2018 Offshore Technology Yearbook

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32 | December 2017 | 2018 OFFSHORE TECHNOLOGY YEARBOOK | DRILLING TECHNOLOGY Block advanced stabilization conical element cutter block along with providing a cutting structure that increases overall durability and allowing it to last longer and drill faster. The StingBlock cutter is essentially the cutting structure of the Schlumberger Rhino integrated borehole system. There are a few key features that are used on the StingBlock cutter to better stabilize the BHA and improve the overall cutting structure dura- bility. The underreamer has the company's propri- etary staged profile, which helps to better distribute the cutter loads and to stabilize the overall cutting structure element, explained Wiley Long, product champion for StingBlock cutter for Schlumberger. "You can imagine it as multiple gauge pads as you go up the cutting structure. Increasing that gauge pad area helps smooth out vibrations during underreaming operations. Our experience shows that the majority of damage that occurs on the reamer cutter structure is due to impact damage. For the cutting structure we've taken a page out of our bits playbook and incorporated the Stinger conical diamond. The Stinger conical element has a much superior impact resistance than a conven- tional PDC cutter," he said. In a conventional under- reaming-while-drilling BHA, the assembly is susceptible to vibration because of the great distance between the two cut- ting structures drilling simul- taneously—the underreamer is typically about 150 ft from the bit. Because of the dis- tance, quite often the tools will be drilling in different kinds of rock, which can gen- erate a lot of vibration into the drillstring, he explained. What helps reduce vibra- tion are the staged pads that better stabilize the cutting structure. It provides more contact area for the cutting block and the extra level of stability that is needed. The rows of PDC cutters on its conventional reamers are symmetrical. "Sym- metry might sound nice but in things with moving parts it can be susceptible to harmonic vibration levels. With StingBlock cutter we're creating an alignment with PDC cutters and Stinger elements more broadly distributed across the width," he noted. Schlumberger devised a different system that would incorporate two Rhino StingBlock ream- ers into the same BHA. It is called the Rhino RHE rathole elimination system. "For that system you have your top Rhino reamer in the conventional location above the LWD tool. Your second Rhino reamer would be just above the RSS about 20 ft to 25 ft from the bit," he continued. The top reamer would be used while drilling the majority of the interval. Once the bit reaches total depth the upper reamer is deactivated, and the lower reamer is activated. "We can then underream that 120 ft-plus of rathole and eliminate an addi- tional trip to underream that rathole," he added. In the MWD and LWD tools there are sensors measuring vibration. In lab tests and field opera- tions the company found the ability of StingBlock cutter to reduce vibration levels. The StingBlock cutter block is the industry's first geometry cutter block that features a stage gauge pad design and Stinger conical diamond elements. (Image courtesy of Schlumberger)

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