Rolling Depth-Of-Cut Control Improves Tool-Face Control and Overall ROP During Steerable Motor Applications

Abstract Rolling depth-of-cut control (RDOCC) on fixed cutter drill bits can improve rate of penetration (ROP) and reduce vibrations during steerable motor applications by reducing torque fluctuations caused by sliding friction. Torque fluctuations are reduced by absorbing weight-on-bit (WOB) variations using a rolling bearing element, without generating additional torque that leads to tool-face control issues. Laboratory testing validated RDOCC efficiency compared to traditional depth-of-cut control limiters (DOCLs) by evaluating frictional force, load, and material resistance to axial and lateral forces. At the field level, potential applications, where tool-face control was identified as a drilling performance limiter, were analyzed and selected for the initial field tests. Baseline performance and target depth of cut (DOC) were determined using foot-based data. Additional drilling parameters, such as WOB, torque, and vibration, were analyzed to measure the RDOCC influence on drilling performance. The vibration data were recorded using an at-bit data collection device (ABDCD) and later compared to data from bits with traditional DOCLs. Modified bit designs that included RDOCC with rolling elements on three blades to engage at the target DOC were run in the selected applications and results compared to historical data, performance, and dull bit condition. In southeastern Saskatchewan, Canada, the curve section of Bakken wells experienced overall ROP improvement and reduced vibrations at the bit, as indicated by improved dull condition and ABDCD data. Five consecutive field record runs were achieved using bits equipped with RDOCC technology. In McKenzie County, North Dakota, USA, direct comparisons between polycrystalline diamond compact (PDC) bits with RDOCC and those with traditional DOCLs show a 39.5% reduction in hours or better to drill the curve section from 10,300 to 11,100 ft measured depth (MD) on the same pad site. The improved tool-face control allowed higher WOB application from a lower inclination through landing the curve, thereby improving ROP throughout the run. In the Wadi Rafash Field, northern Oman, a PDC bit with RDOCC drilled the curve section, improving dogleg severity (DLS) by 45%, ROP by 23% and reducing distance by 30% over the average offset performance in the field. The novelty of the RDOCC is the ability to absorb WOB fluctuations without creating large torque fluctuations that inhibit tool-face control. By maintaining a consistent tool face, operators and directional drillers can apply more energy to the system, resulting in overall higher ROP.

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