Debris collection tool

1. A debris collection tool, comprising:

an inner mandrel;

a cover assembly disposed around the inner mandrel, the cover assembly including a plurality of covers spaced from one another along a length of the assembly creating a gap between adjacent covers; and

a carrier disposed around the inner mandrel and within the cover assembly and axially movable relative to the inner mandrel and to the cover assembly, the carrier including an annular piston and a plurality of magnet groups spaced from one another along a length of the carrier whereby, in an unactuated position of the tool, each of the plurality of magnet groups is under one of the plurality of covers, and in an actuated position, each of the plurality of magnet groups is aligned with a gap between covers;

wherein the inner mandrel includes a port providing a fluid path between a bore of the tool and the annular piston of the carrier;

wherein the debris collection tool is configured to be actuated in a wellbore.

2. The tool of claim 1 , wherein the carrier is movable within the cover assembly to shift the tool to the actuated position due to pressurized fluid being applied to the piston.

3. The tool of claim 1 , wherein the plurality of covers are spaced from one another by spacer pins.

4. The tool of claim 3 , wherein each of the plurality of magnet groups comprises a plurality of magnets radially disposed around an outer surface of the carrier and fixed thereto with a fastener.

5. The tool of claim 1 , wherein the cover assembly includes a particle shield constructed and arranged to separate the magnet groups from debris being magnetically collected.

6. The tool of claim 5 , further including a ring assembly disposed at a lower end of the carrier and constructed and arranged to absorb shock from pressure events acting upon the piston of the carrier.

7. The tool of claim 6 , wherein the ring assembly includes a first ring including an inwardly extending shearable arm that is acted upon by a lower face of the carrier and a wavy ring below the first ring constructed and arranged to flatten and reform in response to the pressure events.

8. The tool of claim 7 , wherein a predetermined fluid pressure on the annular piston causes the shearable arm to fail and the carrier to move axially downwards to the actuated position.

9. The tool of claim 1 , further including a reset assembly for returning the tool to the unactuated position.

10. The tool of claim 9 , wherein the reset assembly incudes a spring-loaded reset piston constructed and arranged to urge the carrier to the unactuated position at a predetermined time.

11. The tool of claim 10 , wherein the reset assembly further includes at least one retainer for maintaining the spring-loaded reset piston in a compressed position until the predetermined time.

12. The tool of claim 1 , wherein when the tool is in the unactuated position, each cover obscures the magnetic properties of a corresponding magnet of the plurality of magnet groups.

13. A method of operating a debris collection tool in a wellbore comprising:

running the tool into the wellbore on a string of tubulars to a predetermined depth, the tool including an inner mandrel and a carrier, the carrier disposed around the inner mandrel with spaced magnets mounted thereon and axially movable in a cover assembly, the cover assembly including a plurality of covers with a gap between adjacent covers; and

providing fluid pressure through a port in the inner mandrel to a piston surface formed on the carrier thereby causing the tool to move from a deactivated position wherein the magnets are covered, to an activated position wherein the magnets are exposed to the wellbore.

14. The method of claim 13 , wherein the piston surface is at an upper end of the carrier and the fluid pressure causes the carrier to move from a first position in the cover assembly to a second, lower position.

15. The method of claim 14 , wherein moving the tool to the activated position requires causing a shearable arm on a ring to fail, the ring disposed in the cover assembly.

16. The method of claim 15 , further including circulating fluid in the wellbore while the tool is in the activated position.

17. The method of claim 13 wherein moving the tool to the activated position is a second downhole operation taking place after a first operation, the first operation being a drilling operation.

18. A debris collection tool, comprising:

an inner mandrel;

a cover assembly disposed around the inner mandrel, the cover assembly including a plurality of covers spaced from one another along a length of the assembly such that a gap exists between adjacent covers;

a carrier disposed around the inner mandrel within the cover assembly and axially movable relative to the inner mandrel and to the cover assembly, the carrier including a plurality of magnet groups spaced from one another along a length of the carrier whereby, in an unactuated position of the tool, each of the plurality of magnet groups is under one of the plurality of covers, and in an actuated position, each of the plurality of magnet groups is aligned with a gap between covers; and

a reset assembly configured to return the tool to the unactuated position;

wherein the debris collection tool is configured to be actuated in a wellbore.

19. The tool of claim 18 , wherein the reset assembly incudes a spring-loaded reset piston constructed and arranged to urge the carrier to a position corresponding to the unactuated position of the tool at a predetermined time.

20. The tool of claim 19 , wherein the reset assembly further includes at least one retainer for maintaining the spring-loaded reset piston in a compressed position until the predetermined time.