Systems and methods for directionally drilling a borehole using a continuously variable transmission

1. A system configured to directionally drill a borehole, comprising:

a biasing subsystem configured to control a tendency of a bottom hole assembly during drilling of the borehole; and

a mechanical continuously variable transmission, wherein an output shaft of the continuously variable transmission is coupled to the biasing subsystem such that the continuously variable transmission is configured to control relative rotation of one or more components of the biasing subsystem during the drilling.

2. The system of claim 1 , wherein the system is further configured as a rotary steerable system.

3. The system of claim 1 , wherein the biasing subsystem is further configured to control the tendency of the bottom hole assembly in three dimensions.

4. The system of claim 1 , wherein the biasing subsystem is further configured to control the tendency of the bottom hole assembly in two dimensions.

5. The system of claim 1 , wherein the biasing subsystem comprises an adjustable stabilizer.

6. The system of claim 1 , wherein the biasing subsystem comprises an orienter conveyed on coiled tubing.

7. The system of claim 1 , wherein the system further comprises a conveyance means configured to move the biasing subsystem and the continuously variable transmission, and wherein the conveyance means comprises wireline, a drill string, coiled tubing, casing while drilling means, or self propelled means.

8. The system of claim 1 , wherein the biasing subsystem is further configured to rotationally position the bottom hole assembly.

9. The system of claim 1 , wherein the biasing subsystem is further configured to axially position the bottom hole assembly.

10. The system of claim 9 , wherein one or more drilling components of the system are coupled to a ball screw.

11. The system of claim 1 , wherein the biasing subsystem is further configured as a push-the-bit system.

12. The system of claim 1 , wherein the biasing subsystem is further configured as a point-the-bit system.

13. The system of claim 1 , wherein the continuously variable transmission comprises a single stage continuously variable transmission.

14. The system of claim 1 , wherein the continuously variable transmission comprises a multiple stage continuously variable transmission.

15. The system of claim 1 , wherein a transmission ratio of the continuously variable transmission is varied depending on one or more characteristics selected for the borehole.

16. The system of claim 1 , wherein a transmission ratio of the continuously variable transmission is varied depending on one or more characteristics of a formation in which the borehole will be drilled.

17. The system of claim 1 , wherein the continuously variable transmission comprises mechanical elements for controlling the relative rotation of the one or more components.

18. The system of claim 1 , wherein the continuously variable transmission comprises conical elements, and wherein relative rotation of the conical elements controls the relative rotation of the one or more components.

19. The system of claim 1 , wherein the continuously variable transmission comprises spherical elements, and wherein relative rotation of the spherical elements controls the relative rotation of the one or more components.

20. The system of claim 1 , wherein the continuously variable transmission comprises disk elements, and wherein relative rotation of the disk elements controls the relative rotation of the one or more components.

21. The system of claim 1 , wherein the continuously variable transmission comprises toroidal elements, and wherein relative rotation of the toroidal elements controls the relative rotation of the one or more components.

22. The system of claim 1 , wherein the continuously variable transmission comprises one or more belts coupled to pulley elements, and wherein an effective diameter of the pulley elements controls the relative rotation of the one or more components.

23. The system of claim 1 , wherein the continuously variable transmission comprises a gear and tooth assembly that couples control arms to mechanical elements of the continuously variable transmission, wherein translation of the control arms is converted to rotation of the mechanical elements, and wherein relative rotation of the mechanical elements controls the relative rotation of the one or more components.

24. The system of claim 1 , wherein the output shaft of the continuously variable transmission is further coupled to the one or more components by a mandrel.

25. The system of claim 1 , wherein the continuously variable transmission comprises a central cylinder traversing its longitudinal axis, and wherein the central cylinder is configured such that drilling fluid can flow through the central cylinder.

26. The system of claim 1 , further comprising a control subsystem coupled to the continuously variable transmission, wherein the control subsystem comprises an electrical subsystem that is configured to alter one or more parameters of the continuously variable transmission.

27. The system of claim 1 , further comprising a control subsystem coupled to the continuously variable transmission, wherein the control subsystem comprises an electro-magnetic subsystem that is configured to alter one or more parameters of the continuously variable transmission.

28. The system of claim 1 , further comprising a control subsystem coupled to the continuously variable transmission, wherein the control subsystem comprises a mechanical subsystem that is configured to alter one or more parameters of the continuously variable transmission.

29. The system of claim 1 , further comprising a control subsystem coupled to the continuously variable transmission, wherein the control subsystem comprises a hydraulic subsystem that is configured to alter one or more parameters of the continuously variable transmission.

30. The system of claim 1 , further comprising a control subsystem coupled to the continuously variable transmission, wherein the control subsystem comprises an electrical subsystem, an electro-magnetic subsystem, a mechanical subsystem, a hydraulic subsystem, or some combination thereof that is configured to alter one or more parameters of the continuously variable transmission.

31. The system of claim 1 , further comprising a control subsystem coupled to the continuously variable transmission, wherein the control subsystem is configured to actively alter one or more parameters of the continuously variable transmission.

32. The system of claim 1 , further comprising a control subsystem coupled to the continuously variable transmission, wherein the control subsystem is configured to passively alter one or more parameters of the continuously variable transmission.

33. The system of claim 1 , further comprising a power supply coupled to the continuously variable transmission, wherein an input shaft of the continuously variable transmission is coupled directly to the power supply.

34. The system of claim 1 , further comprising a power supply coupled to the continuously variable transmission, wherein an input shaft of the continuously variable transmission is coupled indirectly to the power supply.

35. The system of claim 1 , further comprising a power supply coupled to the continuously variable transmission, wherein the power supply is generated by relative rotation between elements of the system or between one or more elements of the system and a formation in which the borehole is being drilled.

36. The system of claim 1 , further comprising a power supply coupled to the continuously variable transmission, wherein the power supply is generated by relative rotation between a non-rotating sleeve and a drive shaft.

37. The system of claim 1 , further comprising a power supply coupled to the continuously variable transmission, wherein the power supply comprises a turbine assembly.

38. The system of claim 1 , further comprising a power supply coupled to the continuously variable transmission, wherein the power supply comprises an electric motor.

39. The system of claim 1 , further comprising a power supply coupled to the continuously variable transmission, wherein the power supply comprises a positive displacement motor.

40. The system of claim 1 , further comprising a power supply coupled to the continuously variable transmission, wherein the power supply comprises a turbine assembly in combination with a positive displacement motor.

41. The system of claim 1 , wherein the continuously variable transmission is further configured as an infinitely variable transmission.

42. The system of claim 1 , further comprising a fixed gear ratio device coupled to the continuously variable transmission, wherein the fixed gear ratio device is configured to provide increased control of a transmission ratio of the continuously variable transmission.

43. The system of claim 1 , further comprising a harmonic drive coupled to the continuously variable transmission, wherein the harmonic drive is configured to provide increased control of a transmission ratio of the continuously variable transmission.

44. The system of claim 1 , wherein the system is further configured as a measuring-while-drilling system.

45. A method for directionally drilling a borehole, comprising:

controlling a tendency of a bottom hole assembly during drilling of the borehole using a biasing subsystem;

connecting the innut shaft of a continuously variable transmission to a downhole power supply;

controlling the power transmission ratio of said continuously variable transmission between said input shaft and an output shaft; and

controlling relative rotation of one or more components of the biasing subsystem using said continuously variable transmission during the drilling, wherein the one or more components are coupled to said output shaft of the continuously variable transmission.

46. The method of claim 45 , wherein the biasing subsystem is configured as a rotary steerable system.

47. The method of claim 45 , wherein said controlling the tendency comprises controlling the tendency of the bottom hole assembly in three dimensions.

48. The method of claim 45 , wherein said controlling the tendency comprises controlling the tendency of the bottom hole assembly in two dimensions.

49. The method of claim 45 , wherein the biasing subsystem comprises an adjustable stabilizer.

50. The method of claim 45 , wherein the biasing subsystem comprises an orienter conveyed on coiled tubing.

51. The method of claim 45 , wherein said controlling the tendency comprises rotationally positioning the bottom hole assembly.

52. The method of claim 45 , wherein said controlling the tendency comprises axially positioning the bottom hole assembly.

53. The method of claim 45 , wherein the biasing subsystem is configured as a push-the-bit system.

54. The method of claim 45 , wherein the biasing subsystem is configured as a point-the-bit system.

55. The method of claim 45 , further comprising altering a transmission ratio of the continuously variable transmission depending on one or more characteristics selected for the borehole.

56. The method of claim 45 , further comprising altering a transmission ratio of the continuously variable transmission depending on one or more characteristics of a formation in which the borehole is being drilled.

57. The method of claim 45 , further comprising altering one or more parameters of the continuously variable transmission electrically, electro-magnetically, mechanically, hydraulically, or some combination thereof during the drilling.

58. The method of claim 45 , further comprising actively altering one or more parameters of the continuously variable transmission during the drilling.

59. The method of claim 45 , further comprising passively altering one or more parameters of the continuously variable transmission during the drilling.

60. The method of claim 45 , wherein the continuously variable transmission is configured as a mechanical continuously variable transmission.