WO2014174325A2

WO2014174325A2 - Downhole apparatus and method

Info

Publication number: WO2014174325A2
Application number: PCT/GB2014/051318
Authority: WO
Inventors: Neil Andrew Abercrombie Simpson; Alexander Craig Mackay
Original assignee: Neil Andrew Abercrombie Simpson; Alexander Craig Mackay
Priority date: 2013-04-26
Filing date: 2014-04-28
Publication date: 2014-10-30
Also published as: GB201307695D0; WO2014174325A3

Abstract

A downhole apparatus (10) comprises a substantially tubular body (12) having a throughbore (14) and connection means (16, 18) for coupling the apparatus (10) to adjacent downhole tools. A central portion of the body (12) defines a radially upset portion (20) comprising a number of circumferentially spaced slots or bays (22), each bay (22) communicating with the throughbore (14) and configured to receive a stabiliser blade (24), the stabiliser blades (24) configured in use to move from a first, retracted, configuration to a second, expanded, configuration for engaging a bore wall (B).

Description

DOWNHOLE APPARATUS AND METHOD

FIELD OF THE INVENTION

This invention relates to a downhole apparatus and method. More particularly, but not exclusively, embodiments of the invention relate to an apparatus and method for stabilising a downhole tool, such as an under-reamer or expandable drilling reamer, in a high angle or horizontal wellbore.

BACKGROUND TO THE INVENTION

In the oil and gas industry, and more specifically in the exploration and production drilling phase of operations, there are a number of situations where it may be desired to enlarge an existing section of a borehole. For example, in some instances it may simply be desired to enlarge a section of borehole which was initially drilled, for well control purposes, at a smaller diameter. In other instances, it may be desired to enlarge a section of borehole for directional reasons, for example to facilitate the formation of a lateral borehole. In these applications, enlargement of the borehole may be performed using a fixed gauge tool. However, in other more complex situations it may be desired to enlarge a section of borehole below a restriction; in which case the borehole enlargement must be carried out by an expandable enlargement device, such as an under-reamer or expandable drilling reamer known in the art.

Under-reamers were regularly used 20 years ago for enlarging the borehole below 12 5/8 inch blow out preventers (BOPs) in order to provide sufficient annular space to cement the 13 3/8 inch casing. However, this application has largely disappeared with the introduction of larger bore BOPs. More recently, the drive to recover hydrocarbons from deeper and more difficult to reach reservoir formations has led to the greater use of long extended reach and horizontal wells, this type of well borehole being referred to as an Extended Reach Development well or "ERD" well.

In ERD wells with extended reach and increased wellbore angle, problems are regularly encountered that require the use of intermediate casing strings. These intermediate casing strings are normally closely nested in size and take up space that was previously available for drill bits of sufficient size to drill a hole suitable for cementing the next casing string. For example, in conventional wells a 26 inch hole is required to run and cement 20 inch casing and a 17 ½ inch hole is required to run a 13 3/8 inch casing which would normally be the next casing size run. The 17 ½ inch drill bit used to drill this hole size can be run through 20 inch casing, as can the next string of 13 3/8 inch casing; leaving an annular radial space of approximately 2 inches. However, if an intermediate size of casing such as 16 ¾ inch is run in a 17 ½ inch hole this provides a radial clearance of only 0.37 inches, this being of insufficient size to effectively cement the 16 ¾ inch casing into the borehole as there would be insufficient annular space to carry out a good cement job. Under these circumstances, an expandable enlargement device or under-reamer would have to be run to enlarge the 17 ½ inch hole, typically to a minimum of 21 inches, in order to carry out an effective cement job. The current frequent use of intermediate casings has consequently developed a new market for borehole enlargement devices such as under-reamers.

However, the use of ERD wells presents a number of problems for conventional tools and equipment.

For example, for expandable drilling devices such as conventional under- reamers and expandable drilling reamers, the majority of ERD wells are now being drilled at high deviation angle (from vertical) and, in many cases, horizontally. This means that conventional tools are lying on the low side of the borehole as opposed to hanging vertically downwards as they would be in a more conventional well borehole, resulting considerable cyclic loading being applied to the extended cutter arm of the under-reamer or expanded drilling reamer which in turn leading to excessive vibration, fatigue and possible partial or full closure of the cutter arms themselves; requiring remedial operations to be carried out at significant time and expense to an operator.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an apparatus for stabilising a downhole tool, such as an under-reamer or expandable drilling reamer, in a high angle or horizontal wellbore, the apparatus comprising:

a body;

a bore-engaging member radially moveably disposed on the body,

wherein the apparatus is configurable between a first, retracted, configuration and a second, extended, configuration, the bore-engaging member in said second configuration defining a radially extended position with respect to the body for engaging a bore wall.

Beneficially, embodiments of the present invention permit stabilisation of a downhole tool, such as an under-reamer or expandable drilling reamer, in a high angle or horizontal wellbore, thereby preventing or at least mitigating excessive vibration and fatigue loading on the under-reamer or drilling reamer which may otherwise occur.

The apparatus may comprise a downhole stabiliser.

In particular embodiments, the apparatus may comprise an expandable downhole stabiliser.

The first configuration may define a run-in configuration of the apparatus and the second configuration may define an activated configuration of the apparatus.

In use, the apparatus may be run into a borehole in the first configuration and activated to the second configuration.

The bore-engaging member may be of any suitable form and construction.

The bore-engaging member may comprise or form part of a stabiliser member or stabiliser blade. The bore-engaging member may be configured to engage the bore wall to urge the body away from the bore wall. For example, in a high angle or horizontal wellbore, the bore-engaging member may be configured to engage the bore wall to urge the body away from the low side of the wellbore.

Alternatively or additionally, the apparatus may comprise, or form part of, a reaming tool. The bore-engaging member may comprise, or form part of, a reaming member or reaming blade. The bore-engaging member may be configured to engage the bore wall to ream the wellbore.

The apparatus may comprise one bore-engaging member. However, in particular embodiments, the apparatus may comprise a plurality of bore-engaging members arranged around the body. In preferred embodiments, the apparatus may comprise three bore-engaging members circumferentially arranged around the body at 120 degrees, although any other suitable arrangement may be used where

appropriate.

The apparatus may comprise a coupling arrangement for coupling the bore- engaging member to the body.

The coupling arrangement may be configured to control the movement of the bore-engaging member between the first configuration and the second configuration.

The apparatus may be configured so that the bore-engaging member is urged substantially radially outwards from the first configuration to the second configuration. However, in particular embodiments the apparatus may be configured so that the bore- engaging member is urged radially and axially in order to move between the first configuration and the second configuration. The coupling arrangement may comprise one or more roller. The roller may be operatively associated with the bore-engaging member. For example, the roller may be disposed on the bore-engaging member. For example, the roller may be disposed in and extend from a recess or bore in the bore-engaging member. In particular embodiments, the roller may be disposed through and extend from the bore-engaging member. The coupling arrangement may comprise a plurality of the rollers. The rollers may be axially spaced. In particular embodiments, the coupling arrangement may comprise two axially spaced rollers, each extending through and out from the bore- engaging member. However, it will be recognised that other arrangements may be employed. For example, four rollers may alternatively be employed, two rollers extending from each side of the bore-engaging member. A bearing may be disposed between the roller and the bore-engaging member. In use, the bearing may permit the roller to rotate relative to the bore-engaging member to facilitate movement of the bore- engaging member.

The coupling arrangement may comprise a profile.

The profile may comprise a cam profile. The roller may define a cam follower of the coupling arrangement.

The profile may be disposed in or on the body. Alternatively, the profile may be provided in a profile member. The profile member may be adapted to be secured to the body. Alternatively, the profile member may not be secured to the body. In particular embodiments, the profile may be provided in a profile plate or the like.

The body may be of any suitable form and construction. In particular

embodiments, the body comprises a cylindrical mandrel having a throughbore for passage of fluid therethrough.

The body may further comprise attachment means provided at one or both ends for coupling the body to another element, such as drill tubulars or other components of a drill string. The attachment means may be of any suitable form. For example, the attachment means may comprise a threaded connection, in particular but not exclusively a threaded box and pin connection. Alternatively, the attachment means may comprise or further comprise an adhesive bond, quick connect attachment or other suitable connector.

The body may comprise an upset diameter portion, that is a portion having greater radial extent that the remainder of the body. The upset diameter body portion may extend substantially axially.

The upset diameter body portion may define or provide mounting for the bore- engaging or members of the apparatus.

A bay, recess or pocket may be provided in the body, in particular but not exclusively, the upset diameter portion of the body. The bay may be adapted to receive the bore-engaging member. In embodiments where the profile is formed in the body, the profile may be formed in the bay. In embodiments comprising a profile member, the bay may be adapted to receive the profile member.

The bay may be formed by any suitable means. In particular embodiments, the bays may be machined.

An activation arrangement may be provided. The apparatus may comprise the activation arrangement. For example, the activation arrangement may be integrally formed with or coupled to the apparatus. Alternatively, the apparatus may be operatively associated with the activation arrangement. For example, the activation arrangement may comprise an activation tool. The activation tool may be run into the borehole with the apparatus. Alternatively, the activation tool may be run into the borehole separately from the apparatus.

The activation arrangement may be of any suitable form. The activation apparatus may comprise at least one of a hydraulic activation arrangement, a pneumatic activation arrangement, and/or mechanical activation arrangement.

In particular embodiments, the activation arrangement may comprise a sleeve adapted for location within the body throughbore. In use, the sleeve may be configured for axial/longitudinal movement relative the body.

The sleeve may be configured to engage the bore-engaging member. In use, the sleeve may be configured to engage the bore-engaging member to move the bore- engaging member between the first configuration and the second configuration.

The sleeve comprises a male member configured to engage a female member provided in the bore-engaging member, or vice-versa. In particular embodiments, the sleeve may comprise radially engaging fingers configured to engage a recess in the bore-engaging member.

The sleeve may be configured to move in response to fluid pressure, in particular but not exclusively a fluid pressure applied from surface.

For example, the sleeve may define a fluid piston. In use, the sleeve may be configured to move in response to a pressure differential reaching a predetermined threshold.

The activation arrangement may be configured to bias the apparatus to the first configuration. The activation arrangement may comprise a biasing member, for example but not exclusively a spring element. In use, the spring element may define a return spring of the activation arrangement for urging the biasing member toward the first configuration where the pressure differential is below the predetermined threshold. Beneficially, this provides a fail-safe design in the event of loss of fluid pressure control.

The apparatus may be lockable in the first configuration.

For example, the bore-engaging member may be captivated by the body in the first configuration, and the bore-engaging member may be capable of movement from the first configuration only when acted upon by the activation arrangement.

The apparatus may be lockable in the second configuration.

Embodiments of the invention thus provide a relatively simple but robust expandable stabiliser configured to move from a locked smaller diameter first configuration to a locked larger diameter second configuration by the action of flow rate generated forces acting on a drive piston while also having the range and strength capability to handle the torsional compressive and tensile loads required to operate in a drilling environment.

According to a second aspect of the present invention, there is provided an assembly comprising a downhole tool and one or more apparatus according to the first aspect of the invention.

The downhole tool may comprise a drilling assembly for drilling a borehole. The drilling assembly may comprise an under-reamer.

The drilling assembly may comprise a reaming tool.

The drilling assembly may comprise an expandable reaming tool.

According to a third aspect of the present invention there is provided a method for stabilising a downhole tool, such as an under-reamer or expandable drilling reamer, in a high angle or horizontal wellbore, the method comprising:

disposing an apparatus according to the first aspect in a borehole; and moving the apparatus between a first, retracted, configuration and a second, extended, configuration, the bore-engaging member in said second configuration defining a radially extended position with respect to the body for engaging a bore wall.

It should be understood that the features defined above in accordance with any aspect of the present invention or below in relation to any specific embodiment of the invention may be utilised, either alone or in combination with any other defined feature, in any other aspect or embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a longitudinal section view of a downhole apparatus according to an embodiment of the present invention;

Figure 2 shows an enlarged view of part of the apparatus shown in Figure 1 ;

Figure 3 shows a longitudinal section view of the apparatus shown in Figures 1 and 2, in a first position;

Figure 4 shows a longitudinal section view of the apparatus shown in Figures 1 to 3, in a second position; and

Figure 5 shows an exploded view of the apparatus shown in Figures 1 to 4.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring first to Figure 1 of the accompanying drawings, there is shown a longitudinal section view of a downhole apparatus 10 according to an embodiment of the present invention, Figure 1 showing the apparatus 10 in a first, retracted, configuration suitable for running into a borehole (represented diagrammatically by reference B). In use the apparatus 10 takes the form of an expandable downhole stabiliser for stabilising a downhole tool, such as an under-reamer or expandable drilling reamer, in a high angle or horizontal wellbore.

As shown in Figure 1 , the apparatus 10 comprises a substantially tubular body

12 having a throughbore 14. Connection means in the form of female threaded box connections 16 and 18 are provided at respective ends of the body 12 for coupling the apparatus 10 to adjacent downhole tools T1 , T2. A central portion of the body 12 defines a radially upset portion 20 into which a number of circumferentially spaced slots or bays 22 are machined or otherwise formed. Each bay 22 communicates with the through bore 14 and is configured to receive a bore-engaging member in the form of a stabiliser blade 24, the stabiliser blades 24 configured in use to move from a first, retracted, configuration as shown in Figure 1 to a second, expanded, configuration as shown in Figure 4.

Referring now also to Figure 2 of the accompanying drawings, recesses 26 are formed in the wall of the bays 22, each recess 26 configured to receive a plate 28 (for clarity, one of the plates 28 is shown in its recess 26 while the other is shown separately; also the stabiliser blade 24 has been removed from Figure 2). Cam profile grooves 30 are machined or otherwise formed in the plates 28. In the illustrated embodiment, each stabiliser blade 24 retains the plates 28 in their respective recesses 26 by means of the close tolerance fit between the respective stabiliser blade 24, the plates 28 and the recesses 26 such that they are captive. However, it will be recognised that the plates 28 may alternatively be retained by other suitable means, such as by mechanical fasteners, adhesive bond or the like, where required for assembly and/or additional safety purposes.

As shown in Figures 1 and 2, each of the stabiliser blades 24 is held in place by two roller pins 32 which are introduced through entry holes 34 in the sides of the upset section of the body 14 and which extend through the groove 30 of the adjacent plate 28, through the stabiliser blade 24 via holes 25 and into the grooves 30 of the distal plate 28.

In use, the cam grooves 30 and the roller pins 32 together form a coupling arrangement between the body 12 and each stabiliser blade 24, the roller pins 32 being of a length such that they just fit across the bay 22 and extend into the full width of the cam plate grooves 30 on either side of the stabiliser blade 24.

It will be also understood that the introduction of the roller pins 32 through the entry holes 34 passes initially through a part of the profile grooves 30 of the cam plates 28 that can only be accessed during assembly of the apparatus 10, the final assembly stages preventing the roller pins 32 returning to that section of the profile grooves 30 when the apparatus 10 is in operation downhole, thereby making it impossible to lose the pins 32 and ensuring integrity and retention of the stabiliser blades 24 in use.

In the illustrated embodiment, the holes 25 are each provided with bearing bushes 36 to facilitate preferential rotation to take place when the roller pins 32 are urged to follow the cam profiles 30 in the plates 28.

As shown in Figure 1 , and as will be described further below, the apparatus 10 further comprises an activation arrangement for urging the stabiliser blades 24 from the first configuration shown in Figure 1 to the second configuration shown in Figure 4. In the illustrated embodiment, the activation arrangement comprises a central hollow tubular mandrel or sleeve 38 configured for location in the throughbore 14. A seal element 40 is disposed about a first end portion of the sleeve 38, such that the sleeve 38 and the throughbore 14 together define a drive piston 42. A return spring 44 and a smaller sealed piston (not shown) are positioned towards the opposite end portion of the sleeve 38. A spider ring 46 is fixed to a central portion of the sleeve 38, the spider ring 46 having radially projecting fingers 48 which pass from the throughbore 14 into each of the bays 22 to enlarge in holes formed in the underside of the stabiliser blades 24. In use, as fluid flow is pumped through the sleeve 38 hydraulic force is applied to the drive piston 42, this hydraulic force being created in the illustrated embodiment by a flow restriction formed within the sleeve 38 by the differential areas of the drive piston 42 and the smaller area of the sealed piston (not shown) at the other end of the sleeve 38, or a combination of both.

As the flow rate of the fluid being pumped through the sleeve 38 is increased, the hydraulic force applied to the drive piston 42 also increases until it reaches a threshold at which the applied force overcomes the spring force of the return spring 44. At this point, the sleeve 38, together with the spider ring 46, is urged in an axial direction with respect to the body 12.

By virtue of the engagement between the fingers 48 of the spider ring 46 and the stabiliser blades 24, axial movement of the sleeve 38 also acts to move the stabiliser blades 24. Moreover, as the stabiliser blades 24 are constrained by the roller pins 32 and cam profile grooves 30, axial movement of the sleeve 38 also results in radial movement of the stabiliser blades 24 with respect to the body 12 from a locked inboard position to a locked outboard position; the manner of this movement being defined by the shape and path of the upper and lower cam profile grooves 30 as described below.

As shown most clearly in Figure 2, the shape and profile of the cam grooves 30 are such that there is a lowered part of the cam profile grooves 30 where the roller pins 32 are first introduced into the body 12 via the entry holes 24. Once the sleeve 38 is installed and the stabiliser blades 24 have been moved up and outwardly to accommodate the sleeve 38, the roller pins 32 are moved out of alignment with the entry holes 24 and are locked in position, now being in contact with the cam profile groove face 30a which holds the stabiliser arms 24 in the closed position. When the stabiliser blades 24 are driven upwards by the hydraulic force applied to the drive piston 42, the roller pins 32 roll out of their locked position against face 30a and roll up cam profile face 30b, thereby moving the attached stabiliser blades 24 outward to their full gauge size.

Finally, as the stabiliser blades 24 continue to move up the profile cam groove

30 driven by the force generated on the drive piston 42, the roller pins 32 move into the final part of the cam profile groove 30c. In this position, the cam profile 30 moves slightly down or inward with respect to the main body axis such that faces 50, 52 and 54 on the stabiliser blades 24 settle down to contact the faces 56, 58 and 60 respectively of the body 12 (see Figure 4). In this position, the stabiliser blade 24 are fully extended and locked out with the upwards and inward thrust loads being supported on the contact faces 50, 52, and 54, and 20, 22 and 24, and 56, 58 and 60 respectively, thereby relieving any further load on the roller pins 32.

In order to move the stabiliser blade 24 back to the first configuration, circulation of fluid is stopped or at least reduced to below the level at which the force transmitted to the drive piston 42 is insufficient to retain the return spring 44, allowing the return spring 44 to push the sleeve 38 back to the start position and, in doing so, drive the stabiliser blades - together with the roller pins 32 back down the profile cam grooves 30 to return the stabiliser blades 24 to their closed and locked position. IN the illustrated embodiment, the spring 44 is selected to have a spring force sufficient to return the apparatus 10 to the first configuration. However, in the event that the spring force is not sufficient to achieve this, then the action of pulling on the main body 12 with downward friction or contact force on the stabiliser blades 24 will cause them to move out of their locked position with the roller pins 32 following the path of cam groove profile 30 into the closed and locked position, effectively creating a failsafe mechanism for stabiliser blade closure.

It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention.

For example, the blades may be provided with reaming elements.

Claims

1. An apparatus for stabilising a downhole tool, such as an under-reamer or expandable drilling reamer, in a high angle or horizontal wellbore, the apparatus comprising:

a body;

a bore-engaging member radially moveably disposed on the body,

2. The apparatus of claim 1 , wherein the apparatus comprises a downhole stabiliser.

3. The apparatus of claims 1 or 2, wherein the apparatus comprises an expandable downhole stabiliser.

4. The apparatus of any preceding claim, wherein the first configuration defines a run-in configuration of the apparatus and the second configuration may define an activated configuration of the apparatus.

5. The apparatus of any preceding claim, wherein the apparatus is run into a borehole in the first configuration and activated to the second configuration.

6. The apparatus of any preceding claim, wherein the bore-engaging member comprises or forms part of a stabiliser member or stabiliser blade.

7. The apparatus of any preceding claim, wherein the bore-engaging member is configured to engage the bore wall to urge the body away from the bore wall.

8. The apparatus of any preceding claim, wherein the apparatus comprises, or forms part of, a reaming tool.

The apparatus of any preceding claim, wherein the bore-engaging member comprises, or forms part of, a reaming member or reaming blade.

The apparatus of any preceding claim, wherein the bore-engaging member is configured to engage the bore wall to ream the wellbore.

The apparatus of any preceding claim, wherein the apparatus comprises one bore-engaging member.

The apparatus of any one of claims 1 to 10, wherein the apparatus comprises a plurality of bore-engaging members arranged around the body.

The apparatus of any one of claims 1 to 10 or 12, wherein the apparatus comprises three bore-engaging members circumferentially arranged around the body at 120 degrees.

The apparatus of any preceding claim, wherein the apparatus comprises a coupling arrangement for coupling the bore-engaging member to the body.

The apparatus of claim 14, wherein the coupling arrangement is configured to control the movement of the bore-engaging member between the first configuration and the second configuration.

The apparatus of any preceding claim, wherein the apparatus is configured so that the bore-engaging member is urged radially and/or axially in order to move between the first configuration and the second configuration.

The apparatus of any preceding claim, wherein the coupling arrangement comprises one or more rollers.

The apparatus of claim 17, wherein the roller is operatively associated with the bore-engaging member.

The apparatus of claims 17 or 18, wherein the roller is disposed through and extend from the bore-engaging member.

20. The apparatus of any one of claims 17, 18 or 19, wherein the coupling arrangement comprises a plurality of rollers.

21. The apparatus of claim 20, wherein the rollers are axially spaced.

22. The apparatus of claims 20 or 21 , wherein the coupling arrangement comprises two axially spaced rollers, each extending through and out from the bore- engaging member.

23. The apparatus of any one of claims 17 to 22, wherein a bearing is disposed between the roller and the bore-engaging member.

24. The apparatus of any one of claims 14 to 23, wherein the coupling arrangement comprises a profile.

25. The apparatus of claim 24, wherein the profile comprises a cam profile.

26. The apparatus of claim 25, wherein the roller defines a cam follower of the coupling arrangement.

27. The apparatus of any one of claims 25 to 26, wherein the profile is disposed in or on the body.

28. The apparatus of any one of claims 25 to 26, wherein the profile is provided in a profile member.

29. The apparatus of claim 28, wherein the profile member is adapted to be secured to the body.

30. The apparatus of claim 28, wherein the profile member is not secured to the body.

31. The apparatus of any one of claims 27 to 30, wherein the profile is provided in a profile plate or the like.

32. The apparatus of any preceding claim, wherein the body comprises a cylindrical mandrel having a throughbore for passage of fluid therethrough.

33. The apparatus of any preceding claim, wherein the body comprises comprise attachment means provided at one or both ends for coupling the body to another element, such as drill tubulars or other components of a drill string.

34. The apparatus of claim 33, wherein the attachment means comprises a threaded connection, in particular but not exclusively a threaded box and pin connection.

35. The apparatus of claim 33, wherein the attachment means comprises or further comprises an adhesive bond, quick connect attachment or other suitable connector.

36. The apparatus of any preceding claim, wherein the body comprises an upset diameter portion, that is a portion having greater radial extent that the remainder of the body.

37. The apparatus of claim 36, wherein the upset diameter portion extends substantially axially.

38. The apparatus of claims 36 or 37, wherein the upset diameter body portion defines or provides mounting for the bore-engaging or members of the apparatus.

39. The apparatus of any preceding claim, wherein a bay, recess or pocket is provided in the body.

40. The apparatus of claim 39 when pending from claim 36, wherein a bay, recess or pocket is provided in in the upset diameter portion of the body.

41. The apparatus of claims 39 or 40, wherein the bay is adapted to receive the bore- engaging member.

42. The apparatus of any one of claims 39 to 41 , when depending from claim 27, wherein the profile is formed in the bay.

43. The apparatus of any one of claims 39 to 41 , when depending from claim 28, wherein the bay is adapted to receive the profile member.

44. The apparatus of any one of claims 39 to 43, wherein the bay is machined.

45. The apparatus of any preceding claim, wherein the apparatus comprises an activation arrangement.

46. The apparatus of any one of claims 1 to 44, wherein the apparatus is operatively associated with an activation arrangement.

47. The apparatus of claim 45 or 46, wherein the activation arrangement comprises at least one of a hydraulic activation arrangement, a pneumatic activation arrangement, and/or mechanical activation arrangement.

48. The apparatus of any one of claims 45 to 47, wherein the activation arrangement comprises a sleeve adapted for location within the body throughbore.

49. The apparatus of claim 48, wherein the sleeve is configured to engage the bore-engaging member.

50. The apparatus of claims 48 or 49, wherein the sleeve comprises a male member configured to engage a female member provided in the bore-engaging member, or vice-versa.

51. The apparatus of any one of claims 48 to 50, wherein the sleeve comprises radially engaging fingers configured to engage a recess in the bore-engaging member.

52. The apparatus of any one of claims 48 to 51 , wherein the sleeve is configured to move in response to fluid pressure, in particular but not exclusively a fluid pressure applied from surface.

53. The apparatus of any one of claims 45 to 52, wherein the activation

arrangement is configured to bias the apparatus to the first configuration.

54. The apparatus of any one of claims 45 to 53, wherein the activation arrangement comprises a biasing member, for example but not exclusively a spring element.

55. The apparatus of any preceding claim, wherein the apparatus is lockable in the first configuration.

56. The apparatus of any preceding claim, wherein the apparatus is lockable in the second configuration.

57. A drilling assembly comprising a downhole tool and one or more apparatus according to any preceding claim.

58. The drilling assembly of claim 57, wherein the downhole tool comprises a drilling assembly for drilling a borehole.

59. The drilling assembly of claims 57 or 58, wherein the drilling assembly comprises an under-reamer.

60. The drilling assembly of any one of claims 57 to 59, wherein the drilling assembly comprises a reaming tool.

61 The drilling assembly of any one of claims 57 to 60, wherein the drilling assembly comprises an expandable reaming tool.