Overview
- Wellbore position uncertainty
- SD and HD geomagnetic models
- In-Field Referencing methods
- Shortcomings of plane grid methods
- Global ellipsoidal harmonic method
- Texas and Alberta aeromagnetic survey examples
Positional Uncertainty in MWD
- Largest source of lateral error: Magnetic field
- Accurate geomagnetic models and advanced corrections significantly reduce this error
Ellipses of Uncertainty Study
Uncertainties in Middle East
Main Field Commission Error
- Only shown is the commission error of the main field. This does not include errors from omitting the crustal field.
- This demonstrates the importance of using annually updated models
Crustal Anomalies: The Old View
Geomagnetic Power Spectrum
Representing the Magnetic Field
- Magnetic field vector represented as gradient of a potential
- 𝑩 = −𝛁�
- Potential satisfies LaPlace’s differential equation:
- 𝛁2𝑉 = 0
- Harmonic functions satisfy LaPlace’s equation
- Sphere: Spherical harmonics
- Ellipsoid: Ellipsoidal harmonics
- Plane: Harmonic waves
....
View the entire Presentation:
Managing Main & Crustal Magnetic Fields and New Developments in Global Magnetic Modeling
Stefan Maus