Wireless acoustic communications method and apparatus

Abstract

A method and apparatus for generating, propagating, encoding, decoding, modulating and detecting acoustic signals in a well borehole that comprises a signal generator ( 10 ) located at a first location for generating an acoustic source signal; a medium for the propagation the acoustic source signal to a second location and the propagation of the reflections and partial reflections of acoustic signals as it propagates through the medium; an apparatus to remove a detectable amount of energy from propagated acoustic signals; a controllable signal modulator ( 11 ) for attenuating the transmitted acoustic source signal; and a receiver ( 12 ) for receiving the modulated acoustic signals reflected, partially reflected or both by at least one reflector respectively located at one or more other locations.

1 . A communication system for a well borehole, the system comprising: a controllable signal modulator for damping an acoustic signal in the well thereby removing a detectable amount of energy from the acoustic signal;
 a receiver for receiving the damped acoustic signal and detecting the amount of removed energy; and   an acoustic propagation medium for propagating the acoustic signal, modulated by a controllable signal modulator located at a first location, to a second location; wherein the receiver is arranged to detect the acoustic signal,   and wherein the controllable signal modulator comprises a plurality of conductive coils moveable relative to a plurality of magnets.   
     
     
         2 . A system according to  claim 1 , the system further comprising:
 a signal generator located at a third location for generating an acoustic source signal.   
     
     
         3 . A system according to  claim 1 , wherein the acoustic propagation medium comprises a pipe disposed in the borehole. 
     
     
         4 . A system according to  claim 2 , wherein the third location is a location at the top of the borehole. 
     
     
         5 . A system according to any of  claim 1 , wherein the first location is within the borehole. 
     
     
         6 . A system according to  claim 5 , wherein the first location is at the end of a pipe disposed in the borehole or at a pipe joint. 
     
     
         7 . A system according to  claim 1 , wherein the receiver is located at the first location. 
     
     
         8 .- 9 . (canceled) 
     
     
         10 . A system according to  claim 1 , wherein the conductive coils and the magnets are coupled to a pipe. 
     
     
         11 . A system according to claim  9 ,  claim 7 , wherein the magnets have poles arranged symmetrically along the axis of the borehole. 
     
     
         12 . A system according to  claim 1 , wherein the magnets are aligned with the conductive coils such that, in use, magnetic flux through the coil is optimised. 
     
     
         13 . A system according to  claim 1 , wherein the conductive coils are selectively connected to vary the amount of damping. 
     
     
         14 . A system according to  claim 1 , wherein the controllable signal modulator is located within a pipe. 
     
     
         15 . A system according to  claim 1 , wherein the acoustic signal is transmitted at two or more frequencies. 
     
     
         16 . A system according to  claim 1 , wherein the acoustic signal is continuous. 
     
     
         17 . A method of communicating in a well borehole, the method comprising the steps of:
 damping an acoustic signal in the borehole thereby removing a detectable amount of energy from the propagated acoustic signal in the well;   receiving the damped acoustic signal to detect the amount of removed energy; and   propagating the acoustic signal from a first location, wherein the signal modulator modulates the acoustic signal, to a second location, wherein the receiver is arranged to detect the acoustic signal, and wherein the controllable signal modulator comprises a plurality of conductive coils moveable relative to a plurality of magnets.   
     
     
         18 . A method according to  claim 17 , the method further comprising the steps of:
 generating at a third location an acoustic source signal.   
     
     
         19 . A method according to  claim 17 , wherein the acoustic propagation medium comprises a pipe disposed in the borehole. 
     
     
         20 . A method according to  claim 18 , wherein the third location is a location at the top of the borehole. 
     
     
         21 . A method according to  claim 17 , wherein the first location is within the borehole. 
     
     
         22 . A method according to  claim 17 , wherein the first location is at the end of a pipe disposed in the borehole or at a pipe joint. 
     
     
         23 . A method according to  claim 17 , wherein the receiver is located at the first location. 
     
     
         24 .- 25 . (canceled) 
     
     
         26 . A method according to  claim 17 , wherein the conductive coils and the magnets are coupled to a pipe. 
     
     
         27 .- 32 . (canceled)