Directional drilling machine and method of directional drilling

• US 6,491,115 B2
• Filed: 01/22/2001
• Issued: 12/10/2002
• Est. Priority Date: 03/15/2000
• Status: Expired due to Fees

• Current Assignee: Vermeer Manufacturing Company
• Original Assignee: Vermeer Manufacturing Company
• Inventors: Stelter, Mark R., Runquist, Randy, Austin, Gregg A., Bischel, Brian J., Van Houwelingen, Mark
• Primary Examiner(s): PEZZUTO, ROBERT ERIC
• Application Number:
  US09/767,107
• Publication Number:
  US 20010022238A1
• Time in Patent Office: 687 Days
• Field of Search: 175/24, 175/27, 175/19, 175/26, 175/40, 175/45, 175/48, 175/61, 175/57, 340/853.2, 340/853.3, 340/853.4, 340/853.5, 340/853.6, 173/28, 173/46, 173/152
• US Class Current: 175/27
• CPC Class Codes: E21B 19/086 with a fluid-actuated cylinder E21B19/084, E21B19/087, E21B19/09 take precedence
• CPC Class Codes: E21B 44/02 Automatic control of the tool feed E21B44/005, E21B44/10 take precedence
• CPC Class Codes: E21B 7/04 Directional drilling

Abstract

A system, apparatus and method for automatically limiting the thrust force applied to a drill string during an underground boring process, in order to prevent the deformation or collapse to the drill rods due to reaching the yield point of the rods. One or more drill string characteristics that have an impact on the yield point of the drill string, or portions of the drill string, are determined. The yield point of the drill string or portion is computed, where the yield point is computed as a function of the drill string characteristics. The thrust force imparted to the drill string is adjusted in response to the computed yield point.

Claims

1. A method for controlling the underground transit of a drill string, comprising:

determining one or more drill string characteristics influencing a yield point of at least a portion of the drill string;

computing the yield point of the drill string portion as a function of the one or more drill string characteristics; and

adjusting a thrust force imparted to the drill string in response to the computed yield point.

2. The method of claim 1, wherein determining the drill string characteristics comprises repeatedly determining the drill string characteristics and computing the yield point, such that the thrust force is repeatedly adjusted.

3. The method of claim 1, wherein determining one or more drill string characteristics comprises measuring an unsupported length of the drill string.

4. The method of claim 3, wherein measuring an unsupported length of the drill string comprises measuring a length of the drill string approximately between a coupling region at the proximal end of the drill string, and a predetermined point proximate the ground.

5. The method of claim 1, wherein determining one or more drill string characteristics comprises measuring a length of the drill string having low radial compression applied thereto, wherein the low radial compression is such that the length of drill string is capable of bending.

6. The method of claim 1, wherein determining one or more drill string characteristics comprises ascertaining the bend radius of at least one portion of the drill string.

7. The method of claim 1, wherein determining one or more drill string characteristics comprises ascertaining a minimum bend radius occurring along the drill string, wherein the minimum bend radius corresponds to a maximum bend along the drill string.

8. The method of claim 1, further comprising overriding adjusting the thrust force in response to an override signal.

9. The method of claim 1, further comprising eliminating adjustments to the thrust force if a current thrust force is within a predetermined optimal operating range.

10. The method of claim 1, wherein adjusting the thrust force comprises limiting the thrust force to an allowable thrust force that is less than a force corresponding to the computed yield point.

11. The method of claim 1, wherein adjusting the thrust force comprises increasing the thrust force if the thrust force imparted to the drill string is less than the computed yield point by at least a predefined amount.

12. The method of claim 1, wherein adjusting the thrust force comprises decreasing the thrust force if the thrust force imparted to the drill string is within a predefined range of a force corresponding to the computed yield point.

13. The method of claim 1, further comprising moving the drill string along an underground path in accordance with the adjusted thrust force.

14. The method of claim 1, wherein determining the drill string characteristics comprises sensing dimensional attributes of the drill string.

15. The method of claim 1, wherein the drill string portion comprises between one and all drill rods forming the drill string.

16. The method of claim 1, further comprising providing a notification of when the thrust force is being adjusted.

17. A method for controlling the subterranean advancement of one or more drill rods forming a drill string, comprising:

measuring an unsupported length of the drill string;

calculating the yield point of the drill string portion as a function of the unsupported length of the drill string; and

limiting a thrust force imparted to the drill string to a maximum allowable thrust force such that the yield point will not be reached.

18. The method of claim 17, further comprising overriding limiting the thrust force in response to an override signal.

19. The method of claim 17, wherein limiting the thrust force comprises reducing the thrust force such that the yield point is not reached.

20. The method of claim 17, wherein limiting the thrust force comprises maintaining the thrust force at a thrust level below a force corresponding to the yield point.

21. The method of claim 17, wherein calculating the yield point comprises determining a threshold thrust force that will cause buckling of the drill string based at least in part on the measured unsupported length of the drill string.

22. The method of claim 17, wherein measuring an unsupported length of the drill string comprises measuring a length of the drill string approximately between a coupling region at the proximal end of the drill string and ground level.

23. The method of claim 17, wherein measuring an unsupported length of the drill string comprises measuring an approximate length of the drill string between a coupling region at the proximal end of the drill string and a predetermined subsurface level.

24. The method of claim 23, wherein the predetermined subsurface level is an approximate distance below a ground surface having sufficient structural support to prevent bending of the drill string at the predetermined subsurface level.

25. The method of claim 17, wherein measuring the unsupported length of drill string comprises measuring the movement of a thrust mechanism that advances the drill string with a position transducer, and computing the unsupported length of drill string based on the distance traveled by the thrust mechanism.

26. The method of claim 17, wherein measuring the unsupported length of drill string comprises measuring the movement of a thrust mechanism that advances the drill string with a plurality of position sensors along the path of the thrust mechanism, and computing the unsupported length of drill string based on the distance traveled by the thrust mechanism.

27. The method of claim 17, wherein measuring the unsupported length of drill string comprises steps for determining the unsupported length of the drill string.

28. A method for controlling the movement of a drill string;

moving the drill string along an underground path;

determining a bend radius of at least a portion of the drill string along the underground path;

computing the yield point of the drill string portion as a function of the bend radius; and

adjusting a thrust force imparted to the drill string in response to the computed yield point.

29. The method of claim 28, wherein adjusting the thrust force comprises reducing the thrust force such that the yield point is not reached.

30. The method of claim 28, wherein adjusting the thrust force comprises capping the thrust force to a maximum thrust force such that the yield point is not reached.

31. The method of claim 28, wherein adjusting the thrust force comprises increasing the thrust force to increase drilling performance, while ensuring that the yield point is not reached.

32. The method of claim 28, wherein adjusting the thrust force comprises increasing the thrust force as the bend radius increases, whereby the thrust force increases as the drill path tends to become more straight.

33. The method of claim 28, wherein adjusting the thrust force comprises decreasing the thrust force as the bend radius decreases, whereby the thrust force decreases as the drill path tends to become less straight.

34. The method of claim 28, wherein calculating the yield point comprises determining a threshold thrust force that will cause buckling of the drill string based at least in part on the bend radius of the drill string portion.

35. The method of claim 28, wherein determining the bend radius comprises calculating the bend radius from a pre-programmed drill path.

36. The method of claim 28, wherein determining the bend radius comprises transmitting position signals from a sonde attached to the drill string, receiving the position signals at a locator above ground, and ascertaining the bend radius from a drill path derived from the position signals.

37. The method of claim 28, wherein determining the bend radius comprises:

steps for ascertaining a drill path taken by the drill string; and

steps for calculating the bend radius from the drill path.

38. The method of claim 28, wherein determining the bend radius comprises using ground penetrating radar (GPR) to locate the drill string underground.

39. A system for controlling the underground transit of a drill string, comprising:

a thrust engine to generate a thrust force for advancing the drill string;

at least one drill string sensor to sense one or more drill string characteristics impacting a yield point of at least a portion of the drill string;

a controller, coupled to the at least one drill string sensor and to the thrust engine, to calculate the yield point of the drill string portion as a function of the one or more drill string characteristics, and to generate a thrust force adjustment signal based on the calculated yield point; and

wherein the magnitude of the thrust force is dependent on the thrust force adjustment signal.

40. The system of claim 39, further comprising a moveable thrust mechanism coupled to the thrust engine and to the drill string, wherein the thrust engine imparts the thrust force to the thrust mechanism causing the thrust mechanism to move, and wherein the thrust mechanism imparts motion to the drill string in response thereto.

41. The system of claim 39, further comprising a sonde coupled proximate a distal end of the drill string, wherein the sonde transmits position signals indicative of an underground position of the sonde.

42. The system of claim 41, wherein the drill string sensor comprises a locator unit situated above ground to sense the position signals transmitted by the sonde.

43. The system of claim 42, wherein the location unit repeatedly senses the position signals transmitted by the sonde to plot a drill path taken by the drill string portion.

44. The system of claim 43, wherein the controller further determines a bend radius of the drill string portion from the plotted drill path, and wherein the controller calculates the yield point as a function of a bend radius of the drill string portion.

45. The system of claim 39, wherein the drill string sensor comprises means for determining an unsupported length of one or more drill rods forming the drill string.

46. The system of claim 39, wherein the drill string sensor comprises means for determining a bend radius of the drill string portion.

47. The system of claim 39, wherein the drill string sensor comprises a displacement measuring unit to determine an unsupported length of one or more drill rods forming the drill string.

48. The system of claim 39, wherein the drill string sensor comprises a plurality of strain gauges coupled on selected ones of drill rods forming the drill string.

49. The system of claim 39, wherein the thrust force adjustment signal generated by the controller directs the magnitude of the thrust force to increase when the thrust force imparted to the drill string is less than the calculated yield point by at least a predetermined amount.

50. The system of claim 39, wherein the thrust force adjustment signal generated by the controller directs the magnitude of the thrust force to decrease when the thrust force imparted to the drill string is within a predetermined range of the calculated yield point.

51. An apparatus for controlling the underground transit of a drill string, comprising:

means for determining one or more drill string characteristics influencing a yield point of at least a portion of the drill string;

means for computing the yield point of the drill string portion as a function of the one or more drill string characteristics; and

means for adjusting a thrust force imparted to the drill string in response to the computed yield point.

52. The apparatus as in claim 51, further comprising means for notifying an operator that the thrust force is being adjusted.

53. A horizontal drilling machine for directionally drilling a drill string into the ground, the drill string including a plurality of elongated members threaded together in an end-to-end relationship, the drilling machine comprising:

a track;

a rotational driver for rotating the drill string in forward and reverse directions about a longitudinal axis of the drill string;

a thrust mechanism for propelling the rotational driver along the track; and

a thrust limiter that prevents the thrust mechanism from applying a thrust load to the drill string that exceeds a thrust load limit established at least in part by a buckle point of at least one drill string portion, wherein the thrust load limit is less than a maximum thrust load that can otherwise be generated by the thrust mechanism.

54. The horizontal drilling machine as in claim 53, wherein the thrust limiter comprises means for establishing the buckle point of the drill string portion.