Case Study: StingBlock Cutter Block Improved HEWD Performance for Large-Bore Presalt Well, Offshore South America

Innovative cutter block design delivers superior performance in interbedded hard and igneous rock strata

Challenge: Enlarge borehole and minimize shock and vibration while drilling through hard and abrasive formations interlayered with igneous formations.

Solution: Use the StingBlock advanced stabilization conical element cutter block in the Rhino integrated borehole enlargement system to increase cutting structure durability and improve ROP and stability.


  • Enlarged 294 m [964.5 ft] with an average ROP of 5.25 m/h [17.22 ft/h].
  • Achieved lower levels of shock and vibration compared with the best performance in offset runs.
  • Exceeded customer goal for ROP and footage.

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.

Increase ROP and cutting structure durability with innovative cutter block

Schlumberger recommended using the unique-geometry StingBlock conical element cutter block, specially designed for challenging drilling applications with a high risk of vibration and excessive damage to the cutter block and BHA. It is incorporated into Rhino integrated borehole enlargement systems, and its staged-gauge pad design distributes the forces of the cutter block more evenly, enhancing stability and reducing lateral displacement and vibration. Positioned across the cutter block profile are Stinger conical diamond elements to deliver a concentrated point load on the rock.

StingBlock Cutter Block Chart

The StingBlock cutter block significantly outperformed the conventional cutter block used to underream the offset runs.

To maximize drilling efficiency and performance during the drilling operation, a multidisciplinary group comprising Schlumberger and customer team members was formed to continuously monitor drilling performance in real time.

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.

Download: StingBlock Cutter Block Improved HEWD Performance for Large-Bore Presalt Well, Offshore South America (0.16 MB PDF)

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