one of the linkage members is an H-shaped link comprising bifurcated double flanges at each opposite end, each end forming a pin joint arranged to pivot about axes orthogonal to each other.

4. A mooring connector as claimed in any of claims 1 to 3, wherein one of the linkage members is an adapter plate comprising a pair of parallel plates, and opposite ends of the adapter plate form a pin joint.

5. A mooring connector as claimed in any of claims 1 to 4, wherein the mooring connector is connected at a first end to a tension leg platform comprising composite tendons.

6. A gravity anchor for an offshore structure, the gravity anchor comprising:

a base for contacting a seabed;

an interference member arranged to protrude from the base and arranged to be embedded in the seabed.

7. The gravity anchor of claim 6, wherein the interference member includes a skirt.

8. The gravity anchor according to claim 6, wherein adjacent skirts are separated by slits arranged to allow soil from the seabed to move/flow between the skirts.

9. The gravity anchor according to claim 6, wherein the interference member comprises a protrusion comprising any one or combination of a tubular/square/rectangular stake, rod, tube or reinforcement strip.

10. The gravity anchor according to claim 9, wherein each protrusion is in sliding engagement with a central portion of the gravity anchor.

11. A gravity anchor according to claim 9 or 10, wherein each protrusion is mounted to the central portion with a shear clip arranged to resist axial loads applied to the protrusion until a rated load is reached, the shear clip then being arranged to release the protrusion.

12. A substructure for an offshore structure, the substructure comprising:

an inlet and an outlet, both positioned above a horizontal plane;

the inlet and the outlet are in fluid communication via an air flow path;

the air flow path having at least a portion below the horizontal plane;

wherein the air flow path is in thermal communication with water and is arranged to transfer heat from the air flow to the water.

13. A substructure according to claim 12, wherein the air flow path comprises a heat exchange device along a portion below the water level, the heat exchange device being arranged to increase heat transfer from the water to the air flow path.

14. A substructure according to claim 12 or 13, wherein the inlet comprises wind direction means arranged to direct wind into the air flow path.

15. A substructure according to claim 12 or 13, further comprising a fan arranged to draw air into the inlet and drive the air flow through the air flow path.