Patent EP0551134A1 successfully refreshed from Google Patents.
EP0551134A1
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Method for evaluating formations and bit conditions
Assignee: Baker Hughes Holdings LLC
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Filing: 1993-01-08
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Granted: —
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Expires: 2013-01-08
Abstract
Abstract A method for evaluating formations and bit conditions is presented. The present invention processes signals indicative of downhole weight on bit (WOB), downhole torque (TOR), rate of penetration (ROP) and bit rotations (RPM), while taking into account bit geometry to provide a plurality of well logs and to optimize the drilling process. Drilling operations are monitored and adjusted in response to these processed signals and logs. The processed signals may include the following signals: drilling response, differential pressure, pore pressure, porosity, porosity compensated for formation effects, drilling alert, bit wear factor, abnormal torque, and bearing wear. The logs may include a drilling response log, a differential pressure log, a porosity log, a porosity log compensated for formation effects, a drilling alert log, a wear factor log, a torque analysis log and a bearing wear log.
Inventors
- 👤 Pushkar N. Jogi
- 👤 William A. Zoeller
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 13:28
CPC Classifications
E; E21; E21B; E21B49/00; E21B49/003; E21B12/00; E21B12/02; E21B21/00; E21B21/08; E21B44/00
Claims Analysis
Total Claims: 108
Claim 1
Independent Claim
61 words
CLAIM 1. A method for investigating properties of subsurface formations traversed by a borehole, the method comprising the steps of: generating while drilling a plurality of signals indicative of formation properties derivable from measurements made while drilling; in response to said plurality of signals, generating a drilling response signal; and in response to said drilling response signal, optimizing the drilling process.
Claim 2
Dependent Claim
24 words
CLAIM 2. The method of claim 1 further comprising the step of: in response to said drilling response signal, generating a drilling response log.
Claim 3
Dependent Claim
15 words
CLAIM 3. A drilling response log produced in accordance with the method of claim 2.
Claim 4
Dependent Claim
23 words
CLAIM 4. The method of claim 1 wherein said derivable formation properties comprise properties representative of the mechanical process of drilling the borehole.
Claim 5
Dependent Claim
35 words
CLAIM 5. The method of claim 4 wherein said properties representative of the mechanical process of drilling the borehole include weight on bit (WOB), bit torque (TOR), bit revolutions (RPM) and rate of penetration (ROP).
Claim 6
Dependent Claim
45 words
CLAIM 6. The method of claim 2 wherein said drilling response log comprises the following relationship: drilling response log = log (TOR ROP / (WOB² RPM)) where, TOR = bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit revolutions.
Claim 7
Dependent Claim
17 words
CLAIM 7. The method of claim 2 wherein said drilling response log includes a shale base line.
Claim 8
Dependent Claim
23 words
CLAIM 8. The method of claim 7 further including the step of: orientating said shale base line relative to said drilling response log.
Claim 9
Dependent Claim
34 words
CLAIM 9. The method of claim 1 further comprising the steps of: in response to said drilling response signal, generating a porosity signal; and in response to said porosity signal, optimizing the drilling process.
Claim 10
Dependent Claim
22 words
CLAIM 10. The method of claim 9 further comprising the step of: in response to said porosity signal, generating a porosity log.
Claim 11
Dependent Claim
14 words
CLAIM 11. A porosity log produced in accordance with the method of claim 10.
Claim 12
Dependent Claim
19 words
CLAIM 12. The method of claim 9 further including the step of: compensating said porosity signal for formation effects.
Claim 13
Dependent Claim
22 words
CLAIM 13. The method of claim 12 further comprising the step of: in response to said porosity signal, generating a porosity log.
Claim 14
Dependent Claim
14 words
CLAIM 14. A porosity log produced in accordance with the method of claim 13.
Claim 15
Dependent Claim
26 words
CLAIM 15. The method of claim 12 wherein at least one of said derivable formation properties comprise a property representative of natural radioactivity of the formation.
Claim 16
Dependent Claim
34 words
CLAIM 16. The method of claim 15 wherein said property representative of natural radioactivity comprises: measuring a plurality of emitted gamma rays to provide a signal indicative of the shale volume in the formation.
Claim 17
Dependent Claim
31 words
CLAIM 17. The method of claim 16 wherein said compensating said porosity signal comprises: reducing said porosity signal by a product of said shale volume signal and a shale porosity signal.
Claim 18
Dependent Claim
43 words
CLAIM 18. The method of claim 17 wherein said shale porosity signal comprises the following relationship: shale porosity = Φ max e -(C3 TVD) where, Φ max is the equivalent surface porosity of shale, C3 is a constant, TVD = true vertical depth.
Claim 19
Dependent Claim
68 words
CLAIM 19. The method of claim 10 wherein said porosity log comprises the following relationship: porosity log = A1 (log (TOR ROP / (WOB² RPM)))² + A2 (log (TOR ROP / (WOB² RPM))) + A3 where, TOR ROP / (WOB² RPM) = drilling response, TOR = bit torque, ROP = rate of penetration, WOB = weight of bit, RPM = bit revolutions, A1, A2 and A3 are constants.
Claim 20
Dependent Claim
68 words
CLAIM 20. The method of claim 13 wherein said porosity log comprises the following relationship: porosity log = A1 (log (TOR ROP / (WOB² RPM)))² + A2 (log (TOR ROP / (WOB² RPM))) + A3 where, TOR ROP / (WOB² RPM) = drilling response, TOR = bit torque, ROP = rate of penetration, WOB = weight of bit, RPM = bit revolutions, A1, A2 and A3 are constants.
Claim 21
Dependent Claim
36 words
CLAIM 21. The method of claim 1 further comprising the steps of: in response to said drilling response signal, generating a differential pressure signal; and in response to said differential pressure signal, optimizing the drilling process.
Claim 22
Dependent Claim
24 words
CLAIM 22. The method of claim 21 further comprising the step of: in response to said differential pressure signal, generating a differential pressure log.
Claim 23
Dependent Claim
15 words
CLAIM 23. A differential pressure log produced in accordance with the method of claim 22.
Claim 24
Dependent Claim
21 words
CLAIM 24. The method of claim 21 further including the step of: determining formation pore pressure from said differential pressure signal.
Claim 25
Dependent Claim
33 words
CLAIM 25. The method of claim 21 further including the steps of: determining desired drilling mud density from said differential pressure signal; and adjusting drilling mud density to said desired drilling mud density.
Claim 26
Dependent Claim
20 words
CLAIM 26. The method of claim 21 further including the step of: compensating said differential pressure signal for formation effects.
Claim 27
Dependent Claim
26 words
CLAIM 27. The method of claim 26 wherein at least one of said derivable formation properties comprise a property representative of natural radioactivity of the formation.
Claim 28
Dependent Claim
34 words
CLAIM 28. The method of claim 27 wherein said property representative of natural radioactivity comprises: measuring a plurality of emitted gamma rays to provide a signal indicative of the shale volume in the formation.
Claim 29
Dependent Claim
25 words
CLAIM 29. The method of claim 28 further including the step of: deriving a transformed differential pressure signal to correspond to said shale volume signal.
Claim 30
Dependent Claim
26 words
CLAIM 30. The method of claim 29 wherein said compensating said differential pressure signal comprises: reducing said differential pressure signal by said transformed differential pressure signal.
Claim 31
Dependent Claim
94 words
CLAIM 31. The method of claim 22 wherein said differential pressure log comprises the following relationship: differential pressure log = α ((TOR ROP / (WOB² RPM)) N / (TOR ROP / (WOB² RPM)) A ) - 1) where, (TOR ROP / (WOB² RPM)) N = drilling response under normal pore pressure conditions, (TOR ROP / (WOB² RPM)) A = drilling response under other than normal conditions, TOR = bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit revolutions, α is a function of bit geometry and rock properties.
Claim 32
Dependent Claim
32 words
CLAIM 32. The method of claim 1 furt in response to said drilling response signal, generating a drilling alert signal; and in response to said drilling alert signal, optimizing the drilling process.
Claim 33
Dependent Claim
24 words
CLAIM 33. The method of claim 32 further comprising the step of: in response to said drilling alert signal, generating a drilling alert log.
Claim 34
Dependent Claim
15 words
CLAIM 34. A drilling alert log produced in accordance with the method of claim 33.
Claim 35
Dependent Claim
129 words
CLAIM 35. The method of claim 33 wherein said drilling alert log comprises the following relationship: drilling alert log = log ((TOR ROP / (WOB² RPM)) N α (1 / (TOR ROP / (WOB² RPM)) A2 ) - (1 / (TOR ROP / (WOB² RPM)) A1 )) - (log (TOR ROP / (WOB² RPM)) A2 ) where, (TOR ROP / (WOB² RPM)) N = drilling response for pore pressure equivalent to mud pressure, (TOR ROP / (WOB² RPM)) A1 = drilling response for a selected maximum differential pressure, (TOR ROP / (WOB² RPM)) A2 = drilling response for a drilling problem, TOR = bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit rotations, α is a function of bit geometry and rock properties.
Claim 36
Dependent Claim
86 words
CLAIM 36. The method of claim 33 wherein said drilling alert log comprises a severity ratio, said severity ratio comprising the following relationship: severity ratio = (TOR ROP / (WOB² RPM)) A / (TOR ROP / (WOB² RPM)) N where, (TOR ROP / (WOB² RPM)) A = drilling response under other than normal conditions, (TOR ROP / (WOB² RPM)) N = drilling response under normal pore pressure conditions, TOR = bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit rotations.
Claim 37
Dependent Claim
38 words
CLAIM 37. The method of claim 1 further comprising the steps of: in response to said drilling response signal, generating a bit wear factor signal; and in response to said bit wear factor signal, optimizing the drilling process.
Claim 38
Dependent Claim
23 words
CLAIM 38. The method of claim 37 further comprising the step of: in response to said bit wear factor signal, replacing the bit.
Claim 39
Dependent Claim
26 words
CLAIM 39. The method of claim 37 further comprising the step of: in response to said bit wear factor signal, generating a bit wear factor log.
Claim 40
Dependent Claim
16 words
CLAIM 40. A bit wear factor log produced in accordance with the method of claim 39.
Claim 41
Dependent Claim
158 words
CLAIM 41. The method of claim 39 wherein said bit wear factor log comprises the following relationship when plotted as a function of depth: bit wear factor log = (-(µ e /4) (ROP D / (WOB RPM)) n1 + ((µ e /4) (ROP D / (WOB RPM)) n1 2 + 4 (TOR ROP / (WOB² RPM)) ((TOR ROP / (WOB² RPM)) n1 - (µ e /4) (ROP D / (WOB RPM)) n1 )) 1/2 ) / (2 ((TOR ROP / (WOB RPM)) n1 - ((µ e /4) (ROP D / (WOB RPM)) n1 )) where, (ROP D / (WOB RPM)) n1 = rock drillability at the start of a bit run, (TOR ROP / (WOB² RPM)) n1 = drilling response at the start of a bit run, µ e = effective coefficient of friction between the bit and the formation, TOR = bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit rotations.
Claim 42
Dependent Claim
36 words
CLAIM 42. The method of claim 1 further comprising the steps of: in response to said drilling response signal, generating a bearing wear signal; and in response to said bearing wear signal optimizing the drilling process.
Claim 43
Dependent Claim
22 words
CLAIM 43. The method of claim 42 further comprising the step of: in response to said bearing wear signal, replacing the bit.
Claim 44
Dependent Claim
24 words
CLAIM 44. The method of claim 42 further comprising the step of: in response to said bearing wear signal, generating a bearing wear log.
Claim 45
Dependent Claim
15 words
CLAIM 45. A bearing wear log produced in accordance with the method of claim 44.
Claim 46
Dependent Claim
100 words
CLAIM 46. The method of claim 44 wherein said bearing wear log comprises the following relationship when plotted as a function of depth: bearing wear log = K L1 ((TOR e / (TOR a ROP / (WOB² RPM)))₁ + (TOR e / (TOR a ROP / (WOB² RPM ))) 2 + ... where, TOR e = bit torque expected, TOR a ROP / (WOB² RPM) = drilling response, L1 = depth interval, K = a constant depending on bearing wear, TOR a = measured bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit revolutions.
Claim 47
Dependent Claim
59 words
CLAIM 47. A method for investigating properties of subsurface formations traversed by a borehole, the method comprising the steps of: generating while drilling a plurality of signals indicative of formation properties derivable from measurements made while drilling; in response to said plurality of signals, generating a porosity signal; and in response to said porosity signal, optimizing the drilling process.
Claim 48
Dependent Claim
22 words
CLAIM 48. The method of claim 47 further comprising the step of: in response to said porosity signal, generating a porosity log.
Claim 49
Dependent Claim
14 words
CLAIM 49. A porosity log produced in accordance with the method of claim 48.
Claim 50
Dependent Claim
23 words
CLAIM 50. The method of claim 47 wherein said derivable formation properties comprises properties representative of the mechanical process of drilling the borehole.
Claim 51
Dependent Claim
35 words
CLAIM 51. The method of claim 50 wherein said properties representative of the mechanical process of drilling the borehole include weight on bit (WOB), bit torque (TOR), bit revolutions (RPM) and rate of penetration (ROP).
Claim 52
Dependent Claim
19 words
CLAIM 52. The method of claim 47 further including the step of: compensating said porosity signal for formation effects.
Claim 53
Dependent Claim
22 words
CLAIM 53. The method of claim 52 further comprising the step of: in response to said porosity signal, generating a porosity log.
Claim 54
Dependent Claim
14 words
CLAIM 54. A porosity log produced in accordance with the method of claim 53.
Claim 55
Dependent Claim
26 words
CLAIM 55. The method of claim 52 wherein at least one of said derivable formation properties comprise a property representative of natural radioactivity of the formation.
Claim 56
Dependent Claim
34 words
CLAIM 56. The method of claim 55 wherein said property representative of natural radioactivity comprises: measuring a plurality of emitted gamma rays to provide a signal indicative of the shale volume in the formation.
Claim 57
Dependent Claim
31 words
CLAIM 57. The method of claim 56 wherein said compensating said porosity signal comprises: reducing said porosity signal by a product of said shale volume signal and a shale porosity signal.
Claim 58
Dependent Claim
43 words
CLAIM 58. The method of claim 57 wherein said shale porosity signal comprises the following relationship: shale porosity = Φ max e -(C3 TVD) where, Φ max is the equivalent surface porosity of shale, C3 is a constant, TVD = true vertical depth.
Claim 59
Dependent Claim
68 words
CLAIM 59. The method of claim 48 wherein said porosity log comprises the following relationship: porosity log = A1 (log (TOR ROP / (WOB² RPM)))² + A2 (log (TOR ROP / (WOB² RPM)) + A3 where, TOR ROP / (WOB² RPM) = drilling response, TOR = bit torque, ROP = rate of penetration, WOB = weight of bit, RPM = bit revolutions, A1, A2 and A3 are constants.
Claim 60
Dependent Claim
68 words
CLAIM 60. The method of claim 53 wherein said porosity log comprises the following relationship: porosity log = A1 (log (TOR ROP / (WOB² RPM)))² + A2 (log (TOR ROP / (WOB² RPM)) + A3 where, TOR ROP / (WOB² RPM) = drilling response, TOR = bit torque, ROP = rate of penetration, WOB = weight of bit, RPM = bit revolutions, A1, A2 and A3 are constants.
Claim 61
Dependent Claim
61 words
CLAIM 61. A method for investigating properties of subsurface formations traversed by a borehole, the method comprising the steps of: generating while drilling a plurality of signals indicative of formation properties derivable form measurements made while drilling; in response to said plurality of signals, generating a differential pressure signal; and in response to said differential pressure signal, optimizing the drilling process.
Claim 62
Dependent Claim
24 words
CLAIM 62. The method of claim 61 further comprising the step of: in response to said differential pressure signal, generating a differential pressure log.
Claim 63
Dependent Claim
15 words
CLAIM 63. A differential pressure log produced in accordance with the method of claim 62.
Claim 64
Dependent Claim
21 words
CLAIM 64. The method of claim 61 further including the step of: determining formation pore pressure from said differential pressure signal.
Claim 65
Dependent Claim
33 words
CLAIM 65. The method of claim 61 further including the steps of: determining desired drilling mud density from said differential pressure signal; and adjusting drilling mud density to said desired drilling mud density.
Claim 66
Dependent Claim
23 words
CLAIM 66. The method of claim 61 wherein said derivable formation properties comprises properties representative of the mechanical process of drilling the borehole.
Claim 67
Dependent Claim
35 words
CLAIM 67. The method of claim 66 wherein said properties representative of the mechanical process of drilling the borehole include weight on bit (WOB), bit torque (TOR), bit revolutions (RPM) and rate of penetration (ROP).
Claim 68
Dependent Claim
20 words
CLAIM 68. The method of claim 61 further including the step of: compensating said differential pressure signal for formation effects.
Claim 69
Dependent Claim
26 words
CLAIM 69. The method of claim 68 wherein at least one of said derivable formation properties comprise a property representative of natural radioactivity of the formation.
Claim 70
Dependent Claim
34 words
CLAIM 70. The method of claim 69 wherein said property representative of natural radioactivity comprises: measuring a plurality of emitted gamma rays to provide a signal indicative of the shale volume in the formation.
Claim 71
Dependent Claim
25 words
CLAIM 71. The method of claim 70 further including the step of: deriving a transformed differential pressure signal to correspond to said shale volume signal.
Claim 72
Dependent Claim
26 words
CLAIM 72. The method of claim 71 wherein said compensating said differential pressure signal comprises: reducing said differential pressure signal by said transformed differential pressure signal.
Claim 73
Dependent Claim
94 words
CLAIM 73. The method of claim 62 wherein said differential pressure log comprises the following relationship: differential pressure log = α ((TOR ROP / (WOB² RPM)) N / (TOR ROP / (WOB² RPM)) A ) - 1) where, (TOR ROP / (WOB² RPM)) N = drilling response under normal pore pressure conditions, (TOR ROP / (WOB² RPM)) A = drilling response under other than normal conditions, TOR = bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit revolutions, α is a function of bit geometry and rock properties.
Claim 74
Dependent Claim
61 words
CLAIM 74. A method for investigating properties of subsurface formations traversed by a borehole, the method comprising the steps of: generating while drilling a plurality of signals indicative of formation properties derivable from measurements made while drilling; in response to said plurality of signals, generating a drilling alert signal; and in response to said drilling alert signal, optimizing the drilling process.
Claim 75
Dependent Claim
24 words
CLAIM 75. The method of claim 74 further comprising the step of: in response to said drilling alert signal, generating a drilling alert log.
Claim 76
Dependent Claim
15 words
CLAIM 76. A drilling alert log produced in accordance with the method of claim 75.
Claim 77
Dependent Claim
23 words
CLAIM 77. The method of claim 74 wherein said derivable formation properties comprises properties representative of the mechanical process of drilling the borehole.
Claim 78
Dependent Claim
35 words
CLAIM 78. The method of claim 77 wherein said properties representative of the mechanical process of drilling the borehole include weight on bit (WOB), bit torque (TOR), bit revolutions (RPM) and rate of penetration (ROP).
Claim 79
Dependent Claim
128 words
CLAIM 79. The method of claim 75 wherein said drilling alert log comprises the following relationship: drilling alert log = log ((TOR ROP / (WOB² RPM)) N α (1 / (TOR ROP / (WOB² RPM)) A2 ) - (1 / (TOR ROP / (WOB² RPM)) A1 )) - (log (TOR ROP / (WOB² RPM)) A2 ) where, (TOR ROP / (WOB² RPM)) N = drilling response for pore pressure equivalent to mud pressure, (TOR ROP / (WOB² RPM)) A1 = drilling response for desired operating conditions, (TOR ROP / (WOB² RPM)) A ₂ = drilllng response for a drilling problem, TOR = bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit rotations; α is a function of bit geometry and rock properties.
Claim 80
Dependent Claim
86 words
CLAIM 80. The method of claim 75 wherein said drilling alert log comprises a severity ratio, said severity ratio comprising the following relationship: severity ratio = (TOR ROP / (WOB² RPM)) A / (TOR ROP / (WOB² RPM)) N where, (TOR ROP / (WOB² RPM)) A = drilling response under other than normal conditions, (TOR ROP / (WOB² RPM)) N = drilling response under normal pore pressure conditions, TOR = bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit rotations.
Claim 81
Dependent Claim
63 words
CLAIM 81. A method for investigating properties of subsurface formations traversed by a borehole, the method comprising the steps of: generating while drilling a plurality of signals indicative of formation properties derivable from measurements made while drilling; in response to said plurality of signals, generating a bit wear factor signal; and in response to said bit wear factor signal, optimizing the drilling process.
Claim 82
Dependent Claim
23 words
CLAIM 82. The method of claim 81 further comprising the step of: in response to said bit wear factor signal, replacing the bit.
Claim 83
Dependent Claim
26 words
CLAIM 83. The method of claim 81 further comprising the step of: in response to said bit wear factor signal, generating a bit wear factor log.
Claim 84
Dependent Claim
16 words
CLAIM 84. A bit wear factor log produced in accordance with the method of claim 83.
Claim 85
Dependent Claim
23 words
CLAIM 85. The method of claim 81 wherein said derivable formation properties comprises properties representative of the mechanical process of drilling the borehole.
Claim 86
Dependent Claim
35 words
CLAIM 86. The method of claim 85 wherein said properties representative of the mechanical process of drilling the borehole include weight on bit (WOB), bit torque (TOR), bit revolutions (RPM) and rate of penetration (ROP).
Claim 87
Dependent Claim
156 words
CLAIM 87. The method of claim 83 wherein said bit wear factor log comprises the following relationship when plotted as a function of depth: bit wear factor log = (-(µ e /4) (ROP D / (WOB RPM)) n1 + ((µ e /4) (ROP D / (WOB RPM)) n1 2 + 4 (TOR ROP / (WOB² RPM)) ((TOR ROP/(WOB² RPM)) n1 - (µ e /4) (ROP D / (WOB RPM)) n1 )) 1/2 ) / (2 ((TOR ROP / (WOB RPM)) n1 - ((µ e /4) (ROP D / (WOB RPM)) n1 )) where, (ROP D / (WOB RPM)) n1 = rock drillability at the start of a bit run, (TOR ROP / (WOB² RPM)) n1 = drilling response at the start of a bit run, µ e = effective coefficient of friction between the bit and the formation, TOR = bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit rotations.
Claim 88
Dependent Claim
61 words
CLAIM 88. A method for investigating properties of subsurface formations traversed by a borehole, the method comprising the steps of: generating while drilling a plurality of signals indicative of formation properties derivable from measurements made while drilling; in response to said plurality of signals, generating a torque analysis signal; and in response to said torque analysis signal, optimizing the drilling process.
Claim 89
Dependent Claim
24 words
CLAIM 89. The method of claim 88 further comprising the step of: in response to said torque analysis signal, generating a torque analysis log.
Claim 90
Dependent Claim
15 words
CLAIM 90. A torque analysis log produced in accordance with the method of claim 89.
Claim 91
Dependent Claim
23 words
CLAIM 91. The method of claim 88 wherein said derivable formation properties comprises properties representative of the mechanical process of drilling the borehole.
Claim 92
Dependent Claim
35 words
CLAIM 92. The method of claim 91 wherein said properties representative of the mechanical process of drilling the borehole include weight on bit (WOB), bit torque (TOR), bit revolutions (RPM) and rate of penetration (ROP).
Claim 93
Dependent Claim
38 words
CLAIM 93. The method of claim 89 wherein said abnormal torque log comprises the following relationship: torque analysis log = TOR a - TOR e where, TOR a = measured bit torque, TOR e = expected bit torque.
Claim 94
Dependent Claim
61 words
CLAIM 94. A method for investigating properties of subsurface formations traversed by a borehole, the method comprising the steps of: generating while drilling a plurality of signals indicative of formation properties derivable from measurements made while drilling; in response to said plurality of signals, generating a bearing bear signal; and in response to said bearing wear signal, optimizing the drilling process.
Claim 95
Dependent Claim
24 words
CLAIM 95. The method of claim 94 further comprising the step of: in response to said bearing wear signal, generating a bearing wear log.
Claim 96
Dependent Claim
22 words
CLAIM 96. The method of claim 95 further comprising the step of: in response to said bearing wear signal, replacing the bit.
Claim 97
Dependent Claim
15 words
CLAIM 97. A bearing wear log produced in accordance with the method of claim 95.
Claim 98
Dependent Claim
23 words
CLAIM 98. The method of claim 94 wherein said derivable formation properties comprises properties representative of the mechanical process of drilling the borehole.
Claim 99
Dependent Claim
35 words
CLAIM 99. The method of claim 98 wherein said properties representative of the mechanical process of drilling the borehole include weight on bit (WOB), bit torque (TOR), bit revolutions (RPM) and rate of penetration (ROP).
Claim 100
Dependent Claim
104 words
CLAIM 100. The method of claim 95 wherein said bearing wear log comprises the following relationship when plotted as a function of depth: bearing wear log = K L1 ((TOR e / (TOR a ROP / (WOB² RPM)))₁ + (TOR e / (TOR a ROP / (WOB² RPM )))₂ + ... where, TOR e = bit torque expected, TOR a ROP / (WOB² RPM) = drilling response, L1 = depth interval over which ROP is measured, K = a constant depending on bearing wear, TOR a = measured bit torque, ROP = rate of penetration, WOB = weight on bit, RPM = bit revolutions.
Claim 101
Dependent Claim
77 words
CLAIM 101. A method for investigating properties of subsurface formations traversed by a borehole, the method comprising the steps of: generating while drilling a plurality of signals indicative of formation properties derivable from measurements made while drilling; in response to said plurality of signals, generating a normalized torque signal; in response to said plurality of signals, generating a rock drillability signal; in response to said normalized torque signal and said rock drillability signal, optimizing the drilling process.
Claim 102
Dependent Claim
23 words
CLAIM 102. The method of claim 101 wherein said derivable formation properties comprises properties representative of the mechanical process of drilling the borehole.
Claim 103
Dependent Claim
35 words
CLAIM 103. The method of claim 102 wherein said properties representative of the mechanical process of drilling the borehole include weight on bit (WOB), bit torque (TOR), bit revolutions (RPM) and rate of penetration (ROP).
Claim 104
Dependent Claim
35 words
CLAIM 104. The method of claim 101 wherein said normalized torque comprises the following relationship: normalized torque = TOR / (WOB D) where: TOR = bit torque, WOB = bit revolutions, D = bit diameter.
Claim 105
Dependent Claim
43 words
CLAIM 105. The method of claim 101 wherein said rock drillability signal comprises the following relationship: rock drillability = ROP D / (WOB RPM) where: ROP = rate of penetration, D = bit diameter, WOB = weight on bit, RPM = bit revolutions.
Claim 106
Dependent Claim
84 words
CLAIM 106. The method of claim 101 wherein said rock drillability signal and said normalized torque signal comprise the following linear relationship: TOR / (WOB D) = S₁(f(η)) + S₂ (ROP D / (WOB RPM)) where, TOR / (WOB D) = normalized torque, ROP D / (WOB RPM) = rock drillability, TOR = bit torque, WOB = weight on bit, D = bit diameter, ROP = bit revolutions, RPM = bit revolutions, S₁ = y intercept, S₂ = slope, f(η) = bit wear function.
Claim 107
Dependent Claim
96 words
CLAIM 107. The method of claim 106 wherein said y intercept comprises the following relationship for a drag bit: S₁ = (µ e / 4) cos (φ) where, µ e = effective coefficient of friction between the bit and the formation, φ = side rake angle for the bit; and wherein said slope comprises the following relationship; S₂ = (τ /8 c1) (1- µ e (σ / τ)) (tan(ϑ) c1) where, τ = insitu shear strength, c1 = a constant, σ = insitu rock strength, ϑ = back rake angle for the bit, f(η) = 1.
Claim 108
Dependent Claim
108 words
CLAIM 108. The method of claim 106 wherein said slope comprises the following relationship for an impact bit: S₂ = (σ tan(ϑ)) / (8 tan(δ)) where, ϑ = half wedge angle for the tooth, σ = insitu rock strength, δ = angle of failure for the formation; and wherein said y intercept comprises the following relationship; S₁ = (α1 c2 / 4) (η((τ/σ) (1/(c1 tan(ϑ))) - tan(ϑ) / tan(δ)) + µ (1-η)) where, α1 = is a factor dependent on rock and bit, c2 = a bit constant, η = bit wear factor, τ = insitu shear strength, c1 = a proportionality constant, µ = coefficient of friction.
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