Reentry wells are drilled routinely in mature fields. On some occasions, drilling the reentry well is complicated by unexpected casing wear in the motherbore or restrictions above the planned kickoff point, which might be due to junk in the hole, sagging, casing collapse, or ovality. In this paper, we present an actual case where a reentry well design was affected by such a restriction and how this challenging situation was overcome efficiently.

This paper will:

  • Present the consequences of the restriction on the reentry well design, initially planned with its 12 ¼-in. section and 9 5/8-in. liner.

  • Describe the solution designed to pass through the restriction and deliver a reentry well design as near to the initial plan as possible, including an innovative undersized whipstock design, 10 5/8×12¼-in. hole section with a dual-reamer assembly, leaving a marginal 10 5/8-in. rathole and a little 11¾-in. rathole, and real-time near-bit directional data sent across the lower reamer.

  • Summarize the risks and compensating measures associated with the designed solution, including shocks and vibrations leading to tool failure and trip, limited record of directional work available with such a design; i.e., a section longer than the vendor’s world record for this dual-reamer size and running 9 5/8-in. liner in the 11¾-in. rathole.

  • Present the successful operation results obtained by using the dual-reamer assembly, fit-for-purpose directional capability, and successful casing run to total depth. This was the longest 10 5/8×12¼-in. run with a dual-reamer assembly, also known as rathole elimination assembly, performed by the vendor worldwide and the section was drilled and completed ahead of schedule and below budget.

  • Highlight the main drivers that make this custom-made solution portable for applications in other situations.

This case study demonstrates how close collaboration between the operator and wellbore departure and directional drilling vendors led to an innovative whipstock and an aggressive drillstring design delivering a proper sidetrack and a fit-for-purpose borehole in one run. This collaboration turned a challenging situation into a successful drilling operation by minimizing the effects of a potentially harmful restriction.

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