Transcript Document 7279146

DRILLING ENGINEERING
CHAPTER # 8
Directional Drilling and
Deviation Control
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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

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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.

3
Inclination and direction planes as a wellbore proceeds in
the depth plane.
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Plan view of a typical oil and gas structure under a lake
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Typical offshore development platform with directional
wells
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Developing a field under a city using directionally drilled
wells
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Drilling of directional wells where the reservoir is
beneath a major surface obstruction
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Sidetracking around a fish
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Using an old well to explore for new oil by sidetracking
out of the casing and drilling occasionally
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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.
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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 < q3 < q2 < q4
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
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X3 = horizontal departure
g1 = radius of curvature
D3 = TVD true vertical depth
D1 = kick off point TVD
q = rate of inclination angle build up
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Geometry of build-and-hold type well
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7.2 Build and Hold Trajectory

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Circumference = 2pr
S=rq
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
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S=gq
1
g

q
S

deg rees
q
length
1  length 
g  

q  deg rees 
1  length   180 
g  
 

q  deg rees   p 
180 1 
180 
 or q 

g1 
p q
g 1p 
(8.1)
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 q=W-T
(8.2)
 To find angle T look at triangle OBA
BA g 1 - X 3
tan T 

AO D3 - D1
T  arctan
g1 - X3
D3 - D1
(8.3a)
(8.3b)
To find angle W consider triangle OBC
CO
SinW 
BO
(8.4)
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CO = g1
BO  (OA) 2  ( BA) 2
BO  ( D3 - D1 )2  (g 1 - X 3 )2
SinW 
g1
(g 1 - X 3 )  ( D3 - D1 )
2
(8.5)
2

g1
W  arcsin 
 (g - X )2  ( D - D )2
1
3
3
1





q=W-T
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
g1

q  arcsin
 (g - X )2  ( D - D )2
1
3
3
1


 - arctan  g 1 - X 3 
D -D 

1
 3

(8.6)
Length of the arc section DC (buildup section)
DC  r1q
p
p
180
1
r1

180 q
DC 
q
q
(8.7)
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Length of CB (Trajectory Path)
Straight at constant inclination angle can be
determined from BCO
CO
r1
tan W 

CB CB
r1
CB 
tan W
Total measured depth DM for TVD of D3 is
q
r1
Dm  D1  
q tan W
(8.8)
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Horizontal departure at end of build up
X 2  EC
consider DOC
X 2  r1 - r1 cosq  r1 (1 - cosq )
(8.9)
True Vertical depth at end of build up section
D2  D1 - r1 sin q
(8.12)
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Geometry for the build section
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Measure depth and Horizontal departure before reaching
maximum angle along any part of build up.
Consider q intermediate inclination angle q
XN=Horizontal Departure at C
DN=Vertical depth
Consider DOC
DN  D1 - r1 sin q
(8.10)
X N  r1 - r1 cosq
X N  r1 (1 -1 cosq )
(8.11)
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New measured depth for any part of the build up
DMN  D1 
q
(8.13)
q
New measured depth at TVD of (D*< D3)(D2<D*< D3)
DMP
q
 D - D1 - r1 sin q
 D1   
q 
cosq




(8.16)
Horizontal Departure X* (X2<X*< X3)
X   r(1 - cosq )  ( D - D1 - r1 sin q ) tan q
(8.18)
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For r1 < X3
D3 - D1
r1
q  180 - arcTan (
) - arcCos(
)
X 3 - r1
D3 - D1

D3 - D1 
 sin arcTan (
)
X 3 - r1 

(8.20)
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Build-hold-and-drop and hold (modified-S)
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Directional quadrants and compass measurements
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Vertical calculation
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Horizontal calculation
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Three-dimensional view of a wellbore showing components that
comprise the X, Y and Z parts of the trajectory
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Techniques for making a positive direction change
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7.3 Directional Drilling Tools
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Stabilizing Tools
The Stiff Hook-Up
The Pendulum Hook-Up
Angle Building Hook-Ups
The Lock-in Hook-Ups
Angle Losing Hook-Ups
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Directional drilling applications
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Stabilizing tool
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The use of stabilizers in directional drilling
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Other Application of Stabilizing Tools
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Key seat Guide
Avoidance of Pressure Differential Sticking
Whip stock
Knuckle Joint
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Whip stocks
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Knuckle joint
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Using a section mill to prepare for a kick-off
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Jetting bit
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Jetting a trajectory change
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Fig 8.95: A typical positive-displacement mud motor
(PDM)
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