1. Lesson 26 * Well Control * * Variable Geometry *
PETE 411 Well Drilling
Lesson 26 * Well Control * * Variable Geometry *

2. Well Control-Variable Geometry
Initial Shut-In Conditions
Driller’s Method
Kick at Casing Seat
Kick at Surface
Wait and Weight Method

3. Read: Applied Drilling Engineering, Ch. 4
HW #14: Driller’s Method - due HW #15: W&W Method - due
Quiz B Thursday, Nov. 14, p.m. Rm. 101 Closed Book 1 Equation sheet allowed, 8 1/2”x 11” (both sides)

4. Example Problem
1. Determine the pressure at the casing seat at 4,000’ when using the old mud (Driller’s) versus using the kill mud (Wait and Weight) to circulate a gas kick out of the hole.
2. Determine the casing pressure at the surface when the top of the gas bubble has just reached the surface, for the same two mud weights used above.

5. Example Problem Mud Weight = 10 ppg
Well depth = 10,000’
Hole size = 10.5”
Drill pipe = 4.5”, #/ft
Drill Collars = 8” * 3.5” * 500 ft
Surface casing = 4,000’, 13-3/8”, 68 #/ft
Mud Weight = 10 ppg
Fracture 4,000’ = 0.7 psi/ft

6. Example Problem Shut in Annulus Pressure, SICP = 400 psi
Shut in Drillpipe Pressure, SIDPP = 200 psi
Pit level increase = 20 barrels (kick size)
Drop the Z terms but consider Temperature
T at surface = 70 deg. F
Temperature gradient = 1.2 deg.F/100 ft

7. Initial (Closed-In) Conditions:
Initial mud gradient = psi/ft
(0.052 * 10 = 0.520)

8. Initial (Closed-In) Conditions:
( ft/bbl )

9. 4,000’ 9,500’ vdp.csg = 0.13006 bbl/ft vdp,hole = 0.08743 bbl/ft
10,000’
vdp,hole = bbl/ft
vdc,hole = bbl/ft

11. Driller’s Method - kick at bottom
F = DP * A = W

13. Driller’s Method - kick at csg. seat
What is the pressure at 4,000 ft when the top of the kick fluid first reaches that point?

14. Top of Kick at Casing Seat
Driller’s Method
Top of Kick at Casing Seat
4,000’
9,500’
10,000’
P = 5,400 psi

15. Driller’s Method - kick at csg. seat
Again,
DP K_4,000 = psi

16. Driller’s Method - kick at csg. seat

17. Driller’s Method - kick at csg. seat
This results in the quadratic Eqn:
With the solutions:

18. Driller’s Method - Top of Kick at Casing Seat
P0,ann = ?
P4,000 = 2,493 psi
h4,000 = 441 ft
DP = 16 psi
BHP = 5,400 psi

19. Driller’s Method Top of Kick at Surface
4,000’
9,500’
10,000’
We need two equations…
BHP = 5,400 psi

20. Driller’s Method - kick at surface
When the bubble rises, it expands. The volume of the bubble at the surface is given by:
(Z = const.)

21. Driller’s Method - kick at surface

22. Driller’s Method - kick at surface
From Eq. (2),
But, from Eq. (1),

23. Driller’s Method - kick at surface
So,
Quadratic equation . . .

24. Driller’s Method - kick at surface

25. Driller’s Method - kick at surface
( = 0.57 psi/ft )

26. Driller’s Method. Top of Kick at Surface
P0,ann = 695 psi
h0 = 974 ft
DPK,0 = 11 psi
P 4,000 = 2,280 psi
P10,000 = ?

27. Wait and Weight Method - kick at casing seat
Calculate the pressure at 4,000 ft when the top of the bubble reaches this point.
Volume of bubble at 4,000 ft

28. Top of Kick at Casing Seat
Wait and Weight Method
Top of Kick at Casing Seat
Old Mud
Kill Mud

29. W&W - Pressure at top of kick at 4,000 ft
Also,

30. Wait and Weight Method - kick at surface
Capacity inside drill string
= DP_cap. + DC_cap.

31. W&W - Pressure at top of kick - kick at 4,000 ft

32. W&W - Pressure at top of kick - kick at 4,000 ft

33. W&W - Pressure at top of kick - kick at 4,000 ft

34. Wait and Weight Method Top of Kick at Surface
4,000’
9,500’
10,000’
Old Mud
Kill Mud

35. Wait and Weight Method - kick at surface
Volume of gas bubble at surface:

36. Wait and Weight Method (Engineer’s Method) - kick at surface
As before,
Assume all 10 lb/gal mud is inside the /8” csg. Then the height of 10 lb mud:

37. Wait and Weight Method (Engineer’s Method) - kick at surface
Hydrostatic head across the mud columns:
Old Mud:
Kill Mud:

38. Hydrostatics in Annulus W&W Method - kick at surface

39. Wait and Weight Method kick at surface
From Eq. 4, substituting for h0

40. Wait and Weight Method - kick at surface
Height of Bubble at Surface

41. Check Pressure at 4,000 ft - kick at surface
Looks OK

42. Wait and Weight Method Top of Kick at Surface
Old Mud
P0,ann = 611 psi
Kill Mud
h0 = 1,109 ft
DPK,0 = 11 psi
DPOld Mud = 569 psi
P 4,000 = 2,161 psi
P10,000 = ?

43. Driller’s Engineer’s Method Method
Summary
Bubble at 10,000 ft
Driller’s Engineer’s
Method Method

44. Summary
Top of Bubble at 4,000 ft
Driller’s Engineer’s
Method Method

45. Top of Bubble at surface
Summary
Top of Bubble at surface
Driller’s Engineer’s
Method Method

47. Why the difference?

48. Maximum Casing Pressure, psi
Wait and Weight Method
Kick Intensity, ppg

49. Kick Intensity, ppg
Casing Pressure, psi
Pump Strokes

50. Casing Pressure, psi
Volume of Mud Pumped, bbl