Earth-boring tools including shaped cutting elements, and related methods

1. An earth-boring tool, comprising:

at least one shaped cutting element attached to at least one structure of the earth-boring tool, the at least one shaped cutting element comprising:

a substrate base attached to at least one surface of the at least one structure; and

a volume of polycrystalline diamond material on an end of the substrate base, the volume of polycrystalline diamond material comprising:

an apex centered about a longitudinal axis extending through a center of the substrate base;

a generally conical surface extending at a first angle from the substrate base to the apex; and

a flat cutting surface opposing the generally conical surface and extending at a second, different angle from a first point at least substantially proximate a center of the apex to a second point on the at least one shaped cutting element more proximate a lateral side surface of the substrate base.

2. The earth-boring tool of claim 1 , further comprising a plurality of blades, at least one blade of the plurality of blades comprising the at least one structure of the earth-boring tool.

3. The earth-boring tool of claim 1 , further comprising a plurality of roller cones, at least one roller cone of the plurality of roller cones comprising the at least one structure of the earth-boring tool.

4. The earth-boring tool of claim 1 , wherein the at least one shaped cutting element exhibits a negative physical back rake angle and a negative effective back rake angle.

5. The earth-boring tool of claim 1 , wherein the at least one shaped cutting element exhibits a negative physical back rake angle and a neutral effective back rake angle.

6. The earth-boring tool of claim 1 , wherein the at least one shaped cutting element exhibits a negative physical back rake angle and a positive effective back rake angle.

7. The earth-boring tool of claim 1 , wherein the at least one shaped cutting element exhibits a neutral physical back rake angle and a negative effective back rake angle.

8. The earth-boring tool of claim 1 , wherein the at least one shaped cutting element exhibits a neutral physical back rake angle and a positive effective back rake angle.

9. The earth-boring tool of claim 1 , wherein the at least one shaped cutting element exhibits a positive physical back rake angle and a positive effective back rake angle.

10. The earth-boring tool of claim 1 , wherein the at least one shaped cutting element comprises at least two shaped cutting elements, a first of the at least two shaped cutting elements exhibiting at least one of a different physical back rake angle or a different effective back rake angle than a second of the at least two shaped cutting elements.

11. The earth-boring tool of claim 1 , wherein the first angle is within a range of from about thirty degrees (30°) to about sixty degrees (60°) between the generally conical surface and a phantom line extending from the lateral side surface of the substrate base, and wherein the second, different angle is within a range of from about fifteen degrees (15°) to about ninety degrees (90°) between the flat cutting surface and the longitudinal axis.

12. An earth-boring tool, comprising:

at least one shaped cutting element attached to at least one structure of the earth-boring tool, the at least one shaped cutting element comprising:

a substrate base attached to at least one surface of the at least one structure; and

a volume of polycrystalline diamond material on an end of the substrate base, the volume of polycrystalline diamond material comprising:

a generally conical surface;

an apex offset from a longitudinal axis extending through a center of the substrate base; and

a flat cutting surface extending from a first point at least substantially proximate a center of the apex to a second point on the at least one shaped cutting element more proximate a lateral side surface of the substrate base, a distance between the first point and the second point greater than a distance between the second point and the lateral side surface of the substrate base.

13. The earth-boring tool of claim 12 , further comprising a plurality of blades, at least one blade of the plurality of blades comprising the at least one structure of the earth-boring tool.

14. The earth-boring tool of claim 12 , wherein the at least one shaped cutting element exhibits a negative physical back rake angle, and either a negative effective back rake angle, a neutral effective back rake angle, or a positive effective back rake angle.

15. The earth-boring tool of claim 12 , wherein the at least one shaped cutting element exhibits a neutral physical back rake angle, and either a negative effective back rake angle or a positive effective back rake angle.

16. The earth-boring tool of claim 12 , wherein the at least one shaped cutting element exhibits a positive physical back rake angle and a positive effective back rake angle.

17. The earth-boring tool of claim 12 , wherein the at least one shaped cutting element comprises at least two shaped cutting elements, a first of the at least two shaped cutting elements exhibiting at least one of a different physical back rake angle or a different effective back rake angle than a second of the at least two shaped cutting elements.

18. The earth-boring tool of claim 12 , wherein a first angle within a range of from about thirty degrees (30°) to about sixty degrees (60°) exists between the generally conical surface and a phantom line extending from the lateral side surface of the substrate base, and wherein a second angle within a range of from about fifteen degrees (15°) to about ninety degrees (90°) exists between the flat cutting surface and the longitudinal axis.

19. The earth-boring tool of claim 12 , further comprising:

at least one additional shaped cutting element attached to the at least one structure of the earth-boring tool, the at least one additional shaped cutting element comprising:

an additional substrate base attached to the at least one surface of the at least one ether structure; and

another volume of polycrystalline diamond material on an end of the additional substrate base, the another volume of polycrystalline diamond material comprising:

an additional apex centered about another longitudinal axis extending through a center of the additional substrate base;

an additional generally conical surface extending at a first angle from the additional substrate base to the additional apex; and

an additional flat cutting surface opposing the additional generally conical surface and extending at a second, different angle from a point at least substantially proximate a center of the additional apex to another point on the at least one additional shaped cutting element more proximate a lateral side surface of the additional substrate base.

20. A method of removing material from a subterranean formation, comprising:

rotating an earth-boring tool within a wellbore in the subterranean formation, the earth-boring tool comprising:

at least one shaped cutting element attached to at least one structure of the earth-boring tool, the at least one shaped cutting element comprising:

a substrate base attached to at least one surface of the at least one structure;

a generally conical surface extending at a first angle from the substrate base to an apex; and

a flat cutting surface opposing the generally conical surface and extending at a second, different angle from a first point substantially proximate a center of the apex to a second point more proximate a lateral sidewall of the substrate base, the flat cutting surface contacting a surface of the subterranean formation at an angle within a range of from about forty-five degrees (45°) to about one hundred twenty degrees (120°) during rotation of the earth-boring tool.