Downhole cleaning apparatus

Abstract

Disclosed herein is a downhole cleaning apparatus and a method of cleaning a wellbore. The downhole cleaning apparatus has a body and a cleaning element coupled to the body. The cleaning element is selectively moveable in relation to the body from a retracted position to an extended position. When the cleaning element is in the retracted position it is retained by retention formations internal to the tool that are coupled together. The retention formations can be slideably released from one another to enable the cleaning element is able to move to the extended position. The force required to slideable release the retention formations exceeds any forces encountered when the apparatus is run in, preventing premature extension of the cleaning element.

Claims

1. A downhole cleaning apparatus, comprising: a body and a cleaning element coupled to the body; the cleaning element selectively moveable in relation to the body from a retracted position to an extended position; and the cleaning element having an inner portion comprising a first retention formation and an outer portion comprising a cleaning formation; and an actuation system comprising a second retention formation slideable in relation to the body between a retaining position and a release position; wherein, in the retracted position, the first retention formation is coupled to the second retention formation and wherein the first and second formations together function as a latch, to latch the cleaning element in the retracted position; the first and second retention formations being slideably releasable from one another by sliding the second retention formation from the retaining position to the release position, in which the cleaning element is able to move to the extended position.

2. The cleaning apparatus of claim 1, wherein the second retention formation is longitudinally slideable along an axis, wherein such longitudinal motion slideably moves the second retention formation in relation to the first retention formation, between the retaining and release positions.

3. The cleaning apparatus of claim 1, wherein the second retention formation is biased towards the retaining position.

4. The cleaning apparatus of claim 3, wherein the second retention formation is biased towards the retaining position by a resilient biasing arrangement which acts between the body and the second retention formation.

5. The cleaning apparatus of claim 1, wherein one of the first retention formation or the second retention formation comprises a protrusion and the other of the first retention formation or the second retention formation comprises a recess or aperture sized to receive at least a part of the protrusion.

6. The cleaning apparatus of claim 5, wherein the first retention element comprises the protrusion and the second retention formation comprises the recess or aperture.

7. The cleaning apparatus of claim 5, wherein the protrusion is L-shaped in cross section, taken along a direction of motion between the retaining and release positions.

8. The cleaning apparatus of claim 1, further comprising a setting sleeve, the sleeve slideable within the body; the sleeve comprising the second retention formation and being longitudinally slideable in relation to the body.

9. The cleaning apparatus of claim 8, wherein an outer surface of the setting sleeve comprises the second retention formation.

10. The cleaning apparatus of claim 1, wherein the cleaning element is biased towards the extended position.

11. The cleaning apparatus of claim 1, wherein the actuation system further comprises: a ball and/or a dart; and a seat to receive a said ball or dart and thereby at least partially block a through bore through the body to facilitate an increase of internal pressure within the body, the increase in pressure causing the second retention formation to move from the retaining position to the release position.

12. The cleaning apparatus of claim 1, wherein the cleaning formation comprises a cutting profile or a brush operable, in use, by axial reciprocation to remove debris from a surface in which the cleaning elements are in contact.

13. The cleaning apparatus of claim 1, wherein the body is a tubular body defining a longitudinal axis and a plurality of cleaning elements, wherein the plurality of cleaning elements are symmetrically disposed around the longitudinal axis.

14. The cleaning apparatus according to claim 1, wherein the body is a tubular body defining a longitudinal axis and a plurality of cleaning elements, wherein the body comprises an opening corresponding to each cleaning element, wherein the outer portion of each cleaning element is configured to at least partially extend through the openings and to extend outwards from an outer surface of the body, when in their extended positions.

15. The cleaning apparatus of claim 14, comprising a one or more longitudinal or helical flutes, the/each flute being defined between longitudinal or helical ribs, wherein longitudinal or helical paths defined by the cleaning elements run along the ribs.

16. A method of cleaning an inside of a wellbore, comprising the steps of: providing a cleaning apparatus having a body and a cleaning element coupled to the body; the cleaning element having an inner portion comprising a first retention formation and an outer portion comprising a cleaning formation; the cleaning apparatus further comprising an actuation system comprising a second retention formation; wherein the second retention formation is in a retaining position in which the first and second retention formations are coupled together and function as a latch to mechanically latch the cleaning element in a retracted position; running the cleaning apparatus into the wellbore; operating the actuation system to cause the second retention formation to slide from the retaining position to a release position in which the first and second retaining formations are released from one another; then moving the cleaning element from the retracted position to an extended position.

17. The method of claim 16, comprising cleaning the inside of the wellbore using the cleaning element, by moving the cleaning apparatus in relation to the wellbore and flowing fluid through a through bore through the body.

18. The method of claim 16, comprising changing the fluid pressure in the body and one or more of; moving the cleaning elements from the retracted position to the extended position by increasing the fluid pressure; blocking a through bore through the body and increasing pressure so as to move the second retention formation and/or to break a shear pin.

19. A downhole cleaning apparatus, comprising: a body and a cleaning element coupled to the body; the cleaning element selectively moveable in relation to the body from a retracted position to an extended position; and the cleaning element having an inner portion comprising a first retention formation and an outer portion comprising a cleaning formation; and an actuation system comprising a second retention formation slideable in relation to the body between a retaining position and a release position; wherein one of the first retention formation or the second retention formation comprising a protrusion that is L-shaped in cross section, taken along a direction of motion between the retaining and release positions, and the other of the first retention formation or the second retention formation comprises a recess or aperture sized to receive at least a part of the protrusion; wherein, in the retracted position, the first retention formation is coupled to the second retention formation; the first and second retention formations being slideably releasable from one another by sliding the second retention formation from the retaining position to the release position, in which the cleaning element is able to move to the extended position.

20. The cleaning apparatus of claim 19, further comprising: a setting sleeve slideable within the body, wherein the sleeve comprises the second retention formation and is longitudinally slideable in relation to the body.

21. A downhole cleaning apparatus, comprising: a body and a cleaning element coupled to the body; the cleaning element selectively moveable in relation to the body from a retracted position to an extended position; and the cleaning element having an inner portion comprising a first retention formation and an outer portion comprising a cleaning formation; and an actuation system comprising a second retention formation slideable in relation to the body between a retaining position and a release position; wherein, in the retracted position, the first retention formation is coupled to the second retention formation and wherein the first and second formations together function as a latch, to latch the cleaning element in the retracted position; the first and second retention formations being slideably releasable from one another by sliding the second retention formation from the retaining position to the release position, in which the cleaning element is able to move to the extended position, wherein the body is a tubular body defining a longitudinal axis and a plurality of cleaning elements, wherein the body comprises an opening corresponding to each cleaning element, wherein the outer portion of each cleaning element is configured to at least partially extend through the openings and to extend outwards from an outer surface of the body, when in their extended positions, and comprising a one or more longitudinal or helical flutes, having each flute being defined between longitudinal or helical ribs, wherein longitudinal or helical paths defined by the cleaning elements run along the ribs.

Description

DESCRIPTION OF THE DRAWINGS

(1) Non-limiting examples of the invention are described below, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic representation of a downhole cleaning apparatus with cleaning elements in retracted positions;

(3) FIG. 2 is a schematic representation of the downhole cleaning apparatus with the cleaning elements in extended positions;

(4) FIG. 3 is a schematic representation of an axial cross-section of the downhole cleaning apparatus as illustrated in FIG. 1;

(5) FIG. 4 is an expanded, simplified cross sectional view of region B of FIG. 3;

(6) FIG. 5 is a schematic representation of an axial cross section of the downhole cleaning apparatus as illustrated in FIG. 2;

(7) FIG. 6 is an expanded, simplified cross sectional view of region B of FIG. 5;

(8) FIG. 7 is a view of region E of FIG. 6, with the through bore re-opened for fluid flow;

(9) FIG. 8 is a schematic representation of an assembly of a casing cleaner; and

(10) FIG. 9 is an expanded, simplified cross sectional view of region B of an alternative example of a downhole cleaning apparatus (a) with the cleaning element in a retracted position and (b) with the cleaning element in an extended position.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(11) FIGS. 1 and 2, each show a casing cleaner 10 (a downhole cleaning apparatus), which represents a downhole cleaning apparatus. The casing cleaner 10 includes a tubular body 12, which comprises an axial through bore (not visible in FIG. 1 or 2). The casing cleaner 10, in the illustrated embodiment, includes three external ribs 14. Flutes 16 (two of which can be seen in FIGS. 1 and 2) separate the ribs 14 and define zones via which debris dislodged from the casing wall (not illustrated) can be discharged in use.

(12) The ribs 14 and flutes 16 of the illustrated embodiment each define part of a helix 18 which extends end to end on the external surface of the body 12.

(13) Each rib 14 includes slots 20 through which cleaning elements 22 extend. As shown in the cross-sectional views of FIGS. 3 to 6 the cleaning elements 22 coupled to the body 12, to prevent them from being fully expelled from the tubular body 12, by locking pins 38 that are attached to the body and extend into the slots 20 and into a groove 40 provided in the side of each cleaning element 22. The grooves are oriented radially in relation to the longitudinal axis A of the body 12. The range of movement of the cleaning element 22 is thereby limited by the length of the groove 40.

(14) The slots 20 and cleaning elements 22 each define part of the helix 18 defined by the ribs 14 and flutes 16. In the illustrated embodiment each of the helical ribs 14 includes four slots 20 and four cleaning elements 22.

(15) In alternative embodiments (not shown) the casing cleaner may have a different number of flutes or ribs, a longitudinal (rather than helical) array of cleaning elements, or any number of one or more cleaning elements.

(16) In respect of the casing cleaner 10, as illustrated, the circumferential extent of each helix 18 is at least 120 degrees such that, in use, the cleaning elements 22 are operable to be in contact with the entire 360 degree casing surface. The arrangement of the ribs 14 and cleaning elements 22 in the form of a helix means that, in use, the casing cleaner 10 needs only to be operated in a reciprocating manner.

(17) The cleaning elements 22 in the illustrated embodiment have an outer portion (indicated generally as 22a) which includes scraper blades 23 (a cleaning formation). Scraper blades comprise a plurality of cutting edges that act against the casing wall to dislodge debris as the cleaner passes through the casing. Casing scrapers may be constructed from, for example, machined low alloy steel. Alternatively, the blades may be forged. The material choice and construction of the blades is that which demonstrates long lasting durability and excellent scraping characteristics. Alternatively, the cleaning elements may comprise another type of cleaning formation, such as brushes, which can be used to brush and clean the interior surface/circumference of a casing to remove scale, rust, mud residue and other types of debris. The scraper blades and brushes are configured to act in an abrasive manner to clean the casing wall.

(18) The cleaning elements 22 are arranged to be retained in a retracted position (shown in FIG. 1), when the casing cleaning 10 is run in. In the retracted position, the cleaning elements are recessed in relation to the outer surface of the body, to prevent wear of the scraper blades or casing during run in.

(19) The cleaning elements 22 are selectively moveable in relation to the body 12 from the retracted position shown in FIG. 1 to an extended position shown in FIG. 2. In the extended position, the scraper blades extend radially from the outermost surface of the body and so can be used to clean a casing.

(20) As discussed in further detail below, the cleaning elements 22 are biased outwardly by springs 50 positioned at their outer ends in cavities 52 in the inner face of the cleaning elements and at their inner ends in tapered cavities 36 in the outer face of a setting sleeve 32. In alternatively embodiments, the cleaning elements are not biased outwardly, until the springs 50 slide out of the tapered cavities 36 in the manner discussed below.

(21) The tapered cavities are optional and in other embodiments (not shown) the sleeve has a constant outer diameter in the region that interacts with the springs in use.

(22) The casing cleaner 10 can be sized such that the overall maximum diameter across the extended cleaning elements exceeds the diameter of the casing to be cleaned, such that the blades are biased with a biasing force F1 into contact with the inner wall of the casing.

(23) The casing cleaner 10 includes an actuation system, the structure and operation of which is described with reference to FIGS. 3 to 6.

(24) FIG. 3 shows a schematic cross sectional view of the tool 10, with the cleaning elements 22 in their retracted positions (c.f. FIG. 1). The expanded section B of FIG. 4 shows a simplified schematic cross sectional view of the cleaning element and the adjacent parts of the tool 10.

(25) In the illustrated embodiment, the cleaning elements 22 are biased by spring force F1 applied between the sleeve 32 and the cleaning elements 22 radially outwardly towards the extended position. The cleaning elements have an inner portion 22b which includes a first retention formation, in the form of a protrusion 56.

(26) The cleaning elements 22, are held in the retracted position by a protrusion 56 that extends from the inner face 58 of each cleaning element (an example of a first retention formation), that is received within a recess 60 (an example of a second retention formation) in the outer face 62 of a setting sleeve 32 that is positioned with the axial through bore 35 of the tool 10. The first and second retention formations 58, 60 are thus coupled together.

(27) The protrusion 56 is L-shaped in cross section along the axis A, and comprises a radially extending portion 56a and a longitudinally extending portion 56b. The recess has a wide entranceway that extends longitudinally slightly further that the longitudinal extent of the protrusion 56.

(28) A lip 64 extends partially over the recess 60, to define an enclosed region 66. Accordingly, the longitudinally extending portion 56b of the protrusion 56 is received within the enclosed region 64 of the recess, thereby coupling the first and second retaining formations, and is prevented by the lip from being propelled radially outward.

(29) As discussed in further detail below, the setting sleeve 32 is slideable in relation to the body. Thus, the recess 60 is longitudinally slideable in relation to the body the body 12, between the retaining position shown in FIGS. 3 and 4, and the release position shown in FIGS. 5 and 6.

(30) Movement of the second retaining formation, the recess 60, from the retaining position to the release position moves the longitudinal portion 56b clear of the lip 64 and thereby release the first and second retaining formations 56, 60 from one another and allow the cleaning element to move to its extended position.

(31) The first and second retaining formations, the protrusion 56 and the recess 60, form part of an actuation system, operable to selectively move the cleaning element from the retracted position to the extended position. A shear pin 24 acts to restrain the setting sleeve 32 from moving longitudinally within the axial through bore 35.

(32) A ball seat 30 is positioned in the bore 35 at the distal end of the body 12, and connected to the sleeve 32. To selectively more the cleaning elements 22 to the extended positions, the axial bore 35 is sealed by release of a ball 34, that is either pumped down from the surface or allowed to drop freely. The ball 34 comes to rest on the ball seat 30 such that fluid pressure within the axial bore 35 can increase to the predetermined level in which pins 24 shear or break to release the setting sleeve 32 which will begin to move downwards (in the direction D).

(33) The sleeve and thus also the recesses 60 thereby slide to the position shown in FIGS. 5 and 6, in which the longitudinal portion 56b is clear of the lip 64. The first and second retaining formations have thereby been slideably released from one another and the cleaning elements are able to move radially outward to their extended positions under the action of the springs 50.

(34) The retaining formations are located internally to the tool (i.e. the inner portion 22a of the cleaning element 22 and the adjacent parts of the actuation system), and so are not exposed to the wellbore in use.

(35) As the setting sleeve 32 moves in the direction D, the inner ends of the springs 50 slide out of the tapered cavities 36 on to wider diameter portions 37 of the sleeve 32, so as to increase the effectiveness of the springs 50.

(36) In some examples, when the springs sit in the tapered cavities and the cleaning elements are in their retracted positions, the springs are not compressed. In this case, the spring bias is provided as the springs ride up and out of the cavities 36.

(37) In still further examples (not shown) the sleeve may, at least when moved to its most distal position, be rotatable so as to cause the springs to ride up and out of the tapered cavities. In this case longitudinal motion of the sleeve primes the cleaning elements for extension, and rotation causes the extension to occur. Internal fluid pressure in the bore can also be used to extend the cleaning elements in some cases.

(38) In other examples, the body itself is compressible and be formed from two portions. The the sleeve may abut or be connected to one of the portions, such that compression of the body causes the slideable disengagement of the first and second retaining formations generally as described above.

(39) At this stage the cleaning elements 22 are extended and ready to clean the casing.

(40) For some applications it may be desirable for fluid flow through the bore 35 to be restored during cleaning, for example to pump fluid through the bore and create allow a fluid back flow within the casing to wash cuttings away from the cutting elements 22 in use.

(41) Referring to FIG. 7, by raising fluid pressure within the axial bore 34 to a predetermined level the shear pins 28, which are located at the ball seat 30 are sheared and a ball seat sleeve 42 is released and moved downwards (direction D) by a distance sufficient to allow fluid flow F2 through the axial bore 35. Alternatively, the ball and/or ball seat may be deformable, so that by further increasing the pressure within the bore, the ball is forced through the ball seat and into the well.

(42) Cleaning the casing with a casing cleaner 10 according to the embodiments described above may be by axial reciprocating motion only where the casing cleaner 10 need only be moved upwards (to the left in the illustrated embodiment) and downwards (to the right in the illustrated embodiment) to remove debris from the inner casing wall. Any debris is expelled via the flutes.

(43) The configuration of the casing cleaner 10 according to embodiments of the present invention is such that reciprocation combined with rotation of the casing cleaner 10 is effective in removing debris from the casing wall quickly and efficiently.

(44) As shown in FIG. 8, the casing cleaner 10 is attached to a drill string 50 by suitable male or female mechanical connections 52, 54. The connections 52, 54 are suitable for attachment to a drill string 50, as shown in FIG. 8.

(45) The casing cleaner 10 is attached to the upper side of the drill string 50 comprising a drill bit 51. The assembly of drill string 50 and casing cleaner 10 is then run into the casing 56 in a known manner. The cleaning elements 10 are retracted into the tubular body for run-in and extended for cleaning.

(46) The drill string 50 is used in a known manner to drill a hole, for example a new wellbore. This may involve drilling, using a suitable drill bit 51, through the base of an existing casing 56 in which the drill string 50 is run-in and creating a new bore in the direction of a drilling target zone.

(47) When the drilling step is complete the cleaning operation can be initiated by extending the cleaning elements as described above. When cleaning is complete the method also includes retrieval of the casing cleaner 10 at surface as the drill string 50 is removed from the casing 56. After use the cleaning elements can be forced back to their retracted positions, for example during redressing or inspection/refit of the tool 10, and the setting sleeve can be re-set and replacement shear pins applied, thereby returning the recess to the retaining positon for re-use.

(48) FIGS. 9a and 9b show region B an alternative embodiment of an actuation system for a cleaning apparatus, with reference numerals in common with the embodiment of FIG. 6 provided with like reference numerals, incremented by 100.

(49) The associated tool comprises a setting sleeve 32 that is biased by annular springs (not shown) that act between the body and the sleeve to urge the sleeve towards the direction C. As previously shear pin 24 acts to restrain the setting sleeve 32 from moving longitudinally within the axial through bore 35.

(50) In this embodiment, the sleeve 32 is provided with a recess 160. A lip 164 extends part way across the recess to define an enclosed region 166. The radially inward surface 165 of the lip 164 is tapered.

(51) The cleaning element 22 is provided with a protrusion 156. The protrusion 156 has a longitudinally extending portion 156b having a tapered radially outward surface 157.

(52) The tapered surfaces 165 and 157 are slideable in relation to one another, as the second retention formation moves between the retaining position shown in FIG. 9a and the release position shown in FIG. 9b. The cleaning element is urged outwardly by the springs 50 to their extended positions. In this case, however, the tip 156c of the protrusion remains under the lip 164 when the cleaning element 22 is fully extended.

(53) This enables the cleaning elements to be selectively moved from their extended positions (FIG. 9b) to their retracted positions (FIG. 9a) downhole. Reduction of the pressure in the wellbore can be effected by cessation of pumping at the surface, by shearing shear pins 28 as described above, or re-opening the bore by forcing the ball 34 through the ball seat 30 as described above. The spring biased setting sleeve 32 then moves back towards the direction C, and the second retaining formation (recess 160) moves back towards the retracted position. Advantageously, the springs 50 slide back into the tapered cavities 36 during this process to reduce or remove the outward bias applied by the springs 50, such that the cleaning elements are effectively locked in place by the spring bias applied to the sleeve 32.

(54) Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention.