1. Directional Drilling and Deviation Control
DRILLING ENGINEERING
CHAPTER # 8
Directional Drilling and Deviation Control

2. Definition Directional Drilling: Deviation Control: X-Y Plane
The process of directing the wellbore along some trajectory to a predetermined target.
Deviation Control:
The process of keeping the wellbore contained within some prescribed limits, relative to inclination angle, horizontal excursion from the vertical or both.
X-Y Plane
X – Plane = direction plane
Y – Plane = inclination plane

3. Purpose of Directional Drilling
Angles
X-Y = Plane X – angle = direction angle
Y-Z = Plane Y – angle = inclination angle
Purpose of Directional Drilling
Res. Under lake (economics, environmental reasons)
Offshore drilling.
Res. beneath population centers.
Res. beneath natural obstruction (mountains) Or severe topographical features.
Sidetracking out of an existing wellbore to bypass an obstruction (fish) or explore additional producing horizons in adjacent sectors.
Relief well to plug a blow out.

4. Inclination and direction planes as a wellbore proceeds in the depth plane.

5. Plan view of a typical oil and gas structure under a lake

6. Typical offshore development platform with directional wells

7. Developing a field under a city using directionally drilled wells

8. Drilling of directional wells where the reservoir is beneath a major surface obstruction

9. Sidetracking around a fish

10. Using an old well to explore for new oil by sidetracking out of the casing and drilling occasionally

11. 7.1 Planning The Directional Well Trajectory
Well path that will intersect given target.
First design propose the various types of paths that can be drilled economically.
Second includes effects of geology on the bottomhole assemblies (BHA) and other factors that could influence the final wellbore trajectory.

12. Types of Trajectories q1 < q3 < q2 < q4
Build and hold trajectory penetrates target at max. build-up angle.
Build-hole and drop (s-shape) penetrate angle vertically
Build-hold drop and/or hold (modified s-shape) penetrates target at angle less than max. inclination angle in the hold section.
Continuous build trajectory inclination angle is increasing.
q1 < q3 < q2 < q4

13. X3 = horizontal departure
g1 = radius of curvature
D3 = TVD true vertical depth
D1 = kick off point TVD
q = rate of inclination angle build up

14. Geometry of build-and-hold type well

15. 7.2 Build and Hold Trajectory
Circumference = 2pr
S=rq
q in radians max. inclination angle
1 radian = 180 o/p = o
1o = p/180 radians
q = degrees per unit length = q/L
= inclination angle build up rate
q = 1o/100ft
r = S /q
r = radius of curvature

16. S = g q
(8.1)

17. To find angle T look at triangle OBA
(8.2)
q = W - T
To find angle T look at triangle OBA
(8.3a)
(8.3b)
To find angle W consider triangle OBC
(8.4)

18. CO = g1
(8.5)
q = W - T

19. (8.6)
Length of the arc section DC (buildup section)
(8.7)

20. Length of CB (Trajectory Path)
Straight at constant inclination angle can be determined from BCO
Total measured depth DM for TVD of D3 is
(8.8)

21. Horizontal departure at end of build up
(8.9)
True Vertical depth at end of build up section
(8.12)

22. Geometry for the build section

23. Measure depth and Horizontal departure before reaching maximum angle along any part of build up.
Consider  intermediate inclination angle 
XN=Horizontal Departure at C
DN=Vertical depth
Consider DOC
(8.10)
(8.11)

24. New measured depth for any part of the build up
(8.13)
New measured depth at TVD of (D*< D3)(D2<D*< D3)
(8.16)
Horizontal Departure X* (X2<X*< X3)
(8.18)

25. For r1 < X3
(8.20)

26. Build-hold-and-drop and hold (modified-S)

27. Directional quadrants and compass measurements

28. Vertical calculation

29. Horizontal calculation

30. Three-dimensional view of a wellbore showing components that comprise the X, Y and Z parts of the trajectory

31. Techniques for making a positive direction change

32. 7.3 Directional Drilling Tools
Stabilizing Tools
The Stiff Hook-Up
The Pendulum Hook-Up
Angle Building Hook-Ups
The Lock-in Hook-Ups
Angle Losing Hook-Ups

33. Directional drilling applications

34. Stabilizing tool

35. The use of stabilizers in directional drilling

36. Other Application of Stabilizing Tools
Key seat Guide
Avoidance of Pressure Differential Sticking
Whip stock
Knuckle Joint

37. Whip stocks

38. Knuckle joint

40. Using a section mill to prepare for a kick-off

41. Jetting bit

42. Jetting a trajectory change

43. Fig 8.95: A typical positive-displacement mud motor (PDM)