1. Lesson 35 Wellbore Surveying Methods
PETE 411 Well Drilling
Lesson 35 Wellbore Surveying Methods

2. Wellbore Surveying Methods
Average Angle
Balanced Tangential
Minimum Curvature
Radius of Curvature
Tangential
Other Topics
Kicking off from Vertical
Controlling Hole Angle

3. Read: Applied Drilling Engineering, Ch.8 (~ first 20 pages)
Projects: Due Monday, December 9, 5 p.m. ( See comments on previous years’ design projects )

4. Homework Problem #18 Balanced Cement Plug
Due Friday, December 6

5. I, A, DMD

6. Example - Wellbore Survey Calculations
The table below gives data from a directional survey.
Survey Point Measured Depth Inclination Azimuth
along the wellbore Angle Angle
ft I, deg A, deg
A 3,
B 3,
C 3,
D 4,
Based on known coordinates for point C we’ll calculate the coordinates of point D using the above information.

7. Example - Wellbore Survey Calculations
Point C has coordinates:
x = 1,000 (ft) positive towards the east
y = 1,000 (ft) positive towards the north
z = 3,500 (ft) TVD, positive downwards C C
N (y) N Dz Dz D D Dy
E (x) Dx

8. Example - Wellbore Survey Calculations
I. Calculate the x, y, and z coordinates of points D using:
(i) The Average Angle method
(ii) The Balanced Tangential method
(iii) The Minimum Curvature method
(iv) The Radius of Curvature method
(v) The Tangential method

9. The Average Angle Method
Find the coordinates of point D using
the Average Angle Method
At point C, x = 1,000 ft
y = 1,000 ft
z = 3,500 ft

10. The Average Angle MethodC
N (y) C Dz D N Dz D
E (x) Dy Dx

11. The Average Angle Method

12. The Average Angle Method
This method utilizes the average of I1 and I2 as an inclination, the average of A1 and A2 as a direction, and assumes the entire survey interval (DMD) to be tangent to the average angle.
From: API Bulletin D20. Dec. 31, 1985

13. The Average Angle Method

14. The Average Angle Method

15. The Average Angle Method
At Point D,
x = 1, = 1, ft
y = 1, = 1, ft
z = 3, = 3, ft

16. The Balanced Tangential Method
This method treats half the measured distance (DMD/2) as being tangent to I1 and A1 and the remainder of the measured distance (DMD/2) as being tangent to I2 and A2.
From: API Bulletin D20. Dec. 31, 1985

17. The Balanced Tangential Method

18. The Balanced Tangential Method

19. The Balanced Tangential Method

20. The Balanced Tangential Method
At Point D,
x = 1, = 1, ft
y = 1, = 1, ft
z = 3, = 3, ft

21. Minimum Curvature Methodb

22. Minimum Curvature Method
This method smooths the two straight-line segments of the Balanced Tangential Method using the Ratio Factor RF.
(DL= b and must be in radians)

23. Minimum Curvature Method
The Dogleg Angle, b, is given by:
cos b =
b = 20.67o = radians

24. Minimum Curvature Method
The Ratio Factor,

25. Minimum Curvature Method

26. Minimum Curvature Method

27. Minimum Curvature Method

28. Minimum Curvature Method
At Point D,
x = 1, = 1, ft
y = 1, = 1, ft
z = 3, = 3, ft

29. The Radius of Curvature Method

30. The Radius of Curvature Method

31. The Radius of Curvature Method

32. The Radius of Curvature Method
At Point D,
x = 1, = 1, ft
y = 1, = 1, ft
z = 3, = 3, ft

33. The Tangential Method

34. The Tangential Method

35. The Tangential Method

36. Summary of Results (to the nearest ft)
x y z
Average Angle , , ,878
Balanced Tangential 1, , ,877
Minimum Curvature 1, , ,881
Radius of Curvature 1, , ,878
Tangential Method 1, , ,865

39. Building Hole Angle

40. Holding Hole Angle

42. CLOSURE
(HORIZONTAL) DEPARTURE
LEAD ANGLE

43. b

44. Tool Face Angle