SYSTEM FOR IMPROVING FLEXIBILITY OF RISER SUPPORTS IN STATIONARY PRODUCTION UNITS AND INSTALLATION METHOD

Abstract

The present invention addresses to a system consisting of one or more pipes of low flexural rigidity (upper and intermediate extension pipes), connected to a thicker pipe section (lower extension pipe) by means of a varied cross-section pipe (conical profile) and further an adapter shaped like a helmet of a bend stiffener of a flexible riser, to enable, without operational losses, the use of rigid risers in Stationary Production Units (SPUs) initially designed to receive only flexible risers, therefore not having specific supports for rigid risers. The low flexural rigidity of the pipe is achieved through the correct selection of specific materials, preferably by using a titanium alloy that has a low modulus of elasticity and a high yield strength compared to steel.

Claims

1. A system for flexibilization of riser support in stationary units, comprising an upper I-tube (15), a lower I-tube (13), a bell mouth (7), an adapter helmet (5), and characterized in that it comprises an upper extension pipe (1), an intermediate extension pipe (2), a lower extension pipe (3) and a varied cross-section pipe (4).

2. The system according to claim 1, characterized in that the upper extension pipe (1) is positioned at the upper end of the system and has a lower flange that connects to the section of intermediate extension pipe (2).

3. The system according to claim 2, characterized in that the number and length of sections of the intermediate extension pipe (2) depend on the distance between the upper I-tube (15) and the lower I-tube (13).

4. The system according to claim 1, characterized in that the lower end of the intermediate extension pipe (2) connects to the section of lower extension pipe (3).

5. The system according to claim 1, characterized in that the section of the lower extension pipe (3) promotes a curvature (flexion) inside the adapter helmet (5).

6. The system according to claim 1, characterized in that the extension pipes (1), (2) and (3) are connected to each other by means of compact type flanges (6), or circumferential welds.

7. The system according to claim 1, characterized in that the lower end of the lower extension pipe (3) is connected to a stress joint or flexible joint (10), replacing the varied cross-section pipe (4).

8. An installation method of the system for flexibilization of risers according to the inventive concept presented in claim 1, characterized in that there are the following steps: Fixing the adapter (5) to the top tube (1) by means of a collar containing fusible cables (8); Starting the pull in procedure of the set of extension pipes (1, 2 and 3) by the platform winch cable passing inside the lower I-tube (13) and through the bell mouth (7); Locking the adapter helmet (5) whose weight will be supported by Dogs (14); Continuing to slide the set of extension pipes (1, 2 and 3) inside the adapter helmet (5) and bell mouth (or multifunctional bell mouth) (7) until its top end reaches the upper I-tube (15); Assembling a support (9) around the flange of the upper extension pipe (1), connecting it to the vessel piping through a top flange (11).

9. The system according to claim 3, characterized in that the lower end of the intermediate extension pipe (2) connects to the section of lower extension pipe (3).

10. The system according to claim 4, characterized in that the section of the lower extension pipe (3) promotes a curvature (flexion) inside the adapter helmet (5).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be described in more detail below, with reference to the attached figures which, in a schematic way and not limiting the inventive scope, represent examples of the same. In the drawings, there are:

[0019] FIG. 1 illustrates the state-of-the-art rigid riser receptacle;

[0020] FIG. 2 illustrates the parts that make up the stresses in the state-of-the-art flexible riser support system;

[0021] FIG. 3 illustrates the Multifunctional Bell Mouth (MFBM) Support of the state of the art;

[0022] FIG. 4 illustrates the components of the system of the present invention;

[0023] FIG. 5 illustrates the embodiment of the present invention;

[0024] FIG. 6 illustrates the attachment of the adapter helmet.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Preliminarily, it should be emphasized that the description that follows will be based on the preferred embodiments of the invention. As will be apparent to anyone skilled in the art, however, the invention is not limited to these particular embodiments, but rather to the scope of the claims.

[0026] The present invention, as shown in FIG. 4, addresses to a top rigid riser with low flexural rigidity, an upper extension pipe (1) and an intermediate extension pipe (2) for the installation in an interface system of flexible risers connected to a thicker tube section of the lower extension pipe (3), by means of a varied cross-section pipe (4) with a conical profile and further an adapter with an adapter helmet shape (5) of a flexible pipe, to enable, without operational losses, the use of rigid risers in Stationary Production Units (SPUs) initially designed to receive only flexible risers, therefore not having specific supports for rigid risers.

[0027] FIG. 1 illustrates the state-of-the-art receptacle with rigid riser, highlighting the use of a flexible joint (10). FIG. 2 illustrates the two parts, one upper and one lower, which make up the segmented stresses respectively in tension (upper part) and bending moment (lower part) in the support system of flexible risers of the state of the art. There should be highlighted in this arrangement the use of a bend stiffener (17).

[0028] Before the pull in operation, transferring the tube to the platform, the adapter helmet (5) will be attached to the top of the tube by means of a collar containing fusible cables (8), as shown in FIG. 6. During the pull in operation, the set of system tubes is pulled by the platform winch cable (12), passing inside the lower I-tube (13) and bell mouth (7) (or MFBM), illustrated in FIG. 3. The adapter helmet (5) will enter the bell mouth (7), where it will be locked with its weight supported by Dogs (14) exactly as in a pull in of flexible pipes. The set of pipes (1, 2 and 3) continues to slide inside the adapter helmet (5) and (conventional/Multifunctional) bell mouth (7) until its top end reaches the upper I-tube (15), see FIG. 5. When this occurs, a support (9) (hang-off) is mounted around the top flange (11) for fixing the tube (16) to the support (9) (hang-off), which surrounds the connector of riser (18) (end-fitting). This support (9) is similar to the support system of a flexible pipe.

[0029] During the service life of the riser, the lower extension pipe (3) will work inside the Bell Mouth (7) and the lower I-tube (13). Its function is to allow a smooth curvature through the transition of flexural rigidity. In this way, the upper extension pipe (1) and the intermediate extension pipe (2), preferably made of titanium and located just above the conical section of this section, support mainly an axial load. In summary, the low flexural rigidity promoted by the selection of materials and the external diameter transition profile of the extension pipes (1, 2 and 3) of the proposed configuration allow a transfer operation from rigid pipes to the SPU similar to the transfer of a flexible riser, in support for the latter. In addition, the present solution allows a lifetime in service where the tensile and bending moment loads exerted on the upper I-tube (13) and lower I-tube (15) are uncoupled. We can mention as additional advantages the technology able to receive the flexible joint (10) and/or a stress joint (not shown), the selection of materials that allows the use of material immune to CO.sub.2 stress corrosion and the installation procedure similar to the ones used for conventional flexible pipes.

[0030] In this way, the present invention, given its embodiment, is available to be applied in Stationary Production Units (SPUs), with the primary function of supporting rigid risers in an interface initially designed to receive only flexible risers and have the following components: [0031] upper extension pipe (1); [0032] intermediate pipe extension (2); [0033] lower extension pipe (3); [0034] varied cross-section pipe (4); [0035] adapter helmet (5); [0036] upper I-tube (15); [0037] lower I-tube (13); [0038] bell mouth (7); [0039] pipe interconnection fittings, flanges (6).

[0040] The system presents a very simple interconnection. The section of upper extension pipe (1) is the pipe section positioned at the upper end of the system. This pipe has a flange at the top that will be used to connect the platform piping, and a lower flange that will be connected to the intermediate extension pipe (2). The profile of these tubes is very similar and therefore they were not differentiated in FIG. 4. The number of intermediate extension pipes (2) depends on the length between the upper I-tube (15) and the lower I-tube (13), in addition to limitations in length that are characteristic of the manufacturing process adopted to obtain the pipes (1) and (2). The lower end of the intermediate extension pipe (2) is connected to the lower extension pipe (3), which is the component responsible for promoting a smooth curvature of the tube inside the adapter helmet (5). The extension pipes (1), (2) and (3) are connected by means of flanges (6) of the compact type, or through circumferential welds, as illustrated in FIGS. 4 and 5. The lower end of the lower extension pipe (3) is connected to a varied cross-section pipe (4), or to a stress joint, or to a flexible joint (10), as it occurs for specific designs.

[0041] The sequence for installing the rigid riser to the SPU, considering the new elements brought by the invention, must be: [0042] Fixing the adapter helmet (5) to the upper extension pipe (1) by means of a collar containing fusible cables (8); [0043] Starting the pull in procedure of the set of extension pipes (1, 2 and 3), already coupled together by means of flanges or welds, by the platform winch cable passing inside the lower I-tube (13) and through the bell mouth (7); [0044] Locking the adapter helmet (5), whose weight will be supported by Dogs (14); [0045] Continuing to slide the set of extension pipes (1, 2 and 3) inside the adapter helmet (5) and through the bell mouth (or multifunctional bell mouth) (7) until its top end reaches the upper I-tube (15), wherein, in this moment, the lower extension pipe (3) due to its larger diameter locks onto the adapter helmet (5); [0046] Assembling a support (9) around the flange of the upper extension pipe (1), and connecting the same to the vessel piping through a top flange (11).

[0047] The proposed method is not restricted to the above embodiment, and may have small procedural variations according to the accessory elements.