Mooring systems for fixed marine structures

Abstract

Techniques are disclosed herein for minimizing motion of fixed offshore structures. Using the described techniques, wind turbines can be attached to a fixed offshore platform (such as a fully restrained platform (FRP)) secured with mooring lines that can be maintained in tension to inhibit platform motion due to environmental loads (wind, waves, etc.). The mooring lines can be attached to the platform with an assembly that includes a stopper that is attached to the mooring line and engaged to a mooring pouch. The stopper can be positioned and / or repositioned to adjust tension in the connected mooring lines and secured in the adjusted position using various systems and techniques described herein.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 266,989, entitled "Mooring System for Fixed Marine Structures," filed on January 21, 2022, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] background Offshore areas at various depths away from the coastline offer huge potential for wind power resources. In deep water areas (e.g., greater than about 120 meters deep), floating marine structures, commonly referred to as "platforms", are used for exploration activities and for installing wind turbines. In shallower areas (e.g., less than about 50 meters deep), fixed structures attached to the seabed are commonly used for installing wind turbines and for providing platforms for various activities. Summary of the Invention [Problem to be solved by the invention]

[0003] For platforms located at any depth or at intermediate depths, it can be difficult to determine how to reduce the motion of such a platform to support a wind turbine. In the open ocean, wind, waves, and currents often act simultaneously and exert forces on an offshore platform, causing it to move. [Means for solving the problem]

[0004] The following detailed description is directed to techniques for minimizing motion of fixed marine structures, such as offshore wind turbines. [Brief description of the drawings]

[0005] [Figure 1]FIG. 1 illustrates an exemplary fully restrained platform (FRP) for supporting a wind turbine, according to an example of the present disclosure. [Diagram 2] FIG. 1 shows a diagram illustrating six degrees of freedom (DOF) motions that a fixed offshore structure may undergo and the natural frequencies of such a structure for the 6 DOF motions. [Diagram 3] 1 illustrates an FRP, mooring lines, and a mooring line tensioning system according to an example of the present disclosure. [Figure 4] FIG. 1 illustrates a mooring line tensioning system according to an example of the present disclosure. [Diagram 5] FIG. 1 illustrates a top mooring assembly (TMA) and tensioning system according to an example of the present disclosure. [Figure 6] FIG. 2 illustrates a TMA, according to an example of the present disclosure. [Figure 7] 1 illustrates a stopper and mooring line fitting according to an example of the present disclosure. [Figure 8] FIG. 2 illustrates a TMA, according to an example of the present disclosure. [Figure 9] 1 illustrates a FRP, mooring lines, and a mooring line tensioning system according to an example of the present disclosure. [Figure 10] FIG. 2 illustrates a TMA, according to an example of the present disclosure. [Figure 11] FIG. 2 illustrates a TMA, according to an example of the present disclosure. [Figure 12] FIG. 2 illustrates a fixed offshore structure and mooring line arrangement according to an example of the present disclosure. [Figure 13] FIG. 13 is a diagram illustrating an arrangement of several fixed offshore structures and mooring lines according to an example of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Detailed Description Using the technology described herein, wind turbines can be attached to fixed offshore structures constructed and attached to the seabed in any depth of water (e.g., shallow water (e.g., less than 50 meters deep), intermediate water (e.g., greater than 50 meters and less than 120 meters deep), and deep water (greater than 120 meters deep)). In various examples, the wind turbines can be attached to fully restrained platform (FRP) monopiles. Monopiles are pile structures driven into the seabed and may form part of or support a fixed offshore platform such as an FRP. As used herein, the term FRP refers to a platform with six degrees of freedom (DOF) restricted movement, and the term FRP monopile refers to an FRP including a monopile.

[0007] For purposes of explanation, the main structural components of the platform may be considered as a rigid body. Its motion may be characterized by and measured in six degrees of freedom (DOF), including three translational degrees of freedom (roar, sway, heave) and three rotational degrees of freedom (roll, pitch, yaw). Environmental loads may exert forces on the platform in one or more degrees of freedom. Some of these loads are dynamic in nature, such as wave loads, while others may be primarily static, such as loads due to ocean currents induced drag.

[0008] One example of a platform design philosophy is that in shallow waters, environmental loads are resisted primarily by the lateral stiffness of the platform, and the platform is designed to be "fixed." One example is a jacket platform, which is a lattice structure with its legs extending into the ground. In deep waters, however, the amount of material required for a fixed platform may become uneconomical, and therefore a floating platform may be used. Platform concepts may be deployed using various techniques to resist and / or allow motions operating in some or all of the six DOFs. For example, a fixed offshore platform using a bottom-mounted, driven-pile structure may be configured to resist motions in all six DOFs, a tension-leg platform (TLP) may allow pitch, yaw, and yaw motions (at least to some extent), while a semi-submersible platform may allow motions in all six DOFs (at least to some extent).

[0009] In current wind engineering practice, fixed offshore platforms may be used for shallow water areas, where the water depth is less than 50-60 meters and the wind, wave and current forces may be relatively smaller than in deeper water areas. However, fixed offshore platforms (such as FRP monopiles) may also be used in deeper water areas (e.g., up to 200 meters) that are subject to larger wind, wave and current forces.

[0010] It is desirable for a wind turbine to have as little movement as possible from its host structure in order to function effectively. A wind turbine supported by a platform that attempts to minimize movement in all six of its degrees of freedom may generate power more efficiently than a turbine mounted on a platform that does not restrict movement in all six degrees of freedom. Prior to the technology described herein, fixed platforms with such capabilities have not been effectively implemented to mount wind turbines in mid-deep water regions. As described herein, fixed offshore structures are disclosed that reduce and / or minimize movement in shallow and moderate water depths (e.g., up to a depth of 120 meters, or even more than 120 meters in calm environments). The disclosed structures may mount one or more wind turbines and associated structures and equipment.

[0011] An offshore wind turbine is a wind turbine mounted on an offshore platform. In various disclosed examples, the offshore platform can be an FRP monopile. Examples of FRP monopiles can be found, for example, in U.S. Patent Application No. 17 / 249,676, entitled "Minimizing Offshore Wind Turbine Movements," filed March 9, 2021, the contents of which are incorporated by reference herein in their entirety and for all purposes.

[0012] An offshore wind turbine mounted on an FRP monopile generally includes six main components: (1) a single pile ("monopile") driven into the seabed; (2) a wind tower with a wind turbine attached; (3) a transition piece attached to the monopile and to which the wind tower is attached; (4) one or more anchors secured to the seabed; (5) one or more mooring lines secured to the anchors and to one or both of the transition piece and the monopile; and (6) a wind turbine, which may include a nacelle (such as a housing), rotor hub, blades, and various other components. In addition to the wind turbine, other structures and equipment may also be attached to a platform such as the disclosed FRP monopile. As described in more detail below, the mooring lines may be connected to one or more connection components disposed on the transition piece and / or the monopile, which facilitate the application and adjustment of tension to the mooring lines.

[0013] Using the techniques described herein, motion in all six degrees of freedom of an offshore wind turbine attached to a fixed marine structure can be reduced and / or suppressed. The motions referred to herein are motions caused by various types of environmental loads. External forces causing motion include external forces from waves and ocean currents on the structure, external forces from moorings with parts of the turbine and / or structure in contact with the water, and external forces from wind on any part of the structure above the sea surface. Methods for assembly, transportation, installation, and development of adjacent wind turbine units and associated structures are also disclosed. Additional details regarding minimizing offshore wind turbine motion will be described below with respect to Figures 1-13.

[0014] In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and which show, for purposes of explanation, specific or generalized examples. The drawings shown herein are not drawn to scale. Like numerals represent like elements throughout the multiple views (which may be referred to herein as a "figure" or "figures").

[0015] 1 illustrates an exemplary wind turbine system 100 supported by an FRP monopile structure. Wind turbine system 100 may include a wind turbine 110, which may include a housing, a rotor hub, blades, and various other components associated with generating and / or collecting energy based on the rotation of one or more blades caused by wind forces. Wind turbine 110 may be mounted to, fixed to, or supported by a wind tower 120.

[0016] The wind tower 120 may be attached to, secured to, or supported by the transition piece 130, which in turn may be attached to, secured to, or supported by the monopile 140. Alternatively, the wind tower 120 may be attached to the monopile 140. The wind tower 120, transition piece 130, and monopile 140 may together form an FRP monopile 190 that supports the wind turbine 110. Each of the wind tower 120, transition piece 130, and monopile 140 may be constructed from any type of one or more materials and may include one or more portions and / or components arranged for various purposes. For example, the materials used to construct each of the wind tower 120, the transition piece 130, and the monopile 140 may be substantially rigid and / or treated to withstand marine environmental conditions (e.g., prolonged exposure to salt water, high winds, etc.). In certain examples, one or more buoyant structures may be disposed in or otherwise secured to one or more submerged portions of the transition piece 130 and the monopile 140 to compensate for forces that may be applied to such components, such as moorings.

[0017] The monopile 140 may be a single pile driven into the seabed 180 and may be substantially (e.g., completely) submerged. The monopile 140 may be secured underwater to a transition piece 130. The transition piece 130 includes a portion below the waterline 170 and above the waterline 170 and supports the wind tower 120 substantially (e.g., completely) above the waterline 170.

[0018] One or more components that enhance stability, such as mooring devices, may be attached to the FRP monopile 190. In an example, such components may be secured to the transition piece 130 and / or the monopile 140. For example, one or more mooring lines 150 may be attached to or connected to the transition piece 130 and / or the monopile 140. The mooring lines 150 may be secured to or attached to one or more anchors 160, which may be driven into or attached to the seabed 180. As described in more detail below, the individual mooring lines 150 may be connected to one or more connection components disposed on the transition piece 130 and / or the monopile 140 that facilitate application and adjustment of tension to the mooring lines. The mooring lines 150 may resist environmental forces that may be applied to the FRP monopile 190.

[0019] The FRP monopile 190 may form a beam column that is "clamped" at a first end (e.g., driven into the seabed 180) and supports a payload (e.g., wind turbine 110) at an opposite end. Mooring lines 150 attached to the FRP monopile 190 may form an intermediate support for the beam column. As an axially loaded structure located in a marine environment, the FRP monopile 190 may be subjected to a variety of steady and dynamic loads (e.g., loads from general weather and less general weather events such as storms). Such loads may be primarily lateral, for example, due to wind, waves, currents, etc.

[0020] FIG. 2 provides an illustration 200 of environmental loads that the FRP monopile 190 may be subjected to. As shown in the illustration 200, the FRP monopile 190 may be subjected to one or more of the six DOFs (heave, pitch, yaw, sway, pitch, roll) described above. The mooring device 150, in combination with the anchoring of the FRP monopile 190 to the seabed (e.g., by driving a first end of the FRP monopile 190 into the seabed), may restrain the FRP monopile 190 from being subjected to motion. This arrangement of the FRP monopile 190 may form a stiffness control structure for supporting a wind turbine. The FRP monopile-based structure implemented by the described systems and techniques may have an increased lateral stiffness, for example, up to 30,000 kN / m, which may be a substantial improvement over known systems and techniques, especially for structures supporting wind turbine payloads of 4,000 MT or less.

[0021] FIG. 2 further illustrates, in diagram 250, the relationship between the natural frequency and wave frequency of an exemplary FRP monopile implemented as described herein. As shown in diagram 250, the systems and techniques described herein, including the use of high tension mooring lines and related aspects described herein, may be used to implement an FRP monopile structure in which the wave frequency zone is substantially lower than the natural frequencies corresponding to the six DOFs. As shown in this diagram, the six natural frequencies of pitch, sway, heave, roll, pitch, and yaw all lie to the right of the significant wave frequency (peak in diagram 250) where the wave energy is greatest. Thus, an FRP monopile structure implemented in accordance with the present disclosure may experience minimal movement in both normal operating conditions and extreme conditions (e.g., storms).

[0022] Although the examples described herein may refer to FRP monopiles used as support structures for wind turbines, the disclosed FRP monopiles may be used to provide marine support for other objects, systems, and components, such as energy storage units, offshore substations, etc. Because the disclosed FRP monopiles are not payload sensitive, the FRP monopiles described herein may be scaled up and / or scaled down as needed to support objects having a wide range of masses.

[0023] As described throughout this disclosure, mooring lines may be used to provide additional stability to the FRP monopiles. Mooring lines may be arranged to maintain tension within a tension range in some instances. Over time, such mooring lines may sag due to dynamic forces (wind, waves, currents, etc.). This sagging may result in the tension of the mooring lines dropping outside of the design tension range, and thus the slackened mooring lines reduce their ability to mitigate movement in the six degrees of freedom. While re-tensioning systems and techniques have been successfully implemented in land-based applications and floating offshore platforms, these systems and techniques have not been successfully implemented in mooring lines used to stabilize fixed offshore structures.

[0024] For example, various systems and techniques available for re-tensioning floating structures typically involve large increases or decreases in tension, preventing fine tension adjustments often required with FRP monopile mooring lines. Various systems and techniques available for re-tensioning land-based structures typically use less robust stabilization components for land-based structures that are subject to low axial loads (e.g., low levels of movement in the six degrees of freedom). FRP monopile structures require stabilization systems and techniques that address the high axial loads such structures are subject to while providing finer tension adjustments. The FRP monopile structure stabilization systems and techniques described herein address these issues and provide a safer, easier, and more cost-effective means of adding and adjusting tension in the environments in which such structures are typically deployed.

[0025] FIGURE 3 illustrates a mooring system 300 for mitigating movement of an FRP monopile, according to various examples. The FRP monopile 310 is driven or otherwise attached to the seabed 380. At least a portion of the FRP monopile 310 may be below the waterline 370 and other portions may be above the waterline. The FRP monopile 310 illustrated in FIGURE 3 may be a transition piece (e.g., transition piece 130 of FIGURE 1), a monopile (e.g., monopile 140 of FIGURE 1), one or more other portions of an FRP monopile, or any combination thereof.

[0026] Mooring lines 340 may be used to mitigate forces or movements on FRP monopile 310. Note that in this example, one mooring line is shown for illustrative purposes, but typically multiple mooring lines and associated components may be installed on the FRP monopile. Mooring lines 340 may include mooring line segment 342 that is substantially above waterline 370, mooring line segment 346 that is substantially below waterline 370, and connector 344 that may connect mooring line segment 342 to mooring line segment 346 (in some examples, at or near waterline 370).

[0027] The use of these mooring line segments 342 and 346 and connector 344 facilitates ease of installation of mooring line 340. For example, anchor 350 may be driven or otherwise attached to the seabed 380 and lower mooring line segment 346 may be attached to anchor 350. Mooring line segment 346 may be later attached to upper mooring line segment 342 using connector 344 at a convenient time. For example, FRP monopile 310 and anchor 350 may be installed on independent schedules and mooring line 340 may be fully connected once both FRP monopile 310 and anchor 350 are installed.

[0028] A top mooring assembly (TMA) 320 may be secured or otherwise attached to the FRP monopile 310. In various examples, the TMA 320 may be attached to the FRP monopile 310 substantially above the waterline 370. The TMA 320 may include a mooring pouch 322 secured to the FRP monopile 310, which may directly support a load applied by tension in the mooring lines 340. The pouch 322 may be welded or otherwise permanently and irremovably secured to the FRP monopile 310. The TMA 320 may further include a stopper 324 to which the mooring lines 340 may be connected. The mooring lines 340 may be connected to the stopper 324 above the pouch 322 and pass through an opening in the pouch 322 and exit below the pouch 322. This opening may prevent the stopper 324 from passing through the pouch 322 (e.g., may be smaller than the dimensions of the stopper 324). By connecting the mooring line 340 to the stopper 324, the stopper 324 may be positioned to prevent the mooring line 340 from moving downwardly in the pouch 322. By applying a linear upward force to the stopper 324 (e.g., "pulling up" the stopper 324), the tension in the mooring line 340 may be increased. Detailed examples of techniques and systems for performing this tension increase are described herein.

[0029] In various examples, the installation procedure for mooring line system 300 may proceed as follows: anchor 350 (and in a typical example, multiple similar anchors) may be installed in the seabed 380. Such anchors may be driven into the seabed 380, dragged embedded, and / or otherwise installed using one or more other fixed anchor installation techniques. Mooring line segment 346 may then be attached to anchor 350 (and, in examples, other mooring lines may be similarly attached to other anchors). FRP monopile 310 may also be installed in the seabed 380 (e.g., driven into seabed 380). Because the installation of the anchor and FRP monopile are independent in this example, they may be installed in any order.

[0030] TMA 320 may be attached to FRP monopile 310 before or after FRP monopile 310 is installed on the seabed 380. Mooring line segment 342 may also be installed to TMA 320 at any point, and specifically may be connected to stopper 324 via pouch 322. Once FRP monopile 310 with TMA 320 and mooring line segment 342 in place is installed, mooring line segment 346 may be retrieved (e.g., from seabed 380) and connected to mooring line segment 342 via connector 344.

[0031] The tension of mooring line 340 (e.g., mooring line segments 342 and 346 connected via connector 344) may then be adjusted using TMA 320. In various examples, this tension may be increased or decreased by manipulation of stopper 324 after initial installation of mooring line 340. Thereafter, as needed, the tension may be similarly adjusted (e.g., using TMA 320, specifically by manipulating stopper 324) to maintain the tension of mooring line 340 within a desired or designed tension range. For example, a load cell may be placed at a point along mooring line 340 (e.g., as load cell or connector 344) and / or where mooring line 340 connects to stopper 324. This load cell may provide periodic, on-demand, and / or continuous tension monitoring to an operator who may then perform maintenance adjustments to the tension of mooring line 340 by manipulating TMA 320 as described herein.

[0032] FIGURE 4 illustrates a mooring line system 400 according to various examples. More specifically, FIGURE 4 illustrates a TMA 420, which represents a particular example of a TMA that may be used to maintain tension in the mooring lines. The TMA 420 may be installed on the FRP monopile 410, which may be any type of FRP monopile described herein or other marine structure. As with other examples described herein, a single mooring line and associated components are shown and described for illustrative purposes, although typically multiple mooring lines and associated components may be installed on the FRP monopile.

[0033] Mooring line 440 may include an upper mooring line segment 442 and a lower mooring line segment 446 connected to each other by a connector 444. In various examples, a load cell 450 may be disposed on mooring line 440 to detect and report tension measurements. Although shown in FIG. 4 as being disposed on upper mooring line segment 442, load cell 450 may be disposed at any point along mooring line 440 or at the end of mooring line 440. In some examples, mooring lines may be disposed with multiple load cells or without load cells.

[0034] Mooring line 440 may be connected to stopper 424 of TMA 420. TMA 420 may also include a pouch 422 positioned to support and restrain stopper 424 (and thus the tension provided by mooring line 440). Pouch 422 may include a cavity, recess, or other section 426 in which stopper 424 may be seated or engaged.

[0035] The stopper may be connected to and operated by a tension cable 434 disposed on the pulley 430. The pulley 430 and associated components may be installed and used for initial installation and tensioning of the mooring line 440 and removed after installation. Alternatively or additionally, the pulley 430 and associated components may be installed from time to time, as needed, to adjust tension in the mooring line 440. For example, the pulley 430 may be disposed with a hook 432 that may be connected to an eye 412 disposed on the FRP monopile 410. Using this hook and eye arrangement, the pulley 430 may be quickly and easily installed and removed, as needed. In other examples, the pulley 430 may be permanently fixed to the FRP monopile 410 and / or the TMA 420.

[0036] The tension in the mooring lines may be increased by pulling the tension cable 434. For example, the tension cable 434 may be pulled from below by a boat or other means positioned near the FRP monopile 410 at the sea surface (shown by solid line 434). Alternatively, the tension cable 434 may be pulled from above by a crane (e.g., located on a vessel) or other means positioned near the FRP monopile 410 above the pulley 430 (shown by dashed line 434). Once the appropriate tension has been applied to the mooring lines 440, the stopper may be locked into place (e.g., as described in more detailed examples herein). In some examples, the pulley 430 and associated components may then be removed from the FRP monopile 410.

[0037] In various examples, installation and use of the pulley 430 to tension the mooring line 440 may proceed as follows: The hook 432 of the pulley 430 may be attached to the eye 412 of the FRP monopile 410. The tension cable 434 may then be connected to the stopper 424. The tension cable 434 may be pulled (e.g., from above, below, or horizontally) using a boat, crane, or other means. This pulling will change the position of the stopper 424 relative to the porch 422. While the tension cable 434 is being pulled, the tension in the mooring line 440 may be monitored (e.g., using a load cell 450). Once the desired tension is achieved by pulling the tension cable 434, the stopper 424 may be locked in place (e.g., using one or more techniques described herein) at its current position. In some examples, once the stopper 424 is secured in place while maintaining a desired tension on the mooring line 440, the tension cable 434 can be disconnected from the stopper 424 and the pulley 430 and associated components can be removed from the FRP monopile 410.

[0038] Various systems and techniques are disclosed herein for maintaining the position of the stopper relative to the pouch to maintain tension in the mooring line. FIG. 5 illustrates a system 500, which may include an exemplary TMA 520, in which some of such systems and techniques may be implemented. The TMA 520 may include a stopper 524 and a pouch 522. The stopper 524 may be connected to a mooring line 540 that passes through an opening 523 in the pouch 522. The mooring line 540 may include an upper mooring line segment 542 and a lower mooring line segment 546 connected by a connector 544. The upper mooring line segment 542 and / or the connector 544 may be connected to the stopper 524 using a coupling component that may be adjustable in length and / or adjustable in length. The upper mooring line segment 542 may be connected to the stopper 524 using a hook positioned to connect to an eye positioned in the stopper 524.

[0039] Stopper 524 may include eye 526 and / or other means for connecting to a stopper manipulation component. In this example, tension cable 534 of pulley 530 may be connected to eye 526, although any other means of moving, repositioning, or manipulating the position of stopper 524 may be used. The position of stopper 524 may be adjusted relative to pouch 522 (e.g., by pulling tension cable 534 of pulley 530) until the tension in mooring line 540 is within a desired tension range.

[0040] When the stopper 524 is in the desired position, one or more gaskets 528 can be inserted between the stopper 524 and the pouch 522 to maintain the position of the stopper 524 relative to the pouch 522. For example, the gasket 528 can be approximately the same width as the distance between the stopper 524 and the pouch 522 when the stopper 524 is in the desired position. By inserting a gasket 528 of this width, the stopper 524 can be released from the tensioning component (e.g., pulley 530) and remain in the desired position. Gaskets such as gasket 528 can be pre-manufactured in various widths, such that various distances between the stopper and the pouch can be positioned using such gaskets. In some instances, multiple gaskets can be used to maintain this distance. Gaskets can be added gradually to the TMA as the distance between the stopper and the pouch increases over time due to tensioning of the mooring lines. Other stopper retention components, including those described herein, can also or instead be used to maintain the stopper in a particular position relative to the pouch. For example, any suitable type and / or size washer may also or alternatively be used to maintain the stopper in a particular position relative to the pouch.

[0041] 6 illustrates a system 600 that may include an exemplary TMA 620 in which several systems and techniques for maintaining the position of the stopper may be implemented. The TMA 620 may include a stopper 624 and a pouch 622. The stopper 624 may be connected to a mooring line 640, which may include an upper mooring line segment 642 and a lower mooring line segment 646 connected by a connector 644. The upper mooring line segment 642 and / or the connector 644 may be adjustable in length and / or may be connected to the stopper 624 using a coupling component that may be adjustable in length. The upper mooring line segment 642 may connect to the stopper 624 using a hook positioned to connect to an eye positioned in the stopper 624 (e.g., at the bottom of the threaded portion 627).

[0042] In this example, the stopper 624 may resemble a bolt with a stopper head 623 positioned on and in engagement with the pouch 622 and a threaded portion 627 that may extend through the pouch 622. The stopper 624 may also include an eye 626 that may be connected to a stopper position manipulation component, such as a pulley (not shown in FIG. 6). The mooring line 640 may be connected to the bottom of the threaded portion 627 or may extend through the threaded portion 627 and connect to the stopper head 623.

[0043] In this example, a gasket 628 may be used to maintain the distance between the head 623 of the stopper 624 and the pouch 622. The stopper 624 may be repositioned using techniques described herein until the tension in the mooring line 640 is within the desired tension range. When the stopper 624 is in the desired position, one or more gaskets 628 may be installed between the head 623 and the pouch 622 to maintain the position of the head 623 relative to the pouch 622. For example, the gasket 628 may be approximately the same width as the distance between the head 623 and the pouch 622 when the stopper 624 is in the desired position. By inserting a gasket 628 of this width, the stopper 624 may be released from the tensioning component (e.g., a pulley) and remain in the desired position. Again, gaskets such as gasket 628 are pre-manufactured in various widths, so that the distance between the stopper or stopper head and the pouch may be positioned using such gaskets. In some examples, multiple gaskets may be used to maintain this distance. As the distance between the stopper or stopper head and the pouch increases over time due to tensioning of the mooring lines, gaskets may be added incrementally to the TMA. As previously mentioned, washers of any suitable type and / or size may also or instead be used to maintain the stopper in a particular position relative to the pouch.

[0044] To secure the stopper 624 in its current position, a nut 625 may be threaded onto the threaded portion 627 of the stopper 624. The nut 625 is threaded down to the bottom of the pouch 622, securing the stopper 624 in place. Alternatively, a washer or other gasket 629, for example, may be placed between the nut 625 and the bottom of the pouch 622 to ensure durable positioning of the nut 625. The use of a nut in the TMA arrangement may provide additional positional security for the stopper beyond just the tension provided by the mooring line. In various examples, the bolt and nut arrangement of the TMA 620 facilitates ease of installation by allowing adjustment (or removal) of the nut 625 and allowing the stopper 624 to be lowered towards the mooring line 640, facilitating attachment of the mooring line 640 to the stopper 624. The nut 625 may then be coupled to and / or tightened onto the stopper 624 to increase the tension in the mooring line 640 after connection to the stopper 624 .

[0045] 7 illustrates a system 700 for attaching a mooring line segment 742 to a stopper 724. The mooring line segment 742 is an upper mooring line segment and may connect to a connector 744 which may be connected to a lower mooring line segment (not shown) as described herein.

[0046] In this example, a fitting 730 may be disposed within the stopper 724 that may secure the mooring line segment 742 within the stopper 724. The mooring line segment 742 may pass through an opening 723 at the bottom of the stopper 724 to connect to a connector 744. The fitting 730 may further be secured to an eye 726 that may pass through or be accessible through an opening 725 at the top of the stopper 724. The placement of the fitting 730 within the stopper 724 to secure the mooring line segment 742 to the eye 726 allows for tensioning of the eye 726, resulting in tensioning the mooring line segment 742 with the stopper 724.

[0047] FIG. 8 illustrates a tensioning system 800 that may implement a bolt and nut tensioning technique (e.g., as opposed to a pulley system) using a TMA 820. The TMA 820 may include a stopper 824 and a pouch 822. In this example, the stopper 824 may resemble a bolt with a stopper head 823 positioned above and / or to engage the pouch 822 and a threaded portion 827 that may extend through the pouch 822. The stopper 824 may also include an eye 826 that may be connected to a stopper position manipulation component, such as a pulley (not shown in FIG. 8). A mooring line segment 842 may be connected to the bottom of the threaded portion 827 at an eye 828 (e.g., using a hook attached to the end of the mooring line segment 842) or may extend through the threaded portion 827 and connect to the stopper head 823. Mooring line segment 842 may be an upper mooring line segment and may connect to a connector 844 which may be connected to a lower mooring line segment (not shown) as described herein.

[0048] In this example, top nut 825 and bottom nut 829 may be used to secure stopper 824 in a desired position and maintain the distance between head 823 of stopper 824 and pouch 822. To reposition stopper 824, nuts 825 and 829 may be loosened (e.g., adjusted away from pouch 822) and stopper 824 may be repositioned using techniques described herein until the tension in the mooring line is within the desired tension range. In some examples, bottom nut 829 may be removed from threaded portion 827 for tensioning operations. Once stopper 824 is in the desired position, nuts 825 and / or 829 may be tightened (e.g., adjusted to compress pouch 822) to maintain the position of head 823 relative to pouch 822. Alternatively, the position of stopper 824 may be adjusted by rotating stopper 824 within nuts 825 and 829 and moving head 823 of stopper 824 up or down relative to pouch 822. Nuts 825 and 829 can be tightened to secure stopper 824 in place. In this arrangement, top nut 825 serves to maintain the position of stopper 824 relative to pouch 822, while bottom nut 829 serves to further secure stopper 824 in place. In this example, tension in the mooring line is counterbalanced by top nut 825, reducing tension on the threads of threaded portion 827.

[0049] In various examples, the bolt and nut arrangement of TMA 820 facilitates ease of installation by allowing adjustment (or removal) of nut 825 and / or nut 829, allowing stopper 824 to be lowered towards mooring line segment 842, and facilitating attachment of mooring line segment 842 to stopper 824. Nut 825 and / or 829 may then be coupled to and / or tightened against stopper 824 to increase tension in mooring line segment 842 after connection to stopper 824.

[0050] 9 illustrates a mooring system 900 for mitigating movement of an FRP monopile, according to various examples. The FRP monopile 910 may be driven or otherwise attached to the seabed 980. At least a portion of the FRP monopile 910 may be below the waterline 970 and other portions may be above the waterline. The FRP monopile 910 illustrated in FIG. 9 may be a transition piece (e.g., transition piece 130 of FIG. 1), a monopile (e.g., monopile 140 of FIG. 1), one or more other portions of an FRP monopile, or any combination thereof.

[0051] Mooring lines 940 may be used to mitigate forces or movements on the FRP monopile 910. Again, one mooring line is shown for illustration purposes, however, typically multiple mooring lines and associated components may be installed on the FRP monopile. Mooring lines 940 may include one or more segments, connectors, and / or load cells, as described herein. Mooring lines 940 may be connected to anchors 950, which may be driven into or attached to the seabed 980.

[0052] The TMA 920 may be fixed or otherwise attached to the FRP monopile 910. The TMA 920 may include a mooring pouch 922 fixed to the FRP monopile 910 and a stopper 924 to which the mooring line 940 may be connected. In this example, the pouch 922 may be positioned such that its bottom surface may be perpendicular 921 to the starting angle of the mooring line 940, as shown in this figure. To maintain this orientation, the pouch 922 may be rotatably fixed to the FRP monopile 910, such that the pouch 922 may rotate about a horizontal axis (e.g., within a limited range of motion, up to 30 degrees, up to 60 degrees). In various examples, the installation procedure for the mooring line system 900 may be similar to the installation procedure for the system 300 described above with reference to FIG. 3. The various tensioning systems and techniques described herein may also be applied to the system 300 of FIG. 3.

[0053] FIG. 10 illustrates a tensioning system 1000 that may include an exemplary TMA 1020. The TMA 1020 may include a stopper 1024 and a pouch 1022. The stopper 1024 may be connected to a mooring line segment 1046, which may be an upper mooring line segment of a mooring line, as described herein. The mooring line segment 1046 may extend through an opening in the pouch 1022 and connect to a fitting 1042 that secures the mooring line segment 1046 to the stopper 1024. In some examples, the load cell 1090 may be disposed between the fitting 1042 and the mooring line segment 1046. Alternatively, the fitting 1042 may directly connect the mooring line segment 1046 to the stopper 1024. In examples, the fitting 1042 may be adjustable (e.g., in length) to facilitate installation of the mooring line segment 1046. The mooring line segment 1046 and / or the fitting 1042 may be adjustable in length and / or a coupling component that may be adjustable in length may be used to connect the mooring line segment 1046 to the fitting 1042. The fitting 1042 may include an eye that may be positioned to receive a hook positioned on an end of the mooring line segment 1046, which may be used to connect the mooring line segment 1046 to the fitting 1042.

[0054] In this example, a "pushing" force, rather than a pulling force used to manipulate the position of the stopper 1024, may be used to increase the distance between the stopper 1024 and the pouch 1022. In an example, one or more hydraulic cylinders may be used to increase the distance between the stopper 1024 and the pouch 1022. For example, hydraulic cylinder 1082 and hydraulic cylinder 1084 may be removably positioned between the stopper 1024 and the pouch 1022. The hydraulic cylinders 1082 and 1084 may be controlled by a hydraulic power unit (HPU) 1080, which may increase or decrease hydraulic pressure in each cylinder 1082 and 1084. The HPU 1080 may control the hydraulic cylinders 1082 and 1084 using connections 1081 and 1083, respectively. Connections 1081 and 1083 may be hoses or any other type (e.g., flexible) conduits of any type of hydraulic fluid. In various examples, one or more hydraulic cylinders, such as hydraulic cylinders 1082 and 1084, may be integrated into a stopper, such as stopper 1024, and / or may be fixed or disposed (e.g., permanently or semi-permanently) to the stopper.

[0055] The hydraulic cylinders 1082 and 1084 may initially have a relatively low or no hydraulic pressure and thus may have dimensions that allow them to be disposed between the stopper 1024 and the pouch 1022. The HPU 1080 may be operated to increase the hydraulic pressure of the hydraulic cylinders 1082 and 1084 until their respective dimensions increase (e.g., vertically relative to the longitudinal axis of the mooring line segment 1046 or parallel to the sloping side of the pouch, such as pouch 922 shown in FIG. 9), raising the position of the stopper 1024 relative to the pouch 1022 and increasing the distance between the stopper 1024 and the pouch 1022. This will in turn increase the tension in the mooring line associated with the mooring line segment 1046. The pressure in the cylinders may be increased by the HPU 1080 until it is within a desired tension range.

[0056] When the stopper 1024 is in the desired position, one or more washers or gaskets 1028 may be inserted between the stopper 1024 and the pouch 1022 to maintain the position of the stopper 1024 relative to the pouch 1022. For example, the washer 1028 may be approximately the same width as the distance between the stopper 1024 and the pouch 1022 when the stopper 1024 is in the desired position. After inserting a washer 1028 of this width, the HPU 1080 may be operated to reduce the hydraulic pressure in the hydraulic cylinders 1082 and 1084 until the hydraulic cylinders 1082 and 1084 may be removed from between the stopper 1024 and the pouch 1022. The washer 1028 may maintain the stopper 1024 in the desired position. Note that one or more washers or gaskets may also be removed when the stopper 1024 is in the desired position. For example, the thinner washer can be removed and a thicker washer can be inserted between the stopper 1024 and the pouch 1022 .

[0057] As with other gaskets described herein, washers or gaskets such as washer 1028 may be pre-manufactured in various widths so that various distances may be placed between the stopper and the pouch using such washers. Washers according to the disclosed examples may include various marks and / or indentations that may facilitate placement and / or removal (e.g., with a specific tool). As with other examples described herein, in the hydraulic cylinder tensioning example, multiple washers may be used to maintain the distance between the pouch and the stopper. Washers or gaskets may be added incrementally to the TMA as the distance between the stopper and the pouch increases over time due to tensioning of the mooring lines.

[0058] FIG. 11 illustrates a tensioning system 1100 that may include an exemplary TMA 1120. The TMA 1120 may include a bolt-type stopper having two or more components, including a fixed stopper component 1185 and a bolt-type stopper 1124. The TMA 1120 may also include a pouch 1122. The fixed stopper component 1185 may be seated on an upper side of the pouch 1122 and may be fixed (e.g., may not move during a tensioning operation). In various examples, the fixed stopper component 1185 may surround the stopper 1124 and other components coupled to and / or otherwise disposed near the stopper 1124. Alternatively or additionally, the fixed stopper component 1185 may substantially hold other parts coupled to and / or otherwise disposed near the stopper 1124 in a predetermined position (e.g., laterally). The stopper 1124 may extend through the fixed stopper component 1185 and the pouch 1122 and may be disposed with an eye 1148 or other coupling component at the bottom of the stopper 1124 that may be connected to the mooring line segment 1146. The stopper 1124 may be adjustable or otherwise movable or repositionable (e.g., may move during a tensioning operation). The fixed stopper component 1185 may include one or more openings or holes that allow for connection through the fixed stopper component 1185 to components within the fixed stopper component 1185. For example, a nozzle 1187 may extend through the fixed stopper component 1185 to allow for (e.g., hydraulic) connection to a hydraulic component within the fixed stopper component 1185 (e.g., connection of the HPU 1180 using connection 1181 via nozzle 1187 to hydraulic component 1182).

[0059] Mooring line segment 1146 may be an upper mooring line segment of a mooring line described herein. Alternatively, mooring line segment 1146 may refer to a single segment (e.g., one piece) of mooring line. Eye 1148 may directly connect mooring line segment 1146 to stopper 1124, for example, using a hook disposed on the end of mooring line segment 1146. In an example, eye 1148 may refer to a coupling component that may be adjustable (e.g., in length) to facilitate attachment and tension adjustment to mooring line segment 1146.

[0060] The TMA 1120 may use the pushing force to manipulate the position of the stopper 1224 to increase the distance between the stopper 1124 and the pouch 1222. In an example, one or more hydraulic cylinders and / or other hydraulic components may be used to increase the distance between the stopper 1124 and the pouch 1122. For example, hydraulic component 1182 may refer to any number of hydraulic cylinders and / or other hydraulic components that may be disposed (e.g., removably or non-removably) between the stopper 1124 and the pouch 1122. The hydraulic component 1182 may be controlled by the HPU 1180, which may increase or decrease the hydraulic pressure in the hydraulic component 1182 using connections 1181, which may refer to any number and types of hydraulic connections, such as one or more hoses or other types (e.g., flexible) of any type of hydraulic fluid. In various examples, the hydraulic components 1182 may be integrated into the TMA 1120 and / or may be fixed or disposed (eg, permanently or semi-permanently) to the TMA 1120.

[0061] Similar to the procedure used in the system of Figure 10, the hydraulic component 1182 may be operated to increase hydraulic pressure in such component, raising the position of the stopper 1124 relative to the pouch 1122, thereby increasing the distance between the stopper 1124 and the pouch 1122 and therefore the tension in the mooring line associated with the mooring line segment 1146. During this operation, the fixed stopper component 1185 may remain fixed and stationary, allowing the position of the stopper 1124 to be adjusted. Pressure in the hydraulic component 1182 may be increased until the mooring line is within the desired tension range.

[0062] When the stopper 1124 is in the desired position, one or more washers or gaskets 1128 may be inserted between the stopper 1124 and the pouch 1122 to maintain the position of the stopper 1124 relative to the pouch 1122. For example, the washer 1128 may be approximately the same width as the distance between the stopper 1124 and the pouch 1122 when the stopper 1124 is in the desired position. After inserting a washer 1128 of this width, the HPU 1180 may be operated to reduce hydraulic pressure in the hydraulic components 1182 until the hydraulic components are needed to readjust the tension in the mooring lines or, in some instances, such components may be removed. The washer 1128 may maintain the stopper 1124 in the desired position. Again, when the stopper 1124 is in the desired position, one or more washers or gaskets may be removed. For example, a thinner washer may be removed and a thicker washer may be inserted between the stopper 1124 and the pouch 1122.

[0063] As with other nut and bolt type TMAs, as described herein, in examples, the nut 1123 may also be used to secure the stopper 1124 in place. In some examples, the bolt type stopper 1124 may not be threaded or may be threaded only in one portion. For example, the stopper 1124 may be threaded in a portion of the stopper 1124 that mates with the nut 1123, but not in other portions.

[0064] In various examples, the bolt and nut arrangement of the TMA 1120 facilitates ease of installation of the mooring line by allowing adjustment (or removal) of the nut 1123 to allow the stopper 1124 to be lowered towards the mooring line segment 1146, facilitating installation of the mooring line segment 1146 to the stopper 1124. The nut 1123 may then be coupled to and / or tightened to the stopper 1124 to increase tension in the mooring line segment 1146 after connection to the stopper 1124.

[0065] In various examples, the TMA may be disposed with a protective cover or other enclosure that may help protect the TMA from environmental conditions, thereby extending the life of the TMA's components. For example, the TMA 1120 may be disposed with a cover 1192 that may substantially enclose the components of the TMA 1120, such as the stopper 1124, the hydraulic components 1182, the washer 1128, and / or portions of the pouch 1122. A protective cover or enclosure, such as the cover 1192, may include access components, such as the nozzle 1187, that may allow the connection 1181 from the HPU 1180 to access the hydraulic components 1182. The cover 1192 may be made of any suitable insulating material and / or combination of materials. A cover, such as the cover 1192, may help insulate the TMA 1120 and / or its components from extreme temperatures and protect such components from moisture and other environmental elements that may otherwise accelerate the degradation of such components.

[0066] As with other gaskets described herein, washers or gaskets such as washer 1128 may be pre-manufactured in various widths so that various distances between the stopper and pouch can be positioned using such washers. Washers according to the disclosed examples may include various marks and / or indentations to facilitate placement and / or removal (e.g., with a specific tool). As with other examples described herein, in the hydraulic cylinder tensioning example, multiple washers may be used to maintain the distance between the pouch and stopper. Washers or gaskets may be added incrementally to the TMA as the distance between the stopper and pouch increases over time due to tensioning of the mooring lines.

[0067] The hydraulic tensioning systems and techniques described herein may be used during initial installation of one or more mooring lines and / or for re-tensioning operations. Other means disclosed herein may also or instead be used to maintain the position of the stopper. For example, where one or more nuts may be used to secure the position of the stopper (e.g., rather than or in addition to one or more washers or gaskets; see, e.g., FIGS. 6, 8, 11 and associated text), one or more hydraulic cylinders may be used to position the stopper within a nut-and-bolt type TMA. Note that in other examples, one or more hydraulic cylinders may be used to "push" the stopper away from the pouch. All such cylinders may be controlled by a single HPU, and multiple HPUs may be used to control a subset of such cylinders. In this example, and other washer and gasket examples described herein, the washers and / or gaskets may be inserted from the side of the TMA between the stopper and the pouch. Such washers and / or gaskets may be constructed in multiple separable segments to facilitate ease of installation.

[0068] As previously mentioned, multiple mooring lines may be used to help resist 6 DOF movements imposed by environmental forces on an FRP monopile or other fixed marine structure. FIG. 12 shows an example of a structure 1200 that may be secured using multiple mooring lines 1204. In various examples, two or more mooring lines may be secured to a single anchor. In this example, two mooring lines may be attached to each of the individual anchors 1203. The mooring lines secured to a particular anchor may form a group of mooring lines. There may be any number of mooring lines associated with a group of mooring lines. Any number of groups may be connected to the structure. In this example, there are three groups of mooring lines 1204 connected to the structure 1200.

[0069] The mooring lines in each mooring line group may be connected to the structure in close proximity to one another. For example, each mooring line 1204 in a separate group of mooring lines may connect to a separate TMA disposed on the structure 1200 in close proximity to another TMA used to connect to another mooring line in the same mooring line group.

[0070] Each of a plurality of mooring lines used to stabilize a structure may have the same or substantially similar length, departure angle (from the structure), and / or initial tension. The initial tension or tension range of such lines may be determined to provide little or no lateral loading on the structure. The tension of the mooring lines may be within a range in which the structure may continue to experience elastic resistance from the soil in which the anchors may be attached (e.g., there may be minimal, if any, plastic deformation). In an example, based on these conditions, an individual mooring line may be fully pretensioned to a design value (or a value within a desired tension range) in a single tensioning operation.

[0071] Mooring lines, or groups of mooring lines, may be distributed symmetrically around the perimeter of a fixed marine structure. FIG. 13 shows some non-limiting examples of such arrangements. In arrangement 1310, a fixed marine structure 1312 may be secured by three groups 1311 of mooring lines. Each of the groups 1311 of mooring lines may have any number of mooring lines. Each mooring line in the group 1311 of mooring lines may be connected to a single anchor and may connect to the structure 1312 substantially evenly (e.g., with a separation angle of substantially 120 degrees) around the perimeter of the structure 1312, with TMAs proximate to other TMAs connecting other mooring lines.

[0072] In arrangement 1320, a fixed marine structure 1322 may be secured by four groups 1321 of mooring lines. Again, each of the groups 1321 of mooring lines may have any number of mooring lines, each mooring line in a group may be connected to a single anchor, and each mooring line in a group may connect to the structure 1322 with a TMA that is proximate to other TMAs that connect other mooring lines in the same group. As shown here, the four mooring line groups 1321 may be distributed substantially evenly (e.g., with a separation angle of substantially 90 degrees) around the circumference of the structure 1322.

[0073] In another example arrangement 1330, a fixed marine structure 1332 may be secured by five mooring line groups 1331. Again, each of the mooring line groups 1331 may have any number of mooring lines, each mooring line in the group may be connected to a single anchor, and each mooring line in the group may connect to the structure 1332 with a TMA that is proximate to other TMAs that connect other mooring lines in the same group. As shown here, the five mooring line groups 1331 may be distributed substantially evenly (e.g., with an angle of separation of approximately 72 degrees) around the circumference of the structure 1332.

[0074] Any other arrangements and distributions of mooring lines and mooring line groups that may be used are considered to be within the scope of this disclosure. Additionally, any of the tensioning systems, TMAs, mooring lines, and related components and techniques described may be used interchangeably. For example, any of the hydraulic and pulley tensioning techniques may be used in conjunction with any of the stopper position fixing techniques, etc. described herein. Any combination of the various systems, components, techniques, and subsets thereof are considered to be within the scope of this disclosure.

[0075] Based on the above, it should be appreciated that techniques for minimizing motion of a fixed marine structure that may support a wind turbine have been presented herein. The above subject matter is provided by way of example only and should not be construed as limiting. Moreover, the claimed subject matter is not limited to implementations that solve some or all of the disadvantages noted in any part of this disclosure. Various modifications and changes may be made to the subject matter described herein without following the examples and applications shown and described and without departing from the true spirit and scope of the invention as set forth in the following claims.

Claims

1. a fixed offshore platform for mounting the wind turbine; a mooring pouch coupled to the fixed offshore platform; a stopper configured to engage the anchoring pouch; An anchor attached to the seabed; a mooring line extending through the mooring pouch, the mooring line having a first end coupled to the anchor and a second end coupled to the stopper; A hydraulic power unit; one or more hydraulic cylinders coupled to the hydraulic power unit and disposed between the stopper and the mooring pouch, the one or more hydraulic cylinders configured to expand under control of the hydraulic power unit to increase a distance between the stopper and the mooring pouch; and one or more stopper retaining components configured to secure the stopper in position relative to the mooring pouch.

2. 2. The system of claim 1, wherein the fixed offshore platform comprises a fully restrained platform monopile embedded in the seabed.

3. 3. The system of claim 2, wherein the ocean floor is at a depth of about 50 meters to 200 meters below the water surface.

4. 2. The system of claim 1, wherein the one or more stopper retaining components comprise a washer disposed between the stopper and the anchoring pouch and through a side of the stopper and the anchoring pouch.

5. 2. The system of claim 1, wherein the stopper comprises a threaded portion extending through an opening disposed in the anchoring pouch.

6. 6. The system of claim 5, wherein the one or more stopper retaining components comprises a nut disposed around the threads and on top of the anchoring pouch.

7. 6. The system of claim 5, further comprising a nut disposed around the threaded portion and underneath the anchoring pouch.

8. 10. The system of claim 1, further comprising a load cell configured to measure tension in the mooring line.

9. 2. The system of claim 1, wherein the first end of the mooring line is coupled to the stopper by a length-adjustable coupling component.

10. 2. The system of claim 1, wherein the mooring line comprises a first segment having the first end, a second segment having the second end, and a connector connecting the first segment and the second segment.

11. A fixed marine structure, comprising:

1. A mooring assembly, the mooring assembly comprising: A mooring pouch; a stopper configured to receive a mooring line attached to an anchor attached to the seabed and engage the mooring pouch; a tensioning component configured to increase tension in the mooring lines by increasing the distance between the stopper and the mooring pouch.

12. 12. The fixed offshore structure of claim 11, comprising a first end embedded in the seabed and a second end configured to support a wind turbine.

13. The fixed marine structure according to claim 11, further comprising: a wind tower configured to support a wind turbine; a monopile attached to the seabed; and A fixed offshore structure comprising: a transition piece connecting the wind tower and the monopile.

14. 12. The fixed offshore structure of claim 11 , wherein the tensioning component comprises one or more hydraulic cylinders disposed between the stopper and the mooring pouch, the one or more hydraulic cylinders configured to increase the distance between the stopper and the mooring pouch by pushing the stopper away from the mooring pouch.

15. 12. The fixed offshore structure of claim 11, wherein the tensioning component comprises a pulley system configured to increase the distance between the stopper and the mooring pouch by pulling the stopper away from the mooring pouch.

16. 1. A method of restraining movement of a platform mounting a wind turbine, the method comprising: attaching a mooring line, which is anchored to the seabed, to a mooring assembly attached to the platform, the mooring assembly including a mooring pouch configured to receive the mooring line and a stopper; attaching a tensioning component to the stopper, the tensioning component configured to increase a distance between the stopper and the anchoring pouch; moving the stopper from a first position to a second position by increasing the distance between the stopper and the anchoring pouch using the tensioning component; fixing the stopper in the second position; and removing the tensioning component from the stopper.

17. 17. The method of claim 16, wherein fixing the stopper in the second position includes inserting one or more washers between the stopper and the anchoring pouch to hold the stopper in the second position.

18. 17. The method of claim 16, wherein the step of fixing the stopper in the second position includes disposing a nut around the threaded portion of the stopper and in contact with a top of the anchoring pouch.

19. 17. The method of claim 16, further comprising attaching a plurality of mooring lines to the platform, the plurality of mooring lines being distributed substantially evenly around a perimeter of the platform.

20. 17. The method of claim 16, further comprising attaching a second mooring line secured to the seabed to a second mooring assembly mounted to the platform, the mooring line and the second mooring line being attached to the same anchor mounted to the seabed.

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