Abstract: Hardware, software and methods for controlling the usage of well drill bits and other aspects of well drilling plans. At least a portion of a given well is drilled with a given drill bit. An abrasive-wear-affecting variable (drilling strength) for the lithology which has been most recently drilled with the bit is continually evaluated. The current abrasive wear of the bit by the total lithology which has been drilled thereby is continually calculated, based on the abrasive-wear-affecting variable. Continued use or retirement of the bit is controlled in accord with the wear calculation. Relative pore pressure at the current site of the drill bit is a useful by product which can be independently used to control other aspects of the well drilling plan, e.g. mud weight and the setting of casing.

Abstract: The potential for failure of a formation is predicated by using standard logging apparatus and techniques to monitor the change in a formation characteristic over an extended time period. Changes in this characteristic are attributed to absorption of fluid by the formation which could lead to a possible breakdown of the structural integrity of the formation.