DEVICE FOR CONNECTING A SUBMARINE PIPELINE TO A FIXED STRUCTURE AND ASSOCIATED CONNECTION PROCEDURE.

Abstract

The invention comprises a submarine pipeline (1) consisting of a main section (6) resting on the seabed (7) and connected to two riser pipes (8, 9) by means of elbow sections (10, 11). These sections form an integral part of the submarine pipeline (1) and are created by controlled curvature of the submarine pipeline (1) during its connection to the fixed structures (3, 5). This curvature is achieved by a connection method according to the invention in which tensioning means are attached to one end (2, 4) of the submarine pipeline (1) to connect it to the fixed structure (3, 5) and to a second coupling point of the submarine pipeline (1) located at a distance from the lower end equal to or greater than the length of the riser pipe (8, 9). The tension exerted on the pipeline by the tensioning means allows the desired curvature to be obtained.

Description

DEVICE FOR CONNECTING A SUBMARINE PIPELINE TO A FIXED STRUCTURE AND ASSOCIATED CONNECTION PROCEDURE The present invention relates to the connection of a pipeline to a fixed structure, in particular, for the connection of offshore facilities for the production or export of effluents, such as oil or gas, to each other, with treatment facilities for these effluents or terminals for the export or import of treated effluents. The invention relates more specifically to the connection of a rigid-type underwater pipeline to a fixed structure, which may be a gravity or thrust platform, to transport effluents to or from this fixed structure at a distance that may vary from a few meters to a few kilometers or even tens of kilometers. The invention applies to offshore hydrocarbon production facilities, but more generally it also applies to the transport of any effluent (semi-liquid, liquid, or gaseous) produced or injected by offshore facilities. Such facilities require the surface connection of a subsea pipeline to any installation that enables, for example, the production, injection, treatment, pumping, or compression of the effluent and that is located in a fixed structure, such as a wellhead. Typically, the subsea pipeline rests on the seabed at a depth that can vary from a few tens of meters to approximately two hundred meters, and it is connected to the fixed structure at or near the surface by one end of a riser attached to the subsea pipeline by a bent section.The invention applies more particularly to this angled section that connects the riser to the portion of the pipeline resting on the seabed. The subsea pipeline has two ends, each of which can be connected to a fixed structure. A similar configuration is used for connecting these two ends of the subsea pipeline. The laying of the subsea pipeline begins at one end and ends at a second end, also called the abandonment end, as it is the end that is left in the sea once the laying is complete. There are many solutions for connecting a rigid underwater pipeline to a fixed structure such as a platform, each with a different technique for making the transition between the part of the underwater pipeline that rests on the seabed and the riser tube of the pipeline that rises to the surface, as shown below. The most conventional connections between a subsea pipeline and a riser involve starting or leaving the end of the rigid pipeline on the seabed, a short distance from the platform to which it will be connected. A riser is attached to the structure to be connected between the surface and the seabed. Then, with the help of divers or underwater robots, a section of connecting pipe called a connecting sleeve is deployed between the end of the rigid pipeline lying on the seabed and the lower end of the pre-installed riser. This connecting sleeve can be either flexible (in the form of a section of flexible pipe) or rigid (in the form of steel pipes welded or flanged together). As an alternative to the connection sleeve described above, a long section of flexible (adaptable) pipe can be coupled, on one side, to the end of the rigid underwater pipe resting on the seabed and, on the other side, directly to the fixed structure on the surface or at shallow depths of the water. To connect subsea pipelines in shallow waters (typically less than 50 m), a rigid riser method is sometimes used, launched from the subsea pipeline laying platform. The laying platform is, in practice, a barge equipped for laying subsea pipelines and, in particular, a lifting crane. This method involves fabricating the riser simultaneously with the pipeline on the laying platform, including the elbow or bend between the subsea pipeline and the riser, and then transferring it to the platform using the laying platform's lifting crane. This method is limited by the available height under the crane hook and the minimum distance between the laying platform and the platform when transferring the riser. For this reason, this connection technique is practically reserved for very shallow depths, i.e., less than 50 m. For very deep water, connections of rigid subsea pipelines to structures, usually floating or laid, are made directly using rigid pipes called catenaries. These direct couplings are possible thanks to surface-mounted swivel joint systems that adapt to the relative movements of the pipeline and the platform. This swivel joint method can also be considered for fixed structures, although its cost is generally prohibitive. All known connection solutions involve either welding or underwater mechanical couplings that require very costly interventions by saturation divers or underwater robots, or very expensive materials such as flexible pipe sections, automatic connectors or flexible joints. US Patent 3,531,941 describes a subsea pipeline bending procedure in which the pipe is bent by tension generated by a winch on a cable. The cable is attached to the subsea pipeline by a bending guide. The pipe bend is achieved by the combined action of the tension generated by the winch and the shape of the bending guide. Throughout the entire subsea pipeline laying operation, including pipe bending, the pipe end is attached to the fixed structure by a hinged flange. During pipe bending, the pipe is simultaneously locked (i) in the bending guide groove due to the pressure exerted by the groove on the portion of the pipe to be bent and (ii) at the level of its attachment to the fixed structure by a clamp mounted on a pivot that allows rotation in one plane.To prevent damage to the pipe between these two fixed points during the bending operation, US patent 3,531,941 provides for a clamp with jaws that, when tightened, block the pipe's movement, but are wide enough to allow the pipe to slide if necessary; this would necessarily entail a complex design. Without such a system that allows the pipe to slide through the clamp, compression can develop between the point of attachment to the fixed structure and the bending guide, potentially resulting in improper pipe deformation. The present invention aims to propose a new type of direct connection between a submarine pipeline and a fixed structure that does not require couplings by divers or robots, flexible pipe sections, ball joint systems at the end of the riser pipe, or bending guides during installation, and that is applicable to water depths ranging from tens of meters to typically two hundred meters. To that end, the invention relates, in a first aspect, to a device for connecting a submarine pipeline to a fixed structure. Once connected, the pipeline comprises a main section suitable for placement on the seabed and at least one riser tube joined together by a bent section. According to the invention, the connection device includes connecting elements located on the fixed structure, suitable for securing the riser tube to it, comprising at least an upper and a lower connecting element; laying means suitable for deploying the submarine pipeline to connect it to the fixed structure; and tensioning means attached to the fixed structure and suitable for applying controlled mechanical tension at at least two distinct coupling points of the submarine pipeline during its deployment to form the bent section before connection to the fixed structure. By directly laying the underwater pipeline, the elbowed section that forms the transition between the riser and the main section of the underwater pipeline eliminates the need for deep-water interventions and the use of expensive, specialized materials to connect an underwater pipeline to a fixed offshore structure. This configuration of the underwater pipeline allows the elimination of intermediate joints and special parts needed to connect or form the riser pipe, which are both weak points in terms of mechanical strength and potential leak points. Preferably, in the connection device according to the invention, a first coupling point is located at one end of the underwater pipe adapted to connect to the fixed structure and a second coupling point is located at a distance from the end of the underwater pipe greater than the distance separating this end of the underwater pipe and the lower connection element fixed to the fixed structure. Advantageously, in the connection device according to the invention, the tensioning means comprise at least a first cable and a second cable mechanically attached, on the one hand, to the fixed structure and, on the other hand, to the first and second coupling points, respectively, of the underwater pipeline. This connection device results in an assembly of simple means that are operated and implemented from the surface without requiring the intervention of specialized divers or robots. Preferably, in the connection device according to the invention, the tensioning means comprise a third cable attached to a third coupling point of the underwater pipeline located at a sufficient distance from the end of the underwater pipeline so that once the pipeline has been laid on the seabed, the third coupling point is at seabed level. Applying tension at various points of the underwater pipeline allows for control of its deformation and thus control of the geometry of the bent section during its formation in situ. Advantageously, in the connection device according to the invention, the tensioning means further comprise at least one pulley suitable for directing the traction exerted by at least one of the cables on the corresponding coupling point of the underwater pipeline. The use of deflector pulleys allows the tension applied to the different coupling points of the underwater pipeline to be controlled from the surface. According to a second aspect, the present invention relates to a method of connecting a submarine pipeline to a fixed structure using laying means. The submarine pipeline has a main section suitable for being laid on the seabed and at least one riser tube joined together by a bent section. The method comprises the following steps: unfolding the submarine pipeline onto the laying means so that it is laid on the seabed; attaching tensioning means to the submarine pipeline, which are connected to the fixed structure to which the submarine pipeline will be connected; laying the submarine pipeline on the seabed; and applying controlled tension to the submarine pipeline with the tensioning means to progressively form the bent section of the submarine pipeline.and connect the riser pipe of the underwater pipeline to the fixed structure by means of connecting elements consisting of at least an upper connecting element and a lower connecting element.; The connection procedure defined above allows for the transition between the main section of the subsea pipeline resting on the seabed and the riser using only the pipeline itself, intervening from the surface without interrupting the subsea pipeline laying operations. It also allows for the implementation of conventional laying methods that do not require the mobilization of specialized equipment such as divers or underwater robots. Advantageously, in the connection procedure according to the invention: a first tensioning means is attached to one end of the underwater pipe to be connected to the fixed structure; a second tensioning means is attached to a second coupling point of the underwater pipe located at a distance from the end of the underwater pipe greater than the distance separating said end from the lower connecting element; a first pull is exerted with the first tensioning means to bring said end of the underwater pipe to the fixed structure at the surface level or at a shallow depth; and a second pull is exerted with the second tensioning means in order to push the underwater pipe against said fixed structure to bend it and thus form the angled part thereof. Preferably, in the connection procedure according to the invention, a third tensioning means is coupled to a third coupling point of the underwater pipeline located at a sufficient distance from the end of the underwater pipeline so that once it is connected to the fixed structure, the third coupling point is at the level of the seabed. This connection procedure allows the implementation of simple means commonly available at underwater pipeline laying sites, which are operated and installed from the surface without requiring the intervention of specialized divers or robots. Advantageously, in the connection procedure according to the invention, the riser pipe is connected to the fixed structure by means of connecting elements after forming the angled part. According to a third aspect, the invention relates to a submarine pipeline that, once connected to at least one fixed structure, comprises a main section resting on the seabed and at least one riser pipe joined together by a bent section. This bent section forms an integral part of the submarine pipeline and is manufactured according to the connection procedure as defined above. By directly bending the subsea pipeline for connection during laying, the integrity of the effluent transport line upstream or downstream of the subsea pipeline is preserved, thus limiting the risk of leaks requiring deep-sea interventions. Maintaining the pipeline's continuity from end to end also allows, if necessary, for the continuity of the pipeline insulation and cathodic protection. Other features and advantages of the invention will be made clear by the following description of non-limiting examples of embodiments of the various aspects of the invention. The description refers to the accompanying figures, which are also provided as non-limiting examples of embodiments of the invention: [Fig. 1] Figure 1 represents a schematic view of an underwater pipeline connected at both ends to fixed structures; [Fig. 2] Figure 2 illustrates a schematic view of a first stage of the connection of the initiation end of a subsea pipeline; [Fig. 3] Figure 3 illustrates in a schematic view a second phase of the connection of the initiation end of a subsea pipeline; [Fig. 4] Figure 4 represents a schematic view of a third stage of the connection of the initiation end of a subsea pipeline; [Fig. 5] Figure 5 illustrates in a schematic view a first phase of the connection of the abandonment end of a subsea pipeline; and [Fig. 6] Figure 6 illustrates in a schematic view a second phase of the connection of the abandonment end of a subsea pipeline. Hereafter, the invention is described in the context of a rigid subsea pipeline intended to transport petroleum effluent from an offshore well to an offshore processing or export terminal. This context for implementing the invention is described solely to facilitate understanding of the invention and is in no way intended to limit it. The same applies to all other examples of implementing the various features of the invention, which are described hereafter for illustrative purposes only. Figure 1 [Fig. 1] represents a rigid underwater pipeline 1 that has two types of connection. On one hand, a first connection of a first end 2 of the rigid submarine pipeline 1 to a first fixed structure 3 on the starting side of the pipeline. The first end 2 corresponds to the direction of pipeline laying. The laying of the submarine pipeline 1 begins at the first end 2. Furthermore, a second connection from a second end 4 of the submarine pipeline 1 to a second fixed structure 5 on the abandonment side of the submarine pipeline 1. The laying of the submarine pipeline 1 is completed by the second end 4 and it is this second end 4 of the submarine pipeline 1 that is abandoned once the laying operations are completed. In the rest of the description, ordinal numeral adjectives such as first, second, or third should be interpreted with respect to the direction of laying of the submarine pipeline 1. The underwater pipeline 1, once connected to the first and second fixed structures 3 and 5, has a main pipe section 6 laid on the seabed 7, a first riser pipe 8 connected to the first fixed structure 3, and a second riser pipe 9 connected to the second fixed structure 5. The first and second riser pipes 8 and 9 are joined, respectively, to the main pipe section 6 by a first elbow section 10 and a second elbow section 11. The underwater pipeline 1 is connected, at each of its two ends 2 and 4, to a fixed structure 3 or 5 without the insertion of an intermediate coupling piece, such as a sleeve, or the insertion of a bent, angled, or flexible section into the underwater pipeline line joining the two fixed structures 3 and 5, unlike the conventional techniques described above. The connection procedure described below allows for the formation of a curved transition between the main section 6 of the rigid subsea pipeline 1, laid on the seabed 7, and a face or edge 13 or 14 of the fixed structure 3 or 5 to which the riser 8 or 9 of the subsea pipeline 1 is connected. Indeed, fixed offshore structures are generally supported by an assembly of legs resting or anchored on the seabed, generally forming a regular polyhedron with three or four faces that rises from the seabed to the surface. Therefore, the riser 8 or 9 can be connected, as required, to one of the faces or edges 13 or 14 of the polyhedron formed by the legs of the fixed structure 3 or 5. The first and second risers 8 and 9 resulting from the formation of The first and second angled sections 10 and 11 are rigidly fixed to the fixed structures 3 and 5 by means of connecting elements 12 to a water depth such that the free portion below (in the form of a chain) can withstand the residual forces due to the external environment (in particular, waves and current) and the forces due to the circulation of effluents inside the subsea pipe 1. The connecting elements 12 can be clamps that lock around the riser pipe. They comprise an upper connecting element (closest to the surface) and a lower connecting element 20 (closest to the seabed). Depending on the length of the riser pipe 8 or 9 to be connected to the fixed structure 3 or 5, one or more intermediate connecting elements 12 may be required. The connection procedure allows the first end 2, with respect to the direction of laying, to bring this first end 2 of the subsea pipeline 1 to the surface, and the second end 4 to bring it close enough to the surface for coupling to be performed at a depth of less than 50 m, without resorting to saturation diving techniques. This shallow coupling can be performed, for example, by means of a pipe extension 28 that is rigidly fixed to the same face or edge 14 of the second fixed structure 5. Figures 2, 3 and 4 illustrate different phases of the procedure for connecting the submarine pipeline 1 to the first fixed structure 3 corresponding to the first end 2 by which the laying of the submarine pipeline 1 is initiated by means of laying means 15 which may be floating. As illustrated in Figure 2 [Fig. 2], a first, a second, and a third cable 16, 17, and 18 are respectively coupled to three winches (not shown) mechanically secured to the fixed structure 3. Instead of a winch / cable assembly, according to the invention, any other means can be implemented that allows applying a tension of similar intensity to that of a winch and bringing the underwater pipe 1 closer to the fixed structure 3 to the required distance or adjusting the length of these cables to the required length. First, the first, second and third cables 16, 17 and 18 are deployed from the first fixed structure 3, passing, if necessary but not necessarily, through deflector pulleys 19, and are transferred to the laying means 15 to couple to the appropriate part of the subsea pipeline 1 before it leaves the laying means 15. From the laying means 15, the first cable 16 is attached to the first end 2 of the underwater pipeline 1. Next, the laying means 15 move away from the first fixed structure 3 in the laying direction of the underwater pipeline 1. When the laying means 15 are sufficiently far from the first fixed structure 3, the second cable 17 is coupled at a distance D1 from the first end 2 of the underwater 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 element 20 to the first face or edge 13 of the first fixed structure 3 once the underwater pipe 1 has been installed. Next, the third cable 18 is attached to the underwater pipeline 1 from the laying means 15 at a sufficient distance from the first end 2 so that, once the pipeline is installed, the attachment point of the third cable 18 is at the level of the seabed 7.During the connection operation of the submarine pipeline 1 in the initial phase of its laying, the pipeline is assembled from the laying means 15 until these are sufficiently far from the first fixed structure 3 for the submarine pipeline 1 to touch the seabed 7 at the level of the catenary's belly. As an alternative to deploying the submarine pipeline 1 by assembling pipeline sections onto the laying means 15, the pipeline can be unrolled during the progression of the laying means 15. As the pipeline sections are assembled onto the laying means 15, winches secured to the first fixed structure 3 pull cables 16, 17, and 18 to control the cable length between the first fixed structure 3 and the cable coupling points on the pipeline.One of the winches exerts a pull F on the first cable 16 to bring the first end 2 of the submarine pipeline 1 to the surface. The first, second, and third submarine cables 16, 17, and 18 are coupled from the laying means 15 to the submarine pipeline 1, respectively, by a first anchor point at the pipeline head, a first submarine clamp 21, and a second submarine clamp 22. As depicted in Figure 3 [Fig. 3], once the first end 2 is at the desired height and in position to connect to the first fixed structure 3, the winch driving the first cable 16 stops while the winches driving the second and third cables 17 and 18 continue to exert a pull on the underwater pipe 1 towards the first fixed structure 3 so that the top of the underwater pipe 1 located between the first end 2 and the third (and last) underwater clamp 22 is pushed as close as possible to the first face or edge 13 of the first fixed structure 3.The runs of the first, second, and third cables 16, 17, and 18 are adjusted to maintain constant tension on the underwater pipeline 1 at the level of the laying means 15, and to control the formation of the bend in the underwater pipeline 1 between the lower connecting element 20 on the first face or edge 13 of the first fixed structure 3 and the seabed 7, which will form the first elbowed part 10 joining the main part 6 of the underwater pipeline 1 to the first riser tube 8. During this operation of obtaining the controlled bend of the underwater pipeline 1, the relative position of the laying means 15 with respect to the first fixed structure 3 and the length of the underwater pipeline 1 deployed from the laying means 15 are also adjusted. As illustrated in Figure 4, once the first bent section 10 is fully formed, the first riser tube 8 is attached to the fixed structure 3 by means of the connecting elements 12. These can be closed automatically or by various means, such as divers or remotely operated vehicles (ROVs) that operate at shallow depths and whose cost is substantially lower than that of operations at greater depths (below 50 meters). Once the connecting elements are closed, the first and second cables 16 and 17 can be detached from the underwater pipeline 1. The third cable 18 remains attached until a sufficient length of underwater pipeline 7 has been laid on the seabed to allow it to absorb, by friction, the laying tension applied by the laying equipment 15 to the underwater pipeline 1 during the remainder of its deployment by assembly or unwinding.Next, it can be uncoupled from the underwater pipeline 1 either from the surface, or with the help of an ROV at seabed level 7. The bent submarine pipeline 1 is inserted into the plastic sector. Monitoring the tensions and travel of the first, second, and third cables 16, 17, and 18, and the position of the laying equipment 15 during the bending operation prevents the pipeline from forming a plastic hinge at one of the second or third submarine clamps 21 and 22, or at seabed level 7. For this purpose, the tension and travel profiles of the cables 16, 17, and 18 are defined through preliminary analyses using specialized software. A control system ensures the monitoring of the position of the laying equipment 15 and the tensions applied to the first, second, and third cables 16, 17, and 18. Figures 5 and 6 illustrate different phases of the procedure for connecting the second end 4 of the underwater pipeline 1 to the second fixed structure 5. The second end 4 corresponds to the end through which the underwater pipeline 1 is abandoned by the laying means 15 when the laying of the underwater pipeline 1 has been completed. As illustrated in Figure 5 [Fig. 5], a fourth cable 23 and a fifth cable 24 are coupled to two winches (not shown) mechanically secured to the second fixed structure 5. The fourth and fifth cables 23 and 24, coupled to two winches (or any other means that allows applying the required tension and / or adjusting the length of these cables to the required length) are deployed from the second fixed structure 5, passing, if necessary, through deflector pulleys 19, and are transferred to the laying means 15 (barge or ship) to be coupled to the underwater pipeline 1. The fourth cable 23 is attached to the second end 4 of the underwater pipe 1. The fifth cable 24 is attached at a distance D2 from the second end 4 of the underwater pipe 1. The distance D2 is defined so that it is slightly greater than the distance separating the second end 4 of the underwater pipe 1 and a lower connecting element 20 on the second face or edge 14 of the second fixed structure 5 once the underwater pipe 1 is installed. Additionally, a slip plane 25 can be optionally pre-installed on the second face or edge 14 of the second fixed structure 5 to better control the trajectory of the second end 4 of the pipe during the bending operation between the second riser pipe 9 and the main part 6 of the subsea pipe resting on the seabed 7. The total length of the underwater pipeline 1 is adjusted as it approaches the second fixed structure 5 to which it is to be connected, with respect to the relative position of the second fixed structure 5 and the laying means 15 at the time of the transfer and based on the desired final elevation of the second end 4 after the formation of the second bent part 11. RnnoLn / Lznz / B / YiAi Once the length of the underwater pipe has been adjusted, the second end 4 of the pipe is coupled to the fourth cable 23 and to a lightening buoy 26 temporarily attached to the underwater pipe 1 and intended to contain the trajectory of the second end 4 in a nearly horizontal plane during its transfer from the laying means 15 to the second fixed structure 5. This transfer operation allows the transfer of horizontal tension to the underwater pipeline 1 from an abandonment cable 27 deployed from the laying means 15 and the fourth cable 23 deployed from the second fixed structure 5. Once the tension transfer operation is completed, the lightening buoy 26 is detached from the second end 4 of the underwater pipeline 1, as well as the abandonment cable 27. The underwater pipeline 1 is then ready to be bent in a controlled manner from the second fixed structure 5 without the intervention of the laying means 15 as shown in figure 6 [Fig. 6]. To control the bend in order to form the second bent part 11 that connects the second riser tube 9 to the main part of the pipe 6 (of which it is an integral part), the second end 4 is lowered along the second fixed structure 6 on the sliding plane 25 by slowly unwinding the fourth cable 23 to keep it in tension, and winding the fifth cable 24 to push the part of the underwater pipe 1 that will become the second riser tube 9, towards the second face or edge 14 of the fixed structure 5. The bend is formed at least partly by the weight of the underwater pipe 1 itself and by the force applied by the fifth cable 24. Once the fourth cable 23 has lowered the second end 4 to the required height, the second bent section 11 is formed, and the second riser tube 9 is attached to the second face or edge 14 of the second fixed structure 5 using the connecting elements 12. As with the connection to the first fixed structure 3, the connecting elements 12 can be closed by any means (automatic, by divers, or using an ROV). Once these connecting elements are closed on the second riser tube 9, the fourth and fifth cables 23 and 24 can be detached from the underwater pipe 1. As with the first bent part 10, the pipe thus curved to form the second bent part 11 is introduced into the plastic sector. Control of the tensions and runs of the fourth and fifth cables 23 and 24 during the bending operation prevents the pipe from forming a plastic hinge in the subsea pipe 1 at the coupling points of cables 23 and 24 or at seabed level 7. For this purpose, the tension and run profiles of the fourth and fifth cables 23 and 24, as well as the abandonment cable 27, are defined by preliminary analyses using dedicated software programs. A control system ensures the position of the laying equipment 15 and the tensions applied to the fourth and fifth cables 23 and 24, as well as to the abandonment cable 27. To complete the connection of the second end 4 to the second fixed structure 5, the pipe extension 28 is coupled to the second end 4 to reach the surface. The depth of the second end 4 of the underwater pipe 1 is sufficiently shallow to allow divers to make the connection without a saturation system, making it more economical than conventional solutions at water depths greater than 50 m. Although the preceding description focuses on specific aspects of the invention in the context of connecting a simple rigid submarine pipeline, it could be implemented in other configurations, particularly for thermally insulated submarine pipelines or onshore pipelines where bends are necessary due to the pipeline's topology, which must conform to the terrain or the different levels of the facilities to be connected. As mentioned in the introductory section, the pipeline can be used to transport hydrocarbon effluents from the production or extraction area to a treatment and / or export facility. Furthermore, the pipeline implemented according to the invention can be used to inject effluents (water or gas) into the subsurface from a treatment facility to an offshore or onshore injection zone.

Claims

CLAIMS 1. A device for connecting to a fixed structure (3, 5) a submarine pipeline (1) comprising, once connected, a main part (6) suitable for being laid on the seabed (7) and at least one riser pipe (8, 9) joined together by an angled part (10, 11), characterized in that it comprises: - connection elements (12) located on the fixed structure (3, 5), suitable for fixing the riser pipe (8, 9) to the same and comprising at least an upper connection element and a lower connection element (20); - laying means (15) suitable for deploying the submarine pipeline (1) to connect it to the fixed structure (3, 5);and - tensioning means (16,17,18, 23, 24) attached to the fixed structure (3, 5) and suitable for exerting controlled mechanical tension on at least two distinct coupling points of the subsea pipeline (1) during the deployment of said subsea pipeline (1) to form the bent part (10, 11) prior to the connection of said subsea pipeline (1) to the fixed structure (3, 5).; 2. Connection device according to the preceding claim, wherein a first coupling point is located at one end (2, 4) of the underwater pipe (1) adapted to connect to the fixed structure (3, 5) and a second coupling point is located at a distance (D1, D2) from said end (2, 4) of the underwater pipe (1) greater than the distance separating said end (2, 4) of the pipe from the lower connection element (20).

3. Connection device according to the preceding claim, wherein the tensioning means (16, 17, 18, 23, 24) comprise at least a first cable (16, 23) and a second cable (17, 24), mechanically attached, on one side, to the fixed structure (3, 5) and, on the other side, to the first and second coupling points, respectively, of the underwater pipeline (1).

4. Connection device according to one of claims 2 or 3, wherein the tensioning means (16, 17, 18, 23, 24) comprise a third cable (18) attached to a third coupling point of the underwater pipe (1) located at a sufficient distance from said end (2) of the underwater pipe (1) so that once it has been laid down on the seabed (7) the third coupling point is at the level of the seabed (7).

5. Connection device according to one of claims 3 or 4, wherein the tensioning means (16, 17, 18, 23, 24) further comprise at least one pulley (19) suitable for directing the tension transmitted by at least one of the cables (16, 17, 18, 23, 24) onto the corresponding coupling point of the underwater pipeline (1).

6. A method for connecting a submarine pipeline (1) to a fixed structure (3, 5) using laying means (15), the submarine pipeline (1), once connected, comprising a main part (6) suitable for being laid on the seabed (7) and at least one riser pipe (8, 9) joined together by an angled part (10, 11), said method comprising the following steps: - unfolding the submarine pipeline (1) onto the laying means (15) so that it is laid on the seabed (7); - attaching to the submarine pipeline (1) the tensioning means (16, 17, 18, 23, 24) connected to the fixed structure (3, 5) to which the submarine pipeline (1) is to be connected; - laying the submarine pipeline (1) on the seabed (7); - exert a controlled traction on the underwater pipe (1) with the tensioning means (16, 17, 18, 23, 24) to progressively form the bent part (10, 11) of the underwater pipe (1);and - connecting the riser pipe (8, 9) of the underwater pipeline (1) to the fixed structure (3, 5) by means of connecting elements (12) comprising at least one upper connecting element and one lower connecting element.; 7. Connection method according to the preceding claim, wherein: a first tensioning means (16, 23) is coupled to an end (2, 4) of the underwater pipe (1) to be connected to the fixed structure (3, 5); a second tensioning means (17, 24) is coupled to a second coupling point of the underwater pipe (1) located at a distance (D1, D2) from said end (2, 4) of the underwater pipe (1) greater than the distance separating said end (2, 4) from the lower connecting element (20); a first pull is exerted by means of the first tensioning means (16, 23) to bring said end (2, 4) of the underwater pipe (1) to the fixed structure (3, 5) at the surface level or at shallow depth; and a second traction is exerted by means of the second tensioning means (17, 24) in order to push the underwater pipe (1) against said fixed structure (3, 5) to bend it and thus form the bent part (10, 11) thereof.

8. Connection method according to the preceding claim, wherein a third tensioning means (18) is coupled to a third coupling point of the underwater pipe located at a sufficient distance from the end (2) of the underwater pipe (1) so that once it is connected to the fixed structure (3), the third coupling point is at the level of the seabed (7).

9. Connection method according to the previous claim, wherein the riser tube (8, 9) is connected to the fixed structure (3, 5) by means of connecting elements (12) after the formation of the angled part (10, 11).

10. Submarine pipeline comprising, once connected to at least one fixed structure (3, 5), a main part (6) resting on the seabed (7) and at least one riser pipe (8, 9) joined together by an angled part (10, 11), characterized in that the angled part (10, 11) forms an integral part of the submarine pipeline (1) and is made according to the connection procedure as defined in one of claims 6 to 9.

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