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pete 661 drilling engineering

7. Abnormal Pressure. 661. Drilling Engineering. Slide 2. Abnormal Pressure - Definition, Causes -. Normal Pore Pressures Abnormal Pore Pressure Gradients Fracture Gradients Mud Weights Casing Seat Depths What Causes Abnormal Pressure?. . 7. Abnormal Pressure. 661. Drilling Engineering.

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pete 661 drilling engineering

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    1. 7. Abnormal Pressure 661. Drilling Engineering Slide 1 PETE 661

    2. 7. Abnormal Pressure 661. Drilling Engineering Slide 2 Abnormal Pressure - Definition, Causes - Normal Pore Pressures Abnormal Pore Pressure Gradients Fracture Gradients Mud Weights Casing Seat Depths What Causes Abnormal Pressure?

    3. 7. Abnormal Pressure 661. Drilling Engineering Slide 3 HW # 5 Casing Design Due 10-10-03

    4. 7. Abnormal Pressure 661. Drilling Engineering Slide 4

    5. 7. Abnormal Pressure 661. Drilling Engineering Slide 5 Pore Pressure vs. Depth

    6. 7. Abnormal Pressure 661. Drilling Engineering Slide 6

    7. 7. Abnormal Pressure 661. Drilling Engineering Slide 7

    8. 7. Abnormal Pressure 661. Drilling Engineering Slide 8 Some Causes of Abnormal Pressure 1. Incomplete compaction of sediments Fluids in sediments have not escaped and are still helping to support the overburden.

    9. 7. Abnormal Pressure 661. Drilling Engineering Slide 9 Some Causes of Abnormal Pressure 3. Aquifers in Mountainous Regions Aquifer recharge is at higher elevation than drilling rig location.

    10. 7. Abnormal Pressure 661. Drilling Engineering Slide 10

    11. 7. Abnormal Pressure 661. Drilling Engineering Slide 11

    12. 7. Abnormal Pressure 661. Drilling Engineering Slide 12

    13. 7. Abnormal Pressure 661. Drilling Engineering Slide 13

    14. 7. Abnormal Pressure 661. Drilling Engineering Slide 14

    15. 7. Abnormal Pressure 661. Drilling Engineering Slide 15

    16. 7. Abnormal Pressure 661. Drilling Engineering Slide 16 Indications of Abnormal Pore Pressures Methods: 1. Seismic data 2. Drilling rate 3. Sloughing shale 4. Gas units in mud 5. Shale density 6. Chloride content

    17. 7. Abnormal Pressure 661. Drilling Engineering Slide 17 Indications of Abnormal Pore Pressures

    18. 7. Abnormal Pressure 661. Drilling Engineering Slide 18 Prediction and Detection of Abnormal Pressure Zones 1. Before drilling Shallow seismic surveys Deep seismic surveys Comparison with nearby wells

    19. 7. Abnormal Pressure 661. Drilling Engineering Slide 19 Prediction and Detection of Abnormal Pressure Zones 2. While drilling Drilling rate, gas in mud, etc. etc. D - Exponent DC - Exponent MWD - LWD Density of shale (cuttings)

    20. 7. Abnormal Pressure 661. Drilling Engineering Slide 20 Prediction and Detection of Abnormal Pressure Zones 3. After drilling Resistivity log Conductivity log Sonic log Density log

    21. 7. Abnormal Pressure 661. Drilling Engineering Slide 21

    22. 7. Abnormal Pressure 661. Drilling Engineering Slide 22

    23. 7. Abnormal Pressure 661. Drilling Engineering Slide 23 D - Exponent The drilling rate equation:

    24. 7. Abnormal Pressure 661. Drilling Engineering Slide 24 D - Exponent If we assume that K = 1 and E = 1 Then

    25. 7. Abnormal Pressure 661. Drilling Engineering Slide 25 D - Exponent A modified version of this equation follows:

    26. 7. Abnormal Pressure 661. Drilling Engineering Slide 26 Example Calculate the value of the d - exponent if the drilling rate is 35 ft/hr, the rotary RPM is 100, and the weight on the 12 1/4” bit is 60,000 lbs.

    27. 7. Abnormal Pressure 661. Drilling Engineering Slide 27 Example What happens to d if R doubles to 70 ft/hr? Note that an increase in R resulted in a decrease in d. Doubling R decreased d from 1.82 to 1.57

    28. 7. Abnormal Pressure 661. Drilling Engineering Slide 28 Example d may be Corrected for mud density as follows:

    29. 7. Abnormal Pressure 661. Drilling Engineering Slide 29 Procedure for Determining Pore Pressure From dc - Exponent Calculate dc over 10-30 ft intervals Plot dc vs depth (use only date from Clean shale sections) Determine the normal line for the dc vs. depth plot. Establish where dc deviates from the normal line to determine abnormal pressure zone

    30. 7. Abnormal Pressure 661. Drilling Engineering Slide 30

    31. 7. Abnormal Pressure 661. Drilling Engineering Slide 31 Procedure for Determining Pore Pressure From dc - Exponent If possible, quantify the magnitude of the abnormal pore pressure using overlays, or Ben Eaton’s Method

    32. 7. Abnormal Pressure 661. Drilling Engineering Slide 32

    33. 7. Abnormal Pressure 661. Drilling Engineering Slide 33 Shale Density - Mud Cup Method 1. Fill mud cup with shale until the weight is 8.33. 2. Fill to top with water, and record the reading Wtot.

    34. 7. Abnormal Pressure 661. Drilling Engineering Slide 34

    35. 7. Abnormal Pressure 661. Drilling Engineering Slide 35 Pore Pressure from Resistivity Shale resistivity plots may be developed from (i) logs or (ii) cuttings

    36. 7. Abnormal Pressure 661. Drilling Engineering Slide 36 From plot, Rn = 1.55 ohms Robs = 0.80 ohms From Eaton:

    37. 7. Abnormal Pressure 661. Drilling Engineering Slide 37 Prediction of Abnormal Pore Pressure Resistivity of Shale Temperature in the Return Mud Drilling Rate Increase dc - Exponent Sonic Travel Time Conductivity of Shale

    38. 7. Abnormal Pressure 661. Drilling Engineering Slide 38

    39. 7. Abnormal Pressure 661. Drilling Engineering Slide 39

    40. 7. Abnormal Pressure 661. Drilling Engineering Slide 40

    41. 7. Abnormal Pressure 661. Drilling Engineering Slide 41

    42. 7. Abnormal Pressure 661. Drilling Engineering Slide 42

    43. 7. Abnormal Pressure 661. Drilling Engineering Slide 43 Typical Drilling Rate Profiles - Shale The drilling rate in a normally pressured, solid shale section will generally generate a very steady and smooth drilling rate curve. The penetration rate will be steady and not erratic (normally pressured, clean shale).

    44. 7. Abnormal Pressure 661. Drilling Engineering Slide 44 Typical Drilling Rate Profiles Note: If you are drilling overbalanced in a transition it will be very difficult to pick up the transition zone initially. This will allow you to move well into the transition zone before detecting the problem.

    45. 7. Abnormal Pressure 661. Drilling Engineering Slide 45 Typical Drilling Rate Profiles This could cause you to move into a permeable zone which would probably result in a kick. The conditions you create with overbalanced hydrostatic head will so disguise the pending danger that you may not notice the small effect of the drilling rate curve change. This will allow you to move well into that transition zone without realizing it.

    46. 7. Abnormal Pressure 661. Drilling Engineering Slide 46 Determination of Abnormal Pore Pressure Using the dc - exponent From Ben Eaton:

    47. 7. Abnormal Pressure 661. Drilling Engineering Slide 47 Where

    48. 7. Abnormal Pressure 661. Drilling Engineering Slide 48 Example Calculate the pore pressure at depth X using the data in this graph. Assume: West Texas location with normal overburden of 1.0 psi/ft. X = 12,000 ft.

    49. 7. Abnormal Pressure 661. Drilling Engineering Slide 49 Example From Ben Eaton:

    50. 7. Abnormal Pressure 661. Drilling Engineering Slide 50 Example

    51. 7. Abnormal Pressure 661. Drilling Engineering Slide 51 E.S. Pennebaker Used seismic field data for the detection of abnormal pressures. Under normally pressured conditions the sonic velocity increases with depth. (i.e. Travel time decreases with depth) (why?)

    52. 7. Abnormal Pressure 661. Drilling Engineering Slide 52 E.S. Pennebaker Any departure from this trend is an indication of possible abnormal pressures. Pennebaker used overlays to estimate abnormal pore pressures from the difference between normal and actual travel times.

    53. 7. Abnormal Pressure 661. Drilling Engineering Slide 53

    54. 7. Abnormal Pressure 661. Drilling Engineering Slide 54 Ben Eaton also found a way to determine pore pressure from interval travel times. Example: In a Gulf Coast well, the speed of sound is 10,000 ft/sec at a depth of 13,500 ft. The normal speed of sound at this depth, based on extrapolated trends, would be 12,000 ft/sec. What is the pore pressure at this depth? Assume: S/D = 1.0 psi/ft

    55. 7. Abnormal Pressure 661. Drilling Engineering Slide 55 Ben Eaton From Ben Eaton,

    56. 7. Abnormal Pressure 661. Drilling Engineering Slide 56 Ben Eaton From Ben Eaton Note: Exponent is 3.0 this time, NOT 1.2!

    57. 7. Abnormal Pressure 661. Drilling Engineering Slide 57

    58. 7. Abnormal Pressure 661. Drilling Engineering Slide 58

    59. 7. Abnormal Pressure 661. Drilling Engineering Slide 59

    60. 7. Abnormal Pressure 661. Drilling Engineering Slide 60

    61. 7. Abnormal Pressure 661. Drilling Engineering Slide 61 Problem #3 - Solution When a well kicks, the well is shut in and the wellbore pressure increases until the new BHP equals the new formation pressure. At that point influx of formation fluids into the wellbore ceases. Since the mud gradient in the wellbore has not changed, the pressure increases uniformly everywhere.

    62. 7. Abnormal Pressure 661. Drilling Engineering Slide 62

    63. 7. Abnormal Pressure 661. Drilling Engineering Slide 63 At 2,500 ftInitial mud pressure = 0.52 psi/ft * 2,500 ft = 1,300 psiFracture pressure = 0.73 psi/ft * 2,500 ft = 1,825 psi

    64. 7. Abnormal Pressure 661. Drilling Engineering Slide 64

    65. 7. Abnormal Pressure 661. Drilling Engineering Slide 65

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