AN UNBONDED FLEXIBLE PIPE

Abstract

A subsea installation including an unbonded flexile pipe for subsea transportation of a H.sub.2S and/or CO.sub.2 containing fluid. The unbonded flexible pipe includes from inside and out, a pressure sheath defining a bore for transportation of the fluid, a tensile armor and a liquid impervious outer sheath, wherein the tensile armor is of corrosion resistant material(s) and the tensile armor includes at least two cross wound layers of elongate armor elements, which are wound with a long pith and wherein the pipe further includes an anti-bird cage layer including at least one elongate element wound with a short pitch onto at least one of the tensile armor layers, and wherein the at least one elongate element includes or consist of steel, titanium and/or fibers of carbon, basalt, polyethylene, PVDF (polyvinylidene fluoride or polyvinylidene difluoride) PEEK (polyether ether ketone) PVC (polyvinyl chloride), LCP (liquid crystalline polymer) or any combinations thereof.

Claims

1. A subsea installation comprising an unbonded flexile pipe for subsea transportation of a H.sub.2S and/or CO.sub.2 containing fluid, the unbonded flexible pipe comprises from inside and out, a pressure sheath defining a bore for transportation of the fluid, a tensile armor and an outer sheath, wherein the tensile armor is located in an annulus and is of corrosion resistant material(s) and the tensile armor comprises at least two cross wound layers of elongate armor elements, which are wound with a long pith and wherein the pipe further comprises an anti-bird cage layer comprising at least one elongate element wound with a short pitch onto at least one of the tensile armor layers, and wherein said at least one elongate element comprises or consist of steel, titanium and/or fibers of carbon, basalt, polyethylene, PVDF (polyvinylidene fluoride or polyvinylidene difluoride) PEEK (polyether ether ketone) PVC (polyvinyl chloride), LCP (liquid crystalline polymer) or any combinations thereof.

2. The subsea installation of claim 1, wherein the pressure sheath and the outer sheath forms said annulus.

3. The subsea installation of claim 1, wherein the unbonded flexile pipe is arranged for subsea transportation of an acidic crude oil and/or gas, at a raised temperatureof at least 30° C. inside the bore of the pipe.

4. The subsea installation of claim 1, wherein the unbonded flexile pipe is arranged for subsea transportation of a sour fluid comprising at least about 0.5% by weight of sulfur or comprising at least about 100 ppm of H.sub.2S.

5. (canceled)

6. The subsea installation of claim 1, wherein the unbonded flexile pipe is arranged for subsea transportation of fluid containing at least about 100 ppm of CO.sub.2 or containing at least about 10 mol % of CO.sub.2.

7. (canceled)

8. (canceled)

9. The subsea installation of claim 1, wherein the pH value in at least a location of the annulus is about 4.5 or less.

10. (canceled)

11. The subsea installation of claim 1, wherein the fluid is a CO.sub.2 containing injection fluid and the unbonded flexile pipe is arranged for transporting the injection fluid at least a part of a way from a sea surface installation to a seabed installation.

12. The subsea installation of claim 1, wherein at least a length section of the unbonded flexible pipe is located at least about 100 m below sea surface.

13. The subsea installation of claim 1, wherein the elongate element of the anti-bird cage layer is wound with an angle of at least about 65° to the center axis of the unbonded flexible pipe and wherein the elongate element of the anti-bird cage layer comprises fibers of stainless steel, titanium, carbon, basalt, ultra-high-molecular polyethylene (UHMWPE) LCP (liquid crystalline polymer), or any combinations thereof.

14. (canceled)

15. (canceled)

16. (canceled)

17. (canceled)

18. The subsea installation of claim 1, wherein the fibers are embedded in a polymer material, wherein the polymer material is polyethylene, PVDF, PEEK, PVC or any combination thereof, and wherein the fibers are dispersed in the embedding material which is in the form of flat tapes, with a thickness of from 0.2 mm to 3 mm.

19. (canceled)

20. (canceled)

21. (canceled)

22. (canceled)

23. (canceled)

24. The subsea installation of claim 18, wherein the anti-bird cage layer comprises a steel strip or a titanium strip.

25. The subsea installation of claim 1, wherein the unbonded flexible pipe comprises two or more anti-bird cage layers.

26. (canceled)

27. (canceled)

28. The subsea installation of claim 1, wherein the anti-bird cage layer is located in the annulus in physical contact with at least one of the tensile armor layers.

29. The subsea installation of claim 1, wherein the unbonded flexible pipe further comprises a stabilization layer located outside the tensile armor layers and wherein the anti-bird cage layer is located onto and in contact with said stabilization layer, and wherein the stabilization layer is made from helically wound polymeric strips.

30. (canceled)

31. The subsea installation of claim 29, wherein the helically wound polymeric strips are wound with a longer pitch than the pitch of the at least one elongate element of the anti-bird cage layer, the helically wound polymeric strips are wound with an angle to the center axis of the unbonded flexible pipe, which is at least about 10° less than the winding angle of the elongate element(s) of the anti-bird cage layer.

32. (canceled)

33. (canceled)

34. (canceled)

35. (canceled)

36. The subsea installation of claim 1, wherein the corrosion resistant material(s) comprises stainless steel, titanium, composite material or any combinations thereof and wherein the composite material comprises a fiber reinforced polymer material.

37. (canceled)

38. (canceled)

39. (canceled)

40. The subsea installation of claim 1, wherein the unbonded flexible pipe comprises a pressure armor located between the pressure sheath and the tensile armor, the pressure armor is of one or more of the corrosion resistant material(s).

41. (canceled)

42. (canceled)

43. (canceled)

44. (canceled)

45. An unbonded flexile pipe for subsea transportation of a H.sub.2S and/or CO.sub.2 containing fluid, the unbonded flexible pipe comprises from inside and out, a pressure sheath defining a bore for transportation of the fluid, a tensile armor and a liquid impervious outer sheath, wherein the tensile armor is of corrosion resistant material(s) and the tensile armor comprises at least two cross wound layers of elongate armor elements, which are wound with a long pith and wherein the pipe further comprises an anti-bird cage layer comprising at least one elongate element wound with a short pitch onto at least one of the tensile armor layers, and wherein said at least one elongate element comprises or consist of steel, titanium and/or fibers of carbon, basalt, polyethylene, PVDF (polyvinylidene fluoride or polyvinylidene difluoride) PEEK (polyether ether ketone) PVC (polyvinyl chloride), LCP (liquid crystalline polymer) or any combinations thereof.

Description

BRIEF DESCRIPTION OF THE EXAMPLES AND DRAWING

[0093] The invention is being illustrated further below in connection with illustrative embodiments and with reference to the figures. The figures are schematic and may not be drawn to scale.

[0094] FIG. 1 is a schematic, perspective view of an unbonded flexible pipe forming part of an embodiment of the installation.

[0095] FIG. 2 is a schematic, side view and partly cross-sectional view of an unbonded flexible pipe forming part of an embodiment of the installation.

[0096] FIG. 3 illustrates an installation according to an embodiment of the invention FIGS. 4a-4e are cross-sectional views of an embodiments of anti-bird cage layer elongate elements.

[0097] FIG. 5 is a schematic, side view of an unbonded flexible pipe forming part of an embodiment of the installation.

[0098] FIG. 6 is a schematic, side view of a further unbonded flexible pipe forming part of an embodiment of the installation.

[0099] FIG. 7 is a schematic, side view of a further unbonded flexible pipe forming part of an embodiment of the installation.

[0100] The unbonded flexible pipe shown in FIG. 1 comprises from inside and out a carcass 2, a pressure sheath 3, a pressure armor 4, a tensile armor comprising an innermost tensile armor layer 5 and an outermost tensile armor layer 6, an anti-bird cage layer 1 and a liquid impervious outer sheath 7.

[0101] The carcass is liquid pervious and the pressure sheath 3 defines the bore 8. An annulus is formed between the pressure sheath 3 and the outer sheath 7.

[0102] The elongate elements of tensile armor layers 5, 6 are cross wound with a long pitch and the elongate element of the pressure armor is wound with a short pitch. The anti-bird cage layer consists of one or more anti-bird cage elongate elements wound with a short pitch, advantageously wound with an angle to the center axis of the pipe of at least about 65°, preferably at least about 75° or even higher. In principle the higher the winding angle, the more will the anti-bird cage layer counteract radial buckling forces of the tensile armor elements.

[0103] The pressure armor and the tensile armor is made of corrosion resistant material(s) and the elongate element(s) of the anti-bird cage layer 1 is made of one or more of steel, titanium and/or fibers of carbon, basalt, polyethylene, PVDF (polyvinylidene fluoride or polyvinylidene difluoride) PEEK (polyether ether ketone) PVC (polyvinyl chloride) and LCP (liquid crystalline polymer). The anti-bird cage elongate element(s) is shapes as flat strips e.g. as in FIGS. 4a-4e.

[0104] In the installation the unbonded flexible pipe will transport a H.sub.2S and/or CO.sub.2 containing fluid. Since the pressure armor and the tensile armor is made of corrosion resistant material(s), the pH value in the annulus drastically drop for example to pH 4 or even pH 3.5 or less. Due to the selections of the material(s) of the anti-bird cage layer elongate element(s), the anti-bird cage protection may have a long durability and preferably remain stable in the entire service time of the pipe.

[0105] The unbonded flexible pipe shown in FIG. 2 comprises a carcass 12 manufactured by winding and folding a metallic tape 12a in such a way that the turns of the tape interlock with each other and thereby limit the displacement between the turns. Around the carcass layer 12, a pressure sheath 13 is arranged. Around the pressure sheath 13, two pressure armor layers 14a, 14b are helically wound with a short pitch. The pressure armor layers 14a, 14b are made of elongate elements in the form of profiled armor wires, where the profile of the wire(s) of the innermost pressure armor layer 14a matches the profile of the wire(s) of the outermost pressure armor layer 14b.

[0106] Around the armor layers 14a, 14b, two tensile armor layers 15, 16 are cross wound with a long pitch.

[0107] Around the outermost tensile armor layer 16, two or more anti-bird cage layers are applied in the form of elongate elements of cords or bundles of cords of carbon fibers which are wound with a short pitch.

[0108] Between the armor layers, optional anti friction layers may be inserted e.g. to lower the friction between the layers, here illustrated in the form of layer 18. Such anti friction layers may advantageously be made of PVDF.

[0109] Similarly, a PVDF layer (here comprising wound PVDF tape) 19 may be applied between the outermost tensile armor layer 16 and the anti-bird cage layers 11.

[0110] The unbonded flexible pipe further comprises a liquid impervious outer sheath 17.

[0111] The unbonded flexible pipe shown in FIG. 5 comprises a carcass 42 preferably comprising interlocked wound elements. Around the carcass layer 42, a pressure sheath 43 is located. Around the pressure sheath 43, a pressure armor 44 is located. The pressure armor is advantageously of wound interlocked elements of corrosion resistant material(s), preferably stainless steel.

[0112] Around the pressure armor 44, two tensile armor layers 45, 46 are cross wound with a long pitch. The tensile armor layers are advantageously of wound elongate elements of corrosion resistant material(s), preferably stainless steel.

[0113] Outside the outermost tensile armor layer 46, a stabilization layer 49 is located. The stabilization layer is provided by helically wound polymeric strips, preferably wound with a winding angle to the center axis of the unbonded flexible pipe, which is low relative to the winding angle of the elongate element(s) of the anti-bird cage layer 41, which is wound onto the stabilization layer 49. The stabilization layer 41 may conveniently have one or more of the functions mentioned above.

[0114] Outside the anti-bird cage layer, the outer sheath 47 is located.

[0115] The unbonded flexible pipe shown in FIG. 6 comprises a carcass 52 preferably comprising interlocked wound elements. Around the carcass layer 52, a pressure sheath 53 is located. Around the pressure sheath 53, a pressure armor 54 is located. The pressure armor is advantageously of wound interlocked elements of corrosion resistant material(s), preferably stainless steel.

[0116] Around the pressure armor 54, two tensile armor layers 55, 56 are cross wound with a long pitch. The tensile armor layers are advantageously of wound elongate elements of corrosion resistant material(s), preferably stainless steel.

[0117] Outside the outermost tensile armor layer 56, the outer sheath is located, preferably in directly physical contact with the outermost tensile armor layer 56. The anti-bird cage layer 51 is located outside the annulus and is applied directly onto the outer sheath 57. A not shown mechanical protection layer may be located outside the anti-bird cage layer.

[0118] The unbonded flexible pipe shown in FIG. 7 comprises a carcass 62 preferably comprising interlocked wound elements. Around the carcass layer 62, a pressure sheath 63 is located. Around the pressure sheath 63, a pressure armor 64 is located. The pressure armor is advantageously of wound interlocked elements of corrosion resistant material(s), preferably stainless steel.

[0119] Around the pressure armor 64, two tensile armor layers 65, 66 are cross wound with a long pitch. The tensile armor layers are advantageously of wound elongate elements of corrosion resistant material(s), preferably stainless steel.

[0120] Outside the outermost tensile armor layer 66, a stabilization layer 69 is located. The stabilization layer is conveniently as described above. An anti-bird cage layer 61a, is wound onto the stabilization layer 69.

[0121] Outside the anti-bird cage layer, the outer sheath 67 is located. An additional back up anti-bird cage layer 61b is located outside the annulus and is applied directly onto the outer sheath 67. The additional back up anti-bird cage layer 61b serves as a back up layer outside the annulus and may serve as an extra protection in case the anti-bird cage layer in the annulus should be damaged.

[0122] The subsea installation disclosed in FIG. 3 comprises a sea surface installation 21, preferably located at the sea surface S and a seabed installation 22, such as a well and/or a production site.

[0123] Two pipelines 23, 24, 25 are arranged to transfer a fluid between the sea surface installation 21 and the seabed installation 22. A first pipeline 23, 24 is arranged to transport a H.sub.2S and/or CO.sub.2 containing fluid from the seabed installation 22 to the sea surface installation 21. The first pipeline 23, 24 comprises a flow line pipe, 24 and a riser pipe 23 interconnected via end-fittings 26. A second pipeline 25 is arranged to transport CO.sub.2 gas from the sea surface installation 21 to the seabed installation 22, e.g. for injection. At least one and preferably two or all three of the second pipeline 25, the flow line pipe 24 and the riser pipe 23 is an unbonded flexible pipe ad described herein and comprising an anti-bird cage layer is made of one or more of steel, titanium and/or fibers of carbon, basalt, polyethylene, PVDF (polyvinylidene fluoride or polyvinylidene difluoride) PEEK (polyether ether ketone) PVC (polyvinyl chloride) and LCP (liquid crystalline polymer).

[0124] Examples of elongate elements of the anti-bird cage layer are shown in FIG. 4a-4e.

[0125] The elongate element shown in FIG. 4a comprises bundles 30 of twisted or untwisted continuous fibers embedded in an embedding material 31 and are shaped in the form of flat tapes. The bundles of twisted or untwisted continuous fibers are arranged to have their length orientated parallel with the length L of the elongate element. As indicated with the “L” the elongate element may be very long and preferably practically “endless”. This mean that lengths if the elongate element may be coupled to form the practically endless elongate element.

[0126] The elongate element shown in FIG. 4b differs from the elongate element of FIG. 4a in that it comprises a larger number of comprises bundles 30 of twisted or untwisted continuous fibers.

[0127] The elongate element shown in FIG. 4c comprises cords of continuous fibers 32 embedded in an embedding material. The cords of continuous fibers 32 are arranged to have their length orientated parallel with the length L of the elongate element.

[0128] The elongate element shown in FIG. 4d is shaped as a tape and comprises a top portion P and a bottom portion T. The bottom portion B comprises bundles 30 of twisted or untwisted continuous fibers embedded in an embedding material 31. The top portion T comprises cut fibers 35 dispersed in the embedding material. This elongate element is specifically advantageously where the elongate element is part of an anti-bird cage layer which simultaneously form a thermal insulation. The bottom portion B is advantageously closer to the tensile armor layer than the top portion T of the elongate element. Thereby the bottom portion ensures a high anti-bird cage effect, whereas the top portion may insure a good insulation. The cut fibers 35 in the top portion T of the elongate element may have the function of protecting the top portion T against compression due to a high hydrostatic pressure.

[0129] The elongate element shown in FIG. 4e is also shaped as a tape and comprises a top portion P and a bottom portion T. The bottom portion B comprises a strip 31 of steel or titanium embedded in an embedding material 33. The top portion T comprises cords of continuous fibers 32 embedded in an embedding material.

[0130] This elongate element is also very beneficial where the elongate element is part of an anti-bird cage layer which simultaneously form a thermal insulation. The bottom portion B is advantageously closer to the tensile armor layer than the top portion T of the elongate element. Thereby the bottom portion ensures a high anti-bird cage effect, whereas the top portion may insure a good insulation. The continuous fibers 32 in the top portion T of the elongate element may have the function of protecting the top portion T against compression due to a high hydrostatic pressure