Abstract

This paper describes how recent tapered bearing innovations in rock bits have significantly increased the life of the roller-cone bit, including advanced systems analysis and an endurance record set with a recent onshore exploration run in the Middle East. This record run beat the field average by over 70% in bit revolutions and 58% in footage. One of the primary constraints with roller-cone rock bits has always been bearing life. Traditional journal bearings and cylindrical roller bearings with ball-lock cone retention result in inherent play in the system, reducing bearing and seal life. As a result, this reduces overall bit life and directly affects drilling cost through increased trips and additional drill bits needed to complete a section. Recent innovations have been made to effectively package application-specific tapered bearing technology into roller-cone assemblies. This system provides a preloaded bearing package, eliminating the damaging axial and radial play found in rock bits today. In addition, the system stabilizes the sealing interface between the head and cone, promoting extended seal life. Analytical modeling was utilized to define and simulate many different loading conditions that could be experienced downhole including reaming, up-drill, directional drilling, and high weight. Through the use of proprietary bearing analysis software, optimal bearings were developed to perform effectively across the broad range of potential loading conditions. The result is an innovative, new bearing assembly, specifically developed for rock bits, that enables significant increases in the service life of bits using roller-cones. This paper will describe real-life advantages of this technology and how it is being implemented into the drilling industry.

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