Azimuths and Magnetic Drift
Expedio’s Top Tip for April understanding Azimuths and Magnetic Drift:
Managing azimuths and magnetic drift is very important in maintaining the integrity of your downhole survey data.
Steps in managing azimuths and magnetic drift correctly:
- Correctly reference azimuths recorded – Is the reading measured in True north, Magnetic north or Grid north. Incorrectly collecting and storing this data will have a massive effects on the quality of the data set.
- Know the magnetic north to grid north conversion – Magnetic declination tells you the direction of magnetic north, measured from true north, and convergence tells you the direction of grid north, measured from true north. For example countries such as Brazil have a 23 degree swing between national grid north and magnetic north. Get this wrong and you will miss your target.
- Be aware of magnetic drift – Variations in the Earth’s outer core results in changes to the magnetic field and hence the position of the magnetic north and south poles over time.