Debris screen for a downhole tool

Abstract

A debris screen, sealingly and releasably latched to the top of a polished bore of a downhole tool for preventing the ingress of debris into the polished bore. Typically the debris screen is connected to a tieback receptacle of a liner hanger assembly. The debris screen is connected to a setting tool and is axially moveable on the setting tool permitting the setting tool to be stroked inside the liner hanger assembly during normal operations, such as cementing while retaining the debris screen at the top of the tieback receptacle at all times except during the final stages of retrieval. The debris screen has a tubular sleeve having a plurality of ports, covered by a wedge wire screen through which fluids can flow. Further, the latching mechanism has a plurality of ports to permit the flow of debris-free fluids from the wellbore into the annulus between the setting tool and the downhole tool.

Description

FIELD OF THE INVENTION

[0001] The invention relates to tools for running in and setting downhole tools and particularly to debris barriers for liner hanger running tools.

BACKGROUND OF THE INVENTION

[0002] Typically, liner hanger systems comprise a liner hanger from which a liner is suspended and which is lowered into a wellbore using a running tool connected at the end of a tubing string. The running tool is releasably connected to the liner hanger for retrieval once the liner has been cemented into place. A tieback receptacle having a polished bore is connected at a top end of the liner hanger to provide a surface against which seals can be applied in order to actuate other downhole equipment such as packers and the like.

[0003] During running in of the liner hanger and during normal operations required to set the slips of the liner hanger, debris may enter the annulus between the running tool and the tieback receptacle, particularly when the running tool is stroked up and down during normal setting operations. Debris which becomes trapped in the annulus may cause the running tool to become stuck, necessitating an expensive fishing expedition to retrieve it to surface. Further. debris may damage the polished bore as the running tool is stroked up and down, resulting in damage that affects the ability of seals to seal against the bore.

[0004] It is known in the industry to use a debris barrier to prevent debris from entering the polished bore of the tieback receptacle. Most debris barriers block the passage of debris and are fixed to the mandrel of the running tool such that as long as the running tool remains in the tieback receptacle, debris is excluded from entering the annulus, however, once the running tool is lifted, the annulus is exposed and debris may enter.

[0005] Other debris barriers are connected to the upper end of the tieback or similar receptacle and are axially moveable on the mandrel of the running tool to maintain the debris barrier at the top of the tieback receptacle during all normal operations, except retrieval.

[0006] U.S. Pat. No. 6,065,536 to Gudmestad teaches a debris barrier or junk bonnet comprising a pair of seals, one between a tubular member and the junk bonnet and the second between the junk bonnet and the polished bore. The junk bonnet slideably engages the outer wall of the tubular member and extends to the polished bore to provide a physical barrier against debris entering the polished bore. The junk bonnet is held at the top of the polished bore by dogs which engage a groove in the polished bore. The junk bonnet is restrained from rotation. As the tubular member is lifted to remove the attached running tool a shear pin is sheared and the dogs retract to release the junk bonnet and the running tool. With the exception of fluid which can flow past the seals, fluid flow through the junk bonnet is not contemplated. Further, should debris pack about the top of the junk bonnet there is a danger of a hydraulic lock forming which may restrict the axial motion of the running tool and the junk bonnet thereon.

[0007] U.S. Pat. No. 5,582,253 to Fraser teaches a plurality of rings and a collet system to latch a tool mandrel to a setting sleeve having a polished bore. One of said plurality of rings effectively covers the annular space between the mandrel and the sleeve providing a physical barrier to debris at the top of the polished bore. Fraser relies on a close tolerance between the ring and the mandrel to exclude debris while acting as a “leaky seal” to prevent pressure trapping on one side of the setting sleeve. Should debris pack about the top of the ring, the advantage of the leaky seal may be overcome and pressure trapping could occur. The apparatus of Fraser offers no alternate pressure relief.

[0008] Baker Oil Tools unit No. 4664 Liner Top Debris Barrier found in the Baker Oil Tools catalogue provides a screen filter held in a housing and mounted at a top of the polished bore using a shear screw. The polished bore is drilled and tapped to allow the shear screw connection and therefore, once the running tool is removed, remnants of the shear screw and the hole created in the polished bore can create an impediment for seals to seal properly against the bore. Further, seals inserted past the remaining protrusions may be damaged. A rupture disc is provided below the screen to relieve pressure should the screen become plugged.

[0009] U.S. Pat. No. 5,628,366 to Telfer teaches a junk bonnet that is hydraulically locked into position in the polished bore without reliance on mechanical fastening. The junk bonnet comprises a complex sealing arrangement having uphole and downhole seals which create an annular volume therebetween that is filled with hydraulic oil. The junk bonnet permits normal operational movements of the downhole assembly while retaining position at the top of the polished bore.

[0010] Clearly what is required is a simple, reusable debris barrier which permits the flow of fluids in an out of the annular space between the running tool and the tieback receptacle during stroking of the running tool in normal operation. The debris barrier must retain position at the top of the tieback receptacle until such time as the running tool is removed. Further, the debris barrier should prevent pressure locking due to blockage by debris and should not damage the integrity of the polished bore during insertion or removal therefrom.

SUMMARY OF THE INVENTION

[0011] In one aspect of the invention, a debris screen is provided preventing the ingress of debris to a tool annulus between a setting tool inserted into a downhole tool in a wellbore and a polished bore of the downhole tool, the setting tool being axially moveable within the polished bore. The debris screen comprises: a tubular sleeve formed over an exterior surface of the setting tool, and axially moveable thereon, defining a sleeve annulus therebetween, contiguous with the tool annulus, the sleeve having a plurality of ports formed therethrough for permitting fluid communication between the sleeve annulus and the wellbore; a screen formed over the tubular sleeve for preventing the passage of debris therethrough; a seal positioned at a top end of the tubular sleeve and extending between the tubular sleeve and the setting tool, the seal being sized so as to permit limited flow of fluid therethrough for preventing pressure locking, while blocking debris; and means for latching the tubular sleeve sealingly to a top of the polished bore and permitting fluid communication between the sleeve annulus and the tool annulus.

[0012] Preferably, the means for latching is a latching mechanism operable between the tubular sleeve and the polished bore wherein the latching mechanism releasably engages an annular groove at a top of the polished bore for retaining the tubular sleeve adjacent the top of the polished bore and permitting axial movement of the setting tool therein.

[0013] More preferably, the latching mechanism comprises a plurality of latch dogs housed within a latch dog housing, the latch dog housing being moveable between a downhole position and an uphole position. In the downhole position, the latch dog housing supports the latch dogs in an extended position wherein the latch dogs engage the groove on the top of the polished bore thus retaining the debris screen at the top of the polished bore. In the uphole position the latch dog housing permits the latch dogs to move to a retracted position wherein the latch dogs are retracted into the latch dog housing to release the latch dogs from the groove, thus permitting retrieval of the tool and the debris screen. Movement of the latch dog housing from the downhole position to the uphole position is accomplished by lifting the setting tool until a shoulder at the bottom of the setting tool mates with a shoulder on the latch dog housing. Lifting pressure applied to the setting tool overcomes shear screws, permitting the latch dog housing to move to the uphole position, the latch dogs to retract into the latch dog housing and retrieval of the debris screen and setting tool.

[0014] Alternatively, well suited for insertion into smaller diameter downhole tools, the latching mechanism is a collet system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a partial longitudinal sectional view of a debris screen of the present invention, showing a cutaway portion attached to the top of a tieback receptacle's polished bore;

[0016] FIG. 2a is a longitudinal sectional view of a latched latching mechanism according to FIG. 1 having a plurality of latch dogs acting between the debris screen and the polished bore, the latch dogs shown in a radially extended position;

[0017] FIG. 2b is a longitudinal sectional view of an un-latched latching mechanism according to FIG. 1 having a plurality of latch dogs acting between the debris screen and the polished bore, the latch dogs shown in a retracted position;

[0018] FIG. 3a is a sectional view of a portion of a collet system according to a second embodiment of the latching mechanism, showing a collet finger from an inside of the tubular housing;

[0019] FIG. 3b is a sectional view of the collet system according to FIG. 3a, showing an inside of a collet retainer, having a plurality of ports formed at a lower edge;

[0020] FIG. 4a is a longitudinal sectional view of a latched latching mechanism according to FIGS. 3a-3b, having a collet system acting between the debris screen and the polished bore, the collet shown in a downhole engaged position; and

[0021] FIG. 4b is a longitudinal sectional view of an unlatched latching mechanism according to FIGS. 3a-3b having a collet system acting between the debris screen and the polished bore, the collet shown in an uphole non-engaged position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] Having reference to FIGS. 1-3, a debris screen 10 of the present invention is shown. The debris screen 10 comprises a tubular sleeve 11 which is positioned about an outer surface of a setting tool 12 forming a sleeve annulus 13 therebetween. The tubular sleeve 11 is releasably latched to a top end 14 of a downhole tool having a polished bore 15, such as a tieback receptacle attached to the top of a liner hanger assembly, to prevent the ingress of debris to a tool annulus 16 between the setting tool 12 and the polished bore 15. The tubular sleeve 11 has a plurality of ports 17 formed therethrough to provide fluid communication between the wellbore and the sleeve annulus 13, the sleeve annulus 13 being contiguous with the tool annulus 16. Means are provided for flow A of fluids between the sleeve annulus 13 and the tool annulus 16.

[0023] The setting tool 12 is axially moveable through the debris screen 10. As the setting tool 12 is stroked up and down through the tubular sleeve 11 and within the polished bore 15, such as when reciprocating the setting tool 12 to ensure that the setting tool is released from the liner hanger assembly prior to cementing, fluid may be caused to flow A in and out of the ports 17. A tubular wire screen 18, such as a wedge wire screen available from Variperm Canada Limited, Calgary, Alberta, Canada, is affixed over the tubular sleeve 11 to prevent debris from entering the ports 17 with the fluid.

[0024] Means, such as a latching mechanism 30, maintains the debris screen 10 at the top 14 of the polished bore 15 except during the final stages of retrieval of the setting tool 12 from the polished bore 15. Thus, the polished bore 15 is protected from damage resulting from debris being scratched along the polished bore during the axial movement of the setting tool 12 therein during routine operations.

[0025] Preferably, as shown in FIG. 1, an upper end 19 of the tubular sleeve 11 is connected to a top sub 20. The top sub 20 is formed having a lower portion 22, an upper cap portion 22 and a pipe wiper 23 sandwiched therebetween. The pipe wiper 23 acts as a “leaky seal” at the upper end 20 of the tubular sleeve 11, preventing debris from entering the annulus 13 between the tubular sleeve 11 and the setting tool 12, while allowing limited flow of fluids therethrough to prevent pressure lock should the screen 18 become plugged with debris.

[0026] In one embodiment of the invention, as shown in FIGS. 1, 2a-2b, the latching mechanism 30 is located adjacent a lower end 33 of the tubular sleeve 11. The latching mechanism 30 comprises a plurality of latch dogs 31 which extend radially outward from a corresponding plurality of openings 32 at the lower end 33 of the tubular sleeve 11. The latch dogs 21 engage an annular groove 34 at the top 14 of the polished bore 15. The latch dogs 31 are held in a radially extending position by a latch dog housing 35, positioned adjacent the lower end 33 of the tubular sleeve 11 in the annular space 13 between the tubular sleeve 11 and the setting tool 12. The latch dog housing 35 is axially moveable therein from a first downhole position, shown in FIG. 2a, in which the latch dogs 31 are supported in the extended position, to an uphole position, shown in FIG. 2b, wherein the latch dogs 31 are permitted to retract from the annular groove 34. Once the latch dogs 31 retract, the lower end 33 of the tubular sleeve 11 is released from the polished bore 15.

[0027] In the downhole position, as shown in FIG. 2a, the latch dog housing 35 extends below the lower end 33 of the tubular sleeve 11 into the annular space 16 between the setting tool 12 and the polished bore 15. The latch dog housing 25 is releasably retained in the downhole position by at least one shear screw 36 connected between the tubular sleeve 11 and the latch dog housing 25. A plurality of shear screws 36 may be used to adjust a retrieval force required to release the latch dog housing 35.

[0028] As shown in FIG. 2b, the setting tool 12 is-lifted for retrieval from the wellbore and engages the latch dog housing 25 to move the latch dog housing 25 to the uphole position. An uphole facing shoulder 40, preferably adjacent a bottom end (not shown) of the setting tool 12 mates with a downhole facing shoulder 41 at a bottom end 42 of the latch dog housing 25. Lifting pressure is applied to the setting tool 12 and through the shoulder 40 to the latch dog housing 25, sufficient to overcome the shear screws 36. The latch dog housing 25 moves axially to the uphole position permitting the latch dogs 21 to retract into an annular groove 43 on the latch dog housing 25, releasing the latching mechanism 30 and the debris screen 10 from the top of the polished bore 15. The setting tool and debris screen 10 are then retrieved to surface after setting a packer (not shown) if included in the liner hanger assembly string.

[0029] Preferably, a plurality of slots or ports 39 are formed at the bottom end 42 of the latch dog housing 25 as the means provided to permit the fluid flow A to and from the wellbore, through the sleeve annulus 13 and the tool annulus 16.

[0030] In a second embodiment of the invention, as shown in FIGS. 3a-3b and 4a-4b, the latching mechanism 30 is a collet system 50, particularly well suited to smaller diameter tools having a smaller tolerance between the setting tool 12 and the polished bore 15. The polished bore 15 or tieback receptacle is the same as set forth in the previous embodiment in FIGS. 2a-2b.

[0031] A plurality of downwardly depending collet fingers 51, are formed adjacent the lower end 33 of the tubular sleeve 11. The collet fingers 51 engage the same form of annular groove 34, as shown in FIG. 3b at the top 14 of the polished bore 15.

[0032] As shown in FIG. 4a, a collet retainer 52 is positioned in the annular space 13 between the tubular sleeve 11 and the setting tool 12 and is releasably connected to the tubular sleeve 11 in a downhole position for supporting the collet fingers 51 in an engaged position in the annular groove 34 at the top 14 of the polished bore 15. With reference to FIG. 4b, the collet retainer 52 is axially moveable for enabling alternate support and release of the collet fingers 51. A profiled outer surface 56, at the lower end 55 of the collet retainer 52, permits the collet fingers 51 to be moved out of the annular groove 34. Once the collet fingers 51 are released, the tubular sleeve 11 can be removed from the polished bore 15.

[0033] As shown in FIG. 4a, the collet retainer 52, in the downhole position, extends below the lower end 33 of the tubular sleeve 11 into the annular space 16 between the setting tool 12 and the polished bore 15. The collet retainer 52 is releasably retained in the downhole position by at least one shear screw 53 connected between the tubular sleeve 11 and the collet retainer 52. A plurality of shear screws 53 may be used to adjust a retrieval force required to release the collet retainer 52.

[0034] Best seen in FIG. 3b, a plurality of ports 54 are formed at a bottom end 55 of the collet retainer 52 for permitting the flow A of fluids therethrough.

[0035] As shown in FIG. 4b, and described in the previous embodiment, the setting tool 12 is lifted for retrieval from the wellbore. The uphole facing shoulder 40 adjacent the bottom end of the setting tool 12 mates with a downhole facing shoulder 54 at a bottom end 55 of the collet retainer 52. Lifting pressure is applied to the setting tool 12 and through the shoulder 40, sufficient to overcome the shear screws 53. The collet retainer 52 moves axially to the uphole position permitting the collet fingers 51 to retract into the profiled outer surface 56 of the collet retainer 52, releasing the debris screen 10 from the top of the polished bore 15. The setting tool and debris screen 10 are then retrieved to surface after setting a packer (not shown) is included in the liner hanger assembly string.

Claims

1. A debris screen preventing the ingress of debris to a tool annulus between a setting tool inserted into a bore of a downhole tool in a wellbore, the setting tool being axially moveable within the bore, the debris screen comprising:

a tubular sleeve positioned about an exterior surface of the setting tool, and axially moveable thereon and defining a sleeve annulus therebetween, the sleeve having a plurality of ports formed therethrough for permitting fluid communication between the sleeve annulus and the wellbore;

a screen formed over the tubular sleeve for preventing the passage of debris therethrough;

a seal positioned at a top end of the tubular sleeve and extending between the tubular sleeve and the setting tool, the seal permitting limited fluid communication therethrough for preventing pressure locking while blocking debris; and

means for latching the tubular sleeve sealingly to a top of the bore and permitting fluid communication between the sleeve annulus and the tool annulus.

2. The debris screen as described in claim 1 wherein the means for latching the tubular sleeve sealingly to the top of the bore comprises:

a latching mechanism operable between the tubular sleeve and the bore wherein the latching mechanism is adapted for releasably engaging an annular groove at a top of the bore for retaining the tubular sleeve adjacent the top of the bore.

3. The debris screen as described in claim 2 wherein the latching mechanism further comprises:

a plurality of latch dogs, extendable radially outward through a plurality of corresponding openings at a lower end of the tubular sleeve, for engaging the annular groove at the top of the bore, the latch dogs being moveable between a radially extended position and a retracted position;

a latch dog housing, positioned in the tool annulus and releasably connected to the tubular sleeve in a downhole position for supporting the latch dogs in the extended position and being axially moveable thereupon to an uphole position following release from the tubular sleeve, to permit the latch dogs to move to the retracted position thereby releasing the tubular sleeve from the bore; and

ports formed in the latch dog housing for permitting fluid communication between the sleeve annulus and the tool annulus.

4. The debris screen as described in claim 3 further comprising a downwardly depending shoulder at a lower end of the latch dog housing wherein when the setting tool is lifted to exit the bore, the setting tool engages the shoulder and lifting pressure is applied to the latch dog housing sufficient to overcome the releasable connection and move the latch dog housing to the uphole position permitting the latch dogs to move to the retracted position and releasing the tubular sleeve from the bore.

5. The debris screen as described in claim 4 wherein the latch dog housing is releasably connected to the tubular sleeve by at least one shear screw.

6. The debris screen as described in claim 2 wherein the latching mechanism further comprises a collet system.

7. The debris screen as described in claim 6 wherein the collet system comprises:

a plurality of downwardly depending collet fingers, formed at a lower end of the tubular sleeve, for engaging the annular groove at the top of the bore;

a collet retainer positioned in the tool annulus and releasably connected to the tubular sleeve in a downhole position for supporting the collet fingers in the annular groove at the top of the bore, the collet retainer being axially moveable thereupon to an uphole position following release from the tubular sleeve, to permit the collet fingers to be released from the annular groove thereby releasing the tubular sleeve from the bore; and

ports formed in the collet retainer for permitting fluid communication between the sleeve annulus and the tool annulus.

8. The debris screen as described in claim 7 further comprising a downwardly depending shoulder at a lower end of the collet retainer wherein when the setting tool is lifted to exit the bore, the setting tool engages the shoulder and lifting pressure is applied to the collet retainer sufficient to overcome the releasable connection and move the collet retainer to the uphole position, forcing the collet fingers out of the annular groove and releasing the tubular sleeve from the bore.

9. The debris screen as described in claim 1 wherein the screen is a wedge wire screen.

10. The debris screen as described in claim 3 wherein the screen is a wedge wire screen.

11. The debris screen as described in claim 8 wherein the screen is a wedge wire screen.

12. The debris screen as described in claim 1 wherein the downhole tool is a liner hanger assembly.

13. The debris screen as described in claim 3 wherein the downhole tool is a liner hanger assembly.

14. The debris screen as described in claim 8 wherein the downhole tool is a liner hanger assembly.

15. A debris screen preventing the ingress of debris to an annulus between a setting tool inserted into a bore of a liner hanger assembly, the setting tool being axially moveable within the bore, the debris screen comprising:

a tubular sleeve positioned about an exterior surface of the setting tool, and axially moveable thereon and defining a sleeve annulus therebetween, the sleeve having a plurality of ports formed therethrough for permitting fluid communication between the sleeve annulus and the wellbore;

a screen formed over the tubular sleeve for preventing the passage of debris therethrough;

a seal positioned at a top end of the tubular sleeve and extending between the tubular sleeve and the setting tool, the seal permitting limited fluid communication therethrough for preventing pressure locking while blocking debris; and

means for latching the tubular sleeve sealingly to a top of the bore and permitting fluid communication between the sleeve annulus and the tool annulus.

16. The debris screen as described in claim 15 wherein the means for latching the tubular sleeve sealingly to the top of the bore is a latching mechanism operable between the tubular sleeve and the bore and wherein the latching mechanism is adapted for releasably engaging an annular groove at a top of the bore for retaining the tubular sleeve adjacent the top of the bore, the latching mechanism comprising:

a plurality of latch dogs, extendable radially outward through a plurality of corresponding openings at a lower end of the tubular sleeve, for engaging the annular groove at the top of the bore, the latch dogs being moveable between a radially extended position and a retracted position;

a latch dog housing, positioned in the tool annulus and releasably connected to the tubular sleeve in a downhole position for supporting the latch dogs in the extended position and being axially moveable thereupon to an uphole position following release from the tubular sleeve, to permit the latch dogs to move to the retracted position thereby releasing the tubular sleeve from the bore:

ports formed in the latch dog housing for permitting fluid communication between the sleeve annulus and the tool annulus; and

a downwardly depending shoulder at a lower end of the latch dog housing wherein when the setting tool is lifted to exit the bore, the setting tool engages the shoulder and lifting pressure is applied to the latch dog housing sufficient to overcome the releasable connection and move the latch dog housing to the uphole position permitting the latch dogs to move to the retracted position and releasing the tubular sleeve from the bore.

17. The debris screen as described in claim 16 wherein the latching mechanism is a collet system comprising:

a plurality of downwardly depending collet fingers, formed at a lower end of the tubular sleeve, for engaging the annular groove at the top of the bore;

a collet retainer positioned in the tool annulus and releasably connected to the tubular sleeve in a downhole position for supporting the collet fingers in the annular groove at the top of the bore, the collet retainer being axially moveable thereupon to an uphole position following release from the tubular sleeve, to permit the collet fingers to be released from the annular groove thereby releasing the tubular sleeve from the bore; and

ports formed in the collet retainer for permitting fluid communication between the sleeve annulus and the tool annulus; and

a downwardly depending shoulder at a lower end of the collet retainer wherein when the setting tool is lifted to exit the bore, the setting tool engages the shoulder and lifting pressure is applied to the collet retainer sufficient to overcome the releasable connection and move the collet retainer to the uphole position, forcing the collet fingers out of the annular groove and releasing the tubular sleeve from the bore.