The present invention relates to a variable-draught barge, and to a system and method of transferring loads from the barge to a supporting structure in a body of water. More specifically, the present invention relates to a system and method of transferring a platform superstructure (typically a module, integrated deck, etc.) from a barge to a supporting structure in a body of water.

BACKGROUND ART

Platform modules are normally transported and installed in a body of water using vessels equipped with lifting systems. These systems call for the use of high- cost equipment, involve considerable risk by having to lift extremely heavy platform modules, and are seriously limited by environmental (sea bed, sea, and weather) conditions .

A so-called ^A float-over' technique has recently been developed whereby a barge is used to support at least one platform module. The barge is moved into position between the legs of the supporting structure in a body of water. And the platform module is then moved vertically by the combined operation of mechanical devices (heavy-duty hydraulic jacks) , and by adjusting the ballast (draught) of the barge.

The barge is fixed to the supporting structure by a known mooring system for limiting horizontal movement of the barge .

This type of mooring ^' system, however, fails to limit vertical movement of the barge, which for the most part is uncontrollable and dependent on water and weather conditions.

Vertical movement of the barge makes it difficult to connect the platform module to the supporting structure, and to detach the barge completely from the platform. At the connecting stage, vertical movement of the barge may result -in the platform module colliding with the supporting structure, thus impairing connection and possibly also damaging both.

As it is being detached, on the other hand, vertical movement of the barge may cause it to impact the installed platform module.

Research into the forces involved at the connecting and detaching stages shows the difficulties posed, mostly in areas with typically unpredictable water conditions, can be overcome by carrying out the connecting and detaching stages as fast as possible.

One known system for transferring a platform module from a barge to a supporting structure in a body of water is described in document US 6027287 filed by the present Applicant. This system is relatively fast at the connecting and detaching stages, but is unacceptably slow in emergency reversing situations.

Other similar methods are described in documents EP0097069, US 5403124, US 5522680, US 6293734, US 6347909 and US 6981823, and more recently in documents WO 2010098898 and WO 2011028568.

DISCLOSURE OF INVENTION

It is therefore an object of the present invention to provide a variable-draught barge for use in a system for transferring loads from the barge to a supporting structure in a body of water, and designed to eliminate the drawbacks of the known art .

According to the present invention, there is provided a variable-draught barge for transferring loads in a body of water, and having a water line which is a function of the draught; the barge comprising:

- a hull;

- an underbody;

- at least one first chamber located in the hull and selectively floodable to alter the draught of the barge ;

- at least one flood valve located below the water line to flood the first chamber; and - a control device designed to selectively open the flood valve to flood the first chamber.

Using a flood valve below the water line of the barge, the barge chamber is flooded rapidly, thus rapidly altering the draught as required, and so minimizing the time taken to connect the load to the supporting structure, which is a highly critical stage that must be performed as fast as possible.

By virtue of the present invention, the time taken to connect the load to the supporting structure is in the region of a few minutes, which is fast enough to perform the operation to a certain degree of precision, while at the same time preventing collision between the parts and an increase in the potentially damaging forces exchanged between the load and the supporting structure.

The barge according to the present invention is also cheaper and simpler in design than known solutions based exclusively on the use of pump systems for altering the draught, which makes connecting the load to the supporting structure much slower and therefore much more hazardous .

In a preferred embodiment of the present invention, the flood valve is located along the underbody. This way, as soon as the flood valve opens, water flows immediately into the barge to fill the first chamber faster . In a preferred embodiment of the present invention, the flood valve is a throttle valve. Throttle valves are reliable, easy to control and maintain, and allow a large flow passage.

In a preferred embodiment of the present invention, the flood valve is a gate valve. Gate valves are reliable, and allow a large flow passage.

In a preferred embodiment of the present invention, the flood valve is over 0.5 m, and preferably 0.8 to 1.2 m, in diameter.. The large diameter of the flood valve allows large amounts of water to be fed into the barge, to fill the barge chambers, and so increase draught, faster.

In a preferred embodiment of the present invention, the barge comprises at least one second chamber floodable selectively and located at a higher level than the first chamber; and at least one pump to transfer water from the first chamber to the second chamber.

In other words, opening the flood valve only provides for fast filling the first chamber, whereas the second chamber is filled by a pump transfer system. Transferring water from the first chamber to the second chamber allows the first chamber to be flooded again, to further increase the draught of the barge, by simply opening the flood valve.

In a preferred embodiment of the present invention, the second chamber is adjacent to, and preferably over, the first chamber.

This simplifies transferring water from the first chamber to the second by minimizing the distance between them.

In ^" a preferred embodiment of the present invention, the barge comprises a plurality of first chambers connected to one another by connecting openings.

This way, opening the flood valve floods the first chambers evenly, to avoid rocking the barge, and so keeping the barge stable when altering the draught.

In a preferred embodiment of the present invention, the barge comprises a plurality of first chambers; and at least a first tunnel connecting the body of water to at least one first chamber of the plurality of first chambers; the flood valve communicating fluidically with the first tunnel.

This way, opening the flood valve immediately floods the tunnel, and then the first chambers connected to it.

The presence of the tunnel prevents any malfunctioning of the flood valve from accidentally flooding the first chambers unevenly and so bringing about a potentially hazardous alteration in the draught of the barge .

In which case, uncommanded opening of the flood valve only fills the tunnel, with no serious alteration in the draught of the barge .

Above all, the tunnel provides for more evenly flooding the first chambers connected to it, to avoid rocking the barge, and so keeping the barge . stable when altering the draught.

In a preferred embodiment, the first chamber is connected to the first tunnel by means of at least one feed valve,- the control device being designed to selectively open and close the feed valve.

This way, flooding of the first chamber connected to the tunnel is controlled by the control device, to further ensure against accidental flooding of the first chamber .

In a preferred embodiment, the barge comprises a second tunnel which communicates with a further first chamber of the ^■ plurality of first . chambers .

The ^" second tunnel solution allows more first chambers to be catered to than the one- tunnel solution.

In a preferred embodiment of the present invention, the second chamber has at least one fast-drain device connecting the second chamber to the outside of the barge .

This way, when the second chamber is flooded, the draught of the barge can be reduced rapidly by simply activating the fast-drain device. In a preferred embodiment of the present invention, the fast-drain device comprises a fast-drain valve designed to drain the second chamber when the fast-drain valve is above the water line.

This way, simply opening the drain valve drains the water from the second chamber with no need for extraction means, the outflow of water being generated by the difference in pressure between the inside of the second chamber and the outside (above the water line) .

Another object of the present invention is to provide a system for transferring a load from a barge to a supporting structure in a body of water, which is faster than known systems in transferring the load, while at the same time being cheap and easy to produce.

According to the present invention, there is provided a system for transferring loads from a barge to a supporting structure in a body of water, as claimed in Claim 20.

This way, the inner, chambers on the barge can be flooded rapidly to connect the load quickly to the supporting structure.

Another object of the present invention is to provide a method of transferring loads from a barge to a supporting structure in a body of water, which is simple and faster than known methods in transferring the load.

According to the present invention, there is provided a method of transferring loads from a barge to a supporting structure in a body of water; the barge having a water line which is a function of the draught, and comprising a hull, an underbody, at least one first chamber located in the hull and floodable selectively to alter the draught of the barge, at least one flood valve located below the water line to flood the first chamber, and a control device designed to selectively open the flood valve to flood the first chamber; the supporting structure resting on the bed of a body of water, and having at least one supporting member connectable to the load; the method comprising the steps of :

- moving the barge, supporting a load with at least one coupling member, into a transfer position, in which the coupling member on the load is substantially aligned with the supporting member of the supporting structure;

- increasing the draught of the barge by flooding at least the first chamber, so as to bring the coupling member of the load into contact with the supporting member of the supporting structure, and completely transfer the load from the barge to the supporting structure; and

- moving the barge from the transfer position;

wherein the step of increasing the draught of the barge comprises opening the flood valve to flood at least the first chamber. This way, the method according to the present invention ensures the draught of the barge is increased, and consequently the load is connected and transferred from the barge to the supporting, structure,, quickly and reliably.

Simply opening the flood valve, in fact, rapidly increases the draught of the barge .

This therefore minimizes the time taken to connect the load to the supporting structure, which is a highly critical stage that must be performed as fast as possible .

Using the method. according to the present invention, the time taken to connect the load to the supporting structure is in the region of a few minutes.

In a preferred variation of the method according to the present invention, the barge comprises at least one second chamber floodable selectively and at a higher level than the first chamber; and at least one pump for transferring water from the first chamber to the second chamber; the step of increasing the draught of the barge comprising the steps of:

- flooding at least the first chamber; and

- feeding the water in the first chamber to at least the second chamber by means of at least one pump.

In other words, opening the flood valve only provides for fast filling the first chamber, whereas the second chamber is f illed by a pump transfer system . Transferring water f rom the f irst chamber to the second allows the f irst chamber to be f looded again .

In a preferred variation of the method according to the present invention, the · step of increasing the draught of the barge also comprises the step of f looding at least the f irst chamber again, af ter the water in the f irst chamber is transferred to the second chamber .

This way, simply opening the f lood valve further increases the draught of the barge by allowing the f irst chamber to be flooded again .

In one variation, the method according to the present invention also comprises the step of reducing the draught of the barge by draining the second chamber by means of a fast-drain device .

This enables connection of the load to the supporting structure to be reversed. That is, draining the second chamber brings about a reduction in draught, that is potentially vital to recover the load in an emergency.

In a variation of the method according to the present invention, the step of draining the second chamber comprises the step of opening at least one fast -drain valve of the second chamber when the fast-drain valve is above the water line.

This way , simply opening the drain valve drains the water from the second chamber with no need for extraction means , the outf low of water being generated by the difference in pressure between the inside of the second chamber and the outside (above the water line) .

BRIEF DESCRIPTION OF THE DRAWINGS

A non- limiting embodiment of the present invention will be described by way of example with reference to the attached drawings, in which :

Figure 1 shows a view in perspective, and in a first operating position, of the system for transferring a load from a barge to a supporting structure in a body of water according to the present invention;

Figure 2 shows a partly sectioned side view, with parts removed for clarity, of the Figure 1 system;

Figure 3 shows a partly sectioned side view, with parts removed for clarity, of the Figure 1 system in a second operating position;

Figure 4 shows a partly sectioned side view, with parts removed for clarity, of - the Figure 1 system in a third operating position;

Figure 5 shows a partly sectioned side view, with parts removed for clarity, of the Figure 1 system in a fourth operating position;

Figure 6 shows a partly sectioned side view, with parts removed for clarity, of the Figure 1 system in a fifth operating position;

Figure 7 shows a partly sectioned side view, with parts removed for clarity, of the Figure 1 system in a sixth operating position;

Figure 8 shows a partly sectioned top plan view, with parts removed for clarity, of a first detail of the Figure 1 system;

Figure 9 shows a partly sectioned side view, with parts removed for clarity, of the first detail in Figure 8;

Figure 10 shows a partly sectioned side view, with parts removed for clarity, of a second detail of the system for transferring a load from a barge to a supporting structure in a body of water according to the present invention;

Figure 11 shows a front view of a third detail of a variation of the system according to the present invention;

Figures 12-16 show larger-scale, partly sectioned front views, with parts removed for clarity, of a detail of the system according to the present invention in the Figure 2 and 4-7 operating positions respectively.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in Figure 1 indicates a system for transferring a load from a barge to a supporting structure in a body of water in accordance with the present invention.

System 1 comprises a barge 2 supporting a load 3 ; and a supporting structure 4 resting on the bed .5 of a body of water 6.

More specifically, load 3 is supported on barge 2 so as to project at least partly from barge 2.

In the non-limiting example described and, illustrated herein, load 3 is a top module of an underwater well drilling and/or hydrocarbon extraction platform. The module may .be used in general for any offshore function, not necessarily relating to hydrocarbons, such as wind- related functions.

Module 3 has at least one deck 8 with a top face 9 and a bottom face 10.

A drilling rig 11 is located on one side of top face 9 of deck 8. Close to drilling rig 11, there is a further deck 12 which serves as a heliport. Module 3 also comprises at least one crane 13 located on deck 8, on the opposite side of drilling rig 11 to deck 12.

Module 3 also comprises miscellaneous tooling and devices, engine rooms, and living quarters not shown in the drawings .

As shown in Figure 2, module 3 has at least four coupling members 14 (only two shown in Figure 2) projecting from bottom face 10 of deck 8.

In the non- limiting example described and illustrated herein, coupling members 14 are defined by pylons .

Pylons 14 are preferably eight in number, and located at the corners of two substantially aligned quadrilaterals .

Pylons 14 are preferably substantially perpendicular to bottom face 10.

Each pylon 14 is preferably substantially cylindrical, and has one end 15 connected to bottom face 10; and one end 16, which has a recess 17 (shown more clearly in Figure 12) defining a coupling seat.

Recess 17 is preferably conical or truncated-cone- shaped.

With reference to Figures 1 and 2, supporting structure 4 comprises two legs 20 resting on and fixed to bed 5 of body of water 6.

In the attached drawings, legs 20 are defined by lattice structures, but may be defined by tubular or other types of structures. Each leg 20 extends along an axis A, and has a base portion 21 fixed to bed 5 of body of water 6; and an end portion 22 designed to fix to module 3.

More specifically, end portion 22 of each leg 20 has at least two supporting members 23.

In the non- limiting example described and illustrated herein, each end portion comprises four supporting members 23 located at the corners of a quadrilatex-al .

Each supporting member 23 preferably has a pointed end 24 designed to engage recess 17 of respective pylon 14 of module 3 (Figure 12) .

Barge 2 extends substantially along a plane perpendicular to axis A, and comprises a hull 18a designed to float in a body of water 6, with a water line L.

Water line L defines underbody 18b constituting the immersed part of hull 18a.

Barge 2 comprises a plurality of supports 25 (Figure 2) for supporting load 3 during transport and when transferring load 3 from barge 2 to supporting structure 4. Supports 25 are preferably lattice- structured. In variations not shown, supports 25 may be defined by tubular or other types of structures.

Barge 2 is preferably not self-propelled, and is towed when required.

With reference to Figure 8, hull 18a (Figure 2) has two longitudinal partitions 26 extending from stern to bow; and a plurality of transverse partitions 27 substantially perpendicular to longitudinal partitions 26.

Longitudinal partitions 26 and transverse partitions 27 define a plurality of airtight chambers 28. The chambers of the plurality of chambers 28 can be selectively flooded or drained independently of one another, to achieve a given draught when transferring load 3 from barge 2 to supporting structure 4.

With reference to Figure 9, barge 2 has an intermediate deck 29, which divides the chambers of the plurality of chambers 28 arranged at the centre of barge 2 into upper and lower portions.

In the non- limiting example described and illustrated herein, the plurality of chambers 28 comprises nine fore chambers 30, nine aft chambers 31, six upper intermediate chambers 32, and six lower intermediate chambers 33.

Barge 2 also has two tunnels 35a, 35b extending along the centre bottom of barge 2 and communicating with lower intermediate chambers 33. Tunnels 35a, 35b preferably extend crosswise to each other in the form of a cross. In the non-limiting example described and illustrated herein, tunnels 35a, 35b are perpendicular to each other.

Barge 2 also comprises a plurality of flood valves 36 located along underbody 18b (Figure 2) , beneath water line L, and interposed between body of water 6 and one or more lower intermediate chambers 33.

Flood valves 36 are controlled by a control device (not shown in the drawings for the sake of simplicity) designed to selectively open flood valves 36 to flood respective lower intermediate chambers 33.

In the non-limiting example described and illustrated herein, flood valves 36 communicate fluidically with tunnels 35a, 35b, and are designed to flood tunnels 35a, 35b when opened.

Tunnels 35a, 35b communicate with _. lower intermediate chambers 33 via respective feed valves 37 (only one shown in Figure 10) .

Feed valves 37 are controlled by the control device, which is designed to selectively open feed valves 37 to flood respective lower intermediate chambers 33 with water from tunnels 35a, 35b.

In other words, tunnels 35a, 35b are dedicated to flooding lower intermediate chambers 33.

In actual use, opening flood valves 36 floods tunnels 35a, 35b, and subsequently opening feed valves 37 floods lower intermediate chambers 33.

Flood valves 36 are preferably large- section throttle valves.

In the non- limiting example described and illustrated herein, flood valves 36 are over 0.5 m, and preferably 0.8 to 1.2 m, in diameter.

Flood valves 36 being located below water line L, water flow from body of water 6 into tunnels 35a, 35b is generated by pressure difference, with no need for pumps .

In one variation, flood valves 36 are gate valves, as shown in Figure 11. In another variation, not shown, flood valves 36 are ball valves .

Feed valves 37 are preferably large-section throttle valves.

In the non- limiting example described and illustrated herein, feed valves 37 are over 0.5 m, and preferably 0.8 to 1.2 m, in diameter.

In one variation, feed valves 37 are ball valves.

In another variation, feed valves 37 are gate valves .

In one variation not shown, barge 2 has no tunnels 35a, 35b, and lower intermediate chambers 33 are connected directly to body of water 6 by respective flood valves. In the absence -of tunnels 35a, 35b, the six lower intermediate chambers 33 are connected -to one another by connecting openings along partition 27 and partitions 26 (Figures 8 and 9) . This provides for fast, even flooding of lower intermediate chambers 33, and therefore greater stability of barge 2.

With reference to Figure 10, upper intermediate chambers 32 and lower intermediate chambers 33 are connected to one another by one or more fluidic, preferably centrifugal, pumps 38 for pumping water from lower intermediate chambers 33 to upper intermediate chambers 32.

In the non-limiting example described and illustrated herein, each lower intermediate chamber 33 has a pump 38 for feeding water to the adjacent upper intermediate chamber 32-.

In one variation not shown, one centrifugal pump is able to pump water from a plurality of lower intermediate chambers 33 to a plurality of upper intermediate chambers 32 simultaneously.

In another variation not shown, an extraction system comprises one centrifugal pump; a plurality of extraction lines; and control means for selectively drawing water from selected lower intermediate chambers 33 to selected upper intermediate chambers 32.

With reference to Figure 10, upper intermediate chambers 32 have respective fast-drain valves 42 connecting them directly to the outside, and which, when above water line L, provide for draining upper intermediate chambers 32.

Fast-drain valves 42 are preferably throttle valves .

Each fast-drain valve 42 is controlled by the control device (not shown in the drawings for the sake of simplicity) .

Draining upper intermediate chambers 32 rapidly reduces the draught of barge 2.

Each fast-drain valve 42 is preferably located on the wall separating the respective upper intermediate chamber 32 from the outside.

For maximum drainage, the fast-drain valve 42 is preferably located, on said wall, close to the bottom of respective upper intermediate chamber 32.

As explained in detail below, opening fast-drain valves 42 is extremely useful for emergency recovery of load 3 during transfer.

Finally, barge 2 comprises a conventional auxiliary hydraulic circuit (not shown in the attached drawings) for selectively feeding water to, and selectively draining, fore chambers 30 and aft chambers 31.

The auxiliary hydraulic circuit preferably comprises a plurality of centrifugal pumps for drawing water from body of water 6, and feeding it directly to fore chambers 30 and aft chambers 31.

In the non- limiting example described and illustrated herein, the -auxiliary hydraulic circuit is designed to selectively draw water from body of water 6 and feed it directly to lower intex-mediate chambers 33 and possibly also to upper intermediate chambers 32, and to drain lower intermediate chambers 33 and possibly also upper intermediate chambers 32.

In one variation not shown, the auxiliary hydraulic circuit does not cater to lower intermediate chambers 33 and upper intermediate chambers 32.

In another variation not shown, barge 2 has a mechanical system for assisting connection of load 3 to supporting- structure 4. The mechanical system may, for example, comprise heavy-duty hydraulic jacks for connecting and detaching the load faster.

With reference to Figures 2-7, the method of transferring load 3 from barge 2 to supporting structure 4 in body of water 6 comprises a plurality of operations described in detail later on and substantially performed in the following order ·.

- moving barge 2, supporting load 3, up to supporting structure 4 (Figures 1 and 2) ;

- positioning and mooring barge 2 between legs 20 of supporting structure 4, so that load 3 is a distance Dl of about 1-2 m from supporting structure 4 (Figures 3 and 12) ;

- first connecting load 3 rapidly to supporting structure 4 to transfer a varying percentage of the load, preferably enough to eliminate any relative movement between load 3 and supporting structure 4; in the non- limiting example described and illustrated herein, the load percentage transferred at this stage ranges between 30% and 50% (Figures 4 and 13) ;

- partly transferring the load from 30/50% to 75% (Figures 5 and 14);

- rapidly transferring 100% of the load, and detaching barge 2 from load 3 to a distance D2 of at least 1-2 m between barge 2 and load 3 (Figures 6 and 15) ;

- moving barge 2 .clear of supporting structure 4 (as shown by the dash lines in ^" Figure 7) ..

The partial load transfer step (from 30/50% to 75%) is optional.

The load may, in fact, be substantially transferred in two steps : the fast connecting step, in which a varying percentage of the load is transferred to prevent any relative movement between load 3 and supporting structure 4; and the full load transfer step.

More specifically, barge 2 is moved up to supporting structure 4 by tow. In the non- limiting example described herein, in fact, barge 2 is not self- propelled.

In a variation not shown, barge 2 is self- propelled .

To adjust the attitude of barge as it is being transported, some of the plurality of chambers 28 on barge 2 are fully or partly flooded with water. In the non- limiting example shown in Figure 2, at least three fore chambers 30 and one aft chamber 31 are fully or partly flooded to ensure a stable attitude of barge 2. The step of flooding the three fore chambers 30 and one aft chamber 31 is performed by the auxiliary hydraulic circuit . Once positioned between legs 20 of supporting structure 4, barge 2 is moored to legs 20 by mooring lines, .and possibly also with the aid of commonly used horizontal motion suppressing means (not shown) such as elastic mechanical abutting elements (pistons) or bumpers ( 'ocean cushions' ) .

When positioned between legs 20 of supporting structure 4, barge 2 must be immersed in body of water 6 so that ends 16 of pylons 14 of load 3 are a distance Dl of about 1-2 metres from ends 24 of supporting members 23 of legs 20 (Figures 2 and 12) .

When transporting, positioning, and mooring the barge, flood valves 36 of tunnels 35a, 35b are closed, and the draught P of barge 2 is roughly 5.5 m, as shown in Figure 12. Here and hereinafter, draught P is intended to mean the substantially vertical distance between the bottom of underbody 18b of barge 2 and water level L (Figure 2) .

With reference to Figure 3, once barge 2 is moored, lower intermediate chambers 33 are flooded with water, and barge 2 is immersed in body of water 6 to reduce distance Dl and bring ends 16 of pylons 14 of load 3 into contact with ends 24 of supporting members 23 of legs 20 (Figure 2) .

Connecting the load is one of the most critical steps in the transfer method according to the present invention, and therefore one that calls for extremely- fast flooding of lower intermediate chambers 33. In the non- limiting example described and illustrated herein, the time taken to bring end 16 of each pylon 14 of load 3 into contact with end 24 of corresponding supporting member 23 of legs 20 is in the region of a few minutes.

More specifically, lower intermediate chambers 33 are flooded by simply opening flood valves 36 located below water line L.

With reference to Figures 4 and 13, by the time the load is connected, lower intermediate chambers 33 are completely flooded to transfer part of load 3 to supporting structure 4 (Figure 4) . In the non- limiting example shown, the percentage of load 3 transferred to supporting structure 4 at this stage ranges between 30% and 50%. This provides for a stable configuration by eliminating any relative movement between load 3 and supporting structure 4.

In the Figure 4 and 13 configuration, flood valves 36 of tunnels 35a, 35b are open, and draught P of barge 2 is around 7.5 m (Figure 13) .

With reference to Figures 5 and 14, upper intermediate chambers 32 are flooded by fluidic pumps 38 (Figure 10) drawing water from lower intermediate chambers 33.

When drawing water from lower intermediate chambers 33, flood valves 36 of tunnels 35a, 35b are closed, and draught P of barge 2 remains unchanged at about 7.5 m (Figure 14) .

In an emergency (such as a sudden change in weather conditions) , upper intermediate chambers 32 can be drained rapidly by opening fast-drain valves 42 (Figure 10). This causes rapid emersion of barge 2, and load 3 is transferred back to barge 2.

The time taken to fill upper intermediate chambers 32 is in the region of a few hours. Since load 3 has already been connected to supporting structure 4, the ballast water is transferred by fluidic pumps 38 (Figure 10) from lower intermediate chambers 33 to upper intermediate chambers 32 in a stable, reversible configuration.

With reference to Figures 6 and 15, once upper intermediate chambers 32 are filled, lower intermediate chambers 33 may be partly filled to increase draught P of barge 2 and assist transferring from 50% to roughly 75% of load 3 to supporting structure 4.

At this stage, lower intermediate chambers 32 may be filled partly by the auxiliary hydraulic circuit, if provided .

In this configuration, draught P of the barge increases to around 8.5 m, as shown in Figure 15. As lower intermediate chambers 33 fill up, load 3 begins detaching from barge 2.

With reference to Figure 7, lower intermediate chambers 33 are filled completely to increase draught P of barge 2 to around 9.5 m, as shown in Figure 16. Draught P must be increased to produce a distance D2 of about 1-2 metres between supports 25 of barge 2 and bottom face 10 of deck 8 of load 3. Distance D2 must be sufficient to allow barge 2 to exit the transfer position without touching load 3.

Final filling of lower intermediate chambers 33 is performed rapidly, in the space of a few minutes, thus safeguarding against surge- induced collision.

At this stage, filling lower intermediate chambers 33 necessarily calls for opening flood valves 36.

The dash lines in Figure 7 indicate barge 2 exiting from the transfer position.

It is understood that all the steps in the method described above may comprise controlled flooding or draining of fore chambers 30 and aft chambers 31 to adjust the draught or simply the attitude of barge 2.

Clearly, changes may be made to the barge and to the system and method of transferring a load from a barge to a supporting structure in a body of water, as described herein, without, however, departing from the scope of the accompanying Claims .