Failing rock in shear is a more efficient process than by crushing, but most cutting materials can not stand up to the forces generated in the shearing process as rockstrength increases. To take advantage of the unique ability of the PCD cutter to shear rock efficiently, a concerted R&D effort supported by laboratory and field-testing led to the application ofdiamond as a shear cutting element on roller cone bits. A variety of rolling cone shear cutting elements have been developed and successfully commercialized in the last decade.
This paper will discusslaboratory results and increased field performance achieved relative to conventional crushing style diamond and tungsten carbide inserts. The authors will document through case studies increases in rateof penetration (ROP), footage, overall durability, and gauge holding ability in addition to bearing/seal effectiveness that have further reduced drilling costs and served to increase usage ofpolycrystalline diamond elements on roller cone bits. These applications range from such diverse markets as high cost offshore North Sea, to low cost North American land operations.