Post on 27-Oct-2020
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Primary funding is provided by
The SPE Foundation through member donations
and a contribution from Offshore Europe
The Society is grateful to those companies that allow their
professionals to serve as lecturers
Additional support provided by AIME
Society of Petroleum Engineers
Distinguished Lecturer Programwww.spe.org/dl
1
WELLBORE POSITION, QUALITY CONTROL,
GROSS ERRORS AND ERROR MODELS
SPE 2014-2015 Distinguished Lecturer Series
Nestor Eduardo Ruiz
Gyrodata
2
OUTLINE
●Wellbore position
● Inclination measurements
●Azimuth measurements
●Error models for Magnetic tools
●Error models for Gyro tools
●Error models and gross errors
●Conclusions and Recommendations
3
WELLBORE POSITION
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INCLINATION
5
AZIMUTH
OLD MAGNETIC TOOLS
6
MULTISHOT MECHANISM
7
Dip Angle= f(Hx, Hy, Hz, Gx, Gy, Gz)
SOLID STATE MAGNETIC TOOLS
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INCLINATION
9
INCLINATION
10
AZIMUTH
• MAGNETIC TOOLS
– Very stable sensors
– Variable reference
• Rate Gyro tools
– Very stable reference
– Variable sensors
– Self oriented with the
Earth Rate.
• Rate gyro tools
– Dependent of one
initialization point
MAGNETIC REFERENCE
EARTH RATE REFERENCE
CONTINUOUS MODE
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QUALITY CONTROL FOR MAGNETIC TOOLS
• INTERNAL TEST in each shot
– Total Magnetic Field (H Total)
– Total Gravity (G Total)
– Dip angle
– Additional tests
– Repeated measurements with additional
down-hole sensors
– Rotation Shot Misalignment TestTool misalignment componentsFor BHA-fixed tool
(SPE PAPER 105558)
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FREE GYRO
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RATE GYRO
GYRO COMPASS MODE
Accelerometers provide
Inclination and Tool Face
Gyro provides the
direction to true Northz
Torque axis y
Spin AxisTorque axis x
Instrument Axis
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RATE GYRO
CONTINOUS MODE
Vertical Earth
Rotation Vector
Horizontal Earth
Rotation Vector
Gyro Sensor
Wellbore Direction
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QUALITY CONTROL FOR RATE GYRO TOOLS
● For Gyro Compass mode
● Horizontal Earth Rate Test for xy
Gyro system
● Total Gravity (G total)
●For Continuous mode
● Quality Number
● In run / Outrun comparison
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ERROR MODEL FOR MAGNETIC TOOLS
• Wolff and De Wardt model in 1981
• Basic MWD ISCWSA model in 2000 (Williamson SPE
67616)
• Assumptions
• Errors in the calculated well position are
caused exclusively by the presence of
measurement errors at the wellbore survey
stations
• Three element measurement vectors
• Depth
• Inclination,
• Azimuth.
• Tool Face angle is required for the
propagation of the error 17
• Error sources Statistically independent
• Linear relationship between the size of each
measurement error and the position (or
coordinate) error
• The combined effect on final position of any
number of measurements at any number of
survey stations is equal to the vector sum of
the contribution of the individual error effects.
ERROR MODEL FOR MAGNETIC TOOLS
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• Error propagation mode can be
• Random
• Systematic
• Well by Well or
• Global.
• MWD surveys run
• following standard procedures
• rigorous and regular tool calibration
• survey interval no greater than 100ft
• non-magnetic spacing according to standard
charts
• not surveying in close proximity to existing
casing strings or other steel bodies
ERROR MODEL FOR MAGNETIC TOOLS
ASSUMPTIONS
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ERROR MODEL FOR GYRO TOOLS
• Set of terms for the ISCWSA compatible model for
Gyro compass mode
• Set of simplified terms for the continuous mode of
operation
• All terms for the ISCWSA need to be provided for
each gyro Company
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SPE 90408
GROSS ERROR EXAMPLE
-25
-20
-15
-10
-5
0
-5 0 5 10 15 20
NO
RTH
ING
(m
)
EASTING (m)
-25
-20
-15
-10
-5
0
5
10
15
-10 0 10 20
NO
RTH
ING
(m
)
EASTING (m)
Well 1 Initial Well Head
New Well First Survey
-25
-20
-15
-10
-5
0
5
10
15
-10 0 10 20
NO
RTH
ING
(m
)
EASTING (m)
Well 1 Initial Well Head
New Well First Survey
-30
-20
-10
0
10
20
30
40
-20 0 20
NO
RTH
ING
(m
)
EASTING (m)
Well 1 Initial Well Head New Well First Survey
New Well Second Survey
-30
-20
-10
0
10
20
30
40
-20 0 20
NO
RTH
ING
(m
)
EASTING (m)
Well 1 Initial Well Head New Well
Well 1 Actual Well Head
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BOTTOM HOLELOCATEDMD: 3153.00
BOTTOM HOLELOCATEDMD: 3178.20
-100
0
100
200
300
400
500
600
700
-300 -200 -100 0 100 200 300 400 500
NO
RTH
IN
G (
m)
EASTING (m)
Survey 1 Survey 2
BOTTOM HOLE
LOCATEDMD: 3153.00
BOTTOM HOLELOCATED
MD: 3310.02
0
10
20
30
40
50
60
70
80
90
100
0 500 1000 1500 2000 2500 3000 3500
IN
CLIN
ATIO
N
MEASURED DEPTH (m)
Survey 1 Survey 2 Gyro
GROSS ERROR EXAMPLE
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BOTTOM HOLELOCATEDMD: 2606.00
-2
0
2
4
6
8
10
12
14
16
-4 -2 0 2 4 6 8 10 12 14
NO
RTH
ING
(m
)
EASTING (m)
BOTTOM HOLE
LOCATEDMD: 2606.72
12.3
12.4
12.5
12.6
12.7
12.8
12.9
13.0
13.1
13.2
13.3
13.4
8.0 8.2 8.4 8.6 8.8 9.0
NO
RTH
ING
(m
)
EASTING (m)
COMPLETION APLICATION EXAMPLE
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GROSS ERROR EXAMPLE
BOTTOM HOLE
LOCATED
MD: 4066.86
BOTTOM HOLE
LOCATED
MD: 4080.00
BOTTOM HOLELOCATED
MD: 4080.00
BOTTOM HOLE
LOCATEDMD: 4066.86
0
20
40
60
80
100
120
0
10
20
30
40
50
60
70
80
0 500 1000 1500 2000 2500 3000 3500 4000 4500
AZIM
UTH
IN
CLIN
ATIO
N
MEASURED DEPTH (m)
Azimuth Survey 1 Azimuth Survey 2 Inclination Survey 2 Inclination Survey 1
BOTTOM HOLELOCATEDMD: 4066.86
BOTTOM HOLELOCATEDMD: 4080.00
-1500
-1000
-500
0
500
1000
1500
2000
2500
3000
-500 0 500 1000 1500 2000 2500 3000 3500 4000
NO
RTH
ING
(m
)
EASTING (m)
Survey 1 Survey 2
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GROSS ERROR EXAMPLE
0
20
40
60
80
100
120
140
160
0 500 1000 1500 2000 2500 3000 3500 4000 4500
AZIM
UTH
MEASURED DEPTH (m)
0
20
40
60
80
100
120
140
160
0 500 1000 1500 2000 2500 3000 3500 4000 4500
AZIM
UTH
MEASURED DEPTH (m)
Gyro Database MWD
0
50
100
150
200
250
0 500 1000 1500 2000 2500 3000 3500 4000 4500
AZIM
UTH
MEASURED DEPTH (m)
Gyro Database corrected MWD Database MWD
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ERROR MODELS
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•A shorter gyro run $10,000 +
•A proximity ‘shut in’ $100,000 +
•A plug back side-track $1 million +
•A dry well or ‘Dead Zone’ $10 million +
•A deep landing $100 million +
•A minor collision blowout $1 billion +
•A major collision blowout $10 billion +
BUSINESS CASE?
Prof Angus Jamieson
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CONCLUSIONS
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• Survey planning is very important in the
design of the well trajectory.
• Verify the wellhead position and the survey
program to avoid gross errors.
• The survey data needs to be validated
and screened for gross error before to
use in the error model.
• Internal Quality Control measures after
each shot are necessary but not enough.
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• External Quality Control with an overlapping
independent survey is the most reliable way
to detect gross errors.
• Comparisons of Inclination, Azimuth and
coordinates to an independent verification
survey, is the most powerful Quality Control
available.
• Each error model is validated by the service
companies.
CONCLUSIONS
• After each survey station
• G-total-, H-total/dip- tests
• Misalignments, Declination, Sag and Depth are not controlled
• At least once per survey section
• Rotation shot tests
• Misalignments are now controlled
• At the end of each survey section
• Multi station corrections
• Validity dependent on geometrical variation
• No more terms controlled
• Accuracy is improved
SURVEY RECOMMENDATION PRACTICES
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• At an intermediate bit run
• Independent verification survey tests
• EMS - Declination is not controlled
• Drop gyro - Depth is not controlled
• Wire-line gyro - All error terms are controlled
• At TD if a definitive survey is necessary
• Continuous gyro survey
• Independent initialisation
• Both in-run and out-run
SURVEY RECOMMENDATION PRACTICES
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•ISCWSA is a good source of
information and is part of SPE
please contact to
WWW.ISCWSA.NET
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Thank You
33
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Distinguished Lecturer Programwww.spe.org/dl
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