WO2009136064A1

WO2009136064A1 - Device for extracting a material situated at the bottom of an expanse of water, extraction installation and associated method

Info

Publication number: WO2009136064A1
Application number: PCT/FR2009/050599
Authority: WO
Inventors: Philippe Espinasse
Original assignee: Technip France
Priority date: 2008-04-08
Filing date: 2009-04-07
Publication date: 2009-11-12
Also published as: MX2010011122A; FR2929638B1; PT2288789T; EP2288789B1; JP2011520046A; BRPI0911059B1; BRPI0911059A2; EP2288789A1; DK2288789T3; FR2929638A1; JP5390593B2; NZ588463A

Abstract

This device comprises a bottom assembly (24) comprising means (50, 52) of gathering material from the bottom (14) of the expanse of water (12) and a pipe (26) for transporting the gathered material, the pipe being connected at a first point (60) to the bottom assembly (24) and connected at a second point (62) to a surface assembly (20). The bottom assembly (24) comprises means (36) of anchorage into the bottom (14) of the expanse of water (12). The extraction device (18) comprises a buoyancy assembly (28) completely immersed under the expanse of water (12). The buoyancy assembly (28) is secured to at least one upper region of the transport pipe (26) in order to keep the transport pipe (26) in a substantially vertical configuration in the expanse of water (12) between the bottom assembly (24) and the upper region when the second point (62) is disconnected from the surface assembly (20).

Description

Device for extracting material located at the bottom of a body of water, extraction plant, and associated method

The present invention relates to a device for extracting a material situated at the bottom of a body of water, of the type comprising: a bottom assembly comprising means for sampling the material on the bottom of the body of water ;

a pipe for transporting the sampled material, connected at a first point to the bottom assembly and intended to be connected at a second point to a set of floating surfaces on the body of water. Such devices are particularly intended for the mining of submarine bottoms, or the earthworks of submarine soils for the establishment of hydrocarbon production facilities.

FR-A-2 467 283 discloses a device of the aforementioned type. This device comprises a surface installation carried by a ship and a bottom assembly. The bottom assembly comprises a base station and an extraction vehicle traveling on the seabed and connected to the base station by a flexible link designated by the English term "jumper".

To lower the bottom assembly into the water, it is known to use a rigid hollow rod train which connects the base station and the surface installation. The drill string internally delimits a circulation passage of material taken from the bottom to convey it to the surface.

Such a device is therefore satisfactory during normal operation in calm waters of the extraction device.

However, in the event of a storm or when the surface installation on the ship must be temporarily moved, it is necessary to reassemble the entire set of rods constituting the transport pipe in the carrying vessel, as well as the underwater vehicle. sampling material on the bottom of the body of water and pumping equipment.

Such an operation is tedious and slow, which affects the safety and cost of operating the device.

An object of the invention is therefore to obtain a device for extracting a material located at the bottom of a body of water that is safer and less expensive to operate. To this end, the invention relates to a device of the aforementioned type, characterized in that the bottom assembly comprises anchoring means in the bottom of the body of water, the extraction device comprising a set buoyancy device intended to be fully immersed under the body of water, the buoyancy assembly being secured to at least one upper region of the transport pipe to maintain the transport pipe in a substantially vertical configuration within the range of water between the bottom assembly and the upper region when the second point is disconnected from the entire surface.

The device according to the invention may comprise one or more of the following characteristics, taken in isolation or according to any combination (s) technically possible (s):

the buoyancy assembly comprises a plurality of buoys mounted around the upper region of the transport pipe;

- the transport pipe comprises a rigid lower portion connected to the bottom assembly and a flexible upper portion connected to the rigid lower portion, the buoyancy assembly being mounted at least partially on the rigid lower portion;

- The transport pipe is flexible over substantially its entire length to be deployable between a wound configuration on a winding drum carried by the entire surface and a deployed configuration in the body of water;

- The bottom assembly comprises an extractor vehicle connected to the transport pipe, the sampling means being carried by the extractor vehicle; and the bottom assembly comprises a material collection support, connected to the transport pipe, the collection support being intended to be placed on the bottom of the body of water to collect the material collected by means of sampling, the sampling means being intended to be maneuvers from the entire surface, regardless of the collection medium.

The invention also relates to a plant for extracting a material situated at the bottom of a body of water, characterized in that it comprises: a surface assembly intended to extend at least partially above the surface of the body of water;

an extraction device as defined above, the second point of the transport pipe being displaceable with respect to the entire surface between a connected configuration in which the second point is connected to the surface assembly and a disassembled configuration in which the second point is located completely away from the surface assembly, the buoyancy assembly holding the transport pipe in a substantially vertical configuration in the body of water between the bottom assembly and the upper region, in the connected configuration and in the disassembled configuration.

The invention further relates to a method of extracting a material located at the bottom of a body of water using an installation as described above, characterized in that it comprises the following steps : - connection of the second point of the transport duct to the surface assembly;

extraction of the material from the bottom of the body of water by the sampling means;

conveying the extracted material to the entire surface through the transport pipe; then

- disconnecting the second point of the transport pipe away from the entire surface, the buoyancy assembly maintaining the transport pipe in a substantially vertical configuration in the body of water between the bottom assembly and the upper region after disconnection. The method according to the invention may comprise one or more of the following characteristics, taken alone or in any combination (s) technically possible (s):

after the disconnection step, an additional step of connecting the second point of the transport pipe to the surface assembly; and the installation comprises a first vessel and a second vessel, each vessel carrying a surface assembly, the method comprising the following steps: connecting the second point of the transport pipe to the surface assembly of the first vessel;

extraction of the material from the bottom of the body of water by the sampling means, conveying the extracted material to the entire surface of the first vessel through the transport pipe, then

- disconnecting the second point of the transport pipe away from the entire surface of the first vessel, the buoyancy assembly maintaining the transport pipe in a substantially vertical configuration in the body of water between the assembly background and the upper region,

- connecting the second point of the transport pipe to the entire surface of the second vessel.

The invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended drawings, in which:

- Figure 1 is a side view of a first extraction system according to the invention, the surface vessel being connected to the extraction device;

- Figure 2 is a schematic side view of an upper portion of the transport pipe provided with a buoyancy assembly; - Figure 3 is a view similar to Figure 1 when disconnecting the surface vessel;

- Figure 4 is a view similar to Figure 1 in the absence of surface ship;

- Figure 5 is a side view of a detail of the first extraction plant in a contracted position of the flexible upper part of the transport pipe;

- Figure 6 is a view similar to Figure 5 in an extended position of the flexible upper part of the pipe;

Figure 7 is a top view schematically illustrating the configurations of Figure 5 and Figure 6; and

- Figure 8 is a curve showing the window of use of the extraction device of Figures 5 to 7 according to the depth and distance to the vertical axis of the rigid portion. An extraction installation 10 according to the invention is shown in Figures 1 to 4. This installation is intended to collect materials located at the bottom of a body of water 12 such as a sea, an ocean, or a lake.

The body of water 12 rests on a bottom 14 delimited by solid material comprising rocks and / or sediments.

The purpose of the device 10 is to carry out, for example, earthworks on the bottom 14 with a view to setting up a hydrocarbon exploitation facility, or to withdraw ores deposited on the bottom 14 with a view to making them available. Subsequent operation at the surface 16 of the water body 12. As illustrated in FIG. 1, the plant 10 comprises an underwater extraction device 18 and a surface assembly 20 for collecting, treating and storing the water. material removed and raised to the surface by the extraction device 18.

In this example, the entire surface 20 is carried by a ship 22 floating on the body of water.

The extraction device 18 comprises a bottom assembly 24 for taking the material on the bottom 14 of the water body 12, a transport pipe 26 connecting the bottom assembly 24 to the surface assembly 20 and , according to the invention, a buoyancy assembly 28 mounted around at least one upper region of the transport pipe 26 to ensure its maintenance in a substantially vertical configuration in the body of water 12.

The extraction device 18 furthermore comprises functional lines 30 for supplying power to the bottom assembly 24 and for injecting gas into the line 26. The bottom assembly 24 comprises a base station 32, means 34A,

34B excavation, moved relative to the base station 32, and an anchor 36 for fixing the base station 32 on the bottom 14 of the body of water 12.

The base station 32 is intended to be placed in the vicinity of the bottom 14, away from it during the exploitation of the materials. The base station 32 includes equipment (not shown) for pumping and treating the sampled material, such as, for example, pumps or filters, and control means for the excavating means 34A, 34B. It may also comprise means for temporarily storing the material taken by the excavating means 34A, 34B.

In the example shown in FIG. 1, the excavating means 34A, 34B comprise, on the left in the drawing, an excavating vehicle 38 and a flexible link 40 connecting the excavating vehicle 38 to the base station 32, and to the right in the drawing, an excavation crane 42, associated with means 44 for receiving and treating the material, placed on the bottom 14 of the body of water 12 and connected to the base station 32 by a second flexible link 46.

The excavating vehicle 38 is intended to move on the bottom 14 to collect material. It comprises means 48 for autonomous movement on the bottom 14, and means 50 for sampling the material capable of digging, scraping or drilling the material constituting the bottom 14 and transporting it to the flexible link

40.

An example of an excavating vehicle is described in French Application FR-A-2 467 283.

The flexible link 42 is sometimes referred to as the "jumper". It is formed of a hose having an upper end connected to the base station 32 and a lower end connected to the vehicle 38 to take the material from the sampling means 50. It delimits internally a material flow opening opening in view of the sampling means 50 and in the base station 32 to connect to the transport pipe 26.

The crane 42 is deployable and operable from the ship 22 at the surface. It comprises a clip 52 for taking the material on the bottom 14, and a cable 53 for deploying and moving the clip 52 to descend it from the ship 22 towards the bottom 14 and to move it relative to the bottom 14.

Alternatively, the excavating means 34B further comprises a jack hammer secured to the clamp 52 or a jack hammer deployed from the ship 22 at the surface by an additional cable deployment and displacement. The receiving means 44 are described for example in the French application No. 07 56579 of the Applicant. They comprise an adjustable support support 54 placed on the bottom of the body of water, provided with a crusher / crusher and a funnel for receiving the sampled material.

The clamp 52 of the crane 42 is movable relative to the support 54 between a material withdrawal position in contact with the bottom 14 of the expanse of water, and a position of discharge of the material into the support 54.

The second flexible link 46 is of similar structure to that of the first flexible link 40.

The anchor 36 comprises a fixing stud in the bottom of the body of water and a connecting cable to the base station 32. The station 32 is thus held above the fixing stud a few meters to the distance from the bottom 14.

The transport pipe 26 extends substantially vertically in the water body 12 between a first point 60, located at its lower end and connected to the base station 32, and a second point 62 located at its upper end and connected. removably on the surface assembly 20.

The pipe 26 comprises, with reference to FIG. 1, a rigid lower portion 64, a flexible upper portion 66 and a connecting connection 68 between the rigid portion and the flexible portion.

The conveying duct 26 defines internally, over its entire length taken between the first point 60 and the second point 62, an inner continuous circulation lumen 70 of the material, intended to convey the material taken from the bottom 14 of the expanse. water from base station 32 to surface assembly 20.

In the example illustrated in FIG. 1, the rigid lower part 64 comprises an end-to-end connection of sections 72 of rigid metal tubes.

The maximum radius of curvature of the rigid pipe is less than 12 m and in particular less than 10 m.

As will be seen below, and according to the invention, thanks to the buoyancy assembly 28 and the anchor 36, the lower portion 64 extends along an axis AA 'substantially vertical between the connection 68 and the station. base 32 regardless of the configuration of the flexible upper portion 66. The lower portion 64 is further provided with two stiffeners 73 located in the vicinity of the connector 68.

The connector 68 is located at a depth between 1 m and 200 m below the surface 16. The flexible upper portion 66 is made based on a flexible duct 74 having a minimum radius of curvature greater than 12 m.

The flexible upper portion 66 is thus able to deform between an S-connected configuration, in which it is connected to the surface assembly 20, as shown in FIG. 1, and an U-shaped disassembled configuration in which it is disconnected from the surface assembly 20 and extends downwardly parallel to the rigid portion 64, as shown in FIG.

In the S-connected configuration, the second point 62 is maintained connected to the surface assembly 20 above the connector 68. The flexible conduit 74 forms from the connector 68 to the second point 62, an elbow 75A directed upwardly. , a bend 75B directed downwards, then a substantially vertical section 75C.

The flexible upper portion 66 is provided, in the vicinity of the first point 62, with a retrieval cable 80 having a buoy 82 floating at the surface at the upper end of the cable 80.

Alternatively, the flexible upper portion 66 is devoid of cable 80 and buoy 82. The first point 62 is then adapted to rest in the body of water 12 or the bottom 14 of the body of water when is disconnected from the surface assembly 20. The functional lines 30 include power and / or hydraulic power transmission lines 90, and information transport lines for feeding the excavating devices 34A, 34B and the station base 32, and at least one line 92 for injecting gas into the inner lumen 70 of the transport pipe 26 for conveying the material from the base station to the surface assembly 20.

The transport lines 90 are made for example in the form of umbilicals with a free upper section relative to the pipe 26, an intermediate section fixed along the pipe 26 facing the rigid portion 64 and a lower free section with respect to the pipe 26 connecting the intermediate section respectively to the excavating vehicle 38 and to the support 54.

According to the invention, the buoyancy assembly 28 comprises a plurality of buoys 96, 98 distributed axially along the transport pipe 26. As illustrated in FIG. 2, the transport pipe 26 thus comprises a first group of buoys 96 coaxially mounted around the lower portion 64 and a second group of buoys 98 mounted around the flexible upper portion 66.

The buoys 96, 98 are for example made of waterproof foam and are fixed axially around the pipe 26 by means of clamps, as described in patent application GB 2 288 205 of the British company CRP.

In the example shown, the buoys 96, 98 are distributed over substantially the entire length of the pipe 26.

Alternatively, the buoys 96, 98 are arranged only on an upper region of the pipe 26 in the vicinity of the connector 68, defining on the rigid lower portion 64 and on the flexible upper portion 66 regions without buoys 96, 98 of length greater than 50% of the length of line 26.

In this case, the upper region provided with buoys 96, 98 has a buoyancy greater than the buoyancy of the other regions of the pipe 26.

The buoys 96, 98 are sized to maintain the rigid portion 64 substantially vertical in the body of water 12 in compensation for the weight of the pipe 26 and the fluid possibly contained in this pipe, in the case where the second point 62 is connected. to the surface assembly 20 or when the second point 62 is disconnected from the surface assembly 20, in the absence of vertical traction on the second point 62.

The buoys 96, 98 thus exert on the duct 26 an upward force greater than the force resulting from the difference between, on the one hand, the weight of the duct 26 and its contents, and on the other hand, the thrust Archimedes exercising on the conduct 26.

In another variant, the buoyancy assembly 28 comprises a single buoy 96 made from a hollow hull totally immersed in the expanse of water. The single buoy is disposed vertically above the connector 68 and is connected to the connector 68 by a chain.

The surface assembly 20 comprises means 100 for receiving, decanting and treating the material received from the transport pipe 28, means 102 for supplying power and / or hydraulic power and for controlling or excavating means 34A. 34B and means 104 for injecting gas into the line

92.

The assembly and operation of the extraction installation 10 according to the invention will now be described. Initially, the extraction device 18 is assembled sequentially and descended to the bottom 14 of the body of water.

For this purpose, the base station 32 and the excavation means 34A, 34B are progressively lowered towards the bottom 14 of the water body 12 from the vessel 22 by successive assembly of the pipe sections 72 forming the lower part. rigid 64 of the transport pipe 26.

During the mounting of the rigid portion 64, the buoys 96 are mounted regularly around the pipe sections 72 and are wedged axially around these tubes 72 to form the buoyancy assembly 28.

Then, the connector 68 is mounted at the upper end of the rigid lower portion 64. The flexible pipe 74 provided with the buoys 98 is then assembled and lowered into the body of water 12 to form the flexible upper portion 66 of the pipe transport 26, which occupies its configuration connected to the surface assembly 20.

Furthermore, the functional lines 30 are unwound from rotary drums placed on the ship 22 and are lowered simultaneously with the transport pipe 26.

When the base station 32 is located a few meters above the bottom 14 of the body of water 12, the anchor 36 is put in place and its attachment stud is immobilized in the bottom 14 of the extension of 'water. The buoys 96, 98 and the buoyancy assembly 28 generating an upward pulling force on the upper region of the transport pipe 26 provided with the buoys 96, 98, and the anchor 36 generating a holding force of the lower end 60 of the transport pipe 26 near the bottom 14 of the extension water 12, the rigid lower portion 64 of the transport pipe 26 spontaneously aligns and permanently along a substantially vertical axis AA 'between the anchor 36 and the connection 68.

In addition, the flexible upper portion 66 adopts a wave-shaped conformation which absorbs the local displacements of the vessel 20 relative to the rigid portion 64.

The excavation means 34A, 34B are then activated to collect material on the bottom 14 of the water body 12 and to bring the material taken through the respective flexible lines 40, 46 to the base station 32 Then, the sampled material is raised through the inner lumen 70 of the transport pipe 26 between the base station 32 and the reception and processing means 100 on the surface assembly 20, in particular under the effect of the gas. injected by the gas injection line 92 into the lumen 70, and / or by centrifugal pumps mounted on the base station 32 or on the base of the anchor 36. In case of a storm or in an emergency , the first point 62 can be disconnected very quickly from the surface assembly 20 to be placed away from the vessel 22 in the body of water 12, so that the upper portion 66 occupies its disassembled configuration illustrated by the Figure 3

Once disconnected, the ship 22 can quickly move away from the extraction device 18, especially when a storm agitates the body of water 12.

However, even when the second point 62 is disconnected, the transport pipe 26 remains substantially vertical in the body of water 12, in particular in the rigid lower part 64 between the base station 32 and the coupling 68, as illustrated by FIG. Figure 4. On the other hand, when the second point 62 of the pipe is to be reconnected to a surface assembly 20, it can be towed on a ship 22 to the surface 16 via the fishing cable 80 which can be grasped at using the buoy 82.

The extraction device 18 according to the invention can therefore be left permanently immersed in the body of water 12 in a substantially vertical configuration, without having to go up in a ship 22 when not in use. As illustrated by FIGS. 4 to 8, the extraction device 18 according to the invention, when it is equipped with excavation means 34B comprising a crane 42 integral with the ship associated with means 44 for receiving treatment of the laid material on the bottom of the body of water, has a large radius of intervention on the bottom 14 of the body of water, even when the second point 62 is kept connected to the surface assembly 20, and when the anchor 36 is held stationary on the bottom 14 of the body of water.

Thus, with reference to FIG. 7, for each position of the ship 22, the clamp 52 located at the lower end of the crane 42 is adapted to process, in projection on the bottom 14, a disc-shaped surface 130 centered on the ship 22. In addition, the ship 22 can rotate 360 ° about the axis A-A ', allowing a treatment of an annular surface 132 centered on the axis A-A', by correspondingly displacing the support 54 to place it in the disc-shaped surface 130. As illustrated in Figures 5, 6 and 7, the extent of the annular treatment surface 132 about the axis AA 'is defined by the configuration in S of the flexible upper part 66.

Thus, when the flexible upper portion 66 occupies its S-shaped configuration, it is able to be moved by the ship 22 between a radially contracted position, shown in FIG. 5, in which the second point 62 connected to the surface assembly 20 is positioned in the vicinity of the vertical axis AA 'of the rigid lower part 64, and a radially expanded position, shown in FIG. 5, in which the second point 62 is further from the vertical axis AA' of the lower part 64. As shown in FIG. 5, in the radially contracted position, the angle θ formed by a vertical axis BB 'passing through the second point 62 and the upper portion of the flexible upper portion 66 is less than -10 ° and is for example between -15 ° and -20 °.

As shown on the left in FIG. 7, the ship 22 is then placed in the vicinity of the axis AA 'and defines with the crane 42, the minimum radius Dmin of the annular intervention surface 132. In contrast, in the radially deployed position, the angle θ formed by the vertical passing through second point 62 and the vertical section is greater than 10 °, is for example between 12 ° and 20 °.

As shown on the right in FIG. 7, the ship 22 is then placed further away from the axis A-A 'and defines with the crane 42 the maximum radius Dmax of the annular intervention surface 132.

Further, the intermediate height h of the flexible upper portion 66 of the conduit 26, taken between the top 134 of the upwardly directed bend 75A and the lowest point 136 of the downward bend 75B, fits the bottom depth 14 of the body of water, for a given length of the transport pipe 26.

For a transport pipe 26 having a rigid lower portion 64 of given length 11, for example between 700 m and 1000 m and a flexible upper portion 66 of given length 12, for example between 400 m and 450 m, it is thus possible to extract material on an annular surface 132 of the bottom 14 of the water extent defined in the depth window P and distance D to the axis AA 'located inside the closed curve 140 substantially trapezoidal of Figure 8, without having to change the length of the pipe 26, and without having to move.

In a first variant of use of the device 18, the surface assembly 20 of a first vessel 22 is used to collect the material from the transport pipe 26 until a given quantity of material is received by the receiving and processing means 100 of the first ship 22.

Then, the first point 62 of the pipe 26 is disconnected from the surface assembly 20 of this first vessel 22 and the first vessel 22 moves away from the device 18.

A second vessel (not shown), which has available material storage means is then brought opposite the extraction device 18 and the first point 62 of the pipe is then connected to the surface assembly 20 of the second vessel . In yet another variant, the transport pipe 26 is flexible over substantially its entire length and each functional line 30 is arranged around the transport pipe 26 to form a flexible pipe as described in the French application No. 07 56579 of the Application ress. In this variant, the transport duct 26 and each functional line 30 are jointly deployable between a rest configuration wound on a winding drum placed on the laying ship 22 and a deployed configuration towards the bottom 14 of the breadth. In another alternative embodiment, the extraction device 18 is moved as a whole after the second point 62 has been disconnected from the surface assembly 20 from a first anchor point. anchor 36 on the bottom 14 of the body of water to a second anchor point of the anchor 36 on the bottom 14 of the body of water, without reassembling the pipe 26 and the set of bottom 24 on the surface assembly 20.

For this purpose, a vessel (not shown) carrying a crane is used to partially lift the pipe 26 and the anchor 36 away from the bottom 14 at the first anchor point, by gripping the pipe 26 for example at the The ship then conveys the extraction device 18 to the second anchor point, where the pipe 26 and the anchor 36 are lowered to place the anchor 36 in contact with the bottom 14. The pipe 26 and the anchor 36 remain immersed under the surface 16 of the body of water 12 during transport between the first anchor point and the second anchor point. The buoyancy provided by the buoyancy assembly 28 facilitates the lifting of the extraction device 18 and allows its transport by keeping the rigid lower portion 64 substantially vertical.

Alternatively, the flexible upper portion 66 occupies a catenary configuration in the connected configuration.

The anchor 26 is for example of the type suction anchor ("suction pile" in English) or gravity base type of gravity anchor ("gravity base").

Claims

1 .- Apparatus for extracting (18) a material comprising rocks and / or sediments located at the bottom (14) of a body of water (12), of the type comprising:

- a bottom assembly (24) comprising means (50, 52) for taking the material on the bottom (14) of the body of water (12);

- a pipe (26) for transporting the sampled material, connected at a first point (60) to the bottom assembly (24) and to be connected at a second point (62) to a floating surface assembly (20) on the body of water (12); characterized in that the bottom assembly (24) comprises anchoring means (36) in the bottom (14) of the body of water (12), the extraction device (18) comprising a set of buoyancy device (28) to be fully immersed under the body of water (12), the buoyancy assembly (28) being secured to at least one upper region of the transport pipe (26) to maintain the transport (26) in a substantially vertical configuration in the water body (12) between the bottom assembly (24) and the upper region when the second point (62) is disconnected from the surface assembly (20) .

2.- Device (18) according to claim 1, characterized in that the buoyancy assembly (20) comprises a plurality of buoys (96, 98) mounted around the upper region of the transport pipe (26).

3.- Device (18) according to any one of claims 1 or 2, characterized in that the transport pipe (26) comprises a rigid lower portion (64) connected to the bottom assembly (24) and a portion flexible upper member (66) connected to the rigid lower portion (64), the buoyancy assembly (28) being mounted at least partially on the rigid lower portion (64).

4.- Device (18) according to any one of claims 1 or 2, characterized in that the transport pipe (26) is flexible over substantially its entire length to be deployable between a wound configuration on a winding drum mounted by the surface assembly (20) and a deployed configuration in the body of water (12).

5.- Device (18) according to any one of the preceding claims, characterized in that the bottom assembly (24) comprises a puller vehicle (38), connected to the transport pipe (26), the sampling means (50) being carried by the extractor vehicle (38).

6.- Device (18) according to any one of the preceding claims, characterized in that the bottom assembly (24) comprises a support (54) for collecting material, connected to the transport pipe (26), the a collection support (54) being intended to be placed on the bottom (14) of the water body (12) to collect the material taken by sampling means (52), the sampling means (52) being intended to be maneuvers from the entire surface

(20) independently of the collection medium (54).

7.- Device according to any one of the preceding claims, characterized in that the anchoring means (36) comprise an anchor held stationary in the bottom of the body of water.

8.- Installation (10) for extracting material located at the bottom (14) of a body of water (12), characterized in that it comprises: - a surface assembly (20) intended for extending at least partially above the surface (16) of the body of water (12);

an extraction device (18) according to any one of the preceding claims, the second point (62) of the transport pipe (26) being displaceable relative to the surface assembly (20) between a connected configuration in which the second point (62) is connected to the surface assembly (20) and a disassembled configuration in which the second point (62) is located completely away from the surface assembly (20), the whole of buoyancy (28) maintaining the transport pipe (26) in a substantially vertical configuration in the water body (12) between the bottom assembly (24) and the upper region, in the connected configuration and in the configuration dismounted.

9. A method of extracting a material located at the bottom (14) of a body of water (12) with the aid of an installation (10) according to claim 8, characterized in that it comprises the following steps: - connecting the second point (62) of the transport pipe (26) to the surface assembly (20);

- extraction of the material from the bottom (14) of the body of water (12) by the sampling means (50, 52); conveying the extracted material to the surface assembly (20) through the transport pipe (26); then

- disconnecting the second point (62) of the transport pipe (26) away from the surface assembly (20), the buoyancy assembly (28) holding the transport pipe (26) in a substantially vertically in the body of water (12) between the bottom assembly (24) and the upper region after the disconnection.

10.- Method according to claim 9, characterized in that it comprises, after the disconnection step, an additional step of connecting the second point (62) of the transport pipe (26) to the entire surface ( 20).

1 1 .- A method according to claim 9 or 10, characterized in that the installation (10) comprises a first vessel (22) and a second vessel, each vessel carrying a surface assembly (20), the method comprising the steps following: - connecting the second point (62) of the transport pipe (26) to the surface assembly (20) of the first vessel (22);

extraction of the material from the bottom (14) of the body of water (12) by the sampling means (50, 52),

conveying the extracted material to the surface assembly (20) of the first vessel (22) through the transport pipe (26), and

- disconnecting the second point (62) of the transport pipe (26) away from the surface assembly (20) of the first vessel (22), the buoyancy assembly (20) holding the transport pipe ( 26) in a substantially vertical configuration in the body of water (12) between the bottom assembly (24) and the upper region,

- connecting the second point (62) of the transport pipe (26) to the surface assembly (20) of the second vessel.