GB2295171A - Bore sealing - Google Patents

Abstract

Bore sealing apparatus such as a downhole plug (10) is adapted for location in a bore profile (12) to seal the bore against fluid pressure. The plug includes a body (14) carrying a circumferential seal (42). The seal is energised by a resilient seal actuator, such as a spring (20) comprising a stack of Belleville Washers. In use, the plug (10) may be set on the surface by compressing the spring (20). The plug (10) may then be run into the bore to the desired depth and the spring (20) released to energise the seal (42). The seal may be made of a copper nickel alloy, elastomer or plastics. <IMAGE>

Description

BORE SEALING This invention relates to bore sealing apparatus and in particular, but not exclusively, to bore sealing apparatus suitable for use in downhole applications.

According to the present invention, there is provided bore sealing apparatus comprising a body carrying a seal member and resilient seal actuating means, said means being releasable from an energy storing configuration to actuate the seal member to provide a seal between the body and a bore wall.

The invention is particularly suited for downhole applications. Thus, in use, the apparatus may be set on the surface by arranging the seal actuating means in the energy storing configuration. The apparatus may then be run into a bore to the desired depth and the means released to actuate the seal member. The requirement to apply seal setting forces through the running string, which may be in the form of a wireline, slickline or the like, is thus obviated. This simplifies the setting the apparatus and also allows application of seal setting forces greater than the force which may be applied directly via the string.

Preferably, the body includes at least two relatively moveable parts and the seal member is located therebetween. Most preferably, the seal actuating means acts between the body parts to produce deformation of the seal member. In a preferred embodiment, one of the body parts is a sleeve and the other body part is a mandrel.

If the mandrel forms an end surface of the apparatus and is fixed relative to the bore, any pressure to break the seal as maintained by the action of the seal actuating means is only effective over a relatively small area, and thus exerts a relatively small force, the bulk of the pressure force being resisted by the fixed mandrel.

Preferably also, the seal actuating means is releasable from the seal actuating configuration, to allow release of the seal member, and facilitate withdrawal of the apparatus from the bore. The seal member may be elastically deformable, to facilitate release of the seal when desired.

Preferably also, the body includes locking means for engagement with the bore wall to lock the body in the bore. The locking means may take any suitable form, and may comprise extendable members for selectively engaging the bore wall. In a preferred embodiment, the apparatus is adapted for location in a nipple profile or other restriction in a bore.

Preferably also, the locking means for locking the body in the bore and the seal actuating means are themselves actuated by a running tool. Most preferably, the running tool is operable to first actuate the locking means, and then release the seal actuating means.

Further, it is desirable that the running tool is only released from the apparatus when both the locking means and the seal actuating means have been actuated, thus providing a "tell tale" that the apparatus has been properly set.

This and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a part-sectional view of bore sealing apparatus in accordance with an embodiment of the present invention, shown mounted on a running tool; Figure 2 is an enlarged view of the apparatus of Figure 1, illustrated in the set position; and Figure 3 is a part-sectional view of the apparatus of Figure 1, shown together with a pulling tool.

Reference is first made to Figures 1 and 2 of the drawings, which illustrate bore sealing apparatus 10 in accordance with an embodiment of the invention in the form of tree plug or downhole plug 10. The illustrated plug 10 is adapted for location in a profile 12 in a bore to seal the bore against fluid pressure. The plug 10 comprises a generally cylindrical body 14 having a blanked-off lower end defined by a mandrel 16. The lower end of the mandrel 16 is chamfered so that the mandrel 16 may seat on a shoulder 18 defined by the bore profile 12.

From the lower end of the mandrel 16, which is of slightly smaller diameter than the bore, the mandrel 16 steps inwardly, the reduced diameter section providing mounting for seal actuating means, in the form of a stack of Bellville springs 20.

The upper spring is restrained by a collar 22 held in place by keys 24 which are themselves held in position by a mandrel core 26 which is itself retained by a releasable connector in the form of a shear pin 30.

The upper end of the mandrel 16 is threaded and pinned to a generally cylindrical casing 36. A sleeve 38 is mounted over the lower end of the casing 36 and extends down the outside of the mandrel 16 over the springs 20. The sleeve 38 further includes a radially inwardly extending ledge 40 which restrains the lower end of the springs 20.

The lowermost end of the sleeve 38, on the outside diameter of the plug 10, engages a resilient seal 42. In this particular example, the seal is formed of a copper nickel alloy, although the seal could equally well be formed of another resilient material, such as another metal or alloy, an elastomer or a plastic. The seal 42 is also located by a cylindrical spacer 44 mounted on the lower end of the mandrel 16. If desired, the seal may be located nearer to the lower end of the mandrel through use of a shorter spacer 44 and by providing a further spacer between the sleeve 38 and the seal 42.

In the "cocked" position, as illustrated in Figure 1, the springs 20 are held in compression between the collar 22 and the ledge 40 by locking keys 46, located in radially spaced apertures 48 in the casing 36 and having toothed outer faces 50 which engaged corresponding toothed profiles 52 in the upper end of the sleeve 38.

The keys 46 are maintained in a radially extended configuration by an inner sleeve 54, which is held in place by releasable means in the form of shear pins 56.

The outer face of the sleeve is provided with recesses 55 corresponding to legs 57 formed on the keys 46, in the cocked position the legs 57 straddling the recesses. The inner sleeve 54 includes a number of radially spaced apertures 58, each of which accommodates a tell tale key 60, the purpose of which will be explained in due course.

Upwardly of the sleeve 38, the casing 36 is provided with a further circumferential array of radially spaced apertures 62, each of which accommodates a locking key 64, adapted for engaging a corresponding bore profile 66.

Each key 64 is supported by an inner mandrel 68. For running in, the mandrel supports the keys 64 such that they lie within the outside diameter of the casing 36, as shown in Figure 1. The mandrel and keys 68, 64 include corresponding chamfered surfaces 70, 71 such that downward movement of the mandrel 68 relative to the casing 36 lifts the keys 64 on to a larger diameter portion of the mandrel to push the keys 64 radially outwardly.

Mounted internally of the mandrel 68 is a lock collet 72 which is slotted to form a plurality of spring fingers 74. Each finger 74 is provided with an enlarged head 76, and in the running position the heads 76 sit on the inner surface of the inner sleeve 54. The collet 72 is secured to the mandrel 68 by releasable means such as shear pins 78.

The upper end of the plug 10 is defined by a casing extension 80 which is threaded and pinned to the upper end of the casing 36.

Figure 1 illustrates the plug 10 mounted on a running tool 82, adapted to be mounted on the lower end of a wireline, slickline or the like. The running tool 82 comprises a central portion 84 including a hammer 86 and an inner support sleeve 88 which is threaded and pinned to the hammer. The sleeve 88 supports a further slotted collet 90 which defines a series of spring fingers 92 provided with enlarged heads 94. The collet 90 is fixed to the support sleeve 88 by shear pins 96.

The upper outer faces of the heads 94 engage the lower faces of the heads 76 of the collet fingers 74. A collar 98 is fixed to the upper end of the hammer 86 by shear pins 100 and engages the upper surface of the casing extension 80.

In use, the plug 10 and running tool 82 are run into a bore until the mandrel 16 engages the shoulder 18.

Jarring down shears the pins 100, allowing the hammer 86 to move relative to the collar 98. Further jarring brings the hammer surface into contact with a corresponding surface of the mandrel 68, which moves the keys 64 radially outwards into the profiles 66.

Further downward jarring brings the lower end of the mandrel 68 into contact with the inner sleeve 54 and once the shear pins 56 have been severed, the inner sleeve 54 is also moved downwardly. Such downward movement allows the key legs 57 to move radially inwardly into the sleeve recesses 55. On release of the keys 46, the sleeve 38 is moved downwardly relative to the mandrel 16 by the action of the springs 20 to compress the seal 42.

The downward movement of the sleeve 54 also brings the tell tale keys 60 opposite a circumferential recess in the casing 100, such that the keys 68 may move radially outward. By this point, the heads 76 of the spring fingers 74 are resting on the keys 60, such that the heads 76 also move outwardly. This movement lifts the heads 76 outwardly and clear of the heads 94 of the fingers 92, such that the running tool 82 may then be withdrawn from the plug 10.

Thus, the running tool 82 is only released from the plug 10 after the locking keys 64 have been extended and the sleeve-retaining keys 46 released, which prevents the plug 10 being left in the bore while not properly set.

However, if there is a problem with the setting of the plug 10, and the running tool 82 cannot be pulled free, upward jarring will cause the pins 96 to shear, allowing collapse of the running tool collet 90. Thus, the running tool 82 and running string may be pulled free.

The deformation of the seal produced by the springs 20 is such that the seal comes into sealing contact with the bore wall, and also with the outer surface of the mandrel 16. The seal 42 is thus subject to the potentially very large force exerted by the springs 20, and which force may be substantially larger from the force which could be applied directly through the running string.

It will be noted that the seal 42 presents only a relatively small area which is subject to the upward pressure A. The remainder of the pressure force is applied to the blanked-off end face of the mandrel 68, which is directly supported by the locking keys 64.

Thus, there is only a relative small pressure force acting on the plug area which is supported by the springs 20.

To remove the plug 10 from the bore, the core 26 is first lifted using a simple fishing tool (not shown).

Pulling the core 26 upwardly allows the keys 24 to move radially inwardly, thus freeing the collar 22 and allowing the springs 20 to relax. The seal 42 may thus return to the undeformed condition, allowing pressure equalisation across the plug 10.

Once the core 26 has been removed, a suitable pulling tool 106 is run into the bore, as illustrated in Figure 3 of the drawings. The pulling tool 106 comprises a central body 108 formed of a number of tubular parts which are threaded and pinned to one another. A first collet 110 is mounted on the exterior of the body 108 and rests on a shoulder 111 sized to sit on the mandrel 68.

The collet 110 is pinned and threaded to an inner collet 112 which is axially movably mounted on the body 108, defining spring fingers 114 with enlarged heads 116 and with the collet 112 in its lowermost position the heads 116 are supported by a shoulder or ledge 118 on the body.

A shear pin 113 extends from the collet 112 into an axial slot 115 in the body 108, which limits the degree of travel of the collects 110, 112 relative to the body 108.

Further, a compression spring 117 is provided above the collet 112 and retained on the body 108 in an annular pocket 119, and tends to bias the collet 112 downwardly.

Thus, when the tool 106 is run into the plug 10 the collet 112 is pushed upwardly against the action of the spring 117, off the ledge 118, allowing the fingers 114 to be deflected inwardly to clear the mandrel 68.

However, when the tool 106 is pulled upwardly the heads 116 engage a downwardly directed surface of the mandrel 68.

The pulling tool 106 may thus be jarred upwardly to lift the mandrel 68 and free the locking keys 64. The plug 10 may then be withdrawn from the bore.

If any difficulties are encountered, downward jarring will shear the pin 113, allowing the heads of the fingers of the collet 110 to move upwardly relative to the body 108 and over a hook 120 on the body 108, to retain the collets 110, 116 is a raised position relative to the body 108. Thus, when the tool 106 is next lifted, the heads of the second collet 116 are held off the ledge 118 and thus the fingers 114 may deflect inwardly to clear the mandrel 68.

On reaching the surface, the collet 110 is released from the hooks 120 by rotating a wedge 122 threaded to the body 108 downwardly to lift the collet fingers. Once the fingers have been lifted clear of the hooks 120, the spring 117 pushes the collet 110 downwards. To facilitate rotation of the wedge 122, a hole 124 suitable for receiving a punch or the like is provided therein.

From the above description it will be evident to those of skill in the art that this embodiment of the present invention provides a plug which may be simply and reliably set in a bore and which provides an effective seal, without the requirement to apply setting forces through the running string. Further, it is relatively straightforward to remove the plug 10 from the bore.

It will further be clear to those of skill in the art that the plug 10 described above is merely exemplary of the present invention and various modifications and improvements may be made thereto without departing from the scope of the present invention.

Claims (16)

1. Bore sealing apparatus comprising a body carrying a seal member and resilient seal actuating means, said means being releasable from an energy storing configuration to actuate the seal member to provide a seal between the body and the bore wall.

2. The apparatus of claim 1 wherein the body includes at least two relatively movable parts and the seal member is located therebetween.

3. The apparatus of claim 2 wherein the seal actuating means acts between the body parts to produce deformation of the seal member.

4. The apparatus of claim 2 or 3 wherein one of the body parts is a sleeve and the other body part is a mandrel.

5. The apparatus of claim 4 wherein the mandrel forms an end surface of an apparatus and, in use, is fixed relative to the bore.

6. The apparatus of any of the preceding claims wherein the seal actuating means is releasable from the seal actuating configuration to allow release of the seal member and facilitate withdrawal of the apparatus from the bore.

7. The apparatus of claim 6 wherein the seal member is elastically deformable.

8. The apparatus of any of the preceding claims wherein the body includes locking means for engagement with the bore wall to lock the body in the bore.

9. The apparatus of claim 8 wherein the locking means comprises extendable members for selectively engaging the bore wall.

10. The apparatus of claim 9 wherein the apparatus is adapted for location in a nipple profile or other bore restriction.

11. The apparatus of any of claims 8, 9 or 10 wherein the locking means and the seal actuating means are adapted for actuation by a running tool.

12. The apparatus of claim 11 in combination with a running tool.

13. The apparatus and running tool of claim 12 wherein the running tool is operable to first actuate the locking means, and then release the seal actuating means.

14. The apparatus and running tool of claim 12 or claim 13 wherein the running tool is only released from the apparatus when both the locking means and the seal actuating means have been actuated.

15. The apparatus of any of the preceding claims wherein the seal member is actuated solely by the resilient seal actuating means.

16. Bore sealing apparatus substantially as described herein and as illustrated in the accompanying drawings.