Unplanned sidetracks while enlarging the hole with a drillbit


We have a customer who wishes to enlarge the hole from 12 1/4" to 22" with a rotary BHA.The BHA proposed is packed hole assy with tricone bit without a hole opener in the assembly  The trajectories are vertical at this point. Total interval to be drilled is about 700 m.

Top 400m of the lithology is clay/sandstone and bottom part is dolomitic limestone

We are conscious that this represent a risk of sidetracking the well and would would like to minimize the risk by leading a bullnose into the hole with a stabilizer and enlarge with a hole opener. Our customer has opened the hole using the bit in the past and doesn't see the point in a hole opener deployment.

Can anyone share best practices out there with enlarging such hole size in rotary BHA without hole opener and still manage to avoid risk of sidetracking?



5 Answer(s)

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