Downhole cleaning apparatus

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.