Summary:
- Magnetic mud affects the magnetic survey
- A base model: predictable cross-axial attenuation
- Difficult to apply
- Not included into the error model
- Some practices in place to avoid the problem
- I have 3 more years full-time to sort it out
The magnetic drilling mud:
- When the drilling mud is contaminated by magnetic materials, it become itself magnetic
- A magnetic mud alters the geomagnetic field at the MWD assembly
- Thus inducing an error in the magnetic measurement
- The problem is known since 20 years, SPE71400, SPE87169, SPE113206, etc.
- Many gaps in understanding the effect and in predicting the error
Occurrence:
- Only when doing magnetic survey..
- Magnetic ingredients in the mud recipe (Ilmenite, Hematite, contaminated batches)
- Heavily used mud
- Error enhanced when drilling at high latitudes
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Giorgio Pattarini