In several Canadian applications, operators have recognized the potential to replace standard roller cone products with a more viable solution that will drive down costs when drilling straight hole and curved sections. In these high-abrasive applications, roller cone bits are preferable because of their ability to increase ROP while maintaining a controlled direction and their relatively low price compared to polycrystalline diamond compact (PDC) bits. Typically, roller cone bits are removed from service because of damage or wear to the bearings or seals, and/or to the cutting structures. However, in these applications, the weakness occurs in the leg section.

Historically, wear protection on the leg outside diameter (OD) was achieved by placing tungsten carbide inserts in vulnerable locations. Although this increased wear resistance, the softer portion of the leg OD was still exposed to the damaging effects of hole-wall contact due to the required spacing between the tungsten carbide inserts. Also, the required drill holes for the inserts could become crack-propagation points in certain drilling environments.

To improve the durability of the leg while increasing seal and bearing reliability, abrasion-resistant hardfacing was incorporated onto the majority of the leg OD. Roller cone bits with the new hardfacing leg protection were field tested in several operators' wells with excellent results. The hardfacing leg protection proved to reduce OD wear more than TCI leg OD protection, therefore providing improved seal and bearing protection and thus reliability. Additionally, the hardfacing configuration stiffens the leg, increasing durability by reducing flexing and the potential of leg breakage. By preventing early bearing failure due to abrasive leg wear, this innovative technology has caused a performance paradigm shift and has significantly driven down drilling costs and non-productive time. The authors will present several case studies that document how the unique technology has increased the overall leg protection of roller cone products resulting in improved seal protection. This has led to an increase in total footage drilled in some applications and substantial cost savings to operators compared with standard roller cone products in those applications that do not have the new hardfacing.

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