The Value of Realtime Geomagnetic Reference Data to the Oil Industry

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The Value of Real-time Geomagnetic Reference
Data to the Oil Industry

• Simon McCulloch
• Halliburton Sperry Drilling Services

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Oil rig
Sea level
3,000m
Seabed
8,000m
20m
Oil bearing sands
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60m
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Error Sources 1

• Sensor Errors
• 3 accelerometers (bias and scale factor errors)
• 3 magnetometers (bias and scale factor errors)
• Temperature related calibration errors

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Error Sources 2

• Misalignment errors
• Drillstring sags in vicinity of sensors
• Sensor package is misaligned in drillstring and
  not parallel to actual wellbore

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Error Sources 3

• Depth Error
• Drillstring strectches under its own weight
• Drillstring is subject to thermal expansion

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Error Sources 3

• Depth Error
• Drillstring strectches under its own weight
• Drillstring is subject to thermal expansion

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Error Sources 4

• Environmental
• Axial interference from drillstring
• Magnetic shielding from drilling fluid

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Axial Interference from Drillstring
X
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Axial Interference from Drillstring
X
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Axial Interference from Drillstring
X
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Axial Interference from Drillstring
X
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Axial Interference from Drillstring
X
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Axial Interference from Drillstringand Magnetic
Shielding from Drilling Fluid
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Example Raw Data
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Basic Formulae
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Total Field calculated with raw magnetometer
values
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Magnetic Dip Angle calculated with raw
magnetometer values and raw accelerometer values
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Axial Interference from Drillstringand Magnetic
Shielding from Drilling Fluid
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Example Raw Data
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Based on geomagnetic reference data we can
iteratively derive our best estimate of

• BX
• BY
• BZ
• and then recalculate our total field strength and
  dip

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Basic Formulae
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Total Field calculated with raw magnetometer
values and iteratively derived values
magnetometer values
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Magnetic Dip Angle calculated with raw
magnetometer values and iteratively derived
values magnetometer values (raw accelerometer
data used for both)
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QC on corrected data
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Uncorrected and Corrected Directions
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Survey Report
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Oil rig
Sea level
3,000m
Seabed
8,000m
20m
Oil bearing sands
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60m
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Error Sources 5

• Uncertainty in Geomagnetic Reference Values
• Uncertainty in declination
• Uncertainty in Total Field Strength
• Uncertainty in Magnetic Dip Angle

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Accuracy of a Global Model in the North Sea

Reference Source Declination Dip BT
Global Model /- 1 /- 0.4 /- 300
nT Figures quoted at the 2 sigma
confidence level
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Industry Steering Committee on Wellbore Survey
Accuracy (ISCWSA) Error Model
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60m
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Crustal anomaly field (Bc)
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Example November 2005
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Accuracy of a Global Model and IFR in the North
Sea

Reference Source Declination Dip BT
Global Model /- 1 /- 0.4 /- 300
nT IFR /- 0.3 /- 0.3 /- 100
nT Figures quoted at the 2 sigma
confidence level
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Improving magnetic survey accuracy
Using a Global Model conventional practice in
most parts of the world
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The principle of Interpolation IFR (IIFR)

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Date Time Dec Dip Total Field
08/11/04 0054 -3.494 72.003 49974.41 08/11/04
0055 -3.472 71.888 50020.58 08/11/04 0056
-3.335 71.824 50024.41 08/11/04 0057 -3.316
71.807 50028.56 08/11/04 0058 -3.284 71.784
50038.19 08/11/04 0059 -3.249 71.823
50023.16 08/11/04 0100 -3.166 71.861
50003.59 08/11/04 0101 -3.110 71.871
50016.20 08/11/04 0102 -3.101 71.958
49985.85 08/11/04 0103 -3.031 72.085
49964.07 08/11/04 0104 -2.938 72.137
49965.79 08/11/04 0105 -2.896 72.168
49993.32 08/11/04 0106 -2.623 72.157
50008.57 08/11/04 0107 -2.496 72.025
50060.56 08/11/04 0108 -2.269 71.954
50061.21 08/11/04 0109 -2.090 71.905
50050.16 08/11/04 0110 -1.939 71.860 50043.92
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This slide shows the behaviour of the
Earths Magnetic Field on Sunday, November 7,
2004. Note that a fairly strong magnetic storm
began in the evening. What happened in the
ensuing 4 days proved to be one of the 3 most
intense magnetic storms seen in Norway in 2004.
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This slide shows the behaviour of the
Earths Magnetic Field on the Monday, November 8,
2004. The storm continued until about noon that
day.
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During this time Sperry-Sun was drilling several
wells for several customers in Norway. Customers
who were using the IIFR service were able to
drill ahead as normal during this storm as the
behaviour of the Earths Magnetic Field was being
calculated at the position of the rig,
minute-by-minute.
Date Time Dec Dip Total Field
08/11/04 0054 -3.494 72.003 49974.41 08/11/04
0055 -3.472 71.888 50020.58 08/11/04 0056
-3.335 71.824 50024.41 08/11/04 0057 -3.316
71.807 50028.56 08/11/04 0058 -3.284 71.784
50038.19 08/11/04 0059 -3.249 71.823
50023.16 08/11/04 0100 -3.166 71.861
50003.59 08/11/04 0101 -3.110 71.871
50016.20 08/11/04 0102 -3.101 71.958
49985.85 08/11/04 0103 -3.031 72.085
49964.07 08/11/04 0104 -2.938 72.137
49965.79 08/11/04 0105 -2.896 72.168
49993.32 08/11/04 0106 -2.623 72.157
50008.57 08/11/04 0107 -2.496 72.025
50060.56 08/11/04 0108 -2.269 71.954
50061.21 08/11/04 0109 -2.090 71.905
50050.16 08/11/04 0110 -1.939 71.860 50043.92
and the storm continued..
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on Tuesday
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and on Wednesday
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It really took until Thursday before the field
returned to a fairly undisturbed condition.
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During this time many people enjoyed impressive
sightings of the Northern Lights.
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Customers who took advantage of the IIFR service
were able to continue drilling almost as normal.
Date Time Dec Dip Total Field
08/11/04 0054 -3.494 72.003 49974.41 08/11/04
0055 -3.472 71.888 50020.58 08/11/04 0056
-3.335 71.824 50024.41 08/11/04 0057 -3.316
71.807 50028.56 08/11/04 0058 -3.284 71.784
50038.19 08/11/04 0059 -3.249 71.823
50023.16 08/11/04 0100 -3.166 71.861
50003.59 08/11/04 0101 -3.110 71.871
50016.20 08/11/04 0102 -3.101 71.958
49985.85 08/11/04 0103 -3.031 72.085
49964.07 08/11/04 0104 -2.938 72.137
49965.79 08/11/04 0105 -2.896 72.168
49993.32 08/11/04 0106 -2.623 72.157
50008.57 08/11/04 0107 -2.496 72.025
50060.56 08/11/04 0108 -2.269 71.954
50061.21 08/11/04 0109 -2.090 71.905
50050.16 08/11/04 0110 -1.939 71.860 50043.92
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Customers who did not take advantage of the IIFR
service wasted a lot of time repeating and
repeating surveys in an attempt to catch a good
survey.
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Solund
Lerwick
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Karmøy
Eskdalemuir
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Comparison in northern North Sea showing the
improvement of using IIFR instead of IFR for the
reference value of magnetic dip angle
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Accuracy of these 3 methods in the North Sea

Reference Source Declination Dip BT
Global model /- 1 /- 0.5 /- 350
nT IFR /- 0.3 /- 0.3 /- 120
nT IIFR /- 0.2 /- 0.1 / 70
nT Figures quoted at the 2 sigma confidence
level
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60m
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IIFR - data flow
Drill Site
Lerwick (BGS)
Solund (TGO)
ACQUISITION
Measure local geomagnetic field
Measure local geomagnetic field
Acquisition of raw magnetic MWD data
BGS (Edinburgh)
PROCESSING
Survey Management
IIFR data
Interpolate for the drill site location
Process Surveys

DD and MWD
Compass Definitive Database
END USER APPLICATION
DELIVERY
Receive corrected surveys within 20 minutes
Updated once per day
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Real Time Survey Management Centre in Tananger
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Real Time Survey Management Centre in Alaska
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The Value of Real-time Geomagnetic Reference
Data to the Oil Industry

• Simon McCulloch
• Halliburton Sperry Drilling Services