Standpipe assembly

Abstract

A riser assembly (110) including a riser (112) having a longitudinal axis (A) and including a first riser joint (114) with an end portion and a second riser joint (116) with an end portion adjacent the end portion of the first riser joint (114), the riser assembly (110) further including an auxiliary line (120, 120') having a first auxiliary line section (122, 122') and a second auxiliary line section (124, 124') connected via an auxiliary line joint (126, 126'), the auxiliary line joint including a first joint assembly (130, 130') connected to the first auxiliary line section (122, 122') and having a bearing surface (130a, 130a'), and a second joint assembly (132, 132') connected to the second auxiliary line section (124, 124') and having a bearing surface (132a, 132a'), the riser assembly (110) further including a first flange (134) extending radially outwardly from an outer surface of the first riser joint (114) adjacent the end portion of the first riser joint, and a second flange (136) extending radially outwardly from an outer surface of the second riser joint (116) adjacent the end portion of the second riser joint, the first and second flanges (134, 136) each having a bearing surface, the bearing surface of the first flange (134) engaging the bearing surface (130a, 130a') of the first joint assembly (130, 130'), and the bearing surface of the second flange (136) engaging the bearing surface (132a, 132a') of the second joint assembly (132, 132'), wherein one of the bearing surfaces of the first flange (134) and the first joint assembly (130, 130') is shaped to provide a point or area of contact between the two bearing surfaces while allowing relative angular movement between the two bearing surfaces.

Description

[0001] The present invention relates to a riser assembly, in particular a riser assembly having a riser connector which provides support for at least one auxiliary flow line which extends along the exterior of the riser and parallel to the riser.

[0002] Risers, for example risers which enclose a drill string in a subsea drilling operation, are constructed from a plurality of tubular sections, commonly referred to as riser joints, the adjacent ends of which are connected by a riser connector. As the riser is lowered towards a subsea wellhead, the sections are joined together on a vessel, such as a rig, using the riser connector. Each riser joint typically comprises a main cylindrical tube and at least one externally auxiliary, smaller diameter cylindrical tube, commonly referred to as an auxiliary line, which is attached to the main tube such that it is spaced apart from and extends parallel to the main tube. Typically, two auxiliary lines are connected to the riser in diametrically opposed fashion. In some cases, more than two auxiliary lines are provided.

[0003] The main tube forms an annular space around the drill string through which drilling fluid returns from the wellbore. The auxiliary lines are used to circulate fluid between the vessel and the subsea blowout preventer (BOP) on the wellhead, and can include choke lines, kill lines, boost lines or hydraulic lines.

[0004] The riser is suspended from the vessel, and it will be appreciated that the weight of the riser and string, the associated riser connectors can become very high as the wellhead can be located 3000m or more below sea level. It is therefore known that the resulting load will be shared with the auxiliary lines. This load sharing is achieved by fixing the end of each section of auxiliary line to the riser via the riser connector. For example, it is known for the riser connector to comprise an annular flange extending radially outwardly from the riser connector, one annular flange being provided at each end adjacent each riser joint. The auxiliary riser section extends between and is fixed to two flanges mounted on one riser joint, with a box and pin joint being located between the two flanges at the end of the adjacent riser joint to provide a fluid flow path between two adjacent auxiliary line sections. The adjacent riser joints are secured together by means of an internal locking ring which is fitted around the two adjacent riser joints between the two flanges.

[0005] Examples of such riser connectors are described in US 4,043,575 and US 2016 / 0258562.

[0006] Figure 1 A riser connection described in US 4,043,575 is illustrated. Figure 1A joint between the lower end of the first riser joint 10 and the upper end of the second riser joint 12 is shown, with two auxiliary lines 14, 16 mounted on either side of the riser joints 10, 12. The auxiliary lines 14, 16 are supported by flanges 18 and 20 and connected together via a connection between the flanges comprising a box 22 and a pin 24. The riser joints 10, 12 are secured together using a locking ring 25.

[0007] Figure 2 A riser connection described in US 2016 / 0258562 is illustrated. In this case, three auxiliary lines 26, 28, 30 are shown mounted on flanges 32, 34, with sections of the auxiliary lines attached to each of the two adjacent riser joints being connected by a box 36, 38, 40 and a pin 42, 44, 46 located between the two flanges 32, 34. Again, the riser joints 10, 12 are secured together using a locking ring 48.

[0008] Other riser connector configurations are described in US 4,487,434, GB 2 320 541, WO2011 / 104629 and US 4,280,719.

[0009] In Figure 1 and Figure 2 In the connector type illustrated, the transfer of a portion of the weight of the riser to the auxiliary lines can cause the flanges to deflect slightly, as Figure 3 illustrated in relation to the prior art riser connector embodiment described in US 2016 / 0258562. This can cause misalignment of the angle of the box and pin connections between adjacent auxiliary lines and therefore contact stresses and wear at the radially outer side of the assembly, at the radially inner edge of the box and the radially outer edge of the pin. While the extent of the possible deflection is greatly exaggerated in Figure 3 over time, repeated deflection can cause significant wear of the box and pin and this can compromise the integrity of the seal between adjacent sections of the auxiliary lines.

[0010] In the system described in WO 2011 / 104629, the adjacent ends of the riser joints are secured together by means of an outer locking ring that encircles and engages with the outer edges of the two flanges. This can help to reduce deflection of the flanges, but the use of such a larger diameter locking ring will have a significant impact on the weight of the riser connector.

[0011] In GB 2 320 541, an additional locking mechanism is provided to lock the adjacent ends of the auxiliary lines together independently of the locking of the riser joints, in order to prevent the adjacent sections of the auxiliary lines from separating in the vertical when the connector is subjected to bending stresses caused by the pressure of the fluid in the riser.

[0012] It is an object of the present invention to provide an alternative configuration of a riser connector that provides for load transfer to an auxiliary line, but in which the wear of the box-to-pin connection between adjacent auxiliary line sections is reduced without significantly increasing the weight of the riser connector.

[0013] According to the invention, there is provided a riser assembly comprising a riser having a longitudinal axis and comprising a first riser joint with an end portion and a second riser joint with an end portion adjacent to the end portion of the first riser joint, the riser assembly further comprising an auxiliary line having a first auxiliary line section and a second auxiliary line section connected via an auxiliary line joint, the auxiliary line joint comprising a first joint component connected to the first auxiliary line section and having a bearing surface, and a second joint component connected to the second auxiliary line section and having a bearing surface, the riser assembly further comprising a first flange extending radially outwardly from an outer surface of the first riser joint adjacent to the end portion of the first riser joint, and a second flange extending radially outwardly from an outer surface of the second riser joint adjacent to the end portion of the second riser joint, the first flange and the second flange each having a bearing surface, the bearing surface of the first flange being in engagement with the bearing surface of the first joint component, and the bearing surface of the second flange being in engagement with the bearing surface of the second joint component, wherein one of the bearing surface of the first flange and the bearing surface of the first joint component has a cardan formation shaped to provide a point, line or area of contact between said two bearing surfaces while allowing relative angular motion between said two bearing surfaces.

[0014] Advantageously, one of the bearing surface of the second flange and the bearing surface of the second joint component also has a cardan formation shaped to provide a point, line or area of contact between said two bearing surfaces while allowing relative angular motion between said two bearing surfaces.

[0015] The cardan formation or each cardan formation can have an arcuate shape in transverse cross-section.

[0016] The cardan formation or each cardan formation is advantageously shaped to allow relative angular motion between said two bearing surfaces about an axis substantially perpendicular to the longitudinal axis of the riser.

[0017] The bearing surface of one or both of the first flange and / or the second flange can be provided on an insert that is not integral with the remainder of the flange.

[0018] The support surface of one or both of the first joint assembly and / or the second joint assembly can be provided on a support piece that is not integral with the rest of the joint assembly.

[0019] The first flange and the second flange can be separated by an annular space around the end of the first riser joint and the end of the second riser joint, in which the first joint assembly is connected to the second joint assembly.

[0020] The first flange has a first side forming a first end of the annular space and an opposite second side, and the second flange has a first side forming a second end of the annular space and an opposite second side, in which case each of the support surfaces can form part of the first side of its respective flange.

[0021] The first joint assembly can extend through an opening provided in the first flange from its first side to its second side.

[0022] The second joint assembly can extend through an opening provided in the second flange from its first side to its second side.

[0023] The first auxiliary line section can be connected to the first joint assembly at the second side of the first flange.

[0024] The second auxiliary line section can be connected to the second joint assembly at the second side of the second flange.

[0025] The first joint assembly can comprise a pin and the second joint assembly can comprise a box in which the pin is positioned to provide the connection between the first auxiliary line section and the second auxiliary line section.

[0026] Embodiments of the application will now be described, by way of example only, with reference to the following drawings:

[0027] Figure 4 is a depiction of a longitudinal cross-section through a riser assembly according to the application in a plane comprising the longitudinal axis of the riser,

[0028] Figure 5 is a depiction of a longitudinal cross-section through Figure 4 is a longitudinal cross-section through one of the auxiliary lines and the associated flanges of the riser assembly depicted in Figure 4 in a plane perpendicular to the plane of the longitudinal cross-section depicted in

[0029] Figure 6 is Figure 4 is a perspective view of the riser assembly depicted in

[0030] Figure 7 is Figure 4a side view of the riser assembly illustrated in

[0031] Figure 8 illustrates a longitudinal cross-section through two of the support surfaces in the riser assembly illustrated in Figure 4 、 Figure 5 and Figure 6 illustrates a longitudinal cross-section through two of the support surfaces in the riser assembly illustrated in Figure 5 ,

[0032] Figure 9a is a perspective view of a portion of the first flange of the riser assembly illustrated in Figure 4 、 Figure 5 and Figure 6 illustrates a longitudinal cross-section through two of the support surfaces in the riser assembly illustrated in

[0033] Figure 9b is a perspective view of a portion of the second flange of the riser assembly illustrated in Figure 4 、 Figure 5 and Figure 6 illustrates a longitudinal cross-section through two of the support surfaces in the riser assembly illustrated in

[0034] With reference to Figure 4 、 Figure 5 and Figure 6 , a riser assembly 110 is shown comprising a riser 112 having a first riser joint 114 with one end and a second riser joint 116 with one end adjacent to the end of the first riser joint 114. In this embodiment, the riser joints 114, 116 each have a circular transverse cross-section and are joined together at their ends by means of a locking ring 115 positioned around the exterior of both ends to enclose a generally cylindrical main passage 118 having a longitudinal axis A, as is known to those skilled in the art. However, it will be appreciated that the present application is not limited to the use of a locking ring 115 and other methods of connecting the ends of the riser joints 114, 116 can be used, such as breech lock technology or actuated locking dogs.

[0035] The riser assembly 110 further comprises two auxiliary lines 120, 120', each having a first auxiliary line section 122, 122' and a second auxiliary line section 124, 124' connected via an auxiliary line joint 126, 126'. In this embodiment, the auxiliary line sections 122, 122', 124, 124' each have a circular transverse cross-section and are connected to enclose a substantially cylindrical passage 128, 128' with a longitudinal axis B, B'. The auxiliary lines 120, 120' are arranged around the outside of the riser 112 such that their longitudinal axes are substantially parallel to the longitudinal axis A of the riser 112. In this embodiment, the two auxiliary lines 120, 120' are located diametrically opposite each other with respect to the riser 112, such that the riser 112 is located exactly between the two auxiliary lines 120, 120'. Although two auxiliary lines 120, 120' are provided in this example, this need not necessarily be the case. The riser assembly 110 can comprise only one or more than two auxiliary lines.

[0036] Each auxiliary line joint 126, 126' can comprise a first joint assembly 130, 130' connected to the first auxiliary line section 122, 122', and a second joint assembly 132, 132' connected to the second auxiliary line section 124', 124'. Each joint assembly has a tubular body, which in this embodiment has an externally threaded end, and each auxiliary line section 122, 122', 124, 124' is fixed to its respective joint assembly 130, 130', 132, 132' by a threaded connection to the external thread.

[0037] In this embodiment, each first joint assembly 130, 130' comprises a pin and each second joint assembly 132, 132' comprises a box, each pin being positioned in the corresponding box to provide a connection between the first auxiliary line section 122, 122' and the second auxiliary line section 124, 124', as is known from the prior art described above. Both the pin and the box have a longitudinal axis which coincides when the pin is correctly aligned in the box.

[0038] The riser assembly 110 also includes a first flange 134 extending radially outward from an outer surface of the first riser joint 114 adjacent to an end of the first riser joint 114, and a second flange 136 extending radially outward from an outer surface of the second riser joint 116 adjacent to an end of the second riser joint 116. Thus, the first flange 134 and the second flange 136 are separated by an annular space surrounding the ends of the first riser joint 114 and the second riser joint 116. The first flange 134 has a first side 134a forming a first end of the annular space and an opposite second side 134b, and the second flange 136 has a first side 136a forming a second end of the annular space and an opposite second side 136b. In this example, the first and second sides 134a, 136a, 134b, 136b of the flanges 134, 136 extend generally perpendicular to the longitudinal axis A of the main passage 118.

[0039] The first joint assemblies 130, 130' each extend through an opening 138, 138' provided in the first flange 134 from its first side 134a to its second side 134b. Similarly, the second joint assemblies 132, 132' each extend through a corresponding opening 140, 140' provided in the second flange 136 from its first side 136a to its second side 136b. In this embodiment, the tubular body of each of the joint assemblies 130, 130', 132, 132' extends through the openings 138, 138', 140, 140'. Each first joint assembly 130, 130' is connected to its corresponding second joint assembly 132, 132' in the annular space, while the first auxiliary line section 122, 122' of each auxiliary line 120, 120' is connected to the first joint assembly 130, 130' at the second side 134b of the first flange 134, and the second auxiliary line section 124, 124' of each auxiliary line 120, 120' is connected to the second joint assembly 132, 132' at the second side 136b of the second flange 136.

[0040] Each joint assembly 130, 130', 132, 132' has a bearing surface 130a, 130a', 132a, 132a' that engages a corresponding bearing surface provided on one of the flanges 134, 136. In this embodiment, the bearing surface provided on the first side 134a of the first flange 134 engages the bearing surface 130a, 130a' of each first joint assembly 130, 130', while the bearing surface provided on the first side 136a of the second flange 136 engages the bearing surface 132a, 132a' of each second joint assembly 132, 132'.

[0041] To ensure Figure 3 As illustrated in the diagram, the deflection of flanges 134 and 136 that occurs when riser assembly 110 is suspended on the drilling vessel will not be transmitted to auxiliary pipeline joints 126 and 126'. Each of the support surfaces of the first flange 134 and the second flange 136 has a rocker formation 150, which is shaped to provide a point or area that contacts the support surfaces 130a, 130a', 132a, and 132a' of each of the joint assemblies 130, 130', 132, and 132', while simultaneously allowing relative angular movement between the two support surfaces. This is in Figure 8 The best maps are shown in Figures 9a and 9b, and... Figure 4 and Figure 5 Not visible in the illustrated cross-section. The rocker shaft forming portion 150 is arranged to allow relative angular movement between the two support surfaces about an axis substantially perpendicular to the longitudinal axis A of the main channel 118. Furthermore, in this preferred embodiment, the rocker shaft forming portion 150 is also arranged such that the axis about which the relative angular movement between the two support surfaces occurs is also perpendicular to a line extending between the longitudinal axis A of the main channel 118 of the riser 112 and the longitudinal axis B / B' of the associated auxiliary pipelines 120 / 120'.

[0042] therefore, Figure 3 The angular deflection of flanges 134 and 136 illustrated in the figure will not be transmitted to auxiliary line connectors 126 and 126' because during the deformation of flanges 134 and 136 caused by the forces transmitted along auxiliary lines 120 and 120', the supporting surfaces of flanges 134 and 136 can pivot about the rocker arm forming portion 150 relative to the supporting surfaces of auxiliary line connectors 126 and 126'. The pin can remain properly aligned in the box-shaped portion, and thus wear on the pin and box-shaped portion caused by repeated loading of the riser assembly 110 can be reduced.

[0043] It should be understood that although in this embodiment the rocker shaft forming portion 150 is disposed on the support surface of the flanges 134, 136, this is not necessarily the case. The rocker shaft forming portion may alternatively be disposed on the support surfaces 130a, 130a', 132a, 132a' of the connector assemblies 130, 130', 130'. It should also be understood that although in this embodiment the rocker shaft forming portion 150 is associated with each contact surface between the support surfaces of the flanges 134, 136 and the support surfaces of the connector assemblies 130, 130', 132, 132', this is not necessarily the case. For example, the rocker shaft forming portion 150 may exist only between the support surface of one of the flanges 134, 136 and the associated support surface of the first connector assembly 130, 130' or the second connector assembly 132, 132'.

[0044] The swing shaft forming portion 150 can have a curved surface. For example, the lateral cross section of the swing shaft forming portion 150 can have an arcuate shape. In this example, the swing shaft forming portion 150 corresponds in shape to the curved surface of a portion of a cylinder formed by cutting the cylinder longitudinally along two radii of the cylinder. However, this need not necessarily be the case, and the swing shaft forming portion 150 can be, for example, triangular or conical, or can be in the form of a triangular prism or cone with curved corners.

[0045] In this embodiment, the support surfaces 130a, 130a', 132a, 132a' of both the first joint assembly 130, 130' and the second joint assembly 132, 132' are each provided on a support 152, 152' that is not integral with the rest of the joint assembly 126, 126'. In particular, in this case, each of these support surfaces 130a, 130a', 132a, 132a' is provided on an annular insert 152, 152' positioned around the tubular body of the joint assembly 130, 130', 132, 132' and clamped between the respective flange 134, 136 and the shoulder 142, 142', 144, 144' integral with the tubular body of the joint assembly 130, 130', 132, 132'.

[0046] Also in this embodiment, the support surfaces of both the first flange 134 and the second flange 136 are provided on inserts 146a, 146b, 146a, 146b', 148a, 148b, 148a', 148b (not visible in Figure 4 In this example, each flange is provided with a set of such inserts 146a, 146b, 146a, 146b', 148a, 148b, 148a', 148b for each auxiliary line 120, 120'. In this embodiment, each set of inserts comprises two inserts positioned diametrically opposite each other around one of the first joint assembly 130, 130' or the second joint assembly 132, 132'. However, it will be appreciated that this need not necessarily be the case, and each flange 134, 136 can be equally provided with one insert for each auxiliary line 120, 120'.

[0047] The use of such inserts is not necessary, but can be advantageous in that they can be made of a material that is stronger than the rest of the joint assembly. It will be appreciated that by providing the rocker shaft formations 150, the contact area between the two abutting support surfaces is reduced compared to the case where both support surfaces are flat. Thus, when a force of a given size is applied to the riser assembly 110, the pressure at the contact area between the support surfaces will be much higher. It is therefore desirable that the support surfaces be made of a material that has a high compressive strength to avoid plastic yielding, deformation and flattening of the rocker shaft surfaces 150. However, it can not be necessary for the flanges 134, 136 or the rest of the joint assemblies 130, 130', 132, 132' to be made of such a high strength material, and using such a material for all of these components can increase the cost and / or weight of the riser assembly 110 more than is necessary. This can be avoided by providing the support surfaces on such inserts.

[0048] The inserts can be removable from the joint assemblies 130, 130', 132, 132' or flanges 134, 136 so that they can be replaced when they have worn to the point that they no longer provide the required angular relative movement.

Claims

1. A riser assembly comprising a riser having a longitudinal axis and having a first riser joint with an end portion and a second riser joint with an end portion adjacent the end portion of the first riser joint, the riser assembly further comprising an auxiliary line having a first auxiliary line section and a second auxiliary line section, the first and second auxiliary line sections being connected via an auxiliary line joint, the auxiliary line joint comprising a first joint assembly connected to the first auxiliary line section and having a bearing surface, and a second joint assembly connected to the second auxiliary line section and having a bearing surface, the riser assembly further comprising a first flange extending radially outwardly from an outer surface of the first riser joint adjacent the end portion of the first riser joint, and a second flange extending radially outwardly from an outer surface of the second riser joint adjacent the end portion of the second riser joint, the first and second flanges each having a bearing surface, the bearing surface of the first flange engaging the bearing surface of the first joint assembly, and the bearing surface of the second flange engaging the bearing surface of the second joint assembly, wherein, One of the bearing surfaces of the first flange and the bearing surface of the first joint assembly has a cardan joint formation shaped to provide a point or area of contact between the two bearing surfaces whilst allowing relative angular movement between the two bearing surfaces.

2. The riser assembly of claim 1, wherein, One of the bearing surfaces of the second flange and the bearing surface of the second joint assembly also has a cardan joint formation shaped to provide a point or area of contact between the two bearing surfaces whilst allowing relative angular movement between the two bearing surfaces.

3. The riser assembly of claim 1 or 2, wherein, The or each cardan joint formation has an arcuate shape in transverse cross-section.

4. The riser assembly of claim 1 or 2, wherein, The or each cardan joint formation is shaped to allow relative angular movement between the two bearing surfaces about an axis substantially perpendicular to the longitudinal axis of the riser.

5. The riser assembly of claim 1 or 2, wherein, The bearing surface of one or both of the first flange and / or the second flange is provided on an insert which is not integral with the remainder of the flange.

6. The riser assembly of claim 1 or 2, wherein, The bearing surface of one or both of the first joint assembly and / or the second joint assembly is provided on a bearing which is not integral with the remainder of the joint assembly.

7. The riser assembly of claim 1 or 2, wherein, The first flange and the second flange are separated by an annular space about the end of the first riser joint and the end of the second riser joint, the first joint assembly being connected to the second joint assembly in the annular space.

8. The riser assembly of claim 7, wherein, The first flange has a first side forming a first end of the annular space and an opposite second side, and the second flange has a first side forming a second end of the annular space and an opposite second side, in which case each of the bearing surfaces can form part of the first side of its respective flange.

9. The riser assembly of claim 8, wherein, The first joint assembly extends through an opening provided in the first flange from the first side to the second side of the first flange.

10. The riser assembly of claim 8, wherein, The second joint assembly extends through an opening provided in the second flange from the first side to the second side of the second flange.

11. The riser assembly of any of claims 8-10, wherein, The first auxiliary line section is connected to the first joint assembly at the second side of the first flange.

12. The riser assembly of any of claims 8-10, wherein, The second auxiliary line section is connected to the second joint assembly at the second side of the second flange.

13. The riser assembly of claim 1 or 2, wherein, The first joint assembly comprises a pin and the second joint assembly comprises a box, the pin being located in the box to provide a connection between the first auxiliary line section and the second auxiliary line section.

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