Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
ARRANGEMENT FOR SECURING A FLOATING WIND TURBINE IN A SEABED, AND USE OF A SUBSEA WELL PORTION FOR SECURING THE FLOATING WIND TURBINE IN THE SEABED
Document Type and Number:
WIPO Patent Application WO/2022/149982
Kind Code:
A1
Abstract:
Arrangement for securing a floating wind turbine (1) in at least one fastening (2a, 2b) arranged on or under a seabed (32), wherein respective end portions of at least one elongated fastening means (14, 15) are fastened in a wind turbine hull (11) and the at least one fastening (2a, 2b) arranged on or under the seabed (32) and is a well portion which forms or has formed part of a subsea well for exploration and/or extraction of hydrocarbons or other fluids from a subterranean formation or for injecting fluid into the subterranean formation, wherein the arrangement for securing the floating wind turbine (1) in the at least one fastening (2a, 2b) is a tension leg arrangement. Use of a subsea well portion (2a, 2b) and a tension leg arrangement as a fastening for a floating wind turbine (1).

Inventors:
HAUGLAND TROND (NO)
Application Number:
PCT/NO2021/050263
Publication Date:
July 14, 2022
Filing Date:
December 15, 2021
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
NOROCEAN AS (NO)
International Classes:
B63B21/50; B63B35/44; E02B3/24; F03D13/25
Domestic Patent References:
WO2009040442A12009-04-02
WO2011112561A22011-09-15
Foreign References:
FR2818327A12002-06-21
GB2486911A2012-07-04
Attorney, Agent or Firm:
HÅMSØ PATENTBYRÅ AS (NO)
Download PDF:
Claims:
C l a i m s

1. Arrangement for securing a floating wind turbine (1) in at least one fastening (2a, 2b) arranged on or under a seabed (32), wherein respective end portions of at least one elongated fastening means (14, 15) are fastened in a wind turbine hull (11) and in the at least one fastening (2a, 2b) arranged on or under the seabed (32), wherein the at least one fastening (2a, 2b) is a subsea well portion, c h a r a c t e r i z e d i n that the arrangement for securing the floating wind turbine (1) in the at least one fastening (2a, 2b) is a tension leg arrange ment.

2. The arrangement according to claim 1, wherein the at least one elongated fas tening means is a fastening line (14).

3. The arrangement according to claim 1, wherein the at least one elongated fas tening means is a substantially torsionally rigid fastening stay (15).

4. The arrangement according to claim 3, wherein the fastening stay (15) in each of its end portions is provided with a joint (151) which allows the direction of the longitudinal axis of the fastening stay (15) to deviate from the directions of the longitudinal axes of the wind turbine hull (11) and the well portion without the wind turbine hull (11) rotating about its own longitudinal axis.

5. The arrangement according to any of the preceding claims, wherein the at least one elongated fastening means (14, 15) is fastened directly in a wellhead (2a).

6. The arrangement according to any of the claims 1 - 4, wherein the at least one elongated fastening means (14, 15) is fastened in a fastening frame (21, 21a) connected to a wellhead (2a).

7. The arrangement according to any of the claims 1 - 4, wherein the at least one elongated fastening means (14, 15) is fastened in a structure (2b) extending downwards from the seabed (32) under a wellhead (2a).

8. The arrangement according to any of the claims 1 - 4, wherein the at least one elongated fastening means (14, 15) is fastened in a lined or unlined portion (2b) of a borehole extending downwards in a rock structure (2c) under a wellhead (2a).

9. The arrangement according to any of the preceding claims, wherein the at least one elongated fastening means (14, 15) is provided with a damping device (16) arranged to take up a vertical load component applied to the at least one elon gated fastening means (14, 15) by a heave movement of the floating wind tur bine (1).

10. The arrangement according to any of the preceding claims, wherein the floating wind turbine (1) is fastened in an assembly of several wellheads (2a) arranged at a distance from each other on the seabed (32).

11. Use of a subsea well portion (2a, 2b) and a tension leg arrangement as specified in any of the claims 1-10 as a fastening for a floating wind turbine (1).

Description:
Arrangement for securing a floating wind turbine in a seabed, and use of a subsea well portion for securing the floating wind turbine in the seabed

This invention relates to an arrangement for securing a floating wind turbine in at least one fastening arranged on a seabed, wherein respective end portions of at least one elongated fastening means are fastened in a wind turbine hull and in the at least one fastening arranged on the seabed. The invention also relates to the use of a well por tion which forms or has formed part of a subsea well, as a fastening on a seabed for a floating wind turbine. The subsea well may be established for various purposes, typi cally for the exploration and/or extraction of hydrocarbons or other fluids from a sub- terranean formation or for injecting fluid into the subterranean formation.

Securing a floating wind turbine in the seabed requires establishing a comprehensive and expensive anchor system which by its weight and/or securing in the seabed masses is able to hold the floating wind turbine in position regardless of the forces which changing tides, wind, and water currents apply to the wind turbine. Typically, floating wind turbines are fastened to the seabed via stays or anchor lines or combina tions of stays and anchor lines to suction anchors that are set down in loose soils that make up the seabed under the wind turbine.

FR2818327 A1 describes a maritime wind turbine fastened to a structure projecting upwards from a floating buoy. The buoy is connected to a vertical elongated pipe which is secured to an anchor on the seabed and projects up through the buoy. The buoy can rotate and move vertically relative to the pipe. Tensioning means which are arranged on the buoy and fastened to the pipe, hold the pipe vertically and extended, so that an upper end of the pipe is kept above the water. The tensioning means are typically cables that are kept in tension by means of springs. Moreover, one or more buoyancy bodies may be fastened to the pipe.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow.

Subsea wells for hydrocarbon extraction are usually provided with a wellhead arranged on the seabed and provided with sturdy fastenings in the masses under the seabed, partly to carry the weight of valves that form a central part of the wellhead, partly to take up the load from the riser or umbilical which connects the wellhead to a surface installation, and possibly to be able to withstand a reservoir pressure propagated through well pipes from an underlying production reservoir to the wellhead.

It is an object of the present invention to provide an arrangement for securing a float ing wind turbine in a seabed using one or more wellheads or the underlying structure as a fastening point in or under the seabed for stays or fastening line(s) extending downwards from the hull of a floating wind turbine. The hull of the wind turbine, which by its positive buoyancy floats in the body of water, may have any shape. It is particu larly advantageous to use wellheads of wells which are abandoned and plugged, in that potential conflicts of interest between safety during production from the well and the requirements to the anchoring system for the wind turbine, are then avoided. The arrangement is preferably provided as a tension leg arrangement, i.e. an arrangement where the hull of the wind turbine is ballasted before it is fastened in the seabed, and that at least parts of the ballast are then removed so that said stay or fastening line(s) remain with tensile load, and the hull of the wind turbine is kept at an even distance from the seabed without vertical movement provided by tides, waves, etc.

Inasmuch as the costs related to establishing the wellhead have already been taken, the installation costs for the wind turbine can be considerably reduced.

Since established fields for extraction of hydrocarbons from subsea fields already place restrictions on other activities, for example fishing, establishing wind turbines in such an area will lead to few or no further restrictions on other activities.

A further advantage of the invention is that areas with activity which comprises estab lishing wellheads suitable for securing floating wind turbines, often comprises consum ers of electric energy, and thus infrastructures for distribution of electric energy have already been established in the area, and in many cases also cable connection to nearby land areas' energy distribution network.

In addition, the use of existing well portions for securing floating wind turbines could make it easier to electrify offshore fields for production of hydrocarbons, etc. by means of wind turbines, since such securing does not necessitate establishing exten sive structures that may conflict with existing, subsea infrastructures established for production of hydrocarbons etc.

The invention is defined by the independent patent claims. The dependent claims de fine advantageous embodiments of the invention.

In a first aspect, the invention more specifically relates to an arrangement for securing a floating wind turbine in at least one fastening arranged on or under a seabed, wherein respective end portions of at least one elongated fastening means are secured in a wind turbine hull and in the at least one fastening arranged on or under the sea bed and is a subsea well portion which forms or has formed part of a subsea well, characterized in that the arrangement for securing the floating wind turbine in the at least one fastening is a tension leg arrangement.

The at least one elongated fastening means may be a fastening line. Alternatively, the at least one elongated fastening means may be a substantially torsionally rigid fas tening stay. The substantially torsionally rigid fastening stay may in each of its end portions be provided with a joint which allows the direction of the longitudinal axis of the fastening stay to deviate from the directions of the longitudinal axes of the wind turbine hull and the well portion without the wind turbine hull rotating about its own longitudinal axis. An effect of this is that different types of elongated fastening means may be used in compliance with what the design basis requires or allows.

The at least one elongated fastening means may be fastened directly in a wellhead. Alternatively, the at least one elongated fastening means may be secured in a fas tening frame connected to the wellhead. An effect of this is that the wind turbine may be secured in existing, easily accessible elements.

The floating wind turbine may be fastened in an assembly of several wellheads ar ranged at a distance from each other on the seabed. An effect of this is that sufficient stability can be achieved even when the ability of the wellheads to take up loads indi vidually is too small to withstand the load from the wind turbine.

The at least one elongated fastening means may be fastened in a structure extending downwards from the seabed under a wellhead. Alternatively, the at least one elongat ed fastening means may be fastened in a lined or unlined portion of a borehole ex tending downwards in a rock structure under a wellhead. An effect of this is that suffi cient stability can be achieved even when the ability of the wellhead itself to take up load is too small to withstand the load from the wind turbine. The at least one elongated fastening means may be provided with a damping device arranged to take up a vertical load component applied to the at least one elongated fastening means by a heave movement of the floating wind turbine. An effect of this is that the stresses of waves etc. both on the wind turbine and on the arrangement for fastening the wind turbine, are reduced.

In a second aspect, the invention more specifically relates to the use of a subsea well portion and a tension leg arrangement according to the first aspect of the invention as a fastening for a floating wind turbine.

In the following are described examples of preferred embodiments illustrated in the accompanying drawings, wherein:

Fig. 1 shows in a lateral view a principle drawing of a wind turbine with a hull floating in a body of water, secured in a wellhead in a seabed by means of two fastening lines;

Fig. 2 shows correspondingly to figure 1, where the hull of the wind turbine is fastened to the wellhead with several parallel fastening lines;

Fig. 3 shows correspondingly to figure 1, where the hull of the wind turbine is fastened to the wellhead with a rotationally rigid stay connected to the bottom of the hull of the wind turbine and to the wellhead by means of universal joints; Fig. 4 shows correspondingly to figure 1, where the hull of the wind turbine is fastened to several wellheads, a fastening line extending from a respec tive wellhead and up to a fastening on the lateral face of the wind tur bine; and

Fig. 5 shows correspondingly to figure 1, where a stay is fastened to a struc ture extending down under the wellhead.

In the drawings, reference numeral 1 denotes a wind turbine comprising a wind tur bine hull 11 in which, from a buoyancy body 111 which is floatable in a body of water 3, a tower 112 projects up above a water surface 31. At the upper end of the tower 112 there is in a manner known per se arranged a turbine casing 12 with a turbine rotor 13 provided with several rotor blades 131.

The wind turbine 1 floats in the body of water 3 at a distance above a seabed 32 where at least one fastening in the form of a wellhead 2a is arranged, which with its shape and size is suitable for absorbing both horizontal and vertical forces, the well head 2a forming part of a production or exploration well 2 for hydrocarbons or other fluids flowing up from a reservoir in a subterranean formation (not shown), possibly a well for injecting fluid into the subterranean formation, or the wellhead 2a is left on the seabed 32 after said well 2 is abandoned and closed by plugging. In the figures, the wellhead(s) 2a is/are shown schematically projecting downwards in a seabed mass 4 under the seabed 32.

Reference is then made to figure 1, where the wind turbine 1 is fastened to one well head 2a by means of several elongated fastening means in the form of fastening lines 14 (two shown) extending between the wind turbine hull 11, in this exemplary embod iment the lower edge of the buoyancy body 111, and the wellhead 2a.

Reference is then made to the exemplary embodiment in figure 2, where several fas tening lines 14 extend parallel to each other between the wind turbine hull 11 and the single wellhead 2a.

In the exemplary embodiment according to figure 3, the wind turbine hull 11 is fas tened to the single wellhead 2a by means of an elongated fastening means in the form of a substantially torsionally rigid fastening stay 15. The fastening stay 15 is in both its end portions provided with joints 151 which allow the direction of the longitudinal axis of the fastening stay 15 to deviate from the directions of the longitudinal axes of the wind turbine hull 11 and the wellhead 2a without the wind turbine hull 11 being able to rotate about its own longitudinal axis, typically in that the joints 151 are formed as universal joints or similar joint types suitable for transferring torque about the longitudinal axes of the interconnected elements 11, 15; 15, 2a.

Reference is then made to figure 4, which shows an exemplary embodiment in which the wind turbine 1 is fastened to several wellheads 2a with one or more fastening lines

14 (one shown) extending between each of the wellheads 2a and the wind turbine hull 11.

Figure 5 shows an exemplary embodiment in which the elongated fastening means 14,

15 is secured down in a structure 2b extending downwards from the seabed 32 under the wellhead 2a, for example in a lined or unlined portion of a borehole extending downwards in the subsoil, preferably downwards in a rock structure 2c under the loose soil 4 which usually forms the seabed 32.

The securing of the fastening lines 14 / fastening stay 15 in the wellhead 2a may be done directly in existing elements on the wellhead 2a, as shown in principle in figures 1 and 4, or they may be fastened to elements which are provided specifically for the purpose and connected to the wellhead 2a, in figure 2 exemplified as a line fastening frame 21, and in figure 3 as a stay fastening frame 21a. Similarly, the fastening lines 14 / fastening stay 15 may be fastened directly in the wind turbine hull 11, as shown in principle in figures 1 and 3, or they/it may be fastened to elements which are pro vided specifically for the purpose and connected to the wind turbine hull 11, in figures

2 and 4 exemplified as line fastenings 111a, here arranged on the lower end of the buoyancy body 111, respectively on the periphery of the buoyancy body 111 about midway between the upper and lower ends of the buoyancy body 111.

It is within the scope of the invention to combine one or more of the principles of the various exemplary embodiments for fastening the floating wind turbine 1 in the sea bed 32.

The wind turbine 1 is formed as a tension leg arrangement, i.e. an arrangement where the wind turbine hull 11 is supplied with a ballast 111b before the wind turbine hull 11 is fastened in the wellhead 2a or the underlying structure 2b, and that at least parts of the ballast 111b are then removed, so that said fastening line(s) 14 or stay 15 is ten sile loaded and the wind turbine hull 11 is kept at an even distance from the seabed 32 without vertical movement provided by tides, waves, etc.

The tension leg arrangement may possibly be provided with one or more damping de vices 16 arranged in connection with said fastening line(s) 14 or stay 15, in figure 5 shown schematically arranged between the wind turbine hull 11 and the stay 15. Said damping device(s) 16 are arranged to take up a vertical load component applied to the attached fastening line(s) 14 or stay 15 when heave movements due to waves, etc. is applied to the floating wind turbine 1.

Use of the verb "comprise" and its conjugations does not exclude the presence of ele ments or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.