Paper No. 175539 Magnetic Referencing and Real-Time …...SPE 175539 • Magnetic Referencing and...

Paper No. 175539 Magnetic Referencing and Real-Time Survey Processing Enables Tighter Spacing of Long-

Reach Wells Stefan Maus, Magnetic Variation Services, Shawn DeVerse, Surcon

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SPE 175539 • Magnetic Referencing and Real-Time Survey Processing • Stefan Maus and Shawn DeVerse

Outline

• Wellbore position • Ellipses of Uncertainty • Geomagnetic field • In-Field Referencing (IFR) • Multi-Station Analysis (MSA) • Summary

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Wellbore Position

Wellbore position is important for… - Collision avoidance - Reservoir modeling - Lease boundaries

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Wellbore Position

• As a wellbore is drilled, MWD surveys consisting of depth, inclination, and azimuth are collected.

• A 3D position is computed from these survey data using minimum curvature.

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Wellbores may not be where we think

Numerous error sources in MWD measurements cause significant uncertainty in the wellbore position.

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Positional Uncertainty in MWD

The positional error is modeled as ellipses of uncertainty (EOU), calculated from ISCWSA* tool codes. *ISCWSA = Industry Steering Committee

for Wellbore Survey Accuracy

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Well Planning with EOUs

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Smaller EOUs facilitate well planning

Smaller EOUs reduce collision risk and enable closer lateral spacing

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Ellipses of Uncertainty Study

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Lateral Uncertainties in West Texas

• Error model: ISCWSA OWSG Revision 1 • 3D Ellipsoids given for 95% confidence interval = 2.79 sigma

Well Azim.

Lateral Length

MWD MWD +IFR1

MWD +IFR1+MS

(ft) (ft) (ft) (ft)

E 11000 439 390 (-11%) 173 (-61%)*

SE 11000 387 329 (-15%) 160 (-59%)

S 11000 259 161 (-38%) 129 (-50%)

*With limitations

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What Does the MWD Tool Measure?

• Compute Inclination, Magnetic Azimuth, Tool Face • True Azimuth = Magnetic Azimuth + Declination

Gx, Gy, Gz

Bx, By, Bz

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Magnetic Elements Given by Model

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Main Field Originating in the Earth’s Core

European Space Agency, Swarm Mission

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Crustal Magnetic Field as Seen by CHAMP Satellite

Vertical component of the magnetic field

MF7 Model Animation by

Rother and Maus

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Omission Error: IGRF

*IGRF = International Geomagnetic Reference Field

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Reduced Omission Error Through IFR

In-Field Referencing models are based on local aeromagnetic overflight data

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Flight lines of Permian Basin Aeromagnetic Survey

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Declination Comparison Permian Basin West

Main Field MagVAR IFR

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Declination Comparison Permian Basin East

Main Field MagVAR IFR

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Lateral Uncertainties in West Texas

• Error model: ISCWSA OWSG Revision 1 • 3D Ellipsoids given for 95% confidence interval = 2.79 sigma

Well Azim.

Lateral Length

MWD MWD +IFR1

MWD +IFR1+MS

(ft) (ft) (ft) (ft)

E 11000 439 390 (-11%) 173 (-61%)*

SE 11000 387 329 (-15%) 160 (-59%)

S 11000 259 161 (-38%) 129 (-50%)

*With limitations

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What Does the MWD Tool Measure?

• True Azimuth = Magnetic Azimuth + Declination • Magnetic Azimuth = Natural magnetic field + Interference

Gx, Gy, Gz

Bx, By, Bz

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Drillstring Magnetic Interference

The drill string is magnetized • This causes magnetic interference • Distorts MWD measurements

despite use of non-mag collars Results in significant azimuth error

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Axial Drillstring Magnetic Interference Example: Total Field = 50,000 nT Dip = 73° Declination = 7°

Southeast wellbore (plan view) Baxial = 500 nT Azimuth error = ~1.6°

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What is Multi-Station Analysis?

• With IFR, we know the magnetic reference field with a high degree of confidence.

• Now we can compare the horizontal and vertical components of the magnetic reference field model against the actual measurements by the MWD sensors.

B Measured

B Reference

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Correction for Systematic Errors Systematic errors can be corrected with Saphira MSA • Survey

measurements are recalibrated

• Azimuths are recomputed

• More stringent QC tolerances can be applied

-800-700-600-500-400-300-200-100

0100200300400500600700800

Del

ta B

Tot

al (

nT)

Measured Depth

B Total QC Plot Lateral Run 1

Measured B Total Corrected B Total

MWD+IFR Field Acceptance Criteria MWD+IFR+MS Field Acceptance Criteria

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Azimuth Corrections are Applied to Original Surveys

Saphira MSA identifies and corrects for numerous errors: • Drill string interference • Poor tool calibration • Magnetic mud • Gross measurement error • Human error

340.00

342.00

344.00

346.00

348.00

350.00

352.00

Azi

mut

h (d

egre

es)

Measured Depth (ft)

MSA Azimuth - Run 4 MSA corrected Azimuth Reported Azimuth

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New Wellbore Trajectory is More Accurate and has Reduced Uncertainty

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Planning With Standard MWD

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Planning With MagVAR IFR & Saphira MSA

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Online Oil Recovery Simulator

http://tools.magvar.com/mvrs


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Simulation results

Web simulator is available online at http://tools.magvar.com/mvrs


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Summary

• Standard MWD surveying has large uncertainties

• IFR and real-time MSA corrections significantly reduce errors • Results in more accurate wellbore spacing

• Reduced positional uncertainty

• Reduced collision risk

• Accurate wellbore placement by MagVAR IFR and Saphira MSA enables

• Drilling of long laterals with close spacing

• Denser and more accurate spacing for improved reservoir drainage

Acknowledgements The aeromagnetic surveys of the Permian Basin were

commissioned by Magnetic Variation Services and flown by Sander Geophysics and Edcon-PRJ

Questions?

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Paper No. 175539 Magnetic Referencing and Real-Time …...SPE 175539 • Magnetic Referencing and...

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