GB2393984A

GB2393984A - Friction reducing clamp

Info

Publication number: GB2393984A
Application number: GB0323108A
Authority: GB
Inventors: Calum Whitelaw; Kenneth Alexander Murray
Original assignee: WELLTONIC Ltd; Polyoil Ltd
Current assignee: WELLTONIC Ltd; Polyoil Ltd
Priority date: 2002-10-04
Filing date: 2003-10-01
Publication date: 2004-04-14
Anticipated expiration: 2023-10-01
Also published as: GB0323108D0; GB0223035D0; GB2393984B

Abstract

A friction reducing clamp 10, for example a centraliser comprises a cylindrical body formed from two cylindrical pieces 11a, 11b manufactured from a polymer material. The cylindrical pieces 11a, 11b are hinged to one another at hinge slots 19a to form a clamp with a bore 12 to allow a coiled tubing (20, figure 3) to pass through. The friction reducing clamp 10 further comprises a series of external fibs 14 and grooves 15, and the bore 12 is coated with an abrasive coating which allows the friction reducing clamp 10 to grip onto the coiled tubing (20, figure 3). The friction reducing clamp 10 is also provided with a reinforcing members (52b, figure 6) to provide additional support for the friction reducing clamp 10.

Description

GB 2393984 A continuation (74) Agent and/or Address for Service: Kennedys

Patent Agency Limited Floor 5, Queens House, 29 St Vincent Place, GLASGOW, G1 2DT, United Kingdom

1 Improved downhole device and method 3 The present invention relates to the field of downhole

4 devices, and in particular to theuse of coiled tubing in 5 the oil and gas well services sector.

7 Coiled tubing is frequently utilised in oilfields for

8 running downhole tools and equipment into a borehole of a 9 well. Coiled tubing can vary in diameter from around 10 25 mm to 100 mm, enabling the pumping of different fluids 11 into the wellbore. The distance to which the coiled 12 tubing is run can range from around 600 m to 5000 m, 13 depending on a number of factors. These factors include 14 the pipe diameter and the spool size, as well as the 15 component materials of the tubing.

17 Coiled tubing is often used in wells that are deviated 18 from the vertical or indeed horizontal wells. Typically, 19 the borehole may include a horizontal section of the 20 borehole several hundred metres long. In vertical wells 21 sections, the pipe strings may be maintained in tension 22 due to the weight of the string caused by the force of 23 gravity. This assists in the running of the pipe string.

2 However, as the coiled tubing passes down the well it 3 contacts the walls of the outer pipe string, creating 4 drag forces on the coiled tubing and inhibiting the 5 insertion of the tubing into the well. These frictional 6 forces may be overcome by providing a compressive force 7 onto the tubing by a stuffing box located on the rig.

9 The problem of drag is exacerbated as the coiled tubing 10 is run through horizontal sections of the wellbore. In 11 this scenario, the string is more likely to be in a state 12 of compression. The significant frictional forces that 13 are placed on the coiled tubing must be overcome by an 14 increased force from the stuffing box in order to push 15 the coiled tubing further into the well. There may be 16 additional physical obstructions to the running of the 17 pipe string in the well, which may produce drag forces 18 resistive to the progress of the pipe string.

20 As the drag forces on the coiled tubing increase, there 21 is a tendency of the coiled tubing to buckle. This 22 buckling can occur throughout the length of the pipe 23 string, and further increases friction or drag between 24 the coiled tubing and the inner wall of the outer pipe 25 string. Once buckling has occurred in the coiled tubing, 26 the force applied by the stuffing box has a lesser degree 27 of linearity along the coiled tubing, causing further 28 escalation of the drag forces. When the drag has 29 increased beyond a certain magnitude, there is a risk 30 that the coiled tubing will lock up, thereby prohibiting 31 further progress into the well.

1 Attempts have been made in order to reduce the tendency 2 of coiled tubing to buckle. Examples include the 3 introduction of frictionreducing chemicals to the fluids

4 within the wellbore, and the use of specially designed 5 tool technology for reducing friction and vibration at 6 the bottom hole assembly. However, for many applications 7 these methods are impractical or prohibitive.

9 It is one aim of the invention to improve the reach 10 capabilities of coiled tubing.

12 It is a further object of the invention to mitigate at 13 least some of the drawbacks associated with the prior 14 art.

16 Additional aims and objects of the invention will become 17 apparent from a reading of the following description.

19 According to a first aspect of the invention, there is 20 provided a method for use in coiled tubing operations in 21 a wellbore, the method comprising the steps of: 22 - receiving a length of coiled tubing from a storage 23 drum, the coiled tubing having an outer surface and; 24 attaching a friction-reducing clamp around a portion of 25 the coiled tubing, the friction-reducing clamp having a 26 substantially cylindrical body portion, said body 27 portion being made from a polymer material and having 28 an axial bore extending therethrough defining an inner 29 surface of the clamp, such that the inner surface of 30 the clamp contacts the outer surface of the coiled 31 tubing. 33 The method may comprise the additional steps of:

1 - receiving the length of coiled tubing into a coiled 2 tubing injecting means) 3 - injecting the coiled tubing from the coiled tubing 4 injecting means into a wellbore opening.

6 Preferably, the step of attaching the friction-reducing 7 clamp is carried out subsequent to the step of receiving 8 the coiled tubing into the coiled tubing injecting means.

10 The step of attaching the friction-reducing clamp may be 11 carried out by means of a hydraulically actuated work 12 window positioned between the coiled tubing injecting 13 means and the wellbore opening.

15 According to a second aspect of the invention, there is 16 provided an assembly for use in wellbore operations, the 17 assembly comprising: 18 a length of coiled tubing having an outer surface; 19 - a frictionreducing clamp having a substantially 20 cylindrical body portion, said body portion being made 21 from a polymer material and having an axial bore 22 extending therethrough defining an inner surface of the 23 clamp; 24 - wherein the friction-redcing clamp is attached around 25 a portion of the coiled tubing such that the inner 26 surface of the clamp contacts the outer surface of the 27 coiled tubing.

29 According to a third aspect of the invention, there is 30 provided a friction-reducing clamp for attachment to a 31 length of coiled tubing, the friction-reducing clamp 32 comprising:

1 - a substantially cylindrical body portion, said body 2 portion being made from a polymer material and having 3 an axial bore extending therethrough defining an inner 4 surface of the clamp; 5 - wherein the friction-reducing clamp includes means for 6 attaching around a portion of coiled tubing such that 7 the inner surface of the clamp contacts an outer 8 surface of the coiled tubing.

10 The body portion may comprise two generally part 11 cylindrical sections. The part-cylindrical sections may 12 be hingedly connected to one another. There may be two 13 such part-cylindrical sections.

15 The body portion may have a circular outer surface and a 16 circular inner surface. The outer surface may be 17 concentric with the inner surface. Alternatively, the 18 outer surface may be eccentric with the inner surface.

20 The outer surface may be provided with a plurality of 21 ribs protruding radially from the body portion and 22 oriented in an axial direction.

24 The outer surface may be provided with a plurality of 25 grooves. The grooves may be concave and be oriented in 26 an axial direction.

28 At least one end of the body portion may be tapered such 29 that the outer diameter at said end is less than the 30 outer diameter of the main body portion.

32 The inner surface may be provided with an abrasive 33 coating. The abrasive coating may be selected from the

1 following group: tungsten carbide grit, sand, silica, 2 metal oxide particulate, metallic flake, a woven metal 3 cloth.

5 The body portion may be shaped as a cylinder with a 6 circumferential portion removed from the entire axial 7 length of the body portion. Such a body portion may be 8 described as having a "C" shaped cross-sectional profile.

10 The friction-reducing clamp may be provided with at least 11 one reinforcing member. The reinforcing member may be a 12 metal structure. The reinforcing members may be moulded 13 into the friction-reducing clamp.

15 There will now be described, by way of example only, 16 various embodiments of the invention with reference to 17 the following drawings, of which: 19 Figure 1 shows a perspective view of a friction 20 reducing clamp in accordance with an embodiment of 21 the invention; 23 Figure 2 shows a perspective view of the friction 24 reducing clamp of Figure 1 in an open position; 26 Figure 3 shows a perspective view of an assembly in 27 accordance with an embodiment of the invention; 29 Figure 4 shows a perspective view of a friction 30 reducing clamp in accordance-with an alternative 31 embodiment of the invention;

1 Figures 5A and 5B show perspective views of a re 2 enforcement structure for use with a friction 3 reducing clamp according to the invention.

5 Figure 6 shows the reinforcements of Figure 5 in 6 place on the friction-reducing clamp; 8 Figures 7, 8, 9 and 10 show further reinforcements 9 for use with friction-reducing clamps in accordance 10 with embodiments of the invention.

12 Referring firstly to Figure 1, there is shown a friction 13 reducing clamp generally depicted at 10. The clamp is 14 generally cylindrical in shape, and is provided with a 15 bore 12 extending axially through the length of the body 16 portion 11. The body is moulded from a polymer material 17 such as nylon.

19 The outer surface 13 of the body 10 is profiled with ribs 20 14 and grooves 15. The ribs 14 are protrusions that 21 extend radially from the inside of the body portion, and 22 are oriented parallel to the longitudinal axis of the 23 body portion 11. Similarly, the grooves are recessed 29 concave channels oriented parallel to the longitudinal 25 axis of the body portion. The ribs 14 and grooves 15 are 26 approximately equally spaced around the circumference of 27 the body portion 10. In this example, each rib is 28 diametrically opposite another rib.

30 The body portion is provided with a tapered region 16 31 located adjacent each end 17. The outer diameter of the 32 friction-reducing clamp 10 decreases within this tapered 33 region towards the end of the boa: portion. The tapered

1 region provides a smoother contour for obstructions 2 encountered when running the coiled tubing.

4 As clearly shown in Figure 2, the body portion of the 5 frictionreducing clamp is constructed from two part 6 cylindrical pieces lla, lib. The sections lla, llb are 7 hingedly connected along an edge 18. Section llb is 8 provided with two hinge slots 19b for receiving hinge 9 fingers 19a formed on section lla. The hinge slots are 10 axially spaced along the edge 18. A bore 22 is provided 11 through the section llb and through the hinge fingers 19a 12 adjacent the edge 18, and extends along the axial length 13 of the body portion from one tapered region 16 to the 14 opposite tapered region. The aperture 22 receives a 15 hinge pin (not shown) for pivotally connecting the two 16 sections.

18 The opposing edges of the sections lla and llb are 19 provided with means for aligning and fastening the part 20 cylindrical sections around a length of coiled tubing.

21 Section lla is provided with alignment blocks 23a and 22 section llb has a corresponding alignment slot 23b.

23 Bores 24 extend through the alignment block 23a and 24 adjacent edge of the alignment slot 23b to enable 25 fastening bolts to extend therethrough, securing the 26 clamp in place on the coiled tubing. Channels 25 are 27 provided in alignment with the bores 24 in order to allow 28 bolts to be inserted into the bores.

30 Figure 3 shows the friction-reducing clamp being 31 positioned around the coiled tubing 20. The clamp is 32 quickly and easily attached around the coiled tubing, and 33 secured by means of bolts as described above, or by

1 alternative fasteners. The fasteners are chosen so that 2 the clamps can easily be removed from the coiled tubing 3 at the surface.

5 The central bore 12 defines an inner surface of the 6 clamp. The internal diameter of the clamp is chosen 7 specifically for the diameter of coiled tubing in use.

8 It is advantageous to have a tight, continuous contact 9 between the clamp and the coiled tubing.

11 To improve grip and reduce any tendency to slip, the 12 inner surface of the polymer clamp may be provided with 13 an abrasive coating. Examples of suitable coatings 14 include tungsten carbide grit, sand, silica, metal oxide 15 particulate, or metallic flake, applied or fixed to the 16 inner surface. Alternatively, the coating may be a woven 17 metal cloth or a mesh. Relatively hard and sharp 18 metallic or tungsten insets could be embedded in the 19 surface to aid grip further.

21 In addition, or as an alternative to the abrasive 22 coating, the clamps may be run with a pair of hinged stop 23 collars, placed on the coiled tubing above and below the 24 clamp.

26 In certain applications, it may be desirable to reinforce 27 the friction-reducing clamps of the above-described 28 embodiment in order to offer a structure which gives 29 greater tightening force and/or greater strength to the 30 clamp. Figures 5 to 10 give examples of various 31 structures which can be used to achieve this.

1 Figures 5A, 5B and 6 show a pair of reinforcing members 2 50a, 50b used in an embodiment of the invention. The 3 reinforcing members each comprise substantially semi 4 circular parts 52a, 52b, and fixing tabs 51a, 51b. The 5 reinforcing members are incorporated into the sections 6 lla, lib, and the manner in which they are arranged is 7 more clearly shown in Figure 6.

9 The reinforcing members 50a, 50b are positioned around 10 the bore 12. The fixing plates 51a, 51b are placed in an 11 abutting relationship such that the threaded shaft 58 of 12 plate 51b extends through a corresponding aperture on 13 plate 51a. The reinforcing members are positioned such 14 that the threaded shaft 58 is aligned with the bore 24, 15 such that a fastening bolt (for fastening the two body 16 sections together) may be received into the threaded 17 shaft 58. The fixing plate therefore provides structural 18 support to the fastening area.

20 At the opposing end of the reinforcing member 50a is a 21 single hook formation 55. This hook is located within 22 the hinge finger of body section lla, and partially 23 surrounds the aperture 22. Reinforcing member 50b is 24 provided with a double hook formation 57. The hooks 57 25 are positioned within the body section llb adjacent and 26 either side of the hinge slot l9b, such that they also 27 partially surround the aperture 22. As shown in Figure 28 6, the hinge pin 61 extends through the aperture 22 and 29 through the surrounding hooks 55, 57. The hooks provide 30 structural support to the hinge area.

1 The additional holes 54 are optional, and would improve 2 the material flow during moulding if necessary and 3 provide additional integral strength when required.

5 In an alternative arrangement, the above reinforcing 6 members could be formed to more closely follow the outer 7 profile of the polymer body portion of the clamp.

9 Figure 7 shows a reinforcing strip 70 that could be 10 incorporated within the body portion. One or more of 11 such strips could be oriented in an axial direction of 12 the clamp in order to improve the axial compressive 13 strength of the device. Once again, optional holes 54 14 are provided to improve material flow during 15 manufacturing.

17 Figure 8 shows a smaller reinforcement section 80 that 18 could be incorporated in or around the alignment blocks 19 23a and alignment slots 23b. Such a reinforcement 20 section could be used to reinforce and distribute loads 21 around the fastening area. This particular example shows 22 a threaded shaft 82 pre-assembled and welded to the 23 plate, functioning to receive a threaded fastening bolt.

24 Again pre-drilled or punched holes 54 would be optional.

26 Figure 9 shows a structure similar to that of Figure 8.

27 However, in this example the plate 91 extends along a 28 greater length. Two threaded shafts 92 are provided in 29 order to receive two fastening bolts. This structure has 30 the advantage that loads are distributed over a larger 31 area.

1 Figure 10 illustrates a reinforcing cage 100. The cage 2 is provided with windows 102 through which the ribs of 3 the body portion may extend.

5 It will be evident that various modifications could be 6 made to the reinforcing structures described with 7 reference to Figures 5 to 10. For example, the members 8 50a, 50b of Figure 5 could be pre-assembled with the 9 structures shown in Figures 7 to 10 by clips, fasteners 10 or by welding. Other combinations are also possible.

12 Figure 4 shows a friction-reducing clamp in accordance 13 with an alternative embodiment of the invention. In this 14 example, four ribs 14 are provided, each giving 15 substantial stand-off for the coiled tubing. Elements 16 similar to those in the example of Figures 1 to 4 are 17 numbered similarly.

19 Further modifications may be made to the above-described 20 embodiments within the scope of the invention. For 21 example, the body portion of the friction-reducing clamps 22 may be constructed from three or more part-cylindrical 23 body sections. These sections may be connected by 24 hinges, or may be connected by other means, such as snap 25 fastenings.

27 Alternatively, the body portion of the clamp could be a 28 single partcylindrical moulding, with an axially 29 extending portion being removed. Such a body portion has 30 may be described as having a "C" shaped crosssectional 31 profile along its entire length. If the polymer from 32 which the body portion is moulded is sufficiently 33 compliant and resilient, the clamp could be stretched to

1 increase the width of the axial slot, thereby allowing 2 the clamp to snap over the coiled tubing.

4 In a method according to an embodiment of the invention, 5 the frictionreducing clamps are attached to the coiled 6 tubing as it is being run into the well, at the level of 7 the rig floor. A hydraulic actuated work window is used 8 to access the coiled tubing and fasten the clamps onto 9 the tubing. The application of the clamps takes place 10 immediately below the stuffing box. Trained personnel 11 are able to attach and remove these clamps in a safe and 12 time-efficient manner. The placement and number of 13 clamps required is predicted by a computer simulation.

15 The method is also applicable to jointed pipe run from a 16 hydraulic work-over unit, for example small diameter 17 jointed tubulars used in similar well intervention 18 applications.

20 The downhole device in accordance with the invention 21 offers several advantages over the prior art systems. It

22 has been recognised that that the use of polymer 23 centralisers and cable clamps has been successfully 24 demonstrated to reduce the effective friction and 25 buckling tendency for other types of tubular 26 operations/deployment such as for casing, tubing, liner 27 and wellscreen. The present invention applies similar 28 principles to the specialised field of coiled tubing

29 operations. It has been realised that the application of 30 frictionreducing clamps to coiled tubing significantly 31 increases the reach of the coiled tubing within the well.

32 Increased centralisation/stand-off will help to increase

1 the effective outer diameter and reduce the buckling 2 tendency of the coiled tubing being run.

4 Another possible advantage is apparent when advanced 5 tools are attached to the end of the coil. Interest in 6 non-metallic components has increased with the prospect 7 of "smart" or "intelligent well" designs, which may in 8 the future use the production tubular as an electrical or 9 signal conductor. The electrical insulating properties 10 of a non-metallic friction-reducing clamp allow the 11 passage of electrical currents, and pulsed electrical or 12 radio signals. This would enable downhole tool power 13 supply, or signals to operate downhole equipment such as 14 valves or other downhole flow controlling devices.

15 Similarly, any downhole gauges or well monitoring 16 equipment can use either the casing wellbore or the 17 producing tubular within for information transmission to 18 the surface.

Claims

1 Claims

3 1. A method for use in coiled tubing operations in a 4 wellbore, the method comprising the steps of: 5 - receiving a length of coiled tubing from a storage 6 drum; 7 - attaching a friction-reducing clamp around a 8 portion of the coiled tubing.

10

2. The method as claimed in Claim 1 comprising the 11 additional steps of: 12 - receiving the length of coiled tubing into a 13 coiled tubing injecting means; 14 - injecting the coiled tubing from the coiled tubing 15 injecting means into a wellbore opening.

17

3. The method as claimed in Claim 2 wherein the step of 18 attaching the friction-reducing clamp is carried out 19 subsequent to the step,of receiving the coiled 20 tubing into the coiled tubing injecting means.

22

4. The method as claimed in Claim 2 or Claim 3 wherein 23 the step of attaching the friction-reducing clamp is 24 carried out by means of a hydraulically actuated 25 work window positioned between the coiled tubing 26 injecting means and the wellbore opening.

28

5. The method as claimed in any preceding claim wherein 29 the friction-reducing clamp has a substantially 30 cylindrical body portion, said body portion being 31 made from a polymer material and having an axial 32 bore extending therethrough defining an inner

1 surface of the clamp, such that the inner surface of 2 the clamp contacts the outer surface of the coiled 3 tubing. 5

6. A frictionreducing clamp for attachment to a length 6 of coiled tubing, the friction-reducing clamp 7 comprising a body portion, and means for attaching 8 the clamp around a portion of coiled tubing.

10

7. The friction-reducing clamp as claimed in Claim 6 11 wherein the body portion is substantially 12 cylindrical and has an axial bore extending 13 therethrough defining an inner surface of the clamp, 14 and the clamp is adapted to be attached around a 15 portion of coiled tubing such that the inner surface 16 of the clamp contacts an outer surface of the coiled 17 tubing. 19

8. The friction-reducing clamp as claimed in Claim 6 or 20 Claim 7 wherein the body portion is made from a 21 polymer material.

23

9. The friction-reducing clamp as claimed in any of 24 Claims 6 to 8 wherein the body portion comprises two 25 generally part-cylindrical sections.

27

10. The friction-reducing clamp as claimed in Claim 9 28 wherein the generally part-cylindrical sections are 29 hingedly connected to one another.

31

11. The friction-reducing clamp as claimed in any of 32 Claims 6 to 10 wherein the body portion has a 33 circular outer surface and a circular inner surface.

2

12. The friction-reducing clamp as claimed in any of 3 Claims 6 to 11 wherein the outer surface is 4 concentric with the inner surface.

6

13. The friction-reducing clamp as claimed in any of 7 Claims 6 to 11 wherein the outer surface is 8 eccentric with the inner surface.

10

14. The friction-reducing clamp as claimed in any of 11 Claims 6 to 13 wherein the outer surface is provided 12 with a plurality of ribs protruding radially from 13 the body portion and oriented in an axial direction.

15

15. The friction-reducing clamp as claimed in any of 16 Claims 6 to 14 wherein the outer surface is provided 17 with a plurality of grooves.

19

16. The friction-reducing clamp as claimed in Claim 15 20 grooves are concave and oriented in an axial 21 direction.

23

17. The friction-reducing clamp as claimed in any of 24 Claims 6 to 16 wherein at least one end of the body 25 portion is tapered such that the outer diameter at 26 said end is less than the outer diameter of the main 27 body portion.

29

18. The friction-reducing clamp as claimed in any of 30 Claims 6 to 17 wherein the inner surface is provided 31 with an abrasive coating.

1

19. The friction-reducing clamp as claimed in Claim 18 2 wherein the abrasive coating may be selected from 3 the following group: tungsten carbide grit, sand, 4 silica, metal oxide particulate, metallic flake, a 5 woven metal cloth.

7

20. The friction-reducing clamp as claimed in any of 8 Claims 6 to 19 wherein the body portion is shaped as 9 a cylinder with a circumferential portion removed 10 from the extent of the axial length of the body 11 portion. 13

21. The friction-reducing clamp as claimed in any of 14 Claims 6 to 20 wherein the friction-reducing clamp 15 is provided with at least one reinforcing member.

16 r 17

22. The friction-reducing clamp as claimed in Claim 21 18 wherein the reinforcing member is a metal structure.

20

23. The friction-reducing clamp as claimed in Claim 21 21 or Claim 22 wherein the reinforcing members are 22 moulded into the friction-reducing clamp.

24

24. An assembly for use in wellbore operations, the 25 assembly comprising a length of coiled tubing, and a 26 friction-reducing clamp according to any of Claims 6 27 to 22 attached to a portion of the coiled tubing.