Removable anchoring system

Abstract

To provide a detachable mooring system for an offshore semisubmersible type floating structure.SOLUTION: A removable mooring system for an offshore semisubmersible floating structure. The detachable buoy has several mooring lines with a buoy chain between the mooring chain and the buoy. The mooring chain and the buoy chain are coupled via a three way mooring connector, and the third coupling is configured to pull the mooring connector to a mooring point of the structure. In a first configuration, the buoy is detached and supports a mooring chain that is retracted for retrieval at shallow depths. In a second configuration, the mooring lines are retracted through the mooring connectors, thereby multi-point mooring the structure with the buoy chain remaining as a catenary between the buoy and the mooring points.SELECTED DRAWING: Figure 2b

Description

[Technical Field]

[0001] The present invention relates to a mooring system for an offshore semi-submersible floating structure, particularly but not exclusively, a floating structure. This invention relates to a removable mooring system for a modular offshore wind turbine. [Background technology]

[0002] Wind power is a recognized and frequently used renewable energy source. Energy yield can be obtained and there are fewer spatial constraints compared to those on land. Offshore locations for wind turbines are currently being sought. The first offshore wind turbines will be built on the seabed. The jacket is generally constructed on a monopile foundation buried in the ground. The foundations are constructed like steel grid structures laid on the ground, and they are at greater depths and Its use has developed because it is more robust with respect to the size of foundations and certain types of underground. To allow for deeper water access and reduce construction costs compared to a jacket Floating offshore wind turbines (FOWTs) are currently in use.

[0003] It is expected that FOWTs will need to be removed at many points during their service life. In particular, the increasing size and height of turbines, the increasing motion at the nacelle level, and the increasing This is due to the complexity of major repairs to the jack-up reactor, which is anchored to the seabed. This is further complicated by the fact that the water is often too deep for lane vessels, and therefore floating vessels. It is necessary to use a crane ship. The movement of the crane tip of the crane ship is It is much larger than a Pneumatic vessel. If the turbine is mounted in a jacket, Such movements are very unlikely because the jacket is anchored to the seabed. It can be ignored.

[0004] 1a to 1c show a typical prior art arrangement of a multi-point moored multi-column semi-submersible FOWT. Figure 1a shows a semi-submersible 4 connected to mooring lines 20a which connect to anchors on the seabed. In such a multi-point mooring, each mooring line is individually connected to each corner of the installation and maintained in a fixed orientation. For clarity, only three mooring lines are shown in the example, but typically the design requires Up to 6-9 mooring lines may be required. Dynamic Power Cable Riser 10 is exemplified in a lazy wave configuration utilizing a float 12. Figure 1b shows the Show placement.

[0005] Detail 1c shows the use of a winch 13 from the top of the pillar to bypass the sheave 14. This is a typical arrangement for pulling in mooring lines through a semi-submersible female coupling device 15. The inch is connected to the end of the mooring connector 16 and when fully engaged, is removed.

[0006] There are many different types of mooring connectors available in the prior art. The designs shown are for illustration purposes only.

[0007] This arrangement is typical not only of semi-submersibles but also of various other moored floating structures and vessels. be. Summary of the Invention

[0008] The drawback of these arrangements is that they typically require 3-9 mooring lines plus typically 2 The dynamic power cable makes it easy to disconnect and reconnect the offshore FOWT. The mooring lines and power cable system are time-consuming and expensive. The connection involves individually locating, measuring, lifting, and connecting each rope end to the FOWT. During this time, the FOWT must be held in place by the towing vessel. The connection may be necessary, especially in deep waters or if the area is connected to platforms, vessels, or other This can be a long and difficult process if the area is crowded with floating structures and their moorings. The dynamic power cable retraction is carried out after the mooring connection is completed, and the cable The bull coupling itself can be lengthy with risk of injury.

[0009] Other floating vessels, such as ships, have a mooring line that is attached to a swivel at a point around which the vessel rotates. The turret mooring system is a standard mooring system (SPM). , reducing stress on the mooring system by weathervaning or pointing the vessel into windward U.S. Patent Application Publication No. 2007 / 0264889 is intended to be used in harsh environments where A detachable underwater turret buoy is disclosed that provides single-point mooring (SPM) for a vessel. A) is a mooring vessel attached to a radius that is much smaller than the vessel's width and much smaller than the vessel's length. The buoy is retracted and secured to the vessel. The turret reacts to wind, waves and currents. The swivel allows the vessel to weathervane around the turret while stationary. do.

[0010] WO 2016069636 discloses a detachable buoy system for FOWT. In this system, the power cable is supported by a buoy and the mooring line runs from the buoy to the The yachts are separated from the main yachts and individually connected to each mast in a standard multi-point mooring arrangement. If the power cable removes the detachable buoy, it must hold it in place. However, it is important to ensure that the buoy is not damaged by its movement. Furthermore, buoys become very large in deep water due to the weight of the cables, which limits offshore operations. There is a possibility.

[0011] The corners of a semi-submersible floating structure may be 50m to 150m apart, so It is not practical to use a submersible turret buoy with such large dimensions. The design of the turret buoy, which can be mounted at only one point on the semi-submersible, is an asymmetric structure. There is a high possibility of rotation around this point, causing the mooring and cable to twist around each other, and if the swivel This adds significantly to the cost and complexity if the control is not built in. If a swivel is installed, the semi-submersible type may interfere with the swivel located in the turbine nacelle. This allows the weather vaning to orient the blades in the optimal direction.

[0012] It is therefore an object of the present invention to obviate or mitigate one or more disadvantages of the prior art. The present invention provides a removable mooring system for an offshore semi-submersible floating structure.

[0013] According to a first aspect of the present invention, a removable mooring system for an offshore semi-submersible floating structure is provided. a mooring system comprising: a buoy including means for connecting to and detaching from a structure; A plurality of mooring lines, Each mooring line includes a mooring chain, and a first mooring line is connected to the mooring chain by an anchor on the seabed. having an end portion, Also, at least one mooring line comprises a buoy chain, and a first end of the buoy chain is attached to the anchor. The second end of the buoy chain is connected to the second end of the mooring chain via a mooring connector. a plurality of mooring lines connected to the buoy; In use, in the first configuration, the buoy is detached from the structure and the buoy chain is attached to the mooring chain. and prevent the mooring connector from contacting the seabed. In the second configuration, the buoy is connected to the structure and the mooring chain is attached to the structure via a mooring connector. The buoy chain is pulled into the mooring point of the object, putting tension on the mooring chain, which causes the buoy chain to The structure is moored at multiple points in a nally state.

[0014] In this way, the mooring chain is attached to the mooring points around the structure in the same pattern as in the case of multi-point moorings. Each can be deployed from a separate buoy, and each is also attached to a removable buoy. This has the advantage that it only needs to be reeled in from shallow depths. This may be a wire, cable or rope element or part of a standard mooring line. It should be understood that the term "component" can refer to any element that constitutes the component.

[0015] The means for connecting and disconnecting the removable buoy to the structure is preferably swivel-less. In this way, the mooring system prevents the structure from weathervaning and allows other It is cheaper than the turret buoy system.

[0016] In the second configuration, the mooring tension on the buoy is preferably applied from only one side of the buoy. If a buoy chain is present, tension is applied to the mooring point instead, and the mooring line is then pulled to the buoy. In one embodiment, all mooring lines are provided with buoy chains. In addition, there is no mooring tension on the buoy.

[0017] There is at least one mooring line that connects the second end of the mooring directly to the buoy, and this mooring The mooring line applies mooring tension to the buoy. Preferably, there is only one such mooring line on a buoy. Alternatively, there may be several such mooring lines, but they should all be attached to only one side of the buoy. In this way, a mooring tension is applied to the buoy from a first direction. Such mooring lines are placed on the side of the buoy and provide mooring tension over an arc of less than 180 degrees. More preferably, the arc is 130 degrees or less. The arc is 90 degrees or less. The arc may be less than 45 degrees. There may be two mooring lines consisting of mooring chains only. Preferably, the forces from the environment act on the buoy via the moorings on only one side of the buoy.

[0018] The mooring connector comprises a first connection to the mooring chain, a second connection to the buoy chain, and a three-way connector with a third connection for connecting to a mooring point on the structure. It is preferable that:

[0019] In one embodiment, the third linkage includes a connector for connecting to a winch or other similar retracting device. Thus, the third coupling portion is provided with a mating connector for connecting the third coupling portion to the second coupling portion. This relates to a prior art device for connecting and retracting mooring lines. The mooring chain and connector are aligned such that the second link is perpendicular to the first and third links. Alternatively, each connector may rotate so that the mating connectors The actuators will assume positions depending on the tension applied to each link. The lashings can be retracted by known devices.

[0020] the at least one mooring line also comprising a buoy chain further comprising a second mooring chain; The second mooring chain has a first end that connects to an anchor on the seabed and a second end that connects to a mooring connector. and a second end of the at least one mooring line, which also includes a buoy chain. and a third mooring chain, the third mooring chain being connected to an anchor on the seabed. The first end and the second end connect to the tether connector. Use buoy chains and mooring connectors to pull multiple mooring chains into mooring points The mooring connectors may each be a 4-way or 5-way connector. It will be understood that there is.

[0021] Two or more mooring chains can be connected to a single anchor on the seabed. , mooring lines from a single anchor can be placed at different mooring points on the structure.

[0022] The buoy may, in use, be fully submerged in both the first and second configurations. , may be connected to the bottom of the structure. The bottom may be a keel. In this way, the buoy , considered as a plug placed under the structure and connecting to the base of any column or the center point of the structure. The dimensions of the buoy can be much smaller than the structure. Alternatively, the buoy can be Alternatively, the buoy may be partially submerged in both the first and second configurations. The buoy may be secured to the side of the structure. The buoy may be fixed to a pole of the structure. Single pole spar type floating structure The object is particularly suitable for fastening the buoy to the side. In this way, the buoy can be safely secured to the side if it is removed. Whenever a structure is floated for mooring purposes, it will always break through the water surface and be easily identified. The position of the buoy in the water is determined by the length of the mooring line, which is calculated from its weight and the depth of the sea. The buoy can be controlled by the ballast or by the speed of the buoy.

[0023] The buoy chain is preferably lighter than the mooring chain. A lighter gauge chain is selected to avoid tension when the structure is moored. It can be done.

[0024] The buoy also preferably includes a cable connection. The cable may be used for power or communications It can be used for signal transmission. The buoy may also have riser connections. The flexible riser can be used for transporting fluids or gases. to install power cables and / or risers inside the structure or topside installations. More preferably, the manifold is provided on the buoy. When the buoy is removed, continuity between two or more risers can be achieved. This is particularly advantageous for offshore wind applications, where the cable ends would otherwise be laid far apart on the seabed. If this occurs, the electrical circuit is broken.

[0025] The floating semi-submersible structure is preferably a multi-column floating semi-submersible structure. Alternatively, a mooring point can be placed on each pole, or a buoy can be attached to one pole. However, any floating structure of large dimensions, such as a ship, boat, purge vessel, or The spar or spar may be considered to cause weather vaning. Preferably, the structure supports a wind turbine.

[0026] A floating semi-submersible structure can be fitted with multiple buoys, and the buoys can be connected to each other. The buoy is thus the entire cable / dynamic riser of the structure. is placed wherever needed and the buoys maintain their relative positions as in the first configuration.

[0027] According to a second aspect of the present invention, there is provided a method of mooring an offshore semi-submersible floating structure, comprising: The method is: (a) providing a removable mooring system according to a first aspect; (b) connecting the buoy to the structure; (c) Pull the mooring connector into the mooring point on the structure and secure the mooring line, which also includes the buoy chain. tensioning each of the mooring chains; (d) thereby providing multi-point mooring around the structure; Includes:

[0028] The method may include fully or partially submerging the buoy. ), the buoy is either tied to the bottom of the structure or secured to the side of the structure.

[0029] The method comprises a separate process for removing the removable mooring system from the offshore semi-submersible floating structure. The removing step may include removing the vehicle using a winch or other method known in the art. Removable moorings can be installed in a controlled manner by lowering mooring lines and buoys using the Alternatively, the step of detaching may include the step of releasing the system. The removable anchor is released by an emergency release method in which the anchor and buoy fall under gravity to the equilibrium depth. This may include the step of releasing the mooring system, which may include quickly removing the mooring system. but the moorings, buoys and cables must be in a safe position ready for efficient re-connection. This has the great advantage of remaining as is. [Brief explanation of the drawings]

[0030] In the following description, the drawings are not necessarily drawn to scale. , may be shown to scale or slightly schematic, and some details of conventional elements may be , may not be shown for the sake of clarity and brevity. The indications and features may be used separately or in any suitable combination to produce the desired result. It should be fully appreciated that the present invention can be used in various ways.

[0031] Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive. Furthermore, the terms and phrases used herein are for descriptive purposes only. and should not be construed as limiting the scope.

[0032] Various embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which:

[0033] [Figure 1a] 1a, 1b and 1c show mooring systems for offshore semi-submersible floating structures according to the prior art. [Figure 1b] Same as above. [Figure 1c] Same as above. [Figure 2a] 2a, 2b and 2c are mooring systems for offshore semi-submersible floating structures shown in a second configuration according to one embodiment of the present invention. [Figure 2b] Same as above. [Figure 2c] Same as above. [Figure 3a] Figures 3a, 3b and 3c are the mooring system of Figures 2a, 2b and 2c shown in a first configuration according to one embodiment of the present invention. [Figure 3b] Same as above. [Figure 3c] Same as above. [Figure 4] Figures 4a to 4f show steps of coupling the mooring system of Figures 2a to 2c from a first configuration to a second configuration. [Figure 5a] Figures 5a, 5b, 5c and 5d are buoys in the mooring systems of Figures 2a, 2b and 2c. [Figure 5b] Same as above. [Figure 5c] Same as above. [Figure 5d] Same as above. [Figure 6a] 6a and 6b are a mooring system for an offshore semi-submersible floating structure shown in a second configuration according to another embodiment of the present invention. [Figure 6b] Same as above. [Figure 7a] 7a-e are another embodiment of a mooring system according to an embodiment of the present invention. [Figure 7b] Same as above. [Figure 7c] Same as above. [Figure 7d] Same as above. [Figure 7e] Same as above. [Figure 8a] 8a, 8b and 8c are yet another embodiment of a mooring system according to an embodiment of the present invention. [Figure 8b] Same as above. [Figure 8c] Same as above. [Figure 9a] 9a and 9b are yet another embodiment of a mooring system according to an embodiment of the present invention. [Figure 9b] Same as above. [Figure 10a] 10a, 10b and 10c are a single column semi-submersible structure with buoys connected to the side of the structure according to one embodiment of the present invention. [Figure 10b] Same as above. [Figure 10c] Same as above. [Figure 11a] 11a and 11b are a mooring system for an offshore semi-submersible barge-type floating structure according to one embodiment of the present invention. [Figure 11b] Same as above. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0034] Referring first to Figures 2a-2c, an offshore semi-submersible vessel, generally designated by reference numeral 11, A mooring system 11 is shown connecting to a floating structure 4, the system 11 being an embodiment of the present invention. The ship is provided with buoy chains 22b and 22c in various shapes, a buoy 24, and mooring lines 20a to 20c.

[0035] In FIG. 2, the offshore semi-submersible floating structure 4 is a structure consisting of three columns floating in the sea with the waterline 2 broken. Although a three-pole semi-submersible type is shown, the offshore semi-submersible floating structure is a wind turbine. The floating structure may be any floating structure supporting a turbine 6. The buoy 24 is attached to the bottom or outer pillar of the semi-submersible 4. is connected to the keel, and mooring lines 20a to 20c are connected to the semi-submersible 4 via a buoy 24.

[0036] FIG. 2a shows a turbine 6 of the same size, a semi-submersible 4 and mooring lines 20a-20c. 1a-c show a similar arrangement to the prior art. In the plan view, buoy chains 22b and 2 Apart from an additional mooring line or "buoy line" underneath the semi-submersible 4, called 2c, the There is little obvious difference. The mooring line 20a is anchored at a first end to the seabed 21 and at a second end to the The mooring line 20a is a mooring chain whose end is connected to the buoy 24. The chain used to secure the mooring system is called a mooring chain. The mooring lines 20b, c may also be wires, ropes, or other similar lines. The mooring chains are anchored at their first ends to the seabed 21. They are anchored at their second ends to the connected to the connector 18, which in turn is connected to the buoy chains 22b,c Again, they are called mooring chains or buoy chains, but these are used in mooring systems. A chain, cable, wire, rope, or other similar cordage used to secure The other ends of the buoy chains 22b and 22c are connected to the buoy 24. The mooring chains 20b, c and the buoy chains 22b, c are connected to the mooring chains 20b, c. In addition, a winch 13 is used from the top of the pillar to secure the sheave 1 at the mooring points 25b and 25c. 4 and pull in the mooring lines through the female connection device 15 on the semi-submersible 4. It is a three-way connector with a connection similar to that of the prior art.

[0037] FIG. 2b shows an elevation view of the same arrangement, with mooring lines 20a connected to a removable buoy 24. , buoy 24 is connected to the semi-submersible keel of one pillar. Mooring lines 20b and 20c are The buoy is connected to the semi-submersible at mooring points 25b and 25c. However, another buoy line 22b is connected to the buoy. The mooring lines are shown extending to semi-submersible tie-ins or mooring points 25b, c for the main mooring lines. do.

[0038] Detail 2c shows the mooring connector 18 connected to the "buoy line" or buoy chain 22b,c The figure shows a different design with connections for winches, sheaves, and The female connector retractor is adapted to mate the connector 18 with a receptor at a mooring point on the structure. The mooring chain 20 is connected to the The buoy chains 22b and 22c are subjected to the loads from the surroundings on the semi-submersible. The buoy chain hangs from the buoy 24 in a chain configuration. In this illustration, the buoy chain is is shown smaller than the mooring chain because it is not subjected to the loads of

[0039] The buoy 24 can be easily coupled to / detached from the semi-submersible hull. ) and supports the mooring 20 and power cable 10 in deeper water, but semi-submersible 4 By controlling the direction of the buoy, the need for a swivel is avoided. When the buoy is pulled into the water, if the top of the buoy is above the water surface or if the internal structure If the equipment can be made watertight, the power cables should be dynamic power cables. It can be connected to the structure's electrical system without handling, which reduces costs and Significantly improves safety.

[0040] When connected to the structure 4, the buoy 24 is generally oriented along the arc of the confined arc. The mooring load is transmitted only from the mooring lines 20b, c connected to the inside of the buoy 24. The mooring line 20a is directly connected to the seabed 21, and is subjected to mooring tension only from one direction. Chains 20b, c are pulled into mooring points 25b, c on structure 4 via mooring connectors 18. If the structure 4 has redundant buoy chains 22b,c, the anchors on the lines 20b,c are The mooring chains 20b and 20c are pulled in and the mooring ropes 20a to 20c are pulled. Once deployed, the semi-submersible 4 is moored in the same multi-point mooring arrangement as in the prior art of Figures 1a-c.

[0041] The mooring chains 20b, c and the buoy chains 22b, c have connections between each section. It is a continuous line which itself connects to the semi-submersible 4 at mooring points 25b, c.

[0042] Figure 3 shows the now-removed buoy in its submerged state prior to the arrival or departure of the semi-submersible 4. The removed buoy 24 is considered the first configuration of the mooring system 11. A buoy 24 connected to a structure 4 as shown in Figures 2a-c can be considered as a second configuration. It can be done.

[0043] FIG. 3a shows the first mooring vessel in a detached state with the buoy 24 and mooring lines 20a-20c. The mooring lines 20b and 20c are "buoy lines"; buoy chains 22b and 22c and mooring connectors 18b and 18c It is connected to the buoy via a

[0044] Figure 3b shows that the buoy 24 is lowered deep into the water to avoid the keel of a passing ship. The mooring line 20b is a catenary similar to the buoy line 22b. Therefore, both the mooring lines and the power cables must be lowered to the seabed 21. and the arrangement is stable in the water.

[0045] Detail 3c shows the boat in its removed state, approximately 90° from the orientation in which it would connect to the mooring catenary. Connector 18 is shown rotated 0 degrees. Mooring chains 20b, c and buoy chain 2 By using pivot connections to the mooring connectors 18 of 0b and 0c, The mooring connector 18 can rotate to change the angle between the connections. The buoy chain 22 can be used to support the weight of the mooring line 20 and the removable buoy 24. The buoy is shown with smaller dimensions because it is only subjected to the forces of the surrounding water. By reducing the size of the chain, the buoyancy required for the removable buoy 24 is also reduced, Strikes will be further reduced.

[0046] Therefore, buoy 24, when removed, is either directly connected to buoy 20a or , or a short "buoy" chain 22 that would be redundant if the semi-submersible 4 were fully articulated. b, c, or supported by all mooring lines 20a-c. It is possible.

[0047] Extra length of "buoy chain" on the mooring catenary when removed from the semi-submersible By introducing the buoyancy required to keep the mooring lines and power cables in the water, Decrease due to low retention.

[0048] Here, the buoy 24 is pulled into the semi-submersible 4, and the mooring lines 20b, c are connected to the structure. Reference is made to Figures 4a-f of the drawings which show a typical procedure for achieving a permanently moored state. 4a-f show how the buoy 24 and mooring lines 20a-c are connected to the semi-submersible 4. For ease of understanding, the dynamic riser 10 is not shown, and only two mooring lines are shown. As shown in the diagram, there are three or more mooring lines, e.g., 3, 6, 8, 9, 12, 15, or 1 If there are six, the same method will generally be used.

[0049] Figure 4a shows the buoy 24 under the semi-submersible 4, with a winch 34 attached to one of the posts. The winch wire passes through the pillar and connects to the buoy 24 under the keel. The mooring lines 20b are connected to the submarine anchors and buoys via the mooring connectors 18b. The buoy chain 22b is connected to the bottom anchor and buoy chain 22b. To assist in the docking operation, a support remotely operated vehicle (ROV) 32 is provided. 30 support ships are deployed nearby.

[0050] FIG. 4b shows the buoy 24 retracted into the semi-submersible 4. Here, the mooring lines 20a are only The vessel is under very high tension and is connected to the semi-submersible 4 via a buoy 24.

[0051] Figure 4c shows winch 3 repositioned to allow for retraction of the mooring onto the semi-submersible. 4. The winch wire 36 is lowered from the winch to near the mooring connector 18b. Using the ROV 32 from the support vessel 30, connect the winch wire to the mooring connector 18b. It can be connected to the hull and retracted into a semi-submersible type 4.

[0052] FIG. 4d shows the winch wire 36 connected to the mooring connector 18b and used to pull the semisubmersible 4. When the winch wire 36 is retracted, the tension of the mooring rope 20b is increased. The force increases and the tension in the buoy chain 22b decreases. At this time, the mooring connector 18b The angle becomes more perpendicular, i.e., moves from the position shown in Figure 3c to the position shown in Figure 2c.

[0053] Figure 4e shows the mooring connector 18b approaching its final position. At this point, the mooring line 20b and the buoy chain 22b to the pulling winch wire 36 hanging loosely. At this point, the angle of the mooring connector 18a passes the vertical and reaches its final position. One important feature of this arrangement is the angle of the mooring connector 18b. can be relatively easily directed towards the towing line, making it easy to connect the winch line underwater. In addition to the need to provide strong propulsion for anchor handling vessels to assist in the connection, This significantly reduces the risk and operational dependency on high tensions and the position of the vessel. This has the great advantage of reducing fuel consumption in the industry.

[0054] Figure 4f shows the mooring connector 18b being retracted into the semi-submersible and engaged at mooring point 25b. This indicates that the retracting winch wire is ready to be removed. The mooring line can be connected by moving the ear and winch to another mooring line. Then, the dynamic riser is installed a short distance inside the structure from the top of the buoy to its final location. can be retracted or coupled to the onboard system without further retraction, As a result, the connection between the mooring and the riser is completed.

[0055] The systems and methods of the present invention advantageously allow for the use of mooring lines and risers instead of shallow This means that the retraction can be done in a relatively short time. such as preventing twisting of mooring lines, restricting navigation, and maintaining clearance from other subsea infrastructure. The need to raise it from the seabed, which can be a lengthy process with attendant risks, Therefore, the size of the winch and the length of wire required are much smaller.

[0056] The load transfer is more gradual and controllable than lifting each mooring line from the seabed. All mooring lines are already tensioned, twist-free, and splayed out at their final azimuth. Because the vessel is clear of the water and the seabed, it has greater freedom of movement in the direction of the bow of the operation. Normally the stern must be in the retracted position.

[0057] After the mooring connection is complete, the cable or riser already connected to the buoy must be removed from the internal and tow The cable can transmit power, communication signals, etc., and can be connected to the equipment on the riser. The cable can move fluids, gases, or other cables.

[0058] The mooring system 11 can be configured to change its configuration from the second configuration (see Figures 2a-2c) to the first configuration (see Figure 3 It will be understood that the device can be removed (decoupled) to return to the original position (see a-3c). This removal is accomplished by controlled release of the winch in a manner known to those skilled in the art. However, in the present invention, the cables / risers and tethers are The mooring system11 can be used as an emergency / ultra-quick release system by remotely releasing it from the connector. If the mooring line and buoy are suddenly released, they will fall under the force of gravity into the water. It falls to an equilibrium position and assumes the first configuration arrangement without a mechanical lowering device.

[0059] Minimizes vessel movements and the handling of long mooring lines to and from the seabed. or not at all, making coupling and uncoupling operations significantly shorter and safer. This reduces the risk and cost of coupling and uncoupling FOWTs.

[0060] Referring now to Figures 5a-d, the mooring lines and 1 shows an embodiment of a detachable buoy, illustrating a dynamic riser / power cable configuration. is shown.

[0061] Figure 5a shows a detachable buoy with six mooring lines from above, with adjacent buoys Figure 1 shows how clearance is typically achieved between chains 22c-f. The buoy 24 is a circular truncated cone. The buoy 24 is attached to the heavier mooring line 20a and and 20b, a larger diameter arc is formed over an arc of approximately 120 degrees to provide additional buoyancy. It has separate buoyancy and is equipped with only mooring chains, and also with buoy chains 22c and 22f. The mooring chains of the mooring lines 20a and 20b are attached directly to the buoy structure. The buoy chains 22c and 22d, along with 22e and 22f, are connected to each other at the risk of collision. The sensors are spaced further apart to minimize noise.

[0062] FIG. 5b shows a perspective view of the buoy, with the dynamic riser 10 attached to the bottom of the buoy 24. and passes through the buoy 24 to the upper part, which is provided with bending stiffeners 28 to control the bending. where they can be suspended from the top of the I-tube 26. 24, the dynamic riser 10, and the mooring lines 20a, b and the buoy chain 22c ~22f shown from below.

[0063] FIG. 5d shows two risers 10a, b entering two I-pipes 26a, b, which are connected to a manifold. A cross section of the buoy is shown connecting together in the device 17 with the third riser 10c. The connection between the third riser 10c and the buoy 24 is made via a connector 19. The buoy 19 is typically a waterproof seal that protects the riser 10c when the buoy is lowered into the water. Therefore, the power cables or fluid cables in the risers 10a, b are expected to The risers 10a are continuous to avoid breakage during placement or removal. , b are shown, but similar connections via manifold 17 are made to the various risers and It will be appreciated that this can be done with respect to power cables or fluid cables. cormorant.

[0064] FIG. 6 shows a buoy 24 connected to the bottom or keel of the central pillar of the semisubmersible 5 and a mooring line 20 6a and 6c show another embodiment in which all of the submersibles 5 are connected to the semi-submersible 5 via a buoy 24. 6a and 6b show a side view of the semi-submersible 5 from above and with the mooring system 11. 24 is connected to the semi-submersible central mast 7 so that the power cable 10 can be easily connected. Although it is directly below the wind turbine 6 where it can be easily reached, it is not a desirable location for connecting mooring lines. , the mooring lines 20a to 20c all have buoy chains 22a to 22c, see Figures 4a to 4f and pulled into the outer pole mooring points as previously described herein. When connected to the structure 5, the buoy chains 22a-22c are under minimal tension. In this state, the buoy chain connects the mooring line via the connector as shown in Figure 3a to c. In this embodiment, the mooring tension applied to the buoy 24 from either direction is I have no strength.

[0065] Figures 7a-7e show two mooring lines connected to a single buoy chain and mooring connector. This shows the layout.

[0066] 7a and 7e show a first configuration of a mooring system according to another embodiment of the present invention. In this arrangement, the pair of mooring chains 20b, 20e and the pair of mooring chains 20c, 20f are The pair are connected by connectors 18. At this point, each pair also has a single buoy chain. 22b and 22c are shared. This arrangement reduces the number of mooring connectors and buoy chains. This reduces the number of moorings required for the system, further shortening the connection time. Although three chains are shown, there may be three or more. The number of servers may differ depending on the model.

[0067] Figures 7b and 7c show a triplate that allows multiple independent planes of movement for the mooring chain. Another design of mooring connector 18b with 23 can be used to connect the mooring chains 20b,e. Figure 7d shows the same configuration as Figure 7c and a typical detailed arrangement of connection points to fastening connectors. 1 shows a mooring connector 18 being pulled to a mooring point 25 on the structure 4. Indicates that.

[0068] 8a-8c, a method for detecting a buoyancy problem using multiple buoys according to another embodiment of the present invention is shown. Two alternative embodiments of a mooring system are shown that achieve rapid connection and disconnection. These arrangements are used when cables / risers need to enter different semi-submersible columns. preferable.

[0069] Figure 8a shows three installations connected by three buoy chains 22a, 22b and 22c. 2 shows a plan view of removable buoys 24a, 24b and 24c. Each buoy also has a submarine anchor. In this embodiment, the mooring chains 20a, 20b and 20c are connected to the car. The mooring points are on separate buoys. The buoy chain is slightly longer than the distance between each buoy. Therefore, if the buoys are connected to a semi-submersible, they will remain loose, but if all buoys are removed, The buoy chain aligns the buoys in the water by resisting the horizontal component of tension in the mooring lines.

[0070] FIG. 8b shows a buoy chain 22b hanging loosely between buoys 24a and 24b. The coupling configuration is shown in elevation, which is the same as the other two elevations of the semi-submersible.

[0071] FIG. 8c shows the position of buoy 24c, which may be the mooring connector shown in FIG. 3, between two buoys. Replaced by the connection between chains 22b and 22c and mooring chain 20c This diagram shows the use of only two buoys when only three mooring lines are shown. However, if a larger number, e.g., six, is used, the mooring lines 20e and 20f are connected to the buoy 2 4b and 24a, respectively.

[0072] These additional buoys are already attached to the structure and do not require the mooring lines to be retracted. The use of two or more buoys in this way is not a good idea as the two power cables are semi-submersible and This is particularly advantageous when the beam emerges from a position different from the beam.

[0073] Figures 9a and 9b show two mooring chains 20a, b, 20c, d, 20e, f. Each of them shares one anchor 40a, b, c, and in the case of multiple FOWTs, Four more, as shown by the two pairs of moorings 20g and 20h that connect to the WT. 10 shows an alternative mooring layout that allows for a mooring chain configuration.

[0074] The mooring system 11 includes mooring chains 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20m ... 9b, the mooring connector 18 has a wide angle between 0e and 0f. connected to either a single mooring chain or two adjacent mooring chains 20a, f This arrangement not only minimizes the installation cost of the anchors, but also It is highly efficient in terms of reducing duration and risk to a much lower level.

[0075] 10a, 10b and 10c show spar structures where the buoy 44 is instead connected to the side of the pillar. In this configuration, the buoy is positioned in a "horseshoe" configuration. The structure is shaped to allow maneuvering into position and mechanically attaching the buoy to the structure. The principle of connection to the side of the buoy is similar to that used for semi-submersible multi-column structures. The draft of the structure allows the buoy to have a portion 46 penetrating the water surface, and the position of the buoy and identifying the entry points of the spar is a desirable safety feature. Since this is primarily a horizontal connection, there is no need to pull the buoys vertically, but some buoy balancing is required. A tethering capability is advisable to allow for fine adjustment of the buoy's trim and draft.

[0076] FIG. 10b shows the power cable 10 connected to a buoy 44 and extending above the water surface through a vertical pipe 46. This eliminates the need to pull the power cable vertically, and the water line It can be connected in a dry state above the water. It is expected that there will be markings, such as lights and shapes, on the top of this tube.

[0077] Figure 10c shows another arrangement of buoys that extend above the waterline. This allows for close visual observation of the mating process between the structure and the machine, improving safety during the connection and disconnection work. Safety is improved.

[0078] Mooring ropes 20a to 20c are connected to the buoys so that the load on the structure is transmitted through the buoys. Alternatively, the mooring lines may be connected to the mooring connectors as shown in Figure 2c or 7d. and a buoy chain arrangement can be used to pull the vessel to the hull connection. The anchorage may be above or below the buoy.

[0079] Figure 10b shows the buoy chains 22c and 22d hanging vertically and loosely above the buoy. Mooring connectors 25c, 25d are shown attached to the structure.

[0080] Figure 10c shows the structure below the buoy with the buoy chain 22b hanging vertically slack. This arrangement allows the environment to load the mooring line 20b. When the mooring lines 20c, 20d are attached, the separation force between the buoy and the spar is minimal and the environment is When a load is applied to b, there is a structural advantage that there is a force pushing the spar into the buoy. do.

[0081] 11a-11b show a buoy 24 connected to the side of a barge 5, with a mooring line 20a running directly to the buoy. The mooring lines 20b, 20c are connected to connectors 25a, 25b. and thus connected to the structure using buoy chains 22a, 22b respectively. In this configuration, the riser 10 can be connected at deck level. However, bottom connections can be made as well, as shown in FIG.

[0082] The main advantage of this invention is the convenience of a "turret" style buoy and the versatility of a desired fixed orientation. The present invention provides a removable mooring system for offshore semi-submersible structures combined with a point mooring configuration. The purpose is to provide.

[0083] Another advantage of the present invention is that the buoy that can support the power cable is also a swivel bearing. It has no ring, and is not subjected to loads from the surroundings or from only one side. , the interior compartment into which the buoy is retracted can be made watertight or above the exterior water level In this case, the layout can be designed so as not to directly handle the submarine cables, and each line The sensors or cables may be in electrical or fluid communication with each other.

[0084] Yet another advantage of the present invention is that the mooring lines can be connected to the semi-submersible structure via connectors at the top of the lines. Pull upward onto the mating connector from a subsea buoy that can be retracted into position within the By hanging the mooring line by doing this, the connector is rotated approximately 90 degrees clockwise. Therefore, the pulling-in work is done by using the Instead, the pulling operation is gradual and much more It is done in a controlled manner.

[0085] A further advantage of the present invention is that the layout of the mooring system itself allows for the mooring lines and one or more facilitates rapid removal by remotely controlled release of multiple buoys, reducing the need for crew However, the mooring, the buoy or buoys and the risers must be in a position to allow for rapid reconnection. The key is to leave it in that state. [Prior art documents] [Patent documents]

[0086] [Patent Document 1] US Patent Application Publication No. 2007 / 0264889 [Patent Document 2] International Publication No. 2016 / 069636

Claims

1. 1. A removable mooring system for an offshore semi-submersible floating structure, comprising: a buoy including means for connecting to and detaching from said structure; A plurality of mooring lines, Each mooring line comprises a mooring chain, which is connected to an anchor on the seabed. having a first end; The at least one mooring line also includes a buoy chain, and a first end of the buoy chain is connected to the second end of the mooring chain via a mooring connector, and a plurality of mooring lines, the second ends of the buoy chain being connected to the buoy; Equipped with In use, in a first configuration, the buoy is removed from the structure and the buoy chain is Supporting the mooring chain and preventing the mooring connector from contacting the seabed; In a second configuration, the buoy is connected to the structure and the mooring chain is attached to the mooring connector. The mooring chain is pulled into the mooring point of the structure through a pulley, tensioning the mooring chain and As a result, the buoy chain moored the structure at multiple points in a catenary state. Removable mooring system.

2. In the second configuration, the mooring tension on the buoy is applied in only one direction. Detachable mooring system as described.

3. In at least one mooring line, the second end of the mooring chain is directly connected to the buoy. and the at least one mooring line is disposed on one side of the buoy, and the mooring line 3. A removable mooring system according to claim 1 or 2, wherein a mooring tension is applied to the buoy from one side. Mooring system.

4. 3. The removable mooring system of claim 1, wherein all of the mooring lines comprise buoy chains. Mooring system.

5. The mooring connector has a first connection to the mooring chain and a second connection to the buoy chain. two connections and a third connection for connection to the mooring point on the structure. The removable mooring system according to any one of claims 1 to 4, which is a three-way connector. Hmm.

6. The third connection has a fitting for connection to a winch or other similar retracting device.

6. The removable mooring system of claim 5, wherein a connector is provided.

7. Each link rotates so that the mating connector changes position depending on the tension applied to each link.

6. The removable mooring system of claim 5.

8. The at least one mooring line, which also comprises a buoy chain, further comprises a second mooring chain. The second mooring chain has a first end connected to another anchor on the seabed and a front end. and a second end connected to the tether connector. Detachable mooring system.

9. 9. The method according to claim 1, wherein two or more mooring chains are connected to respective anchors on the seabed. A removable mooring system according to any one of claims 1 to 4.

10. wherein the buoy is completely submerged in both the first and second configurations.

10. A removable mooring system according to any one of claims 1 to 9.

11. 11. The removable mooring system of claim 10, wherein the buoy is connected to the bottom of the structure. Stem.

12. 10. The buoy of claim 1, wherein the buoy is partially submerged in both the first and second configurations. A removable mooring system according to any one of claims 1 to 9.

13. 13. The removable mooring system of claim 12, wherein the buoy is secured to the side of the structure. Stem.

14. 14. The method according to claim 1, wherein the buoy chain is lighter than the mooring chain.

1. A removable mooring system as described in paragraph 1.

15. The buoy may be connected to an electrical cable or a flexible riser for transporting fluids or gases. The removable mooring system according to any one of claims 1 to 14, further comprising a connection for Tem.

16. If a manifold arrangement is provided as part of the buoy and is detachable from the structure 16. The arrangement of claim 15, wherein the arrangement allows electrical or fluid communication between two or more risers. Detachable mooring system.

17. Any one of claims 1 to 16, wherein the floating semi-submersible structure is a multi-column floating semi-submersible structure.

1. A removable mooring system according to any one of claims 1 to 5.

18. 18. A floating semi-submersible structure according to any one of claims 1 to 17, wherein the floating semi-submersible structure supports a wind turbine. Detachable mooring system as described.

19. Any one of claims 1 to 18, wherein the floating semi-submersible structure is a single-pillar floating semi-submersible structure. A removable mooring system according to any one of claims 1 to 4.

20. a plurality of buoys attached to the floating semi-submersible structure, and a connecting member for connecting pairs of the buoys; A removable mooring system according to any one of claims 1 to 19, comprising a buoy chain. Tem.

21. The mooring line is attached to the buoy on the side where the single-pillar floating semi-submersible structure enters the body of the buoy.

20. The removable mooring system of claim 19, wherein the removable mooring system is permanently connected to the

22. A method for mooring an offshore semi-submersible floating structure, comprising: (a) providing a removable mooring system according to any one of claims 1 to 21; The degree, (b) connecting a buoy to the structure; (c) Pulling in mooring connectors to mooring points on said structure, which also include buoy chains. tensioning the mooring chains of each mooring line; (d) thereby providing multi-point mooring around the structure; A method comprising:

23. The method further comprises removing the removable mooring system from the offshore semi-submersible floating structure.

23. The method for mooring an offshore semi-submersible floating structure according to claim 22, further comprising the step of detaching the floating structure. 。

24. The next step of removing the removable mooring system releases the mooring lines and buoys. and dropping the offshore platform as claimed in claim 23 to an equilibrium position in the water under the action of gravity. A method for mooring a submersible floating structure.

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