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Casing Magnetization
12 December 2019

We are assessing the impact of magnetized casing (mitigation for relief well / PMR in salt) on the drilling operation:

- Handling / storage: interference with MHWirth (pipe handling), rig floor gauges and sensors, rig cameras
- Interference with Torque Turn Computer during M/U
- Interference with LWD tools (hot spot creation on the BHA). THIS IS OUR MAIN FEAR

For this of you with experience of handling and running magnetised casing, or who have encountered the concerns above, we'd be delighted to hear from you.



3 answer(s)
Consultant [retired Shell staff]
SPREAD Associates
Total Posts: 273
Join Date: 02/09/05
 See SPE 17255 Improving Detectability of blowing wells 

Also: I was lead to believe that only the bottom three joints of casing i.e. the shoe-track, would have to be magnetized.
Consultant Driling Engineer / ERD Advisor
Stanfield-Hayes Consulting
Total Posts: 45
Join Date: 25/03/11

I looked into this a few years back to look into options to manage relief well intersection risks. The proposal we came up with was to use a customised magnetic pattern specifically to maximise the ability to passively range based on the well design. We would design the intersection a few 100 ft back from the shoetrack, such that the M/LWD string could be run through, but wouldn't spend significant time in the casing. The vendor did require that collar magnetism before/after runs was measured to assess magnetic 'damage'. 

In terms of preparation and storage the plan had been to have a segregated area in the our pipe yard to perform the magnetisation, then manage logistics such that the casing would not be loaded out with magnetically sensitive equipment and then on the rig to ensure that the casing was kept away from the M/LWD/DD equipment. As we were running dual derrick and racking the casing back, one performance limitation identified was that we would have to have to pick up the magnetised casing online rather than offline.

I don't think we got any negative feedback from the rig on interference with rig equipment with running the casing, Though in the end we didn't go ahead with implementing the project as we found better more cost effective solutions at the time, so never got any actual in-situ evidence of the impacts of custom magnetised casing.
Senior Wellbore Positioning Advisor
Helmerich & Payne
Total Posts: 40
Join Date: 03/07/08
I have some experience in intentionally magnetizing casing to increase the range of PMR.   It is difficult to get equivalent monopoles greater than a few thousand microWebers.  Larger poles will tend to self-demagnetize rather quickly.  This is only marginally more than is sometimes left on the casing by magnetic inspection.  Have you measured the residual magnetization of the casing you are currently using?

PMR requires an adequate signal to noise ratio to get a signature that can be interpreted.   Typical MWD tools can only resolve 30-100 nanoTesla.   Specialized wireline tools can resolve signals an order of magnitude less than that, which will also increase the detection range.

I have seen high magnetization on old wells in the North Sea, where apparently electromagnetic pipe handling equipment had been used.

We can speculate that the steel parts of a BHA could become magnetized by running through highly magnetizied casing.  I doubt this will be nearly as effective as the intentional magnetization during magnetic particle inspection.  This question can only be answered by actually measuring the residual magnetization of BHA components before and after each run. 

Best Regards,
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