Optimization of rock-bit life based on bearing failure criteria

Recent advances in rock-bit seal technology have allowed greater predictability of bearing life. Cone loss following bearing failure incurs costs related to remedial activities. A risk analysis approach, incorporating bearing-life relationships and the interdependence of drilling events, is used to formulate a bit-run cost-optimization method. The procedure enables a choice to be made between elastomeric and metal seals on a lowest-replacement-cost basis. The technique also provides a formal method for assessing the opportunity cost for using a device to detect bit-bearing failures downhole