GB2280459A

GB2280459A - Device for retrieving elements from well bores

Info

Publication number: GB2280459A
Application number: GB9413685A
Authority: GB
Inventors: Bruce Hermann Forsyth Mcgarian
Original assignee: RED BARON
Current assignee: RED BARON
Priority date: 1993-07-07
Filing date: 1994-07-07
Publication date: 1995-02-01
Anticipated expiration: 2014-07-07
Also published as: GB9314048D0; GB2280459B; GB9413685D0

Abstract

A retrieval device, being part of a packer-miller assembly, comprises a central mandrel (33), an apertured sleeve (7), an annular cam member (17) and balls (36). The components are biased by a spring (27) into the configuration of Figure 2A until the device enters the bore of the element (40) to be retrieved, whereupon the sleeve (7) is displaced upwardly to allow the balls to run up cam surfaces (24) to reduce the diameter of the device to allow it to enter the element (40) bore. A collar (8) is released, e.g. by shear bolts, to allow the annular cam member (17) to move downwardly to release the device in the event that retrieval has to be aborted. <IMAGE>

Description

DVICE FOR RETRIEVING ELEMENTS FROM WELL BORES This invention relates to a device for retrieving elements from well bores and, more particularly, for retrieving smooth-bored elements from well bores.

Traditionally, packers have been set in well bores with tubing suspended below the packer A packer is a solid metal cylindrical body which is.secured to the well casing to resist upward and downward movement by means of circumferential upward and downward facing barbs. The packer has a central bore through which liquid can pass, The packer is sealed to the casing by resilient sealing rings.

In the past, packers and tubing have been provided with a stepped internal bore wherein a larger diameter bore portion is provided below the packer, the remainder of the tubing having the same inner diameter as the packer. The larger diameter bore portion called the mill out extension, provides a shoulder, such that a catch assembly can engage with the shoulder to prevent the packer from dropping down the well bore under gravity once the packer has been released by milling. The mill out extension. also permits the catch assembly to protrude below the packer in the larger diameter bore portion, such that the mill and catch assembly are free to rotate to mill the packer without damage to the catch assembly itself.

European patent 0086582 is directed to an oil well packer retriever for retrieving a packer with a stepped internal bore. The retriever comprises a packer miller for milling the packer to release it from the well casing, and a packer catcher mounted on a tubular member extending from the miller for engaging the packer once the packer is released. The packer catcher comprises a sleeve slidable along said tubular member and slotted to define resilient fingers, and including an emergency release means. The packer miller comprises a plurality of radial blades having end faces and side faces provided with abrasive material, the end faces being dimensioned to mill substantially the entire annular surface of the packer, and the side faces having said abrasive material extending along a major portion thereof.The catcher sleeve is urged by resilient means into engagement with a collar and the emergency release means comprises the collar being secured to the tubular member by shear pins or bolts adapted to shear at a predetermined stress.

Due to modified practice, some packers are now being supplied without mill out extensions, and are accordingly "smooth-bored". One reason for this is that such smooth-bored packers represent a significant cost saving to the purchaser. At present, if such a smooth-bored packer requires replacement, for example as a result of seal breakage permitting escape of gas, the packer is milled with a junk mill, or the like, and pushed to the bottom of the well, or retrieved on a second trip with a suitable spear.

As packers without mill out extensions become increasingly common, the need for a tool to mill and retrieve such a packer in one trip increases.

It is an aim of the present invention to facilitate retrieval of a smooth-bored element from a well bore.

It is an additional aim of the present invention to facilitate milling and retrieving of a smooth-bored packer in one trip.

According to the present invention there is provided a device for retrieval of a smooth-bored element from a well bore, the device comprising a catch assembly mounted on a tubular member for engaging the element, the catch assembly comprising a sleeve slidable along the tubular member and including an emergency release means, the sleeve being urged by resilient means towards a collar, the emergency release means comprising the collar being secured to the tubular member by holding means adapted to yield at a predetermined stress, wherein the sleeve has an aperture therethrough and the catch assembly additionally comprises an annular member interposed between the sleeve and the tubular member, the annular member having a camming surface thereon, and a cam element resting on said camming surface and extending through said aperture.

PreferabLy, the sleeve has a plurality of apertures spaced circumferentially around the sleeve, the annular member having a plurality of camming surfaces thereon, one camming surface corresponding to each aperture, and a plurality of cam elements, one resting on each camming surface and extending through the corresponding aperture.

In a particularly preferred embodiment, there are additionally a plurality of apertures spaced longitudinally along the sleeve, there being a camming surface and a cam element corresponding to each aperture.

Preferably, the annular member is provided with a radial flange which abuts against the collar and may act as a thrust bearing against the collar.

The holding means are preferably shear pins.

The retrieval device of the present invention may be used in combination with a packer miller for milling a packer to release it from the well casing, the tubular member extending from the miller for the catch assembly to engage the packer once the packer is released.

The device of the present invention is described hereafter with reference to a packer miller and retriever.

However, as is clear from the foregoing, it is not intended that the device be limited to such an embodiment, since it may be useful for retrieving other smooth-bored elements from well bores.

The device of the present invention will now be described in more detail by way of example with reference to the accompanying drawings, in which: Figure 1 is a layout sketch showing the arrangement of parts throughout the length of a packer retriever incorporating this invention; Figure 2A is a longitudinal part-section of the length indicated by "A" in Figure 1 prior to insertion of the device through a packer; and Figure 2B is a longitudinal part-section of the length indicated by "A" in Figure 1 after insertion of the device through a packer.

Referring to Figure 1, a packer retriever comprises an elongate assembly of parts, the main features of which are shown schematically to illustrate their sequential arrangement from top to bottom.

The retriever 1 has a tubular bore 2 extending from end to end for throughflow of liquid. The assembly is attachable to a drill string by standard AP1 conical screwed connectors, for example as indicated at 3.

The assembly includes one or, preferably, more debris collectors 4 (shown in part-section in Figure 1).

A packer miller 5 has radially extending fin-like projections 6 faced on their leading faces with tungsten carbide.

A slip joint 44 is included in the assembly typically between the mill head and the catch assembly to allow for axial movement of the upper part of the assembly whilst the packer catcher is secured to the packer or tubing bore, if this is necessary, e.g. to re-start milling after stalling of the packer miller.

A packer catcher 13 comprising a central tubular member or mandrel 33, a catch sleeve 7, and a series of cam elements for engagement in the bore of a packer, is mounted below the packer miller as will be described hereinafter.

A collar 8 is fixed to the tubular member of the catcher 13 by suitable means, for example by shear bolts or pins (and pin retainer screws) and is released by excessive force being applied to it during withdrawal of the retriever from the oil well. Once released the shear ring falls into engagement with a retaining ring 9.

The assembly terminates in a milling head 10 dimensioned to pass through the bore of a packer to remove any debris therein.

Liquid is pumped through the assembly during use to exit therefrom via ports located at 11 and 12 as debrisremoving jets.

Referring now to Figures 2A and 2B, the packer catcher 13 has a central tubular member in the form of a mandrel 33 with connections 14 and 15 to connect it to the slip joint 44 above and a bottom mill below, respectively.

The mandrel 33 has a spring location spigot 16 which is threaded along its length and onto which is screwed a spring compression collar 25 held with lock screws 26. Mounted against the spring compression collar 25 is a spring 27 followed by a thrust bearing wear ring 30 of a thrust bearing 29. The catch sleeve 7 fits over the mandrel below the thrust bearing 29 and an annular member 17 is interposed between the sleeve 7 and the mandrel 33. The annular member 17 has a radial flange 18 which extends below the sleeve 7 and abuts against a sleeve 8.

A shoulder 31 at the bottom of the spring location spigot of the mandrel 33 and an external shoulder 35 on the sleeve 7 limit the upward travel of the catch sleeve 7. The upper end 22 of the sleeve 7 is inserted into the thrust bearing 29, The mandrel 33 is provided with a stop ring groove 19 which is adjacent the upper end of the sleeve 7. A split stop ring 38 is inserted into the groove 19 and is retained using an O-ring or garter spring or other suitable means.

The split ring cooperates with an inner shoulder 20 on the sleeve 7 to restrict downward movement of the sleeve and to limit upward movement of the annular member 17 when entering the packer. Between the stop ring 38 and the annular member 17 are housed disc springs 42 which are pre-loaded when shear sleeve 8 is assembled. The split ring also cooperates with the top edge 21 of the annular member 17 to limit upward movement of the annular member.

The annular member 17 has wedge or camming surfaces 24 on its outer circumference corresponding to apertures 28 in the sleeve 7. A ball 36 is located in each aperture 28 and rests on the corresponding camming surface 24. Retaining shells 32 are clamped on the outside surface of the sleeve to prevent the loss of the balls 36 through the apertures 28.

A bush 23 is provided between the annular member 17 and the mandrel 33 to allow for rotation of the mandrel with respect to the remainder of the catch assembly when milling the packer.

A bail wire 41 is fitted in a groove on the mandrel 33 below annular member 17 and covered in a recess in the sleeve 8. The shear sleeve 8 is secured to the mandrel by means of shear pins 34 which are adapted to shear at a predetermined stress. The shear sleeve 8 has a counter bore to clear the bail wire.

Prior to insertion through a packer 4C, the catcher 13 is in the configuration shown in Figure 2A. The spring 27 acts on the sleeve 7 to push the lower end of the sleeve against the radial flange 18 of the annular member 17, the flange being supported against downward movement by the sleeve 8. With the sleeve 7 in the position shown in Figure 2A with respect to the annular member the balls 36 are rolled to their extended position on the camming surfaces 24.

On entry into the bore of packer 40, the balls 36 and the sleeve 7 are pushed upwardly against the bias of the spring 27. Any upward movement of the annular member 17 is limited by the split stop ring 38 and disc springs 42, but the sleeve may move upwardly until the shoulder 31 abuts the upper end 22 (shoulder 35) of the sleeve to limit the upward movement of the sleeve.

As the sleeve moves upward, the balls 36 run in along the taper of the camming surfaces 24 to a retracted position shown in Figure 2B, thus reducing the outside diameter of the assembly, such that the assembly fits inside the packer 40.

Whilst milling down the packer using the miller 5, the assembly moves down continuously, and any drag caused by the rotation of the mandrel 33 through the assembly will cause rotation of the assembly at a slower speed against the casing or packer inside diameter. The running surfaces are all hardened to reduce wear, and the lower end of the annular member 17 acts as a thrust bearing against the shear sleeve 8. Thus, the catch assembly is intended to accommodate rotation of the mandrel 33 whilst the miller 5 is being rotated to mill the packer.

When the packer has been fully milled, the packer and its associated tubing will drop rapidly, causing the balls 36 to roll downwards over the camming surfaces, thus forcing the balls outwards, over the surfaces to engage the inner surface of the packer 40 and lock the packer to the catch assembly, preventing the packer from dropping to the bottom of the well. The outward force on the balls, and hence on the packer, is created by the taper of the camming surfaces and is dependent on the weight of the packer and tubing combination. It is preferable to have several balls 36 to spread the outward force over an area of the packer, to prevent the balls punching a hole through the packer wall thickness, and to minimize distortion of the wall. The embodiment shown in Figures 2A and 2B has a total of fifty balls: five rows of ten balls around the circumference of the annular member 17.

Once the packer 40 is locked to the catch assembly, the retriever 1 can be withdrawn from the well, thus bringing the packer to the surface.

If the packer jams within the well such that the retriever cannot be withdrawn, a sufficient upward force should be applied to the mandrel 33 from the surface, to cause the shear pins 34 to shear. The sleeve 8 can then move downwards allowing the reaction to the outward force exerted by the balls 36 and the pre-load of the disc spring 42 to push the annular member 17 downwards, thus allowing the balls to move to the retracted position such that the packer is no longer locked to the catch assembly, The split stop ring 38 limits the downward travel of the sleeve 7 by abutting shoulder 20. The travel of the annular member t7 is limited by its flange 18 abutting the bail wire 41. This prevents the balls 36 riding up the back radius 43 of the camming surfaces 94 and accidently re-engaging the packer 40 or the tubing bore. The retriever can then be withdrawn from the well leaving the packer behind.

Claims

CLAIMS:

1. A device for retrieval of a smooth-bored element from a well bore, the device comprising a catch assembly mounted on a tubular member for engaging the element, the catch assembly comprising a sleeve slidable along the tubular member and including an emergency release means, the sleeve being urged by resilient means towards a collar, the emergency release means comprising the collar being secured to the tubular member by holding means adapted to yield at a predetermined stress, wherein the sleeve has an aperture there through and the catch assembly additionally comprises an annular member interposed between the sleeve and the tubular member1 the annular member having a camming surface thereon, and a cam element resting on said camming surface and extending through said aperture.

2. A device according to claim 1 wherein the sleeve has a plurality of apertures spaced circumferentially around the sleeve, the annular member has a cam surface corresponding to each aperture, and a cam element extends through each aperture in engagement with the associated cam surface.

3. A device according to claim 2 wherein the cam surfaces corresponding to the apertures are each parts of a common cam surface which is a surface of revolution of the annular member.

4. A device according to any preceding claim wherein the sleeve has a plurality of apertures spaced along its length, the annular member has a cam surface corresponding to each aperture, and a cam element extends through each aperture in engagement with the associated cam surface.

5. A device according to any preceding claim wherein the cam elements are balls.

6. A device according to any preceding claim wherein7 under normal conditions, the annular member is supported by the collar and wherein, upon yielding of the holding means, the collar is released from its normal position to permit the annular member to move downwardly relative to the sleeve thereby allowing the cam members to move radially inward to release the catch assembly from the element being retrieved.

7. A device according to any preceding claim wherein means are provided for limiting upward and/or downward movement of the apertured sleeve relative to the tubular member.

8. A device according to any preceding claim wherein means are provided for limiting upward and/or downward movement of the annular member relative to the tubular member.

9. A device according to any preceding claim comprising a milling tool, located above the catch assembly, and connected thereto by a connection permitting limited axial movement of the milling tool relative to the catch assembly

10. A device for retrieval of a smooth bored element from a well-bore, substantially as hereinbefore described with reference to the accompanying drawings.