Controllable magneto-rheological fluid-based dampers for drilling

1. A damping apparatus for a drillstring comprising a bit, said damping apparatus comprising a damping mechanism comprising magnetorheological fluid and means for generating an electromagnetic field affecting said magnetorheological fluid in response to changing ambient conditions encountered by the bit.

2. The damping apparatus of claim 1 wherein said damping mechanism dampens longitudinal vibrations.

3. The damping apparatus of claim 2 wherein said damping mechanism additionally dampens rotational vibrations.

4. The damping apparatus of claim 3 wherein said damping apparatus comprises two damping mechanisms in series.

5. The damping apparatus of claim 1 wherein said damping mechanism dampens rotational vibrations.

6. The damping apparatus of claim 1 wherein said magnetorheological fluid is housed in a chamber comprising an orifice between two sections of said chamber and wherein said generating means comprises an electromagnetic coil proximate said orifice.

7. A damping apparatus for a drillstring comprising a bit, said damping apparatus comprising a damping mechanism comprising means providing frictional properties that are alterable while the drillstring is in use, and means for controlling the frictional properties based upon changing ambient conditions encountered by the bit.

8. The damping apparatus of claim 7 wherein said damping mechanism dampens longitudinal vibrations.

9. The damping apparatus of claim 8 wherein said damping mechanism additionally dampens rotational vibrations.

10. The damping apparatus of claim 9 wherein said damping mechanism comprises two damping mechanisms in series.

11. The damping apparatus of claim 7 wherein said damping mechanism dampens rotational vibrations.

12. The damping apparatus of claim 7 wherein said means providing frictional properties comprises magnetorheological fluid.

13. The damping apparatus of claim 12 wherein said magnetorheological fluid is housed in a chamber comprising an orifice between two sections of said chamber and wherein said controlling means comprises an electromagnetic coil proximate said orifice.

14. A damping method for a drillstring comprising a bit, the method comprising the steps of:

providing to the drillstring a damping mechanism comprising magnetorheological fluid; and

generating an electromagnetic field affecting the magnetorheological fluid in response to changing ambient conditions encountered by the bit.

15. The damping method of claim 14 wherein the method dampens longitudinal vibrations.

16. The damping method of claim 15 wherein the method additionally dampens rotational vibrations.

17. The damping method of claim 16 wherein the providing step comprises providing two damping mechanisms in series and the generating step comprises generating one or more electromagnetic fields affecting the magnetorheological fluid in both damping mechanisms.

18. The damping method of claim 14 wherein the method dampens rotational vibrations.

19. The damping method of claim 14 wherein the providing step comprises housing the magnetorheological fluid in a chamber comprising an orifice between two sections of the chamber and wherein the generating step comprises employing an electromagnetic coil proximate the orifice.

20. A damping method for a drillstring comprising a bit, the method comprising the steps of:

providing a damping mechanism comprising means providing frictional properties that are alterable while the drillstring is in use; and

controlling the frictional properties based upon changing ambient conditions encountered by the bit.

21. The damping method of claim 20 wherein the method dampens longitudinal vibrations.

22. The damping method of claim 21 wherein the method additionally dampens rotational vibrations.

23. The damping method of claim 22 wherein the providing step comprises providing two damping mechanisms in series and the generating step comprises generating one or more electromagnetic fields affecting the magnetorheological fluid in both damping mechanisms.

24. The damping method of claim 20 wherein the method dampens rotational vibrations.

25. The damping method of claim 20 wherein in the providing step the means providing frictional properties comprises magnetorheological fluid.

26. The damping method of claim 25 wherein the providing step comprises housing the magnetorheological fluid in a chamber comprising an orifice between two sections of the chamber and wherein the controlling step comprises employing an electromagnetic coil proximate the orifice.