While designing a development plan for a field that was underneath a city, major engineering and design stumbling blocks were encountered for the extended-reach drilling (ERD) prototype. There was also the risk of encountering shallow gas and high concentrations of hydrogen sulphide gas across different formations in the field. Hence, the biggest challenge for the field development plan was to develop a well construction design that would provide well integrity and at the same time allow running casings and completions to the desired depth. In addition, different hole sections were experiencing well control, loss circulation, and wellbore stability issues all at once, resulting in a loss of well integrity or total lost circulation. This was making torque and drag unmanageable, which meant inability to drill, run conventional or drillpipe conveyed wireline logs, or run casing and completion. Also, there was a high incidence of stuck pipe events due to wellbore stability issues and hole cleaning problems in a lost circulation scenario. Due to the torque and drag limitation, performing a sidetrack was not an option in the field. In this operation, an extensive offset well analysis and comprehensive risk assessment was done to put together an innovative well construction design and a customized drilling procedure that would lead to successful drilling and completion of a world-class ERD well under high-to-total loss circulation scenario. The selection criterions for technologies for the BHA and the drilling procedures were based on the specifics of designs and highlighted how a predrill geomechanics modeling, a drilling liner application, fit-for-purpose equipment selection, optimized well placement, judicious casing flotation, advanced logging-while-drilling technology application, and tailored drilling practices that not only made an undrillable well drillable but also set a new industry limit to run smart-completions.

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