Petroleum Engineering 406
Lesson 21
Wellbore Trajectory Control
Lesson 18 - Wellbore Trajectory Control
Bent Motor and Bent Sub
Examples
Directional Drilling Measurements
Single Shot and Multishot
Magnetic and Gyro
Steering Tools
MWD tools
Homework
READ:
“Applied Drilling Engineering”,
Ch. 8 (to page 390)
Nonmagnetic
Drill Collar
Orienting Sub
Hole
Bent Sub
Mud Motor
Bent Sub
Angle
Bit
Fig. 8.39: Bent sub unconstrained
and constrained in a wellbore.
b is not necessarily equal to the bent sub angle, but it may be close in (a) above
Problem 1
Determine the effective bent sub
response for a 1 1/2o bent sub in a
motor run where at 6,357’, a = 1o and
e is S85E and at 6,382, aN = 1o and eN
is S20E; the tool face is 160o right of
high side.

  160


aN 1

a 1
e  65


e N  160
e  95
L  25 ft
Solution to Problem 1
Calculate b from Eq. 8.53:
b  cos1cos e sin aN sin a  cos aN cos a

 cos1 cos 65 sin1 sin1  cos1 cos1

 cos 1 0.999824  1.07
Dogleg severity:
i
100
o
  b  1.07 
 4.28
100ft
L
25
Solution to Problem 1 - cont’d
If the mud motor length is 25 ft from the
bit face to the bent sub, the maximum
angle change that could be reached if
there are no restrictions is:
100
o
  1.5 
 6.0
25
100ft
The lower rate of build implies that the
formation resisted the maximum rate of

4
.
3
build by a factor of:
 0.72
6.0

An efficiency factor?
b = Bent Sub Angle?
Since the value of b for any given run
may differ from the bent sub angle, it
should not surprise us if
e predicted = e measured
Let us look at some examples.
Fig. 8.40: Example of three jetting stops while trying to
kick off and set the wellbore lead.

e th  77

eac  62
e th  14

eac  16

e th  33

eac  30

Jetted 7’ 1745-52’
Surv 1722’:
S32W 2.25
o
Nozzle Orientation
 = -122
o
Orient S90E
Final 1799’:
S30E 2.75
e th  77

o
eac  62

 = -80
o
Jetted 12’ 1850-62’
Surv 1814’ S20E 3.0
o
Orient N80E
Final 1877’ S36E 3.25
e th  14

o
eac  16

 = -74
o
Jetted 6’ 1925-31’
Surv 1877’ S36E 3.25
o
Orient N70E
Final 1940’ S66E 4.75
e th  33

o
eac  30

Directional Drilling
Measurements
The trajectory of a wellbore is determined
by the measurement of:
inclination
q, a, I
direction
f, e, A
measured depth
MD, L, L
Directional Drilling
Measurements - cont’d
A tool-face measurement is required to
orient:
a whipstock
the large nozzle on a jetting bit
a bent sub or bent housing
Directional Drilling
Measurements - cont’d
Tools available
single-shot magnetic or gyroscopic
multi-shot magnetic or gyroscopic
magnetometers, accelerometers,
MWD tools
Magnetic Single-Shot Instrument
Records
– inclination
– direction
– tool face position
on sensitized paper or photographic film
Inclination may be determined by
– a float on a liquid
– a pendulum
Magnetic Single-Shot Instrument
Unit may be triggered by:
– clock timer.
– inertial timer (after stop).
Unit may be dropped (pumped down)
and later retrieved by wireline or the
drillpipe.
Magnetic Single-Shot Instrument
Single-shot instruments are used:
– to monitor progress of directionalcontrol well.
– to monitor progress of deviation-control
well.
– to help orient tool face for trajectory
change.
Magnetic Single-Shot
Instrument - cont’d
Procedure:
– load film into instrument
– activate timer (activate stopwatch)
– make up the tool
– drop the tool
– retrieve tool (wireline or drillpipe)
Light
Housing
Center Post
Float
Fluid
Reference Mark
Main Frame
Photographic
Disc
A. 0-20o
Angle-Compass Unit
B. 0-70o
Angle-Compass Unit
Fig. 8.41: Schematic diagrams of magnetic single-shot
angle-compass unit (courtesy Kuster Co.).
1. Pendulum
Fig. 8.43:
Pendulum
suspended
inclinometer
and
compass
unit for a 0 to
oo
17 singeshot unit.
2. Circular Glass
3. Compass
4. Pressure equalization
5. Cover glass
o
Indicated inclination 5 .
Direction of inclination
N 45 degrees 0’ or
azimuth 45 degrees.
A/C Units
Plumb-Bob Units
Incl. Only Units
Fig. 8.42:
Single-shot
film disks
(courtesy of
Kuster Co.).
• Inclination
• Direction
• Tool Face Angle
Fig. 8.12:
Pendulum
assembly: a) plumbbob angle unit b) drift
arc inclinometer
Pendulum
Glass ring
Piston
(a)
(b)
Fig. 8.13:
Schematic
drawing of
magnetic
single and
multi-shot
instruments.
o
N35 W
o
I = 5.5
Hole direction with
reference to Magnetic North
Compass
Inclination Scale
Fig. 8.44:
Cardan suspended
compass and
inclinometer for a
single-shot
o
o
5 to 90 unit.
Wire Line Socket
Overshot
Protective Case
Orienting
Anchor & Plug
Mule Shoe
Mandrel
Rope Socket
Swivel
Stabilizer
Stabilizer Fingers
Fig. 8.45:
Typical
magnetic
single-shot
tool with
landing sub.
Bottom Hole
Orienting Sub
Bottom Landing Assembly
Takes time. Rig time is costly. Temperature limitation. May have to pump down.
Ready to
be Dropped
Free Falling
to Bottom
Tool
seated
Retrieve
single shot
Fig. 8.46: Typical single-shot operation.
Timer On
3 min.
Compass Unit
*Single Shot
Instruments are
run on slickline if
there is a mule
shoe sub in the
hole
Single Shot
Ready to be
Dropped
Non
Magnetic
Drill Collar
Orienting Sub
Sleeve
Single Shot
Free Falling in
Mud to Bottom
Fig. 8.46:
Typical
single-shot
operation.
Fig. 8.46:
Typical
single-shot
operation.
Tool seated
in orienting
sleeve or at
stop taking
picture
3
min.
10 min.
Overshot
Used to
Fish
Single
Shot
Wireline
unit to
retrieve
single
shot
Top View
Direction of
Tool Face Via
Bent Sub
Fishing Neck
Non Magnetic Collar
Single Shot
Mule Shoe Orienting Sub
Orienting Sleeve Lined up with Bent Sub
Bent Sub
Mule Shoe
Key Position
New Centerline
Mud
Motor
Existing
Centerline
Fig. 8.47:
Arrangement of the
mule shoe for
orienting a mud motor.
Magnetic Multishot Instruments
Are capable of taking numerous survey
records in one run.
May be dropped down the drillpipe or run
on wireline in open hole.
The unit contains a watch that is spring
wound and uses the power of the spring
to operate a timer cam.
Non-Magnetic Drill Collar(s)
Compass Position
Multi-shot Instrument
Landing Plate
Fig. 8.48:
Typical
arrangement
for landing a
multi-shot
instrument.
Bottom Landing
Rope Socket
Stabilizer with Rubber Pins
Battery Case
Battery
Connector
Connector
Shock
Absorber
Watch
Assembly
Protective Instrument Barrel
Angle Unit
Barrel Lower Ball Plug
Aluminum Spacer Bar
Bottom Shock Absorber
Assembly
Fig. 8.49:
Drop
multi-shot
survey
instrument
Watch Section
Motor
Light
Switch
Lever
Geneva
Gear
Knife
Geneva Drive
Winding
Motor Wheel Assembly
Switch
Stem
Lever
Watch Switch Terminal
Film Sprocket
Switch
Time Cycle Cam
Takeup Film Supply
Film Spool
Spool
Fig. 8.50: Views of the watch and camera
unit of a typical multi-shot tool.
Magnetic Multishot - cont’d
The multishot tool is usually dropped down
the drillpipe and landed in the nonmagnetic
drill collar.
During the trip out, a survey is taken every
90 ft, i.e. every stand.
Magnetic Multishot - cont’d
More closely spaced stations could be
obtained by stopping the pipe more often,
and waiting for a picture.
A stopwatch at the surface is synchronized
with the instrument watch.
Fig. 8.51:
Use of the
surface
watch while
running a
magnetic
multi-shot
operation.
Synchronize with instrument watch by
starting at the instant camera lights go on.
Time Intervals:
A. 10 seconds Lights are on, exposing film
B. 15 seconds - Delay before moving.
This is an allowance for instrument
watch lag during survey.
Time Intervals - cont’d
C. 20 seconds - Instrument is
idle allowing movement of drill string
without affecting picture. Most moves
require sufficient time for taking one or
more shots while moving
D. 15 seconds - Minimum time for plumb
bob and compass to settle for good
picture, plus allowance for instrument
gain during survey.
Fig. 8.52b:
Projection of
one survey
frame for
determining
inclination and
direction.
Steering Tools
Used with mud
motors and bent sub
Can either pull every
stand or use a side
entry sub for
continuous drilling
Standard
Measuring
Cable
Monel DC
Probe
Mule Shoe
Bent Sub
Mud Motor
MWD Tools
MWD Tools
Gyroscopic Tools
Non-magnetic drill
collars used to prevent
magnetic interference
from drillstring
Gyros used if magnetic
interference is from
non drillstring source