Downhole seal

1. An expandable downhole seal comprising:

a sealing portion and a deflecting portion adapted to move axially relative to each other to effect radial deflection of the sealing portion, wherein at least one of the sealing portion and the deflecting portion comprises a swelling material, and at least one of the sealing and deflecting portions comprises a cam surface adapted to effect radial deflection of the sealing portion by overlapping of the sealing and deflecting portions in an axial direction upon relative axial movement of the sealing and deflecting portions; and

a support member adapted to support the sealing portion and deflecting portion.

2. The expandable downhole seal according to claim 1 , wherein the sealing portion defines a first sealing portion and the expandable downhole seal further comprises a second sealing portion, wherein relative axial movement of the first and second sealing portions and the deflecting portion effects radial deflection of at least the first sealing portion.

3. The expandable downhole seal according to claim 2 , wherein the first and second sealing portions are adapted to interengage.

4. The expandable downhole seal according to claim 3 , wherein the first and second sealing portions are adapted to overlap each other in an axial direction.

5. The expandable downhole seal according to claim 3 , wherein the first and second sealing portions are adapted to interleave each other.

6. The expandable downhole seal according to claim 5 , wherein the first and second sealing portions comprise complementary interleaving features.

7. The expandable downhole seal according to claim 2 , wherein at least one of the first and second sealing portions and the deflecting portion is fixed relative to the support member, wherein movement of the remaining portions produce relative axial movement.

8. The expandable downhole seal according to claim 2 , wherein the first and second sealing portions are located on axially opposed sides of the deflecting portion.

9. The expandable downhole seal according to claim 2 , wherein the first and second sealing portions are located on the same axial side of the deflecting member.

10. The expandable downhole seal according to claim 2 , wherein the sealing portion is adapted to directly engage an inner surface of a bore.

11. The expandable downhole seal according to claim 1 , wherein the sealing portion is adapted to indirectly engage an inner surface of a bore.

12. The expandable downhole seal according to claim 1 , wherein one of the sealing and deflecting portions is fixed relative to the support member and the other of the sealing and deflecting portions is axially moveable relative to the support member.

13. The expandable downhole seal according to claim 1 , wherein both the sealing and deflecting portions are axially moveable relative to the support member.

14. The expandable downhole seal according to claim 1 , wherein the deflecting portion comprises a cam surface adapted to radially deflect the sealing portion.

15. The expandable downhole seal according to claim 1 , wherein the sealing portion comprises a unitary component.

16. The expandable downhole seal according to claim 1 , wherein the sealing portion comprises a plurality of components which collectively define the sealing portion.

17. The expandable downhole seal according to claim 1 , wherein the seal portion comprises a swelling material.

18. The expandable downhole seal according to claim 1 , wherein the deflecting portion comprises a swelling material.

19. The expandable downhole seal according to claim 1 , wherein the downhole seal is adapted to be retrievable.

20. The expandable downhole seal according to claim 19 , wherein relative axial movement of the sealing and deflecting portions in a reverse direction effects radial displacement of the sealing portion in a direction to release or relax the seal, thus permitting the support member to be withdrawn or moved to an alternative location.

21. A method of establishing a seal within a wellbore, said method comprising:

providing an expandable downhole seal according to claim 1 ;

running said downhole seal into a well bore when in a first, unexpanded configuration;

reconfiguring the downhole seal into a second, expanded configuration by effecting relative axial movement of the sealing portion and the deflecting portion to effect radial deflection of the sealing portion; and

permitting the swelling material to swell.

22. The method according to claim 21 , further comprising running the downhole seal into a well bore filled with a material which does not initiate swelling of the swelling material.

23. The method according to claim 22 , further comprising displacing wellbore fluid with a swelling activator once the downhole seal has reached or is approaching a desired location within the wellbore.

24. An expandable downhole seal comprising:

a sealing portion and a deflecting portion adapted to move axially relative to each other to effect radial deflection of the sealing portion, wherein at least the deflecting portion comprises a swelling material, and at least one of the sealing and deflecting portions comprises a cam surface adapted to effect radial deflection of the sealing portion by overlapping of the sealing and deflecting portions in an axial direction upon relative axial movement of the sealing and deflecting portions; and

a support member adapted to support the sealing portion and deflecting portion.

25. The expandable downhole seal according to claim 24 , wherein the sealing and deflecting portions are adapted to interengage upon relative axial movement thereof, wherein said interengagement effects radial deflection of the sealing portion.

26. The expandable downhole seal according to claim 25 , wherein interengagement of the sealing and deflecting portions is achieved by overlapping of said portions in an axial direction.