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‘Disruptive’ bit technology aims at stick-slip elimination

By Mike Killalea, Editor and Publisher

Figure 1: See-through model showing depth-of-control cartridge. The piston-like cartridge features a button protruding from the business end of the bit to sense and adapt to changes in the formation that could cause stick slip.

Figure 1: See-through model showing depth-of-control cartridge. The piston-like cartridge features a button protruding from the business end of the bit to sense and adapt to changes in the formation that could cause stick slip.

A new drill bit designed to eliminate stick-slip constitutes a “disruptive” technology, officials at Baker Hughes said. The new PDC TerrAdapt bit, first reported on DrillingContractor.org, features spring-loaded “adaptive depth-of-control cartridges” within the bit’s three fixed-cutter blades to prevent sudden changes in depth of cut (DOC) (Figures 1 and 2). The product was launched at the 2017 SPE/IADC Drilling Conference, held during March in The Hague, Netherlands.

“With TerrAdapt, we’re going to the source of a problem… We’re going to the bit, and we’re changing the control response of that bit such that the (stick-slip) patterns are never allowed to establish themselves,” said BHI Technology Director-Drill Bits Mark Freeman. “We absolutely think it’s disruptive.”

Stick-slip is a vibrational problem that can occur with PDC bits when the bit’s cutters “stick” in the rock, causing the drill string to wind up like a spring. Eventually, sufficient energy is absorbed by the “spring” that the bit is freed, rapidly unwinding the string. Stick-slip can cause significant downhole failures to the bit, tool joint and other components, resulting in costly and time-consuming trips out of the hole.

While many mitigation solutions exist, Baker Hughes contends that TerrAdapt prevents slip-stick conditions from the outset and is, thus, a game changer.

Figure 2: Depth-of-control cartridge highlighting button used to sense changes in formation. The button compresses the piston-like cartridge.

Figure 2: Depth-of-control cartridge highlighting button used to sense changes in formation. The button compresses the piston-like cartridge.

TerrAdapt is an “autonomination” device, explained BHI VP-Drill Bits Scott Schmidt. Autonomination describes a device that senses and adapts to the external environment, in this case conditions downhole. Mr Schmidt said that work began companywide in 2014 on what he termed a “wildcat” challenge to the entire company to overcome the stick-slip problem.

“A team from this particular product line, drill bits… actually won the challenge,” Mr Schmidt said.

Each of the three spring-loaded cartridges is tipped with a button protruding from the blade, Mr Schmidt said. This element, manufactured from diamond, can move and adapt to well conditions.

“A good analogy is a seat belt,” he said. “When you yank out a seat belt, it doesn’t go. When you pull it out gradually, it comes out.” He added that when the cartridge senses resistance in the formation, it prevents deep cuts and avoids overloading the cutting structure.

Figure 3: Comparison from Delaware Basin case history showing minimal changes in torque for TerrAdapt versus a “standard” PDC bit.

Figure 3: Comparison from Delaware Basin case history showing minimal changes in torque for TerrAdapt versus a “standard” PDC bit.

“It’s able to absorb the shocks in a much better way,” he said.

Baker Hughes cites impressive data from case histories. In one such example, from the Delaware Basin, the company claims that by mitigating stick-slip, the bit increased efficient drilling time by 45%, generated 35% lower surface torque, completed the entire run with zero nonproductive time, improved ROP by 27% and reduced torque variation by 90%. Figure 3 shows surface data from the 1,710-1,780-ft interval.

What’s been the industry reaction to date?

“We received four orders this morning,” a pleased Mr Schmidt said.

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