Magnetic mud causing MWD surveys to fail QC

18 October 2014 Does anyone have any practical advice for avoiding or reducing the problems due to "magnetic mud"?  This has been a problem in the North Sea, and has been reported in South Texas.  The problem seems to be finely dispersed iron particles (from casing wear) in OBM.  The effect is to "shield" the MWD magnetometers in the cross-axial direction.  Reductions of 2% in the measured field have been reported.  This is not seen when the mud is circulating, but only when a stationary shot is taken.

I have little experience with this personally, but we have started to drill in an area where this problem has been reported.  On a recent well I saw MWD issues that may have been due to this.

Are there ways to measure the mud (either in lab or field) to evaluate this problem?  Ways to reduce it other than changing out the mud system frequently?

The cross-axial effect can be corrected for if it is recognized, but if there is also axial drill string interference it is problematic to separate the two effects.

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