Eliminating Stick-Slip by Managing Bit Depth of Cut and Minimizing Variable Torque in the Drillstring

Abstract

Abstract During extended reach drilling operations, stick-slip was identified within the operator’s Fast Drill Process™ workflow as the primary performance limiter in the 8-1/2-in. hole section. This dysfunction resulted in low penetration rates, frequent downhole tool failures, and bit damage. Subsequently, multiple bit runs were required to reach interval objectives. The redesign process identified two key solutions to mitigate stick-slip vibrations. First, the bit was redesigned to limit (or manage) the depth of cut to reduce the torque variations which can excite stick-slip. Second, the torsional stiffness of the drillstring was increased by changing from 5-1/2- to 5-7/8-in. drillpipe, which reduced the magnitude of the torsional oscillations. The systematic application of these design changes allowed higher weight on bit (WOB) to be applied without stick-slip dysfunction, resulting in significantly higher penetration rates. This paper presents the results of applying depth of cut control and drillstring design to eliminate stick-slip while drilling. Weight-on-bit, vibration, and penetration rate data will be presented over the course of eight wells. Results indicate the managed depth of cut and increased torsional stiffness provided significant reductions in vibrations leading to multiple field record rate of penetrations (ROPs), improved downhole tool life, and reduced bit damage.