A New Method of Backup Cutter Layout to Extend Bit Life Without Sacrificing Rate of Penetration

摘要

This paper discusses a new and general method of backup cutter layout to extend bit life without sacrificing rate of penetration and two field case studies. This method includes the following aspects: 1. Ensuring backup cutters do not cut or only partially cut when their primary cutters experience little to no wear and when the depth of cut of the bit does not exceed an expected value. This aspect is enabled by allowing backup cutters to have a minimal critical depth of cut that is greater than the depth of cut of the primary cutters. 2. Ensuring backup cutters act as major cutters when the primary cutters' wear depth is equal to or greater than the underexposure of the backup cutters. This aspect is enabled by allowing each backup cutter be rotationally behind its primary cutter by approximately 180° or greater. The underexposure of each backup cutter relative to its primary cutter is carefully calculated based on the primary cutter's wear and drilling slope.