Stack-bearing technology significantly reduces drilling downtime

Ceradyne has acquired a proprietary technical ceramic bearing technology that will offer operational improvements for drillers and producers alike. The company's stack-bearing technology promises higher load capacity and longer service life than conventional hydrodynamic thrust bearings can offer.

Ceradyne purchased the stack-bearing technology from Rhode Island-based Ride Technologies. Russ Ide, a key inventor of the stack-bearing technology and Ceradyne's new product manager for the stack-bearing product line, explained the key differences between his innovation and other thrust bearings.

"With rolling-element bearings, the balls and races are manufactured to extremely tight tolerances. Abrasives in the mud lubrication cause the balls to skid rather than roll, which accelerates wear. With even small amounts of wear, the balls become unequally loaded and wear out quickly. Stacking only exacerbates the condition by causing one or two bearings to carry the full load and exceed their given capacity."

Ceradyne's stacked ceramic thrust bearing assembly.

The Ceradyne stack bearing is different in that it incorporates a spring mounting component that allows for equal load sharing across each bearing pad and between stacks. "Each thrust-bearing element can be stacked using a spring mounting that equally loads each of the bearings to about 1,000 psi," said Ide. "The load-sharing element of the patent allows us to achieve virtually any thrust load within a diametrically limited space. In our experience to date, there is not much restriction in terms of axial length, so you can just keep on adding thrust bearing after thrust bearing for increasing thrust loads."

For example, it would be nearly impossible for a typical hydrodynamic bearing operation to support 1 million lbs of vertical load on a 6-in. diameter string. With the stack bearings, "we can place 1,000 pads in there, and each one will only experience 1,000 psi of load, which is very sustainable," Ide continued.

The equal load sharing afforded with the spring mounting is one partner in a technology marriage, according to Ide. "The other component is the advanced technical ceramic, silicon carbide, that we use for the element bearings," he said. "Because the ceramic is so hard, you don't see the same abrasive wear that you see with rolling element bearings. We've even tested them in the presence of quartz sand and typical mud lubrications, and there is no abrasive failure. The abrasives just polish the surface." In addition, the technology uses one of Ceradyne's advanced grades of silicon carbide, which is 50% tougher than other commercially available grades.

The stack bearings can also be manufactured from more conventional bearing materials such as bronze, steel, or various polymers. Because the bearings can be stacked such that each one experiences a low individual load, they can be operated without any oil as a lubricant. "In a deepwater application, you could lubricate with seawater and still get extremely good load capability," Ide added, "which provides an environmental benefit by avoiding the need for oil lubricants in ecologically sensitive areas."

Drillers and producers can benefit

Ceradyne sees application for these stack bearings in both exploration and production. "For the exploration side, directional drilling in particular, they are replacing the angular contact style bearings that wear out after maybe 100-200 hours," Ide said. "We have not had one of these fail yet in this application, and we've designed these to take virtually any vertical load."

On the production side, the stack bearing is aimed at pumping systems for steam assisted gravity drainage (SAGD), coal bed methane, and artificial lift applications. "In pumps for SAGD applications, we've been asked to provide bearings that last two years. However, if they are installed and maintained properly, you're probably looking at five to ten years of service life," Ide said.

In the event that the elements need to be replaced, it is typically due to corrosive failure of the steel housing surrounding the bearing elements rather than a mechanical defect with the bearings themselves.

This durability of the bearings has been a major advantage during a tar sand operation. "In the event that the mechanical seal is compromised and tar and sand enter the bearing cavity, the bearings will just keep operating," Ide confirmed. "We've had some tar sands operators running these months after they've lost integrity in the mechanical seals."

The durability of these stack bearings has already caught the attention of several oilfield service providers. The technology has been qualified by several oilfield pump manufacturers, both domestically and internationally. "By taking advantage of the high temperature tolerance of our stack bearings, they can inject steam into old holes and quickly double production, achieving 60-80% oil recovery in some places," said Ide.

Ide concluded with a discussion on the unit- and operational-cost benefits with the stack-bearing technology. Diamond bearings are typically two to three times the cost of the stack bearings, and they experience load limitations due to an upper limit on stacking. Stack bearings are in the same price range as conventional hydrodynamic roller bearings, but the major cost advantage comes from a significant reduction in drilling downtime.

"You can run and finish the hole without having to pull up the string and replace the worn ball bearings," Ide said. "An operator can plan downtime instead of being surprised by it."

To learn more about Ceradyne's stack-bearing technology, contact Russ Ide by email at ride@ceradyne.com or visit www.ceradyne.com.

 Ted Moon is the Technology Editor of JPT Online. He brings information on emerging technologies, R&D successes, new field applications, updates from SPE papers about recent innovations, and more. If you have a question or suggestion for future article topics, email Ted at teched@spe.org.