Double-section, non-retrievable casing drilling technique

With the continuous surging in daily rental rates of oilfield exploration rigs, Casing while Drilling technology—which provides operators with an alternative drilling solution for a reduction in drilling flat-time and increased drilling operation efficiency—has appeared to be a standard part of drilling engineers’ toolkit in the well-planning process. Significant cost savings generated by Casing while Drilling have contributed to this technique being widely deployed on top-hole string installations on exploration and appraisal wells in the southeast Asia region. The double-section casing drilling technique has gained increasing popularity among operators in recent years; however, this technique development has been hamstrung by limited casing bit selections. An improved design casing bit has been highly anticipated in the industry to reduce this technique’s complexity of drilling process. Finding an equilibrium between durability and drill-out capability features for a casing bit has been a major challenge for bit designers. The increasing prospect and demand for a double-section casing drilling technique, however, has yielded the development of the casing bit design to a wider portfolio, inclusive of a more robust PDC (polycrystalline diamond compact) cutter-based drillable casing bit. The introduction of the new robust but drillable PDC cutter-based casing bit has broadened the Casing while Drilling application. The double-section casing drilling technique without the need for an additional conventional clean-out trip has become a strong contender to be part of drilling engineers’ next toolkit in delivering enhanced drilling performance and increasing operational efficiencies. This paper will introduce the first case history of the successful planning and implementation of the double-section casing drilling technique—particularly emphasising its optimised drilling performance and ease of drill-out without the need for a specialised drill-out bit.