Published: 02/23/2018
Published: 02/23/2018
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.
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.
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.
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.
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.
Results:
