Borehole stabilization while drilling

• US 20040045741A1
• Filed: 06/13/2003
• Published: 03/11/2004
• Est. Priority Date: 07/18/2001
• Status: Active Grant

• Current Assignee: Tesco Corporation US (Emerson Electric Company)
• Original Assignee: Tesco Corporation US (Emerson Electric Company)
• Inventors: Warren, Tommy W., Angman, Per G., Slack, Maurice William, Tessari, Robert M.
• Granted Patent: US 7,013,992 B2
• Time in Patent Office: Days
• US Class Current: 175/57
• CPC Class Codes: E21B 17/10 Wear protectors; Centralising devices , e.g. stabilisers
• CPC Class Codes: E21B 17/16 Drill collars
• CPC Class Codes: E21B 29/00 Cutting or destroying pipes, packers, plugs or wire lines, located in boreholes or wells, e.g. cutting of damaged pipes, of windows; Deforming of pipes in boreholes or wells; Reconditioning of well casings while in the ground
• CPC Class Codes: E21B 43/10 Setting of casings, screens, liners or the like in wells
• CPC Class Codes: E21B 7/20 Driving or forcing casings or pipes into boreholes, e.g. sinking; Simultaneously drilling and casing boreholes

Abstract

A method for drilling in unconsolidated formation is taught. In particular, a method for borehole stabilization in an unconsolidated formation includes providing a drill string; rotating the drill string to drive a drill bit to drill a borehole having a borehole wall; driving the drill string against the borehole wall while rotating the drill string to plaster the surface of the borehole wall.

Claims

1. A method for stabilizing a borehole while drilling comprising:

providing a drill string including a drill bit connected at a distal end thereof and a pad carried by the drill string to move axially and rotationally with the drill bit;

rotating the drill bit to drill a borehole, the borehole including a borehole wall; and

driving the pad substantially continuously against the borehole wall while rotating the drill bit to apply a lateral wall stress load helically about the borehole wall.

2. The method of claim 1, wherein the drill bit is driven by rotation of the drill string the pad is carried by the drill string to move rotationally and axially therewith.

3. The method of claim 1, wherein the pad applies lateral wall stress load to the borehole wall as it is driven against the borehole wall to compact earthen materials exposed on the borehole wall.

4. The method of claim 1, wherein the pad applies lateral wall stress load to the borehole wall as it is driven against the borehole wall to plaster borehole solids against the borehole wall.

5. The method of claim 1, wherein the pad applies lateral wall stress load to the borehole wall as it is driven against the borehole wall to reduce the hydraulic film between the pad and the borehole wall such that there is solid to solid contact.

6. The method of claim 1, wherein the pad applies lateral wall stress load to the borehole wall as it is driven against the borehole wall to reduce the hydraulic film between the pad and borehole solids such that there is solid to solid contact and the borehole solids are driven against the borehole wall.

7. The method of claim 1, further comprising selecting the pad to have wear resistance properties.

8. The method of claim 1, further comprising selecting the pad to ride against, substantially without digging into, the borehole wall.

9. The method of claim 1, further comprising driving the pad to sweep the complete circumference of the borehole wall during each revolution of the drill bit.

10. The method of claim 1, wherein the drill bit is driven by rotation of the drill string and the method further comprises driving the pad to sweep the complete circumference of the borehole wall during each revolution of the drill string.

11. The method of claim 1 further comprising stabilizing the drill string to reduce contact of the drill string with the borehole wall except at the pad.

12. A borehole drilling apparatus comprising:

a drill string;

a drill bit connected at a distal end of the drill string; and

a pad carried by the drill string to move axially and rotationally with the drill bit, the drill bit being rotatable to drill a borehole, the borehole including a borehole wall and the pad being drivable substantially continuously against the borehole wall to apply a lateral wall stress load helically about the borehole wall as it is moved with the drill bit to stabilize the borehole wall.

13. The borehole drilling apparatus of claim 12 wherein the drill string includes a continuous length of tubing.

14. The borehole drilling apparatus of claim 12 wherein the drill string includes interconnected joints of tubing.

15. The borehole drilling apparatus of claim 12 wherein the drill string includes a string of casing joints connected together for both drilling the borehole and thereafter, remaining down hole to line the borehole.

16. The borehole drilling apparatus of claim 12 wherein the drill bit is driven by rotation of the drill string and the pad is carried by the drill string to move rotationally and axially therewith.

17. The borehole drilling apparatus of claim 12 wherein the pad applies lateral wall stress load to the borehole wall as it is driven against the borehole wall and the stress load causes compaction of the earthen materials exposed on the borehole wall and plasters materials against the borehole wall.

18. The borehole drilling apparatus of claim 12 wherein the pad includes a means for resisting wear from solid contact.

19. The borehole drilling apparatus of claim 18 wherein the means for resisting wear is applied at the surface of the pad that has solid contact.

20. The borehole drilling apparatus of claim 12 wherein the pad includes a leading edge and the leading edge is graduated to ride over the borehole wall.

21. The borehole drilling apparatus of claim 12 further comprising a second pad carried by the drill string to move axially and rotationally with the drill bit.

22. The borehole drilling apparatus of claim 12 further comprising a means for biasing the pad outwardly such that the pad includes an effective radius from a center axis of the drill string that extends outside the radius of the borehole if not constrained within the borehole.

23. The borehole drilling apparatus of claim 12 wherein the pad is positioned adjacent the bottom end of the drill string.

24. The method of claim 12 further comprising a stabilizing means on the drill string to reduce contact of the drill string with the borehole wall except at the pad.

25. A method for drilling a borehole having a borehole wall, the method comprising:

providing a drill string;

rotating the drill string to drive a drill bit to drill the borehole; and

driving the drill string against the borehole wall while rotating the drill string such that a lateral wall contact load is applied by the drill string against the borehole wall to consolidate the exposed wall earth materials to increase stability of the borehole wall.

26. The method of claim 25 wherein the drill string is formed of drill pipe.

27. The method of claim 25 wherein the drill string is formed of casing joints connected by casing connections.

28. The method of claim 25 wherein the casing joints connected by casing connections.

29. The method of claim 25 wherein the drill string is driven against the borehole wall by provision of a bend in the drill string.

30. The method of claim 25 wherein the drill string is driven against the borehole wall by provision of a plurality of a bends along an interval of the drill string.

31. The method of claim 30 wherein the bends are intentionally imposed in the drill string.

32. The method of claim 29 further comprising providing wear protection at the bend.

33. The method of claim 29 further comprising selecting the angle magnitude of the bend.

34. The method of claim 29 further comprising the angular direction of the bend.

35. The method of claim 29 wherein the bend defines an outer bend area on the drill string and the method further comprising providing wear protection at the outer bend area.

37. The method of claim 25 wherein the drill string is formed of drill pipe.

38. The method of claim 25 wherein the drill string is formed of casing joints connected by casing connections.

39. The method of claim 25 wherein the casing joints connected by casing connections.

40. The method of claim 25 wherein the drill string is driven against the borehole wall by provision of a bend in the drill string.

41. The method of claim 25 wherein the drill string is driven against the borehole wall by provision of a plurality of a bends along an interval of the drill string.

42. The method of claim 30 wherein the bends are intentionally imposed in the drill string.

43. The method of claim 29 further comprising selecting the angle magnitude of the bend.

44. The method of claim 29 further comprising the angular direction of the bend.

45. The method of claim 29 wherein the bend defines an outer bend area on the drill string and the method further comprising providing wear protection at the outer bend area.

36. A method for stabilizing a borehole wall in an unconsolidated formation, the method comprising:

providing a drill string;

rotating the drill string to drive a drill bit to drill a borehole having the borehole wall;

driving the drill string against the borehole wall while rotating the drill string to plaster the surface of the borehole wall.

46. The method of claim 36 further comprising selecting the drill string to have a first bend angle and a second bend angle in an interval.

47. The method of claim 46 wherein the directional orientation of the first bend angle is selected.

48. The method of claim 46 wherein the first bend angle is generated at a connection between an upper casing joint and a lower casing joint.

49. The method of claim 48 wherein the connection includes a threaded coupling having a mill end box having a center axis and a field end box having a center axis and the mill end box center axis being angularly offset from the field end box center axis to form a coupling bend angle and the bend angle is controlled by selecting the coupling bend angle.

50. The method of claim 46 wherein the first bend angle is formed by incorporating into the interval a casing joint having a characteristic capable of generating a bend angle in a casing string.

51. The method of claim 46 wherein the first bend angle is formed by incorporating into the interval a casing coupling having a characteristic capable of generating a bend angle in a casing string.

52. A borehole stabilizing apparatus for use with a drilling apparatus comprising:

a pad installable into a drill string to move axially and rotationally with a drill bit of the drill string, the drill bit being rotatable to drill a borehole including a borehole wall, the pad being drivable substantially continuously against the borehole wall to apply a lateral wall stress load helically about the borehole wall during drilling.

53. The borehole stabilizing apparatus of claim 52 wherein the pad is formed to provide a smooth resilient contact stress that sweeps substantially the complete circumference of the borehole wall each revolution of the drill bit, or in the case of rotary drilling, each revolution of the drill string.

54. The borehole stabilizing apparatus of claim 53 wherein the pad is biased outwardly from the drill string.

55. The borehole stabilizing apparatus of claim 53 wherein drill string resiliency causes the pad to be biased outwardly against the borehole wall.