PDC bits have afforded drillers a means to improve penetration rates in many applications. However, previous attempts to apply PDC technology in air/foam drilling environments have proven unsuccessful primarily due to excessively rapid cutter wear.

A successful test of modern PDC bit designs has been conducted in a foam drilling application of the Appalachian Basin, a widely drilled basin with well-known geological properties. The initiative included identifying applications and refining operating practices while measuring the economic viability of PDC bits in this environment. Encompassing a period of 24 months, this initiative has accumulated performance data from dozens of bit runs, with drilling cost savings and reduction/elimination of borehole deviation as its objectives.

The principle area of focus involves Ordovician period formations in eastern Ohio. Foam is the primary drilling medium with an occasional need to finish the section using light mud for well control. PDC performance has delivered an ROP increase of 300% and a 30% reduction of days-on-well. This proves the ability to reduce drilling costs with PDC bits in certain air and foam applications.

This paper details methods, results, and lessons learned from this study, and translates findings into practical techniques. Operating aspects are discussed, as well as formation characteristics and down-hole conditions. A case study is provided, including performance data and dull bit photographs.

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