Patent ID: 7270196
Filing Date: 2007-09-18
Classification: E21B

Abstract:
1. A drill bit assembly, comprising: a body portion intermediate a shank portion and a working portion, the shank portion being adapted for connection to a downhole tool string; the working portion comprising at least one cutting element fixed with respect to the body portion; the body portion comprising at least a portion of a reactive jackleg apparatus that is generally coaxial with the shank portion; the reactive jackleg apparatus comprising a chamber at least partially disposed within the body portion and a shaft movably disposed within the chamber, the shaft comprising an enlarged portion and a hard metal distal end; the chamber comprising an opening proximate the working portion, through which drilling mud from the bore and the distal end of the shaft exit the drill bit; and the enlarged portion of the shaft is in fluid communication with a bore formed in the tool string; wherein a position of the shaft is determined by at least a combination of a formation pressure and a fluid bore pressure generated by drilling mud; wherein the enlarged portion of the shaft engages a spring.