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

4

INCLINATION

5

AZIMUTH

OLD MAGNETIC TOOLS

6

MULTISHOT MECHANISM

7

Dip Angle= f(Hx, Hy, Hz, Gx, Gy, Gz)

SOLID STATE MAGNETIC TOOLS

8

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

11

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)

12

FREE GYRO

13

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

14

RATE GYRO

CONTINOUS MODE

Vertical Earth

Rotation Vector

Horizontal Earth

Rotation Vector

Gyro Sensor

Wellbore Direction

15

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

16

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

18

• 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

19

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

20

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

21

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

22

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

23

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

24

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

25

ERROR MODELS

26

•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

27

CONCLUSIONS

28

• 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.

29

• 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

30

• 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

31

•ISCWSA is a good source of

information and is part of SPE

please contact to

WWW.ISCWSA.NET

32

Thank You

33

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