Reference signal encoding for seismic while drilling measurement

A seismic-while-drilling method, comprising the steps of:

• (a.) in a downhole processor, analyzing the acoustic signal generated by an operating drill bit to derive data therefrom;
• (b.) transmitting said data to at least one processor located at or near the earth's surface;
• (c.) reconstructing a copy of said acoustic signal from said data;
• and
• (d.) using said copy as a reference signal to interpret acoustic information detected at positions separate from said drill bit.

A method of gathering geophysical information, comprising:

• drilling a well bore with a drill bit which produces seismic energy;
• in a down hole processor, analyzing a reference signal generated by said drill bit during continuing drilling operations to determine key characteristics of said reference signal;
• transmitting said key characteristic to the surface;
• obtaining a reconstructed reference signal at the surface based on said key characteristics;
• detecting a seismic signal at the surface;
• and
• correlating said seismic signal with said reconstructed reference signal to obtain information about subterranean geologic formations.

A method of gathering geophysical information comprising:

• creating a library of anticipated bit wavelets and storing said library in a downhole memory and in a surface memory;
• generating a reference signal downhole;
• analyzing said reference signal downhole to identify a code corresponding to a best matching wavelet from said library and a scale factor;
• transmitting said code and said scale factor to a surface location;
• obtaining a reconstructed reference signal at the surface location from said transmitted code and said scale factor using said surface memory;
• using said reconstructed reference signal to correlate a detected signal to determine geophysical information.

A system for seismic exploration comprising:

• a downhole processor that analyzes an acoustic signal generated by an operating drill bit to derive data therefrom;
• a second processor operatively connected to receive said data;
• and
• at least one acoustic detector remote from said downhole processor;
• wherein
• said second processor is remote from said downhole processor and uses said data to interpret acoustic information received by the at least one acoustic detector.