Performance Comparison of Rolling-Cutter Bits With Alternative Nozzle Designs

Abstract

Controversy exists regarding the optimum nozzle design for rolling-cutter bits. This paper describes the use of controlled laboratory conditions to isolate the true benefit of various hydraulic designs. Tests were conducted in a pressurized drilling environment with 9Ys-in. [2S1-mm] tooth and insert bits in Mancos shale. Hydraulic designs include combinations of standard-and directed-nozzle bits with center jets and long and short extended-nozzle bits. Results indicate that directed nozzles provide substantially better bit cleaning and rate of penetration (ROP) than the standard-and short extended-nozzle designs and a slightly faster ROP than long extended-nozzle designs.