TOP CONNECTION ARRANGEMENT FOR A SUBMARINE RISER, SURFACE INSTALLATION AND METHOD OF CONNECTING A SUBMARINE RISER TO A SURFACE INSTALLATION

Abstract

SUBMARINE RISER UPPER CONNECTIONS. The present invention relates to a top connection arrangement for a submarine riser comprising a pivot or joint combination, disposed between, and fluidly connecting, upper and lower sections of rigid pipe. The pivot combination comprises an upper spherical joint around which the upper pipe section is pivotable. A lower joint, being a flexible joint or a tapered tension joint to which the lower pipe section is attached to the spherical joint in series. A sleeve is attached to the spherical joint and encloses the upper pipe section to allow limited pivoting movement of that pipe section around the spherical joint. The sleeve may seat on the bell mouth of an I or J pipe of a surface installation, or may be omitted if the lower joint is seated on a suspended formation. A locking mechanism is capable of locking the spherical joint and thus preventing pivoting movement of the upper pipe section.

Description

1 / 20 TOP CONNECTION ARRANGEMENT FOR A SUBMARINE RISER, SURFACE INSTALLATION AND METHOD OF CONNECTING A SUBMARINE RISER TO A SURFACE INSTALLATION

[001] The present invention relates to subsea risers (riser pipes) used in the offshore oil and gas industry to transport hydrocarbons and sometimes other fluids from the seabed to the surface. Risers can also be used reciprocally to transport other fluids, energy and data from the surface to the seabed.

[002] Riser configurations include those known in the art as suspended, steep, slow-wave, and weight-distributed risers. Such risers are normally suspended between a floating upper support and the seabed, the upper support being a surface installation such as a platform, a floating production unit (FPU), or an FPSO (floating production, storage and offloading) vessel.

[003] A typical suspended riser consists of a rigid pipe that is freely suspended like a catenary from the surface installation. More conventionally, such a riser is made of steel - thus being known in the art as a steel catenary riser or SCR.

[004] Those skilled in the art know that nominally rigid pipes are not devoid of flexibility. In fact, SCRs exploit the bending behavior of rigid pipes in the elastic domain. However, although they have flexibility, 'rigid' pipes do not fit the definition of 'flexible' pipes as understood in the art.

[005] Conventional rigid pipes used in the subsea oil and gas industry are specified in the American Petroleum Institute (API) Specification SL and Recommended Practice 1111. A rigid pipe generally consists of or comprises at least one pipe of Petition 870260033506, dated 10 / 04 / 2026, page 10 / 68 2 / 20 solid steel or alloy steel. However, additional layers of other materials may be added, such as an inner coating layer or an outer coating layer. A rigid pipe may also have a concentric pipe-in-pipe (PIP) structure. Rigid pipe joints are terminated by a bevel, thread, or flange, and are assembled end-to-end by welding, screwing, or bolting them together to form a pipe string or tubing.

[006] On the other hand, flexible pipes used in the subsea oil and gas industry are specified in API Specification 17J and Recommended Practice 17B. The pipe body is composed of a layered composite structure of materials, where each layer has its own function. In particular, flexible pipes, especially bonded ones, comprise layers bonded together, of steel, fabric and elastomer, and are manufactured in short lengths, on the order of tens of meters.

[007] Typically, polymer tubes and casings ensure fluid tightness and thermal insulation, while steel layers or elements provide mechanical strength.

[008] In recent years, the subsea oil and gas industry has begun to adopt rigid pipes made of polymer composite materials in place of steel. Composite pipes have a load-bearing tubular structure, which is primarily made of composite materials. This should be distinguished from pipes with a composite structure, such as the various layered configurations of rigid and flexible pipes, as mentioned above.

[009] Typically, a composite pipe comprises a polymer resin matrix reinforced with fibers, such as glass fibers or carbon fibers. The polymer matrix can be of thermoplastic or thermoset materials. The former results in what is known as Petition 870260033506, dated 10 / 04 / 2026, page 11 / 68 3 / 20 technique as thermoplastic composite pipe or, more simply, thermocomposite pipe (TCP). TCP is classified as a bonded composite pipe.

[0010] A riser typically has negative buoyancy in seawater and is therefore held in tension by its apparent suspended weight. This weight, expressed in the art as upper tension, is suspended from a support structure in a surface installation.

[0011] Figure 1 illustrates a support structure 10 that is cantilevered from the side of an FPSO 12. In the case of an FPSO 12, the support structure 10 generally comprises a lower cantilever 14 and an upper cantilever 16 above, and vertically spaced from, the lower cantilever 14. The vertical spacing between the lower cantilever 14 and the upper cantilever 16 is typically between about 10m and about 30m.

[0012] During installation, a riser is pulled into engagement with the support structure 10 and is then locked to the structure 10 by means of a fatigue-resistant element. Typically, the fatigue-resistant element is a bend reinforcement for flexible risers, or a flexible joint element for rigid risers.

[0013] A conventional installation method involves pulling the upper riser elements, such as a head, connector, bend reinforcement, or tension joint, through a pipe or suspended formation of the supporting structure and then locking the fatigue-resistant element into the pipe or suspended formation. For example, some risers extend along an I-pipe or J-pipe of a supporting structure, depending on the pipe shape.

[0014] The support structure 10 shown in Figure 1 comprises an I-tube 18. The lower part of the I-tube 18 comprises a bell mouth 20 which is inclined vertically to accommodate the operating slope of the riser top. During the pulling operation, as the riser is pulled upward, the I-tube 18 receives a bending reinforcement in the riser. Petition 870260033506, dated 10 / 04 / 2026, page 12 / 68 4 / 20 and locked at the mouth of the bell 20. For other risers, a flexible joint can be fitted to a suspended formation.

[0015] A reel pipe in fluid communication with the top of a riser may be supported and extend between the lower and upper decks. Above the upper deck, the reel pipe connects the riser to the onboard piping of the surface installation, for example, to transport hydrocarbon production fluids from the riser for processing and storage.

[0016] The top of an overhead riser naturally adopts an angle with the vertical when positioned for operation. The supporting structure of the surface installation is designed to accommodate this angle. However, transiently, the top of the riser adopts different or greater angles with the vertical during installation. In particular, the angle of the top of the riser varies during the steps of: pulling; passing and locking onto the pipe, or settling into the suspension; and connecting with the process piping on the topside aboard the surface installation.

[0017] Once installed, a riser will be in motion throughout its operational life. Its movement is driven by multiple inputs arising from sea dynamics, most notably the movement of the surface installation, expressed as heeling, pitching, roll, yaw, and seawater movement caused by currents, tides, and waves. Consequently, the riser is connected at its upper end to the supporting structure by a connecting device that provides some degrees of freedom, examples being a tension joint or a flexible joint or pivot, as described in WO 2010 / 025449.

[0018] The term 'flexible joint' typically designates a particular category of pivot comprising at least one elastomeric support element, which facilitates the rotation of pipe sections. Examples of flexible joints are manufactured and sold by Oil States Petition 870260033506, dated 10 / 04 / 2026, page 13 / 68 5 / 20 Industries and Techlam Hutchinson.

[0019] Such a joint allows the riser to pivot freely relative to the supporting structure around substantially horizontal, mutually orthogonal axes. Thus, as the riser bends along its length under the influence of sea dynamics, the top of the riser can pivot relative to the supporting structure within a downward diverging cone, the vertex of which coincides with the pivoting center of rotation of the joint. In some cases, the riser may also be able to twist or rotate around its longitudinal axis relative to the supporting structure.

[0020] Typically for an SCR, the top connector is a flexible joint or tension joint, which accommodates the tapered angle of the riser on the counter. Both solutions involve a flexible pipe connected to the top of the joint, to transfer fluids to or from the topside processing equipment.

[0021] There is a need to deal with conflicting requirements during the installation and operation of a riser, namely: transient but substantial variations in the bending angle during installation and tension of the riser top; followed by more limited but frequent continuous variations in the bending angle during riser operation. The latter movements generate a variable bending moment in repeated cycles and therefore promote fatigue at the riser top.

[0022] A limited bending angle is sufficient under operating conditions where fatigue is the determining factor. However, a larger bending angle is required for bonding to the rigid support structure of the surface mount. The challenge is to accommodate substantial variations in the bending angle during installation, but without sacrificing fatigue performance during operation.

[0023] In this respect, flexible and rotary joints are well known in the art, to compensate for operational bending at the top of Petition 870260033506, dated 10 / 04 / 2026, page 14 / 68 6 / 20 riser joints, but are less able to accommodate bending angles that may be encountered during installation. On the other hand, joints that can handle larger bending angles generally suffer from inferior fatigue performance.

[0024] A flexible joint often comprises an elastomeric element, as disclosed in US 5269629 or WO 2016 / 028792. On the other hand, WO 06 / 3598 discloses a cardan shaft SCR suspension and BR PI0505400 discloses a spherical swivel as an alternative to a flexible joint. The spherical swivel of BR PI0505400 comprises a hemisphere that can rotate within a complementary seat of a suspended structure.

[0025] US 5865566 shows a typical use of a flexible joint, locked into the inlet or bell mouth of a J-pipe along which the riser extends. Here, the pipe comprises a ball valve to isolate the riser.

[0026] In WO 2009 / 108644, two flexible joints are combined head-to-head. Two flexible joints are also combined in WO 2011 / 008704. This arrangement offers greater bending capacity than a single flexible joint, while maintaining the advantages inherent in flexible joints, notably their fatigue resistance. However, flexible joints are extremely expensive.

[0027] Additional flexibility is often provided by adding a flexible tube, known as a flexible reel, between the upper end of the riser and the topside process piping aboard the surface installation. This is not satisfactory, since flexible pipe is more expensive than rigid pipes; furthermore, flexible pipe is weaker than rigid pipe and is therefore the weakest mechanical link between the riser and the piping of the surface installation. Handling and connecting a flexible piece to the sea along the hull of the surface installation is also a risky operation. Petition 870260033506, dated 10 / 04 / 2026, page 15 / 68 7 / 20

[0028] Alternative arrangements are known for the same purpose as a flexible tube. For example, WO 2016 / 191637 and US 8550171 describe upper riser connections comprising a swivel, typically a flexible joint, placed in a suspended receptacle that is topped by a rigid spool. The rigid spool is shaped to give the spool flexibility to bend along its length, for example, being wound or otherwise bent in a transverse plane. Similarly, KR 20150057685 discloses a shock-absorbing convoluted riser formation in combination with a flexible suspension.

[0029] In BR PI0601788, a tapered joint for fatigue resistance and a flexible joint for bending are combined.

[0030] US 2019 / 032428 places a flexible joint or ball joint between two sections of rigid pipe. However, this arrangement does not offer sufficient flexibility to pull the riser through a wide range of pipes or suspensions. In this respect, flexible joints have limited pivot angles, while ball joints allow for a greater bending angle but have less fatigue resistance.

[0031] US 3378067 and US 3487486 describe systems in which a flexible pipe section formed by a series of ball joints is provided between two rigid pipe sections.

[0032] US 9988860 refers to a suspended connector for attachment to a collar provided on a steel catenary riser. The riser may include a tapered tension joint or a flexible joint.

[0033] In this context, the invention can be defined as an upper connection arrangement for a subsea riser. The arrangement comprises a pivot combination disposed between, and fluidly connecting, upper and lower sections of rigid pipe. The pivot combination comprises: an upper spherical joint to which the upper section of the pipe is fixed, and around which the upper section of the Petition 870260033506, dated 10 / 04 / 2026, page 16 / 68 The 8 / 20 tube is pivotable; and a lower joint is fixed in series with the spherical joint, the lower joint being either a flexible joint or a tapered tension joint to which the lower section of the tube is attached.

[0034] The arrangement may further comprise a sleeve that is attached to the ball joint and that encloses the upper section of the tube. An annular gap between the sleeve and the upper section of the tube allows pivoting movement of the upper section of the tube around the ball joint. The sleeve may also limit further pivoting movement of the upper section of the tube around the ball joint. An outer face of the sleeve suitably comprises an upward tapered fitting formation.

[0035] The ball joint is preferably fixed directly to the bottom joint to form a compact and rigid unit. In some embodiments, a flange adapter can interconnect the respective flanges of the ball joint and the bottom joint.

[0036] For suspension purposes, the upper section of the tube may comprise a load-bearing formation spaced longitudinally from, and tapering towards the ball joint.

[0037] The ball joint may comprise a locking mechanism that is capable of locking the ball joint against movement of the upper tube section relative to the ball joint, and relative to other elements of the arrangement. For example, the locking mechanism may comprise a circumferential array of clamps or similar elements arranged around a central pivot element. In this case, the clamps may be radially movable inwards to engage the pivot element to lock the ball joint. To accommodate any inclination of the pivot element, the clamps are suitably radially movable inwards, for respectively different extensions.

[0038] The innovative concept also encompasses the arrangement of the invention when supported by a support structure of an installation of Petition 870260033506, dated 10 / 04 / 2026, p. 17 / 68 9 / 20 surface. For example, the supporting structure may comprise a suspended formation on which the bottom joint is seated, or the bottom joint may be engaged with the supporting structure via the ball joint.

[0039] When the ball joint is fitted with the aforementioned sleeve, the sleeve can be received in a bell mouth defined by a tubular support of the supporting structure, in particular an I-tube or a J-tube. Elegantly, in this case, the tension in the upper section of the tube can retain the sleeve in the bell mouth.

[0040] The arrangement of the invention can be used to support a catenary-type riser made of rigid or flexible pipe. In some embodiments, the tension in the upper section of the pipe can support the suspended weight of the riser.

[0041] Advantageously, the upper section of pipe can be in fluid communication with the surface installation piping without the need for an intermediate flexible conduit.

[0042] The innovative concept also encompasses a surface installation when supporting the arrangement of the invention.

[0043] The innovative concept extends to a corresponding method of connecting a subsea riser to a surface installation. The method comprises: pulling an upper connection arrangement of the riser for engagement with a support structure of the surface installation; while pulling, pivoting an upper section of rigid pipe of the arrangement around an upper ball joint of the arrangement, engaging a lower joint of the arrangement with the support structure, this lower joint being a flexible joint or a tapered tension joint fixed in series with the ball joint; suspending the riser from the surface installation by means of a lower section of rigid pipe of the arrangement that is attached to the lower joint engaged with the support structure; and effecting fluid communication between the upper section of rigid pipe and Petition 870260033506, dated 10 / 04 / 2026, page 18 / 68 10 / 20 piping on board the surface installation.

[0044] The ball joint can be locked to restrict further pivoting of the upper section of rigid tubing. The lower section of rigid tubing can also be pivoted around the lower joint while pulling the arrangement.

[0045] The bottom joint can be engaged with a suspended formation of the support structure. Alternatively, the bottom joint can be engaged with a bell mouth of a pipe, most conveniently after pulling the upper section of rigid pipe into that pipe. The bottom joint can then be held in engagement with the bell mouth by tension on the upper section of rigid pipe. More generally, the upper section of rigid pipe can be engaged with a suspended formation of the support structure, allowing the weight of the riser to be suspended through the upper section of rigid pipe.

[0046] The lower joint can be engaged with the bell mouth by means of the ball joint, for example, by means of a sleeve attached to the ball joint. The sleeve can be used to limit the pivoting movement of the upper rigid tube around the ball joint.

[0047] Prior art, such as US 2019 / 032428, comprises only one type of pivot. In contrast, the innovative concept involves a series connection between two pivots with different, yet complementary, characteristics. Specifically, one pivot, typically a ball joint, has high flexibility to accommodate large bending angles but low fatigue resistance and, therefore, can be used solely or primarily for riser installation. The other pivot, typically a flexible joint containing an elastomeric element, allows smaller bending angles but has good long-term fatigue resistance and, therefore, can be used solely or primarily for riser operation. Petition 870260033506, dated 10 / 04 / 2026, page 19 / 68 11 / 20

[0048] Thus, the invention provides an alternative solution for connecting a rigid riser to a counter of a surface installation, such as a floating production unit. The invention is designed for flexible pipes or for suspending a rigid pipe, replacing a rigid reel with a flexible reel above a lower counter.

[0049] Standard and field-proven solutions for rigid and flexible risers include free-suspended catenaries, slow-wave risers, weight-distributed risers, and other configurations. For some projects, these solutions are not feasible or lead to a substantial increase in field development costs. For other scenarios, where the riser counter of a surface installation is used only for flexible pipes and a rigid riser solution is required, known solutions for top connectors are not technically or financially feasible. The invention provides a novel concept for a riser top connector to accommodate these scenarios and address these challenges.

[0050] As noted above, a flexible riser is installed through the bell mouth of an I or J pipe extending from the lower balcony to the upper balcony. There is an angle difference at the lower balcony compared to the upper balcony. This is due to the catenary top angle at the lower balcony, generally being between 5° and 9° with the vertical, typically around 8°, while the riser is substantially vertical at the upper balcony, as shown in Figure 1. This angle difference is a challenge if a rigid spool above the riser is preferred. Consequently, the invention contemplates a rigid angled connection to address this challenge and also potentially to allow a rigid SCR to be installed on a flexible riser balcony.

[0051] The system of the invention provides a total rigid pipe solution for risers in case of any problem with flexible riser elements, whatever flexible riser solution may have been used. Petition 870260033506, dated 10 / 04 / 2026, page 20 / 68 12 / 20 employed. In addition to steel risers, the invention can be applied to TCP risers, standard flexible pipe risers, sheathed pipe risers, and so on. The system of the invention is also suitable for different riser configurations, for example, buoyancy-supported risers (BSRs), hybrid riser towers (HRTs), and indeed any decoupled riser solutions.

[0052] The invention system allows for a pre-abandonment scenario and can be used in combination with a pipe and riser (PLR) system, if required. Optionally, a locking tool can be provided to prevent large angles that arise during pipe retrieval.

[0053] Embodiments of the invention provide an upper riser connection section comprising at least, from top to bottom: a lower rigid pipe section; a flexible joint; a ball joint connected in series with the flexible joint; and an upper rigid pipe section. Each of these elements may have at least one flange at one end for end-to-end interconnection to at least one neighboring element. The invention may be used with a rigid riser, such as a steel catenary riser or a flexible riser.

[0054] The upper connection section of the riser may comprise a sleeve called a 'bishop's hat' which may slide around the upper rigid pipe section and connect mechanically to the ball joint and an external support. The sleeve limits the bending of the ball joint.

[0055] More generally, therefore, the ball joint may be connected mechanically to an external support. The flexible joint may also be connected mechanically to an external support. The external support may be a pipe or a seat or a support of a counter of a surface installation supporting the riser.

[0056] The face flanges of the ball joint and flexible joint can be reinforced by a mechanically connected flange adapter. Petition 870260033506, dated 10 / 04 / 2026, page 21 / 68 13 / 20 between them.

[0057] The angle of the ball joint can be locked after installation, for example, using a cylinder system that actuates a die of clamps, tabs or other locking mechanisms.

[0058] Conveniently, the upper section of rigid pipe can be connected directly to the surface installation piping without the need for a flexible reel.

[0059] Embodiments of the invention also implement a method for connecting a catenary-type riser to a surface installation for transporting a fluid between the seabed and the surface installation. This method comprises: providing a riser top comprising an upper rigid section, a ball joint, a flexible joint in series with the ball joint, and a lower rigid section; pulling the riser top through a connection means of the surface installation while the ball joint and the flexible joint pivot; locking the upper rigid section and the ball joint or the flexible joint in position in the connection means; fluidly connecting the upper rigid section to the process piping of the surface installation; and allowing the flexible joint to rotate during operations. The angle of the ball joint can, conversely, be locked for operations.

[0060] In summary, the invention provides an upper connection arrangement for a subsea riser, comprising a pivot or joint combination disposed between, and fluidly connecting, the upper and lower sections of rigid pipe. The pivot combination comprises an upper spherical joint to which the upper pipe section is attached, and around which the upper pipe section is pivotable. A lower joint, being a flexible joint or a tapered tension joint to which the lower pipe section is attached, is fixed to the spherical joint in series.

[0061] A sleeve may be attached to the ball joint, and may encircle the upper tube section to allow limited pivoting movement of the Petition 870260033506, dated 10 / 04 / 2026, p. 22 / 68 14 / 20 upper pipe section around the ball joint. The sleeve may sit on the bell mouth of an I or J pipe of a surface installation, or may be omitted if the lower joint is seated in a suspended formation. A locking mechanism may be able to lock the ball joint and thus prevent pivoting movement of the upper pipe section.

[0062] To contextualize the invention, reference has already been made to Figure Figure 1, which is a partial view of the end of a riser support structure mounted on the side of an FPSO. For a more easily understood understanding of the invention, reference will now be made, by way of example, to the remaining accompanying drawings, in which:

[0063] Figure 2 is a side view of an upper arrangement of the riser (riser tube) of the invention;

[0064] Figure 3 is an enlarged side view of a pivot or joint combination of the arrangement shown in Figure 2, comprising a ball joint in series with a flexible joint;

[0065] Figure 4 is an enlarged side view of the pivot combination shown in Figure 3, also showing an optional 'bishop's hat' sleeve around a rigid upper tube of the arrangement;

[0066] Figure 5 is a side view of the arrangement in Figure 2 as it is pulled into a tube I of a support structure during the installation of a riser;

[0067] Figure 6 corresponds to Figure 5, but shows the arrangement now pulled and engaged with a bell mouth of tube I;

[0068] Figure 7 is a longitudinal cross-sectional view through the pivot combination of the arrangement, with the upper tube in axial alignment with a lower rigid tube of the arrangement;

[0069] Figure 8 corresponds to Figure 7, but shows the upper tube of the arrangement pivoted away from the central longitudinal axis around the pivot axis of the ball joint; Petition 870260033506, dated 10 / 04 / 2026, p. 23 / 68 15 / 20

[0070] Figures 9 and 10 are enlarged perspective views of the ball joint in the states shown in Figures 7 and 8, respectively;

[0071] Figure 11 is an enlarged longitudinal cross-sectional view through a spherical joint of the arrangement, mounted on top of the flexible joint;

[0072] Figure 12 is a side view of an alternative support structure, showing the flexible joint seated in a suspended structure; and

[0073] Figure 13 is a perspective view corresponding to Figure 12.

[0074] Referring hereto, then, to Figures 2 to 4 of the drawings, an upper riser arrangement 22 of the invention comprises a longitudinal series of elements, namely, progressing upwards: a lower section of rigid pipe 24; a flexible joint 26; a ball joint 28 or ball connector that tops the flexible joint 26 in series; and an upper section of rigid pipe 30 being a rigid reel pipe, which may be up to about 30 m in length, welded to the ball joint 28. In this example, flanged connections are made between each of these elements and the neighboring element(s) in the series.

[0075] The upper end of the upper tube section 30 comprises a flange 32, typically according to an API specification. When this embodiment of the invention is positioned for use, a downward tapered axial load-bearing formation 34 below the flange 32 engages with an upper counter of a support structure to bear the entire tensile load of the catenary.

[0076] The lower end of the lower pipe section 24 is welded contiguously to the upper end of a steel catenary riser, effectively becoming integral with the riser it extends to, and includes the flexible joint 26. An optional riser monitoring system Petition 870260033506, dated 10 / 04 / 2026, page 24 / 68 16 / 20 is shown in Figures 2 and 4.

[0077] A hollow sleeve 38, known in the art as a 'bishop's hat', encircles the upper tube section 30 with substantial radial clearance, defining an annular space between them. As will be explained, the sleeve 38 is responsible for securing the upper riser arrangement 22 to the bell mouth 20, transferring bending moments to the upper tube section 30.

[0078] The annular clearance between the upper tube section 30 and the sleeve 38 allows limited pivoting movement of the upper tube section 30 around the ball joint 28. In this example, the upper tube section 30 can pivot around the ball joint 28 up to 15° from the central axis of the sleeve 38, thus being free to move relative to the other elements of the upper riser arrangement 22 within an upward diverging conical volume.

[0079] A skirt 40 at the bottom of the sleeve 38 is normally seated on top of the ball joint 28, as shown in Figure 2. However, the sleeve 38 is shown lifted away from the ball joint 28 in Figure 3 to show the weld 42, by which the upper tube section 30 is attached to the ball joint 28. The skirt 40 of the sleeve 38 is surrounded by upward-tapered flanges which, together, give a truncated cone profile to the base of the sleeve 38.

[0080] Returning now to Figures 5 and 6, these drawings show the upper arrangement of riser 22 being pulled inward and then engaged with the bell mouth 20 of an I-pipe or J-pipe.

[0081] In Figure 5, the API flange on the upper part of the upper pipe section 30 is shown entering the bell mouth 20 during the upward pull-up motion of the upper riser arrangement 22. At this stage, the lower pipe section 24 and the upper pipe section 30 are substantially in mutual alignment through the flexible joint 26 and the ball joint 28, all at an angle of about 4° with the vertical. Petition 870260033506, dated 10 / 04 / 2026, p. 25 / 68 17 / 20

[0082] In Figure 6, the upper riser arrangement 22 has been raised as sleeve 38 now engages with bell mouth 20. In this respect, the upward tapered profile around the skirt 40 of sleeve 38 serves as a coupling formation for sleeve 38, which complements the downward widened profile of bell mouth 20. In this way, sleeve 38 mechanically connects ball joint 28 and therefore the remainder of the upper riser arrangement 22 to an external support which is exemplified here by bell mouth 20.

[0083] As noted above, the engagement of the axial load area 34 of the upper tube section 30 with an upper balcony 16 of a support structure supports the tensile load of the catenary. When pulling up the upper riser arrangement 22, this tension also keeps the sleeve 38 engaged with the bell mouth 20. The sleeve 38 and bell mouth then support the flexible joint 26 to absorb angular loads arising from the deflection of the riser in operation. The ball joint 28 plays no role in handling these angular loads of the operating riser.

[0084] It will be observed in Figure 6 that the upper tube section 30 is now substantially vertical, while the remainder of the upper riser arrangement 22 corresponds to the typical slope of the riser top and bell mouth 20, namely between about 7° and 9° from the vertical in this example. The ball joint 28 pivots to accommodate this relative angular displacement of the upper tube section 30 within the limits of the surrounding sleeve 38.

[0085] Figures 7 and 8 and Figures 9 and 10 show the respective states of the spherical joint 28 when the riser top arrangement 22 is in the straight and angled states shown in Figures 5 and 6.

[0086] Figure 8 includes a detailed view showing that the outer face of the sleeve 38 comprises a tapered C-ring 44. The C-ring 44 is mounted on a rubber ring 46 to accommodate any gap between Petition 870260033506, dated 10 / 04 / 2026, p. 26 / 68 18 / 20 the 38 sleeve and the I-tube which incorporates the 20 bell mouth.

[0087] In the cross-sectional views of Figures 7 and 8, it will be evident that, as is conventional, the flexible joint 26 comprises an elastomeric element 48 which is sandwiched between the spherical pivot-forming parts 50. The flexible joint 26 contains a central tube 52 which effects fluid communication between the lower tube section 24 and the spherical joint 28. Furthermore, the flexible joint 26 is coupled to the spherical joint 28 by a flange adapter 54 which connects parallel flanges of the flexible joint 26 and the spherical joint 28, to hold those structures together in face-to-face sealing contact.

[0088] The characteristics of the spherical joint 28 are best appreciated with reference to Figures 9 to 11.

[0089] Figures 9 and 10 show that the ball joint 28 comprises a hollow pivot element 56 surrounded by a ring structure 58. The ring structure 58 has a matrix of holes 60 on its upper side to receive bolts for flanged connection to the sleeve skirt 40 38. The ring structure 58 sits atop a lower flange 62 through which the ball joint 28 is coupled to the flexible joint 26 using the flange adapter 54 mentioned above.

[0090] In this embodiment, the ball joint 28 has an optional locking mechanism. For this purpose, the ring structure 58 supports an angularly spaced array of radially movable clamps 64, shown here radially retracted in an unlocked configuration. By activating the respective clamp hydraulic cylinders 66 individually, the clamps 64 can be advanced radially inward in the various extensions that may be required to support the pivot element 56 in one of its various orientations.

[0091] Figure 11 shows that the pivot element 56 has a partially spherical base 68 in fluid communication with the central tube 52 Petition 870260033506, dated 10 / 04 / 2026, page 27 / 68 19 / 20 of the flexible joint. Figure 11 also shows that the base 68 of the pivot element 56 is received and retained in a complementary cavity within the ring structure 58. The cavity is defined by a guide insert 70 with a concave curvature in a partially spherical shape. A sealing line 72 communicates with the cavity to admit a sealing fluid that forms a seal around the pivot element 56.

[0092] It will be evident from Figure 11 that the clamps 64 are in a plane above the base 68 to rest against a narrower neck 74 of the pivot element 56. Working together, therefore, the clamps 64 can lock the pivot element 56 in any orientation relative to the ring structure 58. In this way, when the large pivot angle of the ball joint 28 has facilitated the installation of the riser and the installation is complete, the pivot element 56 of the ball joint 28 can be locked in an orientation corresponding to that of the upper pipe section 30.

[0093] Locking the pivot element 56 of the ball joint 28 in this manner couples the upper tube section 30 to the ball joint 28 and therefore to the flexible joint 26 as a rigid system, strengthening the structure and preventing further movement of the ball joint 28 which could cause fatigue. From this point on, the only compliance of the system is that provided by the flexible joint 26, which conventionally supports the riser for cyclic movement during its operational life, in a fatigue-resistant manner.

[0094] The upper pipe section 30 can be installed offshore after the riser and flexible joint 26 have been installed in the surface installation. If the upper pipe section 30 is installed after the riser, the pivot element 56 and guide insert 70 attached to the upper pipe section 30 can be inserted into the ring frame 58 and then locked by operating the clamp cylinders 66. However, an advantage of the rigid pivotable upper section of the invention is to avoid the need for additional connection since the rigid upper section can be Petition 870260033506, dated 10 / 04 / 2026, page 28 / 68 20 / 20 passed through the pipes.

[0095] Finally, Figures 12 and 13 show that the upper arrangement of the riser 22 of the invention can be applied not only to a balcony designed for a flexible riser, but also to a suspended structure 76 designed for a rigid riser. In this case, the flexible joint 26 is seated on the suspended structure 76 as best appreciated in Figure 13. This engagement with the suspended structure 76 is facilitated by the downward tapering of the flexible joint housing 26, which is evident from the previous drawings.

[0096] The upper flange 32 of the upper tube section seen in Figures 12 and 13 can be adapted for any type of connection to an upper counter. Sleeve 38 is not required in this configuration and has therefore been omitted.

[0097] Other variations are possible within the innovative concept. For example, a tapered tension joint could be used below the ball joint instead of a flexible joint. Petition 870260033506, dated 10 / 04 / 2026, p. 29 / 68

Claims

1 / 4 CLAIMS 1. Upper connection arrangement (22) for a subsea riser, the arrangement comprising a pivot combination disposed between, and fluidly connecting, upper and lower tube sections (30, 24) of rigid pipe, wherein the pivot combination comprises: an upper spherical joint (28) to which the upper tube section (30) is fixed, and around which the upper tube section (30) is pivotable; and wherein the arrangement (22) is characterized in that the pivot combination comprises a lower joint (26) fixed in series to the spherical joint (28), the lower joint (26) being a flexible joint or a tapered tension joint to which the lower tube section (24) is fixed.

2. Arrangement (22), according to claim 1, characterized in that it further comprises a sleeve (38) which is fixed to the spherical joint (28) and which surrounds the upper tube section (30), wherein an annular gap between the sleeve (38) and the upper tube section (30) allows pivoting movement of the upper tube section (30) around the spherical joint (28).

3. Arrangement (22), according to claim 2, characterized in that the sleeve (38) further limits the pivot movement of the upper tube section (30) around the ball joint (28).

4. Arrangement (22), according to any one of claims 2 or 3, characterized in that an outer face of the glove (38) comprises an upward tapered coupling formation (44).

5. Arrangement (22), according to any of the preceding claims, characterized in that the spherical joint (28) is fixed directly to the lower joint (26).

6. Arrangement (22), according to any of the preceding claims, characterized in that it further comprises a flange adapter (54) that interconnects respective flanges of the ball joint (28) and the bottom joint (26).

7. Arrangement (22), according to any of the preceding claims, characterized in that the upper tube section (30) comprises a load-bearing formation (34) spaced longitudinally from, and tapering towards the spherical joint (28).

8. Arrangement (22), according to any of the preceding claims, characterized in that the spherical joint (28) comprises a locking mechanism that is capable of locking the spherical joint (28) against the movement of the upper tube section (30) relative to the spherical joint (28).

9. Arrangement (22), according to claim 8, characterized in that the locking mechanism comprises a circumferential array of clamps (64) arranged around a central pivot element (56), the clamps (64) being radially movable inwards to engage the pivot element (56) to lock the ball joint (28), preferably wherein the clamps (64) are radially movable inwards in respectively different extensions.

10. Arrangement (22), according to any of the preceding claims, characterized in that it is supported by a support structure of a surface installation.

11. Arrangement (22), according to claim 10, characterized in that the supporting structure comprises a suspended formation on which the lower joint (26) is seated.

12. Arrangement (22), according to claim 10, characterized in that the lower joint (26) is engaged with the support structure through the spherical joint (28).

13. Arrangement (22), according to any of the Petition 870260033506, of 10 / 04 / 2026, page 31 / 68 3 / 4 claims 2 to 4, characterized in that it is supported by a support structure of a surface installation, this support structure comprising a tubular support that defines a bell mouth (20) in which the sleeve (38) is received, preferably in which the tension in the upper section of the tube (30) retains the sleeve (38) in the bell mouth (20).

14. Arrangement (22), according to any one of claims 10 to 13, characterized in that it supports a rigid or flexible tube catenary type riser, preferably in which the tension in the upper tube section (30) supports the suspended weight of the riser.

15. Arrangement (22), according to any one of claims 10 to 14, characterized in that the upper tube section (30) is in fluid communication with surface installation piping without an intermediate flexible conduit.

16. Surface mount, characterized in that it supports the arrangement (22) as defined in any one of claims 10 to 15.

17. Method of connecting a subsea riser to a surface installation, characterized in that it comprises: pulling an upper connection arrangement (22) from the riser for engagement with a support structure of the surface installation; when pulling, pivoting an upper rigid pipe section (30) of the arrangement (22) around an upper ball joint (28) of the arrangement (22); engaging a lower joint (26) of the arrangement (22) with the support structure, this lower joint (26) being a flexible joint or a tapered tension joint fixed in series with the ball joint (28); suspending the riser from the surface installation by means of a lower rigid pipe section (24) of the arrangement (22) which is fixed to the lower joint (26) engaged with the support structure; and effecting fluid communication between the upper rigid pipe section (30) and the piping on board the surface installation. Petition 870260033506, dated 10 / 04 / 2026, p. 32 / 68 4 / 4 18. Method according to claim 17, characterized in that it further comprises locking the ball joint (28) to restrict further pivoting of the upper section of the rigid tube (30).

19. Method, according to any one of claims 17 or 18, characterized in that it also comprises pivoting the lower rigid tube section (24) around the lower joint (26) by pulling the arrangement (22).

20. Method, according to any one of claims 17 to 19, characterized in that it comprises engaging the lower joint (26) with a suspended formation of the supporting structure.

21. Method, according to any one of claims 17 to 19, characterized in that it comprises pulling the upper rigid tube section (30) into a tube, and engaging the lower joint (26) with a bell mouth of the tube (20), wherein the method preferably comprises: - engaging the lower joint (26) with the bell mouth (20) by means of the spherical joint (28); - and / or engaging the lower joint (26) with the bell mouth (20) by means of a sleeve (38) fixed to the spherical joint (28); - and / or using the sleeve (38) to limit the pivoting movement of the upper rigid tube (30) around the spherical joint (28).

22. Method according to claim 21, characterized in that it comprises maintaining the lower joint (26) engaged with the bell mouth (20) by tension in the upper section of the rigid tube (30).

23. Method, according to any one of claims 17 to 22, characterized in that it comprises engaging the upper section of rigid pipe (30) with a suspended formation of the support structure, and preferably comprising suspending the weight of the riser through the upper section of rigid pipe (30). Petition 870260033506, dated 10 / 04 / 2026, p. 33 / 68

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