GB2598866A - Device for connecting an underwater pipe to a fixed structure and associated connection method - Google Patents

Abstract

The invention relates to an underwater pipe (1) comprising a main part (6) resting on the seabed (7) and connected to two risers (8, 9) by curved parts (10, 11). These are an integral part of the underwater pipe (1) and are produced by controlled curvature of the underwater pipe (1) during its connection to the fixed structures (3, 5). This curvature is obtained according to a connection method according to the invention in which tensioning means are connected at one end (2, 4) of the underwater pipe (1) in order to bring it to the fixed structure (3, 5) and at a second connection point of the underwater pipe (1) located at a distance from the lower end or equal to the length of the riser (8, 9). Tractions exerted on the pipe by the tensioning means enable the desired curvature to be obtained.

Description

DEVICE FOR CONNECTING AN UNDERWATER PIPE TO A FIXED

STRUCTURE AND ASSOCIATED CONNECTION METHOD

The present invention concerns the connection to a fixed structure of a pipe, in particular for example for the connection together of offshore installations for the production or export of effluents, such as petroleum or gas, with installations for treatment of those effluents or with terminals for export or import of the treated effluents.

More particularly, the invention concerns the connection of a submarine pipe of rigid type to a fixed structure, which may be a gravity platform or a platform with piles, in order to transport effluents to or from that fixed structure over a distance which may go from a few meters to a few kilometers or even a few tens of kilometers.

The invention applies to installations for hydrocarbon production at sea but more generally also applies to the transport of any effluent (semi-liquid, liquid or gaseous) produced or injected by offshore installations. Such installations require the connection at the surface of a submarine pipe to any installation enabling for example the production, injection, treatment, pumping or the compression of effluent and that is located on a fixed structure, for example such as a well head. Typically, the submarine pipe rests on the seabed at a depth which may go from a few tens of meters to approximately two hundred meters, and it comes to be connected to the fixed structure at or near the surface by an end of a riser linked to the submarine pipe by a bent portion.

The invention applies more particularly to that bent portion connecting the riser to the part of the pipe resting on the seabed. The submarine pipe has two ends which may each be connected to a fixed structure. A similar configuration is to be found for the connection of these two ends of the submarine pipe. The laying of the submarine pipe is initiated at a first end of the pipe and the laying of the pipe ends at a second end also called the "abandon end" since this is the end which is "abandoned" offshore once the laying has ended.

There are numerous existing solutions for connecting a rigid submarine pipe to a fixed structure such as a platform, each having a different technique to achieve the transition between the part of the submarine pipe resting on the seabed and the pipe riser coming up towards the surface as indicated below.

The most conventional connections between a submarine pipe and a riser consist in initiating or abandoning the end of the rigid pipe on the seabed, at a short distance from the platform to connect. A riser is fastened to the structure to connect between the surface and the seabed, then with the help of divers or submarine robots, a section of connecting pipe called connecting spool is put in place between the end of the rigid pipe laid on the seabed and the lower end of the pre-installed riser. This connecting spool may be either flexible (in the form of a portion of flexible pipe), or rigid On the form of tubes of steel welded or coupled together).

As an alternative to the connecting spool described above, a long section of flexible pipe (hose) may be connected to the end of the rigid submarine pipe resting on the seabed and also connected directly to the fixed structure at the surface or at small water depth.

To connect submarine pipes at small depth (typically less than 50 m), a method for a rigid riser "thrown" from the submarine pipe-laying means is sometimes employed. The laying means is in practice a barge equipped for submarine pipe laying and having in particular a hoisting crane. This method consists of fabricating the riser at the same time as the pipe on the laying means, including the bent or elbow portion between the submarine pipe and the riser, and transferring it to the platform by virtue of the hoisting crane of the laying means. This method is limited by the available under-hook height of the crane and by the minimum distance between the laying means and the platform at the time of transferring the riser to the latter. For this reason, this connection technique is in practice reserved for very small depths, that is to say less than 50 m.

For large water depths, connections of rigid submarine pipes to structures that are generally floating or moored, are carried out directly by rigid pipes referred to as "catenary" pipes. These direct connections are made possible by virtue of rotary joint systems at the surface which accommodate relative movements of the pipe and the platform. This method with a rotary joint may also be envisioned on fixed structures even though its cost is in general prohibitive.

All the known connection solutions involve either submarine welds or mechanical connections requiring very costly operations by saturation divers or submarine robots, or very costly materials, such as sections of flexible pipes, automatic connectors or flexible joints.

Document US 3 531 941 describes a method of bending a submarine pipe in which the bending of the pipe is achieved by the tension generated by a winch on a cable. The cable is linked to the submarine pipe by a bending guide. The bending of the pipe is obtained by the combined action of the tension generated by the winch and the shape of the bending guide. During the entire operation of laying the submarine cable, including the bending of the pipe, the end of the pipe is linked to the fixed structure by a hinged coupling. On bending the pipe, the pipe is at the same time retained (i) in the channel of the bending guide on account of the pressure applied by the channel on the part of the pipe to bend and (ii) at the location of its anchorage to the fixed structure by a clamp mounted on a shaft allowing rotation in one plane. In order to avoid damaging the pipe between these two fixed points during the bending operation, document US 3 531 941 envisions providing the clamp with jaws making it possible, by clamping them, to block the translational movement of the pipe but which are sufficiently wide for them to allow the pipe to slide if necessary, which would necessarily lead to a complex design. Without such a system enabling the pipe to slide in the clamp, compression may arise in the pipe between the attachment point to the fixed structure and the bending guide and inappropriate deformation of the pipe may result therefrom.

The present invention is directed to providing a new type of direct connection between a submarine pipe and a fixed structure requiring neither connection by divers or robots, nor a section of flexible pipe, nor a rotary joint system at riser end, nor bending guide during implementation, and which is applicable for depths of water going from a few tens of meters to typically two hundred meters.

To that end, according to a first aspect, the invention relates to a device for connecting, to a fixed structure, a submarine pipe comprising, once connected, a main portion able to be laid on the seabed and at least one riser that are linked together by a bent portion. According to the invention, the connecting device comprises connecting members located on the fixed structure, that are able to fasten the riser thereto and which comprise at least an upper connecting member and a lower connecting member, laying means able to put in place the submarine pipe in order to connect it to the fixed structure, and tension means linked to the fixed structure and able to apply a controlled mechanical tension at two or more distinct attachment points of the submarine pipe during the putting in place of the submarine pipe to form the bent portion before the connection of the submarine pipe to the fixed structure.

By producing the bent portion forming the transition between the riser and the main portion of the submarine pipe, directly on the submarine pipe during its laying, operations in deep water as well as the use of special very costly materials are no longer necessary for connecting a submarine pipe to a fixed structure in the open sea.

This configuration of the submarine pipe makes it possible to eliminate the intermediate joints and the special parts necessary to connect or form the riser all of which are weak points in terms of mechanical strength properties and potential leakage points.

Preferably, in the connecting device according to the invention a first attachment point is located at an end of the submarine pipe configured to be connected to the fixed structure and a second attachment point is located at a greater distance from the end of the submarine pipe than the distance separating that end of the submarine pipe and the lower connecting member fastened on the fixed structure.

Advantageously, in the connecting device according to the invention the tension means comprise at least a first cable and a second cable mechanically linked to the fixed structure and furthermore linked respectively to the first and to the second attachment point on the submarine pipe.

This connecting device results in an assembly of simple means which are operated and implemented from the surface without requiring the involvement of specialized robots or divers.

Preferably, in the connecting device according to the invention, the tension means comprise a third cable linked to a third attachment point on the submarine pipe located at a distance sufficiently far from the end of the submarine pipe that, once the latter has been laid on the seabed, the third attachment point is at the level of the seabed.

The application of a tension at several points of the submarine pipe makes it possible to control the deformation thereof and thereby govern the geometry of the bent portion during its formation in situ.

Advantageously, in the connecting device according to the invention the tension means further comprise at least one pulley capable of orienting the direction of the traction applied by at least one of the cables onto the corresponding attachment point on the submarine pipe.

The use of directing pulleys makes it possible to control, from the surface, the tension applied to the different attachment points on the submarine pipe.

According to a second aspect, the present invention concerns a method of connecting a submarine pipe to a fixed structure, using laying means, the submarine pipe having a main portion able to be laid on the seabed and at least one riser that are linked together by a bent portion, said method comprising the following steps: putting the submarine pipe in place on the laying means to be laid on the seabed; connecting tension means to the submarine pipe that are linked to the fixed structure on which the submarine pipe is to be connected; laying the submarine pipe on the seabed; applying controlled traction to the submarine pipe by the tension means in order to form the bent portion of the submarine pipe progressively; and connecting the riser of the submarine pipe to the fixed structure by connecting members comprising at least an upper connecting member and a lower connecting member.

The connecting method defined above makes it possible to form the transition between the main portion of the submarine pipe resting on the seabed and the riser by using the pipe itself exclusively and operating from the surface without interruption of the operations of laying the submarine pipe. It also makes it possible to employ conventional laying means not requiring special means to be implemented such as divers or submarine work robots.

Advantageously, in the connecting method according to the invention: a first tension means is attached to one end of the submarine pipe to connect to the fixed structure; a second tension means is attached to a second attachment point of the submarine pipe located at a greater distance from the end of the submarine pipe than the distance separating said end from the lower connecting member; a first traction is applied by the first tension means in order to bring the end of the submarine pipe to the fixed structure at the surface or at a small depth, and a second traction is applied by the second tension means in order to apply the submarine pipe against said fixed structure to curve it and thus form the bent portion thereof.

Preferably, in the connecting method according to the invention a third tension means is attached to a third attachment point on the submarine pipe located at a distance sufficiently great from the end of the submarine pipe that, once the latter has been connected to the fixed structure, the third attachment point is at the level of the seabed.

This connecting method makes it possible to employ simple means usually available on submarine pipe laying sites and which are operated and installed from the surface without requiring the involvement of specialized robots or divers.

Advantageously, in the connecting method according to the invention the riser is connected to the fixed structure by connecting members after formation of the bent portion.

According to a third aspect, the invention concerns a submarine pipe comprising, once connected to at least one fixed structure, a main portion resting on the seabed and at least one riser which are connected to each other by a bent portion. This bent portion forms an integral part of the submarine pipe and is produced according to the connecting method as defined above.

By directly bending the submarine pipe for the purpose of its connection in the course of it being laid, the entirety of the effluent transport line upstream or downstream of the submarine pipe is preserved which limits the risk of leakages requiring operations at great depth. The maintenance of the continuity of the pipe from one end to the other also makes it possible to ensure, where these are provided, the continuity of the insulation of the pipe and of the cathodic protection.

Other features and advantages of the invention are shown by the following description of non-limiting embodiment examples of different aspects of the invention. The description refers to the appended drawings which are also given by way of non-limiting embodiment examples of the invention: Figure 1 is a diagrammatic view of a submarine pipe connected by both ends to fixed structures; Figure 2 illustrates a diagrammatic view of a first phase of the connection of the initiation end of a submarine pipe; Figure 3 illustrates with a diagrammatic view a second phase of the connection of the initiation end of a submarine pipe; Figure 4 is a diagrammatic view of a third phase of the connection of the initiation end of a submarine pipe; Figure 5 illustrates with a diagrammatic view a first phase of the connection of the abandon end of a submarine pipe; and Figure 6 illustrates with a diagrammatic view a second phase of the 25 connection of the abandon end of a submarine pipe; Below, the description of the invention is given in the context of a rigid submarine pipe for transporting an effluent of petroleum origin from an offshore extraction well to an offshore export or treatment terminal. This context of implementation of the invention is only described to facilitate the understanding of the invention but cannot in any case be considered as limiting thereof. The same applies for all the other implementation examples of the different features constituting of the invention described below solely for illustrative purposes.

Figure 1 shows a rigid submarine pipe 1 having two types of connection.

One of these is a first connection of a first end 2 of the rigid submarine pipe 1 to a first fixed structure 3 located by the initiation of the pipe. The first end 2 corresponds to the direction of laying of the pipe. It is by the first end 2 that the laying of the submarine pipe 1 has been initiated.

The other is a second connection of a second end 4 of the rigid submarine pipe 1 to a second fixed structure 5 located by the abandonment of the submarine pipe 1. It is at the second end 4 that the laying of the submarine pipe 1 has been terminated and it is this second end 4 of the submarine pipe 1 which has been "abandoned" once the laying activities were completed.

In the rest of the description, the ordinal numbers such as first, second or third are to be taken relative to the direction of laying of the submarine pipe 1.

Once connected to the first and second fixed structures 3 and 5, the submarine pipe 1 has a main pipe part 6 laid on the seabed 7, a first riser 8 connected to the first fixed structure 3 and a second riser 9 connected to the second fixed structure 5. The first and second risers 8 and 9 are respectively linked to the main pipe portion 6 by a first bent portion 10 and a second bent portion 11.

At each of its two ends 2 and 4, the submarine pipe 1 is connected to a fixed structure 3 or 5 without inserting any intermediate connection part, such as a spool, or insertion of a bowed, bent or flexible section in the submarine pipe linking the two fixed structures 3 and 5 in contrast to the conventional techniques described above.

The connecting method described below makes it possible to form the transition curve between the main portion 6 of the rigid submarine pipe 1 laid on the seabed 7 and a face or edge 13 or 14 of the fixed structure 3 or 5 onto which the riser 8 or 9 of the submarine pipe 1 is connected. As a matter of fact, fixed offshore structures are generally supported by an assembly of legs laid or anchored on the seabed in general forming a regular polyhedron with three or four faces rising from the seabed towards the surface. The riser 8 or 9 may thus be connected according to requirements to one of the faces or one of the edges 13 or 14 of the polyhedron formed by the legged arrangement of the fixed structure 3 or 5.

The first said second risers 8 and 9 resulting from the formation of the first and second bent portions 10 and 11 are rigidly fastened to the fixed structures 3 and 5 by connecting members 12 to reach a water depth such that the free part located below (of catenary shape) can bear the residual forces due to the external environment On particular those of waves and current) and the forces due to the flow of the effluents within the submarine pipe 1. The connecting members 12 may be clamps which lock around the riser. They comprise an upper connecting member (the one closest to the surface) and a lower connecting member 20 (the one closest to the seabed). According to the length of the riser 8 or 9 to connect to the fixed structure 3 or 5, one or more intermediate connecting members 12 may be required.

The connecting method makes it possible, for the first end 2 relative to the direction of laying, to bring that first end 2 of the submarine pipe 1 to the surface, and for the second end 4 to bring it sufficiently close to the surface for it to be possible to form a connection at less than 50 m of water depth, without recourse to what are referred to as "saturation" diving techniques. This connection at small depth may be achieved for example by an extension of pipe 28 itself rigidly fastened to the same face or edge 14 of the second fixed structure 5.

Figures 2, 3 and 4 illustrate different phases of the method of connecting the submarine pipe 1 to the first fixed structure 3 corresponding to the first end 2 by which is initiated the laying of the submarine pipe 1 by the laying means 15 which may be floating means.

As illustrated in Figure 2, a first, a second and a third cable 16, 17 30 and 18 are connected respectively to three winches (not shown) mechanically joined to the fixed structure 3. Instead of a winch/cable assembly, any other means making it possible to apply a tension of similar intensity to that of a winch, and to bring the submarine pipe 1 to the required distance from the fixed structure 3 or adjust the length of those cables to the required length may be implemented according to the invention. First of all, the first, second and third cables 16, 17 and 18 are put in place then the first fixed structure 3, passing if necessary but not imperatively by directing pulleys 19, and transferred to the laying means 15 to be connected to the appropriate part of the submarine pipe 1 before it leaves the laying means 15.

From the laying means 15, the first cable 16 is connected to the first end 2 of the submarine pipe 1. Next, the laying means 15 move away from the first fixed structure 3 in the laying direction of the submarine pipe 1.

When the laying means 15 are sufficiently far from the first fixed structure 3, the second cable 17 is connected at a distance D1 from the first end 2 of the submarine pipe 1. The distance D1 is defined so as to be slightly greater than the distance separating the first end 2 of the pipe from the lower connecting member 20 on the first face or edge 13 of the first fixed structure 3 once the submarine pipe 1 has been installed.

Next, the third cable 18 is connected onto the submarine pipe 1 from the laying means 15 at a sufficient distance from the first end 2 for the attachment point of the third cable 18 to be at the level of the seabed 7, once the pipe has been installed.

During the operation of connecting the submarine pipe 1 at the stage of the initiation of its laying, the pipe is assembled from the laying means 15 until these are at a sufficient distance from the first fixed structure 3 for the submarine pipe 1 to touch the seabed 7 at the location of the belly of the catenary so formed. As an alternative to the implementation of the submarine pipe 1 by assembly of sections of pipe on laying means 15, the pipe may be unwound during the progression of the laying means 15. At the same time as the sections of pipe are assembled on the laying means 15, the winches fastened to the first fixed structure 3 pull on the cables 16, 17 and 18 in order to control the length of cable between the first fixed structure 3 and the attachment points of the cables on the pipe. One of the winches exerts traction F on the first cable 16 in order to bring the first end 2 of the submarine pipe 1 to the surface.

The first, second and third cables 16, 17 and 18 are connected from the laying means 15 to the submarine pipe 1 respectively by a first mooring point at the pipe head, a first submarine clamp 21 and a second submarine clamp 22.

As shown in Figure 3, once the first end 2 is at the desired height and in position to be connected to the first fixed structure 3, the winch actuating the first cable 16 is stopped whereas the winches actuating the second and the third cables 17 and 18 continue to exert traction on the submarine pipe 1 towards the first fixed structure 3 so as to apply, as closely as possible to the first face or edge 13 of the first fixed structure 3, the upper portion of the submarine pipe 1 located between the first end 2 and the third (and last) submarine clamp 22. The travels of the first, second and third cables 16, 17 and 18 are adjusted so as to maintain constant tension in the submarine pipe 1 at the location of the laying means 15, and so as to control the formation of the curvature of the submarine pipe 1 between the lower connecting member 20 on the first face or edge 13 of the first fixed structure 3 and the seabed 7 which will form the first bent portion 10 linking the main portion 6 of the submarine pipe 1 to the first riser 8. During this operation of obtaining the controlled curvature of the submarine pipe 1, the relative position of the laying means 15 relative to the first fixed structure 3 and the length of submarine pipe 1 put in place from the laying means 15 are also adjusted.

As illustrated in figure 4, once the first bent portion 10 has been fully formed, the first riser 8 is fastened to the fixed structure 3 by the connecting members 12. These may be closed automatically or by the involvement of the various means such as divers or "ROV" remotely operated robots operating at small depth and of which the cost is significantly less than that incurred by deeper operations (below 50 meters). Once the connecting members have been closed, the first and second cables 16 and 17 may be disconnected from the submarine pipe 1. The third cable 18 remains connected until a sufficient length of submarine pipe has been laid on the seabed 7 making it possible, through friction, to take up the laying tension applied by the laying means 15 to the submarine pipe 1 during the subsequent part of its being put in place by assembly or unwinding. Subsequently, it may be disconnected from the submarine pipe 1 either from the surface, or using an ROV at the level of the seabed 7.

The submarine pipe 1 so curved has entered into the plastic domain. Control of the tensions and of the travels of the first, second and third cables 16, 17 and 18 and of the position of the laying means 15 during the curving operation makes it possible not to fold the pipe by forming a plastic rotary joint at one of the second or third submarine clamps 21 and 22 or at the level of the seabed 7. To that end, the profiles of the tensions and of the travels of the cables 16, 17 and 18 are defined by prior analyses using dedicated software applications. A control system provides the position guidance of the laying means 15 and the control of the tensions applied to the first, second and third cables 16, 17 and 18.

Figures 5 and 6 illustrate different phases of the method of connecting the second end 4 of the submarine pipe 1 to the second fixed structure 5. The second end 4 constitutes the end by which the submarine pipe 1 is abandoned by the laying means 15 when the laying of the submarine pipe 1 has been finished.

As illustrated in Figure 5, a fourth cable 23 and a fifth cable 24 are connected to two winches (not shown) mechanically fastened to the second fixed structure 5.

The fourth and fifth cables 23 and 24, connected to two winches (or any other means making it possible to apply the required tension and/or adjust the length of those cables to the required length) are put in place from the second fixed structure 5, passing if necessary by directing pulleys 19, and transferred to the laying means 15 (barge or ship) to be connected to the submarine pipe 1.

The fourth cable 23 is connected to the second end 4 of the submarine pipe 1. The fifth cable 24 is connected at a distance D2 from the second end 4 of the submarine pipe 1. The distance D2 is defined so as to be slightly greater than the distance separating the second end 4 of the submarine pipe 1 and a lower connecting member 20 on the second face or edge 14 of the second fixed structure 5 once the submarine pipe 1 has been installed.

Furthermore, a slide plane 25 may optionally be pre-installed on the second face or edge 14 of the second fixed structure 5 so as to better control the path of the second end 4 of the pipe at the time of the operation forming the curvature between the second riser 9 and the main portion 6 of the submarine pipe resting on the seabed 7.

The total length of the submarine pipe 1 is adjusted on approaching the second fixed structure 5 to which it is to be connected, in relation to the relative position of the second fixed structure 5 and of the laying means 15 at the time of the transfer and according to the final altitude desired for the second end 4 after forming the second bent portion 11.

Once the length of the submarine pipe has been adjusted, the second end 4 of the pipe is connected to the fourth cable 23 and to a lifting buoy 26 temporarily attached to the submarine pipe 1 and provided to confine the path of the second end 4 to a plane which is practically horizontal during its transfer from the laying means 15 to the second fixed structure 5.

This transfer operation makes it possible to transfer the horizontal tension in the submarine pipe 1 from an abandon cable 27 put in place from the laying means 15 and the fourth cable 23 put in place from the second fixed structure 5.

Once the tension transfer operation has been carried out, the lifting buoy 26 is disconnected from the second end 4 of the submarine pipe 1, as well as the abandon cable 27. The submarine pipe 1 is then ready to be curved in controlled manner from the second fixed structure 5 without intervention from the laying means 15 as shown in Figure 6.

To have control over the curvature to form the second bent portion 11 linking the second riser 9 to the main portion of the pipe 6 (of which it forms an integral part), the second end 4 is lowered along the second fixed structure 6 on the slide plane 25 while slowly unwinding the fourth cable 23 in order to keep that cable in tension, and by winding in the fifth cable 24 so as to apply the portion of the submarine pipe 1 which will become the second riser 9, in the direction of the second face or edge 14 of the fixed structure 5. The curvature is formed at least partly thanks to the own weight of the submarine pipe 1 and to the force applied by the fifth cable 24.

Once the second end 4 has been lowered by the fourth cable 23 to the desired altitude, the second bent portion 11 is formed and the second riser 9 is fastened to the second face or edge 14 of the second fixed structure 5 using connecting members 12. As for the connection onto the first fixed structure 3, the connecting members 12 may be closed by any means (automatic, divers or using ROVs). Once these connecting members have been closed on the second riser 9, the fourth and fifth cables 23 and 24 may be disconnected from the submarine pipe 1.

As for the first bent portion 10, the pipe thus curved to form the second bent portion 11 has entered the plastic domain.

Control of the tensions and travels of the fourth and fifth cables 23 and 24 during the curving operation makes it possible not to fold the pipe by forming a plastic rotary connection on the submarine pipe 1 at the attachment points of the cables 23 and 24 or at the level of the seabed 7. To that end, the profiles of the tensions and of the travels of the cables 23 and 24 as well as for the abandon cable 27 are defined by prior analyses using dedicated software applications A control system provides the position guidance of the laying means 15 and the control of the tensions applied to the fourth and fifth cables 23 and 24 as well as to the abandon cable 27.

To terminate the connection of the second end 4 to the second fixed structure 5, the pipe extension 28 is connected to the second end 4 to emerge at the surface. The depth of the second end 4 of the submarine pipe 1 is sufficiently small for the connection to be made by divers without a saturation system, and thus economically relative to the conventional solutions in depths exceeding 50 m.

Although in the above description the particular aspects of the invention have been described in the context of the connection of a submarine pipe of simple rigid type, it could be implemented in other configurations, for example in particular for thermally insulated pipelines or pipelines onshore in which the curvatures are necessitated by the topology of the pipeline which must conform to that of the terrain or different levels of the installations to connect. As indicated in the introductory part of the description, the pipe may serve for transporting effluents of the hydrocarbon type from the production or extraction area to an installation for treatment and/or export. Similarly, the pipe implemented according to the invention may be used to inject effluents (water or gas) underground from the treatment installation to an offshore or onshore injection area.

Claims (10)

1. CLAIMS1. Connecting device for connecting, to a fixed structure (3, 5) a submarine pipe (1) comprising, once connected, a main portion (6) able to be laid on the seabed (7) and at least one riser (8, 9) that are linked together by a bent portion (10, 11), characterized in that it comprises: connecting members (12) located on the fixed structure (3, 5), that are able to fasten the riser (8, 9) thereto and which comprise at least an upper connecting member and a lower connecting member (20); laying means (15) able to put in place the submarine pipe (1) in order to connect it to the fixed structure (3, 5); and tension means (16, 17, 18, 23, 24) linked to the fixed structure (3, 5) and able to apply a controlled mechanical tension at two or more distinct attachment points of the submarine pipe (1) during the putting in place of said submarine pipe (1) to form the bent portion (10, 11) before the connection of said submarine pipe (1) to the fixed structure (3, 5).
2. 2. Connecting device according to the preceding claim, wherein a first attachment point is located at an end (2, 4) of the submarine pipe (1) configured to be connected to the fixed structure (3, 5) and a second attachment point is located at a greater distance (D1, D2) from said end (2, 4) of the submarine pipe (1) than the distance separating that end (2, 4) of the submarine pipe from the lower connecting member (20).
3. 3. Connecting device according to the preceding claim, wherein the tension means (16, 17, 18, 23, 24) comprise at least a first cable (16, 23) and a second cable (17, 24), mechanically linked to the fixed structure (3, 5) and furthermore linked respectively to the first and to the second attachment point on the submarine pipe (1).
4. 4. Connecting device according to one of claims 2 or 3 wherein the tension means (16, 17, 18, 23, 24) comprise a third cable (18) linked to a third attachment point on the submarine pipe (1) located at a distance sufficiently far from said end (2) of the submarine pipe (1) that, once the latter has been laid on the seabed (7), the third attachment point is at the level of the seabed (7).
5. 5. Connecting device according to one of claims 3 or 4 wherein the tension means (16, 17, 18, 23, 24) further comprise at least one pulley (19) capable of orienting the direction of the tension transmitted by at least one of the cables (16, 17, 18, 23, 24) onto the corresponding attachment point on the submarine pipe (1).
6. 6. Connecting method for connecting a submarine pipe (1) to a fixed structure (3, 5), using laying means (15), the submarine pipe (1) having a main portion (6) able to be laid on the seabed (7) and at least one riser (8, 9) that are linked together by a bent portion (10, 11), said method comprising the following steps: - putting the submarine pipe (1) in place on the laying means (15) to be laid on the seabed (7); - connecting tension means (16, 17, 18, 23, 24) to the submarine pipe (1) that are linked to the fixed structure (3, 5) on which the submarine pipe (1) is to be connected; - laying the submarine pipe (1) on the seabed (7); -applying controlled traction to the submarine pipe (1) by the tension means (16, 17, 18, 23, 24) in order to form the bent portion (10, 11) of the submarine pipe (1) progressively; and - connecting the riser (8, 9) of the submarine pipe (1) to the fixed structure (3, 5) by connecting members (12) comprising at least an upper 30 connecting member and a lower connecting member.
7. 7. Connecting method according to the preceding claim, wherein: - a first tension means (16, 23) is attached to one end (2, 4) of the submarine pipe(1) to connect to the fixed structure (3, 5); a second tension means (17, 24) is attached to a second attachment point of the submarine pipe (1) located at a greater distance (D1, 02) from said end (2, 4) of the submarine pipe (1) than the distance separating said end (2, 4) from the lower connecting member (20); a first traction is applied by the first tension means (16, 23) in order to bring said end (2, 4) of the submarine pipe (1) to the fixed structure (3, 5) at the surface or at a small depth; and - a second traction is applied by the second tension means (17, 24) in order to apply the submarine pipe (1) against said fixed structure (3, 5) to curve it and thus form the bent portion (10, 11) thereof.
8. 8. Connecting method according to the preceding claim, wherein a third tension means (18) is attached to a third attachment point on the submarine pipe located at a distance sufficiently great from the end (2) of the submarine pipe (1) that, once the latter has been connected to the fixed structure (3), the third attachment point is at the level of the seabed (7).
9. 9. Connecting method according to the preceding claim, wherein the riser (8, 9) is connected to the fixed structure (3, 5) by connecting members (12) after formation of the bent portion (10, 11).
10. 10. Submarine pipe comprising, once connected to at least one fixed structure (3, 5), a main portion (6) resting on the seabed (7) and at least one riser (8, 9) which are connected to each other by a bent portion (10, 11), characterized in that bent portion (10, 11) forms an integral part of the submarine pipe (1) and is produced according to the connecting method as defined in one of claims 6 to 9.