What's the best practice concerning under displacement?

Hi all,

We're setting some balanced plugs (180-200m), using 3"" tubing as cement stinger (open slanted mule shoe, no slots) ran on 5"" DP.
The hole inclination is about 47 deg.
Mud weight 1.78sg, Spacer 1.80sg, Cement 1.90sg.
Well will be on trip tank when POOH stinger after placement at controlled speed.
My current reasoning is to imagine pulling the stinger up to theoretical TOC and to ensure the spacer inside/outside string only meet at this point, and then calculate the mud volume to be displaced in the string.

I've seen an SPE article on this, No. 168005, but that calculation was assuming no filling in the annulus via trip tank pump during POOH stinger (thus losing hydrostatic pressure and leading to mud falling out of stinger prematurely). But it's not realistic in operations.
So what do you think is the proper under displacement based on what reasoning? Thank you very much!

Regards,
Yunchuan

3 Answer(s)

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