Anchor systems and methods

Abstract

A method of installing a subsea anchor, the method comprising the steps of: (a) constructing a drill string (13) from a vessel (10); (b) drilling a hole (12) in the seabed (4); (c) lowering an anchor member (14) from the vessel (10) into the hole (12); and (d) cementing the anchor member (14) in place in the hole (12) via a cementing hose (15) from the vessel (10).

Description

[Technical Field]

[0001] The present invention relates to anchoring systems and methods, and in particular to methods and systems for establishing subsea mooring foundations from a vessel. [Background technology]

[0002] background Mooring and anchoring systems are important for ensuring the secure positioning of floating objects, such as floating wind turbines or floaters used in oil production. Many solutions exist for this purpose, such as suction bucket moorings, buried anchors, and torpedo anchors. For example, with the increasing development of offshore renewable energy and the exploration of more remote and environmentally challenging areas for natural resource exploration, there is a continuous need for improved mooring and anchoring technology. Improved mooring and anchoring technology is also relevant for a variety of other marine applications.

[0003] References which may be useful in understanding the field include US Pat. No. 3,330,338A, GB Patent Application Publication No. 1,526,934A, US Pat. No. 3,827,258A and US Pat. No. 3,984,991A. Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure aims to provide improved techniques for mooring and anchoring, or at least alternative solutions to the state of the art. [Means for solving the problem]

[0005] overview In one embodiment, a method of installing a subsea anchor is provided, the method including the steps of: (a) constructing a drill string from a vessel; (b) drilling a hole in the seabed; (c) lowering an anchor member from the vessel into the hole; and (d) cementing the anchor member in place in the hole from the vessel via a cementing hose.

[0006] The following detailed description and appended claims outline additional embodiments.

[0007] BRIEF DESCRIPTION OF THE DRAWINGS These and other features will become apparent from the following description of exemplary embodiments given as non-limiting examples with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0008] [Figure 1] 1 illustrates an arrangement according to some embodiments. [Figure 2] 1 illustrates an arrangement according to some embodiments. [Figure 3] 1 illustrates steps of a method according to some embodiments. [Figure 4] 1 illustrates steps of a method according to some embodiments. [Figure 5] 1 illustrates steps of a method according to some embodiments. [Figure 6] 1 illustrates steps of a method according to some embodiments. [Figure 7] 1 illustrates steps of a method according to some embodiments. [Figure 8] Indicates an anchor. [Figure 9a] 1 shows an excavator and associated components. [Figure 9b] 1 shows an excavator and associated components. [Figure 10] 1 illustrates a watercraft used in some embodiments. [Figure 11] 1 illustrates a watercraft used in some embodiments. [Figure 12] 1 illustrates a watercraft used in some embodiments. [Figure 13] 1 illustrates a watercraft used in some embodiments. [Figure 14] 1 illustrates steps of a method for tilting or skidding a structure. [Figure 15] 1 illustrates steps of a method for tilting or skidding a structure. [Figure 16] 1 illustrates steps of a method for tilting or skidding a structure. [Figure 17] 1 illustrates steps in a method for generating liquid flow in a drill string. [Figure 18] 1 shows a vessel having a side cantilever structure. [Figure 19] 1 illustrates one embodiment of an anchor member. [Figure 20] 1 illustrates one embodiment of an anchor member. [Figure 21] 1 illustrates one embodiment of an anchor member. [Figure 22] 1 illustrates one embodiment of an anchor member. [Figure 23] 1 illustrates one embodiment of an anchor member. [Figure 24] 1 illustrates one embodiment of an anchor member. [Figure 25] 1 illustrates a watercraft used in some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0009] Detailed Description The following description may use terms such as "horizontal," "vertical," "side," "front-to-back," "up-down," "above," "below," "inside," "outside," "front," "back," etc. These terms generally refer to perspectives and orientations associated with normal use of the invention, as shown in the drawings. These terms are used for the convenience of the reader only and should not be considered limiting.

[0010] 1 and 2 show an example installation in which the embodiments described below can be utilized. A floating structure 1 is moored to the seabed 4 by a plurality of anchors 2 (only one anchor 2 is shown in FIG. 1 , but it should be understood that additional anchors are typically present). Mooring lines 7 connect the floating structure 1 to the anchors 2. The floating structure 1 may be, for example, a floating wind turbine, as shown. The floating structure 1 is moored at a location at a water depth x (the vertical distance between the waterline 3 and the seabed 4). As shown in FIG. 1 , the anchors 2 may be installed at a horizontal distance y from the floating structure 1, providing so-called catenary mooring. Alternatively, as shown in FIG. 2 , the mooring lines 7 may extend substantially vertically to provide a vertical mooring system. The mooring system may, for example, comprise three anchors 2 and three mooring lines 7.

[0011] The seabed 4 may include a soft soil layer 5 and a hard soil layer 6. The soft soil layer 5 may have a lower density or hardness compared to the hard soil layer 6. The soft soil layer 5 and the hard soil layer 6 may combine to form a rock layer, or the seabed 4 may include only rock layers, only soft soil layers 5, or only hard soil layers 6.

[0012] According to one embodiment, there is provided a method for installing a subsea anchor 2, the method comprising the steps of: (a) constructing a drill string 13 from a vessel 10; (b) drilling a hole 12 in the seabed 4; (c) lowering the anchor member 14 from the vessel 10 into the hole 12; (d) cementing the anchor member 14 in place in the hole 12 via a cementing hose 15 from the vessel 10; Includes.

[0013] Figures 3 to 7 show a method for installing a subsea anchor 2. A vessel 10 is provided and positioned above the location where the subsea anchor 2 is to be installed. A drill string 13 is constructed on the vessel 10, for example by a number of individual drill string segments connected together (e.g. so-called joints or stands), and lowered towards the seabed 4. The drill string 13 comprises a drilling head for engaging the seabed 4 and drilling a hole 12, as shown in Figure 3.

[0014] Once the hole 12 is completed, for example after drilling the hole 12 to a depth of several meters, the drill string 13 may be lifted out of the hole 12 and suspended from the vessel 10 rather than being fully retrieved onto the vessel 10. In such a case, the drill string 13 may remain suspended from the vessel 10 while steps (c) and (d) are performed. If a vessel 10 having a moonpool (see below) is used, the drill string 13 may be suspended via the moonpool 20. The vessel 10 may be provided with a skidding arrangement or equivalent mechanism that allows the drill string 13 to be moved laterally or sideways within the moonpool before steps (c) and (d) are performed. Moving or skidding the drill string 13 sideways may include moving or skidding the drill string 13 away from a vertical axis extending through the drilling rig 30 (described below). This may be done, for example, by a trolley or skid located within or adjacent to the moonpool. In this manner, the drill string 13 may be positioned vertically below the drilling machine 30 in a first position and spaced from a vertical axis extending through the drilling machine 30 in a second position.

[0015] The drilling (step (b)) may be carried out via the moonpool 20 of the vessel 10.

[0016] As shown in Figure 4, after drilling of the hole 12 is completed, the vessel 10 can be moved slightly from the drilling position and / or the drill string 13 can be skidded or moved away from the drilling position. As shown in Figures 5 and 6, the anchor member 14 is then lowered from the vessel 10 into the hole 12. The anchor member 14 can be lowered by a winch and an elongated lifting member 16, such as a rope or wire (see Figure 5). Support of the anchor member 14 from the vessel 10 during lowering can be provided via a crane 31 (see Figures 10-13). The anchor member 14 can be lowered through the moonpool 20 of the vessel 10, or optionally, can be lowered over the side (41) of the vessel 10. If the lowering of the anchor member 14 is supported by a crane 31, the elongated lifting member 16 may be a rope or wire located on the crane 31 (such as on a winch drum on the crane 31) or may be a rope or wire located in association with a separate winch on the vessel 10, where the rope or wire is guided via a sheave or the like held by the crane 31. If the anchor member 14 is lowered over the side of the vessel 10, a cantilever structure 40 (see FIG. 18) may optionally be used for guidance or support.

[0017] 5 and 6, a cementing hose 15 may be lowered along with the anchor member 14 and secured to the anchor member 14. The cementing hose 15 may be a tube or pipe operable to carry cement from the vessel 10 to fill the void between the anchor member 14 and the wall of the hole 12 to cement the anchor member 14 in place within the hole 12.

[0018] Alternatively, the cementing hose 15 may be provided separately from the anchor member 14, for example so that the cementing hose 15 is lowered separately from the vessel 10.

[0019] The cementing hose 15 can be handled by an ROV 17 controlled from the vessel 10 via a control umbilical 18 (see Figure 6).

[0020] After pumping cement into hole 12, cementing hose 15 can be removed from anchor 2. This can be done, for example, by ROV 17. ROV 17 can also or alternatively remove lifting member 16. Alternatively, cementing hose 15 and / or lifting member 16 can be removed via a release mechanism actuated by applying tension, for example, from vessel 10, e.g., via lateral or vertical tension applied to cementing hose 15 and / or lifting member 16.

[0021] After steps (a) to (d) have been performed, the vessel 10 can be moved to a new drilling location. Advantageously, the vessel 10 can be moved to a new drilling location with the drill string 13 suspended from the vessel 10, as shown in Figure 7. If required, after allowing time for the cement to settle, the anchor 2 can be installed and connected to a floating body by another vessel. Optionally, the vessel 10 can connect the anchor 2 to a mooring line or a floating body before moving away.

[0022] 8 shows anchor member 14. Anchor member 14 is preferably cylindrical and may have a variable cross-sectional diameter. For example, anchor member 14 may have a smaller diameter at its lower portion 14a and a larger diameter at its upper portion 14b.

[0023] The holes 12 may advantageously be drilled with a diameter of more than 500 mm, more than 750 mm, more than 1000 mm or more than 1250 mm.

[0024] Anchor member 14 may advantageously have a length that exceeds the diameter of hole 12 , that exceeds 150% of the diameter of hole 12 , or that exceeds 200% of the diameter of hole 12 .

[0025] 9a and 9b show a drilling machine 30 suitable for use on the vessel 10. The vessel 10 may have a support structure 11, such as a rig or tower structure, for holding the drilling machine 30. The drilling machine 30 and / or the support structure 11 may be positioned on the deck of the vessel 10. The drilling machine 30 may be a drilling machine operable to rotate a drill string 13.

[0026] Advantageously, the drill string 13 is suspended from the vessel 10 from a heave compensated drilling rig 30. This can be achieved by making the drilling rig heave compensated within the support structure 11.

[0027] Advantageously, the anchor member 14 is suspended from the vessel 10 from a motion compensated winch or crane 31. The winch or crane 31 may be separate from the excavator 30.

[0028] Optionally, the drill string 13 can be suspended from the vessel 10 as described above by leaving it hanging from the excavator 30 while the winch or crane 31 is operated to lower the anchor member 14 and perform the steps related to performing cementing.

[0029] As mentioned above, the seabed may include a soft soil layer 5 (see Figures 1 and 2) and a hard soil layer 6, the hard soil layer 6 being denser than the soft soil layer 5. The method may include drilling into the hard soil layer 6 and cementing the anchor member 14 at least partially within the hard soil layer 6.

[0030] The method may include removing a portion of the soft soil layer 5 prior to step (b). The soft soil layer 5 may be removed by excavating through the soft soil layer 5 before excavating into the hard soil layer 6. The vertical thickness of the soft soil layer 5 may be less than 5 m, less than 4 m, less than 3 m, or less than 2 m.

[0031] Any embodiment of the methods described herein may include lowering a guide base with a guide wire to the seabed 4 and drilling through the guide base. The guide wire may also be used to quickly access the drilled hole when advancing and landing the anchor member.

[0032] Figures 10-13 illustrate a vessel 10 that may be suitable for carrying out methods according to embodiments described herein. The vessel 10 comprises the components described above, including a support (rig or tower) structure 11 with a drilling machine 30 and a crane 31, which in this example is a knuckle boom crane. The vessel 10 has a moonpool 20 (see Figure 13) on its hull through which the drill string 13 and other components (such as a wire / rope elongated lifting member 16) can be lowered.

[0033] The vessel 10 has a deck 32 where associated components and equipment may be stored during operation. In particular, the vessel 10 may have storage locations for a plurality of anchor members 14 for installation on the deck 32 or elsewhere. In this manner, a large number of anchor members 14 may be available and ready for installation on the vessel 10, such as to enable efficient operations.

[0034] The vessel 10 may also be equipped with a fluid handling system 33 (see Figures 12 and 13) for handling drilling fluids and / or cement that may be required during the operations described above.

[0035] The anchor 2 can be designed to suit the expected soil and working conditions, for example in terms of its diameter, length, material properties, etc. The anchor 2 can support one mooring line 7 (see Figures 1 and 2) or, optionally, two or more mooring lines 7. For example, in a wind park with many floating wind turbines, one anchor 2 can provide support for two or more floating wind turbines, thereby reducing the total number of anchors required.

[0036] Advantageously, if the drill string 13 is allowed to be suspended from the vessel 10, the drill string 13 can be set up, lowered, and suspended in a standby position, for example in a moonpool, one time at a time, while other work activities are carried out. The other work activities can be carried out by a crane or winch, or a combination of a crane and winch. Once these other work activities, such as steps (c) and (d) above, are completed, the vessel 10 can move to the next installation site and commence the next drilling operation, without having to set up and lower the entire drill string 13.

[0037] In any of the embodiments described herein, for an anchor 2 suitable for use in a wind power floater, the diameter of the hole 12 may be, for example, approximately 1500 mm and the anchor member 14 may be approximately 700-1300 mm. However, for other applications, various other sizes may be relevant, depending on the wants and requirements of any particular case.

[0038] Before drilling operations begin, an on-board ROV may be deployed to inspect and, if necessary, measure the slope or other parameters of the seabed 4 .

[0039] Optionally, the vessel 10 may have the ability to skid or tilt the excavator 30 and associated components away from the moonpool area. This is shown in Figures 14 and 15 (see also Figures 9-13). The excavator 30 may be positioned to be supported by a support structure 11 that is movable relative to the rest of the structure of the vessel 10. For example, the support structure 11 may be skidable or tiltable relative to the moonpool 20.

[0040] This is shown in Figures 14 and 15, where the support structure 11 with the drilling rig 30 can be skidded relative to the moonpool 20. The support structure 11 can be skidded completely away from the opening defined by the moonpool 20, as shown in Figure 15, or only partially away from the opening. For example, if the drill string 13 remains suspended from the drilling rig 30, such as during lowering of the anchor member 14, the support structure 11 may be skidded only a sufficient distance to provide more space for other operations via the moonpool 20, but still allow the drill string 13 to remain suspended in the water below the vessel 10 from the drilling rig 30 through the moonpool 20.

[0041] Figure 16 shows how the support structure 11, or portions of the support structure 11, can be tilted to provide more space above the moonpool area. Optionally or additionally, the entire platform as shown in Figure 16 can be arranged to have the ability to skid laterally, similar to that shown in Figures 14 and 15.

[0042] Thus, step (b) of the method may involve operating the drilling rig 30 to drill a hole in the seabed 4, as described above, and then skidding or tilting the support structure 11 supporting the drilling rig 30. In this way, the support structure 11, drilling rig 30 or other associated components may be moved out of the way so that other operations via the moonpool 20 can be more easily performed.

[0043] As shown in Figure 17, the method may include generating a liquid flow from the drill string head 13' upwardly within the drill string 13 to the vessel 10. In this embodiment, the method may include receiving soil particles or cuttings 19 onto the vessel 10 via the liquid flow. The soil particles or cuttings 19 may be received on board the vessel 10 for storage, processing, or transport away. In this manner, the soil particles or cuttings 19 do not need to be dumped on the seabed 4.

[0044] By carrying out the drilling as a reverse circulation drilling (RCD) process, it is possible to have the advantage that soil particles or cuttings 19 can be transported off-site in or around the hole 12 .

[0045] The liquid flow within the drill string 13 may be generated, for example, by gas lift, i.e., by injecting a gas (such as air) into the drill string 13. The liquid flow including the soil particles or cuttings 19, if present, may be received via a return line 21 arranged in relation to the drilling machine 30, as can be seen in Figures 9a and 9b. For example, the return line 21 may be connected to a liquid treatment system for separating the liquid from the soil particles or cuttings 19, for further treatment of the liquid, or for discharge of the liquid.

[0046] Advantageously, portions of the soft formation 5 may be removed in areas of the seabed that are larger than the cross-sectional area of ​​the drill string head 13' or larger than the cross-sectional area of ​​the drill string 13. This is shown in Figure 17, where a reverse circulation flow may be used to remove soil particles from the soft formation 5 over an area that is larger than the cross-sectional area required for the hole 12. This has the advantage that there may be less risk of the hole 12 collapsing or the risk of disruption of operations is reduced.

[0047] The method may include positioning a lower end of the drill string 13, such as a drill string head 13′, above and adjacent to or within the soft formation 5 while suspending the drill string 13 from the vessel 10 and generating a liquid flow within the drill string 13 and upward to the vessel 10. In this embodiment, for example, the lower end may hover above the soft formation 5 while the vessel 10 is moving, such that a greater area of ​​the soft formation 5 is removed and transported to the vessel 10 via the liquid flow within the drill string 13.

[0048] As can be seen, for example, in Figures 9a and 9b, the drilling machine 30 may be supported by a support structure 11 on the vessel 10. The support structure 11 provides rotational support for the drilling machine 30 in a horizontal plane as the drilling machine 30 applies moments to the drill string 13 to rotate it, and may therefore hold the drilling machine 30 rotatably fixed relative to the vessel 10. Advantageously, the support structure 11 comprises a motion compensated frame 11' that supports the drilling machine 30. The motion compensated frame 11' may comprise, for example, vertically arranged hydraulic cylinders that allow vertical movement of the drilling machine 30 in response to vessel motions.

[0049] Alternatively, the excavator 30 can be suspended by a sway-compensated crane 31 (see FIGS. 10-13). In such an arrangement, the crane 31 can be arranged to hold the excavator 30 vertically, for example, by suspending the excavator 30 from the crane via a hook or the like. The support structure 11 can be arranged to provide rotational support for the excavator 30 as described above, but to allow the excavator 30 to move freely in a vertical direction, for example, along tracks or support rods. A movable frame similar to frame 11' can be used for this purpose. To provide sway compensation capability for the excavator 30, the crane 31 can be operated in a sway-compensated mode to hold the excavator 30.

[0050] In any of the embodiments herein, the motion compensation may be passive motion compensation or active motion compensation.

[0051] 18 , in any of the embodiments described herein, the method may optionally be performed on the side of the vessel via a cantilever structure 40 extending outward from the side of the vessel 41. This may include constructing the drill string 13 from the cantilever structure 40 such that the drill string 13 is suspended (directly or indirectly) from the cantilever structure 40.

[0052] Additionally or alternatively, the anchor member 14 may be lowered from the vessel 10 via the cantilever structure 40, for example, by suspending the anchor member 14 directly or indirectly from the cantilever structure 40 during lowering, or by, for example, a lateral support of the lifting member 16 during lowering.

[0053] 19-24 illustrate various embodiments of anchor members 14 suitable for use in the methods described herein. The anchor members 14 may have suspension members 44, such as shackles or hooks, from which the anchor members 14 may be suspended and lowered from the vessel 10 via lifting members 16.

[0054] Advantageously, anchor member 14 may have a perforated lower portion 14a, which may allow cement to be distributed in and around anchor member 14 in a manner beneficial to secure anchor member 14 within hole 12.

[0055] The lower portion 14b can be formed as a hollow elongated tube, see for example Figures 19, 21 and 23.

[0056] The anchor member 14 may include an injection tube probe 45 arranged to inject cement into the interior of the anchor member 14. The anchor member 14 may be arranged hollow for this purpose, for example in the form of an elongated cylinder, so that the interior volume of the anchor member 14 can be filled with cement via the injection tube probe 45. The injection tube probe 45 may extend downwardly within the interior of the anchor member 14.

[0057] The cementing hose 15 may be connected to the injection tube probe 45 before the anchor member 14 is lowered to the seabed 4. Alternatively, the cementing hose 15 may be connected to the injection tube probe 45 after the anchor member 14 has been lowered, for example with the assistance of the ROV 17. In this manner, the anchor member 14 may be cemented by filling the interior volume of the anchor member 14 with cement in addition to filling the annular volume around the anchor member 14 in the hole 12. Optionally, the anchor member 14 may be cemented in place in the hole 12 by filling the annulus around the anchor member 14 in the hole 12 with cement.

[0058] If the injection tube probe 45 extends into the interior volume of the anchor member 14, the method may include using an on-board cement reel and assisted by the ROV 17 to retract the injection tube probe 45 from within the anchor member 14 during the cementing operation to achieve improved cement distribution both within the anchor member 14 and in an annulus surrounding the anchor member 14.

[0059] FIG. 25 shows an embodiment of the vessel 10 having an alternative support structure 11 for holding and suspending the excavator 30 .

[0060] The embodiments described herein may be suitable for the installation of floating renewable energy installations, such as floating wind power plants. According to the embodiments, more flexible installation of mooring and anchoring systems may be achieved. For example, structurally reliable moorings in different or variable soil conditions may be obtained, and operations may be less sensitive to water depth. Additionally or alternatively, high installation efficiency may be achieved, allowing the use of less specialized installation vessels and / or reducing dependency on weather windows. This may be advantageous, for example, in the installation of large renewable energy parks where a large number of mooring points are required.

[0061] Advantageously, the vessel 10 may further be equipped to install suction anchors. The possibility of performing such "dual" operations may provide the advantage of more efficient operations, for example in areas with variable soil conditions where a combination of suction anchors and cemented anchors may be used.

[0062] The systems and methods may be employed using lighter weight vessels than those typically used for offshore drilling operations, for example, vessels known as offshore work vessels may be suitable for this purpose.

[0063] Further inventive aspects and embodiments according to the present disclosure are provided in the following numbered clauses: 1. A method for installing a submarine anchor (2), comprising: (a) constructing a drill string (13) from a vessel (10); (b) drilling a hole (12) in the seabed (4); (c) lowering the anchor member (14) from the vessel (10) into the hole (12); (d) cementing the anchor member (14) in place in the hole (12) via a cementing hose (15) from the vessel (10); A method comprising: 2. The method of the preceding clause, wherein step (b) includes drilling through a moonpool (20) of the vessel (10). 3. The method of any preceding clause, wherein step (a) includes constructing the drill string (13) from a cantilever structure (40) extending outward from a side (41) of the vessel (10). 4. The method of any preceding clause, wherein step (c) includes lowering the anchor member (14) through a moonpool (20) of the vessel (10). 5. The method of any preceding clause, wherein step (c) includes lowering the anchor member (14) from the vessel (10) onto a side (41) of the vessel (10). 6. The method of any preceding clause, wherein step (c) includes lowering the anchor member (14) from the vessel (10) via a cantilever structure (40) extending outward from a side (41) of the vessel (10). 7. The method of any preceding clause, including suspending the drill string (13) from the vessel (10) while performing steps (c) and (d). 8. The method of the preceding clause, wherein suspending the drill string (13) from the vessel (10) while performing steps (c) and (d) includes suspending the drill string (13) through a moonpool (20). 9. The method of any preceding clause, including skidding or otherwise moving the drill string (13) laterally before performing steps (c) and (d). 10. A method according to any preceding clause, comprising, after carrying out steps (a) to (d), moving the vessel (10) to a new drilling location with the drill string (13) suspended from the vessel (10). 11. A method according to any preceding clause, comprising lowering the anchor member (14) from the vessel (10) via a crane. 12. A method according to any preceding clause, comprising lowering a guide base having a guide wire thereon to the seabed (4) and drilling through the guide base. 13. The method of any preceding clause, wherein step (c) includes lowering a cementing hose (15) together with the anchor member (14) and securing it to the anchor member (14). 14. A method according to any preceding clause, including providing a cementing hose (15) separately from the anchor member (14), for example by an ROV (17) controlled from the vessel (10) via a control umbilical (18). 15. The method of any preceding clause, including, following step (d), removing the cementing hose (15) from the anchor (2). 16. The method of the preceding clause, wherein the step of removing the cementing hose (15) from the anchor (2) includes removing the cementing hose (15) from the anchor (2) using an ROV (17). 17. The method of any preceding clause, wherein the anchor member (14) is cylindrical. 18. The method of any preceding clause, wherein the anchor member (14) has a circular cross-section of variable diameter. 19. The method of the preceding clause, wherein the anchor member (14) has a smaller diameter at a lower portion and a larger diameter at an upper portion. 20. The method of any preceding clause, wherein step (b) includes drilling a hole (12) having a diameter greater than 500 mm, greater than 750 mm, greater than 1000 mm, or greater than 1250 mm. 21. The method of any preceding clause, wherein the anchor member (14) has a length that exceeds the diameter of the hole (12), exceeds 150% of the diameter of the hole (12), or exceeds 200% of the diameter of the hole (12). 22. The method of any preceding clause, wherein step (b) includes suspending the drill string (13) from the vessel (10) from a motion compensated drilling rig (30). 23. A method according to any preceding clause, wherein the excavator (30) is supported by a support structure (11) on the vessel (10). 24. The method of any preceding clause, wherein the support structure (11) includes a sway compensated frame supporting the excavator (30). 25. The method of any preceding clause, wherein the excavator (30) is suspended by a sway compensated crane (31). 26. The method of any preceding clause, wherein the support structure (11) provides rotational support to the excavator (30) in a horizontal plane. 27. The method of any preceding clause, wherein step (c) includes suspending the anchor member (14) from the vessel (10) from a winch or crane (31). 28. The method of any preceding clause, wherein step (c) includes suspending the anchor member (14) from the vessel (10) from a motion compensated winch or crane (31). 29. The method of any preceding clause, wherein step (c) includes suspending the anchor member (14) from the vessel (10) from a winch or crane (31) that is independent of the excavator (30). 30. A method according to any preceding clause, wherein the seabed comprises a soft soil layer (5) and a hard soil layer (6), the hard soil layer (6) being denser than the soft soil layer (5), and the method comprises drilling into the hard soil layer (6) and cementing the anchor member (14) at least partially within the hard soil layer (6). 31. A method according to any preceding clause, including removing a portion of the soft soil layer (5) before step (b). 32. A method according to any preceding clause, including drilling a hole through the soft soil layer (5) before the step of drilling a hole in the hard soil layer. 33. The method according to any preceding clause, wherein the vertical thickness of the soft soil layer (5) is less than 5 m, less than 4 m, less than 3 m, or less than 2 m. 34. A method according to any preceding clause, wherein step (b) includes operating a drilling machine (30) to drill a hole in the seabed (4), and the method includes skidding or tilting a support structure (11) supporting the drilling machine (30) between steps (b) and (c). 35. The method of any preceding clause, wherein step (b) includes generating a liquid flow from the drill string head (13') upwardly within the drill string (13) to the vessel (10). 36. The method of any preceding clause, comprising receiving soil particles or cuttings (19) on a vessel (10) via a liquid stream. 37. The method of any preceding clause, wherein step (b) is performed as a reverse circulation drilling (RCD) drilling process. 38. A method according to any preceding clause, comprising removing a portion of the soft formation (5) via a liquid flow from the drill string head (13') upwardly within the drill string (13) to the vessel. 39. A method according to any preceding clause, wherein a portion of the soft formation (5) is removed in an area of ​​the seabed that is larger than the cross-sectional area of ​​the drill string head (13') or larger than the cross-sectional area of ​​the drill string (13). 40. A method as in any preceding clause, comprising suspending the drill string (13) from the vessel (10) and positioning a lower end of the drill string (13), such as a drill string head (13'), above and adjacent to or within the soft formation (5) while generating a flow of liquid within the drill string (13) flowing upward to the vessel (10). 41. A method according to any preceding clause, comprising moving the vessel (10) while hovering said lower end above the soft layer (5).

[0064] The invention is not limited to the above-described embodiments, but reference should be made to the appended claims.

Claims

1. A method for installing a subsea anchor (2), comprising the steps of: (a) constructing a drill string (13) from a vessel (10); (b) drilling a hole (12) in the seabed (4); (c) lowering an anchor member (14) from said vessel (10) into said hole (12); (d) cementing the anchor member (14) in place in the hole (12) via a cementing hose (15) from the vessel (10); Including, After performing steps (a) to (d), the method includes moving the vessel (10) to a new drilling site with the drill string (13) suspended from the vessel (10).

2. 2. The method of claim 1, wherein step (b) comprises drilling through a moonpool (20) of the vessel (10).

3. 3. The method of claim 1 or 2, wherein step (c) comprises lowering an anchor member (14) through a moonpool (20) of the vessel (10).

4. A method according to any one of claims 1 to 3, comprising suspending the drill string (13) from the vessel (10) while steps (c) and (d) are carried out.

5. 5. A method according to any one of claims 1 to 4, comprising skidding or otherwise moving the drill string (13) laterally before carrying out steps (c) and (d).

6. Any one of claims 1 to 5, wherein step (c) includes lowering the cementing hose (15) together with the anchor member (14) and fixing it to the anchor member (14).

1. The method according to claim 1.

7. A method according to any preceding claim, wherein step (b) comprises drilling the hole (12) to a diameter of more than 500mm, more than 750mm, more than 1000mm or more than 1250mm.

8. A method according to any preceding claim, wherein step (b) comprises suspending the drill string (13) from the vessel (10) from a motion compensated drilling machine (30).

9. 9. A method according to any preceding claim, wherein step (b) comprises generating a liquid flow from a drill string head (13') upwardly within the drill string (13) to the vessel (10).

10. 10. The method of claim 9, comprising receiving soil particles or cuttings (19) on a vessel (10) via the liquid flow.

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