Patent ID: 8020632
Filing Date: 2011-09-20
Classification: E21B

Abstract:
1. A casing-while-drilling system that advances a bottom hole assembly having a drill bit into a subsurface formation along a wellbore that is at least partially cased, comprising: a modulator that generates mud pulses at a high frequency selected based on an inner diameter of the casing; a tool assembly configured for at least one of drilling measurements and formation measurements; and a mud motor that converts mud flow into rotation of the drill bit; wherein the modulator is positioned at a location uphole relative to the mud motor and the tool assembly is positioned at a location downhole relative to the mud motor; and wherein the modulator is in communication with the tool assembly despite the position of the mud motor therebetween; wherein a signal strength at a surface transducer is generated by the modulator according to a formula S=S