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?