GB2486065A

GB2486065A - A riser connector

Info

Publication number: GB2486065A
Application number: GB1120617.4A
Authority: GB
Inventors: Simon Luffrum; Stephen Anthony Hatton
Original assignee: Subsea Riser Products Ltd
Current assignee: Subsea Riser Products Ltd
Priority date: 2010-12-01
Filing date: 2011-11-30
Publication date: 2012-06-06
Also published as: GB201020356D0; GB201120617D0

Abstract

A connecter for connecting first and second riser portions comprising first and second flanges where the flanges comprise an arcuate section having a reduced radial thickness such that the periphery of the flanges is shaped inwards towards the centre of the flanges to provide a passageway for a pipe 4. Further peripheral surfaces of the flanges may comprise chords.

Description

Apparatus for Running Subsea Completions and Xmas Trees

FIELD OF THE INVENTION

The present invention relates to a connector for use in connecting a first riser section to a second riser section and to a method of joining a first riser section to a second riser section. In particular, the present invention relates to a dual bore riser system used in the offshore oil and gas industry for installing completions in subsea wellheads and for running and conducting workover operations through subsea Xmas trees.

BACKGROUND TO THE INVENTION

Completion and workover risers are used in the offshore industry to install completions in subsea wells and provide a means to access the bores of subsea Xmas trees for completion and workover operations. Typically for conventional dual bore trees such risers are assembled from individual riser joints approximately 4Oft long. Each joint is configured with dual bores, typically a 5in bore used for production access and a smaller 2in bore used for access into the annulus of the tree or tubing hanger. Such a riser is typically referred to as a 5 x 2 completion riser; other configurations such as 7 x 2 also exist.

The completion and workover riser is typically installed from a floating drilling vessel by sequentially connecting riser joints at the drill floor. The riser spans the water depth physically and provides a pressure tight path for fluid communication and access to the well between equipment at the seabed with that at the surface.

The completion workover riser can be run in two modes of operation: The first mode is when it is used to run or remove the downhole completion and tubing hanger. In this mode the completion and workover riser must be run inside the marine drilling riser and thus the outside diameter of the completion riser is limited by the internal diameter of the marine drilling riser.

The second mode of operation is when it is used to install or work through a subsea tree. In this mode the completion workover riser is run in open water and thus directly subjected to all external environmental loads.

In either mode of operation completion and workover riser design must allow it to be installed quickly and efficiently and it must provide reliable pressure and structural integrity. This requires the riser to withstand high internal reservoir pressures, hydrostatic pressures, current and wave loading, vessel motions and high axial loads resulting from completion loads and external top tension applied to control the riser structural response.

The production and annulus tubulars of the completion workover riser are configured on a given centreline spacing so as to allow interface with the equipment at the seabed and the pressure control equipment at the drill floor. In addition to standard joints used along the riser length special strengthened tension and surface joints are needed at the upper and lower ends of the riser to control stresses and allow interface with the connecting equipment.

The applied load and geometric requirements drive the physical design of the completion workover riser. Typical completion riser designs have historically used threaded couplings to connect the production bores of adjacent joints. The annulus bore may also use a threaded coupling or a floating stab connection. However, the proximity of the two bores driven by the need to fit the completion workover riser inside the bore of a marine drilling riser provides significant spatial constraints making design, manufacture, handling and assembly of such joints challenging.

Typically with normal 5in by 2in completion and workover riser systems it is difficult to apply high preloads to the threaded connections due to the limited access to apply large makeup tooling. Hence such connections have limited preload and hence poor structural and fatigue capacities. Furthermore the limited preload prevents the use of reliable metal sealing technology and typically such connections use elastomeric seals.

It is an aim of the present invention to overcome at least one problem associated with the prior art whether refereed to herein or otherwise.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a connector for connecting a first riser section to a second riser section contained within an outer conduit, the connector comprising a first annular flange located on the first riser section and a second annular flange located on the second riser section, the annular flanges having corresponding securement means to secure the annular flanges together, wherein the annular flanges comprise an arcuate section having a reduced radial thickness such that an outer periphery of the annular flanges is shaped relatively inwards towards a centre of the flanges to provide a passageway space for at least a part of a pipe to locate adjacent to the riser and within the outer conduit.

The term radial thickness refers to the distance between an inner diameter and an outer diameter of the flanges.

The diameter of the pipe plus the diameter of the outer diameter of the flanges may be greater than an inner diameter of the outer conduit.

The diameter of the pipe plus the diameter of the arcuate section reduced thickness of the flanges is less than an inner diameter of the outer conduit.

Preferably the flanges comprise outer peripheries in which the outer peripheries comprise incomplete circles. Preferably the incomplete sections of the incomplete circular peripheries provide the passageway space.

Preferably the riser sections connect to form a riser.

Preferably the pipe is secured to the riser such that the riser and the pipe extend parallel and off set from each other. Preferably the riser and the pipe form a dual conduit assembly.

Preferably the passageway space comprises a segmental space.

Preferably the passageway space is defined at least in part by a chord from the outer periphery of the flanges.

The passageway space may comprise a recessed or concave portion to enable a part of the pipe to be received within the passageway space.

The outer peripheries of the flanges may provide a second space wherein the second space provides a proximity space to enable the riser to locate within a close proximity to an outer conduit.

Preferably the radial thickness of the annular flanges is less for a second arcuate section such that the outer periphery of the annular flanges is shaped relatively inwards towards the centre of the flanges to provide the proximity space.

The proximity space may enable the riser to locate closer to an outer conduit compared to a connector having complete annular flanges defined around the complete periphery of the riser sections.

The proximity space may enable the riser to locate closer to an outer conduit in a direction extending along a line form the centre of the riser through a point midway along the passageway space than in a direction extending along a line from the centre of the riser through a point midway along mounting sections provided on the flanges.

Preferably the outer peripheries of the flanges each comprise at least one arc of a circle and a chord of the circle.

Preferably a shape of the outer periphery of the first flange and a shape of the outer periphery of the second flange are identical.

Preferably the connector is arranged, in use, to connect the riser sections located within an outer conduit.

Preferably the connector is arranged, is use, to connect the riser sections to provide a riser which is off set from the outer conduit.

Preferably the first riser section and the second riser section are connected to form a cylindrical riser having a circular fluid flow path located centrally.

Preferably the outer peripheries of the flanges comprise two arcs of a circle and two chords of the circle. Preferably the two chords are located symmetrically about the flanges. Preferably the two arcs are located symmetrically about the flanges.

Preferably each flange comprises incomplete annular mounting means on which securement means are located. Accordingly, the mounting means on each flange comprises an incomplete annulus. Preferably each mounting means comprises an arcuate section.

Preferably each flange provides two mounting means on which securement means are located. Preferably each mounting means comprises an arcuate section.

Preferably the two arcuate sections are identical and may be located symmetrically about the riser sections.

Preferably a first space between the two arcuate sections provides the passageway space.

Preferably a second space between the two arcuate sections provides a proximity space to enable the riser to locate within a close proximity to an outer conduit which may contain the connector.

Preferably each flange provides mounting means comprising at least a first arcuate mounting section on which the securement means are located.

Preferably the mounting means comprises a plurality of holes through which securement means may extend to secure the first flange to the second flange.

Preferably one part of the hole may be provided in the first flange and a second part of the hole may be provided in the second flange. The two parts of the hole preferably register to enable a securement element to locate therethrough. The mounting means may comprise at least four, six or eight holes. Preferably half of the holes are provided on a first section of the mounting means and the other half of the holes are provided on a second section of the mounting means.

Preferably the securement means comprise corresponding bolts and nuts.

Preferably the flanges provide holes through which a bolt extends.

Preferably the flanges provide a sealing surface.

Preferably the sealing surface provides a metal to metal seal.

Preferably the connector comprises a gasket which is arranged to locate between the sealing surfaces of the flanges.

The connector may provide an auxiliary passageway space to enable an auxiliary conduit to locate adjacent to the riser. The connector may provide two auxiliary passageway spaces to enable two auxiliary conduits to locate adjacent to the riser.

The or each auxiliary conduits may comprise control umbilical cable(s).

According to a second aspect of the present invention there is provided an assembly comprising an outer conduit and a riser formed from at least two sections connected together by a connector, the connector comprising a first annular flange located on a first riser section and a second annular flange located on a second riser section, the annular flanges having corresponding securement means to secure the annular flanges together, wherein the annular flanges comprise an arcuate section having a reduced radial thickness such that an outer periphery of the annular flanges is shaped relatively inwards towards a centre of the flanges to provide a passageway space for at least a part of a pipe to locate adjacent to the riser and within the outer conduit.

According to a third aspect of the present invention there is provided a method of locating a riser and a pipe with an outer conduit comprising forming the riser by connecting at least a first riser section and a second riser section using a connector, wherein the connector comprises a first annular flange located on the first riser section and a second annular flange located on the second riser section, the annular flanges having corresponding securement means to secure the annular flanges together, wherein a radial thickness of the annular flanges is less for an arcuate section such that an outer periphery of the annular flanges is shaped relatively inwards towards the centre of a flanges to provide a passageway space for at least a part of a pipe to locate adjacent to the riser and within the outer conduit.

Accordingly the present invention provides a method for reliably connecting dual bore completion workover riser joints in a manner that allows substantial preload, high structural strength and conventional metal to metal sealing and still fit within a marine drilling riser.

The design uses a flanged connection wherein the bolt distribution around the flange is non uniform and the flange outside diameter is non circular. The coupling design is sized for 1O,000psi internal operating pressure and normally a flange sized for this operating pressure would be too big to fit within the spatial constraints of the bore of the marine drilling riser. However, the present invention overcomes this problem by the proposed bolt and flange geometry. Furthermore the flange geometry is optimised to allow the flange to accommodate and protect the control umbilical which need to be run adjacent to the riser tubulars and pass by the flange connection without the risk of being crushed between the workover riser and marine drilling riser wall.

The flange uses a smaller number of bolts than typically used in a standard API or ANSI flange of the same capacity in order to simplify the manufacture and facilitate assembly. The smaller number of bolts also allows the bolt distribution around the flange diameter to be optimised. In the current design 8 bolts are selected and these are located in two groups of 4 either side of the flange. This provides the space needed to accommodate annulus line, the umbilicals and allow the flange OD to be reduced diametrically opposite the annulus line to allow the envelope of the connection to be maintained within the spatial constraints of the marine drilling riser bore and the production and annulus bores on the correct relative centres.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 shows the general arrangement of the asymmetric flange coupling; Figure 2 is a cross section through the asymmetric flanged coupling; Figure 3 is a plan view looking down on the riser asymmetric flange located on the bore of the marine drilling riser.

Figure 4 is a plan view of the underside of the riser asymmetric flange located on the bore of the marine drilling riser.

DETAILED DESCRIPTION

The present invention provides a connector comprising an upper flange I (a first flange) located on a first riser section and a lower flange 2 (a second flange) on a second riser section which are machined from forged materials and used to connect the production line pipe 3 (a riser) and the annulus line pipe 4 (a pipe).

The annulus line pipe 4 is arranged to extend parallel with, but off set from, the production line pipe 3. The flange faces are machined with mating gasket profiles on the respective bores. The gasket 5 is a metal to metal bore gasket seal that is initially preloaded during flange make-up and then pressure energised by application of internal fluid. The gasket is typically manufactured from 316 stainless steel and is located in a machined pocket that is inlayed with a corrosion resistant material, typically Inconel 625.

A test port and peripheral 0 ring may also be provided to allow a back seal test to be performed on the gasket after makeup to make sure of its correct sealing.

The flange forgings are externally machined to the profile shown to ensure smooth structural transitions from the pipe into the flange bodies. The thickness of the flange body is purposefully larger than a typical flange to provide higher stiffness and thus better to accommodate the asymmetric bolting pattern without loss of flange preload and cyclic bolt loading.

The flange forgings are machined on their bore with a 5.125in internal diameter for the production bore and an asymmetric OD to provide a clearance with the internal diameter of the marine drilling riser 6 (an outer conduit), typically 17-lI2in. Each flange half is machined with 8 mating vertical bolt holes (securement holes) on mounting portions to accept the bolts (securement members). The flanges may be provided with 4, 6, 8, 10 or another suitable number of holes and securement members. In the lower flange the holes are further machined to accommodate a captured nut 7. This arrangement simplifies installation and makeup whilst maintaining a flush lower flange face on which to easily support or spider the riser string during handling.

The mounting portions for the bolts generally comprise two arcuate sections which are symmetrically provided on the flanges 1, 2 around the riser 3. In particular two arcuate mounting portions are provided with two portions located at each side which provide a proximity space and a passageway space. These flat portions may include recesses or concave portions to accept a pad of the perimeter of an annulus line pipe 4 and/or umbilical cables.

Each flange 1, 2 generally comprises an annulus having an inner diameter and an outer diameter with each flange 1, 2 having a radial thickness extending between these two diameters. Each annular flange 1, 2 comprise an arcuate section having a reduced radial thickness such that an outer periphery (or outer diameter) of each annular flange 1, 2 is shaped relatively inwards towards a centre of the flange 1, 2 to provide a passageway space for at least a part of a pipe 4 to locate adjacent to the riser and within the outer conduit 6. This passageway space enables a conduit to bypass the connector within the outer conduit. Previously, a flanged connector would accommodate a greater proportion of the inner space within the outer conduit and such a by pass would not be possible.

The outer periphery of each annular flange is non-circular and forms an incomplete circle comprising part of a circumference of a circle and a chord of the circle or two parts of a circumference of a circle spaced between tow chords of the circle.

The bolts 8 are specifically designed for optimum fatigue performance as is typical on marine drilling riser couplings. The bolts are single piece forgings and -11 -manufactured from a high strength alloy steel typically 130-l45ksi yield. The bolts are installed using an air spinner for speed and final torque applied using a hydraulic torque wrench to accurately achieve an optimum preload.

The annulus tubular connection 9 is bolted on the side of the flange. It consists of a lower female stab receptacie 10 and an upper male stab 11. The interface between the two is sealed using conventional elastomeric seals located on the body of the male stab 12. The male stab is threaded onto the end of the annulus tubing to allow replacement of the stab in the event that the stab is accidentally damaged.

The annulus line pipe 4 is retained within a concave or recessed portion defined in the outer peripheries of the flanges 1, 2.

The outer peripheries of the flanges 1, 2 provide a second space providing a proximity space to enable the riser 3 to locate within a close proximity to the outer conduit 6. Again, the radial thickness of the annular flanges 1, 2 is less for a second arcuate section such that the outer periphery of the annular flanges 1, 2 is shaped relatively inwards towards the centre of the flanges 1, 2 to provide the proximity space. The proximity space enables the riser 3 to locate closer to the outer conduit 6 compared to a connector having complete annular flanges defined around the complete periphery of the riser sections.

In particular, the proximity space enables the riser 3 to locate closer to the outer conduit 6 in a direction extending along a line form the centre of the riser 3 through a point midway along the passageway space than in a direction extending along a line from the centre of the riser 3 through a point midway along mounting sections provided on the flanges 1, 2.

The flange allows routing of control umbilicals, 13, around it, fitting inside the marine drilling riser. These control umbilicals 13 locate and are retained within recessed or concave portions provided in the outer peripheries of the flanges 1, 2.

Again, this reduces the overall cross-sectional diameter of the assembly.

Claims

CLAIMS1. A connector for connecting a first riser section to a second riser section to form a riser contained within an outer conduit, the connector comprising a first annular flange located on the first riser section and a second annular flange located on the second riser section, the annular flanges having corresponding securement means to secure the annular flanges together, wherein the annular flanges comprise an arcuate section having a reduced radial thickness such that an outer periphery of the annular flanges is shaped inwards relatively towards a centre of the flanges to provide a passageway space for at least a part of a pipe to locate adjacent to the riser and within the outer conduit.
2. A connector according to Claim I in which the diameter of the pipe plus the diameter of the outer diameter of the flanges is greater than an inner diameter of the outer conduit.
3. A connector according to Claim I or Claim 2 in which the diameter of the pipe plus the diameter of the arcuate section of reduced thickness of the flanges is less than an inner diameter of the outer conduit.
4. A connector according to any preceding claim in which the flanges comprise outer peripheries in which the outer peripheries comprise incomplete circles.
5. A connector according to any preceding claim in which the pipe is secured to the riser such that the riser and the pipe extend parallel and off set from each other.
6. A connector according to any preceding claim in which the riser and the pipe form a dual conduit assembly.
7. A connector according to any preceding claim in which the passageway -14 -space comprises a segmental space.
8. A connector according to any preceding claim in which the passageway space is defined at least in part by a chord from the outer periphery of the flanges.
9. A connector according to any preceding claim in which the passageway space comprise a recessed or concave portion to enable a part of the pipe to be received within the passageway space.
10. A connector according to any preceding claim in which the outer peripheries of the flanges provide a second space wherein the second space provides a proximity space to enable the riser to locate within a close proximity to an outer conduit.
11. A connector according to Claim 10 in which the radial thickness of the annular flanges is less for a second arcuate section such that the outer periphery of the annular flanges is shaped relatively inwards towards the centre of the flanges to provide the proximity space.
12. A connector according to Claim 10 or Claim 11 in which the proximity space enables the riser to locate closer to the outer conduit compared to a connector having complete annular flanges defined around the complete periphery of the riser sections.
13. A connector according to any preceding claim in which the outer peripheries of the flanges each comprise at least one arc of a circle and a chord of the circle.
14. A connector according to any preceding claim in which the connector is arranged, is use, to connect the riser sections to provide a riser which is off set from the outer conduit.
15. A connector according to any preceding claim in which the outer peripheries of the flanges comprise two arcs of a circle and two chords of the circle
16. A connector according to Claim 15 in which the two chords are located symmetrically about the flanges and the two arcs are located symmetrically about the flanges.
17. A connector according to any preceding claim in which each flange comprises incomplete annular mounting means on which securement means are located such that the mounting means on each flange comprises an incomplete annulus.
18. A connector according to Claim 17 in which each mounting means comprises an arcuate section.
19. A connector according to any preceding claim in which each flange provides two mounting means on which securement means are located, each mounting means comprising an arcuate section and the two arcuate sections being identical and located symmetrically about the riser sections.
20. A connector according to Claim 19 in which a first space between the two arcuate sections provides the passageway space and a second space between the two arcuate sections provides a proximity space to enable the riser to locate within a close proximity to an outer conduit which contains the connector.
21. A connector according to any preceding claim in which each flange provides mounting means comprising at least a first arcuate mounting section on which the securement means are located.
22. A connector according to Claim 21 in which the mounting means comprises a plurality of holes through which securement means extend to secure the first flange to the second flange.
23. A connector according to Claim 22 in which one part of the hole is provided in the first flange and a second part of the hole may be provided in the second flange and the two parts of the hole register to enable a securement element to locate therethrough.
24. A connector according to Claim 22 or Claim 23 in which the mounting means comprises at least eight holes.
25. A connector according to any one of Claim 22 to Claim 24 in which half of the holes are provided on a first section of the mounting means and the other half of the holes are provided on a second section of the mounting means.
26. A connector according to any preceding claim in which the securement means comprise corresponding bolts and nuts.
27. A connector according to any preceding claim in which the flanges provide a sealing surface.
28. A connector according to Claim 27 in which the sealing surface provides a metal to metal seal.
29. A connector according to any preceding claim in which the connector comprises a gasket which is arranged to locate between sealing surfaces of the flanges.
30. A connector according to any preceding claim in which the connector provides an auxiliary passageway space to enable an auxiliary conduit to locate adjacent to the riser.
31. A connector according to any preceding claim in which the connector provides two auxiliary passageway spaces to enable two auxiliary conduits to locate adjacent to the riser.
32. A connector according to Claim 30 or claim 31 in which the or each auxiliary conduits comprises a control umbilical cable.
33. An assembly comprising an outer conduit, a pipe and a riser formed from at least two sections connected together by a connector, the connector comprising a first annular flange located on a first riser section and a second annular flange located on a second riser section, the annular flanges having corresponding securement means to secure the annular flanges together, wherein the annular flanges comprise an arcuate section having a reduced radial such that an outer periphery of the annular flanges is shaped relatively inwards towards a centre of the flanges to provide a passageway space for at least a part of the pipe to locate adjacent to the riser and within the outer conduit.
34. A method of locating a riser and a pipe within an outer conduit comprising forming the riser by connecting at least a first riser section and a second riser section using a connector, wherein the connector comprises a first annular flange located on the first riser section and a second annular flange located on the second riser section, the annular flanges having corresponding securement means to secure the annular flanges together, the method comprising providing a passageway space where the annular flanges comprise an arcuate section having a reduced radial thickness such that an outer periphery of the annular flanges is shaped inwardly relatively towards a centre of the flanges, the method further comprising locating the pipe adjacent to the riser in the passageway space and within the outer conduit
35. A connector for connecting a first riser section to a second riser section contained to form a riser contained within an outer conduit substantially as herein described, with reference to, and as shown in, any of the accompanying figures.
36. An assembly comprising an outer conduit and a riser formed from at least two sections connected together by a connector substantially as herein described, with reference to, and as shown in, any of the accompanying figures.
37. A method of locating a riser and a pipe within an outer conduit substantially as herein described, with reference to, and as shown in, any of the accompanying figures.