GB2433079A

GB2433079A - A method of cleaning a liner top.

Info

Publication number: GB2433079A
Application number: GB0623216A
Authority: GB
Inventors: George Telfer
Original assignee: Specialised Petroleum Services Group Ltd; Specialised Petroleum Services Ltd
Current assignee: Schlumberger UK Holdings Ltd
Priority date: 2003-03-25
Filing date: 2004-03-19
Publication date: 2007-06-13
Anticipated expiration: 2024-03-19
Also published as: GB2433079B; GB0623216D0

Abstract

A method of cleaning a liner top 72, the method comprising the steps; inserting a cleaning tool 10 into a liner; running the tool and liner 66 together into a well bore; setting the liner at a casing in the well bore; rotating and/or reciprocating the tool to clean an inner surface of a PBR on the liner with cleaning elements 24a thereon; pulling the tool from the PBR, so that cleaning elements 24a move outwardly by means such as leaf spring 40 to contact neighbouring casing 68 and the liner top 72; and rotating and/or reciprocating the tool to clean an inner surface of the neighbouring casing 68 with the cleaning elements 24. A surface 54 on the cleaning element 24 includes a mill 80 which, when it contacts the top 72 of the PBR 66, can dress the top, acting as a top dress mill when the string is rotated.

Description

1 DUAL FTCT ION CLEANING TOOL 3 The present invention relates to

downhole cleaning tools 4 for use in oil and gas wells and in particular, though not exclusively, to a dual function cleaning tool adapted 6 for cleaning a polished bore receptacle (PBR) and 7 neighbouring casing on the same trip as setting a liner 8 including the PBR.

When a liner is cemented into casing located in a well 11 bore, the PBR located at the top of the liner together 12 with that part of the casing immediately above the PBR 13 (herein referred to as the neighbouring casing) are 14 susceptible to the influx of. cement due to over displacement when the cement is pumped through the drill 16 string and liner setting tool. Further when the drill 17 string and setting tool are removed from the liner, 18 cement and other debris located between the drill string 19 and casing will fall back into the PBR and adhere to the neighbouring casing.

22 As the next stage requires the insertion of a sealing 23 assembly into the liner, the PBR requires to have a 1 smooth cylindrical inner bore on which an effective seal 2 can be made. Additionally, the inner bore of the 3 neighbouring casing is used to seal against a packer if a 4 liner top packer is inserted, and thus requires to provide a smooth uniform cylindrical surface just above 6 the PBR.

8 Consequently the presence of cement and debris at the PBR 9 and/or the neighbouring casing provides a major problem in ensuring a successful seal. In order to overcome this 1]. problem, cleaning tools are typically run into the well 12 bore to clean the PBR. and the neighbouring casing. A trip 13 is typically made to clean the PBR and a second trip is 14 typically needed to clean the casing. Each trip into a well bore is both costly and time consuming.

17 Due to the decrease in inner bore diameter from the 18 casing to the PBR, a single trip cannot be made into the 19 well with a cleaning tool of a fixed diameter to clean both the PBR. and casing. Cleaning tools with cleaning 21 elements which are biased radially outwards such as that 22 disclosed in US 4,189,000 to Best, are inappropriate as 23 the elements cannot be retracted at the point of entry to 24 the PBR. Thus these tools can only clean the casing.

Additionally as the cleaning elements are not located at 26 the ends of the widest diameter of the tool, the cleaning 27 elements cannot effectively access the neighbouring 28 casing due to its close proximity to the narrower PBR.

It is therefore an object of the present invention to 3]. provide a cleaning tool which can provide the dual 32 function of cleaning both the PER and neighbouring casing 33 on the same trip into a well bore.

2 It is a further object of at least one embodiment of the 3 present invention to provide a cleaning tool which can 4 provide the dual function of cleaning both the PBR and neighbouring casing, on the same trip as the liner is set, 6 and/or a packer is set.

S It is a further object of at least one embodiment of the 9 present invention to provide a cleaning tool which can effectively clean the inner bore of a PBR without 11 damaging its relatively delicate inner surface while 12 being able to effectively scrape the harder wearing inner 13 surface of the neighbouring casing to effectively clean 14 this also.

16 It is a yet further object of at least one embodiment of 17 the present invention to provide a cleaning tool which 18 can dress the top of the PER while also cleaning both the 19 PER and the neighbouring casing on a single trip.

21 It is a yet further object of the present invention to 22 provide a method of cementing a liner which includes the 23 step of cleaning the PBR and neighbouring casing on 24 tripping out the liner setting tool.

26 According to a first aspect of the present invention 27 there is provided a cleaning tool for use on a work 28 string, the tool comprising a cylindrical body having an 29 axial bore running there through, a plurality of cleaning elements mounted thereon arid positioning means to move 31 the cleaning elements in relation to the body, and 32 wherein the elements are located eccentrically to the 33 axial bore. 3.

2 Preferably the cleaning elements are scrapers. Preferably 3 also each element has an inner face and an outer face.

4 The outer face may include one or more blades as scrapers. More preferably the cleaning element is 6 substantially rectangular in cross-section to provide a 7 first edge between a side and the outer face.

9 Preferably the plurality of elements are located in at least one band around the circumference of the body.

13. Preferably also the elements of each band are spaced 12 equidistantly around the body.

14 Preferably each element is located in a recess of the body. Preferably each recess is located longitudinally 16 on the body, eccentrically to the axial bore. Preferably 17 also each recess has a lip located at each longitudinal 18 end thereof. The lip will prevent the cleaning element 19 moving out of the recess.

21 Preferably the positioning means is a biasing means 22 located between an inner surface of the recess and the 23 inner face of the cleaning element. More preferably the 24 biasing means is a spring. The spring may be leaf, coiled or conical as are known in the art. Preferably the spring 26 is held in compression, biasing the element away from the 27 body.

29 Preferably the outer face is curved. More preferably the curvature of the outer face is greater than a curvature 31 of the cylindrical body.

1 Preferably the curvature of the outer faces of the 2 elements are selected such that in a first position 3 wherein the outer faces are proud of the body, the outer 4 faces define a cylindrical surface centralised to the adal bore. Preferably also in a second position wherein 6 the outer faces are located outwardly of the first 7 position, the first edge of each element provides a 8 leading edge of a scraper.

Preferably the outer face comprises a material being 11 softer or more malleable than the material of a PBR. In 12 this way the PER cannot be damaged during scraping. The 13 material of the outer face may be brass.

Preferably also the elements include a profiled end. The 16 profiled end may be tapered. In this way, they allow a 17 sleeve, such as a PBR, to move the elements inwards 18 towards the body if the tool is inserted into a PBR.

19 Alternatively, the profiled end may provide a stop. In this way, the stop which may be a shoulder, prevents 21 movement of the tool into a PER whose top overlaps the 22 stop.

24 Preferably the stop comprises a ledge facing the PBR.

Advantageously the ledge comprises a mill. In this way a 26 topdress mill is provided for the PER.

28 According to a second aspect to the present invention 29 there is provided a method of cleaning a liner top, the method comprising the steps; 32 (a) inserting a tool according to the first aspect into 33 a liner; 1 (b) running the tool and liner together into a well 2 bore; 3 (c) setting the liner at a casing in the well bore; 4 (d) rotating andlor reciprocating the tool to clean an S inner surface of a PER on the liner with the 6 cleaning elements; 7 (e) pulling the tool from the PBR, so that the cleaning 8 elements move outwardly to contact neighbouring 9 casing at the liner top; and (f) rotating andJor reciprocating the tool to clean an 11 inner surface of the neighbouring casing with the 12 leading edges of the cleaning elements.

14 This is achieved on a single trip into the well bore.

16 The method may include the further step of tripping the 17 tool from the well bore.

19 The method may include the step of attaching the tool to a liner setting tool, so that the tool is tripped out 21 with the setting tool. In this way the casing is cleaned 22 as the setting tool is tripped from the well.

24 Preferably the method further includes the step of selecting the curvature of the outer faces to be no 26 greater than the curvature of the inner surface of the 27 PER. In this way, at the first position, the curvature of 28 the outer faces substantially match the curvature of the 29 inner surface of the PER.

31 Preferably also the method may include the step of 32 running the tool back into the PER.

1 Preferably the method may include the step of dressing a 2 top of the PER.

4 Preferably the method may include the step of setting down weight on the tool to thereby set a packer.

7 An embodiment of the present invention will now be 8 described, by way of example only, with reference to the 9 accompanying drawings of which: 11 Figure 1 is a part cross-sectional schematic view through 12 a cleaning tool according to an embodiment of the present 13 invention; Figure 2 is a cross-sectional schematic view through the 16 tool of Figure 1 at section AA; and 18 Figure 3 is an illustration of a tool according to an 19 embodiment of the present invention at a PER.

21 Reference is initially made to Figure 1 of the drawings 22 which illustrates a cleaning tool,. generally indicated by 23 reference numeral 10, according to an embodiment of the 24 present invention. Tool 10 comprises a cylindrical body 12 having an axial bore 14. At an upper end 16 of the 26 tool 10 is located a box section 18 for connection of the 27 tool 10 to a work string or a liner setting tool (not 28 shown). At a lower end 20 of the tool 10 is located a pin 29 section 22 for connection of the tool 10 onto a lower section of work string or drill string (not shown).

32 Three cleaning elements 24 are arranged equidistantly 33 around the body 12. Each element 24 is located in a 1 recess 26. Each recess 26 is rectangular and arranged on 2 the body 12 to be eccentric with the centre 28 of the 3 bore 14. This is best seen with the aid of Figure 2. Each 4 recess 26 is offset from a radius drawn from the centre 28. Thus a back surface 38 of the recess 26 is not 6 perpendicular to a radius drawn from the centre 28, 7 through the centre of the surface 38, and to the surface 8 44 of the body 12.

Each element 24 is generally rectangular in cross-section 11 and includes inner face 30, an outer face 32, and 12 longitudinal sides 34,36 respectively. Between the inner 13 face 30 and the back surface 38 of the recess 26 is 14 located a linear expander in the form of a leaf spring 40. Spring 40 is attached to the element 24 by a screw 16 42. The spring 40 is held in compression and thus biases 17 the element 24 away from the back surface 38 of the 18 recess 26. In this way the front face 32 of the element 19 24 protrudes from the outer surface 44 of the body 12.

21 At each longitudinal end 46a,b of the recess 26 is 22 located a lip 48a,b. Lip 48a,b comprises a ring 50a,b 23 threaded onto the body 12. Ring 50a,b is held in position 24 by a lock wire 52a,b as is known in the art. Thus when the tool is rotated the rings 50a,b and hence the lips 26 48a,b remain in position over the ends 46a,b of the 27 recesses. The lips 46a,b limit the movement of the 28 elements 24 away from the back surfaces 38 of the 29 recesses 26. By this limitation on movement, the springs 40 are always held in compression.

32 The outer face 32 of each element 24 comprises three 33 sections 54,56,58. Outer sections 54,56 taper towards the 9.

1 surface 44 of the body 12 from an inner raised section 2 56. Inner section 56 is a scraper. The surface of section 3 56 comprises a blade, but alternatively could comprise a 4 milling surface. The element 24 is made of brass.

Alternatively only the middle section 56 could be made of 6 brass, mounted on a base plate comprising the other - 7 sections 54,58 and the inner face 30. The outer face 32 8 is curved in the plane perpendicular to the axial bore 9 14. The curvature of the outer face does not match the curvature of the surface 44 of the body 12 and is 11 unbalanced on the face 32. In this way a leading edge 60 12 is formed between the outer face 32 and a side 34 of the 13 element 24.

As can be seen with the aid of Figure 2, when the 16 elements 24b,c sit proud of the surface 44 of the body 12 17 at a first position, each outer face 32 lies on a circle 18 62 having a centre, at the centre 28 of the bore 14. As 19 is illustrated by the element 24a, in Figure 2, once the face 32 is in any other position except the first, the 21 leading edge is presented as the point furthest from the 22 body 12. - 24 In use, tool 10 is preferably attached to a liner setting tool (not shown). The tool 10 is mounted ahead of the 26 setting tool on a drill string. The curvature of the 27 faces 32 are selected to be no greater than the curvature 28 of the inner surface 64 of the PBR 66 intended to be 29 cleaned. Ideally, as shown in Figure 2, surface 64 matches the circle 62 defined by the faces 32.

32 The tool 10 is inserted in the PER 66 of the liner to be 33 set in casing 68. The tapered section 58, of the elements 1 24 allow the elements 24 to compress into the recesses 2 26. The tool 10 can then slide into the PER 66 and be 3 held in place by the faces 32 being biased against the 4 inner surface 64 of the PBR 66. As the faces 32 comprise of brass, which is a softer material than the steel 6 typically used for the PER 66, the elements 24 will not 7 damage the smooth surface 64 of the PBR 66. With the tool 8 10 located in the PER 66, the liner is run in the well 9 and. set using the setting tool as is known in the art.

Cement can be pumped through the bore 14 during the 11 cementing process to set the liner.

13 Once the liner is set, the work string is rotated and or 14 reciprocated to allow the faces 32 to clean the inner surface 64 of the PBR 66 to remove any debris or cement 16 which may have accumulated. As the faces 32 are of a 17 softer material than the material of the PBR 66 and the 18 curvatures are similar, the leading edges 60 sweep over 19 the surface 64 providing a polishing action so that the surface 64 is left smooth.

22 Tool 10 is then withdrawn from the PBR 66 on the work 23 string. As the elements are freed from the PBR 66, they 24 will move away from the body 12 under the action of the springs 40 and the faces 32 will now contact the inner 26 surface 70 of the neighbouring casing 68. As the 27 curvature of the faces 32 does not match the curvature of 28 the inner surface 68, the leading edge 60 will contact 29 the surface 68. Rotation and/or reciprocation of the tool 10 will cause the edge 60 to scrape the surface 68 and 3]. thereby clean any debris or cement which rests thereon.

32 This cleaning action is more aggressive than that used in -11 1 the PBR 66. The casing 68 is thereby cleaned as the tool 2 10 is withdrawn from the well bore.

4 As the elements 24 extend from the body 12, the elements 24 can clean the neighbouring casing close to the PBR.

6 This is particularly useful as liner top packers are 7 generally set within two feet (50 cm) of the top 72 of 8 the PBR 66 and the cleaning action therefore provides a 9 good sealing surface on which to set the packer.

11 Any wear of the leading edge 60 will merely cause it to 12 self-sharpen by virtue of the curvature of the face 32 13 always meeting the side 34 at an edge.

In a further embodiment of the present invention the 16 tapered sections 54,58 can be replaced by faces arranged 17 perpendicular to the axial bore 14. This is as 18 illustrated in Fig-ure 3. Lower surface 54 is now 19 substantially perpendicular to the bore 14 at angle to match the top 72 of the PBR 66. The surface 54 includes 2]. a mill 80 which when it contacts the top 72 of the PBR 66 22 can dress the top, acting as a top dress mill when the 23 string is rotated. The mill 80 is made of a suitable 24 material such as carbide. Further, the tool of this embodiment can be used to provide a stop at the top 72 of 26 the PBR 66. In this way the tool 10 cannot be pushed back 27 inside the PBR 66 and so can be used as a packer actuator 28 sub to set a liner top packer 82, by setting down weight 29 on the string.

31 A principal advantage of the present invention is that it 32 provides tool which can clean both the PBR and 1 particularly, the neighbouring casing, on the same trip 2 as a liner is set.

4 A further advantage of the present invention is that it provides a tool with the dual function of providing a 6 delicate cleaning action on the smooth sealing surface of 7 the PBR and a more aggressive cleaning action on the 8 inner surface of the casing.

Modifications may be made to the invention herein 11 intended without departing from the scope thereof. For 12 example, Though scrapers have been illustrated as the 13 cleaning elements bristles could also be placed on the 14 outer faces. The number of elements could be varied and more rows of elements could be mounted on the tool.

16 Additionally, though movement of the cleaning elements is 17 provided by a spring, other means such as using hydraulic 18 pressure against the inner face 30 could be used to move 19 the cleaning elements outwards from the tool body.

Claims

CLAIMS

1. A method of cleaning a liner top, the method comprising the steps; (a) inserting a cleaning tool into a liner; (b) running the tool and liner together into a well bore; (C) setting the liner at a casing in the well bore; (d) rotating and/or reciprocating the tool to clean an inner surface of a PBR on the liner with cleaning elements thereon; (e) pulling the tool from the PBR, so that the cleaning elements move outwardly to contact neighbouring casing at the liner top; and (f) rotating and/or reciprocating the tool to clean an inner surface of the neighbouring casing with the leading edges of the cleaning elements.

2. A method of cleaning a liner top as claimed in Claim 1, wherein the tool comprises a cylindrical body having an axial bore running therethrough, a plurality of eccentrically located cleaning elements mounted thereon, the cleaning, elements having outer faces, the outer faces having a curvature, and, positioning means to move the cleaning elements in relation to the cylindrical body from a first position to a second position, wherein, in the first position, the outer faces of the cleaning elements define a cylindrical surface centralised to the axial bore so that the elements provide a polishing action, and, in the second position, the outer faces present leading edges providing a scraping action.

3. A method of cleaning a liner top as claimed in either of Claims 1 or 2, wherein the method includes the further step of tripping the tool from the well bore.

4. A method of cleaning a liner top as claimed in any preceding Claim, wherein the method includes the step of attaching the tool to a liner setting tool, so that the tool is tripped out with the setting tool.

5. A method of cleaning a liner top as claimed in any preceding Claim, wherein the method further includes the step of selecting the curvature of the outer faces to be no greater than the curvature of the inner surface of the PBR.

6. A method of cleaning a liner top as claimed in any preceding Claim, wherein the method includes the step of running the tool back into the PER.

7. A method of cleaning a liner top as claimed in any preceding Claim, wherein the method includes the step of dressing a top of the PBR.

8. A method of cleaning a liner top as claimed in any preceding Claim, wherein the method includes the step of setting down weight on the tool to thereby set a packer.

9. A method of cleaning a liner top substantially as described herein with reference to and as shown in Figures 1 and
2.

10. A method of cleaning a liner top substantially as described herein with reference to and as shown in Figure
3.