Downhole vibration assembly and method of using same

1. A vibration assembly for a downhole tool positionable in a subterranean formation, the vibration assembly comprising:

a vibration race positioned in the downhole tool, the vibration race having a non-planar engagement surface comprising a plurality of valleys, a plurality of ramps, and a plurality of flat peaks, wherein each flat peak is positioned between a pair of the plurality of ramps, each valley has a first radius, and each ramp has a second radius that is different from the first radius;

an additional race positioned in the downhole tool a distance from the vibration race, the additional race having another engagement surface facing the non-planar engagement surface of the vibration race; and

a cage positioned between the vibration race and the additional race; and

rollers rollably engageable with the non-planar engagement surface and the another engagement surface to vary the distance between the vibration race and the additional race whereby axial movement is provided in the downhole tool.

2. The vibration assembly of claim 1 , wherein the additional race is a bearing race and wherein the another engagement surface is a planar engagement surface.

3. The vibration assembly of claim 1 , wherein the additional race is another vibration race having another non-planar surface.

4. The vibration assembly of claim 3 , wherein the additional race is identical to the vibration race.

5. The vibration assembly of claim 1 , wherein the rollers are one of cylindrical, spherical, and frusta-conical.

6. The vibration assembly of claim 1 , wherein the non-planar engagement surface is a wavy surface extending radially about the vibration race.

7. The vibration assembly of claim 1 , wherein the non-planar engagement surface is a circular channel extending into an inner surface of the vibration race, the circular channel having a non-smooth surface.

8. The vibration assembly of claim 1 , wherein the ramps and the valleys of the non-planar engagement surface are in one of a smooth curved configuration, a sinusoidal configuration, a stepped configuration, a ramped configuration, a symmetric configuration, an asymmetric configuration, and combinations thereof.

9. The vibration assembly of claim 1 , wherein the vibration race and the additional race have connector holes to receive connectors therethrough for connection to the downhole tool.

10. The vibration assembly of claim 1 , further comprising a cage positioned between the vibration race and the additional race, the rollers being positionable in the cage.

11. The vibration assembly of claim 10 , wherein:

the vibration race, the additional race, and the cage are ring-shaped members with a passage extending therethrough; and

the cage has roller holes to receive the rollers therein.

12. A downhole tool positionable in a subterranean formation, the downhole tool comprising:

a conveyance; and

a bottomhole assembly supported by the conveyance, the bottomhole assembly comprising a housing and a vibration assembly, the vibration assembly comprising:

a vibration race positioned in the downhole tool, the vibration race having a non-planar engagement surface comprising a plurality of valleys, a plurality of ramps, and a plurality of flat peaks, wherein each flat peak is positioned between a pair of the plurality of ramps, each valley having has a first radius and each ramp has a second radius that is different from the first radius;

an additional race positioned in the downhole tool a distance from the vibration race, the additional race having another engagement surface facing the non-planar engagement surface of the vibration race; and

rollers rollably engageable with the non-planar engagement surface and the another engagement surface to vary the distance between the vibration race and the additional race whereby axial movement is provided in the downhole tool.

13. The downhole tool of claim 12 , wherein the conveyance is a drill string and the bottomhole assembly comprises a motor assembly, a bearing assembly, and a drill bit, the vibration assembly positioned in the bearing assembly.

14. The downhole tool of claim 12 , wherein:

the bottomhole assembly comprises a drive portion, an adjustment portion, and a bearing assembly, the vibration assembly positioned in the bearing assembly; and

the bearing assembly comprises a crossover housing, bearing housings, and a bearing mandrel.

15. The downhole tool of claim 12 , wherein:

the bottomhole assembly comprises an adjustment portion, and a bearing assembly;

the adjustment portion comprises a bearing housing, a bearing mandrel, a lock housing, and an adjustment ring, the vibration assembly positioned between the bearing housing and the bearing mandrel.

16. The downhole tool of claim 12 , wherein the vibration assembly comprises a cage positioned between the vibration race and the additional race, the rollers being positionable in the cage.

17. A method of drilling a wellbore penetrating a subterranean formation, the method comprising:

advancing a downhole tool with a vibration assembly into the subterranean formation, the vibration assembly comprising:

a vibration race positioned in the downhole tool, the vibration race having a non-planar engagement surface comprising a plurality of valleys, a plurality of ramps, and a plurality of flat peaks, wherein each flat peak is positioned between a pair of the plurality of ramps, each valley has a first radius, and each ramp has a second radius that is different from the first radius;

an additional race positioned in the downhole tool a distance from the vibration race, the additional race having another engagement surface facing the non-planar engagement surface of the vibration race; and

rollers in engagement with the non-planar engagement surface and the another engagement surface generating axial movement in the downhole tool by rotating the rollers along the non-planar engagement surface of the vibration race.

18. The method of claim 17 , wherein the generating comprises varying the distance between the vibration race and the additional race by rotating the rollers along the non-planar engagement surface of the vibration race.