Enlarge borehole through challenging formation

In a presalt exploration campaign, offshore South America, the operator faced a unique challenge in the planned hole-enlargement-while-drilling (HEWD) operations. The 2,200-m- [7,218-ft-] thick postsalt section at the well location dictated that HEWD operations for the 18 1/8-in to 22-in borehole would occur in the long interval extending from the Neo-Cretaceous through the Aptian saline strata. This section includes hard and abrasive lithologies, such as interbedded sandstone and shale, marl with shale lenses, and calcilutite stringers in the underlying salt. Drilling in high-compressive-strength igneous rock can produce high shock, lateral vibration, and severe stick/slip events in the drilling system. Consequently, the operator wanted to mitigate the anticipated drilling shock/vibration associated with underreaming through the challenging strata without compromising drilling efficiency.

Set new benchmark, outperforming best offset run

With the new StingBlock cutter block, the operator drilled 294 m [964.5 ft] through the hard and abrasive postsalt interval—55% more than the goal set by the customer—and achieved an average ROP of 5.25 m/h [17.22 ft/h]—110% higher than subsequent runs with the conventional cutter block. Using surface and OptiLog BHA dynamics recorder data, the team performed a full postjob analysis of the run. The outputs from this analysis that demonstrated the benefits derived from the new cutter block: improved durability, higher cutting structure aggressiveness, and reduced lateral vibration and stick/slip events.