WO2014060741A2

WO2014060741A2 - Improvements in or relating to marine operations

Info

Publication number: WO2014060741A2
Application number: PCT/GB2013/052688
Authority: WO
Inventors: Richard Parkinson
Original assignee: Mojo Maritime Limited
Priority date: 2012-10-16
Filing date: 2013-10-15
Publication date: 2014-04-24
Also published as: EP2909126A2; WO2014060741A3; GB201218569D0

Abstract

This invention relates to marine operations for the purposes of installing, maintaining and decommissioning sub-sea structures, such as those used in tidal, wave and wind energy converters. This applies to all phases of an offshore energy demonstrator or array life cycle, which covers: • Seabed preparation (sub-sea drilling, installing piles); • Foundation installation; • Cable installation; • Power converter installation (tidal/wind turbine or wave energy converter); • Operations and maintenance (during normal operation, including repairs and maintenance); and • Decommissioning.

Description

IMPROVEMENTS IN OR RELATING TO MARINE OPERATIONS

This invention relates to marine operations for the purposes of installing, maintaining and decommissioning sub-sea structures, such as those used in tidal, wave and wind energy converters. This applies to all phases of an offshore energy demonstrator or array life cycle, which covers:

• Seabed preparation (sub-sea drilling, installing piles);

• Foundation installation;

• Cable installation;

• Power converter installation (tidal/wind turbine or wave energy converter); · Operations and maintenance (during normal operation, including repairs and maintenance); and

• Decommissioning.

According to a first aspect of the present invention, there is provided apparatus for a marine operation comprising a support structure for supporting an object by way of a support coupling and a stabilising arrangement including a stabilising coupling connectable to the object.

According to a second aspect of the present invention, there is provided a method of deploying an object from a marine vessel comprising attaching a support coupling to the object, attaching a stabilising coupling to the object and moving the object through a column of water.

Owing to these aspects, the object can be lowered accurately to a desired position on a seabed location.

Preferably, the support coupling is in the form of a cable and the stabilising coupling is also preferably a cable. Advantageously, the object is a payload of the marine vessel and can be in the form of any object to be lowered to the sea bed in the course of a marine operation. According to a third aspect of the present invention, there is provided a marine vessel comprising a cable dispensing device including a cable to be deployed into water and a cable guiding device attached to a lateral edge region of the vessel for guiding the cable from the lateral edge of the vessel.

According to a fourth aspect of the present invention, there is provided a method of deploying a cable from a marine vessel into water comprising dispensing a cable and guiding the cable into the water from a lateral edge of the vessel. Owing to these aspects, a marine cable-laying operation can be completed with a good routing accuracy.

Advantageously, the cable is a sub-sea power and/or communications cable. Advantageously, a cable touch-down monitoring device is used to assist in the tracking of the cable as it is laid upon the seabed.

According to a fifth aspect of the present invention, there is provided a marine vessel comprising a plurality of hulls connected by a deck surface having an opening therein between respective hulls and a tool arrangement for working at a sub-marine surface arranged to be manoeuvred into a column of water through the opening.

According to a sixth aspect of the present invention, there is provided a method of working at a sub-marine surface comprising manoeuvring a sub-marine tool arrangement through a deck opening of a vessel having a plurality of hulls, the opening being between respective hulls and lowering the sub-marine tool to the submarine surface.

Owing to these aspects, sub-marine operations at a sea bed surface can be performed from the deck of a marine vessel through a deck opening between respective hulls so as to better position the tool arrangement.

Preferably the tool arrangement is for performing drilling work into the sea bed surface or, alternatively, for mining work at the sea bed surface. A preferred marine vessel for performing a range of marine operations is a dynamic positioning vessel with a plurality of hulls and, advantageously, two hulls connected by a deck structure. Such a vessel is described in our earlier British Patent Application 1200841 .3.

In order that the present invention can be clearly and completely disclosed, reference will now be made, by way of example, to the accompanying drawings, in which:-

Figure 1 is a top plan view of a marine vessel for performing a marine operation, Figure 2 is a partial cross-section of the vessel of Figure l and a column of water in the initial stage of the marine operation,

Figure 3 is a view similar to Figure 2, but at a subsequent stage of the operation, Figure 4 is a view similar to Figure 3, but at a further subsequent stage of the operation,

Figure 5 is a view similar to Figure 4, but at the next stage of the operation,

Figure 6 depicts the following stage of the operation from Figure 5,

Figure 7 shows an alternative to the stage of the operation shown in Figure 6, Figure 8 depicts the following stage of the operation following Figure 6 or 7,

Figure 9 shows the final stage of the marine operation,

Figure 10 is a view similar to Figure 1 , but for a different marine operation,

Figure 1 1 is an end elevation of the vessel of Figure 10,

Figure 12 is a view similar to Figure 10, but there being a change on the tidal flow direction,

Figures 13 and 14 are views similar to Figures 10 and 1 1 respectively, but of a second version for performing the different marine operation,

Figure 15 is s view similar to Figures 1 and 10, but for a further marine operation, Figure 16 is a side view of the vessel of Figure 15 similar to Figures 2 to 9,

Figure 17 is a view similar to Figure 16, but at a subsequent stage of the further operation,

Figure 18 is a view similar to Figure 17, but showing more detail of a sub-marine mining arrangement, and

Figure 19 is a schematic diagram of a sub-marine mining tool, vessel-mounted unit. Marine operations for installing a foundation on a seabed with one or more fixtures (i.e. a monopile, tripod or multi-legged jacket structure) generally use either a template or the foundation structure itself to correctly space the seabed fixtures. There are several stages in the installation operation of a marine energy converter device, such as a tidal or wind turbine.

Referring to Figures 1 and 2, a marine vessel 2, preferably a dynamic positioning vessel having a plurality of hulls 3 is used to perform a marine operation. The first stage of the operation is to deploy an object in the form of a single or multiple template unit 4 by way of a central moon pool/deck opening 6 or astern of the vessel 2 (as shown). The template unit 4 is moved by way of manoeuvring equipment 8 (for example an A-frame or gantry) mounted on one side of the deck opening 6 on the deck of the vessel 2 and a support coupling in the form of a cable 9 extending between the template unit 4 and the manoeuvring equipment 8. A stabilising arrangement comprises a winch drum 10 and a stabilising coupling in the form of a stabilising cable 12 extending between the winch drum 10 and the template unit 4. The winch drum 10 is mounted to the deck surface on the opposite side of the deck opening 6 to the manoeuvring equipment 8. The stabilising cable 12 is paid out over the bow section of the vessel 2 and connected to the upstream end of the sub-sea template, the direction of the flow being shown by the arrow 14. The stabilising cable 12 is used to better position the template unit 4, both in terms of latitude/longitude and heading direction by altering the tension in the stabilising cable 12 using the winch drum 10. The vessel 2 is moved across the water surface 5 by operation of a plurality of thrusters 1 1 .

This approach has the distinct advantage that the template unit 4 can be lowered into the water column before the environmental conditions are favourable, i.e. while there is still a tidal current. As a result of this primary action, the template unit 4 is already in close proximity to its intended position close to the seabed 16, so that when the tidal conditions are favourable, the time to perform the operation of lowering the template unit 4 to the seabed 16 is reduced. Therefore more similar operations can be performed in a given time, and the exposure to risk is reduced by ensuring that the operation is conducted with the maximum window of time. Figures 1 and 2 show the deployment of the template unit 4 into the 'holding' position prior to final deployment onto the seabed 16.

The benefit of operating through the central region of the dual hulled vessel 2 by way of the deck opening 6 is that wave-induced motions are at a minimum there, thereby extending the operational limits of the vessel.

From this 'holding' position, when the tidal current is within the favourable operational constraints, the template unit 4 can be deployed onto the seabed 16 at the earliest possible opportunity, as shown in Figure 3. This deployment is typically before that which could be achieved during a standard operation, as usually a payload is deployed from the deck of a vessel into the sea when the tidal current has reduced (< 1 knot). Owing to the fact that the tidal current towards the surface is greater than that at depth, the surface current could still exceed the operation's tidal limits whilst the current speed near the seabed 16 is much lower and within the operational limitations, enabling the deployment of the payload and increasing the operating windows significantly.

Upon deployment of the template unit 4 at the required position and orientation on the seabed 16, and referring to Figure 4, another object in the form of drilling unit 18 can be deployed. This drilling unit 18 engages with the template unit 4 on the sea bed 16 so that the position of the holes to be drilled, and therefore piles to be inserted in the drilled holes, are known. The drilling unit 18 has the ability to perform small corrections for seabed slope such that the piles to be inserted will interface with the following foundation structure in a subsequent stage of the operation.

The deployment of the drilling unit 18 is shown using the stabilising cable 12.

Mechanical interfaces between the template unit 4 and the drilling unit 18 require a guide cone, often referred to as a 'stabbing guide', so that they can be relatively easily initially mated.

Referring to Figures 5 and 6, on completion of a drilling stage of the operation, a drill string 20 including the drilling machinery (and shown in Figure 6) is removed from the drilling unit 18, following which a pile 22 can be installed using a drilling guide tube/conductor of the drilling unit 18, as shown in Figure 5. Once correctly inserted, and aligned if necessary, the pile 22 is then grouted into place, as shown in Figure 6. This process of drilling a hole and inserting a pile is repeated until all of the piles 22 are fixed by grouting to the seabed 16 at which time the drill string 20 can be removed and recovered to the vessel 2.

An alternative approach is to use a sub-marine or sub-sea foundation structure 24 as the template, as shown in Figure 7. Again the stabilising cable 12 is utilised to improve drill string positioning and maximising the time for the sub-sea movements.

Referring to Figure 8, following the stage of installation of the piles 22 and when having used the template unit 4, a further object in the form of the sub-sea foundation 24 can be deployed and connected to the already installed piles 22 which can form the anchor position for a variety of sub-sea structures including, but not exclusively, tidal turbines, offshore wind turbines and wave energy converters.

The foundation structure 24 is also manoeuvred into position using the stabilising cable 12, as previously explained.

Referring to Figure 9, yet another object in the form of a marine energy converter 28 (wind, tide or wave), or another sub-sea device can then be installed in a subsequent stage of the operation either directly onto the pile(s) 22, or via the foundation structure 24. In the example shown, a typical tidal turbine 28 is used which comprises a three-bladed horizontal axis turbine.

Again, this operation uses the stabilising cable 12. Advantageously, the connection point between the stabilising cable 12 and the tidal turbine 28 is made upstream of the centre of resistance, so that the payload passively assumes the desired orientation, using the directionality of the flow of water to achieve this. A lifting tool 30 provides an interface between the turbine 28 and the manoeuvring equipment 8 of the vessel 2. Marine energy converters, such as the turbine 28 and other sub-sea structures, require connections (be they electrical or otherwise) to another infrastructure, which may be shore-based or it may be another offshore structure (which itself may be submerged or above the water surface). A typical example of such a marine operation would require running a power and/or communications cable or an umbilical across a body of water which has tidal water flows. Such tidal flows can range greatly in magnitude. Where, in particular, the desired cable/umbilical route is substantially perpendicular to the tidal current, traditional cable laying over the stern of the vessel is awkward since the tidal current can relatively easily push the vessel off-course resulting in an inefficient cable route and the potential for damaged cables simply because the cable/umbilical is laid on unplanned seabed terrain.

A solution to this problem is laying the cable/umbilical over the side edge (i.e. the port or starboard edge) of the vessel 2, where the vessel 2 is substantially aligned with the direction of tidal flow and hence directionally more stable. The dynamic positioning vessel 2 can then apply the majority of its thrust to remain on track with a small amount of side force in order to lay the cable/umbilical. Referring to Figures 10 and 1 1 , an arrangement allowing better cable routing accuracy comprises a sub-sea cable/umbilical (for power and/or communications) 34, a powered and braked cable drum 36 mounted to the deck of the vessel 2 upon which the cable/umbilical is 34 wound, one or more optional cable steering devices 35 to enable safe passage of the cable/umbilical 34 across the deck to a cable engine 38 which maintains a desired tension in the cable/umbilical 34 and a cable guide device in the form of a cable guide chute 40 mounted to at least one side edge of the vessel 2. The guide chute 40 prevents damage to the cable/umbilical 34 as it passes over the side of the vessel 2. In relation to the direction of tidal flow, the direction of movement of the vessel 2 is shown by arrow 42 and the vessel thrust direction is shown by the arrow 44.

The cable engine 38 is a unit mounted on the deck that controls the tension in the cable/umbilical 34 and deploys/recovers the cable/umbilical 34 as required. The cable engine 38 includes wheels or tracks that are pressed together either side of the cable/umbilical 34 in order to control its movement.

When the tide turns (the direction of the tide changes to flow in the opposite direction) the dynamic positioning vessel 2 can easily accommodate this change to maintain the desired cable route, as seen in Figure 12.

Referring to Figures 13 and 14, in order to assist the complete tracking of the cable/umbilical to its touch down point on the seabed 16, a touch down tool 46 can be deployed along the cable/umbilical 34 (as shown by the double-headed arrow in Figure 14), and which is attached to the vessel 2 by way of a control wire 48. The cable/umbilical angle of touch down is closely monitored and, in turn, controlled by the cable engine 38 and the vessel thrust. The touch down tool 46 ensures that the cable/umbilical 34 is not bent beyond its minimum bend radius and thus prevents any likelihood of damage. The touch down tool 46 therefore allows remote monitoring of the cable laying operation and advantageously includes an imaging device, an inclinometer and possibly a sonar device operable to monitor a monitoring zone 49 covering the area where the cable/umbilical 34 touches down on the sea bed 16.

An alternative marine operation to installation of sub-sea structures is sub-sea mining. There are many different forms of sub-sea mining. Referring to Figures 15 to 19, the dual hulled dynamic positioning vessel 2 is utilisable for sub-sea mining operations through the deck opening/moonpool 6. A payload in the form of a sub-sea mining tool 50, which can either have no propulsion apparatus of its own where it is moved by movement of the vessel 2, or it can be self-propelled in which case it can traverse the seabed 16 independently of movement of the vessel 2. The choice of the sub-sea mining tool 50 would depend on the bathymetry of the mining site. The vessel 2 also houses the associated processing machinery for the sub-sea mining tool 50 in a mining unit 51 mounted to the deck of the vessel 2.

Initially, the sub-sea mining tool 50 is lowered to the seabed 16 where the mining process of seabed deposits is carried out by fluid flow scouring the sea bed 16. The sub-sea mining tool 50 may be deployed utilising the stabilising cable 12, as described above, or without if there is negligible tidal current and the positioning can be performed by the vessel 2 to a suitable accuracy. The sub-sea mining tool 50 incorporates a system to remove material at the seabed in an enclosed unit 52 to minimise the disturbance to the sea bed 16 and pump this mixture of sea water and seabed deposits up to the deck of the vessel 2 by way of a mining tool outlet umbilical 54 to a filtration unit 56 inside the mining unit 51. The separated sea water and spoil is then returned to the enclosed unit 52 by way of a mining tool inlet umbilical 58 and the separated, desired mined material 60, for example mineral deposits, is retained on the vessel 2. The mining unit 51 also comprises a sea water inlet/outlet 62 to allow for sea water priming of the pumps. After the sub-sea mining tool 50 has completed its mining operation at one site, it is then moved to the next desired site and the mining operation repeated. Thus, the ability to quickly and accurately re-position the vessel 2 and the sub-sea mining tool 50 is highly beneficial.

Claims

1 . Apparatus for a marine operation comprising a support structure for supporting an object by way of a support coupling and a stabilising arrangement including a stabilising coupling connectable to the object.

2. Apparatus according to claim 1 , wherein the support coupling is in the form of a cable.

3. Apparatus according to claim 1 or 2, wherein the object is a payload of a marine vessel to be lowered to the sea bed in the course of a marine operation.

4. Apparatus according to claim 3, wherein the object is manoeuvred by way of manoeuvring equipment mounted on one side of a deck opening and towards the rear end of the vessel.

5. Apparatus according to any preceding claim, wherein the stabilising arrangement comprises a winch drum and the stabilising coupling is in the form of a stabilising cable extending between the winch drum and the object.

6. Apparatus according to claim 5 as appended to claim 4, wherein the winch drum is mounted to the deck surface on the opposite side of the deck opening to the manoeuvring equipment.

7. Apparatus according to claim 5 or 6, wherein the stabilising cable is paid out over the bow section of the vessel and connected to an upstream end of the object.

8. Apparatus according to any one of claims 3 to 7, wherein the vessel is a dynamic positioning vessel.

9. Apparatus according to any one of claims 3 to 8, wherein the vessel comprises a cable dispensing device including a further cable to be deployed into water and a cable guiding device attached to a lateral edge region of the vessel for guiding the further cable from the lateral edge of the vessel.

10. Apparatus according to any one of claims 4 to 9, wherein the marine vessel further comprises a plurality of hulls connected by the deck surface having an opening therein between respective hulls and a tool arrangement for working at a sub-marine surface arranged to be manoeuvred into a column of water through the opening.

1 1 . A method of deploying an object from a marine vessel comprising attaching a support coupling to the object, attaching a stabilising coupling to the object and moving the object through a column of water.

12. A method according to claim 1 1 , and further comprising attaching the stabilising coupling is to an upstream end of the object.

13. A method according to claim 1 1 or 12, wherein the stabilising coupling is used to better position the object, both in terms of latitude/longitude and heading direction by altering tension in the stabilising coupling.

14. A method according to any one of claims 1 1 to 13, and further comprising, upon deployment of the object at the required position and orientation on the seabed, deploying another object.

15. A method according to claim 14, wherein the other object is a drilling unit.

16. A method according to claim 15, wherein the deployment of the drilling unit is by way of using the stabilising coupling.

17. A method according to claim 15 or 16, and further comprising, subsequent to drilling with the drilling unit, deploying a sub-sea foundation to be connected to piles inserted into drilled holes, the sub-sea foundation arranged to support energy converting devices.

18. A method according to claim 17, wherein the sub-sea foundation is manoeuvred into position using the stabilising coupling.

19. A method according to claim 17 or 18, and subsequently deploying the energy converting device.

20. A method according to claim 19, wherein the energy converting device is deployed by way of the stabilising coupling.

21 . A method according to claim 21 , wherein the stabilising coupling is connected to the energy converting device upstream of the centre of resistance.

22. A method according to any one of claims 1 1 to 21 , and further comprising deploying a cable from the marine vessel into water comprising dispensing a cable and guiding the cable into the water from a lateral edge of the vessel.

23. A method according to any one of claims 1 1 to 22, and further comprising working at a sub-marine surface comprising manoeuvring a sub-marine tool arrangement through a deck opening of the vessel having a plurality of hulls, the opening being between respective hulls and lowering the sub-marine tool to the submarine surface.

24. A marine vessel comprising a cable dispensing device including a cable to be deployed into water and a cable guiding device attached to a lateral edge region of the vessel for guiding the cable from the lateral edge of the vessel.

25. A marine vessel according to claim 24, wherein the cable is a sub-sea power and/or communications cable.

26. A marine vessel according to claim 24, and further comprising a cable engine mounted on the deck of the vessel.

27. A marine vessel according to any one of claims 24 to 26, and further comprising a cable touch-down monitoring device.

28. A method of deploying a cable from a marine vessel into water comprising dispensing a cable and guiding the cable into the water from a lateral edge of the vessel.

29. A method according to claim 28, and further comprising tracking of the cable as it is laid upon the seabed with a cable touch-down monitoring device.

30. A marine vessel comprising a plurality of hulls connected by a deck surface having an opening therein between respective hulls and a tool arrangement for working at a sub-marine surface arranged to be manoeuvred into a column of water through the opening.

31 . A marine vessel according to claim 30, wherein the tool arrangement is for performing drilling work into the sea bed surface.

32. A marine vessel according to claim 30 or 31 , wherein the tool arrangement is for performing for mining work at the sea bed surface.

33. A marine vessel according to claim 32, wherein the mining tool arrangement incorporates a system to remove material at the seabed in an enclosed unit and pump the mixture of sea water and seabed deposits up to the deck of the vessel by way of a mining tool outlet umbilical to a filtration unit inside the enclosed unit.

34. A method of working at a sub-marine surface comprising manoeuvring a sub- marine tool arrangement through a deck opening of a vessel having a plurality of hulls, the opening being between respective hulls and lowering the sub-marine tool to the sub-marine surface.

35. A method according to claim 34, wherein the tool arrangement is for performing drilling work into the sea bed surface.

36. A method according to claim 34 or 35, wherein the tool arrangement is for performing for mining work at the sea bed surface.

37. A method according to claim 36, wherein the mining tool arrangement incorporates a system for removing material from the seabed in an enclosed unit and to pump this mixture of sea water and seabed deposits up to the deck of the vessel by way of a mining tool outlet umbilical to a filtration unit inside the enclosed unit.