| dc.description.abstract | Drilling the highly interbedded Brushy Canyon in the Delaware Basin can force operators to use over three PDC bits to drill a 12.25” intermediate hole. A study was conducted in order to develop understanding of the mechanics involved in specific bit failures that were occurring when drilling across high-strength laminations. It was found that upon exiting high-strength interbedded laminations, sudden high-torque events were occurring that were leading to tangential overload of the trim and gauge cutters. The change from high-strength to low-strength rock at the transition reduces the resistance on the nose of the bit abruptly, transferring the axial load to the trim and gauge cutters in the high-strength rock. The redistribution of axial load across the cutters results in an instantaneous net gain in torque that is great enough to overload one to two rows of outside cutters tangentially.
To combat this, a rate of penetration (ROP) setpoint and constant bit RPM were utilized when drilling the Brushy, allowing for the depth of cut per revolution (DOC) to be controlled, prevent damaging bit whirl in high-strength laminations, and reducing tangential overload tendency due to entering and exiting laminations. Performance was tracked using a simple DOC tracer alongside MSE which helped in distinguishing between bit dysfunction and damage. Additionally, an operational practice for using the DOC tracer when control drilling with an ROP setpoint was developed. | en |
