In the long tophole section of vertical wells in Abu Dhabi, formation challenges historically have caused roller cone bits to suffer impact and fatigue damage to the gage and cutting structure. As a result, at least two bits have been required to drill the 4000-foot section, which is composed mainly of carbonates with a thick anhydrite section.

In addition to high impact damage, the carbonates also generate high friction on bits that exacerbates thermal degradation to the cutting materials, launching a series of consequences that inevitably result in premature bit failure.

In addition, lost circulation is very common in this application, so determining optimum operating parameters is more challenging.

Given these conditions, the operator's stated objective was to drill the 17-1/2-in. interval "shoe-to-shoe" in a single bit run, optimizing penetration rate without compromising hole quality or cleaning efficiency.

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