Mud return riser and method of deploying and retrieving same

Abstract

A mud return riser (20) includes multiple interconnected riser sections (20a, 20b) through which multiple pipes (40) extend. The connection between the upper flange (25) of a first riser section (20a) and the lower flange (24) of an adjacent second riser section (20b) is secured by a rotatable locking ring (30). Each riser section (20a, 20b) has a support skirt (23) rigidly fixed to the upper flange (25) and configured for engagement with a vertical friction support device (50). Also provided are mud return riser sections (20a, 20b) for the mud return riser (20), a mud return riser suspension system (60) including the vertical friction support device (50) and multiple mud return riser sections (20a, 20b), and a method for constructing the mud return riser (20).

Description

Technical Field

[0001] This disclosure relates to a mud return riser for offshore drilling and a method and system for deploying and retrieving the mud return riser at a marine vessel. Background Technology

[0002] Traditional offshore drilling is typically conducted via a marine drilling riser suspended from a drilling vessel (such as a Mobile Offshore Drilling Unit (MODU)), and this method has historically been the most trusted drilling concept for both exploration and production drilling in subsea oilfields. The marine drilling riser extends from the top of the subsea blowout preventer (BOP) to the bottom of the vessel's drilling rig. The marine drilling riser serves several functions: as a return conduit for drill cuttings and drilling fluid; as an auxiliary line for attaching and supporting the subsea BOP to the MODU for well control; and for bringing the subsea BOP to / from the subsea wellhead. The lower end of the riser is attached to the top of the Lower Marine Riser Assembly (LMRP) via a flexible element, which in turn is connected to the top of the Lower BOP. A riser tensioning system stabilizes the riser while passively compensating for the vessel's vertical movement. The riser can be disconnected from the Lower BOP via a large-angle release connector on the LMRP.

[0003] In some applications, open water (sometimes also called "standby-less") drilling has been proposed. This approach may be advantageous, for example, in ultra-deepwater or mature oilfields where the difference between pore pressure and fracture gradient in the reservoir is small (due to reservoir depletion and / or pressure rise). Open water drilling systems consist of a separate mud return standby independent of the drill string deployment and have a fluid lifting system, such as a subsea pump, to return the mud (i.e., drilling fluid, optionally containing drill cuttings) to the drillship.

[0004] Publications that may be useful for understanding this technical field include US 2019 / 0136642 A1; WO 2022 / 154666 A1; WO 2022 / 164324 A1; US ​​8,733,452 B2; and US 10,502,348 B2.

[0005] There is a need for continuous improvement of offshore drilling systems and methods, particularly to achieve more efficient operations or to make equipment designs more compact and / or easier to operate. The purpose of this disclosure is to provide these improvements, or at least to provide useful alternatives to existing technologies. Summary of the Invention

[0006] In one embodiment, a mud return riser is provided, comprising a plurality of interconnected riser sections through which a plurality of pipes extend. Each riser section has a lower flange and an upper flange for interconnecting the riser sections. The connection between the upper flange of a first riser section and the lower flange of an adjacent second riser section is secured by means of a rotatable locking ring. Each riser section has a support skirt rigidly fixed to the upper flange and configured for engagement with a vertical friction support device.

[0007] In one embodiment, a mud return riser section for use as a mud return riser is provided.

[0008] In one embodiment, a mud return riser suspension system is provided, which includes a vertical friction support device and multiple mud return riser sections.

[0009] In one implementation, a method for constructing a mud return riser is provided. Attached Figure Description

[0010] The above and other features will become apparent from the following illustrative and non-limiting description of an example with reference to the accompanying drawings, in which: Figure 1 The image shows a drilling vessel during drilling operations in open water (“no riser”).

[0011] Figure 2a and Figure 2b A perspective side view is provided of the upper flange of the first mud return riser section and the matching lower flange of the second mud return riser section according to the first example.

[0012] Figure 3 The diagram illustrates a relative arrangement, according to a first example, for connecting the upper flange of the first mud return riser section to the matching lower flange of the second mud return riser section.

[0013] Figure 4a and Figure 4b A perspective side view is provided of the upper flange of the first mud return riser section and the matching lower flange of the second mud return riser section according to the second example.

[0014] Figure 5 A schematic cross-sectional side view of a mud return riser suspension system, including a mud return riser section and a vertical friction support device, is shown.

[0015] Figure 6 A schematic three-dimensional top view of the vertical friction support device is depicted.

[0016] Figure 7A schematic cross-sectional side view of a vertical friction support device is shown.

[0017] Figure 8 A perspective side view of the adapter unit for the mud return riser is provided. Detailed Implementation

[0018] The following description provides an improved mud return riser concept for so-called riserless drilling rigs. The described mud return riser, mud return riser section, mud return riser suspension system, and method of constructing the mud return riser advantageously facilitate the operation and assembly of the mud return riser, thereby reducing operation time on mobile offshore drilling units and increasing operational safety and reliability during mud return riser deployment and retrieval.

[0019] Figure 1 The diagram shows a drilling vessel 100 conducting a riserless drilling operation at sea. The drill string 11 passes through open water 12 and leads to a subsurface wellbore 13 via a wellhead assembly 14. The wellhead assembly 14 includes a wellhead established on the seabed 15 and related equipment arranged on the wellhead, such as a blowout preventer (BOP), a rotary control device (RCD) 16 for sealing the drill string 11, etc.

[0020] The mud return riser 20 is suspended on the vessel 100 and fluidly connected to the wellhead assembly 14 below the RCD 16 to receive mud (i.e., drilling fluid pumped into the well from the top side of the vessel 100, optionally carrying drill cuttings). This "fluid connection" may take the form of a flexible riser section 21 including at least one flexible hose. A subsea pump 22 is provided to assist in pumping mud via the mud return riser 20 to the vessel 100. Alternatively, a different fluid lifting system may be used. The mud return riser 20 is preferably positioned a few meters laterally from the centerline of the well to ensure that it does not interfere with the drill string 11.

[0021] Those skilled in the art will recognize that the above content is itself a known arrangement for drilling in open water (“no riser”).

[0022] The mud return riser 20 comprises multiple riser sections 20a and 20b interconnected end-to-end. Before the drilling process begins, the mud return riser 20 is constructed by sequentially attaching riser sections 20a and 20b to the vessel 100 and lowering the resulting riser string into the water 12. Similarly, after the drilling process is completed, the mud return riser 20 can be dismantled by sequentially raising and disconnecting riser sections 20a and 20b. The length of each riser section 20a and 20b can be, for example, approximately 22 m. Each riser section 20a and 20b may include at least one pipe, preferably multiple pipes, extending axially through the riser section 20a and 20b. For example, the multiple pipes 40 may include a mud return line 41, a choke and kill line 42, a slops line 43 for returning water to the drilling vessel 100, and a pipe 44 for hydraulic supply to the BOP. In addition, the power and signal cables used for LMRP, RCD, BOP and subsea pump 22 can be guided via mud return riser 20.

[0023] In order to connect riser sections 20a and 20b to each other in an end-to-end relationship, each riser section 20a and 20b includes a lower flange 24 and an upper flange 25. The upper flange 25 of the first riser section 20a can be connected to the lower flange 24 of the second riser section 20b, and vice versa. Figure 2a , Figure 2b and Figure 3 The end portions of the first riser section 20a and the second riser section 20b are shown, wherein the first riser section 20a according to the first example is depicted. Figure 2a The upper flange 25 and the second riser section 20b () Figure 2b The lower flange 24 of the ) is, Figure 3 The relative arrangement for connecting the end flanges 24, 25 to each other is shown. According to an advantageous embodiment, the lower flange 24 can provide the male connector portion of the riser sections 20a, 20b, and the upper flange 25 can provide the female connector portion of the riser sections 20a, 20b.

[0024] like Figure 2b and Figure 3As shown, the connection between the upper flange 25 of the first riser section 20a and the lower flange 24 of the adjacent second riser section 20b can be secured by a rotatable locking ring 30. For example, the upper flange 25 and the lower flange 24 may include radially outwardly projecting connecting surfaces 26 for engaging with the mating locking surfaces 31 of the locking ring 30. The locking ring 30 may be rotatably attached to the lower flange 24, or it may be configured as a separate assembly and installed on the upper flange 25 of the first riser section 20a prior to the lower flange 24 of the second riser section 20b. To secure the connection between the upper flange 25 and the lower flange 24, the locking ring 30 can be rotated so that the locking surface 31 of the locking ring 30 engages with the connecting surfaces 26 of the end flanges 24, 25. For example, the connecting surfaces 26 and the locking surfaces 31 may include mating protrusions and recesses that can form multiple bayonet connections when the locking ring 30 is rotated, thereby achieving simultaneous locking. The protrusions may be, for example, lugs arranged at regular intervals around the periphery of the end flanges 24, 25. The locking ring 30 ensures a reliable and robust connection between the first riser section 20a and the second riser section 20b. Optionally, a locating pin 32 may be attached to the lower end flange 24 to prevent the locking ring 30 from rotating to the open position, and the locating pin may serve as an optical marker for visual inspection of the position and orientation of the locking ring.

[0025] from Figure 2a and Figure 3As can also be seen, each riser section 20a, 20b includes a support skirt 23 rigidly fixed to the upper flange 25 and configured to engage with the vertical friction support device 50 (described in further detail below). The support skirt 23 is configured to hold the riser sections 20a, 20b in slips during deployment and retraction of the mud return riser 20. By providing the support skirt 23 for vertical friction-based support, the operational performance of the riser sections 20a, 20b is significantly improved. In contrast, the conventional horizontal support structure commonly used in riser section assembly may require time-consuming and cumbersome switching between a support mode (where the riser sections to be connected are held) and a sliding mode (where the riser sections are allowed to move to enable subsequent riser section connections). With the vertical support concept, the time and force required to hold and move the mud return riser sections 20a, 20b can be greatly reduced. Since the mud return riser 20 is typically lighter and smaller than the subsea riser configured to surround the drill string 11, the frictional force provided by a suitable vertical friction support device 50 and applied to the support skirt 23 can provide sufficient holding force to securely hold riser sections 20a, 20b in place. Because vertical frictional force can be quickly, easily, and flexibly applied to the support skirt 23 by activating and deactivating the vertical friction support device 50, the operation time required for assembling and disassembling the mud return riser 20 can be significantly reduced. Furthermore, the concept of vertical friction support allows the locking ring 30 to rotate safely and easily relative to the upper flange 25 of the first riser section 20a, including the support skirt 23, while preventing rotation of the first riser section 20a by means of the vertical friction support device 50 that securely holds the support skirt 23.

[0026] For example, such as Figure 2a , Figure 3 and Figure 4bAs depicted, the support skirt 23 preferably includes an end face 23a that provides a circumferential locking ring support surface for the locking ring 30. Providing a locking ring support surface facilitates the operation of the locking ring 30 and securely supports it on the support skirt 23. The end face 23a can provide a collar-shaped support surface for circumferential support of the locking ring 30. The end face 23a can provide a substantially flat support surface on which the locking ring 30 can rotate with low resistance. Preferably, the locking ring 30 and the support skirt 23 can be arranged flush with each other to provide a smooth common outer surface and enhance protection for the pipe 40 and end flanges 24, 25. According to an advantageous example, the support skirt 23 extends for a length of at least 500 mm, thereby providing sufficient surface area to absorb the frictional forces exerted by the vertical friction support device 50. The support skirt 23 can include a generally cylindrical shape, such as having a circular or elliptical cross-section. With its generally cylindrical shape, the support skirt 23 can be held by the vertical friction support device 50, regardless of the current angle of rotation of the support skirt 23 about its longitudinal axis. According to an advantageous embodiment, the support skirt 23 may include a friction-enhancing surface, such as having grooves, recesses, friction-enhancing coatings, or form-fitting elements, thereby increasing the applicable frictional force and improving the reliability of the vertical friction support concept.

[0027] Figure 4a and Figure 4b A perspective side view is provided of the upper flange 25 of the first mud return riser section 20a and the matching lower flange 24 of the second mud return riser section 20b according to the second embodiment. As can be seen from the figures, the depicted riser sections 20a and 20b include different piping arrangements compared to the riser sections 20a and 20b of the first embodiment, for example, the waste liquid line 43 is not provided. Therefore, the present invention can be considered independent of the type and arrangement of the pipe 40 extending through the riser sections 20a and 20b. Furthermore, Figure 4b The support skirt 23 is depicted as including a closed portion 23c and a frame-like open portion 23d, thereby reducing the weight of the support skirt 23 and the associated riser sections 20a, 20b, while providing a sufficiently large friction area on the closed portion 23c to ensure that the support skirt 23 is securely held in place by means of the vertical friction support device 50. According to an advantageous example, the length of the closed portion 23c of the support skirt 23 is at least 500 mm, thereby providing sufficient surface area to absorb the frictional forces exerted by the vertical friction support device 50. This arrangement provides the advantage that the friction area on the closed portion 23c is longitudinally spaced from the upper flange 25, such that the flange 25 is positioned further away from the vertical friction support device 50 when it engages with the support skirt 23. This simplifies operation of the riser sections 20a, 20b, for example, making the locking ring 30 more easily accessible.

[0028] Figure 5 , Figure 6 and Figure 7 An example of a vertical friction support device 50 is schematically depicted, wherein, Figure 5 A vertical friction support device 50 supporting a first riser section 20a is shown, and a second riser section 20b is installed to the first riser section. Figure 6 A perspective view of the vertical friction support device 50 is provided, and Figure 7 A cross-sectional view of a vertical friction support device is shown. The vertical friction support device 50 can be a support structure having at least one vertical friction surface 52 configured to engage the supported object and apply a frictional force to it. The vertical friction support device 50 can be configured to be activated to generate the frictional force required to hold the supported object, and to be deactivated to allow the supported object to move along or through the vertical friction support device 50. The vertical friction support device 50 can be, for example, a powered slip device that can be activated and deactivated hydraulically, pneumatically, or electrically. According to an alternative example, the vertical friction support device 50 can be a manually operated slip device. According to an example, the vertical friction support device 50 includes at least two wedges 51, preferably at least three or at least four wedges 51, which can be arranged equidistantly around the riser sections 20a, 20b to be supported by the vertical friction support device 50. Each wedge 51 may provide a vertical friction surface 52 configured to selectively apply frictional force to the support skirts 23 of riser sections 20a, 20b. Furthermore, the vertical friction support device 50 may include suitable mating supports 54 for supporting the wedges 51 on the wedge surfaces 53 opposite to the vertical friction surfaces 52. The vertical friction support device 50 may include a circular structure with an axial opening 55 at its center, and the wedges 51 are circumferentially distributed around the axial opening 55. The distance between the vertical friction surfaces 52 of the wedges 51 is adjustable to allow the vertical friction support device 50 to accommodate support skirts 23 of riser sections 20a, 20b of different sizes. According to an alternative embodiment, the vertical friction surfaces 52 of the vertical friction support device 50 may be provided by friction elements other than the wedges 51 (e.g., cuboid blocks).

[0029] The support skirt 23 can be a cover structure attached to the upper flange 25 of the riser sections 20a, 20b, thereby providing the pipe 40 with a robust shell having a vertical mantle surface 23b to which the vertical friction support device 50 can apply frictional force. For this purpose, the vertical mantle surface 23b and the vertical friction surface 52 can generally be oriented parallel to each other to apply a uniform and large-area frictional force on the opposing surfaces of the support skirt 23 and the vertical friction surface 52. The vertical friction surface 52 can, for example, have a flat surface shape, or preferably a curved shape adapted to the preferably curved vertical mantle surface 23b of the support skirt 23 to increase the applicable frictional force. The support skirt 23 at least partially (preferably completely) radially surrounds the pipe 40 of the riser sections 20a, 20b and is capable of absorbing the applied frictional force, thereby preventing force transmission to the pipe 40. According to an advantageous example, the support skirt 23 can be assembled from at least two skirt portions, which can be configured to be assembled around the riser sections 20a, 20b and fixed to the upper flange 22 as a half-shell portion.

[0030] The term "vertical" can mean that the described structure is primarily vertically extended in its orientation of use, i.e., during the deployment and retrieval of the mud return riser 20. "Vertical extension" can generally refer to an extension direction perpendicular to the ground. According to a simplified scheme, a "vertical structure" can extend from the drillship 100 in a direction leading to the seabed 15.

[0031] Now turn to Figure 1 If a suitable transition structure is provided between riser sections 20a, 20b and the flexible riser section 21, the operational performance of the mud return riser 20 can be further enhanced. This flexible riser section has a flexible hose configured to fluidly connect riser sections 20a, 20b to the wellhead assembly 14. Therefore, the mud return riser 20 may preferably include, for example, […]. Figure 8The adapter unit 27 shown is used to connect multiple pipes 40 extending through interconnected riser sections 20a and 20b to the wellhead assembly 14 via a flexible hose (not shown in the figures) of a flexible riser section 21. The adapter unit 27 has: a first interface 27a, which can be connected to the pipes 40 and to the lower flange 24 of the riser sections 20a and 20b; a second interface 27b, which can be connected to the flexible hose of the flexible riser section 21; and a connecting line 27c connecting the first interface 27a and the second interface 27b. The flexible riser section 21 is configured as the pipe between the riser sections 20a and 20b and the wellhead assembly 14. Another technical function of the flexible riser section 21 is to compensate for the relative movement between the drilling vessel 100 and the wellhead assembly 14. For example, the flexible riser section 21 can compensate for heave during the vertical movement of the vessel.

[0032] The adapter unit 27 can be advantageously attached to one of the riser sections 20a and 20b by connecting the first interface 27a to the pipe 40 and the second interface 27b to the flexible hose of the flexible riser section 21 while the riser sections 20a and 20b are supported by the vertical friction support device 50, thereby facilitating the assembly and disassembly of the slurry return riser 20.

[0033] Preferably, at least one of the connecting pipes 27c can be a flexible connecting pipe 27c. Therefore, the flexible hoses in the flexible riser section 21 do not necessarily have to be arranged in the same distribution and sequence as the pipes 40, thus providing greater flexibility for interconnection. Furthermore, as... Figure 1 The subsea pump 22 shown can be connected to the adapter unit 27 via a first interface 27a or a second interface 27b, thus providing a clear connector for the subsea pump 22. According to an advantageous embodiment, the mud return pipe 41 in the plurality of pipes 40 can be configured as a load-bearing pipe to carry the subsea pump 22, thereby enabling reliable and efficient maintenance of the subsea pump 22.

[0034] Turn to Figure 5 The vertical friction support device 50 and multiple mud return riser sections 20a and 20b, each including a supporting skirt 23, can form a structure as follows: Figure 5The mud return riser suspension system 60 is shown. The mud return riser suspension system 60 advantageously facilitates the operation and assembly of the mud return riser 20, thereby reducing operation time on mobile offshore drilling units and increasing operational safety and reliability during mud return riser deployment and retrieval. The mud return riser suspension system 60 may also include locking rings 30 that can be attached to and detached from riser sections 20a, 20b during riser deployment and retrieval, the locking rings 30 being configured to secure the connection between adjacent riser sections 20a, 20b. The vertical friction support device 50 may include at least two wedges 51, each wedge having a vertical friction surface 52 configured to selectively apply frictional force to the support skirt 23 of the riser sections 20a, 20b. According to an advantageous embodiment, the vertical friction support device 50 is configured as a power slip that can be controlled hydraulically or electrically, thereby facilitating the operation of the vertical friction support device 50.

[0035] according to Figure 5 The mud return riser suspension system 60 shown can perform a method for constructing a mud return riser 20, the method comprising the following steps: - Provides a vertical friction support device 50, multiple mud return riser sections 20a, 20b of the described type, and multiple locking rings 30; -Guide the first riser section 20a to move along or through the vertical friction support device 50 until the support skirt 23 of the first riser section 20a reaches the vertical friction support device 50; -Activate the vertical friction support device 50 to apply frictional force on the support skirt 23; Connect the upper flange 25 of the first riser section 20a to the lower flange 24 of the second riser section 20b; - Rotate the locking ring 30 arranged around the upper flange 25 and the lower flange 24 to secure the above connection; and -Disable the vertical friction support device 50 to release the first riser section 20a.

[0036] This method can be repeated for multiple riser sections 20a, 20b until the assembly of the slurry return riser 20 is complete. For example, a subsequent step may include guiding the second riser section 20b along or through the vertical friction support device 50 until the support skirt 23 of the second riser section 20b reaches the vertical friction support device 50. Those skilled in the art will recognize that the proposed method for constructing the slurry return riser 20 can be reversed during the retrieval and disassembly of the slurry return riser 20, such that the related method for disassembling the slurry return riser 20 may include the following steps: -Guide the second riser section 20b and the first riser section 20a to move along or through the vertical friction support device 50 until the support skirt 23 of the first riser section 20a reaches the vertical friction support device 50. -Activate the vertical friction support device 50 to apply frictional force on the support skirt 23; - The locking ring 30 arranged around the upper flange 25 and the lower flange 24 is unlocked by rotating the locking ring 30; - Disconnect the upper flange 25 of the first riser section 20a from the lower flange 24 of the second riser section 20b; and -Disable the vertical friction support device 50 to release the first riser section 20a.

[0037] The described method for constructing and optionally disassembling the mud return riser 20 advantageously facilitates the operation and assembly of the mud return riser 20, thereby reducing operation time on mobile offshore drilling units and increasing operational safety and reliability when deploying and retrieving the mud return riser.

[0038] In any instance or embodiment described or claimed herein, the locking ring 30 and the support skirt 23 may be arranged to surround or enclose multiple conduits 40. Thus, all these conduits 40 may be located inside the locking ring 30 and the support skirt 23.

[0039] In any instance or embodiment described or claimed herein, the cross-sectional diameter of the support skirt 23 may be substantially the same as the cross-sectional diameter of the locking ring 30, for example, wherein the diameter of the support skirt 23 is between 0.8 and 1.2 times the diameter of the locking ring 30, or even more preferably, between 0.9 and 1.1 times the diameter of the locking ring 30.

[0040] This invention is not limited to the examples described above; reference should be made to the appended claims.

Claims

1. A mud return riser (20) comprising multiple interconnected riser sections (20a, 20b), with multiple pipes (40) extending through the multiple riser sections, Each of the riser sections (20a, 20b) has a lower flange (24) and an upper flange (25) for connecting the riser sections (20a, 20b) to each other, wherein, The connection between the upper flange (25) of the first riser section (20a) and the lower flange (24) of the adjacent second riser section (20b) is secured by a rotatable locking ring (30). Each of the riser sections (20a, 20b) has a support skirt (23) that is rigidly fixed to the upper flange (25) and configured to engage with the vertical friction support device (50).

2. The mud return riser (20) according to claim 1, wherein, The supporting skirt (23) includes an end face (23a) that provides a circumferential locking ring support surface for the locking ring (30).

3. The mud return riser (20) according to claim 1 or 2, wherein, The length of the supporting skirt (23) is at least 500 mm.

4. The mud return riser (20) according to any of the preceding claims, wherein, The supporting skirt (23) includes a closed portion (23c) and an open portion (23d), the open portion being, for example, a frame-like open portion (23d).

5. The mud return riser (20) according to any of the preceding claims, wherein, The supporting skirt (23) includes a friction-enhancing surface, for example, wherein the friction-enhancing surface is achieved by a coating, surface treatment, serration or other surface profile.

6. The mud return riser (20) according to any of the preceding claims, wherein, The mud return riser (20) includes an adapter unit (27) for connecting multiple pipes (40) extending through interconnected riser sections (20a, 20b) to a wellhead assembly (14) via a flexible hose of a flexible riser section (21). The adapter unit (27) has: a first interface (27a) for connecting to the pipes (40) and to the lower flange (24) of the riser section (20a, 20b); a second interface (27b) for connecting to the flexible hose of the flexible riser section (21); and a connecting line (27c) for connecting the first interface (27a) and the second interface (27b).

7. The mud return riser (20) according to claim 6, wherein, At least one of the connecting lines (27c) is a flexible connecting line (27c).

8. The mud return riser (20) according to claim 6 or 7, wherein, A subsea pump (22) is connected to the adapter unit (27).

9. The mud return riser (20) according to any of the preceding claims, wherein, The mud return pipe (41) in the multiple pipes (40) is configured as a load-bearing pipe to carry the subsea pump (22).

10. A mud return riser section (20a, 20b) for a mud return riser (20) according to at least one of claims 1 to 9, the mud return riser section (20a, 20b) comprising a lower flange (24) and an upper flange (25), the lower flange and the upper flange having radially outwardly projecting connecting surfaces (26) for engaging with a locking ring (30), the mud return riser section (20a, 20b) further comprising a support skirt (23) rigidly fixed to the upper flange (25) and configured for engaging with a vertical friction support device (50).

11. A mud return riser suspension system (60) comprising a vertical friction support device (50) and a plurality of mud return riser sections (20a, 20b) according to claim 10.

12. The mud return riser suspension system (60) according to claim 11, wherein, The vertical friction support device (50) includes at least two wedges (51), each of the at least two wedges having a vertical friction surface (52).

13. The mud return riser suspension system (60) according to claim 11 or 12, wherein, The vertical friction support device (50) is configured as a power slip that can be controlled hydraulically or electrically.

14. A method for constructing a mud return riser (20), the method comprising: - Provides a vertical friction support device (50), a plurality of locking rings (30) and a plurality of mud return riser sections (20a, 20b) as claimed in claim 10. - Guide the first riser section (20a) to move along or through the vertical friction support device (50) until the support skirt (23) of the first riser section (20a) reaches the vertical friction support device (50). -Activate the vertical friction support device (50) to apply frictional force on the support skirt (23); - Connect the upper flange (25) of the first riser section (20a) to the lower flange (24) of the second riser section (20b); - Rotate the locking ring (30) arranged around the upper flange (25) and the lower flange (24) to secure the connection between the upper flange and the lower flange; and - Deactivate the vertical friction support device (50) to release the first riser section (20a).

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