PETE 661 Drilling Engineering

1. PETE 661Drilling Engineering Lesson 21 Well Control Complications

2. 2 Well Control Complications Volumetric Well Control Lubrication Complications During Conventional Kill Techniques to Reduce Annular Friction

3. 3 HW #12 - due Dec 02, 2002 Review

4. 4 Gas Kick Migration While a well is shut in the casing pressure increase by 1,040 psi in 2 hours. Mud Weight = 10 lb/gal How fast is the kick migrating?

5. 5 Gas Kick Migration How fast is the kick migrating?

6. 6 Volumetric Well Control Non-Circulating method of well control. Allows a gas bubble to migrate to the surface while systematically allowing the bubble to expand. It also maintains the BHP at or above formation pressure Used whenever circulation cannot be used to kill the well.

7. 7 Two situations can be present Drillpipe can be used to monitor pressure Drillpipe cannot be used

8. 8 Drillpipe can be used When Bit is on bottom Bit is not plugged No float in drillstring

9. 9 Drillpipe can be used Procedure Determine a safety margin for the casing pressure (usually 50 - 100 psi above initial stabilized SICP and SIDPP) Determine working margin (50 - 100 psi above safety margin) As bubble migrates, casing pressure will eventually reach the safety margin

10. 10 Drillpipe can be used Procedure Allow the casing pressure to reach the upper limit of the working margin Very slowly bleed a small volume of mud from the annulus (approximately 1/4 bbl) into a calibrated tank. Then close the choke. Let Drillpipe pressure �stabilize�

11. 11 Drillpipe can be used Procedure, cont�d If new SIDPP > Initial SIDPP + Safety margin, repeat bleeding procedure. If SIDPP = Initial SIDPP + Safety margin, stop bleeding and allow casing pressure to increase again. Repeat until circulation can be restored or bubble has reached the surface

12. 12

13. 13 Drillpipe cannot be used Plugged bit Migrating fluid is below the bit (bit is off bottom) Drillpipe has parted or has a hole that is above the influx

14. 14 Drillpipe cannot be used Well closed in on the blind rams Pumps are inoperable and the drillstring is not full of mud Gas has entered the drillstring If drillpipe pressure cannot be used, what can we do?

15. 15 Volumetric Procedure 1. Record the initial SICP 2. Allow the casing pressure to increase by the predetermined safety margin. 3. Allow the casing pressure to further increase by the predetermined working margin.

16. 16 Volumetric Procedure 4. Bleed mud from the choke manifold into a measuring tank while maintaining a relatively stable casing pressure. Continue to bleed mud until the volume in the measuring tank is equivalent to the mud�s HSP of the working margin buildup. The HSP is based on the hole dimensions at the depth of the rising influx.

17. 17 Volumetric Procedure 6. Repeat steps 3 through 5 until choke pressures stabilize, secondary control can be regained, or the influx surfaces. 7. Stop the bleed process if gas exits the choke. Monitor annulus pressures for further buildup.

18. 18 Volumetric Procedure Allowable increase in surface casing pressure = 0.052 * MW * h

19. 19 Example 6.1

20. 20 Example 6.1

21. 21 Example 6.1

22. 22 Example 6.1

23. 23 Example 6.1

24. 24 Example 6.1

25. 25 Example 6.1

26. 26

27. 27

28. 28

29. 29

30. 30 Lubrication Process of replacing gas at the surface of a wellbore with mud. Pump mud into the wellbore Let mud fall Bleed gas Repeat

31. 31 Lubrication

32. 32 Lubrication Procedure Desired decrease in surface casing pressure = 0.052 * MW * h

33. 33 Example 6.2 Consider the final condition in Example 6.1 where all the gas has migrated to the surface. Write a lubrication procedure for replacing the gas with mud.

34. 34 Example 6.2

35. 35 Example 6.2

36. 36 Example 6.2

37. 37 Example 6.2

38. 38 Example 6.2

39. 39 Example 6.2

40. 40 Example 6.2

41. 41 Example 6.2

42. 42 Example 6.2

43. 43 Off Bottom Well Control Volumetric Use same procedure as before Staging in the Hole Entails circulating mud of sufficient density to control BHP at the current position of the bit (off bottom) Tripping in the hole some distance Repeat

44. 44 Off Bottom Well Control

45. 45 Off Bottom Well Control

46. 46 Complication During Conventional Kill

47. 47 Techniques to Reduce Annular Friction Low choke procedure Overkill Mud Weights Spotting a Balanced Heavy-Weight Pill Reverse Circulation Bullheading Dispersing or Segmenting a Gas Kick

48. 48 Low choke procedure Operator intentionally opens the choke to reduce the surface casing pressure. I do not recommend this although some operators choose to use this procedure

49. 49 Overkill Mud Weights

50. 50 Overkill Mud Weights

51. 51 Example 6.6 Estimate the maximum shoe pressure if a 10 ppg mud were used to kill the well and prepare a drillpipe pressure schedule Calculate the pressure at the shoe if the well had to be shut-in at the instant the string was filled with the new mud.

52. 52 Example 6.6

53. 53 Example 6.6

54. 54

55. 55 Example 6.6

56. 56 Spotting a Heavy-Weight Pill

57. 57 Spotting a Heavy-Weight Pill

58. 58 Spotting a Heavy-Weight Pill

59. 59 Spotting a Heavy-Weight Pill

60. 60 Reverse Circulation

61. 61

62. 62

63. 63 Bullheading Pump into a shut-in well and attempt to place the influx back into the formation. Reasons: H2S kicks Inability to circulate on bottom Loss zone below the kick disallows adequate circulation rates for a kill To buy time Inability to withstand the maximum surface pressures during conventional kill

64. 64 Example 6.8

65. 65