FIELD OF THE INVENTION

The invention relates to a composite pipe termination for use in the oil and gas industry, such as in subterranean and sub-sea locations, and a method of providing a composite pipe termination.

DESCRIPTION OF THE RELATED ART

Subsea oil and gas drilling and development employs pipes to transport liquid and/or gaseous hydrocarbons from the seabed to the sea surface and to transport injection fluids from the surface to the seabed. These pipes have typically been made from steel or from unbonded layers of materials, such as one or more layer(s) of steel wires combined with a plastic liner, which together form a flexible, unbonded steel pipe. Such unbonded, flexible pipes are covered by American Petroleum Institute standard API 17J.

Over time, the subsea depths at which hydrocarbons are extracted has tended to increase. This development has been accompanied by a need to operate under harsher conditions including one or more of conditions of increased salinity, higher acidity, higher internal and external pressures and higher temperatures. In order to address these challenges, the industry has turned to composite pipes, comprising fibre-reinforced thermoplastic polymer. Reference may be made to WO 2012/072993 A1 which discloses such composite pipes. These pipes may be manufactured by winding tapes of composite material onto a pipe liner and fusing them thereto, then winding further layers of tape on top and fusing each layer to the immediately preceding layer. The composite material typically comprises a thermoplastic matrix, such as polyether ether ketone, with fibres embedded therein and the liner is typically made of the same thermoplastic material as the matrix. These pipes are lighter and better able to withstand the more severe environments as well as the more complex dynamic loading conditions including tension, bending and intemal/extemal pressure found deep below the sea surface. DNV standard DNVGL-ST-F119 (August 2018) relates to thermoplastic composite pipes for offshore applications in the oil and gas industry.

An obstacle to the introduction of such composite pipes has been the ability to effectively terminate such pipes and to reliably connect them to non-composite, especially steel, piping and apparatus at both subsea and surface interfaces. Composite pipe terminations and connections must be able to provide a reliable transition from the composite pipe material to a standard steel pipe, which may typically incorporate a steel flange or hub connection. The different structural properties of the two materials on the one hand and the differences in thermal expansion on the other, may make it challenging to effect both a reliable structural and sealing connection. Reference may also be made to WO 2012/095633 A1 and WO 2017/163021 A1 , which disclose prior art end-fittings for a composite pipe.

There is a need to improve composite pipe terminations, such that they may reliably be connected to metal piping. In particular, there is a need to improve the seal achieved by the composite pipe termination and to improve its ability to resist axial and torsional forces. In addition, it is desirable for the diameter of the pipe termination to be kept small so that it is not significantly larger than the diameter of the pipe.

For completeness, pipe end-fittings are also known from GB 2439 146 A, EP 2492 571 A2 and US 2014/0312612 A1. These documents relate to flexible steel, unbonded pipe of the type discussed above. Although such flexible pipes may comprise multiple layers including steel and polymer layers, the pipes are, at heart, steel pipes and not composite pipes as presently defined. As a result of these pipes being fundamentally steel pipes, the problems of providing an end-fitting to a composite pipe do not arise. The end-fitting generally comprises a steel flange, which is attached to the underlying steel carcass of the flexible steel, unbonded pipe. This is a metal-to-metal connection, so the challenges which may arise when attaching a steel end-fitting to a composite pipe do not occur.

It is against this background that the present invention has been devised. SUMMARY OF THE INVENTION

According to a first aspect of the invention, a composite pipe termination comprising an end-fitting is provided comprising: a) a composite pipe formed of composite material and having an interior pipe surface, an exterior pipe surface and a pipe end, wherein composite material is a material comprising a polymer matrix and a plurality of reinforcing fibres embedded in the polymer matrix; b) a liner, wherein the interior pipe surface is fused to the linen c) an annular portion of composite material attached to the exterior pipe surface, the annular portion having an external surface comprising a first face; wherein the first face tapers towards the exterior pipe surface in the direction towards the end-fitting, the first face comprising a male thread; d) an annular collar enclosing the pipe end and the first face and having a tapered internal surface comprising a female thread which engages the male thread on the first face, such that the threads lock to provide axial movement blocking means which prevent the annular collar from moving axially relative to the annular portion, wherein the annular collar comprises the end-fitting.

As used herein, the term “end-fitting” means a device intended to attach to another apparatus, such as a pipe, or an end cap, and may comprise a flange, hub or the like.

As used herein, the term “axial” refers to the axis of the composite pipe, which extends longitudinally along the composite pipe.

According to one embodiment, the composite pipe termination of the first aspect of the invention additionally comprises rotational movement blocking means to prevent the annular collar from rotating relative to the annular portion.

According to one alternative of this embodiment, the rotational movement blocking means comprises one or more elongate attachment elements extending radially through the annular collar into the annular portion. The elongate attachment elements may comprise pins, bolts, retaining screws or a mixture thereof.

According to another alternative of this embodiment

- the external surface of the annular portion comprises a second face which tapers towards the exterior pipe surface in the direction away from the pipe end;

- wherein the pipe termination additionally comprises an annular collar extension attached to the annular collar which extends over at least a portion of the second face; and wherein the rotational movement blocking means comprises keyways disposed in the second surface which mate with keys disposed in the annular collar extension.

According to this alternative, the second face may comprise two or more tapered regions, each tapered region having a taper which is at a different angle to the other tapered region(s), the angle being measured relative to a plane normal to the central axis of the composite pipe.

According to another embodiment of the first aspect, the first face may terminate before the pipe end, or the first face may terminate at the pipe end, or the first face may terminate beyond the pipe end.

According to one embodiment of the first aspect, the end-fitting is made of metal, preferably steel.

According to another embodiment of the first aspect, the end-fitting comprises a flange. According to a further embodiment of the first aspect, the polymer matrix comprises thermoplastic polymer. Preferably, the polymer matrix consists of thermoplastic polymer. More preferably, the polymer matrix consists of polyether ether ketone (PEEK).

According to another embodiment of the first aspect, the reinforcing fibres comprise glass fibres, cartoon fibres, or mixtures thereof.

The annular portion may consist of a composite material which may be the same as or different from the composite material of the composite pipe. Preferably, at least the matrix of the annular portion consists of the same material as the matrix of the composite pipe. In such a case, the matrix of the composite material of the annular fuses with the matrix of the composite material of the composite pipe to form a single, unitary material, such that there is no variation in mechanical and physical properties at the interface. This provides a stronger attachment between the exterior pipe surface and annular portion than in the case in which different matrix materials are used. Strong bonds may contribute to achieving high resistance to axial and torsional shear. More preferably, the annular portion consists of a composite material which is the same as the composite material of which the composite pipe consists.

According to an advantageous embodiment of the first aspect, the composite pipe comprises wound tapes of composite material which have been fused together and wherein the polymer matrix consists of thermoplastic polymer. More advantageously, the fibres are continuous along the entire length of each tape.

According to one embodiment of the first aspect, the liner comprises thermoplastic polymer. Preferably, the liner consists of thermoplastic polymer. More preferably, the liner consists of PEEK.

The liner may advantageously consist of the same material of which the matrix of the composite pipe consists, because stronger bonds are likely to result between the interior pipe surface and liner in the case in which the liner and composite pipe matrix are made of the same material than in the case in which different materials are used, for the reasons given above in relation to the discussion of the annular portion. Strong bonds may contribute to achieving high resistance to axial and torsional sheer.

According to another embodiment of the first aspect, the liner comprises an extension portion which extends beyond the pipe end. According to this embodiment, the annular portion extends along at least some of the extension portion to terminate beyond the pipe end and is fused to the extension portion.

Further according to this embodiment, the annular collar may comprise a receiving portion formed to receive the extension portion and form a lip seal, wherein, in use, the lip seal is pressed against the receiving portion by the pressure of fluid contained within the pipe termination to enhance the seal.

According to a second aspect of the invention a method of providing a composite pipe termination comprising an end-fitting is provided, the method comprising: a) providing a composite pipe formed of composite material and having an interior pipe surface, an exterior pipe surface and a pipe end, wherein composite material is a material comprising a polymer matrix and a plurality of reinforcing fibres embedded in the polymer matrix; and wherein the interior pipe surface is fused to a liner; b) attaching an annular portion of composite material to the exterior pipe surface, the annular portion having an external surface; c) providing the external surface with a first face which tapers towards the exterior pipe surface in the direction towards the end-fitting; d) tapping a male thread into the first face; e) providing an annular collar comprising the end-fitting, the annular collar being configured to enclose the pipe end and the first face and having a tapered internal surface comprising a female thread configured to engage the male thread on the first face; f) disposing the pipe end and the annular portion within the annular collar to engage the male thread with the female thread such that the threads lock to provide axial movement blocking means which prevent the annular collar from moving axially relative to the annular portion.

According to one embodiment of the second aspect, b) comprises by winding tapes of composite material onto the exterior pipe surface to create the annular portion.

According to another embodiment of the second aspect, c) comprises removing a portion of the wound tapes to provide the first face which tapers towards the exterior pipe surface in the direction towards the end-fitting.

According to a further embodiment of the second aspect, the method further comprises removing a portion of the wound tapes to provide the external surface of the annular portion with a second face, wherein the second face tapers towards the exterior pipe surface in the direction away from the pipe end.

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 a side-elevation of a composite pipe termination according to a first embodiment of the invention.

Figure 2 shows a perspective view of the annular collar extension shown side- elevation in Figure 1.

Figure 3 shows an exploded perspective view of the end-fitting of Figure 1. Figure 4 shows expanded details of the end-fitting shown in Figure 1 from detail view A.

Figure 5 shows a side-elevation of a composite pipe termination according to a second embodiment of the invention.

Figure 6 shows expanded details of the end-fitting shown in Figure 5 taken from detail view B.

DETAILED DESCRIPTION

A detailed description of the invention will now be provided with reference to the above figures. A given reference number is always used to denote the same feature in each of the accompanying drawings.

Figure 1 shows a side-elevation of a composite pipe termination according to a first embodiment of the invention. Specifically, it shows a composite pipe 1 having an interior pipe surface 1 a, an exterior pipe surface 1 b and a pipe end 1 c. A liner (shown in more detail in Fig.4) is fused to the interior pipe surface.

Typically, the composite pipe consists of wound tapes of composite material which have been fused together. The composite material typically consists of a PEEK matrix and a plurality of carbon fibres embedded therein. The tapes are typically wound onto a PEEK liner.

The composite pipe termination comprises an annular portion 2 fused to the exterior pipe surface 1 b, which annular portion 2 itself comprises composite material. Typically, the annular portion is also manufactured by winding consecutive layers of tapes made of composite material, each layer being fused to the preceding one. The composite material typically consists of a PEEK matrix and a plurality of carbon fibres embedded therein. The annular portion 2 has an external surface comprising a first face 2a, which tapers towards the exterior pipe surface 1 b in the direction towards the end-fitting, which is the flange shown on the right hand side of the figure. First face 2a is provided with a male screw thread. The exterior surface of the annular portion also has a second face 2b, which tapers towards the exterior pipe surface 1 b in the direction away from the pipe end 1c. In this embodiment, second face 2b comprises two portions having different taper angles when measured relative to a plane normal to the central axis of the composite pipe. First face 2a and second face 2b are typically made by removing of a portion of the wound and fused PEEK tapes to form tapered portions. Removal is typically achieved by means of a lathe. A male screw thread is then tapped into first face 2a.

The arrangement of Fig.1 also comprises an annular collar 5 which encloses the pipe end 1 c and the first face 2a. Annular collar 5 comprises the end-fitting, a flange in this case, shown on the right hand side of the figure. The annular collar 5, including the end-fitting, is typically made of steel. The internal surface of the annular collar 5 is provided with a female screw thread. The female screw thread engages the male screw thread on the first face 2a, such that the threads lock to provide axial movement blocking means which prevent the annular collar 5 from moving axially relative to the annular portion 2.

In the arrangement of Fig.1 , the annular collar 5 extends to the apex of the annular portion 2. An annular collar extension 15 extends over a portion of the second surface 2b and the annular collar extension 15 is attached to the annular collar 5 by means of retaining screws 9. The annular collar extension 15 and the retaining screws 9 are typically made of steel.

The annular collar extension 15 comprises keys 17a which mate with keyways 17b, shown in Fig.3, such that, together they provide rotational movement blocking means to prevent the annular collar 5 from rotating relative to the annular portion 2.

The keys 17a are shown in more detail in Figure 2, which shows a perspective view of the annular collar extension 15. Figure 3 shows an exploded perspective view of the end-fitting of Figure 1. Keyways 17b are visible in this figure.

Figure 4 shows an expanded detail of the end-fitting shown in Figure 1 from detail “A”. In this figure, liner 1d is shown to have an extension portion, which is a portion of the liner which extends beyond the pipe end (the pipe end is located on the far left, out of this figure). Annular collar 5 is shown in this figure to have a receiving portion 5a machined into it which receives part of the extension portion to form a lip seal. In use, the extension portion is pressed against the receiving portion by the pressure of fluid flowing through the composite pipe termination to enhance the seal.

Figure 5 shows a side-elevation of a composite pipe termination according to a second embodiment of the invention. Specifically, it shows a composite pipe 1 having an interior pipe surface 1a, an exterior pipe surface 1 b and a pipe end 1c. A liner is fused to the interior pipe surface. The pipe 1 comprises an annular portion 2, which itself comprises composite material. The annular portion 2 has an external surface comprising a first face 2a, which tapers towards the exterior pipe surface 1 b in the direction towards the end fitting and which is provided with a male screw thread.

Typically, the elements of the second embodiment are made of the same materials as those described in relation to the same elements in the first embodiment.

The arrangement of Fig.5 also comprises an annular collar 5 which encloses the pipe end 1 c and the first face 2a. Annular collar 5 comprises an end-fitting on the right hand side of the figure, which in this case is a flange. The internal surface of the annular collar 5 is provided with a female screw thread. The female screw thread engages the male screw thread on the first face 2a, such that the threads lock to provide axial movement blocking means which prevent the annular collar 5 from moving axially relative to the annular portion 2.

The arrangement of Fig.5 additionally comprises retaining screws 90 which extend radially through the annular collar 5 into the annular portion 2. Retaining screws 90 provide rotational blocking means to prevent annular collar 5 from rotating relative to the annular portion 2. In the embodiment shown, retaining screws pass radially into the annular portion only at the apex of the annular portion, but it is possible to provide retaining screws 90 which extend radially through the annular collar 5 into the annular portion 2 at alternative locations or at multiple locations along the entire length of the annular portion. Retaining screws 90 are shown in magnified form taken from detail view B, which is shown in Figure 6. Detail view C relates to the lip seal and is identical to detail view A, shown in Fig.4.