Milling window G2 XL mechanical whipstock at 74deg inclination at 1700mMD

Hi ,

We are planning to sidetrack with whipstock on the original ERD well (single 13-3/8" casing exit). Drilled a long tangent 12.25" hole before build up to targeted sand.  

Plan to set the whipstock Gravity TF @ 30-45deg right.  Sidetrack and drill parallel to the original wellbore.

Tri-mill with silverback for milling window.  Upper Mill 12.25" - Lower Mill 12" - silverback 12.25" Mill BHA about 9m (with flex joint betw UM and LM).  

Plan to drill a long rathole about 33 to 35m for our drilling BHA.  Our whipstock vendor seem to think we should drill short rathole (reason given was milling BHA will drop the inclination too much) and run in with rathole BHA to extend the rathole for Drilling BHA.  This is additional run that will cost rig time.

Drilling BHA with Geopilot - RES - GyroWD about 33m in length. 

We would like to hear any lessons learned specifically related to milling BHA too flexible versus Stiff drilling BHA resulted in passthrough problem.  Obviously, it would be ideal if we finishing milling and drilling 35m rathole in one run.  Mills coming out in gauge and run the drilling BHA in subsequent run without problem.  

I have proposed to whipstock vendor to put a 12-¼" or 12-1/8" String stab and 8" DC directly on top of milling BHA to emulate the same stiffness as drilling BHA.  Their standard answer is Not recommended.

Thank you in advance for sharing.

6 Answer(s)

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