Maintaining Steerability While Extending Gauge Length To Manage Whirl Academic Article uri icon

abstract

  • This paper discusses the results of a global campaign to increase the length of the gauge area of bits used on rotary-steerable systems (RSSs) to mitigate bit whirl and its undesirable effects. The desired steerability was achieved with lengths in excess of 4 in. with all RSS tools used. The modifications have resulted in reduced vibrations, significant improvement in drill rate, improved borehole quality, and reduced tool damage. When the operator's performance-management process was implemented, real-time and post-drill analysis of mechanical specific energy (MSE) suggested 40% of footage drilled worldwide was affected by bit whirl or lateral instability. One element in the programmatic response was an initiative beginning in 2006 to extend bit-gauge lengths to constrain side cutting and reduce the amplitude of whirl-induced patterns. The value of extended gauge lengths has been demonstrated in numerous papers. However, field implementation by the industry has not been uniform, and a significant issue has been concern that steerability would be reduced. The purpose of the initiative was to demonstrate that common build rates could be achieved with all RSS tools used by the operator with bits having a minimum gauge length of 4 in. In the subject wells over a 2-year period, normal build rates (2-47100 ft) were not affected with 4-in. gauges if the profile and aggressiveness were designed properly. The gauge profiles used to maintain steerability included full taper, full undercut, and partial undercut. While the desired steerability was achieved with both point-the-bit and push-the-bit RSS tools, specific modification required in the gauge profile varied with the RSS used, desired build rate, and drilling environment. Drill-rate performance and bit life also improved, but this was attributed partly to implementation of the performance-management process and specific rig-crew training. Extension of the gauge length is also known to benefit bent-motor operations (Norris et al. 1998); however, the effects of various gauge profiles are less certain, and motor operations are not discussed in this paper. The objective was not to determine the maximum build rates achievable but to simply confirm that gauge lengths of 4 in. or greater could be used as standard practice in normal operations. This paper discusses the rationale for the use of extended gauges, the modified profiles used to maintain steerability with various RSS tools, and the field performance achieved. © 2010 Society of Petroleum Engineers.

author list (cited authors)

  • Dupriest, F. E., & Sowers, S. F.

citation count

  • 7

publication date

  • June 2010