NL2021841B1 - Combination of heavy lift vessel and floating appendage structure - Google Patents
Combination of heavy lift vessel and floating appendage structure Download PDFInfo
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- NL2021841B1 NL2021841B1 NL2021841A NL2021841A NL2021841B1 NL 2021841 B1 NL2021841 B1 NL 2021841B1 NL 2021841 A NL2021841 A NL 2021841A NL 2021841 A NL2021841 A NL 2021841A NL 2021841 B1 NL2021841 B1 NL 2021841B1
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
- B63B35/003—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for for transporting very large loads, e.g. offshore structure modules
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
- B63B35/40—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for for transporting marine vessels
- B63B35/42—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for for transporting marine vessels with adjustable draught
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B17/02—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto
- E02B17/027—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto steel structures
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B2017/0039—Methods for placing the offshore structure
- E02B2017/0047—Methods for placing the offshore structure using a barge
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B2017/0052—Removal or dismantling of offshore structures from their offshore location
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B2017/0056—Platforms with supporting legs
- E02B2017/0069—Gravity structures
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B2017/0056—Platforms with supporting legs
- E02B2017/0073—Details of sea bottom engaging footing
- E02B2017/0086—Large footings connecting several legs or serving as a reservoir for the storage of oil or gas
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Transportation (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Ocean & Marine Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Filling Or Discharging Of Gas Storage Vessels (AREA)
- Load-Engaging Elements For Cranes (AREA)
Abstract
The present invention relates to a combination of a heavy lift vessel and an floating appendage structure which are interconnected by a hinge having a horizontal hinge axis , wherein: - the heavy lift vessel comprises: 0 at least one crane comprising a crane boom , wherein the heavy lift vessel is configured to carry out heavy lift operations by itself, i.e. without the floating appendage structure, 0 at least one vessel hinge assembly , - the floating appendage structure is configured to lift a heavy structure at sea and comprises: o a hull , 0 at least one appendage hinge assembly configured to be connected to the vessel hinge assembly and to form the hinge therewith, 0 at least one crane line connector mounted to the hull, wherein the heavy lift vessel and the floating appendage structure are interconnected via the hinge, wherein the hinge allows a rotation of the floating appendage structure relative to the heavy lift vessel about the hinge axis, and wherein a crane line suspension point of the at least one crane boom is positioned above the floating appendage structure, wherein the at least one crane is connected to the floating appendage structure, wherein at least one first crane line extends from the first crane line connector to the crane line suspension point of the at least one crane and wherein at least one second line extends from the second crane line connector to the crane line suspension point of the at least one crane,
Description
The invention relates to a combination of a heavy lift vessel and an floating appendage structure for the installation and/or removal of large offshore structures.
BACKGROUND OF THE INVENTION
General market
Currently the largest crane capacity is limited to approximately lO.OOOmT per crane. For a dual crane construction vessel the current maximum capacity is 20.000mT. When considering the reach required for lifting, this capacity is decreased. There is a general need for solutions that can remove and install larger topsides and possibly jackets or other types supporting structures in one piece. An installation and/or removal in one piece results in a smaller risk for the operator, in a reduced environmental impact and in an overall reduction of cost.
Larger loads can be lifted by a vessel (or a barge) which is positioned underneath the loads using buoyancy as the lifting force. However, the majority of platforms / jacket designs prevent the vessel to be positioned directly underneath the load because the jacket or other support construction is located there. Hence a different type of hull shape is required for the lifting vessel, such as a dual hull or a U-shaped type lifting vessels. Over the course of time several options have been developed. Some of these are already in use, such as the Pioneering Spirit operated by Allseas and the Versatruss operated by Versabar. These solutions are known to have high operational costs (OPEX) and also require a high initial investment (CAPEX).
Single lift dedicated vessels
The construction of a large (double) hull that is capable of lifting large offshore platforms (i.e. Pioneering Spirit) has a high initial cost and results in a high OPEX. Although the need was seen by Allseas to include an alternative operational mode in the vessel (i.e. a pipelay mode for laying pipelines on the seabed) the added vessel and equipment are always
-2present and idle when not in use. This all adds to the operational cost (OPEX) of the vessel, also during the alternative use (of pipelay mode).
Another drawback of the Pioneering Spirit and other lifting vessels is the limited capability of varying the draft of the vessel. The underside of a top side or module support frame (MSF) is generally the preferred location where the topside should be engaged for an installation procedure or a removal procedure in one piece. The underside of an installed topside on a jacket is generally positioned quite high above the water level in order to keep the topside out of reach of the waves in case of a storm. However, when transferred to shore, the preferred height of a topside which is to be scrapped is quite low, so the workers can easily and safely reach the topside. Therefore, at some point in time - preferably as soon as possible - it is desired to lower the topside during a removal operation. The desire to lower the topside also applies when a topside is scrapped directly from a removal vessel or barge.
For an installation procedure, the same may apply, but in an opposite sequence. It may be preferable to build the topside at a low location and to install the topside quite high on the jacket. The Pioneering Spirit is not capable of varying its height in order to change the level of the topside, or only to a very limited extent.
Other solutions are also known in this field. For instance, various parties have conceived a dedicated U shape vessel. For instance the MPU heavy Heavy Lifter of MPU Offshore Lift ASA) is a purpose built vessel which was only intended for the lift of (large) offshore platforms. Although fabrication had started, this was halted at an early stage and the project was eventually completely stopped. In general, lifting operations of heavy structures offshore are quite rare and these vessels remain idle for a large part of the time. This results in a need to earn back a large initial investment in a limited number of offshore operations, driving up the costs. Also, most designs require accomodation, propulsion and other equipment to be incorporated in the single purpose vessel. This further increases the initial investment.
Floating appendage structures in combination with an existing vessel
Appendages (also called floating appendage structures) to existing vessels to perform single lifts have also been conceived and circumvent the drawbacks of dedicated vessels as outlined above. One proposed solution (Global Maritime, GM-Lift Decommissioning and Installation Vessel) as presented in W00160688A1 uses a combination of a semi
- 3submersible vessel and an floating appendage structure which are coupled to one another. The floating appendage structure has a U-shape, when seen in top view. The GM lifter is considered to form the closest prior art for the present invention.
In the GM-Lift Decommissioning and Installation Vessel as presented in W00160688A1, the coupling between the (main) semi-submersible vessel and the floating appendage structure comprises a right and a left connection at deck level and a right and left connection at the level of the floater (and possibly over the complete height).
A drawback of this solution is that the coupling between the floating appendage structure and the heavy lift vessel is put under heavy loads during operation. The cause of these large environmental loads (mainly hogging and sagging) which result in large bending moments in the combination. These bending moments need to be carried by the coupling.
The large loads necessitate extensive stiffening of both the main vessel and the floating appendage structure near the coupling. This in turn renders the ships relatively heavy, complex and expensive to build. A hinged coupling (moment free) would reduce the loads, but introduces the challenge of having to cope with relative motions between the two vessels. Relative motions are generally undesirable.
A further disadvantage of the GM-Lift Decommissioning and Installation Vessel is that a transfer operation of a topside from the GM-Lift Decommissioning and Installation Vessel to a barge or vice versa is quite difficult. This is related to the U-shape, which prevents a barge from traversing the GM-Lift Decommissioning and Installation Vessel.
It is noted that if in the GM-Lift Decommissioning and Installation Vessel the coupling breaks when the floating appendage structure carries a topside, this will almost certainly result in the loss of both the floating appendage structure and the topside itself. Most likely it will also result in the loss of the main vessel. In fact it is questionable whether the kind of coupling as envisaged in the GM-Lift Decommissioning and Installation Vessel can be constructed sufficiently strong for such a combination to be seaworthy. The GM-Lift Decommissioning and Installation Vessel was never built and it may have been that the decision to cancel this project was related to the uncertainties surrounding the strength of the coupling and its technical feasibility and the associated risks and costs. Summarizing, the GM-Lift Decommissioning and Installation Vessel has a questionable technical feasibility.
- 4Transfer of the lifted structure to and from a barge
During an offshore installation or removal operation, the structure, e.g. the topside, is typically transferred from a barge to the lifting vessel or vice versa. For a removal operation, the topside is typically transferred from the lifting vessel to a barge. All of the proposed solutions above display a restricted access of a barge underneath the structure which is lifted by the lifting vessel. This prevents the structure from being positioned in the most favourable position on the barge (lengthwise): centrally where the centre of buoyancy relatively lines up with the platform’s centre of gravity as to minimise ballasting and thus barge capacity.
Conversely, the load needs to be positioned eccentrically on the barge, i.e. near the front end or rear end of the barge. This creates large longitudinal bending moments on the vessel or barge. The eccentric position necessitates the use of large barges or purpose-built barges with large section moduli and resulting large barge depth to withstand the loads exerted.
Beside technical drawbacks, this adds to both the CAPEX and OPEX of the complete system as the added barge(s) need to be earned back by the same operations, as typically no such barges are required in the market for any other kind of operation.
OBJECT OF THE INVENTION
It is an object of the invention to provide a method of performing a heavy offshore lift operation, typically greater than the crane lifting capacity at reach of the vessel, in particular for the installation or removal of a topside or part thereof or other heavy structure at sea, which requires a limited financial investment (CAPEX) and results in relatively small operational expenses (OPEX). It is an object to keep the operational expenses relatively small both in use and in idle mode.
It is a further object of the invention to provide a combination of a main vessel and one or more floating appendage structures for carrying out the method.
SUMMARY OF THE INVENTION
In order to achieve at least one object, the invention provides a combination of a heavy lift vessel and an floating appendage structure which are interconnected by a hinge having a horizontal hinge axis , wherein:
- 5the heavy lift vessel comprises:
o at least one crane comprising a crane boom , wherein the heavy lift vessel is configured to carry out heavy lift operations by itself, i.e. without the floating appendage structure, o at least one vessel hinge assembly , the floating appendage structure is configured to lift a heavy structure at sea and comprises: o a hull, o at least one appendage hinge assembly configured to be connected to the vessel hinge assembly and to form the hinge therewith, o at least one crane line connector mounted to the hull, wherein the heavy lift vessel and the floating appendage structure are interconnected via the hinge, wherein the hinge allows a rotation of the floating appendage structure relative to the heavy lift vessel about the hinge axis, and wherein a crane line suspension point of the at least one crane boom is positioned above the floating appendage structure, wherein the at least one crane is connected to the floating appendage structure, wherein at least one first crane line extends from the first crane line connector to the crane line suspension point of the at least one crane.
The combination according to the invention provides the capability of lifting operations of very heavy loads for relatively low capital costs, both CAPEX and OPEX. Also, use can be made of an already existing heavy lift vessel which only needs to be converted to a limited extent by adding a part of a hinge to the heavy lift vessel.
The skilled person will understand that if the vessel rolls, the hinge axis will not be horizontal. Horizontal in this context is intended to refer to the reference frame of the heavy lift vessel itself.
In an embodiment, wherein the at least one crane line is under pretension and exerts an upward force on the floating appendage structure, wherein the crane line under pretension limits the freedom of movement of the floating appendage structure relative to the heavy lift vessel. This is a very effective alternative to the rigid connection on the GM lift Decommissioning and Installation Vessel. The alternative according to the invention is technically feasible, which is uncertain for the rigid connection of the GM lift Decommissioning and Installation Vessel.
- 6In an embodiment, the pretension causes the heavy lift vessel and the floating appendage structure to move in tandem, with motion characteristics resembling the motion characteristics of a single rigid vessel. With relatively simple and cost-effective means, a very large rigid vessel is mimicked with the combination according to the invention.
In an embodiment, the heavy lift vessel comprises:
a first crane and a second crane positioned at a distance from the first crane, wherein the floating appendage structure comprises:
a first crane line connector which is positioned on a first side of the hull of the floating appendage structure, and a second crane line connector which is positioned on a second side of the floating appendage structure, and wherein a first crane line is connected to the crane line suspension point of the first crane and to the first crane line connector and a second crane line is connected to the crane line suspension point of the second crane and the second crane line connector.
The first crane and the second crane added stability and rigidity to the overall combination.
In an embodiment, the first crane is positioned on the right side of the heavy lift vessel and the first crane line connector is positioned on a right side of the floating appendages structure , and wherein the second crane is positioned on the left side of the heavy lift vessel and the second crane line connector is positioned on a left side of the floating appendages structure. This configuration has a general longitudinal arrangement. It was found that this configuration has relatively little low drag forces during transit. Furthermore, use can be made of an already existing heavy lift vessel.
In an embodiment, when seen in top view the first and second crane define a crane axis , wherein the crane axis extends parallel to the hinge axis.
In an embodiment, when seen in top view the first and second crane are positioned on a same side or end of the heavy lift vessel as the vessel hinge part, said side or end being the right side, the left side the bow or the stern of the heavy lift vessel.
In an embodiment, the vessel hinge assembly comprises a first vessel hinge part and a second vessel hinge part which are positioned at a distance from one another, and wherein
- 7the appendage hinge assembly comprises a first appendage hinge part associated with the first vessel hinge part and a second appendage hinge part associated with the first vessel hinge part.
In an embodiment, the heavy lift vessel is a semi-submersible vessel, comprising: one or more floaters, in particular a right floater and a left floater, a deck structure , multiple columns which extend upward over a vertical distance from the at least one floater and which interconnect the floater with the deck structure, wherein the columns define open areas between the columns, a ballasting system for varying the draught of the heavy lift vessel.
Heavy lift vessels in the form of a semisubmersible vessel have the advantage of being less sensitive to waves when the columns are positioned in the water line. The columns have a relatively small water piercing surface area, which results in very calm behavior.
In an embodiment, the floating appendage structure is a semi-submersible vessel, comprising:
one or more floaters, multiple columns which extend upward from the at least one floater over a vertical distance and define open areas between the columns, and ballasting tanks which can be filled end emptied for varying the draught of the floating appendage structure.
A floating appendage structure in the form of a semi-submersible vessel was found to provide excellent characteristics during transfer operations at sea and in short. When ballasted to a draft in which the columns are in the water line, the floating appendage structure displays very calm behaviour.
In an embodiment, when seen in top view the floating appendage structure has a right floater and a left floater. This has the benefit of low drag forces during transit mode.
In an embodiment, when seen in side view the at least one crane line, in particular the first crane line and the second crane line, extend under an angle of less than 35 degrees to the vertical, in particular less than 20 degrees. In this way, horizontal forces between the heavy lift vessel and the floating appendage structure and the offlead load on the crane are limited.
- 8In an embodiment, the first vessel hinge part is connected to a first column of the heavy lift vessel and the second vessel hinge part is connected to a second, different column of the heavy lift vessel. It was found that this has the benefit of a very strong and rigid hinge
In an embodiment, the first vessel hinge part and the second vessel hinge part are connected to respectively a first side of the first column and to a second side of the second column, wherein the first side and second side face one another.
In an embodiment, the floating appendage structure, when seen in top view, has a Ushape or H-shape, the U-shape or H-shape, having a right elongate part and a left elongate part and a cross-connection.
In an embodiment, the floating appendage structure comprises an opening between the floaters at one end, and a transverse structure between the floaters at the opposite end, wherein the transverse structure is located higher than the floaters but lower than the upper ends of the columns of the floating appendage structure, and in particular about halfway the height of the columns of the floating appendage structure.
In an embodiment, the columns of the floating appendage structure define a passageway which traverses the floating appendage structure, the passageway extending from a first opening located between a front right column and a front left column of the floating appendage structure and a second opening located between a rear right column and a rear left column of the floating appendage structure, wherein a barge or combination of barges can move completely through said passageway, thereby traversing the floating appendage structure when the floating appendage structure is ballasted at a deep draft.
The passageway extends in the longitudinal direction of the floating appendage structure and makes it easy to position a topside or other heavy structure centrally on the barge. The barge can travel through the passageway and be positioned with its center of buoyancy directly underneath the center of gravity of the topside.
In an embodiment, the vessel hinge assembly comprises a first hole and a second hole which are aligned, wherein the appendage hinge assembly comprises a first pin which is inserted in the first hole and a second pin which is inserted in the second hole. It was found that this type of hinge is very strong and reliable, which is essential for this application.
In an embodiment, the first pin and second pin are rigidly interconnected by a beam or truss construction.
- 9In an embodiment, the first vessel hinge part and the second vessel hinge part each comprise a flat plate which positioned with one of the main faces thereof against a column and welded to a column at least at the circumference thereof, wherein the plate comprises the hole .
In an embodiment, the appendage hinge assembly is connected to the rest of the floating appendage structure via an open truss frame. This further limits the water piercing surface of the floating appendage structure when positioned with the columns in the water line. This further reduces motions of the floating appendage structure as a result of waves.
In an embodiment, the vessel hinge assembly is provided above the floater of the heavy lift vessel. This reduces drag, and make it possible to position the hinge above the floaters of the floating appendage structure.
In an embodiment, the vessel hinge assembly is provided at the level of the columns of the heavy lift vessel.
In an alternative embodiment, the vessel hinge assembly is provided at the level of the deck structure of the heavy lift vessel.
In an embodiment, the floating appendage structure does not comprise: a propulsion system, a living quarters or a helicopter deck. In this way the floating appendage structure remains cost-effective.
In an embodiment, Combination according to any of the preceding claims, the columns of the floating appendage structure have a smaller water piercing surface than the columns of the heavy lift vessel. This reduces the motions of the floating appendage structure.
In an embodiment, one or more columns of the floating appendage structure, are formed entirely or partially as a truss structure.
In an embodiment, one or more columns of the floating appendage structure comprise an upper part having a greater water piercing surface than a lower part of the column, wherein in particular the upper part is formed as a closed box and the lower part is formed as a truss structure.
In an embodiment, the upper ends of the columns of the floating appendage structure are interconnected by one or more beams which extend lengthwise of the floating appendage structure.
- 10In an embodiment, the first crane line connector and the second crane line connector define a connector axis which extends parallel to the hinge axis and in particular parallel to the crane axis.
In an embodiment, when seen in top view the at least one crane line connector is positioned at a distance from the hinge axis which is greater than 35 percent, in particular greater than 45 percent of a distance from the hinge axis to the opposite side or end of the floating appendage structure.
In an embodiment, the vessel hinge assembly is located at the bow or stern of the heavy lift vessel, and wherein the hinge axis extends orthogonal to a main longitudinal direction of the heavy lift vessel.
In an embodiment, the vessel hinge assembly is located at the right or left side of the heavy lift vessel and wherein the hinge axis extends parallel to a main longitudinal direction of the heavy lift vessel.
In an embodiment, the floating appendage structure comprises a plurality of crossbeams which rest on the upper end of the columns or on longitudinal beams which rest on the columns of the floating appendage structure, wherein the cross-beams extend over the open lifting area from a right side of the floating appendage structure to a left side of the floating appendage structure.
In an embodiment, the floating appendage structure comprises a hydraulic lift system configured to raise the cross-beams relative to the at least one hull of the floating appendage structure.
The present invention also relates to a method of lifting a heavy structure at sea, the method comprising:
providing the combination of the heavy lift vessel and the floating appendage structure according to any of the preceding claims, positioning a heavy structure such as a topside on the floating appendage structure, putting the at least one crane line under pre-tension, wherein the at least one crane line under pretension limits the freedom of movement of the floating appendage structure relative to the heavy lift vessel.
The method provides substantially the same advantages as the combination.
- 11 In an embodiment of the method, the at least one crane line under pretension causes the heavy lift vessel and the floating appendage structure to move in tandem, with motion characteristics resembling the motion characteristics of a single rigid vessel.
In an embodiment of the method, when seen in top view at least one barge is positioned between the right floater and the left floater of the floating appendage structure under the heavy structure, and wherein the heavy structure is transferred from the barge onto the floating appendage structure or from the floating appendage structure to the barge.
In an embodiment of the method:
a topside is lifted from a jacket or other substructure by positioning the U-shaped part of the floating appendage structure around the jacket or other substructure and by subsequently deballasting the heavy lift vessel and the floating appendage structure together, thereby lifting the topside from the jacket or jacket, or a topside is installed onto a jacket by carrying the topside with the floating appendage structure and by positioning the U-shaped part of the floating appendage structure around the jacket or other substructure, and subsequently ballasting the heavy lift vessel and the floating appendage structure, thereby lowering the heavy lift vessel, floating appendage structure and the topside and placing the topside onto the jacket or other substructure.
In an embodiment of the method, the floating appendage structure comprises a hydraulic lift system configured to raise the cross-beams relative to the at least one hull of the floating appendage structure, wherein for making the initial contact between the floating appendage structure and the heavy structure which is to be lifted the hydraulic system raises the cross-beams relative to the hull.
In an embodiment of the method:
a topside or other heavy structure is transferred from a barge to the floating appendage structure, and wherein:
o the topside or other heavy structure is positioned centrally on the barge, o the floating appendage structure is ballasted to a deep draft, o the barge including the topside or other heavy structure is positioned in the Ushaped part of the floating appendage structure, and o the floating appendage structure is deballasted, thereby decreasing the draught of the floating appendage structure, wherein the floating appendage structure lifts the topside or other heavy structure from the barge,
- 12a topside or other heavy structure is transferred from the floating appendage structure to at least one barge or vessel, wherein:
o the topside or other heavy structure is positioned on the floating appendage structure, o optionally the floating appendage structure including the topside or other heavy structure is pre-ballasted to a deeper draught, o the barge is positioned in the U-shaped part of the floating appendage structure, and o the floating appendage structure is ballasted, thereby increasing the draught of the floating appendage structure, wherein the floating appendage structure is lowered and places the topside or other heavy structure on the barge.
In an embodiment, the method comprises the subsequent steps of:
ballasting the combination which carries the heavy structure until the columns pierce the water line, uncoupling the floating appendage structure from the heavy lift vessel, positioning at least one barge in the passageway of the floating appendage structure further ballast the floating appendage structure until the heavy structure is positioned on the at least one barge.
The present invention further relates to a floating appendage structure configured to lift a heavy structure at sea, the floating appendage structure comprising:
a hull, at least one appendage hinge assembly configured to be connected to a vessel hinge part of a heavy lift vessel and to form a hinge therewith, at least one crane line connector mounted to the hull, wherein the floating appendage structure is configured to be interconnected via the hinge to the heavy lift vessel, wherein the hinge allows a rotation of the floating appendage structure relative to the heavy lift vessel about the hinge axis.
These and other aspects of the invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like parts.
- 13SHORT DESCRIPTION OF THE FIGURES
Figure 1 shows an isometric view of the combination according to the invention.
Figure 2 shows a top view of the combination according to the invention.
Figure 3 shows a side view of the combination according to the invention.
Figure 4 shows a rear or front view of the combination according to the invention.
Figure 5 shows an isometric view of the combination according to the invention carrying a topside.
Figure 6 shows a top view of the combination according to the invention carrying a topside.
Figure 7 shows a side view of the combination according to the invention carrying a topside.
Figure 8 shows a front view of the combination according to the invention carrying a topside.
Figure 9A shows an isometric view of the floating appendage structure.
Figure 9B shows a further isometric view of the floating appendage structure.
Figure 9A shows yet a further isometric view of the floating appendage structure.
Figure 10A shows an isometric view of the hinge.
Figure 10B shows they another isometric view of the hinge, with the rest of the heavy lift vessel and the appendage vessel left out.
Figure 11 shows a top view of the hinge.
Figure 12A shows an isometric view of a part of the hinge.
Figure 12B shows another isometric view of a part of the hinge.
Figure 12C shows a top view of a part of the hinge.
Figure 13A shows an isometric view of the installation or removal of a topside from a substructure.
Figure 13B shows an isometric view of the uncoupled floating appendage structure carrying a topside.
Figure 14 shows a front view of the uncoupled floating appendage structure carrying a topside.
Figure 15 shows a side view of the uncoupled floating appendage structure carrying a topside.
Figure 16 shows a top view of the uncoupled floating appendage structure carrying a topside.
Figure 17 shows the same view as figure 13B, but with two barges positioned under the topside and under the cross beams.
Figure 18 shows a side view associated with figure 17.
- 14Figure 19 shows a top view associated with figure 17 and 18.
Figure 20 shows a front view associated with figure 17-19.
Figure 21 shows an isometric view of the floating appendage structure with two barges.
Figure 22 shows a front view of the floating appendage structure with two barges.
Figure 23 shows a side view of the floating appendage structure with two barges.
Figure 24A shows a top view of another embodiment of the invention.
Figure 24B shows a top view of yet another embodiment of the invention.
Figure 25 shows a front view of the embodiment of figure 24.
Figure 26 shows a top view of yet another embodiment of the invention
Figure 27 shows a top view of again another embodiment of the invention.
DETAILED DESCRIPTION OF THE FIGURES
Turning to figures 1 - 4, a combination 10 of a heavy lift vessel 12 and a floating appendage structure 14 is provided. The heavy lift vessel 12 and the floating appendage structure 14 are interconnected via a hinge which will be discussed further below.
The heavy lift vessel 12 is a semi-submersible vessel, comprising one or more floaters, in particular a right floater 56A and a left floater 56B and a deck structure 57. The heavy lift vessel 12 comprises multiple columns 58 which extend upward over a vertical distance from the at least one floater and which interconnect the floaters with the deck structure. The columns 58 are arranged in a right row 61A and a left row 61B.
The columns define open areas 59 between the columns. The columns have a lower water piercing surface than the combined floaters. The heavy lift vessel comprises a ballasting system for varying the draught of the heavy lift vessel. Such ballasting systems are known per se for semi-submersible vessels.
The heavy lift vessel 12 comprises at least one crane 15. In the embodiment of figures 1 - 4 the heavy lift vessel comprises two cranes, a first crane 15A and a second crane 15B. The second crane 15B is positioned at a distance from the first crane. The cranes have a rotatable turret which allows rotation of the crane about a respective vertical axis.
However, as will be discussed further below in principle the invention is also possible with only a single crane 15.
- 15Each crane 15A, 15B comprises a crane boom 20. The heavy lift vessel is configured to carry out heavy lift operations by itself, namely with the cranes 15A, 15B, and without the floating appendage structure 14. The heavy lift vessel comprises accommodation 31, a helicopter deck 32, propulsion 33, and may comprise further equipment.
The floating appendage structure 14 is configured to lift a heavy structure at sea and comprises a hull 22. The floating appendage structure 14 and in particular the hull 22 thereof may be of a semi-submersible type.
The floating appendage structure 14 is a semi-submersible vessel, comprising one or more floaters, in this case a right floater 60A and a left floater 60B. The floating appendage structure 14 comprises multiple columns 62 which extend upward from the at least one floater over a vertical distance and define open areas 63 between the columns, and ballasting tanks which can be filled end emptied for varying the draught of the floating appendage structure.
The upper ends 90 of the columns 62 of the floating appendage structure are interconnected by one or more beams 92A, 92B which extend lengthwise of the floating appendage structure. The floating appendage structure does not have a “real” deck structure, because a central part is open for carrying out lifting operations.
The pumps for the ballasting tanks and other equipment on board may be temporary removable in order to lower the Capex.
The columns 62 of the floating appendage structure 14 have a smaller water piercing surface than the columns of the heavy lift vessel. This improves the lift characteristics. For the stability, the floating appendage structure 14 benefits from the stability of the heavy lift vessel when coupled to the heavy lift vessel.
The floating appendage structure 14 does not comprise: a propulsion system, a living quarters or a helicopter deck. The floating appendage structure 14 relies on the heavy lift vessel for these aspects, which keeps the floating appendage structure 14 cost-effective
The floating appendage structure 14, when seen in top view, has a U-shape having a right elongate part formed by the right floater and a left elongate part formed by the left floater and a cross-connection which will be discussed later. In an alternative embodiment, the floating appendage structure 14 may have an H-shape.
- 16The floating appendage structure comprises an opening 70 between the floaters at one end 72, and a transverse structure 74 between the floaters at the opposite end.
The floating appendage structure does not have a transverse connection at the level of the upper ends of the columns 62. This provides a passageway 77 for a barge to travel through when the floating appendage structure is ballasted at a deep draft.
The floating appendage structure 14 comprises at least one crane line connector 24A, 24B which are mounted to the hull 22. The first crane line connector 24A is positioned on a first side of the hull (in this case the right side) of the floating appendage structure and the second crane line connector 24B is positioned on a second side of the floating appendage structure (in this case the left side).
The first crane line connector 24A and the second crane line connector 24B define a connector axis 93 which extends parallel to the hinge axis and in particular parallel to the crane axis 17, see fig. 2.
When seen in top view the at least one crane line connector 24A, 24B is positioned at a first distance D1 from the hinge axis 45 which is greater than 35 percent, in particular greater than 45 percent of a second distance D2 between the hinge axis 45 to the opposite end 95 of the floating appendage structure 14.
One or more columns 62 of the floating appendage structure 14 may be formed entirely or partially as a truss structure.
Alternatively or additionally, one or more columns 62 of the floating appendage structure 14 may comprise an upper part having a greater water piercing surface than a lower part of the column, wherein in particular the upper part is formed as a closed box and the lower part is formed as a truss structure.
A crane line suspension point 26A, 26B of the at least one crane boom is positioned above the floating appendage structure. The at least one crane is connected to the floating appendage structure via at least one crane line 28A, 28B. Figure 1-4 show that each crane 15A, 15B is connected to the floating appendage structure via multiple crane lines.
The at least one first crane line 28A extends from the first crane line connector 24A to the crane line suspension point 26A, of the first crane. The at least one second crane line 28B
- 17extends from the second crane line connector 24B to the crane line suspension point 26B of the second crane 15B.
When seen in side view the at least one crane line, in particular the first crane line 28A and the second crane line 28B, extend(s) under an angle a of less than 35 degrees to the vertical 19, in particular less than 20 degrees.
The first crane 15A is positioned on the right side of the heavy lift vessel and the first crane line connector 24A is positioned on a right side of the floating appendages structure. The second crane 15B is positioned on the left side of the heavy lift vessel and the second crane line connector 24B is positioned on a left side of the floating appendages structure.
When seen in top view the first and second crane 15A, 15B define a crane axis 17.
Turning to figures 5, 6, 7, 8, the same combination 10 is shown, but this time carrying a topside 30. It will be clear for the skilled person that the combination 10 can lift a topside 30, but also other types of heavy structures, such as a jacket, a vessel, or another type of heavy structure which is to be lifted.
In use, the at least one crane line 28A,28B is under pretension and exerts an upward force on the floating appendage structure 14. The crane line(s) 28A, 28B under pretension limits the freedom of movement of the floating appendage structure 14 relative to the heavy lift vessel 12.
The pretension causes the heavy lift vessel and the floating appendage structure to move in tandem, with motion characteristics resembling the motion characteristics of a single rigid vessel. The skilled person will understand that in practice, some movement may occur between the floating appendage structure and the heavy lift vessel. The skilled person will understand that a single rigid vessel also deforms somewhat under the influence of the forces of wind and waves. Therefore, absolute rigidity does not occur.
Turning to figs. 9A, 9B, 9C, the floating appendage structure comprises a plurality of cross-beams 100 which rest on the upper ends 76 of the columns or on the longitudinal beams 92A, 92B which rest on the columns 62 of the floating appendage structure. The cross-beams 100 extend over the open lifting area 102 from a right side of the floating appendage structure to a left side of the floating appendage structure.
- 18The floating appendage structure comprises a hydraulic lift system 104 configured to raise the cross-beams 100, i.e. move the cross-beams up or down, relative to the at least one hull 22 (and relative to the columns 62) of the floating appendage structure. See the arrow 105 in figures 9B and 9C.
Turning to figures 10A, 10B,11,12A,12B and 12C, the hinge 40 is shown in further detail. The hinge 40 comprises a part on the side of the floating appendage structure 14.This part is called the appendage hinge assembly 42 and is configured to be connected to the vessel hinge assembly 44 and to form the hinge 40 therewith.
The hinge 40 has a horizontal hinge axis 45. The heavy lift vessel 12 and the floating appendage structure 14 are interconnected via the hinge 40. The hinge allows a rotation of the floating appendage structure 14 relative to the heavy lift vessel 12 about the hinge axis 45. The crane axis 17 extends parallel to the hinge axis 45.
The first and second crane 15A, 15B are positioned on a same end 48 of the heavy lift vessel 12 as the vessel hinge assembly 44, said end being the stern of the heavy lift vessel. It is noted that a heavy lift vessel often moves backwards, wherein the stern becomes the bow. For a heavy lift vessel, the stern and bow may be exchangeable.
The hinge axis 45 extends orthogonal to a main longitudinal direction 99 of the heavy lift vessel.
The vessel hinge assembly 44 comprises a first vessel hinge part 50A and a second vessel hinge part 50B which are positioned at a distance from one another. The first vessel hinge part 50A is connected to a first column 58.1 of the heavy lift vessel and the second vessel hinge part is connected to a second, different column 58.2 of the heavy lift vessel. The columns are numbered 58.1-58.8, the uneven columns 58.1, 58.3, 58.5, 58.7 being located on the right side and the even columns 58.2, 58.4, 58.6, 58.8 being located on the left side.
The first vessel hinge part 50A and the second vessel hinge part 50B are connected to respectively a first side 59.1 of the first column 58.1 and to a second side 59.2 of the second column 58.2, wherein the first side and second side face one another.
The vessel hinge assembly 44 is provided above the floaters of the heavy lift vessel 12. In the shown embodiment, the vessel hinge assembly 44 is provided at the level of the
- 19columns 58 of the heavy lift vessel 12. Alternatively, the vessel hinge assembly 44 may be provided at the level of the deck structure of the heavy lift vessel.
The appendage hinge assembly 42 comprises a first appendage hinge part 51A associated with the first vessel hinge part 50A and a second appendage hinge part 51B associated with the first vessel hinge part 50B.
The transverse structure 74 may be located higher than the floaters but lower than the upper ends 76 of the columns 62 of the floating appendage structure, and in particular about halfway the height of the columns of the floating appendage structure. The transverse structure 74 provides rigidity to the floating appendage structure and interconnects the floaters 60A, 60B. The transverse structure 74 also serves as a base frame which connects the appendage hinge assembly 42 to the floaters 60A, 60B.
Alternatively, the transverse structure 74 may be located at the level of the floaters as indicated in the embodiment of figs 4 and 8. However, this is not preferred, because at this level, the transverse structure 74 creates drag in transit mode.
The vessel hinge assembly 44 comprises a first hole 80A and a second hole 80B which are aligned. The appendage hinge assembly 42 comprises a first pin 82A which is inserted in the first hole and a second pin 82B which is inserted in the second hole. The appendage hinge assembly 42 comprises a hydraulic system 47 (indicated in dashed lines in Fig. 12B) for moving the pins 2A, 82B along the hinge axis from an inward to an outward position and vice versa as indicated with arrow 83. This allows coupling and uncoupling of the floating appendage structure. The inward position allows coupling and uncoupling. In the outward position of the pins, the floating appendage structure and the heavy lift vessel are coupled.
The first pin 82A and second pin 82B are rigidly interconnected by a beam 85 or truss construction in order to take bending moments, notwithstanding the capability of inward and outward movement of the pins.
The first vessel hinge part 50A and the second vessel hinge part 50B each comprise a flat plate 88A, 88B which positioned with one of the main faces thereof against a column 58 and welded to a column at least at the circumference 89 thereof, wherein the plate comprises the hole 80.
The appendage hinge assembly 42 is connected to the rest of the floating appendage structure via an open truss frame 74.
- 20Turning to figures 13A-23, the columns 62 of the floating appendage structure 14 define a passageway 77 which traverses the floating appendage structure, the passageway extending from a first opening 78 located between a front right column 62.5 and a front left column 62.6 of the floating appendage structure 14 and a second opening 79 located between a rear right column 62.1 and a rear left column 62.2 of the floating appendage structure, wherein a barge or combination of barges can move completely through said passageway, thereby traversing the floating appendage structure when the floating appendage structure is ballasted at a deep draft.
Turning to figures 24A, 24B, and 25in an alternative embodiment, the vessel hinge assembly is located at the right or left side of the heavy lift vessel and wherein the hinge axis 45 extends parallel to a main longitudinal direction 99 of the heavy lift vessel. The combination 10 moves in the transport direction T, but may also move in the opposite direction.
In these embodiments, when seen in top view, the first and second crane 15A, 15B are positioned on a same side of the heavy lift vessel as the hinge axis, said side being the right side. Obviously the side can also be the left side. The opening 70 of the floating appendage structure is oriented in the same direction as the bow 110 of the heavy lift vessel.
In the embodiment of fig. 24A, the heavy lift vessel comprises two cranes. In the embodiment of fig. 24B, the heavy lift vessel comprises a single crane 15. The appendage hinge assembly 42 of the hinge 40 is connected to the floater
Turning to fig. 26, in a variant, the floating appendage structure is asymmetric and has an L-shape instead of a U-shape or H-shape. The floating appendage structure has only a single floater. This embodiment may require two cranes 15A, 15B.
Turning to fig. 27,the single crane 15 may also be used in a longitudinal configuration, i.e. wherein the crane 15 and the floating appendage structure 14 are positioned at the bow 110 or stern of the heavy lift vessel 12.
Operation
In operation, the method of lifting a heavy structure 30 comprises: providing the combination 10 of the heavy lift vessel 12 and the floating appendage structure according to any of the preceding claims, positioning a heavy structure 30 such as a topside on the floating appendage structure,
- 21 putting the at least one crane line 28 under pre-tension, wherein the at least one crane line under pretension limits the freedom of movement of the floating appendage structure relative to the heavy lift vessel.
The at least one crane line 28 under pretension may cause the heavy lift vessel 12 and the floating appendage 14 structure to move in tandem, with motion characteristics resembling the motion characteristics of a single rigid vessel.
Turning to figures 17-23, when seen in top view at least one barge 120 is positioned between the right floater 60A and the left floater 60B of the floating appendage structure under the heavy structure and under the cross-beams 100. The heavy structure 30 or other heavy structure including the cross beams 100 is transferred from the barge 120 onto the floating appendage structure 14 or from the floating appendage structure 14 to the barge 120.
The topside 30 or other heavy structure is positioned centrally on the barge. In top view the centre of gravity of the topside is close to the centre of buoyancy of the barge. This improves the stability and makes it possible to use a smaller, simpler and more cost-effective barge.
Removal of a topside
When removing a topside, the topside 30 will initially be present on a jacket or other substructure at sea.
The combination 10 travels to the location of the topside. The cross-beams 100 are installed on the floating appendage structure 14. The U-shaped part, H-shaped part or Lshaped part of the floating appendage structure 14 is positioned around the jacket or other substructure. See figure 13A. By subsequently deballasting the heavy lift vessel 12 and the floating appendage structure 14 together, thereby lifting the topside from the jacket or jacket. The cross-beams engage the topside 30 and lift the topside 30 from the jackets.
The floating appendage structure comprises a hydraulic lift system 104 configured to raise the cross-beams 100 relative to the at least one hull 22 of the floating appendage structure. The hydraulic system 104 raises the cross-beams 100 relative to the hull 22 for making the initial contact between the floating appendage structure and the heavy structure which is to be lifted. The hydraulic system 104 obviously have a limited stroke. After the initial contact, the ballast tanks are emptied, thereby raising the heavy lift vessel 12, the floating appendages structure and the topside 30 further.
-22The combination 10 then travels to an inshore location. Here the conditions (wave, wind) are more benign. Here, the topside or other heavy structure is transferred from the floating appendage structure to at least one barge or vessel. The floating appendage structure 14 may be uncoupled from the heavy lift vessel 12. Next, the floating appendage structure 14 including the topside 30 or other heavy structure is ballasted to a shallow draught. One or more barges 120 is positioned under the topside and under the cross-beams 100. The barge can travel through the passageway 77.
Next, the floating appendage structure 14 is ballasted, thereby increasing the draught of the floating appendage structure. The floating appendage structure is lowered and the topside 30 or other heavy structure including the cross-beams 100 is placed on the barge 120. Scrapping may then take place from the barge. This obviates the need for an extra transfer operation, or the need for a reinforced quayside or the need for a deep draft quayside.
Alternatively, the topside or other heavy structure may be transferred from the barge to a location on shore.
Installation of a topside
When installing a topside 30, the topside 30 is generally built on shore and first transferred shore to a barge 120.
Next, the topside 30 needs to be first transferred from the barge 120 to the floating appendage structure 14. In this procedure, the cross-beams are connected to the topside 30 on the barge. The cross-beams 100 may be moved underneath the topside 30 by a translational movement. Next, the floating appendage structure 14 is ballasted to a deep draft. In this stage the floating appendage structure 14 may be uncoupled from the heavy lift vessel 12.
Next, the barge 120 including the topside 30 or other heavy structure is positioned in the U-shaped part of the floating appendage structure. The cross-beams 100 are already present and connected to the topside 30. Next, the floating appendage structure 14 is deballasted, thereby decreasing the draught of the floating appendage structure, wherein the floating appendage structure lifts the topside or other heavy structure including the crossbeams 100 from the barge 120.
- 23Next, the floating appendage structure 14 including the topside 30 is coupled to the heavy lift vessel 12 at the hinge 40. Next the combination 10 travels to the target location where a substructure, e.g. a jacket has previously been installed. During the travel, the crane lines 28 are pretensioned, thereby providing rigidity and stability to the floating appendage structure 14.
Next, the topside is transferred to the substructure. In this step, the topside 30 is installed onto a jacket by carrying the topside 30 with the floating appendage structure 14 and by positioning the U-shape, H-shape or L-shape of the floating appendage structure 14 around the jacket or other substructure. See figure 13A. Subsequently the heavy lift vessel 12 and the floating appendage structure 14 are ballasted, thereby lowering the heavy lift vessel, floating appendage structure 14 and the topside 30 and placing the topside onto the jacket or other substructure.
Next, the cross-beams 100 are removed from the installed topside. The cross-beams may be withdrawn by a translational movement. The heavy lift vessel, floating appendage structure 14 then move away from the target location and travel back to an inshore location.
After an installation of removal operation, the floating appendage structure is uncoupled at an inshore location, and the heavy lift vessel is directly ready to perform an entirely different operation on its own, without the floating appendage structure. The floating appendage structure can remain in an inshore location to wait for a next operation.
The heavy lift vessel is only needed for the duration of the sailing and for the transfer operations.
Further general aspects
Typically the heavy lift vessel will be capable of lift operations in excess of 15.000 mT. However, smaller sizes are in principle also possible.
The columns of the heavy lift vessel may be closed. It is also possible that one or more of the columns of the heavy lift vessel are closed, whereas one or more other columns of the heavy lift vessel are open, and have a smaller water piercing surface.
The columns of the heavy lift vessel may be embodied in the form of truss structures.
- 24The deck structure of the heavy lift vessel will typically be closed and may provide buoyancy. A deck structure with buoyancy can be combines with columns in the form of truss structures.
In principle no heave compensation systems are needed for the crane lines.
A closed column combines both functionality in a single structure. This potentially results in a weight saving, but is more difficult to tune/adapt for different conditions/requirements.
The terms a or an, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising i.e., open language, not excluding other elements or steps.
Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention. It will be recognized that a specific embodiment as claimed may not achieve all of the stated objects.
The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
White lines between text paragraphs in the text above indicate that the technical features presented in the paragraph may be considered independent from technical features discussed in a preceding paragraph or in a subsequent paragraph.
Claims (44)
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2021841A NL2021841B1 (en) | 2018-10-19 | 2018-10-19 | Combination of heavy lift vessel and floating appendage structure |
| EP19828889.6A EP3867138B1 (en) | 2018-10-19 | 2019-10-21 | Combination of heavy lift vessel and floating appendage structure |
| PCT/NL2019/050691 WO2020080948A2 (en) | 2018-10-19 | 2019-10-21 | Combination of heavy lift vessel and floating appendage structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2021841A NL2021841B1 (en) | 2018-10-19 | 2018-10-19 | Combination of heavy lift vessel and floating appendage structure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| NL2021841B1 true NL2021841B1 (en) | 2020-05-13 |
Family
ID=64755670
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| NL2021841A NL2021841B1 (en) | 2018-10-19 | 2018-10-19 | Combination of heavy lift vessel and floating appendage structure |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP3867138B1 (en) |
| NL (1) | NL2021841B1 (en) |
| WO (1) | WO2020080948A2 (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3854297A (en) * | 1970-11-09 | 1974-12-17 | Shell Oil Co | Method and apparatus for laying marine pipelines |
| US3924415A (en) * | 1974-12-30 | 1975-12-09 | Santa Fe Int Corp | Column stabilized semisubmersible pipelaying barge |
| WO1990003470A2 (en) * | 1988-09-27 | 1990-04-05 | Sheffield And Adams Engineering, Inc. | Method and apparatus for erecting and removing offshore structures |
| WO2001060688A1 (en) | 2000-02-18 | 2001-08-23 | Vatsvaag Jan | A semi-submersible offshore lifting structure, and a method for using the same |
-
2018
- 2018-10-19 NL NL2021841A patent/NL2021841B1/en active
-
2019
- 2019-10-21 WO PCT/NL2019/050691 patent/WO2020080948A2/en unknown
- 2019-10-21 EP EP19828889.6A patent/EP3867138B1/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3854297A (en) * | 1970-11-09 | 1974-12-17 | Shell Oil Co | Method and apparatus for laying marine pipelines |
| US3924415A (en) * | 1974-12-30 | 1975-12-09 | Santa Fe Int Corp | Column stabilized semisubmersible pipelaying barge |
| WO1990003470A2 (en) * | 1988-09-27 | 1990-04-05 | Sheffield And Adams Engineering, Inc. | Method and apparatus for erecting and removing offshore structures |
| WO2001060688A1 (en) | 2000-02-18 | 2001-08-23 | Vatsvaag Jan | A semi-submersible offshore lifting structure, and a method for using the same |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2020080948A3 (en) | 2020-05-28 |
| EP3867138A2 (en) | 2021-08-25 |
| EP3867138B1 (en) | 2023-01-25 |
| WO2020080948A2 (en) | 2020-04-23 |
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