TUBING CONNECTOR FOR COMPOSITE TUBING, COMPOSITE TUBING, AND METHODS OF USING THE SAME

Abstract

A tubing segment is provided for construction of tubing for transporting a fluid, and a tubing connector, tubing for carrying a fluid, the tubing comprising a plurality of tubing segments, a production or injection installation comprising a subsurface well and tubing, methods of manufacturing tubing, methods of connecting two tubing segments, and a method of producing mineral oil or natural gas from a subsurface reservoir, such as a well.

Claims

1. Tubing segment (10) for construction of tubing for transporting a fluid, the tubing segment comprising; a sheath (20) comprising; an inner liner (1); an outer wall (2); a first open end (21); and a second open end (22), said sheath extending between the first open end and the second open end; and a tubing connector (3), wherein the first open end of the sheath is connected to the tubing connector, said tubing connector comprising: a male coupling end having a tapered outer surface, wherein said tapered outer surface has a decreasing diameter, moving away from the first open end of the sheath; or a female coupling end having a flared inner surface, wherein said flared inner surface has an increasing diameter, moving away from the first open end of the sheath, wherein said tapered outer surface or said flared inner surface comprises a number of attachment members, said number of attachment members being arranged to interlock with an opposing set of attachment members on a surface of an opposing tubing connector.

2. The tubing segment according to claim 1, further comprising a second tubing connector, wherein the second open end of the sheath is connected to the second tubing connector, said second tubing connector comprising: a male coupling end having a tapered outer surface, wherein said tapered outer surface has a decreasing diameter, moving away from the first open end of the sheath; or a female coupling end having a flared inner surface, wherein said flared inner surface has an increasing diameter, moving away from the first open end of the sheath, wherein said tapered outer surface or said flared inner surface comprises a number of attachment members, said number of attachment members being arranged to interlock with an opposing set of attachment members on a surface of an opposing tubing connector.

3. The tubing segment according to any of the preceding claims, wherein the first open end of the sheath is connected to a tubing connector comprising a male coupling end and wherein the second open end of the sheath is connected to a second tubing connector comprising a female coupling end.

4. The tubing segment according to any of the preceding claims, wherein the female coupling end comprises a passage connecting an outer surface of the female coupling end to the flared inner surface, said passage being arranged to allow pressurized fluid to be injected between the flared inner surface of the female coupling end and a tapered outer surface of a male coupling end of an opposing tubing connector.

5. The tubing segment according to any of the preceding claims, wherein the attachment members are circumferential grooves, preferably wherein the circumferential grooves are axially spaced.

6. The tubing segment according to any of the preceding claims, wherein the inner liner comprises an isotropic material.

7. The tubing segment according to any of the preceding claims, wherein the inner liner has a rupture strain rate of more than about 0.5%, preferably of more than about 5%, more preferably of more than about 20%.

8. The tubing segment according to any of the preceding claims, wherein the inner liner comprises metal and/or metal alloys.

9. The tubing segment according to claim 8, wherein the inner liner comprises one or more of steel, nickel alloys, nickel chrome, nickel copper alloys, titanium, titanium alloys.

10. The tubing segment according to claim 8 or 9, wherein the inner liner is welded to the tubing connector and/or to the second tubing connector.

11. The tubing segment according to any of the preceding claims, wherein the tubing connector and/or the second tubing connector comprises titanium, preferably a high yield strength grade titanium, more preferably grade 4 titanium and/or grade 5 titanium and/or grade 12 titanium.

12. The tubing segment according to any of the preceding claims, wherein the inner liner and the tubing connector both comprise titanium, preferably wherein the second tubing connector also comprises titanium.

13. The tubing segment according to any preceding claim, wherein the tubing segment has a density that of lower than about 3000 kg/m.sup.3 at 25 degrees Celsius, preferably lower than about 2000 kg/m.sup.3 at 25 degrees Celsius, more preferably lower than about 1800 kg/m.sup.3 at degrees Celsius, still more preferably lower than about 1500 kg/m.sup.3 at 25 degrees Celsius.

14. The tubing segment according to any preceding claim, wherein the outer wall comprises a fiber-reinforced material.

15. The tubing segment according to claim 14, wherein the outer wall comprises fibers within a thermoset polymer matrix.

16. The tubing segment according to claim 15, wherein the thermoset polymer matrix comprises at least an epoxy resin.

17. The tubing segment according to claim 15 or 16, wherein the thermoset polymer matrix comprises one or more of polyester, epoxy, dicyclopentadiene, polyurethane, phenolic polymers, bismaleimide resin, and/or phthalonitrile.

18. The tubing segment according to any of claims 15 to 17, wherein the thermoset polymer matrix material has a glass transition temperature of at least about 120 degrees Celsius, preferably of at least about 160 degrees Celsius, more preferably of at least about 180 degrees Celsius, still more preferably of at least about 200 degrees Celsius, most preferably of at least about 220 degrees Celsius.

19. The tubing segment according to claim 14, wherein the outer wall comprises fibers within a thermoplastic polymer matrix, preferably comprising one or more of polyolefin, polyethylene, polyamide, polyvinylidene fluoride, polyether ether ketone.

20. The tubing segment according to any of claims 14 to 19, wherein the fibers of the fiber-reinforced material comprise one or more of carbon fiber, glass fiber, aramid fiber, and/or basalt fiber.

21. The tubing segment according to any of claims 14 to 20, wherein the fiber-reinforced material comprises pitch based carbon fiber and/or pan based carbon fiber.

22. The tubing segment according to any of claims 14 to 21, wherein the fiber-reinforced material has an ultimate tensile strength of between 2500 and 8000 MPa, preferably of between 5000 and 8000 MPa, more preferably of between 7000 and 8000 MPa.

23. The tubing segment according to any of claims 14 to 22, wherein the fiber-reinforced material has a modulus of elasticity of between 60 and 590 GPa, preferably of between 200 and 400 GPa, more preferably of between 200 and 250 GPa.

24. The tubing segment according to any of claims 14 to 23, wherein the fiber-reinforced material comprises PX35 and/or T700 carbon fiber.

25. The tubing segment according to any of the preceding claims, wherein the tubing segment has an uninterrupted length of between about 2 and 100 meters, preferably of between about 4 and 50 meters, more preferably of between 8 and 20 meters, most preferably of about 12 meters.

26. The tubing segment according to any of the preceding claims, wherein the sheath has an outer diameter of less than about 500 millimeters, preferably of less than about 350 millimeters, more preferably of less than about 140 millimeter, still more preferably of less than about 70 millimeters.

27. The tubing segment according to any of the preceding claims, wherein the sheath has an inner diameter of more than about 45 millimeters, preferably of more than about 80 millimeters, more preferably of more than about 125 millimeters, still more preferably of more than about 300 millimeters.

28. The tubing segment according to any of the preceding claims, wherein the sheath has a wall thickness of less than about 60 millimeters, preferably of less than about 40 millimeters, more preferably of less than about 30 millimeters, still more preferably less than about 20 millimeters, and most preferably of less than about 5 millimeters.

29. The tubing segment according to any of the preceding claims, wherein the outer wall comprises a fiber-reinforced material; and wherein the tubing connector and/or the second tubing connector comprises a binding end, wherein the fiber-reinforced material of the outer wall of the sheath binds to the binding end of the tubing connector and/or the second tubing connector.

30. The tubing segment according to claim 29, wherein the binding end of the tubing connector and/or the second tubing connector comprises fiber-deflecting units, wherein said fiber-deflecting units are arranged to guide fibers of the fiber-reinforced material of the outer wall over the binding end of the tubing connector and/or the second tubing connector.

31. The tubing segment according to claim 30, wherein an outer surface of the binding end of the tubing connector and/or the second tubing connector, comprises fiber-reception grooves as the fiber-deflection units, wherein the fibers extend over the binding end, through the fiber-reception grooves.

32. The tubing segment according to claim 30, wherein an outer surface of the binding end of the tubing connector and/or the second tubing connector comprises radially extending projections as the fiber-deflection units, wherein the fibers extend over the binding end, and are disposed between the projections.

33. A tubing connector (3), comprising: a binding end (4); and a male coupling end (6) having a tapered outer surface, wherein said tapered outer surface has a decreasing diameter, moving away from the binding end; or a female coupling end (5) having a flared inner surface (51), wherein said flared inner surface has an increasing diameter, moving away from the binding end, wherein said binding end comprises fiber-deflecting units (7), arranged to guide fibers of a fiber-reinforced outer wall of a tubular over the binding end.

34. The tubing connector according to claim 33, wherein said tapered outer surface or said flared inner surface comprises a number of attachment members (8), said number of attachment members (8) being arranged to interlock with an opposing set of attachment members on a surface of an opposing tubing connector, wherein preferably the attachment members are circumferential grooves.

35. The tubing connector according to claim 33 or 34, wherein the fiber-deflection units comprise fiber-reception grooves in an outer surface of the binding end, wherein the grooves are arranged to guide the fibers over the first binding end.

36. The tubing connector according to claim 33 or 34, wherein an outer surface of the binding end comprises radially extending projections as the fiber-deflection units, wherein the radially extending projections are arranged to retain the fibers on the binding end.

37. The tubing connector according to claim 36, wherein the projections are conical or rounded and/or wherein the projections comprise a cylindrical stem.

38. The tubing connector according to claim 36 or 37, wherein the projections have a maximum diameter of between 1 mm and 15 mm, preferably between 2 mm and 10 mm, more preferably between 3 mm and 8 mm, most preferably between 4 and 6 mm.

39. The tubing connector according to any of claims 36 to 38, wherein the projections are distributed over the binding end, in the form of a regular pattern and/or with a density gradient and/or with a constant density.

40. The tubing connector according to any of claims 36 to 39, wherein the ratio of the distance between two projections to the diameter of the projections is greater than 1, preferably greater than 3.

41. The tubing connector according to any of claims 39 to 40, wherein the density of the projections is at most 1 projection per square centimeter, preferably per 2 square centimeter, more preferably per 5 square centimeter.

42. Tubing for carrying a fluid, said tubing comprising a plurality of tubing segments in accordance with any of claims 1 to 32, said tubing segments being connected in series, preferably wherein said tubing segments are connected with at least two tubing connectors in accordance with any of claims 33 to 41.

43. A production or injection installation comprising a subsurface well and tubing according to claim 42, said tubing being located in the subsurface well.

44. Method of manufacturing tubing, the method comprising the steps of: providing an inner liner; connecting a tubing connector according to any of claims 33 to 41 to the inner liner; winding a fibrous material around the inner liner and at least a part of the tubing connector; providing a polymer material to the fibrous material; and preferably impregnating the fibrous material with a polymer resin.

45. The method of claim 44, wherein the polymer material is a thermosetting polymer material, the method further comprising the step of curing the thermosetting polymer material, preferably by heating the thermosetting polymer material.

46. The method of claim 44 or 45, wherein the inner liner comprises a metal, wherein preferably the inner liner is welded to the tubing connector.

47. The method of claim 45 or 46, wherein the thermosetting polymer is heated via induction heating.

48. The method of any of claims 44 to 47, wherein an electrically conducting additive is provided in the polymer material.

49. The method of any of claims 44 to 48, wherein the inner liner and the tubing connector comprise titanium.

50. Method of connecting two tubing segments, comprising the steps of: providing a first tubing segment, said tubing segment being in accordance with any of claims 1 to 32; providing a second tubing segment, said tubing segment being in accordance with any of claims 1 to 32; wherein the first tubing segment comprises a tubing connector comprising a male coupling end and wherein the second tubing segment comprises a tubing connector comprising a female coupling end, positioning the male coupling end of the first tubing segment in line with the female coupling end of the second tubing segment; partially sliding the tapered outer surface of the male coupling end into the flared inner surface of the female coupling end; and securing the attachment members of the tapered outer surface between the attachment members of the flared inner surface to secure the male coupling end in the female coupling end, preferably wherein the attachment members are circumferential grooves.

51. The method of claim 50, wherein the step of securing the attachment members, preferably circumferential grooves, comprises: injecting a fluid, preferably oil, under pressure between the male coupling end and the female coupling end, wherein the fluid creates a space between the tapered outer surface of the male coupling end and the flared inner surface of the female coupling end, thereby pushing the attachment members of the flared inner surface away from the attachment members of the tapered outer surface, fully sliding the tapered outer surface of the male coupling end into the flared inner surface of the female coupling end, thereby completing the insertion and aligning the attachment members of the tapered outer surface with the attachment members of the flared inner surface, releasing the pressure of the fluid, thereby reducing the space between the tapered outer surface and the flared inner surface to allow interlocking the attachment members of the tapered outer surface and the attachment members of the flared inner surface.

52. Method of producing mineral oil or natural gas from a subsurface reservoir, comprising the steps of; providing tubing according to claim 42 in a subsurface reservoir; and extracting subsurface oil or gas through the tubing to provide said mineral oil or natural gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0078] The features and advantages of the invention will be appreciated upon reference to the following drawings, in which:

[0079] FIG. 1 is an isometric schematic view of the sheath of the tubing segment according to an embodiment of the present invention;

[0080] FIG. 1A is a cross-sectional view of the sheath of FIG. 1 according to an embodiment of the present invention;

[0081] FIG. 2 is an isometric view of a tubing connector according to an embodiment of the present invention;

[0082] FIG. 3 is a side view of the tubing connector of FIG. 2 according to an embodiment of the present invention;

[0083] FIG. 4 is a longitudinal cross-sectional view of the tubing connector of FIGS. 2 and 3, taken at the line A-A of FIG. 3, according to an embodiment of the present invention; and

[0084] FIG. 5 is an isometric view of a tubing connector according to an embodiment of the present invention; and

[0085] FIG. 6 is a longitudinal cross-sectional view of the tubing connector of FIG. 5 according to an embodiment of the present invention; and

[0086] FIG. 7 is an isometric view of a tubing connector according to an embodiment of the present invention; and

[0087] FIG. 8 is a longitudinal cross-sectional view of the tubing connector of FIG. 7 according to an embodiment of the present invention; and

[0088] FIG. 9 is a cut-out view of the tubing connector according to an embodiment of the present invention, connected to the tubing segment according to an embodiment of the present invention; and

[0089] FIG. 10 is a front view of the tubing connector, connected to the inner liner of the sheath of the tubing segment according to an embodiment of the present invention;

[0090] FIG. 11 is a cross-sectional view of one side of tubing according to an embodiment of the present invention, showing a female coupling end and a male coupling end in connected state;

[0091] FIG. 12 is a flow chart illustrating a method of manufacturing tubing in accordance with an embodiment of the present invention; and

[0092] FIG. 13 is a flow chart illustrating a method of coupling two tubing segments in accordance with an embodiment of the present invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0093] The following is a description of certain embodiments of the invention, given by way of example only and with reference to the drawings.

[0094] Referring to FIG. 1, an isometric schematic view of the sheath 20 of the tubing segment 10 according to an embodiment of the present invention is shown. The sheath 20 comprises an inner liner 1 and an outer wall 2. The inner liner 1 is exposed as the outer wall 2 is retracted. In normal operation, the outer wall 2 would extend over the entire length of the sheath 20. The sheath 20 further comprises a first open end 21 and a second open end 22. The first open end 21 of the sheath 20 is to be connected to a tubing connector 3 according to the invention.

[0095] Referring to FIG. 1A a cross-sectional view of the sheath 20 of FIG. 1 according to an embodiment of the present invention is shown. The cross-sectional view of the sheath 20 shows the inner liner 1 surrounded by the outer wall 2. In a preferred embodiment, the outer wall 2 and the inner liner 1 directly contact one another. In other embodiments of the invention, further layers of tubing may be disposed between the inner liner 1 and the outer wall 2. As shown in the figure, the outer wall 2 has a greater thickness than the inner liner 1. The outer wall 2 provides a high degree of structural integrity to the sheath 20 and thus to the tubing segment 10. The inner liner 1 preferably comprises an isotropic impermeable material which mitigates the effects of potential microcracks in the surface of the outer wall 2 of the tubing segment 10.

[0096] Referring to FIG. 2, an isometric view of a tubing connector 3 according to an embodiment of the present invention is shown. Referring also to FIG. 3, a side view of the tubing connector of FIG. 2 is shown. The tubing connector 3 comprises a binding end 4 and a female coupling end 5. The binding end 4 comprises a number of fiber-deflecting units 7, arranged to guide fibers 23 of the outer wall 2 over the binding end 4 of the tubing connector 3. The fiber-deflecting units 7 help prevent slipping of the fibers 23 of the outer wall 2 during binding. As a result, the fiber-deflecting units 7 lead to increased strength of the connection between the tubing connector 3 and the sheath 20 of the tubing segment 10. In the shown embodiment, the fiber deflecting units 7 are projections extending from the surface of the binding end 4 of the tubing connector 3. These projections are formed by cutting away material therebetween, e.g. by milling. In the shown embodiment substantially triangular elements are formed to gradually guide the fibers 23 of the outer wall 2 in a curved manner so that they can fall in a circumferential trench 71. The trench 71 is arranged to receive the fibers 23 of the outer wall 2 and spool them so that they adhere to the binding end 4 of the tubing connector 3. Provision of the fiber-deflecting units 7 may allow for a reduced depth of the trenches 71, as they aid in preventing slipping of the fibers 23 off the outer wall 2.

[0097] Referring to FIG. 4, a longitudinal cross-sectional view of the tubing connector of FIGS. 2 and 3 is shown, taken at the line A-A of FIG. 3. The cross-sectional view clearly shows the shape of the trenches 71 in relation to the substantially triangular projections of the fiber-deflecting units 7. The shown embodiment comprises a female coupling end 5 having a flared inner surface 52, onto which attachment members 8 are disposed, which are not shown in the figure. The flared inner surface 52 of the female coupling end 5 has an increasing diameter, when moving away from the binding end 4 of the tubing connector. It shall be appreciated that this is the other way around for a male coupling end 6, which would have a tapered outer surface 62. The tapered outer surface 62 of a male coupling end 6 would also comprise attachment members 8. As can be seen in the cross-sectional view, not much material is needed to form the tubing connector 3. At the point where the binding end 4 of the tubing connector 3 starts to increase in thickness, the inner diameter of the flared surface 52 starts to increase as well, thereby reducing the wall thickness of the tubing connector 3. As a result, the tubing connector 3 has relatively low material costs.

[0098] Referring to FIG. 5, an isometric view of another tubing connector according to an embodiment of the present invention is shown. Referring to FIG. 6, a longitudinal cross-sectional view of the tubing connector of FIG. 5 according to an embodiment of the present invention is shown. As seen in the isometric view of FIG. 5, the tubing connector 3 comprises a binding end 4 and a female coupling end 5. The binding end 4 comprises fiber-deflecting units in the form of fiber-reception grooves disposed on the wall sections between the four circumferential trenches 71. In a preferred embodiment, these fiber-reception grooves are milled into the surface of the tubing connector. These fiber-reception grooves work in substantially the same way as the substantially triangular projections as shown in FIG. 2. The fibers 23 of the outer wall 2 of the sheath 20 are wound around the inner liner 1 of the sheath and disposed over at least a part of the binding end 4 of the tubing connector 3. The fibers 23 are guided between the fiber-reception grooves 7 of the binding end 4 and guided into the trenches 71 so that they may be wound around the binding end 4 of the tubing connector 3 with a minimized risk of slipping. This ensures a tight fit between the outer wall 2 of the sheath and the tubing connector 3. As shown in the cross-sectional view of FIG. 6, the female coupling end 5 of the tubing connector 3 comprises a flared inner surface 52. Again, a male coupling end 6 may also be utilized in embodiments of the tubing connector 3.

[0099] Referring to FIG. 7, an isometric view of another tubing connector according to another embodiment of the present invention is shown. Referring to FIG. 8, a longitudinal cross-sectional view of the tubing connector of FIG. 7 according to an embodiment of the present invention is shown. As shown in the embodiment of FIG. 7, the tubing connector 3 comprises a binding end 4 and a female coupling end 5. The binding end 4 comprises a plurality of fiber-deflection units 7, disposed on three wall sections between the four circumferential trenches 71. In the shown embodiment, the fiber-deflection units 7 are substantially cylindrical projections which protrude from the surface of the tubing connector 3. These projections may e.g. be welded onto the surface of the tubing connector 3. In other embodiments, these projections may be milled into the original surface of the tubing connector 3. Again, the fibers 23 of the outer wall 2 of the sheath 2 may be provide between the fiber-deflecting units 7 and guided into the trenches 71 disposed in the surface of the tubing connector 3. As a result, the fibers 23 may be prevented from slipping away, allowing for a limited depth of the trenches 71, while maintaining a strong connection between the binding end 4 of the tubing connector 3 and the outer wall 2 of the sheath 20. As a result, a tubing segment 10 having a high structural integrity is formed, while keeping material costs low and acceding to operational performance requirements. FIG. 8 shows how the substantially cylindrical projections 7 protrude from the surface of the binding end 4 of the tubing connector 3.

[0100] In reference to the previous embodiments of the tubing connector 3, it shall be understood that various combinations and adaptations are applicable. For example, it may be advantageous to combine the substantially triangular fiber-deflection units with the substantially cylindrical projections. In other embodiments, the trench(es) 71 may be entirely omitted, if the fiber-deflection units 7 provide sufficient guidance to the fibers 23 of the outer wall 2 of the sheath 20.

[0101] Referring to FIG. 9 a cut-out view of a tubing connector 3 connected to the tubing segment 10 according to an embodiment of the present invention is shown. The figure shows the tubing segment 10 comprising a sheath 20 having an inner liner 1, an outer wall 2 and a first open end 21. The tubing segment 10 further comprises a tubing connector 3. The tubing connector 3 is connected to the first open end 21 of the sheath 20. In a preferred embodiment, the tubing connector 3 is welded to the inner liner 1 of the sheath 20. The tubing connector comprises a binding end 4 and a female coupling end 5. As can be seen, the binding end 4 of the tubing connector 3 comprises a plurality of fiber-deflection units 7 in the form of projections or pins, which extend radially outward, and are provided across the binding end 4 of the tubing connector 3. These projections 7 are arranged to receive the fibers 23 of the outer wall 2 of the sheath 20 of the tubing segment 10. These fibers 23 extend between the projections 7 of the tubing connector 3, thereby creating an integral connection between the sheath and the tubing connector 3 to form the tubing segment 10. As explained, in a preferred embodiment, both the inner liner 1 and the tubing connector 3 are made of titanium. The titanium inner liner 1 and the titanium tubing connector 3 may be welded together since they are both titanium. However, this must be done in a oxygen-low environment, preferably in an argon-environment. Since the tubing segments 10 are manufactured in a normal production facility, i.e., not at the well site or on the vessel prior to deployment, the environments may be easier controlled, thereby allowing for the use of welded titanium. By using titanium, the corrosion regularly found in steel tubing segments is reduced, the diameter may be reduced because of the lower modulus of elasticity, and the inner liner 1 and the tubing connector 3 may be welded together, increasing the strength of the connection and thus the structural integrity of the tubing segment 10.

[0102] Referring to FIG. 10, a front view of the tubing connector 3, connected to the inner liner 1 of the sheath 20 of the tubing segment 10, according to an embodiment of the present invention is shown. The figure shows a tubing connector 3 having a binding end 4 and a female coupling end 5. The inner liner 1 is connected to the tubing connector 3, preferably via welding. On the tubing connector 3, a number of projections 7 are disposed, between which the fibers 23 of the outer wall 2 may be guided. As shown in the figure, one such fiber 21 is directed over the inner liner 1 of the tubing segment 10 between the projections 7. The projections 7 allow for a gradual directional change of the fiber 21 to ensure the fiber does not encounter disadvantageous amounts of local stress.

[0103] Different layers of fibers 23 may be wound around the inner liner 1 of the binding end 4 of the tubing segment 10 at different winding angles relative to a central sheath axis. The low angle fibers 23 are mainly responsible for carrying the axial loads and providing the connection to the tubing connector 3. Therefore, particular attention must be given to the winding pattern of the low angle fibers 23 when transitioning to the tubing connector 3 and to the path they follow between the projections 7. To provide a smooth and distributed transfer of axial loads from the fibers 23 to the tubing connector 3, a gradual change of fiber direction is desired. This translates into so called wide turns, e.g. turns with a large radius. This is shown in FIG. 10. An even distribution of loads onto the projections 7 is also achieved by ensuring that the turns of each new low angle fiber 21 is placed at a different location along the tubing connector 3 than the previous one. The high angle fibers, provided in the outer wall 2 are mainly responsible for carrying the circumferential loads i.e. pressure and collapse loads. When transitioning onto the tubing connector 3, these high angle fibers maintain their path and angle. This method will sandwich the low angle fibers 23 into a stable laminate, thereby increasing the integrity and stability of the low angle fibers 23. This approach may equally be used in conjunction with other example embodiments of the tubing connectors 3 described herein.

[0104] The transition of fibers from the inner liner 1 onto the tubing connector 3 may be a weak point of the tubing segment 10. To design a fiber transition that is as strong or stronger than the tubing itself, additional local fibers may be added. This leads to the creation of a tubing connection upset, e.g. the increased thickness of the outer wall 2, closer to the tubing connector 3. The maximum outer diameter of the pipe body as well as the maximum outer diameter of the tubing connector 3 may be determined by industry standards, such as for example the maximum inner diameter of the BOP rams, and/or the production casing in downhole applications. Additional local fibers may be added to increase the strength at the transition point while not exceeding the maximum connection upset diameter.

[0105] Referring to FIG. 11, a cross-sectional view of one side of tubing according to an embodiment of the present invention is shown, showing a female coupling end 5 and a male coupling end 6 being connected. As shown in the figure, both the flared inner surface 52 of the female coupling end 5 and the tapered outer surface 52 of the male coupling end 6 comprise attachment members 8. In the shown embodiment, the attachment members 8 are circumferential grooves. The female coupling end 5 of the tubing connector 3 comprises a passage 51 arranged to allow the injection of pressurized fluid between the female coupling end 5 and the male coupling end 6. The passage allows for a fluid connection between the outer surface of the female coupling end 5 and the flared inner surface 52 of the female coupling end 5. As a result, a pressure may be applied between the flared inner surface 52 of the female coupling end 5 and the tapered outer surface 62 of the male coupling end 6, thereby forcing the surfaces, and thus their attachment members 8 apart, so that they may be aligned. Once they are aligned, in an axial direction, the pressure may be released via passage 51 so that the attachment members 8 of the flared inner surface 52 and the tapered outer surface 62 may interlock.

[0106] Referring to FIG. 12, a flow chart illustrating a method of manufacturing a tubing segment 10 in accordance with an embodiment of the present invention is shown. The figure shows the steps of providing an inner liner 1; connecting a tubing connector 3 to the inner liner 1; winding a fibrous material 23 around the inner liner 1 and at least a part of the tubing connector 3; and providing a polymer material to the fibrous material. This forms the outer wall 2 having an integral connection with the tubing connector 3.

[0107] Referring to FIG. 13, a flow chart illustrating a method of coupling two tubing segments 10 in accordance with an embodiment of the present invention is shown. The figure shows the steps of providing a first tubing segment 10 having a male coupling end 6; providing a second tubing segment 10 having a female coupling end 5; positioning the male coupling end 6 in line with the female coupling end 6; partially sliding the tapered outer surface 62 of the male coupling end 6 into the flared inner surface 52 of the female coupling end 5; and securing the attachment members 8 of the tapered outer surface 62 and the flared inner surface 52.

[0108] The invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.

[0109] Further modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.