Negative Rig specific LL with Wellesley

Kallåsen (35/12-6 S) – Production section

What happened:

Tried to shear OBM mud in pits before drilling the 12 1/4″ section. At this time the well and all surface lines contained SW. Plan was to RIH with BHA in SW, fill pipe with SW, function test MWD with SW etc.

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What was planned:

Shear OBM in pits prior to drilling the 12 1/4″ section.

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What was learned:

If rig would pump OBM from mud pump into mud standpipe to shear mud in pit, one would pollute SW with OBM, and get this into well when testing MWS and filling pipe to trip in. It was not possible to split the standpipe in two, one for OBM and one for SW. Consequence is one has to shear OBM through bit and control ROP until low end rheology & 3 rpm reading are up within spec.

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What actions are required:

Do not plan to shear mud in pits in similar operations. ?