Radial flow valve and method

1. A radial flow valve for use in a subterranean well, comprising:

a plurality of flow openings;

a first piston and a second piston, said first and second pistons being independently actuable relative to one another; and

a sleeve operatively coupled to said second piston, said sleeve adapted to be positioned so as to cover said plurality of flow openings;

wherein said second piston is releasably coupled to said sleeve such that said sleeve is moved in an uphole direction when said second piston moves in the uphole direction;

wherein said second piston is secured in its initial position until said first piston is moved from its initial position in a direction away from said second piston.

2. The valve of claim 1 , wherein said valve is adapted to be used in a subterranean well having an upper zone pressure and a lower zone pressure, and wherein said first piston is adapted to be moved from its initial position to its final position by increasing a pressure within the valve to a value that is greater than the upper zone pressure.

3. The valve of claim 2 , wherein said second piston is adapted to be moved from its initial position to its final position by reducing said pressure within said valve to a value that is approximately the same as the lower zone pressure or less.

4. The valve of claim 1 , wherein movement of said coupled second piston and sleeve toward said first piston operates to uncover said flow openings.

5. The valve of claim 1 , wherein said first piston is releasably coupled to a component of said valve by a plurality of shear pins.

6. The valve of claim 5 , wherein said component defines a portion of an outer surface of the valve.

7. The valve of claim 1 , wherein said valve is adapted to be used in a subterranean well having an upper zone pressure and a lower zone pressure, wherein said first piston is movable in response to a pressure within said valve being greater than the upper zone pressure, and wherein said second piston is movable when a pressure within said valve is reduced to approximately the lower zone pressure or less.

8. The valve of claim 1 , wherein said sleeve has a plurality of openings that are adapted to be substantially aligned with the flow openings in the valve to thereby permit fluid flow therethrough.

9. The valve of claim 1 , wherein said sleeve has at least one profile formed in an interior surface of the sleeve that is adapted to be engaged by a wireline tool.

10. The valve of claim 1 , wherein said sleeve is operatively coupled to the second piston by a plurality of shear pins.

11. The valve of claim 1 , further comprising a spring positioned proximate said second piston, said spring adapted to apply a biasing spring force to said second piston so as to urge said second piston to move toward its final position.

12. The valve of claim 1 , further comprising a plurality of actuatable members that engage said first and second pistons when said first and second pistons are in their initial positions and thereby secure said second piston in its initial position.

13. The valve of claim 12 , wherein said plurality of actuatable members comprises a plurality of spring actuated dogs.

14. A radial flow valve adapted to be used in a subterranean well having an upper zone pressure and a lower zone pressure, comprising:

a plurality of flow openings;

a first piston and a second piston, said first and second pistons being independently actuable relative to one another, the first piston being releasably coupled to a component of said valve, wherein said first piston is movable when a pressure within said valve is greater than the upper zone pressure, and wherein said second piston is movable when a pressure within said valve is reduced to approximately the lower zone pressure or less; and

a sleeve releasably coupled to said second piston, said sleeve adapted to be positioned so as to cover said plurality of flow openings;

wherein said second piston is releasably coupled to said sleeve such that said sleeve is moved in an uphole direction when said second piston moves in the uphole direction;

wherein said second piston is secured in its initial position until said first piston is moved from its initial position in a direction away from said second piston.

15. The valve of claim 14 , wherein said first piston moving upward releases at least one actuatable dog holding said second piston stationary.

16. The valve of claim 15 , wherein said second piston is adapted to be moved from its initial position to its final position when the pressure within said valve is reduced to a value that is approximately equal to or less than the lower zone pressure.

17. The valve of claim 14 , wherein the first piston is releasably coupled to said component by a plurality of shear pins.

18. The valve of claim 17 , wherein said second piston is secured in its initial position until said first piston is moved from its initial position.

19. The valve of claim 14 , wherein said sleeve has a plurality of openings that are adapted to be substantially aligned with the flow openings in the valve to thereby permit fluid flow therethrough.

20. The valve of claim 14 , wherein said sleeve has at least one profile formed in an interior surface of the sleeve that is adapted to be engaged by a wireline tool.

21. The valve of claim 14 , further comprising a spring positioned proximate said second piston, said spring applying a biasing spring force to said second piston so as to urge said second piston toward its final position.

22. The valve of claim 14 , further comprising a plurality of actuatable members that engage said first and second pistons when said first and second positions are in their initial positions and thereby secure said second piston in its initial position.

23. A method, comprising:

positioning a radial flow valve in a subterranean well bore having an upper zone pressure and a lower zone pressure;

increasing a pressure within the valve to a pressure above the upper zone pressure to release a first piston within the valve;

after releasing the first piston, reducing the pressure within the valve to a value that is approximately equal to or less than the lower zone pressure to thereby permit a second piston within the valve to move and thereby permit fluid flow through the valve;

wherein said second piston moves toward said first piston and thereby moves a sleeve that is releasably coupled to said second piston, wherein movement of said sleeve toward said first piston uncovers a plurality of flow openings in the valve;

inserting a wireline tool to engage a profile formed in an interior surface of the sleeve;

applying a mechanical force to the sleeve to disengage the sleeve from the second piston; and

moving said disengaged sleeve to a first position where a plurality of openings in the sleeve are substantially aligned with the plurality of flow openings in the valve.

24. The method of claim 23 , wherein increasing a pressure within the valve to a value above the upper zone pressure to release the first piston within the valve shears a shear pin connection between the first piston and a component of the valve.

25. The method of claim 23 , further comprising moving said disengaged sleeve from said first position to a second position wherein said sleeve blocks said flow openings in the valve.

26. The method of claim 23 , further comprising producing a fluid from said well through said valve.