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Title:
A METHOD FOR OPERATING A VESSEL AND A FLOATING WIND TURBINE AND A COMBINATION OF VESSEL AND FLOATING WIND TURBINE
Document Type and Number:
WIPO Patent Application WO/2021/078748
Kind Code:
A1
Abstract:
A method for operating a vessel for offshore operations and a floating wind turbine for providing power from the wind to the vessel, wherein the method comprises the following steps: a. sailing the vessel and floating wind turbine to an offshore site where operations need to be carried out by the vessel; b. providing a plurality of anchors in a sea bottom; c. mooring the vessel to the plurality of anchors; and d. mooring the floating wind turbine to the plurality of anchors such that the vessel and the floating wind turbine share at least one of the plurality of anchors.

Inventors:
WIJNING, Diederick Bernardus (Admiraal Trompstraat, 3115 HH SCHIEDAM, NL)
ROODENBURG, David (Admiraal Trompstraat, 3115 HH SCHIEDAM, NL)
Application Number:
EP2020/079515
Publication Date:
April 29, 2021
Filing Date:
October 20, 2020
Export Citation:
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Assignee:
ITREC B.V. (3115 HH SCHIEDAM, 3115 HH SCHIEDAM, NL)
International Classes:
B63B35/44; B63B21/50
Attorney, Agent or Firm:
EP&C (2280 GE Rijswijk, NL)
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Claims:
C L A I M S

1. A method for operating a vessel for offshore operations and a floating wind turbine for providing power from the wind to the vessel, wherein the method comprises the following steps: a. sailing the vessel and floating wind turbine to an offshore site where operations need to be carried out by the vessel; b. providing a plurality of anchors in a sea bottom; c. mooring the vessel to the plurality of anchors; and d. mooring the floating wind turbine to the plurality of anchors such that the vessel and the floating wind turbine share at least one of the plurality of anchors.

2. A method according to claim 1 , wherein the vessel is a vessel for performing wellbore-related activities.

3. A method according to claim 1 or 2, wherein the vessel is a semisubmersible vessel.

4. A method according to any one or more of the preceding claims, wherein the floating wind turbine and the vessel share at least two of the plurality of anchors.

5. A method according to any one or more of the preceding claims, wherein the floating wind turbine is a first floating wind turbine, and wherein a second floating wind turbine is provided that is moored to the plurality of anchors such that the vessel and the second floating wind turbine share at least one of the plurality of anchors.

6. A method according to any one or more of the preceding claims, wherein providing a plurality of anchors in a sea bottom includes providing a first set of anchors and a second set of anchors, wherein the offshore site is a first offshore site, wherein in step c. and d. the floating wind turbine and the vessel are moored to the first set of anchors, and wherein the method further comprises the steps of: e. sailing the vessel to a second offshore site; and f. mooring the vessel to the second set of anchors and one or more anchors of the first set of anchors.

7. A method according to claim 6, wherein in step f. the vessel and the floating wind turbine are moored to the second set of anchors and one or more anchors of the first set of anchors, wherein the vessel and the floating wind turbine share at least one anchor.

8. A method according to claim 6, wherein the floating wind turbine is a first floating wind turbine, and wherein a second floating wind turbine is moored to the second set of anchors, and wherein the vessel after step f. shares at least one anchor with the second floating wind turbine.

9. A method according to claim 8, wherein the first floating wind turbine, the second floating wind turbine, and the vessel all share an anchor after step d. and/or after step f.

10. In combination a vessel for offshore operations and a floating wind turbine for providing power from the wind to the vessel including a plurality of anchors, wherein the vessel and the floating wind turbine are moored to the plurality of anchors such that the vessel and the floating wind turbine share at least one of the plurality of anchors.

11. The combination according to claim 10, wherein the vessel is a vessel for performing wellbore-related activities.

12. The combination according to claim 10 or 11, wherein the vessel is a semisubmersible vessel.

13. The combination according to any one or more of the claims 10-12, wherein the floating wind turbine and the vessel share at least two of the plurality of anchors.

14. The combination according to any one or more of the claims 10-13, wherein the floating wind turbine is a first floating wind turbine, and the second floating wind turbine is moored to the plurality of anchors such that the vessel and the second floating wind turbine share at least one of the plurality of anchors.

15. The combination according to claim 14, wherein the first floating wind turbine, the second floating wind turbine, and the vessel all share an anchor.

16. The combination according to claim 14, wherein the first floating wind turbine and the second floating wind turbine are arranged at opposite sides of the vessel.

17. The combination according to any one or more of the claims 10-16, wherein the anchors are suction anchors.

Description:
A METHOD FOR OPERATING A VESSEL AND A FLOATING WIND TURBINE AND A COMBINATION OF VESSEL AND FLOATING WIND TURBINE

The invention relates to a vessel, e.g. a vessel for performing subsea wellbore related activities, such as workover activities, well maintenance, installing an object on a subsea wellbore, drilling a subsea wellbore, oil production via the wellbore, etc.

During performing of the subsea wellbore related activities, the vessel preferably maintains its position. Depending on the depth of the sea at the wellbore, maintaining the position can be done in various ways including but not limited to active positioning of the vessel using the vessel engines, jack-up systems and anchoring systems. However, a drawback is that an oil field generally comprises a lot of distinct wellbores so that the position of the vessel regularly changes within the oil field. For jack-up systems and anchoring systems this requires a lot of time to adjust the position while the active positioning systems require a large energy consumption. An anchoring system has the additional drawback that a lot of wellbores require a lot of anchors to be placed on the sea bottom having a negative influence on sea life and requiring a lot of installation time.

Another issue related to performing subsea wellbore related activities is that the activities require a lot of energy. Normally this energy is provided by the vessel itself for instance provided by generators using fuel stored on board of the vessel. However, when fuel runs low, new fuel needs to be transported to the vessel. Other solutions may include the provision of power lines between an onshore or offshore wind turbine farm. However, such long power lines are also not desired, especially when the position regularly changes.

It is therefore an object of the invention to provide a vessel that is able to operate independently for a longer period of time and/or is able to maintain or change position at wellbores more efficiently.

This object is achieved by providing a method for operating a vessel for offshore operations and a floating wind turbine for providing power from the wind to the vessel, wherein the method comprises the following steps: a. sailing the vessel and floating wind turbine to an offshore site where operations need to be carried out by the vessel; b. providing a plurality of anchors in a sea bottom; c. mooring the vessel to the plurality of anchors; and d. mooring the floating wind turbine to the plurality of anchors such that the vessel and the floating wind turbine share at least one of the plurality of anchors.

The use of a floating wind turbine provides a power source near the vessel so that the vessel is able to operate independently for a longer period of time, which floating wind turbine is able to follow any position change of the vessel easily. By sharing anchors, the number of anchors to be used can be reduced which results in a reduction of installation time, It also allows to handle the corresponding two mooring lines between the shared anchor and the vessel and floating wind turbine more efficiently.

In an embodiment, the vessel is a vessel for performing wellbore-related activities, such as workover activities, well maintenance, installing an object on a subsea wellbore, drilling a subsea wellbore, oil production via the wellbore, etc.

In an embodiment, the vessel is a semisubmersible vessel.

In an embodiment, the floating wind turbine and the vessel share at least two of the plurality of anchors. The floating wind turbine is preferably moored to at least three anchors so that the position can efficiently be maintained in all directions. The vessel is preferably moored to at least three, more preferably at least four, most preferably at least six, for instance eight anchors.

In an embodiment, the floating wind turbine is a first floating wind turbine, wherein a second floating wind turbine is provided that is moored to the plurality of anchors such that the vessel and the second floating wind turbine share at least one of the plurality of anchors.

In an embodiment, providing a plurality of anchors in a sea bottom includes providing a first set of anchors and a second set of anchors, wherein the offshore site is a first offshore site, wherein in step c. and d. the floating wind turbine and the vessel are moored to the first set of anchors, and wherein the method further comprises the steps of: e. sailing the vessel to a second offshore site; and f. mooring the vessel to the second set of anchors and one or more anchors of the first set of anchors. In an embodiment, in step f., the vessel and the floating wind turbine are moored to the second set of anchors and one or more anchors of the first set of anchors, wherein the vessel and the floating wind turbine share at least one anchor.

In an embodiment, the floating wind turbine is a first floating wind turbine, and wherein a second floating wind turbine is moored to the second set of anchors, wherein the vessel after step f. shares at least one anchor with the second floating wind turbine.

In an embodiment, the first floating wind turbine, the second floating wind turbine, and the vessel all share an anchor after step d. and/or after step f.

The invention further relates to in combination a vessel for offshore operations and a floating wind turbine for providing power from the wind to the vessel including a plurality of anchors, wherein the vessel and the floating wind turbine are moored to the plurality of anchors such that the vessel and the floating wind turbine share at least one of the plurality of anchors.

In an embodiment, the vessel is a vessel for performing wellbore-related activities, such as workover activities, well maintenance, installing an object on a subsea wellbore, drilling a subsea wellbore, oil production via the wellbore, etc.

In an embodiment, wherein the vessel is a semisubmersible vessel.

In an embodiment, the floating wind turbine and the vessel share at least two of the plurality of anchors.

In an embodiment, the floating wind turbine is a first floating wind turbine, and the second floating wind turbine is moored to the plurality of anchors such that the vessel and the second floating wind turbine share at least one of the plurality of anchor.

In an embodiment, the first floating wind turbine, the second floating wind turbine and the vessel all share an anchor.

In an embodiment, the first floating wind turbine and the second floating wind turbine are arranged at opposite sides of the vessel.

In an embodiment, the anchors are suction anchors. The invention will now be described in a non-limiting way by reference to the accompanying drawings in which like parts are indicated using like reference symbols, and in which:

Fig. 1 schematically depicts a side view of a combination of a vessel for offshore operations and two floating wind turbines according to an embodiment of the invention;

Fig. 2 schematically depicts a plan view of the combination of Fig. 1 ;

Fig. 3A schematically depicts an oil field with two wellbores and the positioning of a vessel over one wellbore in accordance with a first arrangement;

Fig. 3B schematically depicts the oil field of Fig. 3A with the vessel being positioned over the other wellbore in accordance with a second arrangement;

Fig. 4A schematically depicts an oil field with two wellbores and the positioning of a vessel over one wellbore in accordance with a third arrangement; and Fig. 4B schematically depicts the oil field of Fig. 4A with the vessel being positioned over the other wellbore in accordance with a fourth arrangement.

Figs. 1 and 2 schematically depict a combination of a vessel V for offshore operations, a first floating wind turbine FW1, and a second floating wind turbine FW2. The vessel V and wind turbines FW1, FW2 are located offshore at a site where the sea bottom SB is at a depth D. Fig. 1 depicts a side view while Fig. 2 depicts a plan view.

The vessel V may be a semisubmersible vessel configured to perform wellbore-related activities, such as workover activities, well maintenance, installing an object on a subsea wellbore, drilling a subsea wellbore, oil production via a wellbore, etc. The vessel V is therefore positioned over a wellbore WB.

The first and second floating wind turbine FW1, FW2 are provided near the vessel V to provide power from the wind to the vessel V. The fact that the wind turbines are floating makes it easy to change the position of the wind turbines and adapt the position to the position of the vessel V. It is for instance possible that the first and second wind turbines FW1, FW2 follow the vessel during wellbore-related activities within a field of multiple wellbores. Another advantage of the floating wind turbines FW1, FW2 is that they can be used independent of the water depth D.

To provide power to the vessel V, each wind turbine FW1, FW2 has an associated power line PL, preferably provided slack on the sea bottom SB to prevent any overload of the power lines PL due to relative motions between the wind turbines and the vessel. Although only two floating wind turbines FW1, FW2 are depicted in Figs. 1 and 2, it will be apparent to the skilled person that only one wind turbine or any other number of wind turbines may be provided as well.

In order to maintain the position of the vessel V and the first and second floating wind turbines FW1, FW2, a plurality of anchors is provided in the sea bottom SB. In this example, a total of ten anchors are provided. Anchors that are only connected to the vessel V by a mooring line ML are indicated using reference symbol AV. Anchors that are only connected to a wind turbine FW1, FW2 by a mooring line ML are indicated using reference symbol AW. Anchors that are connected to both the vessel V and a wind turbine FW1, FW2 by a mooring line MO and thus shared by the vessel V and wind turbine FW1, FW2 are indicated using reference symbol AVW.

When sharing of anchors as according to the invention was not applied, a total number of fourteen anchors should have been provided to achieve the same functionality of maintaining the position of the vessel and the wind turbines FW1, FW2. The anchors AV, AW, AVW may be of the suction type allowing to lower the anchors to the sea bottom SB, pumping water out of the anchors to apply negative pressure inside the anchor resulting in the anchor being sucked into the sea bottom SB. This installation process is time-consuming and has a negative influence on sea life near or in the sea bottom SB. Reducing the number of anchors required for achieving the same result thus has a huge advantage.

As can be seen in the figures, the first and second wind turbines FW1, FW2 are arranged at opposite sides of the vessel V. Although not necessary per se, the symmetrical arrangement has the advantage that loads applied to the anchors are also more or less symmetrical and may compensate each other.

Wind and current may apply loads to the vessel V and the wind turbines FW1, FW2 urging them in a certain direction. An example of such a direction is indicated in Fig. 1 as arrow UD.

Urging the first wind turbine FW1 in the direction UD towards the vessel V will increase the tension in the mooring line ML connected to the first wind turbine FW1, but will simultaneously decrease the tension in the mooring lines MO connected to the first wind turbine FW1.

Urging the second wind turbine FW2 in the direction UD away from the vessel V will decrease the tension in the mooring line ML connected to the second wind turbine FW2, but will simultaneously increase the tension in the mooring lines MO connected to the second wind turbine FW2.

Urging the vessel V in a direction UD towards the second wind turbine FW2 will increase the tension in the mooring lines MO connected to vessel V and extending towards the first wind turbine FW1, but will simultaneously decrease the tension in the mooring lines MO connected to the vessel V and extending towards the second wind turbine FW2. As a result thereof, the loads applied to the anchors AVW will not significantly increase due to sharing of the anchors.

Fig. 3A schematically depicts a plan view of an oil field with two wellbores WB, WB2 at a certain distance from each other. Around the wellbore WB, a first set of anchors is installed in a pattern similar to the pattern of anchors shown in Figs. 1 and 2. The anchors belonging to the first set of anchors all have reference symbols starting with the letter “A” and ending with the numeral “1”. The vessel V, the first floating wind turbine FW1 and the second floating wind turbine FW2 similar to the embodiment of Figs. 1 and 2 have been schematically indicated in Fig. 3A.

Anchors connected to the vessel include the letter “V” in their reference symbol while anchors connected to a wind turbine include the letter “W’ in their reference symbol. Mooring lines connected to a shared anchor AVW1 are indicated using reference symbol MO while mooring lines connected to a non-shared anchor AV1 or AW1 are indicated using reference symbol ML.

Fig. 3A also depicts a second set of anchors installed around the second wellbore WB2 in a pattern similar to the pattern of the first set of anchors, although this pattern is not complete as will be explained below in more detail. The anchors belonging to the second set of anchors all have reference symbols starting with the letter “A” and ending with the numeral “2”.

Preferably, all anchors, i.e. the anchors of the first set of anchors and the anchors of the second set of anchors are installed prior to performing any operations with the vessel V. However, it is also possible that the first set of anchors is installed first, the vessel V and the wind turbines FW1, FW2 are connected to the first set of anchors as shown in Fig. 3A and subsequently while the vessel V is performing operations, the second set of anchors is installed.

When the second set of anchors is installed, the vessel can be moved to the second wellbore WB2 by disconnecting from the anchors of the first set of anchors, sailing towards the second wellbore WB2 and connecting the vessel and wind turbines to the second set of anchors and the first set of anchors as depicted in Fig. 3B.

The way the vessel and the wind turbines are connected to the anchors in Fig. 3A will be referred to as the first arrangement while the way the vessel and the wind turbines are connected to the anchors in Fig. 3B will be referred to as the second arrangement. To clearly show which anchors are used in which arrangement, anchors used in the first arrangement are square, anchors used in the second arrangement are circular and anchors used in both the first and second arrangement are square with an inscribed circle. The anchors used in both the first and second arrangement are the anchors AVW1 of the first set of anchors. This may also be referred to as sharing of anchors in the first and second arrangement and results in less anchors needed when going through an oil field.

Although the example of Figs. 3A and 3B relates to two wellbores only, it will be apparent to the skilled person that the same principle can be used with more wellbores as well.

Fig. 4A schematically depicts a plan view of an oil filed with two wellbores WB, WB2 at a certain distance from each other. Around the wellbore WB, a first set of anchors is installed in a pattern similar to the pattern of anchors shown in Figs. 1 and 2. The anchors belonging to the first set of anchors all have reference symbols starting with the letter “A” and ending with the numeral “1”. The vessel V, the first floating wind turbine FW1 and the second floating wind turbine FW2 similar to the embodiment of Figs. 1 and 2 have been schematically indicated in Fig. 4A.

Anchors connected to the vessel include the letter “V” in their reference symbol while anchors connected to a wind turbine include the letter “W’ in their reference symbol. Mooring lines connected to a shared anchor AVW1 are indicated using reference symbol MO while mooring lines connected to a non-shared anchor AV1 or AW1 are indicated using reference symbol ML.

Fig. 4A also depicts a second set of anchors installed around the second wellbore WB2 in a pattern similar to the pattern of the first set of anchors, although this pattern is not complete as will be explained below in more detail. The anchors belonging to the second set of anchors all have reference symbols starting with the letter “A” and ending with the numeral “2”.

When the second set of anchors is installed, the vessel can be moved to the second wellbore WB2 by disconnecting from the anchors of the first set of anchors, sailing towards the second wellbore WB2 and connecting the vessel to the second set of anchors and the first set of anchors as depicted in Fig. 4B.

The way the vessel and the wind turbines are connected to the anchors in Fig. 4A will be referred to as the third arrangement while the way the vessel and the wind turbines are connected to the anchors in Fig. 4B will be referred to as the fourth arrangement. To clearly show which anchors are used in which arrangement, anchors used in the third arrangement are square, anchors used in the fourth arrangement are circular and anchors used in both the third and fourth arrangement are square with an inscribed circle. To be consistent with the symbols used and their meaning throughout the description it is explicitly mentioned here that the anchor AVW1 in Fig. 4A shared by the vessel V and the first wind turbine FW1 and not the second wind turbine FW2 is indicated as anchor AW1 in Fig. 4B as it is no longer connected to the vessel V. The opposite happened to anchor AW1 in Fig. 4A that in Fig. 4B is connected to the vessel V and thus renamed to be an anchor AVW1. The corresponding mooring lines MO and ML have also switched.

It will be apparent that in this example, moving the vessel from wellbore WB to the second wellbore WB2 only required five new anchors, while all others could be reused.

Further, there is an anchor AVW1 connected to both the first wind turbine FW1 and the second wind turbine FW2 as well as the vessel V. Another advantage of this example is that while the vessel was repositioned, the first and second wind turbine could maintain their position.