Vibration isolating coupler for reducing high frequency torsional vibrations in a drill string

1. A vibration isolating coupler for isolating torsional vibration in a drill string comprising:

a first coupler portion including a first annular wall having an external surface and an internal surface defining a first central bore portion;

a second coupler portion disposed within the first central bore portion, the second coupler portion including a second annular wall having an external surface section and an internal surface section defining a second central bore portion; and

a plurality of connecting elements extending from the internal surface of the first annular wall through the second annular wall across the second central bore portion and connecting with the internal surface section of the second annular wall, wherein the vibration isolating coupler isolates torsional vibration by elastic bending of the plurality of connecting elements.

2. The vibration isolating coupler according to claim 1 , wherein the second coupler portion includes a plurality of axially spaced openings extending from the external surface section of second annular wall through the second annular wall to the internal surface section of second annular wall and the plurality of axially spaced openings include a first plurality of axially spaced openings, a second plurality of axially spaced openings circumferentially offset relative to the first plurality of axially spaced openings, a third plurality of axially spaced openings circumferentially offset from the first plurality of axially spaced openings and the second plurality of axially spaced openings.

3. The vibration isolating coupler according to claim 1 , further comprising: a conductor extending through at least one of the plurality of connecting elements.

4. The vibration isolating coupler according to claim 1 , further comprising: a seal arranged between the first coupler portion and the second coupler portion.

5. The vibration isolating coupler according to claim 1 , wherein the first coupler portion includes a first tubular portion, and the second coupler portion includes a second tubular portion, the first tubular portion, the second tubular portion and the plurality of connecting elements are formed from the same material.

6. The vibration isolating coupler according to claim 1 , wherein the first coupler portion includes a first tubular portion and the second coupler portion includes a second tubular portion, the first tubular portion and the second tubular portion are formed from a first material, and the plurality of connecting elements are formed from a second material that is different to the first material.

7. The vibration isolating coupler according to claim 1 , wherein the plurality of connecting elements are integrally formed with the first coupler portion and the second coupler portion.

8. The vibration isolating coupler according to claim 1 , wherein the second coupler portion is concentric with the first coupler portion.

9. The vibration isolating coupler according to claim 1 , wherein the first annular wall includes a first end and a second end, and the second annular wall includes a first end portion and a second end portion, the first end portion of the second annular wall supporting a first connector and the second end of the first annular wall supporting a second connector, wherein the first connector comprises one of a first box thread connector and a first pin thread connector and the second connector comprises one of a second box thread connector and a second pin thread connector.

10. The vibration isolating coupler according to claim 1 , wherein the plurality of connecting elements are connected to at least one of the first coupler portion and the second coupler portion by one of welding, soldering, screwing, and clamping.

11. A method of isolating torsional vibrations from one portion of a drill string connected to another portion of the drill string through a vibration isolating coupler having a first coupler portion connected to a second coupler portion through a plurality of connecting elements, the method comprising:

introducing the torsional vibrations into the first coupler portion;

transferring the torsional vibrations into the plurality of connecting elements extending from an internal surface section of the second coupler portion, through an annular wall of the second coupler portion to an internal surface of the first coupler portion; and

isolating the torsional vibrations by elastic bending of the plurality of connecting elements.

12. The method of claim 11 , wherein isolating torsional vibrations includes elastically bending the plurality of connecting elements in a direction perpendicular to a longitudinal axis of the vibration isolating coupler.

13. The method of claim 11 , further comprising: limiting torsion angle of the second coupler portion relative to the first coupler portion through at least one torsional end stop.

14. The method of claim 11 , further comprising: passing drilling fluid through the vibration isolating coupler.

15. A vibration isolating coupler for isolating torsional vibration in a drill string comprising:

a first coupler portion including a first annular wall having an external surface and an internal surface defining a first central bore portion;

a second coupler portion disposed within the first central bore portion, the second coupler portion including a second annular wall having an external surface section and an internal surface section defining a second central bore portion; and

a plurality of connecting elements extending from the internal surface of the first annular wall through the second annular wall across the second central bore portion and connecting with the internal surface section of the second annular wall, wherein the second coupler portion includes a plurality of axially spaced openings extending from the external surface section of the second annular wall through the second annular wall to the internal surface section of the second annular wall.

16. The vibration isolating coupler according to claim 15 , wherein the vibration isolating coupler isolates torsional vibration by deformation of the plurality of connecting elements.

17. The vibration isolating coupler according to claim 15 , further comprising: a conductor extending through at least one of the plurality of connecting elements.

18. The vibration isolating coupler according to claim 15 , further comprising: a seal arranged between the first coupler portion and the second coupler portion.

19. The vibration isolating coupler according to claim 15 , wherein the first coupler portion includes a first tubular portion and the second coupler portion includes a second tubular portion, the first tubular portion, the second tubular portion, and the plurality of connecting elements being formed from the same material.

20. The vibration isolating coupler according to claim 15 , wherein the plurality of connecting elements are integrally formed with the first coupler portion and the second coupler portion.

21. The vibration isolating coupler according to claim 15 wherein the first annular wall includes a first end and a second end, and the second annular wall includes a first end portion and a second end portion, the first end portion of the second annular wall supporting a first connector and the second end of the first annular wall supporting a second connector, wherein the first connector comprises one of a first box thread connector and a first pin thread connector and the second connector comprises one of a second box thread connector and a second pin thread connector.

22. A vibration isolating coupler for isolating torsional vibration in a drill string comprising:

a first coupler portion including a first annular wall having an external surface and an internal surface defining a first central bore portion;

a second coupler portion disposed within the first central bore portion, the second coupler portion including a second annular wall having an external surface section and an internal surface section defining a second central bore portion; and

a plurality of connecting elements extending from the internal surface of the first annular wall through the second annular wall across the second central bore portion and connecting with the internal surface section of the second annular wall, wherein the vibration isolating coupler includes a torsion spring constant, the torsion spring constant defining a torsional resonance frequency of less than 100 Hz thereby isolating vibrations between the first and the second coupler portion with a frequency higher than about the torsional resonance frequency.

23. The vibration isolating coupler according to claim 22 , wherein the vibration isolating coupler isolates vibration by deformation of the plurality of connecting elements.

24. The vibration isolating coupler according to claim 22 , wherein the second coupler portion includes a plurality of circumferentially spaced openings extending from the external surface section of the second annular wall through the second annular wall to the internal surface section of the second annular wall.

25. The vibration isolating coupler according to claim 22 , further comprising: a conductor extending through at least one of the plurality of connecting elements.

26. The vibration isolating coupler according to claim 22 , further comprising: a seal arranged between the first coupler portion and the second coupler portion.

27. The vibration isolating coupler according to claim 22 , wherein the first coupler portion includes a first tubular portion, and the second coupler portion includes a second tubular portion, the first tubular portion, the second tubular portion and the plurality of connecting elements are formed from the same material.

28. The vibration isolating coupler according to claim 22 , wherein the plurality of connecting elements are integrally formed with the first coupler portion and the second coupler portion.

29. The vibration isolating coupler according to claim 22 , wherein the first annular wall includes a first end and a second end, and the second annular wall includes a first end portion and a second end portion, the first end portion of the second annular wall supporting a first connector and the second end of the first annular wall supporting a second connector, wherein the first connector comprises one of a first box thread connector and a first pin thread connector and the second connector comprises one of a second box thread connector and a second pin thread connector.

30. A method of isolating torsional vibrations from one portion of a drill string connected to another portion of the drill string through a vibration isolating coupler having a first coupler portion connected to a second coupler portion through a plurality of connecting elements, the method comprising:

selecting a torsional stiffness of the vibration isolating coupler to having a torsional resonance frequency of the vibration isolating coupler less than 100 Hz; and

selecting the moment of inertia of a drill string section positioned one of above or below the vibration isolating coupler to a moment of inertia having the torsional resonance frequency of the vibration isolating coupler;

introducing the torsional vibrations into one of the first coupler portion and the second coupler portion;

transferring the torsional vibrations into the plurality of connecting elements extending from an internal surface section of the second coupler portion, through an annular wall of the second coupler portion to an internal surface of the first coupler portion; and

isolating torsional vibrations between the first and the second coupler portion having a frequency higher than about the torsional resonance frequency.