Definition

1
DRILLING ENGINEERING
CHAPTER 8
Directional Drilling and Deviation Control
2
Definition

• Directional Drilling
• 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

• 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

• 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

• 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 lt q3 lt q2 lt 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
• Srq
• q in radians max. inclination angle
• 1 radian 180 o/p 57.29578 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
(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 ?
• XNHorizontal Departure at C
• DNVertical 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 (Dlt D3)(D2ltDlt D3)
(8.16)
Horizontal Departure X (X2ltXlt X3)
(8.18)
25

• For r1 lt 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
39
(No Transcript)
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)