Earth-boring tools, methods of forming earth-boring tools, and methods of forming a borehole in a subterranean formation

1. An earth-boring tool, comprising:

a body having a face at a leading end thereof;

blades extending from the body and comprising primary blades and secondary blades; and

cutting elements on the blades and arranged in groups each comprising neighboring cutting elements sequentially positioned directly radially adjacent one another across the face of the body, wherein:

all of the cutting elements disposed on the primary blades belong to groups exhibiting a first spiral configuration; and

all of the cutting elements disposed on the secondary blades belong to additional groups exhibiting a second spiral configuration opposing the first spiral configuration.

2. The earth-boring tool of claim 1 , wherein the blades comprise an even quantity of the primary blades and an even quantity of the secondary blades.

3. The earth-boring tool of claim 1 , wherein the blades comprise an even quantity of one of the primary blades and the secondary blades, and an odd quantity of the other of the primary blades and the secondary blades.

4. The earth-boring tool of claim 1 , wherein the blades comprise three of the primary blades and three of the secondary blades.

5. The earth-boring tool of claim 4 , wherein each of the groups comprises three neighboring cutting elements.

6. The earth-boring tool of claim 5 , wherein the three neighboring cutting elements of each of the groups are circumferentially separated from one another by an angle within a range of from 100 degrees to 140 degrees relative to a rotational axis of the earth-boring tool.

7. The earth-boring tool of claim 4 , wherein a sequentially last cutting element of at least one of the groups is circumferentially separated from a sequentially first cutting element of a subsequent, adjacent group by an angle within a range of from 160 degrees to 200 degrees relative to a rotational axis of the earth-boring tool.

8. The earth-boring tool of claim 4 , wherein a sequentially first cutting element of at least one of the groups is circumferentially separated from a sequentially last cutting element of a preceding, adjacent group by an angle between 180 degrees and 190 degrees relative to a rotational axis of the earth-boring tool.

9. The earth-boring tool of claim 1 , wherein all of the groups disposed on the primary blades exhibit a reverse spiral configuration, and wherein all of the groups disposed on the secondary blades exhibit a forward spiral configuration.

10. The earth-boring tool of claim 1 , wherein at least one of the cutting elements exhibits at least one of a different size, a different shape, a different chamfer, a different rake, a different exposure, a different diamond grade, a different diamond abrasion resistance property, and a different impact resistance property than at least one other of the cutting elements.

11. The earth-boring tool of claim 1 , wherein the cutting elements of a first of the groups proximate a rotational axis of the earth-boring tool and a second of the groups radially adjacent the first of the groups each exhibit a smaller size than the cutting elements of radially subsequent groups.

12. The earth-boring tool of claim 1 , further comprising backup cutting elements rotationally behind and at substantially the same radial positions as at least some of the cutting elements on the blades.

13. A method of forming an earth-boring tool, comprising:

forming a body comprising a face at a leading end thereof, blades extending from the body and comprising primary blades and secondary blades; and

disposing cutting elements on the blades in groups each comprising neighboring cutting elements sequentially positioned directly radially adjacent one another across the face of the body, wherein:

all of the cutting elements disposed on the primary blades belong to groups exhibiting a first spiral configuration; and

all of the cutting elements disposed on the secondary blades belong to additional groups exhibiting a second spiral configuration opposing the first spiral configuration.

14. The method of claim 13 , wherein forming a body comprises forming the blades to comprise an even quantity of the primary blades and an even quantity of the secondary blades.

15. The method of claim 13 , wherein forming a body comprises forming the blades to comprise an even quantity of one of the primary blades and the secondary blades, and an odd quantity of the other of the primary blades and the secondary blades.

16. The method of claim 13 , wherein forming a body comprises forming the primary blades to circumferentially alternate with the secondary blades.

17. The method of claim 13 , wherein disposing cutting elements on the blades in groups comprises:

forming a first three of the groups radially proximate a rotational axis of the earth-boring tool to each exhibit a reverse spiral configuration; and

forming additional groups radially subsequent to the first three of the groups to alternate with one another between forward spiral configurations and reverse spiral configurations.

18. The method of claim 13 , wherein disposing cutting elements on the blades in groups comprises forming at least some of the groups to comprise three of the neighboring cutting elements circumferentially separated from one another by an angle within a range of from 100 degrees to 140 degrees relative to a rotational axis of the earth-boring tool.

19. A method of forming a borehole in a subterranean formation, comprising:

disposing an earth-boring tool at a distal end of a drill string in a borehole in a subterranean formation, the earth-boring tool comprising:

a body having a face at a leading end thereof;

blades extending from the body and comprising primary blades and secondary blades; and

cutting elements on the blades and arranged in groups each comprising neighboring cutting elements sequentially positioned directly radially adjacent one another across the face of the body, wherein:

all of the cutting elements disposed on the primary blades belong to groups exhibiting a first spiral configuration; and

all of the cutting elements disposed on the secondary blades belong to additional groups exhibiting a second spiral configuration opposing the first spiral configuration;

applying weight on bit to the earth-boring tool through the drill string to contact the subterranean formation while rotating the earth-boring tool; and

engaging the subterranean formation with the cutting elements of the rotating earth-boring tool.