DK2288789T3

DK2288789T3 - DEVICE FOR THE EXTRACTION OF A MATERIAL FROM THE BOTTOM OF A WATER MASS, PLACES FOR EXTRACTION AND RELATED PROCEDURE

Info

Publication number: DK2288789T3
Application number: DK09742262.0T
Authority: DK
Inventors: Philippe Espinasse
Original assignee: Technip France Sas
Priority date: 2008-04-08
Filing date: 2009-04-07
Publication date: 2018-09-17
Also published as: WO2009136064A1; MX2010011122A; FR2929638B1; PT2288789T; EP2288789B1; JP2011520046A; BRPI0911059B1; BRPI0911059A2; EP2288789A1; FR2929638A1; JP5390593B2; NZ588463A

Description

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

The present invention concerns a device for extracting a material situated at the bottom of an expanse of water, according to the preamble of claim 1.

Such devices are in particular intended for mining seabeds, or earthworking of sea beds for the placement of hydrocarbon production equipment. A device of the aforementioned type is known from document FR-A-2 467 283. 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 circulating on the seabed and connected to the base station by a flexible connection called a jumper.

To lower the bottom assembly into the water, it is known to use a string of rigid hollow rods that connect the base station and the surface installation. The string of rods inwardly defines a passage for circulation of the material gathered at the bottom to convey it to the surface.

Such a device is therefore satisfactory during normal mining, in calm water, of the extraction device.

However, in case of storm or when the surface installation on the ship must be temporarily moved, it is necessary to raise the assembly of the string of rods constituting the transport pipe in the carrying ship, as well as the subsea vehicle for gathering the material on the bottom of the expanse of water and the pumping equipment.

Such an operation is tedious and slow, which is detrimental to the safety and operating cost of the device. EP 0 063 911 discloses an installation for exploiting a petroleum fluid in the bottom of the expanse of water which does not comprise material sampling means on the bottom of the expanse of water. DE 199 02 33 discloses an installation for sampling material on the bottom of the expanse of water according to the preamble of claim 1. US 3,697,134, DE 3129228 and US 3,811,730 disclose installations for sampling material on the bottom of the expanse of water which comprise mobile sampling vehicles on the bottom of the expanse of water.

One aim of the invention is therefore to obtain a device for extracting a material situated on the bottom of an expanse of water that is safer and less expensive to operate.

To that end, the invention concerns a device according to claim 1.

The device according to the invention can comprise one or several of the features of claims 2 to 7.

The invention also concerns an installation for extracting a material according to claim 8 or 9.

The invention also concerns a method according to claim 10.

The method according to the invention can comprise one or several of the following featuresof claims 11 and 12.

The invention will be better understood upon reading the following description, provided solely as an example, and done in reference to the appended drawings, in which: - Figure 1 is a side view of a first extraction installation according to the invention, the surface ship being connected to the extraction device; - Figure 2 is a diagrammatic side view of an upper portion of the transport pipe provided with a buoyancy assembly; - Figure 3 is a view similar to Figure 1 during the disconnection of the surface ship; - Figure 4 is a view similar to Figure 1 in the absence of a surface ship; - Figure 5 is a side view of a detail of the first extraction installation in a contracted position of the flexible upper portion of the transport pipe; - Figure 6 is a view similar to Figure 5 in a deployed position of the flexible upper portion of the pipe; - Figure 7 is a top view diagrammatically illustrating the configurations of Figure 5 and Figure 6; and - Figure 8 is a curve illustrating the usage window of the extraction device of Figures 5 to 7 as a function of the depth and distance at the vertical axis of the rigid portion.

An extraction installation 10 according to the invention is illustrated in Figures 1 to 4. This installation is intended to gather materials situated at the bottom of an expanse of water 12 such as a sea, an ocean or a lake.

The expanse of water 12 rests on a bottom 14 defined by a solid material comprising rocks and/or sediment.

The device 10 aims for example to perform earthworking on the bottom 14 for the placement of a hydrocarbon mining installation, or to gather ores deposited on the bottom 14 for their subsequent exploitation on the surface 16 of the expanse of water 12.

As illustrated by Figure 1, the installation 10 comprises a submerged extraction device 18 and a surface assembly 20 intended to collect, treat, and store the material gathered and brought up to the surface by the extraction device 18.

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

The extraction device 18 comprises a bottom assembly 24 for gathering material on the bottom 14 of the expanse of water 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 keep it in a substantially vertical configuration in the expanse of water 12.

The extraction device 18 also comprises functional lines 30 for powering the bottom assembly 24 and injecting gas into the pipe 26.

The bottom assembly 24 comprises a base station 32, extraction means 34A, 34B that can be moved in relation to the base station 32, and an anchor 36 for fixing the base station 32 on the bottom 14 of the expanse of water 12.

The base station 32 is intended to be placed in the vicinity of the bottom 14, spaced apart therefrom during mining of the materials.

The base station 32 comprises equipment (not shown) for pumping and treating the gathered material, such as pumps or filters for instance, and means for controlling the extraction means 34A, 34B. It can also comprise temporary storage means for the material gathered by the extraction means 34A, 34B.

In the example illustrated in Figure 1, the extraction means 34A, 34B comprise, on the left side in the drawing, an extraction vehicle 38 and a flexible connection 40 connecting the extraction vehicle 38 to the base station 32, and on the right side in the drawing, an extraction crane 42, associated with means 44 for receiving and treating the material, placed on the bottom 14 of the expanse of water 12 and connected to the base station 32 by a second flexible connection 46.

The extraction vehicle 38 is intended to move on the bottom 14 to gather material there. It comprises means 48 for independent movement on the bottom 14, and means 50 for gathering the material capable of digging, scraping, or drilling the material making up the bottom 14 and transporting it to the flexible connection 40.

One example of an extraction vehicle is described in French application FR-A-2 467 283.

The flexible connection 42 is sometimes referred to as a jumper. It is made up of a flexible tube having an upper end connected on the base station 32 and a lower end connected on the vehicle 38 to gather the material from the gathering means 50. It inwardly defines a material circulation opening emerging opposite the gathering means 50 and in the base station 32 to connect to the transport pipe 26.

The crane 42 can be deployed and actuated from the surface ship 22. It comprises a claw 52 for gathering the material on the bottom 14, and a cable 53 for deploying and moving the claw 52 to lower it from the ship 22 towards the bottom 14 and to move it in relation to the bottom 14.

In one alternative, the extraction means 34B also comprises a pneumatic drill integral with the claw 52 or a pneumatic drill deployed from the surface ship 22 by an additional deployment and movement cable.

The receiving means 44 is described for example in French application no.07 56579 by the Applicant.

It comprises an adjustable bearing support 54 placed on the bottom of the expanse of water, provided with a shredder/crusher and funnel for receiving the gathered material.

The claw 52 of the crane 42 can be moved in relation to the support 54 between a position for gathering material in contact with the bottom 14 of the expanse of water, and a position for tipping the material out into the support 54.

The second flexible connection 46 has a structure similar to that of the first flexible connection 40.

The anchor 36 comprises a fixing point in the bottom of the expanse of water and a connection cable to the base station 32. The station 32 is thus kept above the fixing point a few meters away from the bottom 14.

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

The pipe 26 comprises, in reference to Figure 1, a rigid lower portion 64, a flexible upper portion 66, and a connector 68 between the rigid portion and the flexible portion.

The transport pipe 26 inwardly defines, over its entire length between the first point 60 and the second point 62, a continuous inner opening 70 for the circulation of the material, intended to convey the material gathered on the bottom 14 of the expanse of water from the base station 32 to the surface assembly 20.

In the example illustrated in Figure 1, the rigid lower portion 64 comprises an end-to-end assembly of sections 72 of rigid metal tubes.

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

As will be seen below, and according to the invention, owing to the buoyancy assembly 28 and the anchor 36, the lower portion 64 extends along a substantially vertical axis A-A’ between the connector 68 and the base station 32 regardless of the configuration of the flexible upper portion 66.

The lower portion 64 is also provided with two stiffeners 73 situated in the vicinity of the connector 68.

The connector 68 is situated at a depth between 1 m and 200 m under the surface 16.

The flexible upper portion 66 is made with a base of a flexible pipe 74 having a minimum radius of curvature greater than 12 m.

The flexible upper portion 66 is thus able to deform between an S-shaped connected configuration, in which it is connected to the surface assembly 20, as illustrated in Figure 1, and a upside-down U-shaped disassembled configuration in which it is disconnected from the surface assembly 20 and extends downward parallel to the rigid portion 64, as shown in Figure 4.

In the S-shaped connected configuration, the second point 62 is kept connected on the surface assembly 20 above the connector 68. The flexible pipe 74 forms, from the connector 68 towards the second point 62, a bend 75A oriented upward, a bend 75B oriented downward, then a substantially vertical section 75C.

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

Alternatively, the flexible upper portion 66 is provided with the cable 80 and buoy 82. The first point 62 is then able to rest in the expanse of water 12 or on the bottom 14 of the expanse of water when it is disconnected from the surface assembly 20.

The functional lines 30 comprise lines 90 for transporting electrical and/or hydraulic power, and for transporting information to power the extraction devices 34A, 34B and the base station 32, and at least one line 92 for injecting gas into the inner opening 70 of the transport pipe 26 to convey the material from the base station towards the surface assembly 20.

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

According to the invention, the buoyancy assembly 28 comprises a plurality of buoys 96, 98 axially distributed along the transport pipe 26.

As illustrated by Figure 2, the transport pipe 26 thus comprises a first group of buoys 96 mounted coaxially 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 sealing foam and are axially fixed around the pipe 26 via clamps, as described in patent application GB 2 288 205 by the English company CRP.

In the illustrated example, 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 having a length longer than 50% of the length of the pipe 26.

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

The buoys 96, 98 are dimensioned to keep the rigid portion 64 substantially vertical in the expanse of water 12 to compensate for the weight of the pipe 26 and any fluid that may be contained in said 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 pipe 26, an upwardly oriented force greater than the force resulting from the difference between the weight of the pipe 26 and its content, on one hand, and the buoyancy exerted on the pipe 26, on the other hand.

In another alternative, the buoyancy assembly 28 comprises a single buoy 96 made from a hollow shell completely submerged in the expanse of water. The single buoy is arranged vertically above the connector 68 and is connected to the connector 68 by a chain.

The surface assembly 20 comprises means 100 for receiving, settling and treating the material received from the transport pipe 28, electric and/or hydraulic power and control means 102 or extraction 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 is lowered towards the bottom 14 of the expanse of water.

To that end, the base station 32 and the extraction means 34A, 34B are gradually lowered towards the bottom 14 of the expanse of water 12 from the ship 22 through successive assembly of the tube sections 72 forming the rigid lower portion 64 of the transport pipe 26.

When the rigid portion 64 is assembled, buoys 96 are regularly mounted around the tube sections 72 and are axially wedged around said tubes 72 to form the buoyancy assembly 28.

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

Moreover, the function 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 situated a few meters above the bottom 14 of the expanse of water 12, the anchor 36 is put into place and its fixing point is immobilized in the bottom 14 of the expanse of water.

The buoys 96, 98 and the buoyancy assembly 28 creating an upward tractive force on the upper region of the transport pipe 26 provided with buoys 96, 98, and the anchor 36 creating a force for keeping the lower end 60 of the transport pipe 26 in the vicinity of the bottom 14 of the expanse of water 12, the rigid lower portion 64 of the transport pipe 26 spontaneously and continuously aligns itself along a substantially vertical axis A-A’ between the anchor 36 and the connector 68.

Moreover, the flexible upper portion 66 adopts a wave-shaped configuration that absorbs the local displacements of the ship 20 in relation to the rigid portion 64.

The extraction means 34A, 34B are then activated to gather material on the bottom 14 of the expanse of water 12 and to bring the gathered material through the respective flexible lines 40, 46 to the base station 32.

The gathered material is then brought up through the inner opening 70 of the transport pipe 26 between the base station 32 and the receiving and treatment means 100 on the surface assembly 20, in particular under the effect of the gas injected by the gas injection line 92 into the opening 70, and/or by centrifugal pumps mounted on the base station 32 or on the base of the anchor 36.

In case of storm or emergency, the first point 62 can be disconnected very quickly from the surface assembly 20 to be placed spaced away from the ship 22 in the expanse of water 12, such that the upper portion 66 occupies its disassembled configuration illustrated by Figure 3.

Once it is disconnected, the ship 22 can quickly move away from the extraction device 18, in particular when a storm agitates the expanse of water 12.

However, even when the second point 62 is disconnected, the transport pipe 26 remains substantially vertical in the expanse of water 12, in particular in the rigid lower portion 64 between the base station 32 and the connector 68, as illustrated by Figure 4.

Moreover, when the second point 62 of the pipe must be reconnected to a surface assembly 20, it can be drawn on a ship 22 towards the surface 16 via the fishing cable 80, which can be grasped using the buoy 82.

The extraction device 18 according to the invention can therefore be left continuously submerged in the expanse of water 12 in a substantially vertical configuration, without having to bring it back up into a ship 22 when it is not in use.

As illustrated by Figures 4 to 8, the extraction device 18 according to the invention, when it is equipped with extraction means 34B comprising a crane 42 integral with the ship connected to receiving means 44 for treating the material placed on the bottom of the expanse of water, has a large operating radius on the bottom 14 of the expanse of water, even when the second point 62 is kept connected on the surface assembly 20, and when the anchor 36 is kept immobile on the bottom 14 of the expanse of water.

Thus, in reference to Figure 7, for each position of the ship 22, the claw 52 situated at the lower end of the crane 42 is capable of treating, projected on the bottom 14, a discshaped surface 130 centered on the ship 22. Moreover, the ship 22 can rotate 360° around the axis A-A’, allowing treatment of the annular surface 132 centered on the axis A-A’, moving the bearing support 54 in a corresponding manner to place it in the disc-shaped surface 130.

As illustrated by Figures 5, 6 and 7, the expanse of the annular treatment surface 132 around the axis A-A’ is defined by the S-shaped configuration of the flexible upper portion 66.

Thus, when the flexible upper portion 66 occupies its S-shaped configuration, it is capable of being moved by the ship 22 between a radially contracted position, shown in

Figure 5, in which the second point 62 connected on the surface assembly 20 is positioned in the vicinity of the vertical axis A-A’ of the rigid lower portion 64, and a radially deployed position, shown in Figure 5, in which the second point 62 is farther from the vertical axis A-A’ of the lower portion 64.

As illustrated in Figure 5, in the radially contracted position, the angle θ formed by a vertical axis B-B’ that passes through the second point 62 and the upper section of the flexible upper portion 66 is less than - 10° and is for example between - 15° and - 20°.

As shown on the left side of Figure 7, the ship 22 is then placed in the vicinity of the axis A-A’ and defines, with the crane 42, the minimum radius Dmin of the annular operating surface 132.

On the contrary, in the radially deployed position, the angle θ formed by the vertical line passing through the second point 62 and the vertical section is greater than 10°, is for example between 12° and 20°.

As shown on the right side of Figure 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 operating surface 132.

Moreover, the intermediate height h of the flexible upper portion 66 of the pipe 26, between the apex 134 of the upwardly-oriented bend 75A and the lowest point 136 of the downwardly-oriented bend 75B, adapts to the depth of the bottom 14 of the expanse of water, for a given length of the transport pipe 26.

For a transport pipe 26 having a rigid lower portion 64 with a given length 11, for example between 700 m and 1000 m and a flexible upper portion 66 with a given length I2, 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 expanse of water defined in the window of depth P and distance D at the axis A-A’ situated inside the substantially trapezoidal closed curve 140 of Figure 8, without having to modify the length of the pipe 26, and without having to move it.

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

Then, the first point 62 of the pipe 26 is disconnected from the surface assembly 20 of said first ship 22 and the first ship 22 moves away from the device 18. A second ship (not shown), which includes available material storage means, is then brought across from the extraction device 18 and the first point 62 of the pipe is then connected on the surface assembly 20 of said second ship.

In still another alternative, 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 French application no. 07 56579 by the Applicant.

In this alternative, the transport pipe 26 and each functional line 30 can be deployed jointly between a rest configuration wound on a winding drum placed on the lay barge 22 and a configuration deployed towards the bottom 14 of the expanse of water 12.

In another alternative use, the extraction device 18 is moved in its entirety, after disconnection of the second point 62 spaced away from the surface assembly 20, from a first anchoring point of the anchor 36 on the bottom 14 of the expanse of water towards a second anchoring point of the anchor 36 on the bottom 14 of the expanse of water, without bringing the pipe 26 and the bottom assembly 24 back up on the surface assembly 20.

To that end, a ship (not shown) carrying a crane is used to partially raise the pipe 26 and the anchor 36 spaced apart from the bottom 14 at the first anchoring point, by grasping the pipe 26 for example at the connector 68. The ship then conveys the extraction device 18 towards the second anchoring point, where the pipe 26 and the anchor 36 are lowered again to place the anchor 36 in contact with the bottom 14. The pipe 26 and the anchor 36 remain submerged under the surface 16 of the expanse of water 12 during the transport between the first anchoring point and the second anchoring point. The buoyancy provided by the buoyancy assembly 28 facilitates raising of the extraction device 18 and allows its transport while 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 suction pile type or the gravity base type.

Claims

An apparatus for the extraction (18) of a material comprising cutting pieces and / or deposits from the bottom (14) of a body of water (12), the device being of the type comprising: - a bottom unit (24) comprising means (50, 52) for removing the material from the bottom (14) of the body of water (12) and a base station (32); - a conduit (26) for transporting the withdrawn material coupled at a first point (60) to the base unit (24) and intended to be coupled at a second point (62) to a surface unit (20) flowing on the body of water (12); wherein the bottom unit (24) comprises anchoring means (36) on the bottom (14) of the body of water (12), characterized in that the extraction device (18) comprises a buoyancy unit (28) intended for full immersion in the body of water (12), wherein the buoyancy unit (28) is fixedly coupled to at least one upper region of the conveyor line (26) to hold the conveyor line (26) in a substantially vertical configuration in the body of water (12) between the bottom unit (24) and the upper region when the second point ( 62) is disconnected from the surface unit (20), where the anchoring means (36) comprise a fastening point on the bottom of the body of water and a connecting cable to the base station (32).

Device (18) according to claim 1, characterized in that the buoyancy unit (20) comprises a plurality of buoys (96, 98) mounted around the upper region of the conveyor line (26).

Device (18) according to any one of claims 1 or 2, characterized in that the conveyor line (26) comprises a lower rigid part (64) coupled to the base unit (24) and an upper flexible part (66). ) coupled to the lower rigid portion (64), while the buoyancy unit (28) is mounted at least partially on the lower rigid portion (64).

Device (18) according to any one of claims 1 or 2, characterized in that the conveyor line (26) is substantially bendable over its full length to be used between a coiled configuration on a reeling drum carried by the surface unit. (20), and a rolled-out configuration in the body of water (12).

Device (18) according to any of the preceding claims, characterized in that the bottom unit (24) comprises a recovery vehicle (38) coupled to the transport line (26) while the withdrawal means (50) are carried by the recovery vehicle (38). ).

Device (18) according to any one of the preceding claims, characterized in that the bottom unit (24) comprises a material collection carrier (54) coupled to the transport line (26), which collection carrier (54) is intended to be disposed on the bottom (14) of the body of water (12) for receiving the material withdrawn by the withdrawal means (52), which withdrawal means (52) are intended to be controlled from the surface unit (20) independently of the collection carrier (54).

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

An installation (10) for extracting a material from the bottom (14) of a body of water (12), characterized in that it comprises: - a surface unit (20) intended to be at least partially above the surface (16) the wastewater mass (12); - a recovery device (18) according to any one of the preceding claims, wherein the second point (62) of the transport line (26) can be displaced relative to the surface unit (20) between an interconnected configuration, wherein the second point (62) is coupled to the surface unit (20), and a dismounted configuration wherein the second point (62) is completely away from the surface unit (20), where the buoyancy unit (28) holds the transport line (26) in a substantially vertical configuration in the body of water (12). ) between the base unit (24) and the upper region in the interconnected configuration and in the dismounted configuration.

System (10) according to claim 8, characterized in that the surface unit (20) is carried by a vessel (22) floating on the body of water, which vessel (22) is able to rotate 360 ° about an axis (A-1). A ') which is substantially vertical to the conveyor line (26) when the second point (62) is held interconnected with the surface unit and when the anchoring means (36) are kept motionless at the bottom of the body of water.

A method for recovering a material from the bottom (14) of a body of water (12) by means of a plant (10) according to claim 8 or 9, characterized in that it comprises the following steps: - interconnection of the second point (62) ) of the conveyor line (26) with the surface unit (20); extracting the material from the bottom (14) of the body of water (12) by means of the withdrawing means (50, 52); transporting the recovered material to the surface unit (20) via the transport line (26); then - disconnecting the second point (62) of the conveyor line (26) away from the surface unit (20), while the buoyancy unit (28) holds the conveyor line (26) in a substantially vertical configuration in the body of water (12) between the bottom unit (24) and the upper area after disconnection.

Method according to claim 10, characterized in that, after the disconnection step, it comprises an additional step of interconnecting the second point (62) of the transport line (26) with the surface unit (20).

Method according to claim 10 or 11, characterized in that the system (10) comprises a first vessel (22) and a second vessel, each vessel carrying a surface unit (20), the method comprising the steps of: - coupling the second point (62) of the transport line (26) with the surface unit (20) of the first vessel (22); - extracting the material from the bottom (14) of the body of water (12) by means of the extraction means (50, 52), - transporting the recovered material to the surface unit (20) of the first vessel (22) via the transport line (26), then - disconnecting of the second point (62) of the conveyor line (26) away from the surface unit (20) of the first vessel (22), while the buoyancy unit (20) holds the conveyor line (26) in a substantially vertical configuration in the body of water (12) between the bottom unit ( 24) and the upper area, - connecting the second point (62) of the transport line (26) with the surface unit (20) of the second vessel.