®

DELIVERING KNOWLEDGE. DEVELOPING COMPETENCE.

INTRODUCTION
Directional drilling is the art and science
involving the intentional deflection of a
wellbore in a specific direction in order to
reach a predetermined objective below the
surface of the earth
Introduction

At one time it was thought that all

wells were vertical
Methods to measure deviation were
developed in the 1920’s (initially acid
bottle)
Directional drilling developed after
1929 when new survey instruments
were available (inclination and
direction)

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Introduction

The first controlled directionally

drilled well was drilled in the
Huntington Beach Field in 1930 to
tap offshore reserves from land
locations
Directional drilling became more
widely accepted after a relief well
was drilled near Conroe, Texas in
1934

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Introduction

Today, directional drilling is an integral

part of the petroleum industry
It enables oil companies to produce
reserves that would not be possible
without directional drilling

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Introduction

One of the
primary uses of
directional
drilling was to
sidetrack a well
even if it was to
go around a
stuck BHA

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Introduction

Sometimes
multiple sidetracks
are used to better
understand
geology or to place
the wellbore in a
more favorable
portion of the
reservoir

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 Introduction
Straight hole drilling
is a special
application of
directional drilling
ØTo keep from crossing
lease lines
ØTo stay within the
specifications of a
drilling contract
ØTo stay within the well
spacing requirements
of a developed field

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Introduction

Drilling multiple
wells from a
single structure
or pad
Most offshore
development
would not be
possible without
directional
drilling

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Introduction

Inaccessible
surface location
Drilling in towns,
from land to
offshore and
under
production
facilities

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Introduction

Drilling around
salt domes
Salt can cause
significant drilling
problems and
directional drilling
can be used to
drill under the
overhanging cap

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Introduction

Steeply dipping
sands can be
drilled with a
single wellbore

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Introduction

Fault drilling
In hard rock,
deviation can be a
problem
Sometimes the bit
can track a fault
Drilling at a higher
incident angle
minimizes the
potential for
deflection of the bit

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Introduction

Relief well drilling

Directional
drilling into the
blowout when the
surface location
is no longer
accessible
Very small target
and takes
specialized
equipment
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Introduction

Horizontal
drilling
Increasing
exposure of the
reservoir to
increase
productivity

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Introduction

Multilateral
drilling
Drilling more
than one
wellbore from a
single parent
wellbore

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Introduction

Extended reach
drilling wells are
characterized by
high inclinations
and large
departures in
the horizontal
plane

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Introduction

Extended reach wells are wellbores

where the horizontal departure is
significantly higher than the true
vertical depth of the well, which is
the horizontal departure – TVD ratio
(HD/TVD)
Extended reach wells have been
drilled with HD/TVD ratios greater the
6/1.

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Introduction

Maersk Oil has drilled the longest ERD

wellbore with 40,320’ (12,290m) at Al
Shaheen Field, offshore Qatar. 35,770’
(10,903m) of the wellbore was horizontal
in the producing zone. The true vertical
depth of the reservoir is 3845’ (1172m ).
HD/TVD is 10.49

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Introduction

BP drilled a well at Wytch Farm with a

measured depth of 37,001’ (11,278 m), a
TVD of 5,371’ (1,637 m) and horizontal
departure of 35,197’ (10,723 m). HD/TVD
6.55
Total drilled a well in Tierra del Fuego
with a measured depth of 36,693’
(11,184m), a TVD of 5434’ (1656m) and a
horizontal departure of 34,728’ (10,585m).
HD/TVD 6.39

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Introduction

There are four basic hole patterns

Not all wells conform to the basic
hole patterns and may be a
combination of patterns
ØBuild and hold
ØBuild, hold drop (S curve)
ØContinuous build
ØHorizontal

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 True Vertical Depth (m)
0
25
0
500
ERD Wells 750
1000
with 1250
significant 1500
1750
azimuth 2000
Final
change(s) Wellbore
2250

Highly
engineered
well plan
required
Pilot Hole

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Introduction

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Introduction

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 ®

DELIVERING KNOWLEDGE. DEVELOPING COMPETENCE.

SURVEY CALCULATIONS

Survey calculations are used to predict

the position of the wellbore relative to the
surface location
Survey Calculations

Terminology used in this book

ØMD = Measured depth – Length of the
wellbore measured by the drill string
ØTVD = True vertical depth – Vertical
component of the measured depth
ØN = North component of the horizontal
departure

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∆

Survey Calculations

ØE = East component of the horizontal

displacement
Ø = Delta meaning the difference in
ØSubscript 1 = The upper survey of two
survey points
ØSubscript 2 = The lower survey of the lower
survey point
ØI = Inclination from vertical

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Survey Calculations

ØA = Azimuth of the survey (0 to 360

degrees)
Ør = Radius of curvature
ØVS = Vertical section
ØDLS = Dogleg severity
ØDEP = The departure in the horizontal
plane

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Survey Calculations

KB, RT, DF
Common
KOP
terminology for
a directional Build Section
EOB or EOC
profile

TVD, ft
Tangent or Hold

Drop
Section

Vertical Section, ft
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Survey Calculations

Most common survey methods

ØTangential
ØBalanced Tangential
ØAverage Angle
ØRadius of Curvature
ØMinimum Curvature

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Survey Calculations

Tangential method uses only the

lower survey point and is the least
accurate survey method

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Survey Calculations

The tangential method assumes the

wellbore course is a straight line
tangent to the lower inclination or
azimuth
Tangential method equations

∆TVD = ∆MD × Cos I 2

∆N = ∆MD × Sin I 2 × Cos A2
∆E = ∆MD × Sin I 2 × Sin A2

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Survey Calculations

The balanced tangential survey

method assumes the wellbore course
is two straight lines with half the
wellbore course tangent to the upper
survey point and the other half to the
lower survey point

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Survey Calculations

The balance tangential is an accurate

survey method but seldom used
Balanced tangential equations

∆MD
∆TVD = (Cos I1 + Cos I 2 )
2
∆MD
∆N = [(Sin I1 × Cos A1 ) + (Sin I 2 × Cos A2 )]
2
∆MD
∆E = [(Sin I1 × Sin A1 ) + (Sin I 2 × Sin A2 )]
2
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Survey Calculations

The average angle method assumes

the wellbore course is a straight line
tangent to the average angle

I1

I1 + I 2
2

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Survey Calculations

The average angle method is

accurate as long as the surveys are
not too far apart and there is no large
change in azimuth at low angles
Average angle equations
 I + I2 
∆TVD = ∆MD × Cos 1 
 2 
I +I   A + A2 
∆N = ∆MD × Sin 1 2  × Cos 1 
 2   2 
I +I   A + A2 
∆E = ∆MD × Sin 1 2  × Sin 1 
 2   2 
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Survey Calculations

Radius of curvature assumes that the

wellbore course is an arc of a circle
Used for planning but not for final
survey

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Survey Calculations

Radius of curvature has problems

when inclinations and azimuths are
equal because the radius of
curvature is infinite
Radius of curvature also has
problems when the well walks past
north

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Survey Calculations

Radius of curvature equations

∆TVD =
(180 )(∆MD )(Sin I 2 − Sin I 1 )
π (I 2 − I 1 )

∆N =
(180 ) (∆MD )(Cos I1 − Cos I 2 )(Sin A2 − Sin A1 )
2

π 2 (I 2 − I1 )( A2 − A1 )
180 2 (∆MD )(Cos I1 − Cos I 2 )(Cos A1 − Cos A2 )
∆E =
π 2 (I 2 − I1 )( A2 − A1 )
180( ∆MD)(CosI1 − CosI 2 )
∆DEP =
π ( I 2 − I1 )
I 2 − I1 r=
180
∆MD =
Br (π )( DLS )
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Survey Calculations

Minimum Curvature is the balanced

tangential method but the straight
lines are smoothed into an arc by a
correction factor

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Survey Calculations

Minimum curvature is suitable for a

computer or programmable
calculator
The inclinations and azimuths must
be changed to radians before
entering them in the equations
It is considered the most accurate
survey method

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Survey Methods

Minimum curvature equations

 ∆MD 
∆TVD =   (Cos I1 + Cos I 2 )( FC )
 2 
 ∆MD 
∆N =  [(Sin I 2 × Cos A2 ) + (Sin I1 × Cos A1 )](FC )
 2 
 ∆MD 
∆E =  [(Sin I 2 × Sin A2 ) + (Sin I1 × Sin A1 )](FC )
 2 
D1 = Cos (I 2 − I 1 ) − {Sin I 2 × Sin I 1 × [1 − Cos ( A2 − A1 )]}

 1 
D 2 = Tan −1  2  − 1
 D1 
2  D2 
FC = × Tan 
D2  2 
§ Note: inclination and azimuth must be entered in
radians
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Survey Methods

Example 12-1 on page 12-10

MD1 = 1000’ MD2 = 1062’

I1 = 10° I2 = 11.5°
A1 = 140° A2 = 143°
TVD1 = 943.13’
N1 = -110.26’
E1 = 86.32’

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Survey Methods

Class Problem Page 12-37

ØGiven the following two surveys, calculate
the ΔTVD, ΔN and the ΔE using the
average angle method and the radius of
curvature method
MD1 = 100’ MD2 = 200’
I1 = 1o I2 = 1.01o
A1 = 0o A2 = 180o

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Survey Methods

RESULTS

Method ΔTVD ΔN ΔE
Average Angle 99.98 0.00 1.75
Radius of Curv. 99.98 0.00 1.12
Minimum Curv. 99.99 -0.01 0.00

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Survey Calculations

AVERAGE ANGLE METHOD

 I1 + I 2 
∆TVD = ∆MD × Cos 
 2 

 1 + 1.01 
( )
∆TVD = 200 − 100 × Cos  = 99.98
 2 

I +I   A + A2 
∆N = ∆MD × Sin 1 2  × Cos 1 
 2   2 

 1 + 1.01   0 + 180 
∆N = (200 − 100 )× Sin  × Cos  = 0.00
 2   2 

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Survey Calculations

AVERAGE ANGLE METHOD

I +I   A + A2 
∆E = ∆MD × Sin 1 2  × Sin 1 
 2   2 

 1 + 1.01   0 + 180 
∆E = (200 − 100 )× Sin  × Sin   = 1.75
 2   2 

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Survey Calculations

RADIUS OF CURVATURE METHOD

∆TVD =
(180 )(∆MD )(Sin I 2 − Sin I 1 )
π (I 2 − I 1 )

∆TVD =
(180 )(200 − 100 )(Sin(1.01) − Sin(1))
= 99.98
π (1.01 − 1)

∆N =
(180 ) (∆MD )(Cos I1 − Cos I 2 )(Sin A2 − Sin A1 )
2

π 2 (I 2 − I1 )( A2 − A1 )

∆N =
(180 ) (200 − 100 )(Cos(1) − Cos(1.01))(Sin(180 ) − Sin(0 ))
2
= 0.00
π (1.01 − 1)(180 − 0 )
2

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Survey Calculations

RADIUS OF CURVATURE METHOD

180 2 (∆MD )(Cos I1 − Cos I 2 )(Cos A1 − Cos A2 )

∆E =
π 2 (I 2 − I1 )( A2 − A1 )

180 2 (200 − 100 )(Cos (1) − Cos (1.01))(Cos (0 ) − Cos (180 ))

∆E = = 1.12
π (1.01 − 1)(180 − 0 )
2

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Survey Methods

MINIMUM CURVATURE METHOD

D1 = Cos (I 2 − I1 ) − {Sin I 2 × Sin I1 × [1 − Cos ( A2 − A1 )]}

D1 = Cos (0.0176 − 0.0175) − {Sin(0.0176)× Sin(0.0175)× [1 − Cos (3.1416 − 0.000)]}

D1 = 0.9994

 1 
D 2 = Tan −1  2  − 1
 D1 

 1 
D 2 = Tan −1
  − 1 = 0.0351
2 
 (0.9994 ) 

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Survey Methods

MINIMUM CURVATURE METHOD

2  D2 
FC = × Tan 
D2  2 

2  0.0351 
FC = × Tan  = 1.000103
0.0351  2 

 ∆MD 
∆TVD =  (Cos I1 + Cos I 2 )(FC )
 2 

 200 − 100 
∆TVD =  (Cos(0.0175) + Cos(0.0176 ))(1.000103)
 2 
∆TVD = 99.99

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Survey Methods

MINIMUM CURVATURE METHOD

 ∆MD 
∆N =  [(Sin I 2 × Cos A2 ) + (Sin I1 × Cos A1 )](FC )
 2 
 200 − 100 
∆N =  [(Sin(0.0176)× Cos(3.1416 )) + (Sin(0.0175)× Cos(0.000 ))](1.000103)
 2 
∆N = −0.01

 ∆MD 
∆E =  [(Sin I 2 × Sin A2 ) + (Sin I1 × Sin A1 )](FC )
 2 
 200 − 100 
∆E =  [(Sin(0.0176)× Sin(3.1416 )) + (Sin(0.0175)× Sin(0.000 ))](1.000103)
 2 
∆E = 0.00

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Survey Methods

RESULTS

Method ΔTVD ΔN ΔE
Average Angle 99.98 0.00 1.75
Radius of Curv. 99.98 0.00 1.12
Minimum Curv. 99.99 -0.01 0.00

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Survey Methods
North

Radius of
Curvature 1.12’ E

Average
Angle 1.75’ E
West East

Minimum
Curvature 0.01 S

South
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Survey Calculations

Closure distance and direction is the

North and East coordinate expressed
as polar coordinates rather than
rectangular coordinates
Closure distance is a2 + b2 = c2

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Survey Calculations

Closure distance and direction

equations
ØNote: you must subtract the coordinates of the
surface location from the North and East
before calculating the closure distance and
direction

Closure Distance = ( N ) + (E ) 2 2

E −1
ClosureDirection = Tan  
N

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Survey Calculations

Vertical section is the horizontal length

of a projection of the borehole into a
specific vertical plane and scaled with
the vertical depth

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Survey Calculations

Vertical section equations

VS = Cos( Azvs − Azcl ) × (Closure Distance)

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Survey Calculations

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Survey Calculations

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 True Vertical Depth (m)
0
25
0
500

What do 750
1000

you use 1250

1500

for 1750
2000
Final
Vertical Wellbore
2250

Section
Azimuth

Pilot Hole

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Survey Calculations

Dogleg severity is a measure of the

amount of change in the inclination
and/or azimuth of a borehole, usually
expressed in degrees per 100 feet or
degrees per 30 meters course length

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Survey Calculations

If I1 = 2o, I2 = 4o and ΔMD = 100’, then

the dogleg severity would be
DLS =
(4 − 2) = 20 / 100'
100

If I1 = 2o, I2 = 4o and ΔMD = 50’, then

the dogleg severity would be

DLS =
(4 − 2) 2
x = 40 / 100'
50 2

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Survey Calculations

If I1 = 10o, I2 = 10o, A1 = 10o, A2 = 20o

and ΔMD = 100’, what would the
dogleg severity be?
1.74o/100’

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Survey Calculations

Curvature at 90 degrees

Curvature at 10 degrees

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Survey Calculations

For a change in azimuth, the dogleg

severity is a function of the sine of
the inclination (ΔA x Sin I)

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Survey Calculations

Dogleg severity equations (English

Units)
 100 
Cos {(Sin I 1 × Sin I 2 )[(Sin A1 × Sin A2 ) + (Cos A1 × Cos A2 )] + (Cos I 1 × Cos I 2 )}
−1
DLS = 
 ∆MD 

(2)(100) Sin −1 (Sin I )(Sin I )Sin A2 − A1 

2 2
  I − I 
DLS = 2    +  Sin 2 1 
∆MD
1
  2    2 

In the metric system, replace the 100

with 30

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Survey Calculations

To make it a little easier to understand,

the dogleg severity is approximately
equal to the vectorial sum of the change
in inclination and the change in azimuth
The equation does not work well at low
inclinations
2
  I 2 + I1  
DLS =
100
(I 2 − I1 )2
+ sin  ( A2 − A1 )
∆MD   2  

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Survey Calculations

DLS

( I 2 − I1 ) a +b = c 2 2 2
2
 I +I  
DLS =
100
(I 2 − I1 )2 + sin  2 1 ( A2 − A1 )
∆MD   2  

 I 2 + I1 
sin  ( A2 − A1 )
 2 

The dogleg severity can be estimated by

the above means
© 2010 PetroSkills, LLC. All rights reserved. 68
Survey Calculations

Class Problem Page 12-37

ØCalculate the dogleg severity for the
following surveys

MD1 = 100’ MD2 = 200’

I1 = 1o I2 = 1.01o
A1 = 0o A2 = 180o

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 Survey Calculations

DLS equations
 100 
Cos {(Sin I 1 × Sin I 2 )[(Sin A1 × Sin A2 ) + (Cos A1 × Cos A2 )] + (Cos I 1 × Cos I 2 )}
−1
DLS = 
 ∆MD 

 100 
Cos {(Sin(1)× Sin(1.01))[(Sin(0)× Sin(180)) + (Cos(0)× Cos(180))] + (Cos(1)× Cos(1.01))}
−1
DLS = 
 200 − 100 

DLS = 2.010 / 100'

(2)(100) Sin −1 (Sin I )(Sin I )Sin A2 − A1 

2 2
  I − I 
DLS = 2    +  Sin 2 1 
∆MD
1
  2    2 

(2)(100)
2 2

DLS = Sin −1
(Sin(1))(Sin(1.01))Sin 180 − 0  + Sin 1.01 − 1 
(200 − 100)   2    2 

DLS = 2.010 / 100'

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Survey Calculations

DLS equations
2

DLS =
100
(I 2 − I1 )2 + sin I 2 + I1 ( A2 − A1 )
∆MD   2  
2
  1.01 + 1  
DLS =
100
(1.01 − 1) + sin
2
(180 − 0 )
100   2  
DLS = 3.16 o / 100'

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Survey Calculations

Problems caused by doglegs

ØTorque and drag
ØKeyseats and casing wear
ØFatigue

© 2010 PetroSkills, LLC. All rights reserved. 72

Survey Calculations

Torque and drag

are caused by
the friction
between the drill
string and the
wall of the hole
Higher tension
and doglegs
result in higher
torque and drag

© 2010 PetroSkills, LLC. All rights reserved. 73

Survey Calculations

Keyseats and
casing wear are
caused by the
drill string being
rotated in a
dogleg with
higher tension

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Survey Calculations

Fatigue is
caused by
rotating the drill
string in a bend
The cyclic
stresses cause
fatigue

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Survey Calculations

The endurance
limit is the
amount of
bending stress
that can be
tolerated without
causing fatigue
with no tension

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Survey Calculations

As the amount of tension increases in a

dogleg, the amount of bending that can
be tolerated before causing fatigue
decreases

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 Survey Calculations
4.9

Figure 13-9,
page 13-12 of
Chapter 13
100

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Survey Uncertainty

Directional surveys are not absolute

and the accuracy of the surveys
must be considered
Wolff and DeWardt is one systematic
survey error model used to predict
the ellipse of uncertainty (actually an
ellipsoid since it is in three
dimensions)

© 2010 PetroSkills, LLC. All rights reserved. 79

Survey Uncertainty

Generally, the inclination of a survey

is relatively accurate because it is
only affected by depth measurement
and the accuracy of the tool
The direction of the well is more
inaccurate due to accuracy of the
tools, magnetic interference,
magnetic storms, etc.

© 2010 PetroSkills, LLC. All rights reserved. 80

Survey Uncertainty

As the inclination of the well

increases, the error in the vertical
and horizontal plane increases
Most survey errors are systematic
rather than random which means
they accumulate rather than cancel
each other out

© 2010 PetroSkills, LLC. All rights reserved. 81

Survey Uncertainty

Ellipse of
Uncertainty at
TD showing
possible
location of
wellbore
Spider maps
are used to plot
existing wells
and future
wells
© 2010 PetroSkills, LLC. All rights reserved. 82
Survey Uncertainty

The size of the

ellipse of
uncertainty
increases with
depth

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Survey Uncertainty

While drilling
other wells, we
try to stay out of
the ellipse of
uncertainty of
other wells to
avoid a collision
using a traveling
cylinder
proximity
analysis
© 2010 PetroSkills, LLC. All rights reserved. 84
 ®

DELIVERING KNOWLEDGE. DEVELOPING COMPETENCE.

SURVEY INSTRUMENTS
Survey instruments are used to
measure the inclination and azimuth of
the well
Survey Instruments

Magnetic surveys use the earth’s

magnetic field to determine the azimuth
of the wellbore
ØThe magnetic north pole is not the same as
the geographical north pole

© 2010 PetroSkills, LLC. All rights reserved. 86

Survey Instruments

ØDeclination is the difference between the

magnetic north pole and the geographical
north pole
ØIt is either an east or west declination
ØEast declination is added to the azimuth
ØWest declination is subtracted from the
azimuth

© 2010 PetroSkills, LLC. All rights reserved. 87

Survey Instruments

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Survey Instruments

© 2010 PetroSkills, LLC. All rights reserved. 89

Survey Instruments

© 2010 PetroSkills, LLC. All rights reserved. 90

Survey Instruments

For magnetic survey instruments you

must use non-magnetic (monel) drill
collars
ØThe survey instrument must be placed
within the collars to minimize magnetic
interference
ØNear the middle but not precisely the
middle

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Survey Instruments

ØThe number of collars depends upon the

geographical location of the well
ØWhere the horizontal intensity of the
earth’s magnetic field is a minimum, more
non-mag drill collars will be required

© 2010 PetroSkills, LLC. All rights reserved. 92

Survey Instruments

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Survey Instruments

ØZone I requires fewer non-magnetic drill

collars
ØZone II and Zone III require more non-
magnetic collars
ØThe number of collars also depends upon the
inclination and direction of the well

© 2010 PetroSkills, LLC. All rights reserved. 94

Survey Instruments

ZONE I
© 2010 PetroSkills, LLC. All rights reserved. 95
Survey Instruments

ZONE III

© 2010 PetroSkills, LLC. All rights reserved. 96

Survey Instruments

Significant advances in directional

drilling technology

PDM and Wireline Steerable Rotary Steerable

Bent Sub Steering Tool MWD Motor System

1960 1970 1980 1990 2000

© 2010 PetroSkills, LLC. All rights reserved. 97

Survey Instruments

Types of survey instruments

ØMagnetic
ØGyroscopic

SURVEY INSTRUMENTS

MAGNETIC GYROSCOPIC

COMPASS ELECTRONIC CONVENTIONAL RATE OR RING LASER INERTIAL GRADE

NORTH SEEKING

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Survey Instruments

Compass
ØSingleshot
ØMultishot
ØBoth use a compass and camera
ØThe camera takes a picture of the compass at
various depths within the wellbore

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Survey Instruments

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Survey Instruments

© 2010 PetroSkills, LLC. All rights reserved. 101

Survey Instruments

Types of survey instruments

ØMagnetic
ØGyroscopic

SURVEY INSTRUMENTS

MAGNETIC GYROSCOPIC

COMPASS ELECTRONIC CONVENTIONAL RATE OR RING LASER INERTIAL GRADE

NORTH SEEKING

© 2010 PetroSkills, LLC. All rights reserved. 102

Survey Instruments

Steering Tool
MWD (Measurement While Drilling)
EMS (Electronic Multishot)

© 2010 PetroSkills, LLC. All rights reserved. 103

Survey Instruments

All electronic survey tools use the

same instruments to measure the
inclination and azimuth
ØAccelerometers to measure the inclination
ØMagnetometers to measure the azimuth

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Survey Instruments

The difference is how the instrument

gets the information to the surface
ØSteering tool was the first electronic
instrument and used a single conductor
wireline

© 2010 PetroSkills, LLC. All rights reserved. 105

Survey Instruments

© 2010 PetroSkills, LLC. All rights reserved. 106

Survey Instruments

The steering tool is

oriented in a mule
shoe sub (UBHO
sub). The key in the
MSS is aligned with
the bend in the
motor so that the
orientation of the
MSS is the same as
the motor.

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Survey Instruments

The mule shoe

stinger is oriented
in reference to the
high side on the
survey tool. When
the stinger enters
the MSS, it is
rotated until it
lines up with the
orientation of the
MSS and motor.
© 2010 PetroSkills, LLC. All rights reserved. 108
Survey Instruments

In order to make a connection, the

steering tool had to be pulled from
the hole
It was time consuming and there was
a possibility of getting stuck while
tripping the wireline
A side entry sub was developed to
minimize connection time

© 2010 PetroSkills, LLC. All rights reserved. 109

Survey Instruments

With the side

entry sub, the
wireline passes
from inside the
drill string to
outside the drill
string

© 2010 PetroSkills, LLC. All rights reserved. 110

Survey Instruments

With the wireline

outside the pipe
near the surface,
the steering tool
did not have to
be pulled to
make a
connection

© 2010 PetroSkills, LLC. All rights reserved. 111

Survey Instruments

Drilling with a
side entry sub
The kelly
bushings are
on a stand to
keep from
damaging the
wireline

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Survey Instruments

Development of the MWD spelled

doom for the steering tool because
the drill string could not be rotated
with the wireline in the hole
A wet connect system was
developed to allow rotation of the
drill string without pulling the
steering tool

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Survey Instruments

The wireline
enters the top of
the swivel
While rotating,
the wet connect
is not connected
to the tool
It is reconnected
while surveying
or sliding

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Survey Instruments

Steering tools are still used where the

MWD may not be applicable
ØUnderbalanced drilling
ØLCM in the mud
ØHigh temperature

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Survey Instruments

MWD pulses the mud system to send

information to the surface
ØPositive pulse
ØNegative pulse
ØContinuous wave
ØAlso have electromagnetic MWD which
uses radio waves to send information

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Survey Instruments
Surface Computer

Transducer
On Standpipe

Pressure Pulses
in Drill Pipe

MWD

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Survey Instruments

Directional MWD
tool

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Survey Instruments

Positive pulse –
a restriction in
the MWD causes
an increase in
pressure
1’s and 0’s
Pressure Time

Positive Pulse

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 Survey Instruments

Negative pulse
uses a valve in
the side of the
MWD to bypass
some of the fluid
reducing the
Pressure

standpipe
Time
pressure
Negative Pulse

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Survey Instruments

Continuous
wave modulates
the frequency to
generate 1’s and
0’s

Pressure
Time

Continuous Wave

© 2010 PetroSkills, LLC. All rights reserved. 121

Survey Instruments
Antenna Array

Electromagnetic
MWD uses radio
waves
Works in
compressible
fluids
(underbalanced)

MWD

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Survey Instruments

The EMS or electronic multishot stores

the information in a computer chip
(memory). Once the tool is retrieved
from the hole, the survey data is
downloaded into a computer.

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Survey Instruments

Gyroscopic tools
ØConventional Gyro
ØRate or North Seeking Gyro
ØRing Laser Gyro
ØInertial Grade Gyro

SURVEY INSTRUMENTS

MAGNETIC GYROSCOPIC

COMPASS ELECTRONIC CONVENTIONAL RATE OR RING LASER INERTIAL GRADE

NORTH SEEKING

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Survey Instruments

Conventional
gyro
Get direction
only and not
inclination
Inclination is
still with
accelerometers

© 2010 PetroSkills, LLC. All rights reserved. 125

Survey Instruments

A conventional gyro must be

referenced. You have to know which
way the axis is pointing.
The conventional gyro has drift due to
imperfections in the gyro and the
earth’s rotation

© 2010 PetroSkills, LLC. All rights reserved. 126

Survey Instruments

Rate or North Seeking Gyro

SURVEY INSTRUMENTS

MAGNETIC GYROSCOPIC

COMPASS ELECTRONIC CONVENTIONAL RATE OR RING LASER INERTIAL GRADE

NORTH SEEKING

© 2010 PetroSkills, LLC. All rights reserved. 127

Survey Instruments

Determines which way is north

without referencing
Automatically adjusts for drift
electronically
More accurate than the conventional
gyro

© 2010 PetroSkills, LLC. All rights reserved. 128

Survey Instruments

Ring laser gyro uses lasers to get

direction. More accurate than rate
gyro. 5 1/4” OD

SURVEY INSTRUMENTS

MAGNETIC GYROSCOPIC

COMPASS ELECTRONIC CONVENTIONAL RATE OR RING LASER INERTIAL GRADE

NORTH SEEKING

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Survey Instruments

Inertial grade gyro is the same gyro

used for navigation, 10 5/8” OD

SURVEY INSTRUMENTS

MAGNETIC GYROSCOPIC

COMPASS ELECTRONIC CONVENTIONAL RATE OR RING LASER INERTIAL GRADE

NORTH SEEKING

© 2010 PetroSkills, LLC. All rights reserved. 130

Survey Instruments

Cannot be run in 9 5/8” or smaller

casing
Now have smaller versions of the
inertial gyro
The most accurate survey instrument
available

© 2010 PetroSkills, LLC. All rights reserved. 131

Survey Instruments

Bottomhole assemblies are oriented

with survey tools
The orientation of the BHA is called
the toolface
Toolface is magnetic below 5
degrees and high side above 5
degrees

© 2010 PetroSkills, LLC. All rights reserved. 132

 ®

DELIVERING KNOWLEDGE. DEVELOPING COMPETENCE.

LWD

Logging while drilling

LWD

LWD tools are

added to the MWD
tool and the MWD
pulser sends the
information to the
surface
Some of the LWD
data may be stored
in memory and
downloaded later

© 2010 PetroSkills, LLC. All rights reserved. 134

LWD

Typical position
of LWD tools in
the bottomhole
assembly

© 2010 PetroSkills, LLC. All rights reserved. 135

 ®

DELIVERING KNOWLEDGE. DEVELOPING COMPETENCE.

METHODS OF DEFLECTING A
WELLBORE
Any number of directional tools can be
used to deflect a wellbore or make the
wellbore go where we want it to go
Methods of Deflection

Whipstocks
Jetting
Rotary BHA
ØRotary BHA with adjustable stabilizer
Motor
ØSteerable motor
Rotary steerable assembly

© 2010 PetroSkills, LLC. All rights reserved. 137

Methods of Deflection

Over time, the tools we have used to

deviate a wellbore in the desired
direction have changed
Newer and more efficient tools have
been developed and will be
developed in the future

© 2010 PetroSkills, LLC. All rights reserved. 138

Methods of Deflection

Whipstock
ØOne of the
earliest tools used
in the industry
was the
whipstock
ØThe whipstock is
a metal wedge
placed in the
wellbore that
causes the bit to
deviate

© 2010 PetroSkills, LLC. All rights reserved. 139

Methods of Deflection

ØIn the early years of the petroleum

industry, they were used to sidetrack wells
if a portion of the drill string became stuck
ØAs directional drilling started in the 1930’s,
whipstocks were oriented and used to
change the inclination and azimuth of the
wellbore
ØWhipstocks were not very efficient

© 2010 PetroSkills, LLC. All rights reserved. 140

Methods of Deflection

ØIn order to use a

whipstock, the
drill string was
pulled from the
hole and a
whipstock was
run into the well
ØOn a retrievable
whipstock, a pin
was sheared and
the bit drilled off
the whipstock
© 2010 PetroSkills, LLC. All rights reserved. 141
Methods of Deflection

ØBecause the bit

had to be run in
with the
whipstock, it was
a smaller
diameter than the
hole
ØA second trip was
made to open the
hole to full gage

© 2010 PetroSkills, LLC. All rights reserved. 142

Methods of Deflection

ØIn harder rock, a reaming trip may have

been required
ØUsing the whipstock required a minimum of
three trips, which was not cost effective
ØPermanent whipstocks were no better even
though a full sized bit could be used to drill
off it

© 2010 PetroSkills, LLC. All rights reserved. 143

Methods of Deflection
Starting Mill

ØThe primary use Shear bolt

of a whipstock
today is in
sidetracking out
of casing

Slips

Bottom Trip

Bridge Plug

© 2010 PetroSkills, LLC. All rights reserved. 144

Methods of Deflection

Starter Mill

Two trips are Watermelon Mill

required to
sidetrack the
wellbore
Window Mill

© 2010 PetroSkills, LLC. All rights reserved. 145

Whipstock

ØSingle trip
whipstock can
drill off the
whipstock
without making a
trip

© 2010 PetroSkills, LLC. All rights reserved. 146

Whipstocks

ØThis retrievable
whipstock has a
keyway pocket in
the whipstock for
later removal

© 2010 PetroSkills, LLC. All rights reserved. 147

Methods of Deflection

Jetting was used as an alternative to

whipstocks
ØJetting was only effective in softer rocks
since formations have to be eroded to
change the trajectory of the wellbore

© 2010 PetroSkills, LLC. All rights reserved. 148

Methods of Deflection

ØA bit with a larger

diameter nozzle
facing the side of
the hole was used
to erode the
formation to one
side of the bit
ØThe larger nozzle
was oriented in
the desired
direction
© 2010 PetroSkills, LLC. All rights reserved. 149
Methods of Deflection

ØThe formation
was washed as
the assembly was
lowered into the
hole
ØIf the rocks were
too soft, the entire
bottom of the hole
may wash out
without
substantially
altering the hole
trajectory
© 2010 PetroSkills, LLC. All rights reserved. 150
Methods of Deflection

ØIn harder formations, the bit often had to be

turned slightly left and right to erode the
side of the hole
ØPenetration rate while jetting, was very
slow
ØOnce a portion of the hole had been jetted
and the bit worked to bottom, the assembly
was rotated to continue drilling ahead

© 2010 PetroSkills, LLC. All rights reserved. 151

Methods of Deflection

ØThe jet deflection bit was actually the first

steerable assembly
§ While jetting, the drill string was not rotated
in order to effect a trajectory change
§ After jetting, the drill string was rotated to
drill ahead

© 2010 PetroSkills, LLC. All rights reserved. 152

Methods of Deflection

Rotary BHA
ØThe rotary BHA consists of a bit, drill
collars, stabilizers, reamers, subs and
other special tools run below the drill pipe

© 2010 PetroSkills, LLC. All rights reserved. 153

Methods of Deflection

ØA slick assembly is
simply a bit and drill
collars
ØThe deviation
tendency is caused
by the bending of
the drill collars
ØThe point at which
the collars touch the
wall of the hole is
the tangency point
© 2010 PetroSkills, LLC. All rights reserved. 154
Methods of Deflection

ØThe resultant force

applied to the
formation is not in
the direction of the
hole axis but in the
direction of the drill
collar axis

© 2010 PetroSkills, LLC. All rights reserved. 155

 Methods of Deflection

ØThe resultant force

can be broken up into
its components FB and
FP
ØFB is the side force
caused by the
bending of the collars
or building force
ØFP is the force due to
gravity or pendulum
force
© 2010 PetroSkills, LLC. All rights reserved. 156
Methods of Deflection

ØIdeally, if
FP > FB, the hole inclination will drop
FP < FB, the hole inclination will increase
FP = FB, the hole inclination will remain
constant
ØThe building force can be increased by
increasing bit weight, which drives the
tangency point down

© 2010 PetroSkills, LLC. All rights reserved. 157

Methods of Deflection

ØThe building force is also affected by the

stiffness of the collars
ØStiffer collars will bend less
ØAs the diameter of the collar increases, the
stiffness of the collar increases
ØThe pendulum force can be increased by
reducing bit weight and using larger
diameter collars

© 2010 PetroSkills, LLC. All rights reserved. 158

Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 159

Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 160

Methods of Deflection

ØDeviation
problems are
associated with
formation dip
ØThe anisotropy of
the formation
causes deviation

© 2010 PetroSkills, LLC. All rights reserved. 161

Methods of Deflection

ØIf the formation deviation tendency can be

defined as a force FF, the resultant force at
the bit would be
FB + FP + FF
ØThe wellbore will continue to build angle
until the sum of the forces is equal to zero
ØUnfortunately it is difficult to define FF and
it changes with depth

© 2010 PetroSkills, LLC. All rights reserved. 162

Methods of Deflection

ØRule of thumb
ØIf the bed dip is less
than 45 degrees, the
bit will have a
tendency to deviate
perpendicular to the
bed dip (up dip)

© 2010 PetroSkills, LLC. All rights reserved. 163

Methods of Deflection

ØIf bed dip is above

65 degrees, the bit
will have a tendency
to deviate along the
bed dip
ØBetween 45 and 65
degrees, the bit can
do either

© 2010 PetroSkills, LLC. All rights reserved. 164

Methods of Deflection

ØIn directional drilling, it is the difference

between the bit angle and the formation dip
that causes the deviation
ØIn this case, the bit wants to deviate up dip

Deviation
© 2010 PetroSkills, LLC. All rights reserved. 165
Methods of Deflection

ØThe formation may

want the bit to drop
inclination when the
wellbore is at an
inclination greater
than bed dip
ØA building assembly
may need to be run
in order to maintain
inclination
Deviation
© 2010 PetroSkills, LLC. All rights reserved. 166
Rotary BHA

Stabilizers are
used as
fulcrums in
order to
increase the
side force at the
bit

© 2010 PetroSkills, LLC. All rights reserved. 167

Rotary BHA

Stabilizers are
used as
fulcrums in
order to
increase the
side force at the
bit

© 2010 PetroSkills, LLC. All rights reserved. 168

Methods of Deflection

Building assembly
ØA building assembly is constructed by
placing a stabilizer near the bit
ØBending of the drill collars above the
stabilizer causes the building force at the
bit to increase substantially

© 2010 PetroSkills, LLC. All rights reserved. 169

Methods of Deflection
90’
High

High
30’ 60’
High
60’
High to
Medium

30’ 45’
Medium
to Low

Building Assemblies

© 2010 PetroSkills, LLC. All rights reserved. 170

Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 171

Methods of Deflection

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Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 173

Methods of Deflection

In order to make a dropping

assembly, the pendulum force is
maximized by placing a stabilizer at
least 30 to 90 feet (9 to 27 meters)
above the bit

© 2010 PetroSkills, LLC. All rights reserved. 174

Methods of Deflection
60’
High

30’ 60’
High

45’
Medium

30’
Low

Dropping Assemblies

© 2010 PetroSkills, LLC. All rights reserved. 175

Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 176

Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 177

Methods of Deflection

A holding assembly is constructed

by placing stabilizers closer together
so that the collars are more rigid
Bit side force is minimized

© 2010 PetroSkills, LLC. All rights reserved. 178

Methods of Deflection
30’, 60’ or 90’ 30’ 15’-20’
Medium
A

30’ 30’ 5’-15’

Medium
B

30’ or 60’ 30’ or 60’ 30’-40’

Low
C

Holding Assemblies

© 2010 PetroSkills, LLC. All rights reserved. 179

Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 180

Methods of Deflection

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Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 182

Methods of Deflection
Can also make a rotary assembly
with an adjustable stabilizer

© 2010 PetroSkills, LLC. All rights reserved. 183

Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 184

Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 185

Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 186

Methods of Deflection

Positive displacement motors were

introduced in the 1960’s

© 2010 PetroSkills, LLC. All rights reserved. 187

Methods of Deflection
Rotor/stator configuration

© 2010 PetroSkills, LLC. All rights reserved. 188

Methods of Deflection
Speed (RPM) /
Torque (Ft-Lbs.)
Ø For best performance,
the power section
should be matched to
the bit and formation
being drilled. The
speed and torque of a
power section is
directly linked to the
number of lobes on the
rotor and stator. The
higher the number of
lobes, the higher the
torque and the lower the
RPM.
© 2010 PetroSkills, LLC. All rights reserved. 189
Methods of Deflection

© 2010 PetroSkills, LLC. All rights reserved. 190

Methods of Deflection

Power pack section

ØRotor is hard
ØStator is flexible
ØStator housing is thin
ØPDM is not a drill
collar

© 2010 PetroSkills, LLC. All rights reserved. 191

Methods of Deflection

ØReverse application of the Moineau

pump principle
ØElastomer lined - steel tube stator
ØChrome coated steel rotor
ØConverts Hydraulic HP (flow & pressure) to
Mechanical HP (rpm & torque)
ØThere are three main producers of motor
power sections in the world

© 2010 PetroSkills, LLC. All rights reserved. 192

Methods of Deflection

Ø This differential pressure causes drilling fluid to

enter the cavities at the top of the motor. As it
moves through the motor, the fluid pushes on the
rotor causing it to rotate.

© 2010 PetroSkills, LLC. All rights reserved. 193

 Methods of Deflection

The sum of the cross-sectional

areas of any plane is a constant. As
a result, the speed of the motor is
constant for a given flow rate.

© 2010 PetroSkills, LLC. All rights reserved. 194

Methods of Deflection

Typical PDM power curve

Motor Start Pressure, 110 psi (7 bar)
rpm ft-lb N• m
200 600 gal/min (2271 L/min) 10,000 13,557

180 9000 12,202

160 8000 10,846

450 gal/min (1704 L/min)
140 7000 9490

120 6000 8134

Torque
rpm

100 300 gal/min (1136 L/min) 5000 6779

80 4000 5423

60 3000 4067

40 2000 3490

20 1000 1356

psi 0 100 200 300 400 500 600 700

bar 0 7 14 21 28 34 41 48
Pressure

© 2010 PetroSkills, LLC. All rights reserved. 195

Methods of Deflection

Ø Rotor is coupled to
transmission
Ø Transmission shaft is
coupled to the bearing
pack
Ø The adjustable bent
housing enables the bend
to be changed at the
wellsite
Ø The housing can be
adjusted 0.26 to 3.0
degrees depending upon
motor size and
manufacturer
© 2010 PetroSkills, LLC. All rights reserved. 196
Methods of Deflection
Ø Works on offset pin and box
concept
Ø Typically adjust from 1 to 3 degrees
Ø Four main Components: Offset
Housing, Splined Mandrel, Stator
Adapter Housing, and Adjusting
Ring

© 2010 PetroSkills, LLC. All rights reserved. 197

Methods of Deflection

Bearing function
ØOn bottom thrust bearings carry
force from the bit (WOB)
ØOff bottom thrust bearings carry
the hydraulic load of the mud
and weight of the rotor
ØRadial bearings carry side
loads
ØFlow restrictor diverts a portion
of the mud for lubrication

© 2010 PetroSkills, LLC. All rights reserved. 198

Methods of Deflection

Typical steerable motor

configuration

© 2010 PetroSkills, LLC. All rights reserved. 199

 Methods of Deflection

Effect of bend housing angle on

build rate and bit side load
20,000 Bit Side-Load
Straight Hole
18,000 Bit Side-Load 4 to
Rotating in 35 ft
16,000
Curved Hole
12 ft
Bit Side-Load, lb

14,000
12,000 Bend Dogleg
Angle Severity
10,000 (°) of Curved
Hole (°/100 ft)
8000
0.5 2.6
6000
0.75 4.34
4000
1 6.08
2000 1.25 7.85
0 1.5 9.57
0.5 0.75 1 1.25 1.5
Bent Housing Angle, deg

© 2010 PetroSkills, LLC. All rights reserved. 200

Methods of Deflection

Rotary Steerable System (RSS)

ØSteerable without sliding (100% rotation)
ØCan change both inclination and direction

© 2010 PetroSkills, LLC. All rights reserved. 201

Methods of Deflection

Steerable motor
in the slide and
rotate mode

© 2010 PetroSkills, LLC. All rights reserved. 202

Methods of Deflection

Limitations of steerable motors in the

slide mode
ØSometimes difficult to slide
ØDifficulty maintaining orientation
ØPoor hole cleaning
ØLower effective penetration rate
ØHigher wellbore tortuosity
ØDifferential pressure sticking
ØBuild rate is formation sensitive

© 2010 PetroSkills, LLC. All rights reserved. 203

Methods of Deflection

Limitations of steerable motors in the

rotate mode
ØHigher vibrations lead to motor and MWD
failure
ØAccelerated bit wear
ØPoor hole quality for logs sometimes
The rotary steerable system address
some but not all of the limitations

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These rotary
steerable concepts
were patented in
the 1950’s, but the
design is being
used today
Guidance systems
were required to
make them work

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Methods of Deflection

Rotary
steerable
systems being
designed and
used today

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Methods of Deflection

Schlumberger Power Drive rotary

steerable assembly

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Methods of Deflection

Schlumberger rotary steerable

system has pistons near the bit that
push against the side of the hole

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Gyrodata rotary steerable assembly

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Baker AutoTrak works like the

Schlumberger tool with pistons near
the bit

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Economics of rotary steerable

45 Assumptions:
40
Motor and MWD = $12,000
Time Reduction, %

35
Rotary Steerable = $35,000
30
MTBF is the same
25
20
15
10
5
0
20,000 40,000 60,000 80,000 100,000 120,000 140,000
Daily Operating Cost (excluding directional drilling)

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Rotary steerable can improve hole

cleaning

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Methods of Deflection

Rotary steerable assemblies have the

potential to reduce overall dogleg
severity

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Rotary steerables can still drill

directionally when the pipe will not
fall into the hole with its own weight
(steerable motor cannot slide)

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Methods of Deflection

Service companies eventually want

to get the rotary steerable to drill the
hole without interference from the
surface
ØThe directional program is placed in the
MWD
ØThe computer computes a position and
determines what it needs to do to get to the
target and takes the appropriate action

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Methods of Deflection

ØAll the drilling contractor does is add drill

pipe similar to drilling a vertical well
ØBaker now markets a tool that will do that
It would not be applicable where the
directional target significantly
changes based on geosteering data

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