Anchoring method and apparatus

Abstract

The present invention relates to an apparatus and method for embedding plate anchors. The method uses multiple embedding modules, each suitable for embedding a plate anchor in a different soil type. The method involves determining the type of soil at a target location on the seabed based on the type of soil at the target location, and selecting an embedding module. The embedding module is removably mounted within a modular follower device. The modular follower device is deployed from an installation vessel, the embedding module is activated, and the plate anchor is driven into the seabed. The modular follower device is then returned to the installation vessel. The modular follower device is then reconfigured for subsequent deployment by installing a different embedding module in the modular follower device to embed yet another plate anchor in a different soil type.

Description

[Technical Field]

[0001] The present invention relates to a plate anchor embedding method and a plate anchor embedding device. [Background technology]

[0002] Floating offshore wind turbines (FOWTs) are envisioned as a viable solution for offshore wind farms in deep coastal waters where fixed structures become uneconomic. A significant cost component of FOWTs is the mooring / anchoring system used to hold the structure in place. A large portion of the mooring cost is that of the anchors.

[0003] The oil and gas industry has used multiple rows of mooring lines to hold floating structures to their base since the 1960s. While a typical oil and gas development might use 8-12 mooring lines, a large wind farm can have hundreds of mooring lines and corresponding anchors. Floating wind farms require a large number of anchors. This means that reducing anchoring costs has a significant benefit on the overall economics of floating wind farm development and the final cost to users of the generated electricity.

[0004] Plate anchors are widely considered to be the most efficient anchors in terms of material usage. Generally, when constructed from high-strength steel and buried deep below the seabed where soil strength is greatest, plate anchors have a holding capacity to weight ratio that exceeds all other anchor types, such as drag anchors and piles. They use less material compared to other anchor types, which translates into savings in material and transportation costs. In addition to monetary cost savings, plate anchors also reduce carbon emissions, which manifests itself as reduced steel production and reduced shipping weight and size.

[0005] Although plate anchors are highly efficient once installed, burying them deeply can be challenging and time-consuming depending on the soil conditions. The FOWT industry needs to address the challenges posed by difficult soil conditions and reduce the time required to install plate anchors.

[0006] Suction embedment (see, for example, U.S. Patents 5,992,060 and 6,122,847) is often used to install plate anchors in soft, deep-sea clays. In the case of stiff clays, silt, or sand, suction embedment may not be feasible. It is feasible to embed small plate anchors in sand by explosive force, impact driving, vibration driving, and jetting. Experience and theory suggest that the embedment method can be adapted to suit the soil type. For example, suction embedment works well in soft to medium clays, while vibro driving works well in sands, etc.

[0007] Many proposed wind turbines are located in areas with stratified soil layers with different or varied soil types throughout the turbine range. Therefore, a single burial method and burial device may not be efficient or feasible. In such cases, multiple different types of driving devices may be prepared to perform different burial methods as needed, and the driving devices may be retrieved and used to burial different soil layers.

[0008] It is an object of the present invention to overcome at least one of the problems of the prior art identified herein or elsewhere. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 5,992,060 [Patent Document 2] U.S. Patent No. 6,122,847 Summary of the Invention

[0010] A first aspect of the present invention is A method for embedding a plate anchor, comprising: When burying plate anchors in different types of soil, multiple burial modules suitable for each type of burial are prepared, determining the type of seabed soil at the target location; Selecting a buried module based on the soil type at the target location; releasably mounting the embedded module within a modular follower device; deploying the modular follower device from a vessel; activating the embedding module to drive the plate anchor into the seabed; Retrieving the modular follower apparatus to the vessel and subsequently reconfiguring the modular follower apparatus by adding another embedded module to the modular follower apparatus for subsequent deployment. The present invention relates to a method for embedding a plate anchor.

[0011] Preferably, the method includes retaining a first plate anchor within the modular follower device and burying the first plate anchor at a first destination, retrieving the modular follower device, reconfiguring the buried modules within the modular follower device, retaining another plate anchor within the modular follower device and burying the still another plate anchor at a second destination. Preferably, the method includes burying a plurality of plate anchors to provide tethering points for a floating structure, preferably a floating offshore wind turbine.

[0012] The method includes: deploying the follower device at a first deployment time and burying one or more plate anchors with the follower device in a first configuration; The follower device is recovered onto an installation vessel (or work vessel; the same applies hereinafter), reconfiguring the follower device to provide a different embedded module in the follower device; and The follower device can then be deployed to embed one or more additional plate anchors.

[0013] The method includes deploying and retrieving the follower device any number of times (two or more times) and / or in a first series (a first batch) while maintaining the configuration of the follower device. The method further includes reconfiguring the follower device to provide a different embedment module, deploying the follower device, and embedding at least one additional plate anchor. The method further includes deploying and retrieving the follower device any number of times (two or more times) and / or in a second series (a second batch) while maintaining an additional configuration different from the initial configuration of the follower device used in the first series.

[0014] The method includes deploying the follower device during a first deployment and burying a first plate anchor together with the follower device in a first configuration; Retrieving the follower device to an installation vessel; reconfiguring the follower device to provide a different embedded module in the follower device; and The follower device can then be deployed to install a second plate anchor.

[0015] In this method, the follower device can be retracted after each plate anchor is embedded. Although the configuration of the embedding modules within the follower device can be changed after each plate anchor is embedded, it is preferred to change the embedding modules only after a number of plate anchors are embedded.

[0016] In this method, the follower device can only be retrieved after a number of plate anchors have been embedded.

[0017] The method can install multiple plate anchors on the seabed. The method can include securing the plate anchors within the follower devices while the plate anchors and follower devices are located on the seabed. The method preferably includes manipulating the plate anchors on the seabed before securing the plate anchors to the follower devices.

[0018] Preferably, the method identifies layers and / or strata (e.g., layers of different types of soil) within the seabed. The method can include attaching one or more embedded modules to the follower device and driving them into the identified layers and / or strata within the seabed. The method can include attaching a specific embedded module and driving it into a specific layer or strata within the seabed.

[0019] The method can include providing a first embedded module for the first layer or formation and providing a second embedded module for the second layer or formation.

[0020] In this method, the modular follower device can be used in conjunction with burial modules to drive into multiple layers / formations of the seabed. For example, the seabed may be composed of layers / formations of soil, each with different soil types and / or properties. Each of these soil types and / or properties may require a different burial module / means.

[0021] In this method, Vibro hammer buried module, Impact hammer buried module, Suction buried module, and Preferably, one or more buried modules are selected and installed among the jetting modules.

[0022] The method may involve removing and / or installing one or more of the following embedded modules during successive deployments of the modular follower device: Vibro hammer buried module, Impact hammer buried module, Suction buried module, and Jetting module.

[0023] One embedding module may be a Vibro Hammer embedding module, which, in use, may be configured to generate vibrations to embed the plate anchor into the seabed.

[0024] One embedment module may be an impact hammer embedment module, which, in use, may be configured to generate an embedding force to embed the plate anchor into the seabed.

[0025] One of the embedding modules may be a suction embedding module, which, when in use, may be configured to generate a suction force to embed the plate anchor in the seabed.

[0026] One burial module may be a jetting module, which, in use, may be configured to generate a (fluid) jet to bury the plate anchor in the seabed.

[0027] The method may involve the use of a clamping module in conjunction with a modular follower apparatus, wherein the clamping module may be removably mounted within the modular follower apparatus, wherein a plate anchor may be clamped between (two) opposing jaws of the clamping module, and the jaws are preferably released from the plate anchor after the plate anchor has been placed at a desired location / depth within the seabed.

[0028] The modular follower device may include a slot for retaining a plate anchor within the device. The slot may be located at a first end (lower end) of the modular follower device. The slot may include an open-ended slot and may include two guide or docking slots offset by 180 degrees around the lower end of the housing or (tubular) body of the modular follower device. The slot may include two or more guide or docking slots offset around the lower end of the housing or (tubular) body of the modular follower device.

[0029] The method can include a power module and a connector for receiving power from the umbilical and transmitting power to the at least one embedded module. The power module can include a self-contained power source for providing power to the at least one embedded module. The power module can provide hydraulic and / or electrical power.

[0030] The method can include using a power pack module for the modular follower apparatus. The method can include removably attaching a power pack module to the modular follower apparatus. The power pack module can provide hydraulic or electrical power to one or more embedded modules, such as an impact hammer module and / or a clamping module and / or a vibro module and / or a clamping module and / or a jetting module.

[0031] The or each embedment module may be a combined embedment and extraction module.

[0032] The method preferably comprises adjusting / changing the length of a (tubular) housing of the modular follower device, which (tubular) housing preferably constitutes a suction follower housing.

[0033] The method may use multiple (tubular) housing sections that can be removably assembled into or removed from the (tubular) housing of the modular follower device. The method may allow for adjusting / changing the longitudinal / axial length of the (tubular) housing after withdrawal of the modular follower device from a first deployment and before a subsequent or subsequent deployment. The method may provide multiple sections resulting in various sections with different longitudinal / axial lengths.

[0034] The method preferably involves tethering a floating offshore wind turbine or other offshore device to the seabed, and preferably includes connecting a plurality of mooring lines extending from the floating offshore wind turbine or other offshore device to a number of buried plate anchors.

[0035] A second aspect of the present invention is 1. A plate anchor installation device comprising a modular follower device having a housing and extending from a first longitudinal end to a second longitudinal end, The follower device Plate anchor engagement module, Lifting line fixing mechanism, a first attachment mechanism for releasably attaching the first buried module; a second attachment mechanism for releasably attaching a second embedded module; and a power supply module for supplying power to at least one buried module; and the follower device is reconfigurable on board the vessel between subsea deployment locations so that buried modules can be replaced with buried modules for subsequent deployment and so that buried modules mounted on the follower device can be removed from or installed on the follower device; This is a plate anchor embedding device characterized by the above.

[0036] The first attachment mechanism can include a first attachment means. The first attachment mechanism can include an internal flange fastening mechanism. The second attachment mechanism can include a second attachment means. The second attachment mechanism can include an internal flange fastening mechanism.

[0037] The lift line securing mechanism can include a lift line securing module, which can be attached to the housing and / or can be attached to another module.

[0038] The first embedding module can generate an embedding force used to efficiently embed the plate anchor in a first layer / formation, and the second embedding module can generate an embedding force used to efficiently embed the plate anchor in a second layer / formation.

[0039] The burial modules of the modular follower device can be used in conjunction to drive the plate anchor into multiple (successive) layers / strata of the seabed. For example, the seabed may consist of multiple layers / strata of soil, each of which may be composed of different soil types and have different properties. Depending on these soil types and / or properties, different burial modules / means / burial forces may need to be used.

[0040] Preferably, the first embedded module and the second embedded module comprise one of the following modules: Vibro hammer buried module, Impact hammer buried module, Suction buried module, and Jetting module.

[0041] One embedding module may be a vibro hammer embedding module, which may be configured to generate vibrations in use to embed the plate anchor into the seabed.

[0042] One embedding module may be an impact hammer embedding module, which may be configured to generate an embedding force in use to embed the plate anchor into the seabed.

[0043] One of the embedding modules may be a suction embedding module, which may be configured to generate a suction force when in use to embed the plate anchor into the seabed.

[0044] One burial module may be a jetting module, which may be configured to generate a (fluid) jet (jet stream) when in use to bury the plate anchor in the seabed.

[0045] The plate anchor embedding device may comprise a clamping module, which may be removably mounted within the modular follower device. The clamping module may comprise a clamping mechanism having (two) opposing jaws of the clamping module that clamp the plate anchor therebetween, the jaws preferably being released from the plate anchor once the plate anchor is located at a desired location / depth within the seabed.

[0046] The modular follower device may include a slot capable of holding a plate anchor. The slot may be located at a first (lower) end of the modular follower device. The slot may be an open-ended slot. The slot may include two guide or docking slots offset by 180 degrees around the lower end of the housing or (tubular) body of the modular follower device. The slot may include two guide or docking slots offset by 180 degrees around the lower end of the housing or (tubular) body of the modular follower device.

[0047] The power module can include a connector for receiving power from the umbilical and transmitting the power to the at least one submerged module. The power module can include an independent power source for providing power to the at least one submerged module. The power module can provide hydraulic and / or electrical power.

[0048] The power module may include a power pack module for the modular follower device. The power pack may be removably attached to the modular follower device. The power pack module may provide hydraulic and / or electrical power to at least one embedded module and may provide hydraulic and / or electrical power to the impact hammer module and / or the clamp module.

[0049] The or each buried module may be configured as a buried and extractable module.

[0050] The modular follower device may comprise a (tubular) housing with an adjustable / variable (longitudinal / axial) length. The (tubular) housing may comprise a suction follower housing.

[0051] The plate anchor embedding device may comprise multiple (tubular) housings that may be removably assembled into or detached from the (tubular) housing of the modular follower device. The plate anchor embedding device may comprise multiple sections resulting in various sections of different longitudinal / axial lengths.

[0052] Preferably, the plate anchor embedding device is configured, in use, to embed a plurality of plate anchors into the seabed and moor the floating offshore wind turbine or other offshore apparatus, with a plurality of mooring lines extending from the floating offshore wind turbine or other offshore apparatus to the embedded plate anchors. [Brief explanation of the drawings]

[0053] The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a side view showing the installation vessel with itself at a target anchor location on the seabed. [Figure 2] FIG. 2 is a side view showing a plate anchor connected to a mooring line, stowed in a follower device on the deck of an installation vessel. [Figure 3] FIG. 3 is a side view showing the plate anchor tensioned on the mooring line and clamped to a follower device on the deck of the installation vessel. [Figure 4] FIG. 4 is a side view showing the plate anchor, mooring line and follower device complex being lowered through the water column by the installation vessel towards the target anchor location. [Figure 5] FIG. 5 is a side view of the plate anchor as it is being embedded through layered and different soil types by one or more of the embedded modules. [Figure 6] FIG. 6 is a side view showing the mooring line and plate anchor being released from the follower device. [Figure 7]FIG. 7 is a side view showing the follower unit being withdrawn from the seabed using one or more of the embedding / withdrawal modules. [Figure 8] FIG. 8 is a side view showing a preferred embodiment of a follower device attached to a lifting line. DETAILED DESCRIPTION OF THE INVENTION

[0054] The present invention relates to a method and apparatus for quickly and efficiently installing plate anchors 7 in all types of soil, and in particular to a method that is adaptable to address the problems and demands found in the FOWT industry.

[0055] To efficiently install foundation piles where different soil types exist as layered layers, it may be advantageous to use one or more burial means. In such cases, it is necessary to retrieve one type of driving equipment and switch to a different type. This switching operation requires a long time, and the time required to lower and retrieve the equipment is even longer, especially at greater depths and in harsh environments. The present invention provides a method and apparatus that allows for the construction of multiple burial means / modules that can handle layered soil situations without the need to retrieve and reconfigure the driving equipment. This feature eliminates the time-consuming equipment retrieval and redeployment process, resulting in shorter installation times. This time savings translates into reduced installation vessel costs and reduced carbon emissions. The apparatus is also suitable for burial in single-layer soils, if desired.

[0056] The present invention provides a method and apparatus for efficient installation of plate anchors 7 intended for offshore wind farms consisting of floating offshore power turbines (FOWTs). The invention is also applicable to installing plate anchors 7 for other purposes in the renewable energy industry (current turbines, tidal turbines, etc.), the oil and gas industry (floating driving units, floating production units, terminals, etc.) and any other case requiring an efficient anchor.

[0057] The present invention provides a method for burying all or part of a plate anchor 7 and associated mooring line 8 using a follower device 9. The components are assembled, raised, lowered, handled and retrieved by an installation vessel 3.

[0058] The follower device 9 is made up of multiple device sections (modules 101, 102, 103, 104, 105, 106, 108) that perform required functions determined by the type(s) of soil present, the means for operating the mooring line 8 (or mooring line sections), and the means for providing power and fluid to the follower device 10. Different installations will require different functions, and therefore the follower device 9 can be made up of any combination of multiple modules.

[0059] The above module can be composed of the following modules: i. Clamp module 101. This is used to hold the plate anchor 7 in the follower device 9, for example, when a rigid connection between the plate anchor 7 and the follower device 9 is required. In a preferred configuration, no rigid clamp is required when impact hammering. Therefore, another function of the clamp module is to safely distribute the stress of the impact hammer to the plate anchor (i.e., to spread the load). Therefore, the clamp module is provided with structural features to do this. ii. Mooring line holding module 104. This is a module that holds the mooring line 8 taut and optionally holds the plate anchor 7 with the mooring line 8 within the follower device 9 (for example, for use when the clamping module 101 is not required). iii. An internal impact hammer module 102 having an internal impact hammer 20, for example when used for impact hammering. iv. Length Adjustment Module 103. This is a variable length component that changes the overall length of the follower device 9, controlling the final depth of the plate anchor 7, as well as providing conduits for pressurized water, hydraulics and / or power and signals (if required). v. Suction seal module. This is the upper closure / suction pump interface module, for example, in suction burial. vi. Jetting Module: This is a module that interfaces to a water pump or subsea water pump, for example, during jetting burial. vii. A vibrohammer / impact hammer interface module 105, for example when using a commercially available vibrohammer or impact hammer. viii. A lifting module 107, which is an upper end mounting device for connecting the lowering rigging. In some cases, this module will be part of a commercially available vibro hammer; and / or ix. Subsea Hydraulic Power Pack Module 108. This is a module for use, for example, when the water depth is such that hydraulic power supplied from the surface is inefficient. In some embodiments, the power supply module may only provide power to the corresponding submerged module(s), and may or may not include an independent (built-in) power supply or (hydraulic / electrical) source. For example, the power module may comprise a connector that receives power from an umbilical and transmits it to at least one submerged module. The power module may comprise an independent power source that provides power to at least one submerged module. The power module may be configured to provide hydraulic and / or electrical power.

[0060] The soil type can be determined during a site-specific ground investigation early in the development lifecycle. Information from the ground investigation will determine the type of burial module / means needed, along with power requirements. The combination of modules within the follower device 9 can be arranged so that there are enough modules for complete burial and retrieval of the plate anchor 7 throughout all possible soil strata. Thus, the plate anchor can be fully buried and secured in the seabed having several different soil layers 12, 14, 16 (layers / strata) of different soil types without retrieving or modifying the burial mechanism.

[0061] Different burial modules / methods are used to efficiently bury plate anchors in different soil types (i.e., soils made of different materials on the seabed). With a few exceptions, theoretically, all burial module types (vibro, impact, suction, and jetting) can be buried according to a general definition of soil type (mud, silt, and sand). However, efficiency (i.e., speed) varies widely and may even be so poor that it is considered impossible in some cases. The soil types for which each burial module is thought to work optimally can be classified as follows: (1) vibro for sand, (2) impact for sand and clay, (3) suction for soft clay, and (4) jetting for all soils.

[0062] Once the plate anchor 7 has been buried in the seabed 2 to the desired depth, the plate anchor 7 and mooring line 8 are released, the follower device 9 is retrieved and another plate anchor 7 is reloaded. Soil resistance during retrieval is again counteracted using one or more of the following means: vibration using a vibro hammer, back suction (overpressure) by a suction seal module and / or direct extraction from the installation vessel.

[0063] The specific embodiment of the present invention shown in the accompanying drawings is based on an installation method using an Anchor Handling Construction Vessel (AHCV) 3 equipped with a stern roller and crane 17. This method is also applicable to other carrier vessels, including crane ships, subsea construction vessels and heavy lift vessels.

[0064] As shown in the accompanying drawings, one end of the mooring line 8 is connected to the plate anchor 7, the other end is held by the installation vessel 3 and then connected to the FOWT. Note that this method can also be applied to a short section of the mooring line 8 with a subsea mooring connector, in which case the connection to the remaining section of the mooring line 8 will be made in a later phase of the operation.

[0065] The plate anchor 7 is inserted into the follower device 9 using the installation vessel's crane 17. Other lifting, jacking and handling means for hoisting, jacking and handling the plate anchor 7 may also be used.

[0066] The chain retention mechanism can be hydraulically, electrically or manually operated.

[0067] The present invention also allows for batch-based burial of multiple plate anchors. For example, multiple plate anchors can be initially buried in the seabed adjacent to a target location. A first configuration of follower devices (possibly with a first anchor secured thereto) is deployed, and the first batch of anchors is buried. In this system, each anchor can utilize a configuration of burial modules mounted on the follower devices. The follower devices can then be retrieved for reconfiguration. The follower devices can then be redeployed to bury a second batch of plate anchors, again utilizing this different configuration of follower devices. While this system can save some time by not retrieving the follower devices between the burial of each plate anchor, this method requires that the plate anchors be individually installed on the seabed and secured within the follower devices while in and on the seabed.

[0068] In the method, the follower device can be deployed during a first deployment and one or more plate anchors can be buried with the follower device in a first configuration. The follower device can then be retrieved to the installation vessel. Once on deck of the installation vessel, the follower device can be reconfigured to include a different burial module. The follower device can then be deployed and one or more additional plate anchors can be buried.

[0069] The method allows the follower device to be deployed and retrieved any number of times (two or more times) and / or in a first series (first batch) while maintaining the configuration of the follower device. The method further allows the follower device to be reconfigured to provide a different embedding module / means on the follower device, and the follower device to be deployed and retrieved with at least one additional plate anchor. Furthermore, the method allows the follower device to be deployed and retrieved any number of times (two or more times) and / or in a second series (second batch) while maintaining another configuration of the follower device, preferably different from the original configuration of the follower device used in the first series.

[0070] This batch burial method involves placing multiple plate anchors on the seabed. While the plate anchors and follower devices are on the seabed, the plate anchors are only fixed within the follower devices (although the first plate may be fixed within the follower devices on board the installation vessel).

[0071] In some methods, the follower device can be retrieved and deployed for the next plate anchor while maintaining the buried modular configuration. For example, even if the follower device is retrieved to an installation vessel, it may need to be reconfigured from time to time. In this regard, it is a feature of the follower device that it can be reconfigured to provide a multi-functional follower device.

[0072] As shown in Figure 1, an installation vessel 3 traverses the ocean surface 1 and is positioned at or near a target anchor location 4 on the seabed 2. The installation vessel shown is an AHCV 3, although other installation vessels with useful crane 17 and / or winch capabilities could also be used.

[0073] The anchor embedding devices are prepared and stowed on deck 5 of the installation vessel 3. The follower devices 9 releasably hold the plate anchors and then embed them in the seabed 2 before retrieving the follower devices 9 ready to embed the next plate anchor 7. Accordingly, the follower devices 9 are provided with a retention mechanism for holding each plate anchor 7 to the follower devices 9, which in a preferred embodiment may use a clamping mechanism as described below.

[0074] The follower device 9 includes a housing 30, which is a substantially tubular housing extending from a first (lower) longitudinal end 32 to a second (upper) longitudinal end 34. The tubular housing need not be cylindrical, and the tubular housing may have other functional shapes, but in a preferred embodiment, the tubular housing is cylindrical. The housing 30 may form a suction follower housing. The follower device 9 includes fastening means at or toward its upper end for fastening the follower device 9 to the lift line 6. The fastening means may include one or more brackets 40 with openings for fastening to couplings at the ends of the lift line 6. In some embodiments, the fastening means may be located on one of the other modules. The fastening means may also include brackets, pad eyes, or similar fastening devices.

[0075] A retention mechanism for retaining the plate anchor 7 is located at the lower end 32 of the follower device. In a preferred embodiment, the retention mechanism comprises a clamp that holds the plate anchor 7 within a slot 50 located at the lower end of the follower device. Specifically, the slot 50 comprises two or more docking or guide slots extending from the lowermost end 32 of the housing 30, where each slot is offset around the circumference of the tubular housing 30; in one embodiment, the two guide slots are offset 180 degrees. The plate anchor 7 extends diametrically across the tubular housing 30 in the retained position. These slots 50 confine the plate anchor 7 within the lower end 32 of the housing 30, allowing a releasable tightening mechanism 101 to further tighten the plate anchor 7 in place. In some embodiments, the slot 50 may comprise two or more guide slots that may be located at the lower end of the housing.

[0076] The plate anchor 7 comprises a plate 60 and a shank with means for securing the plate anchor 7 to a mooring line 8 in use. The securing means comprises a shank (bracket) 62 located on a first upper surface of the plate 60 of the plate anchor 7. The shank 62 has a securing opening that engages with a corresponding coupler on the mooring line 8. The mooring line 8 is often a chain, although other materials such as wire or synthetic rope can also be used for the mooring line 8.

[0077] As shown in FIG. 2 , the plate anchor 7 can be secured to a mooring line 8 located on deck 5. Additionally, a lifting line 6 is attached to the fixed shank 62 of the plate anchor 7 for handling purposes, allowing the plate anchor 7 to be raised and lowered onto the installation vessel 3. In particular, a crane 17 is used to lift the plate anchor 7, then move it and load it into the follower device 9 using the lifting line 6. Typically, this is done on deck 5 of the installation vessel, although the first anchor 7 of a multi-anchor operation can be pre-loaded near the dock. In the preferred embodiment disclosed herein, the lifting line 6 starts from the installation vessel's crane 17. The plate anchor 7 can also be lifted and handled by other means, such as by jacking, winching, or a robotic arm.

[0078] In some configurations and embodiments, the plate anchor 7 can be secured and retained within the follower device 9 via a tensioned portion of the mooring line 8. In such configurations, tension is applied to the mooring line 8, or at least a portion thereof, to compress the plate anchor 7 into the slot(s) 50, thereby sufficiently retaining the plate anchor 7 within the slot(s) 50. However, in some situations, a clamping mechanism 101 may be required to more securely retain the plate anchor 7 and prevent or inhibit movement of the plate anchor 7 about its planar orientation within the follower device 9. For example, some burial modules / means may advantageously provide a single-plane fixation of the plate anchor 7 without significant movement of the plate anchor 7 relative to the housing 30. Alternatively, some burial modules / means may benefit from a non-rigid retention mechanism. This can be achieved through the use of slot(s). For example, in the case of impact hammering, the objective is to distribute the force rather than concentrating it on the clamping mechanism. In this situation, the clamp is released and the plate anchor is retained by the slot(s). The distribution surface, which is formed by a follower device, can transfer these forces evenly to the plate anchor, thereby reducing the stresses present in the plate anchor in particular.

[0079] As shown in FIG. 3 , tension is applied to the mooring line 8, and the plate anchor 7 is clamped to the follower device 9 while the follower device 9 is positioned on the installation vessel's deck 5. The plate anchor 7 is positioned within the slot(s) 50 defined by the housing 30 of the follower device 9. The shank 62 of the plate anchor 7 is positioned at the entrance of the slot(s) 50, with a portion of the plate anchor 7 extending downward and away from the lower end 32 of the housing 30. This becomes the lower end of the plate anchor 7, which is then directly driven to penetrate the seabed 2. Once this position is reached, the clamping mechanism 101 can be activated. The clamping mechanism 101 includes at least one jaw, and preferably multiple jaws. In a preferred embodiment, a first clamping member (jaw) 70 and a second clamping member (jaw) 72 are used to clamp the plate anchor 7 between them. As shown in FIG. 3 , the two jaw members 70, 72 are driven to press inward toward each other and against opposing surfaces of the plate anchor 7. This clamps the plate anchor 7 between the two jaw members 70, 72, with the lower portion of the plate anchor 7 extending directly away from the housing 30. In some cases, it may be advantageous to provide multiple sets of jaws (i.e., clamps) to efficiently transmit vibrations.

[0080] The mooring line retention mechanism 10 is used to apply tension to the mooring line 8. In a preferred embodiment, as shown, the retention system is a hook 80 that engages the mooring line 8 and is capable of sliding longitudinally along the axis of the follower device 9 to remove slack from the mooring line 8. For example, a link of the chain of the mooring line 8 engages the hook 80 with the hook 80 in a first, initial position. In this configuration, the chain of the mooring line 8 is relatively slack, forming a slack section of chain as shown in FIG. 3 . The hook 80 is configured to translate along the longitudinal axis of the housing 30. Specifically, the hook 80 is configured to move from the initial position to a second, tensioned position where the hook 80 moves away from the first lower end 32 of the housing 30 and toward the second upper end 34. Specifically, this movement moves the mooring line 8 away from the shank 62 of the retention plate anchor 7 to which the mooring line 8 is coupled. The translation of the hook 80 from the initial position to the tensioned position is a sliding action of the hook 80 which may be hydraulically or electrically actuated, or manually ratcheted. Other means for applying tension to the mooring line 8 may include wire slings, turnbuckles, come-alongs, or manual winches.

[0081] As mentioned above, in this preferred embodiment, the plate anchor 7 is held in the follower device 9 using the tightening mechanism 101. In particular, the use of this tightening mechanism 101 allows vibrations to be transferred from the vibro hammer 106 to the anchor 7 via the follower device 9, which has the advantageous effect of reducing friction with the soil during burial. For example, if a vibro hammer is not used, the plate anchor 7 can be held in the follower device 9 using only the mooring line retention mechanism 10.

[0082] Additionally, the tightening mechanism 101 can transmit impact / vibration from the impact hammer module 102 through the follower device 9 to the anchor 7, which advantageously reduces friction with the soil during burial. For this burial operation, the plate anchor 7 can be held within the follower device 9 without the use of a rigid tightening mechanism. This allows for significant force deployment and / or distribution when using impact hammering.

[0083] As shown in Figure 4, the plate anchor 7, mooring line 8, and follower device 9 are lowered using the lifting line 6. As mentioned above, the lifting line 6 is attached to a fixed bracket 40 located at or towards the upper end 34 of the housing 30. The tensioned portion of the mooring line 8 is adjacent to the housing 30 and engages a hook 80. The remaining length of the mooring line 8 extends generally upward from the hook 80 to the installation vessel 3.

[0084] Conventionally, there are numerous methods for lifting and inverting piles and subsea structures from an installation vessel, and these methods are believed to apply to the follower device 9 with the plate anchor 7. Simultaneous lowering of the mooring lines 8 and other components can be accomplished using various combinations of cranes and winches, depending on the capabilities of the installation vessel 3. The umbilical 110 provides a source of electrical, hydraulic, or signal power from the surface to the follower device 9. The specific requirements for the umbilical depend on the modules used in the follower device. A lifting line 6 attached to the upper end 34 lowers the lower portion of the plate anchor 7 to the target location 4 and allows it to be directly penetrated into the seabed 2. Because pure gravity alone is insufficient to penetrate the plate anchor 7 to a sufficient depth into the seabed 2, the follower device 9 comprises an embedding module / means that is activated to penetrate the plate anchor 7 to the required depth into the seabed 2. As noted above, the follower device 9 has the capability to accommodate a number of different embedding modules. This capability allows a single follower device 9 to drive the plate anchor 7 into the seabed 2 through different numbers and combinations of soil layers (stratum / formations) 12, 14, 16 within the seabed. As mentioned above, different embedding modules / means can be optimized for different soil types with different properties. Therefore, application of the present invention eliminates the need to retrieve the follower device 9 according to the different soil layers (stratum / formations) 12, 14, 16 within the seabed 2, and allows the plate anchor 7 to be installed with a single deployment of the follower device 9.

[0085] As shown in FIG. 5 , the plate anchor 7 and the lower end of the mooring line 8 are buried in the seabed 2 using a follower device 9. In this example, there are three soil layers 12, 14, and 16, and the present invention provides a simple, fast, and reliable method for driving each of the layers 12, 14, and 16 into different soil types. The follower device 9 includes the necessary embedding equipment to efficiently drive the plate anchor 7 into (or through) each of the soil layers 12, 14, and 16. The follower device 9 of the present invention can use any combination of vibro-driving, impact hammering, suction embedding, or jetting. Because all required modules are present or can be present, the system allows for easy switching between driving methods without the need to retrieve and reconfigure the equipment.

[0086] Once the plate anchor 7 has reached the desired driving depth, the mooring chain 8 and plate anchor 7 are released. The clamping mechanism 101 is released by pulling the jaw members 70, 72 outward and away from each face of the plate anchor 7. In this position, the plate anchor 7 is no longer captured within the housing 30 and can be removed from within the slot(s) 50 in the housing 30.

[0087] The hook 80 moves from the tensioned position to the released position by reversing the sliding action of the hook. The hook 80 translates relative to the housing 30 and moves in a direction toward the lower end 32. This movement slackens the tensioned portion of the mooring line 8 and causes the chain links of the mooring line 8 to disengage from the hook 80. In this configuration, the plate anchor 7 is located within the slot(s) 50 in the housing 30 but is not engaged within the separable follower device 9.

[0088] As shown in Figure 7, after extraction of the follower device 9, the plate anchor 7 and mooring line 8 remain. Extraction of the follower device 9 from the seabed 2 is performed using one or more extraction means, which may consist of one or more burial modules (or multiple modules, such as a combined burial and extraction module). The extraction modules / means may consist of one or more of vibro-extraction, back-suction, and / or pulling force from the installation vessel. Since these functions are already present in the follower device 9 and lifting line 6, no equipment modifications are required. The follower device 9 is retrieved onto the deck 5 of the installation vessel 3, where another plate anchor 7 is ready for use. During this process, the burial and / or retrieval modules can be quickly and easily changed if the next target location consists of a different combination of soil layers (stratum / strata).

[0089] A preferred embodiment of the follower device 9 is shown in Figure 8. This shows a clamping module 101, a mooring line retention module 104, an internal impact hammer module 102, a length adjustment module 103, a vibro hammer / impact hammer interface module 105, a lifting module 106 and a subsea hydraulic or electric power pack module 108.

[0090] The mooring line retention module 104 has attachment means for generating tension in a portion of the mooring line 8 and maintaining that portion of the mooring line under tension. Specifically, as previously described, the mooring line retention module 104 includes a movable (axially sliding) hook 80 that moves toward and away from the lower end 32 of the follower device 9. The hook 80 is configured to connect to a link of the mooring line 8, with the lower portion of the mooring line 8 connected to a plate anchor 7 engageable within the slot(s) 50 at the lower end 32 of the follower device 9. Once a particular link is engaged with the hook 80, the upward movement of the hook 80 increases the axial distance between the engaged plate anchor 7 and the hook 80. This increases tension in the portion of the mooring line 8 extending between the plate anchor 7 and the hook 80 located at or toward the top of the follower device 9. Once the anchor plate 7 has been driven into the seabed 2 to the required position / depth, the link of the mooring line 8 is disengaged from the hook 80 by moving the hook 80 axially downwards. The mooring line 8 can then be extended from the plate anchor 7 directly towards the moored structure.

[0091] The clamping module 101 includes two or more jaws or sets of jaws (sets of jaws); in the illustrated embodiment, the clamping module includes first and second jaw members 70, 72, which are located at the lower end 32 of the follower device 9 and clamp the plate anchor 7 during deployment and during the burial phase. The clamp maintains the plate anchor 7 in a fixed position and orientation, which may be advantageous, particularly during some burial methods. The lower end 32 of the housing 30 of the follower device 9 includes guide slots, which may consist of two or more slots; the illustrated embodiment includes first and second guide slots 50. These two slots 50 maintain the plate anchor 7 in a desired orientation relative to the tubular housing 30 of the follower device 9. The slots 50 also maintain the plate anchor 7 in an orientation and position relative to the clamp.

[0092] The follower device includes a mounting device or mechanism for mounting the internal impact hammer module 102. The mounting mechanism may consist of an internal bolted flange. In a preferred embodiment, the mounting mechanism is located adjacent to and / or above the clamp module 101. The impact hammer module 102 includes a hammer 90 (piston or ram) that sits on an anvil / block 92 and generates an embedding force for some soil types. Because the forces generated are significant, in a preferred embodiment, the internal impact hammer module 102 is located directly above and adjacent to the clamp module 101.

[0093] The follower device 9 is adjustable in length. This adjustability optimizes the follower device 9 for embedding the plate anchor to an adjustable maximum depth. For example, increasing the longitudinal / axial length of the follower device 9 for deeper seabed depths allows for deeper driving. The follower device 9 includes a length adjustment module 103. This length adjustment module 103 may comprise a section 36 of the tubular housing 30 whose length can be selected to provide a follower device 9 with a desired length. In a preferred embodiment, this section of the housing 30 is located directly above the internal impact hammer module 102 or directly below the mooring line retention module 104. A user can use multiple housing sections 36 of different lengths and secure each housing section within the follower device 9. In some embodiments, more than one housing section 36 can be secured within the follower device 9. For example, two or more sections 36 can be secured in an end-to-end configuration to increase the length of the follower device 9. As noted above, these sections 36 are detachable from the deck 5 of the installation vessel 3 and can be selected for each deployment. Thus, the length adjustment module 103 makes it possible to realize suction followers of different lengths and different capacities that can be individualized according to the task and the target site.

[0094] The follower device 9 includes a mooring line retention module / means 104 that maintains the lower portion of the mooring line 8 adjacent to the housing of the follower device 9 during the deployment and burial phases. This reduces the risk of the mooring line 8 becoming tangled and pulling the plate anchor 7 away from the desired burial direction, and facilitates maintaining the mooring line 8 adjacent to the housing 30 during driving into the seabed 2. In a preferred embodiment, the mooring line retention module / means 104 includes a hook located in an upper position on the follower device 9 / housing 30. As previously described, the hook 80 is slidable from a lower position to an upper position. In use, a link of the chain of the mooring line 8 engages the hook 80 in the lower position. The hook 80 then moves away from the plate anchor 7, increasing the separation distance between the ends of the chain segment, thereby increasing tension on the chain segment. This tension prevents the chain segment from disengaging and being pinned against the housing 30 of the follower device 9. After the plate anchor 7 is buried to the required depth in the seabed 2, the mooring line holding module / means 104 is restarted and releases the mooring line 8. Specifically, the hook 80 returns to the lower position, releasing tension on the section of chain. This movement disengages the link from the hook 80. Once disengaged, the mooring line 8 extends from its lower position, where it is secured to the plate anchor 7, to the upper end of the mooring line 8, which then connects the structure to the plate anchor 7.

[0095] The vibro hammer / impact hammer interface module 105 is located above the mooring line retention module / means 104 and below the vibro hammer 106 .

[0096] The vibro hammer 106 is located on an interface through which the vibratory motion for the vibro hammer 106 is transmitted to the housing of the follower device 9 .

[0097] The follower apparatus 9 includes a subsea power pack 108. This power pack is located at the top end 34 of the follower apparatus 9. Specifically, it is located above the vibro hammer module 106. It should be noted that the bracket(s) 40 of the lifting module 107 may extend beyond the top surface of the power pack 108, providing an easily accessible mounting opening. The power pack 108 is configured to provide a hydraulic or electrical source for the follower apparatus 9. For example, the power pack 108 may provide a hydraulic or electrical source to the impact hammer module 102. This can be advantageous in deep water where the supply of such a hydraulic source from the surface may be insufficient.

[0098] The follower device 9 includes a lifting module 107 located toward its upper end. This lifting module 107 provides a mounting means for attaching the lower end of the lifting line 6. This mounting means may include at least one bracket 40 that provides a fixed opening. In this case, the follower device 9 can be manually mounted and removed while on the deck 5 of the installation vessel 3. Once mounted, the follower device 9 can be suspended from the lifting line 6 and moved to the desired location for the plate anchor 7. In some embodiments, the lifting module can be provided on one of the other modules.

[0099] Each module may be removably secured within the follower device using internal bolted flanges and / or similar devices.

[0100] The umbilical 110 connects to the follower unit 9 and may connect to a subsea power pack 108. The umbilical 110 may provide electrical power (and / or hydraulic power) from the surface to the follower unit 9. The configuration of the umbilical 110 will depend on the modules within the particular follower unit 9.

[0101] The suction module and / or jetting module can often be used in place of the impact hammer module and tubular housing portions 30 and 36. In such a configuration, the clamping module and possibly the vibro / impact adapter module 105 are still considered required modules. The suction module includes a vent valve and an interface for an attached suction pump or an ROV-mounted suction pump. It includes a jetting pump and has piping that interfaces with the clamping module and plate anchor, and the actual jet nozzles can also be incorporated into the plate anchor. [Explanation of symbols]

[0102] 1 sea level 2 Undersea 3 Installation vessels, anchor handling construction vessels (AHCV) 4 Anchor position 5 Deck 6 Lifting Line 7 Plate anchor 8 Mooring lines 9 Follower Device 10 Retention mechanism 12, 14, 16 Soil layers (layers / strata) 17 Crane 20 Impact Hammer 30 Housing 32 (lower part) longitudinal end, lower end 34 (Upper) Longitudinal end, upper end 36 Housing part 40 Bracket 50 slots 60 plates 62 Shank (bracket) 70 First clamping member (jaw) 72 Second clamping member (jaw) 80 Hook 90 Hammer 101 Clamp module, tightening mechanism 102 Impact Hammer Module 103 Length Adjustment Module 104 Mooring Line Retention Module 105 Vibro Hammer / Impact Hammer Interface Module 106, 107 Lifting Module 108 Subsea Hydraulic or Electric Power Pack Module 110 Umbilical

Claims

1. A method for embedding a plate anchor, comprising: When burying plate anchors in different types of soil, multiple burial modules suitable for each type of burial are prepared, determining the type of seabed soil at the target location; Selecting a buried module based on the soil type at the target location; releasably mounting the embedded module within a modular follower device; deploying the modular follower device from a vessel; activating the embedding module to drive the plate anchor into the seabed; Retrieving the modular follower apparatus to the vessel and subsequently reconfiguring the modular follower apparatus by adding another embedded module to the modular follower apparatus for subsequent deployment. A method for embedding a plate anchor.

2. 10. The method of embedding a plate anchor of claim 1, further comprising: retaining a first plate anchor within the modular follower device; burying the first plate anchor at a first destination; retrieving the modular follower device; reconfiguring the embedded module within the modular follower device; and retaining another plate anchor within the modular follower device and burying the yet another plate anchor at a different destination.

3. 3. The method of embedding a plate anchor according to claim 2, wherein a plurality of plate anchors are embedded to form mooring points for floating offshore wind turbines or other offshore equipment.

4. 2. The method for embedding a plate anchor according to claim 1, further comprising identifying a layer and / or formation within the seabed and attaching one or more embedding modules to the follower device for insertion into the identified layer and / or formation within the seabed.

5. 2. The method of embedding a plate anchor according to claim 1, wherein a combination of embedding modules is attached to the modular follower device and penetrates multiple layers / stratum of the seabed.

6. Vibro hammer buried module, Impact hammer buried module, Suction buried module, and Jetting module, 2. The method for embedding a plate anchor according to claim 1, wherein one or more embedding modules are selected and attached from the following:

7. 2. The method of claim 1 including providing a clamping module for the modular follower device, releasably mounting the clamping module within the modular follower device, clamping the plate anchor between opposing jaws of the clamping module and then releasing the jaws from the plate anchor once the plate anchor is located at a desired location / depth within the seabed.

8. 2. The method of installing a plate anchor according to claim 1, further comprising providing a power pack module for the modular follower device, and removably attaching the power pack module to the modular follower device, wherein the power pack module provides a hydraulic or electrical source to at least one of the installation modules.

9. 2. The method for embedding a plate anchor according to claim 1, further comprising adjusting the length of the housing of the modular follower device.

10. 10. The method of embedding a plate anchor according to claim 9, further comprising providing multiple housing sections that can be releasably assembled to or removed from the tubular housing of the modular follower device.

11. 11. The method of embedding a plate anchor according to claim 10, wherein the longitudinal length of the tubular housing is adjusted after retrieving a first deployment of the modular follower device and before a next deployment, and wherein multiple sections are provided, resulting in various sections having different longitudinal lengths.

12. 10. The method of embedding a plate anchor according to claim 1, wherein a floating offshore wind turbine or other offshore equipment is tethered to the seabed and a plurality of mooring lines extending from the floating offshore wind turbine or other offshore equipment are connected to a number of embedded plate anchors.

13. 1. A plate anchor installation device comprising a modular follower device having a housing and extending from a first longitudinal end to a second longitudinal end, The follower device Plate anchor engagement module, Lifting line fixing mechanism, a first attachment mechanism for releasably attaching the first embedded module; a second attachment mechanism for releasably attaching a second embedded module; and a power supply module for supplying power to at least one buried module; and the follower device is reconfigurable on board the vessel between subsea deployment locations so that buried modules can be replaced with buried modules for subsequent deployment and so that buried modules mounted on the follower device can be removed from or installed on the follower device; A plate anchor embedding device characterized by:

14. 14. The plate anchor embedding device of claim 13, wherein the first embedding module generates an embedding force to efficiently embed the plate anchor in a first layer / formation, and the second embedding module generates an embedding force to efficiently embed the plate anchor in a second layer / formation.

15. 14. The plate anchor embedment device of claim 13, configured in conjunction with an embedment module of the modular follower device to drive the plate anchor into multiple successive layers / formations of the seabed.

16. the first embedded module and the second embedded module, Vibro hammer buried module, Impact hammer buried module, Suction buried module, and Jetting Module 14. The plate anchor embedding device of claim 13, comprising one of:

17. 14. The plate anchor installation device of claim 13, wherein a clamping module is removably mounted within the modular follower device, the clamping module comprising a clamping mechanism having opposing jaws for clamping a plate anchor.

18. 14. The plate anchor embedding device of claim 13, wherein the power supply module comprises a power pack module removably attached to the modular follower device, the power pack module being configured to provide hydraulic and / or electrical power.

19. 14. The plate anchor installation device of claim 13, wherein the modular follower device comprises a housing having an adjustable longitudinal length.

20. 20. The plate anchor embedding device of claim 19, comprising multiple housing sections removably installable in or detachable from the housing of the modular follower device, the housing sections being various sections of differing longitudinal length.

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