We have been running the Archer Tornar tool after milling windows (both for 13-3/8" & 9-5/8" casings exits) for our subsea wells. Typically running the tool 2-3 times until only residual swarf remaining on the magnets to ensure BOPs as clean as possible.
Also run string magnets in the whipstock milling BHAs (either just below BOP or at top of HWDP) as a preventative measure to limit the amount of swarf that can get to the cavities in the first place.
For the 30+ semi-sub section milling jobs we conducted for the HEss abandonments, we used the Coretrax combination Jetting / Magnet tool to clean up the BOP stack
Only the occasional swarf chip was found upon opening up and nothing in the controls side.
As relevant slide won't upload but feel free to contact me if you require more information.
As for ditch magnets, we used several racks of Romar EZ Clean magnets - the racks are made to suit your requirement and the design of the magnet is safe and easy to clean (hence the name I guess!!)
Hope this assists......cheer PT
As mentioned most of the main service suppliers provide these cleanup tools all be it with certain nuances . Magnets would be beneficial with a jetting tool that is nozzled to provided various flow angles.
The Tornar by Archer is one that I have come across that is different to others (or just better marketing) and has been utilised for some heavy cleanups here in Norway. http://archerwell.com/product-service/oiltools/well-cleaning/wellbore-cleaning/.
Having magnets in the BHA that are ribbed are beneficial for cleaning similar to ones used by MI.
All of the major suppliers of wellbore cleanup tools (MISwaco, BHI, Halliburton) plus the smaller suppliers (such as Odjfell, Archer etc) should be able to supply this without issue.
Not so sure about a single tool with integral swab cups but they all have tools under names similar to “surface junk catcher” which you can run below a BOP jetting tool.
The ”surface junk catcher” will have a swab cup, or tight interference fit part (depending on supplier and relevant patents) that contacts the casing.
For efficiency you can have the assembly made up in the workshop prior to delivery to the rigsite. We ran this assembly regularly on the BP Tangguh phase 1 project (which you may be familiar with through the Technical Limit coaching contract that you had there).
If it is a milling operation and swarf is the concern I would supplement the BHA with some string magnets.
Also may be worth looking at the openholenet by 5D magnetics (http://www.5doilfieldmagnetics.com/).
In reference to your comment on the use of ditch magnets, 5D also have a magnetic flowline filter and Romar have Magnogrid and EX-clean ditch magnets which should resolve the issues of cleaning swarf without the use of socks. (http://www.romarinternational.co.uk/ditch-magnets/ez-clean/)
I too have had a good success with the well Patroller - also, use a couple of string magnets.
On the subject of magnets - I have had good experience with Romar magnets - these are finger magnets and can be supplied with a pull-to-clean sleeve which allows you to pick them out of flowline and simply pull a handle and the swarf falls into a bucket. These should be sufficient for a simple window-mill.
I'd steer clear of the big 56 lb magnets which are difficult to handle - you can probably still put one in the flowline downstream of the Romar ones just in case, but they are a pain to clean.