Downhole cleaning apparatus

Abstract

A downhole cleaning apparatus (10) comprising a tubular body (12). The tubular body (12) comprises comprising a plurality of openings (20) therethrough. Each opening (20) defines at least part of a helix extending longitudinally and circumferentially about the tubular body (12). The downhole cleaning apparatus (10) also includes a plurality of cleaning elements (22). Each cleaning element (22) is configured to extend through an opening (20) and to extend outwards from an outer surface of the tubular body (12). The cleaning elements (22) are distributed about the tubular body (12) and each cleaning element (22) defines at least part of a helix extending longitudinally and circumferentially about the tubular body. The openings (20) and the cleaning elements (22) are grouped to define a plurality of substantially continuous helical paths (18). Each helical path (18) extends substantially end to end of the tubular body and the helical paths (18) are distributed relative to each other to define a cleaning surface of at least 360 degrees.

Claims

1. A downhole cleaning apparatus comprising: a tubular body comprising a plurality of openings therethrough, wherein each opening defines at least part of a helix extending longitudinally and circumferentially about the body; and a plurality of cleaning elements having a retracted state and a use state; said plurality of cleaning elements configured to extend through the openings and to extend outwards from an outer surface of the body when in said use state, wherein the cleaning elements are distributed about the body and each cleaning element defines at least part of a helix extending longitudinally and circumferentially about the body, wherein the openings and cleaning elements are grouped to define a plurality of substantially continuous helical paths, each of which extend substantially end to end of the tubular body and are distributed to define a cleaning surface of at least 360 degrees, and wherein the helical paths define a plurality of flutes and ribs, each flute being defined by at least part of a helix extending longitudinally and circumferentially about the body, wherein a rib is defined between each flute; wherein the said openings are provided through the ribs; wherein the cleaning elements are retractable and extendable, wherein when retracted the cleaning elements are storeable within the body during said retracted state until required for use during said use state; and wherein the ribs define the outermost surfaces of the cleaning apparatus when the cleaning elements are stored within the body.

2. A downhole cleaning apparatus as claimed in claim 1, wherein the helical paths are arranged such that the combined circumferential extent of the helical paths is at least 360 degrees.

3. A downhole cleaning apparatus as claimed in claim 2, comprising at least three ribs and at least three flutes.

4. A downhole cleaning apparatus as claimed in claim 2, wherein the cleaning elements are retractable and extendable, wherein, in a retracted position the cleaning elements are held within the tubular body and cannot contact a casing wall in use and, in an extended position, the cleaning elements extend from said outermost surfaces of the ribs.

5. A downhole cleaning apparatus according to claim 1, wherein each cleaning element is biased to an extended position, and wherein each of said plurality of cleaning elements is maintained in a retracted position by an interlocking retaining member; said interlocking retaining member reversibly interlocking said each of said plurality of cleaning elements with another portion of the downhole cleaning apparatus maintaining said each of said plurality of cleaning elements in said retracted position; said interlocking retaining member being operable to be released to free said each of said plurality of cleaning elements to move radially outward to achieve said extended position.

6. A downhole cleaning apparatus according to claim 1, wherein the openings are provided by a plurality of slots and wherein a corresponding number of cleaning elements are provided wherein a cleaning element extends through each of said plurality of slots.

7. A downhole cleaning apparatus according to claim 1, wherein when required for use and in said use state, the cleaning elements are extendable wherein they extend outwards from an outermost surface of the ribs.

8. A downhole cleaning apparatus as claimed in claim 1, further comprising a holding system and an activation system, whereby the cleaning elements are held in a retracted position by the holding system until required for use and wherein the activation system is operable to at least prime the cleaning elements for movement from a retracted position to an extended position.

9. A downhole cleaning apparatus as claimed in claim 8, wherein the holding system comprises one or more shear pins.

10. A downhole cleaning apparatus according to claim 9, wherein the activation system comprises at least one of a ball and a dart.

11. A downhole cleaning apparatus according to claim 10, wherein the seat is configured to allow the ball or dart to pass through after the cleaning elements assume an extended position.

12. A downhole cleaning apparatus as claimed in claim 11, wherein the seat is connected to a moveable sleeve, wherein the sleeve is movable under application of a predetermined fluid pressure.

13. A downhole cleaning apparatus according to claim 8, wherein the activation system comprises a setting sleeve, internal to the tubular body, and operable to move in an axial direction relative to the tubular body and operable to break or shear at least one or more shear pins such that the cleaning elements are at least partially primed for movement from retracted to extended.

14. A downhole cleaning apparatus as claimed in claim 13, wherein the setting sleeve and the cleaning elements each comprise an angular profile such that movement of the sleeve relative to the cleaning element is effective in moving the cleaning elements from retracted to extended.

15. A downhole cleaning apparatus as claimed in claim 8, wherein, in use, the activation system comprises one or more stages of activation, and wherein said activation system comprises at least one of a mechanical trigger, an electronic signal and an applied fluid pressure.

16. A downhole cleaning apparatus as claimed in claim 5, further comprising a mechanical or hydraulic spring arranged to assist movement of the cleaning elements from a retracted position to an extended position; and to maintain position of the cleaning elements in the extended position.

17. A downhole cleaning apparatus according to claim 1, wherein each cleaning element comprises a cutting profile operable, in use, by axial reciprocation to remove debris from a surface in which the cleaning elements are in contact.

18. A downhole cleaning apparatus according to claim 1, wherein the cleaning element is at least one of a scraper blade and a brush.

19. A downhole cleaning apparatus as claimed in claim 1, wherein each said opening is provided through a said outermost surface of a corresponding rib.

20. A downhole cleaning apparatus as claimed in claim 1, wherein the tubular body has a radial thickness extending from an inner diameter to an outer diameter; wherein each opening extends through said radial thickness; wherein the cleaning elements each slideably extend through a said opening.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic representation of a downhole cleaning apparatus according to an embodiment of the present invention in a retracted position;

(3) FIG. 2 is a schematic representation of a downhole cleaning apparatus according to an embodiment of the present invention in an extended position;

(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 a schematic representation of an axial cross section of the downhole cleaning apparatus as illustrated in FIG. 2 wherein the cleaning elements are in an extended position;

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

(7) FIG. 6 is a schematic representation of an assembly of a casing cleaner as illustrated in FIGS. 1 to 5 and a drill string.

BRIEF DESCRIPTION

(8) FIGS. 1 and 2, each show a casing cleaner 10, which represents a downhole cleaning apparatus according to an embodiment of the present invention. 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 visible 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.

(9) 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.

(10) Each rib 14 includes slots 20 through which cleaning elements 22 extend. 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.

(11) 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.

(12) The cleaning elements 22 in the illustrated embodiment are scraper blades. Scraper blades comprise a plurality of cutting edges 23 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 constructed from forgings. The material choice and construction of the blades is that which demonstrates long lasting durability and excellent scraping characteristics. Alternatively, the cleaning elements may be 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.

(13) The cleaning elements 22 are arranged to be retracted, when run in, see FIG. 1 and extended, when in use, see FIG. 2. Shear pins 24, 26 are located through holes in the tubular body 12 to retain the cleaning elements 22 in a retracted position until a predetermined fluid pressure is applied via the axial bore 34 (see FIGS. 3 and 4). In the illustrated example, fluid pressure is used to activate a mechanism operable to break or shear the pins 26, 28 such that the cleaning elements 22 are at least partially primed for extension.

(14) FIGS. 3 and 4 each illustrate a cross-sectional view of the casing cleaner 10 as illustrated in FIGS. 1 and 2 respectively. It will be appreciated that FIGS. 3 and 4 provide a clearer representation of how the cleaning elements 22 are held in the retracted position (as illustrated in FIGS. 1 and 3) and how the cleaning elements 22 move to the extended position (as illustrated in FIGS. 2 and 4).

(15) FIGS. 3 and 4 represent the activation stages required to release the cleaning elements 22 from the retracted position to the extended position. FIG. 3 represents the retracted position where the cleaning elements 22 are held within the tubular body 12 and therefore cannot contact the casing wall. In the illustrated embodiment the cleaning elements 22 are biased by spring force F1 to the extended position, but are held in a retracted position by a series of shear pins 24, 26, 28. Shear pin 24 acts to restrain a setting sleeve 32 from moving within the axial bore 35. Shear pin 26 acts to restrain the cleaning elements 22 in the retracted position and shear pin 28 acts to restrain a ball seat 30.

(16) The setting sleeve 32 is positioned within the axial bore 35. The setting sleeve 32 is held against movement relative to the tubular body 12 by shear pin 24. The shear pin 24 engages with the tubular body 12 and the setting sleeve 32. The setting sleeve 32 includes an external profile with tapered sections 36 which engage with similar profiles on the inside surface of the cleaning elements 22, such that when the setting sleeve 32 is released it moves axially, as guided by the bore 35, to move the cleaning elements 22 to the extended position.

(17) The shear pins 24, 26, 28 are sheared or broken as a result of fluid pressure being applied within the axial bore 35. A predetermined fluid pressure or force is required to shear the pins 24, 26, 28 such that the sleeve 32 is released to act upon the cleaning elements 22. Each shear pin 24, 26, 28 responds to a different predetermined pressure, where the shear pins 24 shear or break upon application of pressure lower than the pressure required by shear pin 26 and shear pin 26 will shear or break upon application of pressure lower than the pressure required by shear pin 28.

(18) To activate the cleaning elements 22 to the extended position the axial bore 35 is sealed by release of a ball 34 (see FIGS. 3 and 4). As illustrated in FIG. 3, the ball 34 is dropped into the axial bore 35 from surface and is either pumped down 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 (to the right in the illustrated embodiment).

(19) As the setting sleeve 32 moves downwards, towards the drill bit 51 (see FIG. 6) the tapered sections 36 acts upon the similarly shaped profile of the cleaning elements 22 thereby priming the cleaning elements 22 for movement to the extended position. A substantially radial load is generated by the physical contact of the setting sleeve 32 upon the cleaning element 22 and acts to shear the shear pins 26 to release the cleaning elements 22. By shearing the shear pin 26 the cleaning elements 22 are primed for extension under the spring force F1, which biases the cleaning elements 22 to the extended position.

(20) The cleaning elements 22 are restrained from being fully expelled from the tubular body 12 by engagement with the casing wall and locking pins 38 as shown in the illustrated embodiment. The locking pins 38 are arranged to slide within a slot 40 provided in the body of the cleaning element 22 such that the range of movement of the cleaning element 22 is controlled.

(21) At this stage the cleaning elements 22 are extended and ready to clean the casing. To begin the cleaning process fluid flow through the casing cleaner 10 needs to be restored. Referring to FIG. 5, 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 by a distance sufficient to allow fluid flow F2 through the axial bore 35 and to the drill bit 51 beneath (see FIG. 6). Once fluid flow through the device 10 is restored the cleaning elements 22 are in the ready position, where they are extended and ready for application to clean the casing in which they are deployed.

(22) 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.

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

(24) A method of application of the casing cleaner 10 according to described embodiments is illustrated in FIG. 6, where 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.

(25) The arrangement illustrated in FIG. 6 demonstrates an integrated formation and cleaning process.

(26) 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.

(27) 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.

(28) When the drilling step is complete the cleaning operation can be initiated wherein an activating device, such as a ball (described above) or a dart is released to block fluid flow through the centre of the assembly. Fluid F3 is pumped into the axial bore 35 of the casing cleaner 10 such that the activation process described above takes place to move the cleaning elements 22 from a retracted position to an extended position. The method includes resuming fluid flow through the device by releasing the sleeve 42 that provides support for the ball 34 or dart (not illustrated) and allowing fluid flow F2 through the device (see FIG. 5). When fluid flow F2 is resumed through the device the assembly is moved upwards and downwards (reciprocating motion) in the direction M1 (as illustrated in FIG. 6) such that the cleaning elements 22 actively clean debris from the casing wall 56.

(29) Pressure monitoring of fluid within the device may be used to determine when the casing cleaner 22 is fully extended and ready for use.

(30) Each stage of the activation process, as described above requires a predetermined, but different pressure to shear each shear pin 24, 26, 28. As such the activation of the cleaning elements 22 to an extended position is fully controllable. By monitoring the pressures within the axial bore 35 of the casing cleaner 10 it can be determined with certainty that the cleaning elements 22 are in the extended position and the cleaning process can be carried out with certainty also.

(31) 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.

(32) 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.