EP1492699B1

EP1492699B1 - Submersible watercraft

Info

Publication number: EP1492699B1
Application number: EP03721147A
Authority: EP
Inventors: Joop Roodenburg
Original assignee: Itrec BV
Current assignee: Huisman Equipment BV
Priority date: 2002-04-10
Filing date: 2003-04-10
Publication date: 2007-08-01
Anticipated expiration: 2023-04-10
Also published as: AU2003224498A1; WO2003086852A1; ATE368611T1; EP1492699A1; DE60315276D1; NO330075B1; NO20043671L

Abstract

A method for erecting an object, in particular a lifting frame, comprising the steps of: providing a floatable object having a base and a top; providing a submersible vessel; placing the floatable object on the vessel; transporting the vessel with floatable object to a desired location; ballasting the vessel to permit the floatable object to float; securing the base of the floatable object to the vessel; securing a hoist line between the floatable object and a winch on the vessel; winching the hoist line and thereby raising the floatable object top from the water while the base remains secured to the vessel. In a preferred embodiment the floatable object is a lifting frame, in particular an A-frame. Preferably the vessel is a catamaran.

Description

The present invention relates to a method for lifting, lowering and transporting an object at sea, e.g. from a barge to an installation site, wherein use is made of a catamaran.
From US 5,829,919 , on which the preamble of claim 1 is based, a method for removing a superstructure from a jacket placed on a sea-bottom is known, using a vessel constructed from two bulk carriers which are combined to form a whole while leaving clear an open space between their two ends.
This method involves submerging the catamaran under the intended topsides to be installed, then rising by deballasting to lift the topsides, then while either partially submerged or at normal draft, to transport that topsides to a new position, then by ballasting and positioning to depositing that topsides on the new structure.
The invention also relates to a method for picking up a topsides for decommissioning using a load lifting system which is integral to the vessel, carrying the topsides and redepositing the topsides using the same lifting system.
A method has long been needed for moving large topsides in one piece, in less than stable seas. The present invention was developed to enable the transport of rigs and drilling platforms even in rough seas by providing a vessel, which can move while submerged at one or more drafts, or to transport at normal draft. This is achieved by a method according to the characterizing part of claim 1.
The aspects of the invention will now be explained in further detail referring to the drawings showing, non-limitative examples. In the drawings:

FIG 1 is a top view of the catamaran with ballast systems.
FIG 2 is a starboard view of the catamaran with two moveable columns.
FIG 3 is a bow on view of the catamaran showing the air gap.
FIG 4 is a top view of the catamaran showing the bow structure as rounded triangular shapes.
FIG 5 shows three typical drafts for the catamaran.
FIG 6 shows a vertical positioning system usable on the catamaran disposed in a moveable column.
FIG 7 Shows the catamaran from the stern view using the vertical positioning system on an object at sea.
FIG 8 is a top view of the catamaran using the horizontal positioning system.
FIG 9 shows the catamaran wherein two of the moveable columns have been moved from positions on extreme ends of the hulls to a center area of the solid support structure.
FIG 10 is a top view of the catamaran with the hatch disposed across the bow.
FIG 11 is a stern view of the catamaran with a lift operation occurring.
FIG 22 is a view of the catamaran with a barge carrying a topsides prior to load transfer.
FIG 23 is a view of the catamaran carrying topsides on the detachable, moveable support columns while semi submerged.

In FIG 1, a catamaran (2) is shown having a bow (4) and a stern (6). The catamaran has a first hull (8) and a second hull (10).
The first and second hulls (8) and (10) each have a similar construction of bow, midsection and stern section.
In particular, the first hull has a first hull rounded triangular bow (50), a first hull, midsection (54), a first hull stern section (58), and first hull stern (62). The second hull (10) has a second hull rounded triangular bow (52), second hull midsection (56), second hull stern section (60) and second hull stern (64).
The first and second hulls (8) and (10) are disposed in a parallel relation to each other along a center line (158). In one embodiment, the first hull stern section (58) and the second hull stern section (60) have a tapered shape. Alternatively they can be of a rectangular design, however the tapered shape enables easier positioning of the catamaran when engaging objects at sea.
FIG 1 also shows that each hull has a ballast system. First hull (8) has ballast tank (34) and second hull (10) has ballast tank (35).
An air gap (13) which is shown in better detail in later Figures, is present between the first and second hulls and the solid support surface (12). A slot opening (15) is disposed between first and second hull stern sections. The slot opening in a preferred embodiment is between 10 and 80 meters in width and 10-80 meters in length. In a most preferred embodiment the slot opening (15) is 50 meters in width. Preferably, the slot opening (15) has a U-shape. The slot opening (15) is sized to position at least partially around a structure in a marine environment, such as around a jacket or a spar or similar deep draft floating caisson structure as shown in more detail in FIG 7. Other structures which could be positioned in slot opening (15) include a floating platform, a fixed leg platform or another floating vessel.
FIG 2 is a starboard view of the catamaran, shows that the support surface (12) forms a top on the first and second hulls. This solid support surface (12) can support very heavy loads.
The catamaran has two towers or columns which are disposed generally above the hulls approximately in a longitudinal symmetry plane.
The two hulls and the columns are rigidly interconnected by the support surface (12). The towers or columns can contain propulsion and control mechanisms, crew accommodation and other equipment, such as ROV's, diver work chambers, pipeline repair gear or other operating equipment.
Also the catamaran has load supporting moveable columns (14,16) and (17,19) which are disposed on the support surface (12). Additional moveable columns are also contemplated as usable on this catamaran. These load supporting moveable columns can support very heavy loads, such as a top sides, or objects, such as plates of steel or a hatch can be placed on the load supporting moveable columns and then a load placed on the hatch. These load supporting moveable columns can also be used as a lifting device in combination with a hatch of the catamaran.
Returning to FIG 1, four load supporting moveable columns are shown, as (14), (16), (17) and (19). In a most preferred embodiment, four moveable support columns are contemplated, two disposed on the first hull and two disposed on the second hull. However, it should be noted that between 2 and 10 load supporting moveable columns could be used on a catamaran. These columns can be skiddable on the support surface (12). Alternatively, these columns can be detachable from the support surface.
The support columns are detachably fitted on the hulls. This has the advantage that the support columns can be removed from the vessel at the point in time when they are not needed. This makes a difference in weight and, furthermore, space is made free on the deck in this way.
Furthermore, it is advantageous if the position of the support columns on the hulls is adjustable. The construction of the catamaran is so rigid and so strong that the position of the support columns on the hulls can be freely chosen. The support columns can be placed in an optimum position, depending on the load that has to be transported. The support columns can be positioned close to the stern of the catamaran.
The one or more fixed columns, with the crew accommodation etc. therein, are preferably located at the bow of the catamaran. Two fixed columns can also be disposed on the hulls, preferably one on each float.
It is possible that the open space between the two hulls is filled by hatches in order to increase the effective surface area of the deck. Provision is made that these hatches can be fixed to the side of the hulls. In this case the volume of the vessel is appreciably increased at this location. As a result the lifting capacity of the catamaran will be increased at the location of the hatches.
FIG 2 shows one of the two fixed columns, the first fixed column (18) disposed on the hull (8).
FIG 3 shows the second fixed column (20) disposed on the second hull (10). These fixed columns are contemplated to be single hulled or double hulled. Double hulling is helpful if the columns should contain a fluid that is harmful to the environment. This construction helps to create an environmental friendly vessel.
Returning to FIG 2, the ballast system (34) is shown disposed in the hull (8). It is contemplated that at least two ballast systems are used, one for each hull. FIG 1 shows the preferred positioning of each of the two ballast tanks which would be used in this vessel. These ballast systems are used to raise and lower the catamaran with respect to the waterline. The ballast systems can be used to keep the catamaran at first, a normal draft, or second, a slightly submerged draft, wherein water fills the air gap (13) between the first and second hulls (8) and (10) and the solid support surface (12) is above the water level, or third, a lower draft, wherein between 1 and 16 meters of water covers the solid support surface (12).
These three drafts are explained in more detail with reference to FIG 5. It is contemplated that the first and second ballast systems (34) and (35) can be used to raise and lower the catamaran between 10 and 90 percent of the overall height of the catamaran.
Returning to FIG 2, an optional propulsion system comprised of rotatable propellers and bow thrusters is shown for one of the two hulls. In particular, reference number 38 is a rotatable propeller connected to an engine (37), and reference numeral (39) is a thruster as is reference numeral 42. At least three propulsion devices can be located in each hull as an option. The equipment for operating these devices can be contained in the fixed column (18) and (20) or located in the hulls.
FIG 3 provides additional detail that the fixed columns (18) can contain crew accommodations (92) and/or a bridge command center, such as a navigational bridge (74) for piloting and commanding the vessel. The fixed column can contain catamaran operational equipment (93). The fixed columns can also support a helipad or second deck (72) as shown in this Figure.
It is contemplated as an option that each fixed column could support different structures. (74).Also notable in FIG 3 is the air gap (13) disposed between the two hulls.
FIG 4 shows a top view of the catamaran with the airgap (13) and the slot (15) as well as the support deck (12) in a position where the slot (15) is not covered by hatches. In this Figure, the two fixed columns (20) and (18) are shown disposed on the hulls Figure 4 shows the bow structure having the unique rounded triangular shape for each hull. The edges are shown as reference numeral 200 for hull (8) and reference numeral (202) for hull (10).
FIG 5 shows the way in which the catamaran can be submerged to at least 3 different draft depths. The first depth is shown as reference numeral (180), the second depth is shown as reference numeral (182) and the third depth is shown at reference numeral (184). It is contemplated that the vessel can move at any of these depths.
Figure 6 shows one element of the vertical positioning system (24) which is installed in at least two of the moveable columns and used for securing the catamaran to an object at sea. A first line (134) connects to an object at sea (1000). One end of this line (134) is secured substantially vertically to an object at sea (1000). The angle of attachment is usually not more than between 5 and 30 degrees from the vertical. Typically a second line (135) is used, as shown in FIG 7 and is also secured on one end, substantially vertically, no more than between 5 and 30 degrees from the vertical, to the same object at sea.
The object at sea (1000) is fitted into the opening slot (15) of the catamaran and secured with both lines. FIG 7 shows the object at sea secured in the opening slot (15).
FIG 7 is a stern view of the catamaran wherein the hull (8) and the hull (10) can be seen, as well as two moveable columns (14) and (16) each containing a vertical positioning device with motion compensation system.. Specifically, moveable column (14) contains the first vertical positioning device (24) and moveable column (16) contains the second vertical positioning device.
Returning to the detail of FIG 6, the vertical positioning system is a motion compensation system (138) disposed in the first load supporting moveable column (14). The other end of first line (134) engages this motion compensation system. In the second load supporting moveable column 16, an identical second motion compensation system is located and connected to the other end of the second line (135) (shown in FIG 7).
The first and second motion compensation systems (138 and 200) each comprises the same elements, which are shown in detail in FIG 6. Specifically the systems include a winch (77), the line (134 or 135) connected to the winch and vertically connectable to the object at sea (1000), a tension measuring device (79) connected to the line; a motion control device (80) connected to the line and winch for monitoring and controlling tension on the line. Sheaves or rollers or wheels 104a and 104b can be used to assist in the tensioning of the line. These rollers are preferably mounted at the top of the moveable columns, and the tensioning devices are mounted at the bottom of the device. The motion compensation systems also each comprise at least one pressurized cylinder (81) containing pressurized gas to control the system and assisting in the tensioning. Between 1 and 8 or more winches can be used in each motion compensation system.
A horizontal positioning system is also used on the vessel. This horizontal positioning can be a dynamic positioning system. FIG 8 shows the horizontal positioning system holding a spar or floating deep draft cassion vessel in the opening slot (15). The horizontal positioning system preferably consists of at least three maneuvering lines (25, 26, and 28) although four are shown in FIG 8, with the fourth maneuvering line having reference numeral (33). Each line is connected on one end to a maneuvering winch. Line (26) connects to winch (29), line (25) connects to winch (30) line (28) connected to winch (23). The other end of each line connects to the object at sea (1000). It should be noted that if the fourth line (33) is used, it would be connected to a maneuvering winch (31). Each winch is disposed in a load supporting column. Winch (23) is in column (17), winch (29) is in column (19), winch (30) is in column (16) and optional winch (31) is in column (14).
A controller (130) for orienting the catamaran relative to the object at sea (1000) is electrically connected to the winches and the motion compensation systems. The controller monitors the tension on the maneuvering lines and the controller initiates winch pay out of the maneuvering line when load on any one of the maneuvering lines exceeds a first preset limit. The controller initiates the maneuvering winch tensioning of the maneuvering lines when tension or any one of the maneuvering lines falls below a second preset limit. -
All winches are used to reduce the relative motion between the two bodies. When the bodies move away from each other, the winches go to a high preset tension. When the bodies move towards each other, the winches go to a low preset tension.
The vessel can include a propulsion system. However, this vessel may be propulsion-less, and simply be towable and work within the scope of the invention for lifting, transport and maintenance of objects at sea.
FIG 9 shows one embodiment of a propulsion system usable on the vessel. A mirror image for the port side of the vessel is contemplated for this propulsion system. This starboard side has a first engine (37) in the first submersible float (8) driving a first rotatable propeller (38). A second engine is the second hull for driving a second rotatable propeller also disposed on the stern of the second hull.
The propulsion system can optionally comprises a first bow thruster (42) disposed in the bow of the first hull (8) connected to the propulsion system, and a second bow thruster (44) disposed in the hull connected to the propulsion system. Returning to FIG 7, another embodiment contemplates that the propulsion system further can comprises a first stern thruster (46) disposed in hull (10) connected to the propulsion system and a second stern thruster (48) can be disposed in the second hull (8). These two thrusters can be used with the two rotatable propellers previously described. In still another embodiment, two stern thrusters can be used in each hull. Figure 7 shows the 4 stern thruster embodiment with the additional stern thrusters noted at 46a and 48a. Essentially, the catamaran can comprise a propulsion system consisting of a plurality of bow and stern thrusters.
The present invention is contemplated to include one or more load supporting hatches. The support surface (12) can comprises at least one removable hatch. In a preferred embodiment, the hatch can float. FIG 1 shows removable hatch (21, 152, 154 and 156) disposed over the opening slot (15).
In a safety mode for moving the catamaran, it is contemplated that the removable hatch can be placed between the bows of the first and second hulls to prevent water from coming over the solid support surface (12). FIG 10 shows the hatch 21 disposed across the bows of the vessel.
The vessel can either place a topsides or remove a topsides, jacket or similar structure. FIG 11 shows one of the lifting embodiments for the vessel, which can be used to lift a small structure from a jacket. In this embodiment, a hatch (21) is disposed over the two load support columns (16) and (14) for carrying a load (400) using the two winches and two motion compensation systems and the vertical compensation system previously described. Other lifting devices can also be used, such as an A-frame, a gantry, or a crane.
The invention relates to a method for installing topsides to form an offshore platform, with the topside initially at a wharf and then at an intended installation at a location remote from the topside.
Initially, the method comprises a series of steps, which can include placing a topside on a transport wagon; rolling the transport wagon onto a barge and positioning the topsides on the barge wherein a portion of the topsides extends out over opposing sides of the barge.
Next, topsides support structures can be placed on the barge. The topsides are then lowered onto topside support structures enabling the wagon to be rolled from under the topsides and off of the barge.
The barge is then moved near to a submersible catamaran comprising a bow (4) and a stern (6) as shown in FIG 1.
FIG 22 shows some of the features of the method for lifting and transporting a topsides.
FIG 22 shows a topsides already placed on a barge. In a preferred method, the first step consists of: placing a topsides (301) on a barge (302). The barge (302) is then maneuvered near the catamaran (2). The catamaran has positioned the first and second moveable columns (14) and (16) at the stern of the vessel opposite the opening slot (15). Two additional moveable columns, not viewable with this FIG, are disposed in front of the first and second columns, forming a four-column square or rectangle around the slot opening (15).
One or more removable hatches are taken off of a position covering the opening slot (15) thereby forming an unobstructed opening and placed on the solid support surface (12). Each of the four corners of a hatch is connected to the vertical positioning system lines and winches disposed in each of the columns. Here lines (134 and 136) are only viewable, but it is contemplated that all four lines are used. The catamaran is then ballasted to a position below the water's surface (303).
The barge (302) is sailed into the opening over the hatch (21).
The first and second ballast systems are then used to raise the catamaran with respect to the waterline. The base of the topsides is positioned over the tops of the four load supporting moveable columns (14,16,17,19).
The vertical positioning system used for this method is essentially a securing system for securing the catamaran to a topsides or other object, and it comprises:(i) tensioning lines; (ii) a winch; (iii) a motion compensation system disposed in each load supporting moveable column.
A control means is used to enable the securing systems to cooperatively tension the lines.
The catamaran is then raised further, enough to transfer load from the barge to the load supporting moveable columns. The hatch (21) is then lowered with the securing system without the topsides. The catamaran is then lowered permitting the barge to float freely.
The barge is then sailed away from the catamaran.
The catamaran then transports the topsides either at normal draft or in a semi-submersed state to minimize motions on the catamaran.
FIG 23 shows the catamaran transporting the topsides (301) while at a semi-submerged draft.
An alternative embodiment of this invention, involves moving the topsides using a wagon onto the barge, keeping the topsides on the wagon, and removing the topsides from the wagon onto the catamaran.
The method can also comprise using an element between said topsides and the topsides supporting moveable columns to dampen movement between the topsides and the catamaran. The element can be a rubber disc or elastomeric material.
In an embodiment, there can be between 4 and 16 lines used in conjunction with the line of the motion compensators.
It is contemplated that a barge with subsea equipment such as subsea hoisting systems, moorings, suction piles can be sailed onto the support surface (12) while the catamaran is submerged, then the catamaran can be raised and the barge can be supported on the support surface (12).

Claims

Method for lifting, lowering and transporting an object at sea (301; 1000), e.g. from a barge to an installation site, wherein use is made of a catamaran (2), comprising:
• a first hull (8) and a second hull (10) disposed in a parallel spaced relation to said first hull (8), each hull having a hull bow (50;52), a hull midsection (54;56), a hull stern section (58;60) and a hull stern (62;64);

• a support surface (12) forming the top of said first and second hulls, wherein said support surface is adapted for supporting heavy loads and wherein an air gap (13) is present between said first and second hulls and said support surface and wherein a slot opening (15) is present between the stern sections of said first and second hulls;
characterized by
• a first load supporting moveable column (14) being disposed on said support surface; a second load supporting moveable column (16) also being disposed on said support surface;

• a first ballast system (34) being associated with said first hull; a second ballast system (35) being associated with said second hull, wherein said first and second ballast systems are adapted to raise and lower said catamaran with respect to the waterline;

• a first and a second motion compensating and securing system (77;134;135;79;80;138;200) in the first and second load supporting columns (14;16) respectively, for securing the catamaran to the object at sea, wherein each system comprises:
i) a tensioner (77);

ii) a tensioning line (134;135) connected to the tensioner and to the object at sea;

iii) a tension-measuring device (79) connected to said tensioning line;

iv) a motion control device (80) connected to said tensioning line and tensioner for monitoring and controlling tension on said tensioning line.
Method according to claim 1, comprising the steps of:
a. placing the object, e.g. a topsides (301), onto a barge (302);

b. manoeuvring the barge near the catamaran (2);

c. submerging the catamaran using the ballasting system;

d. manoeuvring the barge between the first and second load supporting columns;

e. damping the relative motion between barge and catamaran using the motion compensating and securing system;

f. raising the catamaran enough to transfer the load of the object from the barge to the load supporting columns;

g. floating the barge away from the catamaran.
Method according to claim 1 or 2, comprising the steps of:
a. placing the topsides on a wagon;

b. driving the topsides onto a barge;

c. manoeuvring the barge to a position near a catamaran;

d. submerging the catamaran;

e. manoeuvring the barge over the catamaran and between the first and second load supporting columns,

f. raising the catamaran enough to transfer load from the barge to the load supporting columns;

g. removing the barge.
Method according to any of the previous claims, wherein, once the catamaran has moved to an installation site, the method comprises the additional steps:
a: positioning the catamaran over the installation site;

b. ballasting the catamaran to transfer the topsides onto the installation site; and

c. moving the catamaran away from the installation site using a draft which is deeper than a normal draft for the vessel.
Method according to any of the previous claims, wherein, once the catamaran has moved to an installation site, the method comprises the additional steps:
a. positioning the catamaran over the installation site;

b. damping the relative motion using the motion compensating and securing system and ballasting the catamaran to lower the topsides over the installation site;

c. transferring load to the installation site from the load supporting columns; and

d. moving the catamaran away from the installation site using a draft, which is deeper than a normal draft for the vessel.
Method according to any of the previous claims, wherein use is made of a catamaran (2):
• wherein the support surface comprises at least two floatable hatches, wherein said hatches are adapted for supporting heavy loads;

• further comprising a first and a second load supporting movable columns and each load supporting column having a winching system disposed on said first hull; a third and fourth load supporting movable column and each load supporting column having a winching system disposed on said second hull;

• further comprising a horizontal positioning system comprising:
- at least three horizontal manoeuvring winches,

- at least three lines each connected on one end to a winch and on the other end to an object at sea,

- a controller for orienting the catamaran relative to said object at sea, wherein said controller monitors the tension on said at least three lines and initiates winch pay out of lines when load on any one of said lines exceeds a first preset limit, and further said controller initiates winch tensioning of a line when tension on any one of said lines falls below a second preset limit.
Method according to claim 6, for installing a topsides to form an offshore platform, with the topside initially at a wharf and an intended installation site at a location remote from the topside initially, the method comprising the steps of:
a. placing a topside on a transport wagon;

b. rolling the transport wagon onto a barge and positioning the topsides on the barge wherein a portion of the topsides extends out over opposing sides of the barge;

c. moving the barge to a catamaran;

d. using one of said two floatable hatches to form a first base between said first and third load supporting movable columns and using the other of said two floatable hatches to form a second base between said second and third load supporting columns, connecting said first base to the winching system of said first load supporting column and said third load supporting column, and connecting said second base to the winching systems of said second load supporting column and said fourth load supporting column;

e. lowering the catamaran below the water line;

f. manoeuvring the barge over the first and second base;

g. raising said first and second base using said winching systems lifting the barge to synchronise the barge movements with the catamaran;

h. partially deballasting the catamaran raising it until the topsides on the transport wagon touch the top of the first, second, third and fourth load supporting columns;

i. transferring load of the topsides from the barge to the catamaran;

j. lowering the first and second base thereby lowering the barge;

k. removing the barge from a position over the catamaran;

l. moving the catamaran to an intended installation site;

m. manoeuvring the catamaran to that the intended installations site is contained within the slot opening;

n. ballasting and lowering the catamaran in the water, until the topsides touch supports of the intended installation site;

o. transferring load from the catamaran to the intended installation site.
Method according to claim 7, further comprising the step of using the motion compensating and securing system to secure the catamaran to the intended installation site prior to deballasting and lowering the catamaran with the topsides.
Method according to any of the previous claims, further comprising using an element between said topsides and said load supporting columns to dampen movement between the topsides and the catamaran, e. g. a rubber disc or an element of an elastomeric material.
Method according to any of the previous claims, further comprising using the step of between 4 and 16 tensioning lines connected to the motion compensating and securing system to synchronise the movements of the catamaran and the barge or installation site when lifting the topsides from a barge or lowering the topsides onto the installation site.
Method according to any of the previous claims, wherein an intended installation site is a floating platform.
Method according to any of the previous claims, wherein an intended installation site is a fixed leg platform.
Method according to any of the previous claims, wherein said catamaran is operated at a depth selected from the group:
a normal draft, a slightly submerged draft, wherein water fills the air gap between the first and second hulls and the support surface is above the water level, and a lower draft, wherein between 1 and 20 meters of water covers the support surface.
Method according to any of the previous claims; wherein the topsides extends beyond the hulls of the catamaran.
Method according to any of the previous claims, wherein the catamaran is used in a semi-submerged state to transport the topsides and minimize motions on the catamaran.