Mooring assembly

Abstract

A mooring assembly for attaching a vessel to a subsea well, the subsea well comprising a well conduit, the mooring assembly comprising: (a) a housing for the well conduit; (b) a base defining an interface for a subsea surface; and (c) a rotatably mounted ship attachment point; wherein, in use, a vessel moored to the subsea well is capable of rotational movement about the subsea well.

Description

[0001] This application is a divisional application of a prior application filed on April 9, 2020, with application number CN202080028402.6 and invention name “Mooring Component”. Technical Field

[0002] The present invention relates to a mooring assembly for attaching a vessel to a subsea well. The present invention also relates to a method for installing a mooring assembly for a vessel to a subsea well and a method for mooring a vessel to a subsea well, wherein after mooring the vessel is able to perform a rotational movement around the subsea well. The mooring assembly allows control of the well and production from the well to the vessel. Background Art

[0003] The cost of current solutions for developing natural resources in the oil and gas sector means that many smaller oil and gas fields cannot be developed economically.

[0004] The present invention seeks to provide a solution that enables the commercialization of small scale oil and gas fields to be achieved safely by allowing the well to be produced without many of the components traditionally required. Summary of the invention

[0005] According to a first aspect of the present invention, there is provided a mooring assembly for attaching a vessel to a subsea well, the subsea well comprising a well conductor, the mooring assembly comprising:

[0006] (a) A casing for a well casing;

[0007] (b) defining a base for the interface with the sea floor; and

[0008] (c) rotatably mounted vessel attachment points;

[0009] Therein, during use, a vessel moored to the subsea well is capable of performing a rotational movement around the subsea well.

[0010] According to a second aspect of the present invention, there is provided a method for installing a mooring assembly of a vessel to a subsea well, the subsea well comprising a well conductor, the method comprising the following steps:

[0011] (a) providing a mooring assembly including a base; and

[0012] (b) rotatably mounting the mooring assembly to the well conductor at or near the seafloor surface;

[0013] Therein, during use, a vessel moored to the subsea well is capable of performing a rotational movement around the subsea well.

[0014] According to a third aspect of the present invention there is provided a method of mooring a vessel to a subsea well, the method comprising the step of attaching the vessel to the subsea well by means of a mooring assembly as described herein, wherein after mooring the vessel is capable of rotational movement around the subsea well.

[0015] It will be appreciated that other aspects, preferred forms and advantages of the present invention will become apparent from the present specification including the detailed description, examples, drawings and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to facilitate a better understanding of the present invention, preferred embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

[0018] Figure 1A is a side view of a mooring component according to a first embodiment of the first aspect of the present invention;

[0019] Figure 1B for Figure 1A a top view of the mooring assembly shown;

[0020] Figure 1C for Figure 1A a perspective view of the mooring assembly shown, including partial cutaway to show further details of the mooring assembly;

[0021] Figure 2A is a side view of a mooring component according to a second embodiment of the first aspect of the present invention;

[0022] Figure 2B for Figure 2A a top view of the mooring assembly shown;

[0023] Figure 2C for Figure 2A a perspective view of the mooring assembly shown, including partial cutaway to show further details of the mooring assembly;

[0024] Figure 2D For along Figure 2B Section view of the middle section line AA;

[0025] Figure 3A-3H is a series of schematic diagrams showing a method for installing a mooring assembly of a vessel to a subsea well according to an embodiment of the second aspect of the present invention;

[0026] Fig. 3I and Figure 3J Shows Figure 3H A production well in a production well equipped with a mooring assembly that combines a flow controller (Christmas tree) and an anchor line ( Figure 3J );and

[0027] Figure 4A perspective view including a section showing a portion of a production well Figure 1A Mooring components shown. DETAILED DESCRIPTION

[0028] According to a first aspect of the present invention, there is provided a mooring assembly for attaching a vessel to a subsea well, the subsea well comprising a well conductor, the mooring assembly comprising:

[0029] (a) A casing for a well casing;

[0030] (b) defining a base for the interface with the sea floor; and

[0031] (c) rotatably mounted vessel attachment points;

[0032] Therein, during use, a vessel moored to the subsea well is capable of rotating around the subsea well.

[0033] The term "well conductor" as used in the present invention may include any well pipe, housing (housing), pipeline or any other similar component suitable for providing the main support structure of a submarine well, and includes a conductor pipe (conductor casing) located at or near the wellbore. The well conductor may include a portion located above the wellbore at the seafloor surface hole. The well conductor may also include a portion located below the wellbore.

[0034] Preferably, the mooring assembly defines a single mooring point on the sea bed.

[0035] The mooring assembly may be adapted to allow a vessel moored thereto to steer through 360 degrees. Preferably, the mooring assembly is adapted to allow a vessel moored thereto to steer in either direction.

[0036] Preferably, the mooring assembly comprises a guide base, such as a permanent guide base.

[0037] Preferably, the housing defines a conduit for well conduit.

[0038] Preferably, the pipe is located at a central position in the shell.

[0039] Preferably, the above-mentioned duct comprises a circular cross-section.

[0040] Preferably, the conduit defines upper and lower ends and an inner surface therebetween, the inner surface having a profile sized and shaped to allow the housing to form a casing or jacket around a well conduit.

[0041] Preferably, the housing comprises fixing means to enable it to be fixed in position relative to the well conductor.

[0042] Preferably, the fixture is adapted to allow the housing and the well conduit to form a frictional engagement. Even more preferably, the fixture comprises a first mating surface disposed on the housing and compatible with a second mating surface on the well conduit. In a particular form of the invention, the first mating surface is disposed on an inner surface of the housing and compatible with a second mating surface disposed on an outer surface of the well conduit. The first mating surface may comprise a pin, a ball, a hole, a protrusion, a blade or a channel.

[0043] Preferably, the first mating surface is compatible with a second mating surface comprising a pin, a ball, a hole, a protrusion, a blade or a channel.

[0044] Preferably, the housing further comprises a positioning device for positioning the well casing therein. In this regard, when the well casing is installed from above, the positioning device makes it easier to land and install the well casing, or at least helps guide the well casing into the wellbore.

[0045] Preferably, the well casing is a well surface casing.

[0046] Preferably, the positioning means is adapted to centre the well casing in the housing or, when the housing comprises a pipe, to centre the well casing in said pipe.

[0047] Preferably, the positioning device is integrally provided with the pipeline.

[0048] Preferably, the positioning device is located at or towards the upper end of the pipe.

[0049] Preferably, the positioning device comprises a contact surface for the front end of the well casing and extends outwardly from the inner surface of the pipe.

[0050] The contact surface may extend around the entire upper end of the pipe or around a portion of the upper end of the pipe.

[0051] Preferably, the positioning means comprises a protrusion, such as a lip or a shoulder.

[0052] Preferably, the above-mentioned positioning means comprises a circumferential protrusion.

[0053] Preferably, the housing further comprises a guide device to further assist in placing the sleeve in the housing.

[0054] Preferably, the guide means comprises a body defining a bore having an opening wider than an opening at an upper end of the duct.

[0055] Preferably, the guide device comprises a tubular, funnel-shaped, drum funnel-shaped or barrel-shaped member.

[0056] Preferably, the guide device is located adjacent to and above the positioning device. Even more preferably, the guide device is integrally arranged with the positioning device.

[0057] Preferably, the housing defines a mounting point for the rotatably mounted vessel attachment point. Preferably, the mounting point is located on an outer surface of the conduit. Preferably, the mounting point is a surface of suitable size and shape that is compatible with the rotatably mounted vessel attachment point.

[0058] Preferably, the base comprises at least one engagement means for the sea floor. Even more preferably, the base comprises a plurality of said engagement means.

[0059] The engagement means for the seabed surface at least restricts movement of the base relative to the seabed surface, such as lateral and / or rotational movement. Preferably, the engagement means secures the mooring assembly in position relative to the seabed surface. In this regard, preferably, the engagement means locks the mooring assembly to the seabed surface (e.g., the seabed) such that the mooring assembly cannot rotate, move axially (pull out), or move laterally (tilt).

[0060] Preferably, the above-mentioned engagement means for the sea floor are arranged around the above-mentioned base. Even more preferably, the engagement means are arranged equidistantly spaced around the base.

[0061] Preferably, the above-mentioned engagement means for use with the subsea floor comprises projections, such as feet, legs, stabs or blades.

[0062] The above-mentioned engagement means for use with the seafloor surface may include at least one arm or brace extending laterally from the above-mentioned base to allow the above-mentioned interface to extend over a larger area of ​​the seafloor surface. When the above-mentioned engagement means includes an arm or brace, the above-mentioned protrusion may be arranged at or near the distal end of the arm or brace.

[0063] Preferably, the above-mentioned engagement device for the seabed ground is adapted to be inserted into the seabed ground when in use. Alternatively, the above-mentioned engagement device for the seabed ground may be adapted to receive additional anchors, such as stakes / piles, screws or spikes, to increase the engagement strength with the seabed ground.

[0064] The base may include spacer means to allow a gap to be formed between the base and the sea floor when in use.

[0065] The above-mentioned spacing means may be the above-mentioned protrusion or other feature of the base.

[0066] Preferably, the spacer extends from a lowermost surface of the base.

[0067] When cement is used to secure the well casing therein, the voids allow for visual confirmation of the cement returning to the surface.

[0068] The housing may further include at least one inspection port or viewing window to allow for confirmation of returned cement when no voids are formed or returned cement is otherwise not visually confirmed.

[0069] Preferably, the above-mentioned gap or inspection port is adapted to allow the passage of fixing material such as mortar, glue or concrete to an area adjacent to the lower part of the base. Preferably, the area is one or more of the area between the base and the seabed surface, between the base and another feature of the mooring assembly, and / or between the base and a seabed well (e.g., a well conduit).

[0070] Preferably, the base comprises a skirt extending radially outwardly from the main longitudinal axis of the housing. Preferably, the skirt is located at the lower end of the duct and is integrally provided with one or more of the duct, the engaging means and / or the spacing means.

[0071] Preferably, the mount is used to reinforce the mooring assembly and / or provide support for at least one other component of the mooring assembly, such as a rotatably mounted vessel attachment point, more particularly a bearing member (described in more detail below).

[0072] Preferably, said rotatably mounted vessel attachment point is mounted to said hull. Even more preferably, said rotatably mounted vessel attachment point is mounted to the hull at a point below said positioning means.

[0073] Preferably, the above-mentioned rotatably mounted vessel attachment point comprises at least one bearing member.Even more preferably, the rotatably mounted vessel attachment point comprises a plurality of bearing members.

[0074] Preferably, the bearing member defines a tapered bearing surface.

[0075] Preferably, the tapered bearing surface tapers toward its lower end.

[0076] Preferably, the bearing member is a roller bearing, such as a tapered roller bearing or a rollercone bearing.

[0077] Preferably, the bearing member comprises at least one port for delivering lubricant to the at least one bearing member, for example a port accessible by a ROV.

[0078] Preferably, the rotatably mounted vessel attachment point includes an attachment member for releasably receiving a vessel anchor line or hawser.

[0079] Preferably, the attachment member comprises a padeye, a loop or a shackle.

[0080] Preferably, the rotatably mounted vessel attachment point comprises at least one extending arm between the bearing member and the attachment member to provide lateral spacing between the attachment member and the bearing member. Even more preferably, the rotatably mounted vessel attachment point comprises two arm members.

[0081] According to a second aspect of the present invention, there is provided a method for installing a mooring assembly of a vessel to a subsea well, the subsea well comprising a well conductor, the method comprising the following steps:

[0082] (a) providing said mooring assembly including a base; and

[0083] (b) installing the mooring assembly to the well conductor at or near the seabed surface;

[0084] Wherein, during use, a vessel moored to the subsea well can perform a rotational movement around the subsea well.

[0085] Preferably, the mooring component is a mooring component as described herein.

[0086] Preferably, the mooring assembly is mounted to the well conductor by grounding it on the well conductor.

[0087] Preferably, the mooring assembly frictionally engages with, or is securable or fastenable to, the well conductor.

[0088] Preferably, the mooring assembly is rotatably mounted to the well conductor such that it defines a void at the interface between the base and the seafloor surface or otherwise allows visual confirmation of cement returning to the seafloor surface as the well conductor is cemented therein.

[0089] Preferably, the method further comprises the step of securing the mooring assembly to the well conductor.Preferably, the step of securing the mooring assembly to the well conductor comprises latching or otherwise securely fastening the mooring assembly to the well conductor.

[0090] Preferably, the method further comprises the step of extending the well casing by installing a further well casing to said mooring assembly.

[0091] Preferably, the method further comprises the step of installing a flow control device (eg a Christmas tree) to the well conduit.

[0092] According to a third aspect of the invention there is provided a method for mooring a vessel to a subsea well, the method comprising the steps of attaching the vessel to the subsea well by means of a mooring assembly as described herein and wherein, when moored, the vessel is capable of rotational movement about the subsea well.

[0093] Overview

[0094] Those skilled in the art will appreciate that, in addition to those specifically described herein, various variations and modifications may be made to the present invention. The present invention includes all such variations and modifications. The present invention also includes all steps and features mentioned or indicated in the specification individually or jointly and any and all combinations or any two or more steps or features.

[0095] Each document, reference, patent application or patent cited in this article is expressly incorporated herein by reference in its entirety, which means that the reader should read it and consider it as a part of this article. For the sake of brevity, the cited documents, references, patent applications or patents are not repeated in this article. However, the cited materials or the information contained in the materials should not be understood as common knowledge.

[0096] The scope of the present invention is not limited by any specific embodiments described herein. These embodiments are for illustrative purposes only. Functionally equivalent products and methods are clearly within the scope of the present invention described herein.

[0097] The invention described herein may include one or more numerical ranges (e.g., dimensions, etc.). Numerical ranges will be understood to include all values ​​within the range, including the values ​​defining the range, and values ​​adjacent to the range (these values ​​result in the same or substantially the same results as the values ​​immediately adjacent to the limits of the range).

[0098] In this specification, unless the context requires otherwise, the word "comprising" will be understood to imply the inclusion of a specified object or group of objects but not the exclusion of any other object or group of objects.

[0099] Other definitions of selected terms used herein can be found in the detailed description of the present invention and apply to the entire text. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by ordinary technicians in the field to which the present invention belongs.

[0100] The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make this disclosure thorough and complete and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements.

[0101] Preferred Embodiments

[0102] A mooring assembly according to an embodiment of the first aspect of the present invention is Figures 1A to 1C 1, and generally indicated by reference numeral 10, comprises a housing for a well conductor, the housing defining a centrally located conduit 12 having a circular cross-section 14. The conduit 12 has an upper end 16 and a lower end 18, and an inner surface 20 therebetween, the profile of which is sized and shaped to receive a standard well conductor having a circular cross-section, such as a surface casing. The mooring assembly 10 can be assembled on the well conductor by passing through the free end of the installed well conductor to form a casing arrangement on the well conductor.

[0103] The housing includes a fixing device (not shown) so that it can be fixed in place relative to the well pipe in the form of a first mating surface (not shown) on the inner surface 20, which is configured to cooperate with a second mating surface (not shown) on the outer surface of the well pipe.

[0104] The housing also includes a locating means for locating a sleeve therein in the form of a shoulder 22, wherein the shoulder 22 is integrally provided with and located at the upper end 16 of the pipe 12. The shoulder 22 protrudes circumferentially from the entire upper end 16 of the pipe 12 and extends around it.

[0105] The housing also includes a guide in the form of a cup 24 integral with and positioned adjacent to and above the shoulder 22. The cup 24 defines a bore having an opening and a cross section wider than the cross section 14 of the duct 12.

[0106] The mooring assembly also includes a base 26 defining an interface for the seabed surface. The base 26 includes a skirt 28 extending radially from the main longitudinal axis of the pipe 12 and integrally provided with the lower end 18 of the pipe 12 and engagement means in the form of a plurality of blades 30, wherein the blades 30 include feet 32 ​​extending downwardly from the skirt 28 and adapted to penetrate the seabed surface when in use. The blades 30 including the feet 32 ​​are arranged around the skirt 28 and are equally spaced.

[0107] The blades 30 including the feet 32 ​​also form a spacer to allow a gap to be formed between the skirt 28 and the sea floor when in use. The gap 34 is best shown at Figure 3C , allowing the return of the fixing material (e.g., concrete) to be seen during installation (see Figure 3A-3J ).

[0108] The mooring assembly 10 also includes a rotatably mounted vessel attachment point in the form of a pair of extension arms 36a, 36b which are mounted at one end to the pipe 12 via bearing members in the form of upper and lower radial bearings 38a, 38b which are housed within a bearing housing 40. The other ends of the extension arms 36a, 36b are attached to an attachment member in the form of an eye plate 42 for releasably receiving a vessel's anchor line or cable.

[0109] A mooring component according to another embodiment of the first aspect of the present invention is Figure 2A-2D The embodiment is generally indicated by the reference numeral 100. This embodiment includes many features corresponding to those of the first embodiment, and these corresponding features are shown in FIG. Figure 2A-2D Medium Figure 1A-Figure 1C The corresponding reference numerals used in the drawings are indicated.

[0110] Figure 2A-2D The embodiment shown in FIG. 1 differs primarily in the interface for the seafloor surface. The base 26 includes a skirt 28 extending radially from the main longitudinal axis of the pipe 12 and integrally provided with the lower end 18 of the pipe 12, and Figure 1A-Figure 1C . However, the engagement means is in the form of a plurality of modified blades 130 in combination with three equally spaced arms 150a, 150b and 150c extending downwardly from the skirt 28 and extending laterally from the base 26, thereby allowing the interface to extend over a greater area of ​​the seafloor surface. Each distal end of the arms 150a, 150b and 150c includes a protrusion in the form of a foot 152a, 152b and 152c defining an eyelet 154a, 154b and 154c adapted to receive an additional anchor, such as a stake (pile) or a spike.

[0111] With Figure 1A-Figure 1C In a similar manner to the first embodiment shown, in the second embodiment, the blades 30 and feet 152a-c form a spacer to allow a gap to be formed between the skirt 28 and the sea floor in use, thereby allowing the fixing material (e.g. cement or concrete) to be seen to return during installation (see Figure 3A-3J If the mooring assembly is flush with the sea floor, the housing may also include at least one inspection or viewing port to enable the return of fixing material or grout to be seen during installation.

[0112] FIG. 3A to FIG. 3J A method of installing a mooring component according to an embodiment of the second aspect of the invention is shown.

[0113] Drilling a hole 60 on the seafloor surface ( Figure 3A ) and introduce the well conduit 62 therein ( Figure 3B ) thereafter, the mooring assembly (generally indicated by reference numeral 110) is landed on the well conduit 62 at or near the seafloor surface 60 ( Figure 3C ). Spacers (not shown) in the mooring assembly 110 allow a gap 34 to be formed between the mooring assembly 110 and the seafloor surface 60 ( Figure 3C ), thereby allowing the injected fixing material 112 such as concrete or cement used to fix the well casing 62 to be seen returning to the seabed or rock layer of the top borehole ( Figure 3D Cement 112 extends downwardly into the borehole to ensure a secure engagement between the mooring assembly 110 and the well conductor 62.

[0114] Once the mooring assembly 110 is fixed to the well casing with cement, other well casings ( Figure 3E ), for example, surface casing 114; further drilling ( Figure 3F ), other casings (e.g., intermediate casing 116, Figure 3G ) can be installed according to conventional drilling operations. Finally, the production tubing 118 ( Figure 3H ) and such as Christmas trees 120 ( Fig. 3I ) and other flow controllers to configure the well for production.

[0115] Once the installation is complete ( Figure 3H ), the oil well can be collected from a floating production vessel (not shown) moored to the well guide tube 62 via the anchor cable 122 via the mooring assembly 110 on the sea surface ( Fig. 3I and Figure 3J ). The vessel, while attached to the mooring assembly 110, can freely move, rotate or provide a "weather vane" around the subsea well.

[0116] Figure 4 The schematic diagram including a cross section shows a mooring assembly 10 according to a first embodiment as part of a production well, the production well including a flow controller (ie, a Christmas tree 120) connected to the casing via a wellhead connector 180. Figure 4 The same reference numerals are used for features in .

Claims

1. A mooring assembly for attaching a vessel to a subsea well, the subsea well comprising a well guide, the mooring assembly comprising: (a) a housing adapted to be secured to the well conductor and including a rotatably mounted vessel attachment point extending laterally from the housing; (b) a base defining an interface for the seafloor surface; and Wherein, in use, a vessel moored to the subsea well is capable of performing a rotational movement around the subsea well.

2. The mooring assembly according to claim 1, wherein: The well conduit includes a conduit or a conduit casing.

3. The mooring assembly according to claim 1, wherein: The housing includes a first mating surface that is compatible with a second mating surface on the well conduit.

4. The mooring assembly of claim 1, adapted to allow a vessel moored thereto to change direction with the wind within 360 degrees.

5. The mooring assembly according to claim 1, wherein: The housing defines a conduit for the well conduit.

6. A mooring assembly according to claim 5, wherein: The conduit defines upper and lower ends and an inner surface therebetween, the inner surface having a profile sized and shaped to allow the housing to form a casing or jacket around the well conduit.

7. The mooring assembly according to claim 1, wherein: The housing is adapted to be fixed in position relative to the well conductor pipe by fixing means for forming a frictional engagement between the housing and the well conductor pipe.

8. The mooring assembly according to claim 7, wherein: The fixing device includes a first mating surface disposed on the housing and compatible with a second mating surface on the well conductor pipe.

9. A mooring assembly according to claim 8, wherein: The first mating surface includes a pin, a ball, a hole, a protrusion, a blade or a channel.

10. A mooring assembly according to claim 8 or 9, wherein: The second mating surface includes a pin, a ball, a hole, a protrusion, a blade or a channel.

11. The mooring assembly according to claim 1, wherein: The housing also includes a positioning device for centering the well casing therein.

12. The mooring assembly according to claim 11, wherein: The housing comprises a tubing, and the positioning device is adapted to center the well casing in the tubing.

13. The mooring assembly of claim 1, wherein: The housing also includes a guide device to further assist in landing the well casing within the housing.

14. The mooring assembly of claim 1, wherein: The base comprises at least one engagement means for the sea floor.

15. A mooring assembly according to claim 14, wherein: The engagement means for use with a subsea floor comprises a protrusion.

16. The mooring assembly of claim 14, wherein: The engagement means for use with a subsea surface comprises at least one arm or brace extending laterally from the base to allow the interface to extend over a greater area of ​​the subsea surface.

17. The mooring assembly of claim 14, wherein: The engagement device for use on a subsea surface is adapted to receive an additional anchor.

18. An anchor according to claim 17, wherein: The additional anchors are posts, screws or spikes.

19. The mooring assembly of claim 1, wherein: The base further comprises spacer means to allow a gap to be formed between the base and the sea floor in use, and wherein the gap is adapted to allow the passage of securing material to an area adjacent a lower portion of the base.

20. The mooring assembly of claim 1, wherein: The base includes a skirt or at least one arm extending radially outwardly from a major longitudinal axis of the housing.

21. The mooring assembly of claim 1, wherein: The rotatably mounted marine vessel attachment point includes at least one bearing member defining a bearing surface.

22. The mooring assembly of claim 1, wherein: The rotatably mounted vessel attachment point includes an attachment member for releasably receiving a vessel anchor line or cable.

23. The mooring assembly of claim 19, wherein: The fixing material package is mortar, glue or concrete.

24. The mooring assembly of claim 1, wherein: The mooring assembly is mounted to the subsea well, and the subsea well further comprises a flow controller, and wherein the rotatably mounted vessel attachment point is adapted to rotate independently of the flow controller.

25. A method of installing a mooring assembly of a vessel to a subsea well, the subsea well comprising a well guide, the method comprising the following steps: (a) providing a mooring assembly as described including a base and a vessel attachment point; and (b) rotatably mounting and securing the mooring assembly to the well conductor at or near the seabed surface; Wherein, in use, a vessel moored to the subsea well is capable of performing a rotational movement around the subsea well.

26. The method according to claim 25, wherein: Securing the mooring assembly to the well conduit includes applying a securing material.

27. The method according to claim 26, wherein: The fixing material is applied so that it extends below the sea floor and / or the fixing material is concrete or cement.

28. The method of claim 25, further comprising fitting a flow controller to the subsea well, and wherein: The mooring assembly and the flow controller are capable of rotating independently of each other.

29. A method for mooring a vessel to a subsea well, the method comprising the step of attaching the vessel to the subsea well by means of the mooring assembly of claim 1, wherein: When moored, the vessel is able to perform a rotational movement around the subsea well.

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