Calibration of a well acoustic sensing system

Abstract

A method of calibrating a distributed acoustic sensing system can include receiving predetermined acoustic signals along acoustic sensors distributed proximate a well, and calibrating the system based on the received acoustic signals. A method of calibrating an optical distributed acoustic sensing system can include displacing an acoustic source along an optical waveguide positioned proximate a well, transmitting predetermined acoustic signals from the acoustic source, receiving the acoustic signals with the waveguide, and calibrating the system based on the received acoustic signals. A well system can include a distributed acoustic sensing system including an optical waveguide installed in a well, and a backscattered light detection and analysis device, and at least one acoustic source which transmits predetermined acoustic signals at spaced apart locations along the waveguide. The device compensates an output of the system based on the acoustic signals as received at the locations along the waveguide.

1 . A method of calibrating a distributed acoustic sensing system, the method comprising:
 receiving predetermined acoustic signals along multiple acoustic sensors distributed proximate a well; and   calibrating the distributed acoustic sensing system based on the received predetermined acoustic signals.   
     
     
         2 . The method of  claim 1 , further comprising displacing at least one acoustic source adjacent the acoustic sensors. 
     
     
         3 . The method of  claim 2 , wherein the displacing further comprises displacing the acoustic source through a wellbore. 
     
     
         4 . The method of  claim 2 , wherein the acoustic source transmits the predetermined acoustic signals at multiple locations along the acoustic sensors. 
     
     
         5 . The method of  claim 4 , wherein the acoustic source transmits the predetermined acoustic signals at different amplitudes at each of the multiple locations. 
     
     
         6 . The method of  claim 4 , wherein the acoustic source transmits the predetermined acoustic signals in synchrony with an interrogator. 
     
     
         7 . The method of  claim 6 , wherein the calibrating further comprises measuring a phase of the acoustic signal along the acoustic sensors. 
     
     
         8 . The method of  claim 1 , wherein the receiving further comprises determining a power of the acoustic signals as received along the acoustic sensors. 
     
     
         9 . The method of  claim 1 , wherein the receiving further comprises determining a power spectral density of the acoustic signals as received along the acoustic sensors. 
     
     
         10 . The method of  claim 1 , wherein the receiving further comprises determining an extent of the acoustic signals as received along the acoustic sensors. 
     
     
         11 . The method of  claim 1 , wherein the calibrating further comprises measuring an acoustic sensitivity along the acoustic sensors. 
     
     
         12 . The method of  claim 1 , further comprising transmitting the acoustic signals from another well. 
     
     
         13 . The method of  claim 1 , further comprising transmitting the acoustic signals from at or near the earth's surface. 
     
     
         14 . The method of  claim 1 , further comprising transmitting Stoneley waves from at or near a wellhead. 
     
     
         15 . The method of  claim 1 , further comprising transmitting Stoneley waves from a downhole location. 
     
     
         16 . The method of  claim 1 , wherein the receiving further comprises receiving the acoustic signals by a three-axis reference sensor positioned proximate the distributed acoustic sensors. 
     
     
         17 . The method of  claim 16 , wherein the calibrating further comprises calibrating the distributed acoustic sensing system based on the predetermined acoustic signals as detected by the three-axis reference sensor. 
     
     
         18 . The method of  claim 16 , wherein the three-axis reference sensor comprises a geophone. 
     
     
         19 . The method of  claim 1 , wherein the calibrating further comprises computing an acoustic point spread function along the sensors for each of multiple source locations. 
     
     
         20 . The method of  claim 19 , wherein the calibrating further comprises using the point spread function determined by the computing to deblur acoustic emissions along a wellbore as received by the distributed acoustic sensors. 
     
     
         21 . A method of calibrating an optical distributed acoustic sensing system, the method comprising:
 receiving predetermined acoustic signals along an optical waveguide positioned proximate a well; and   calibrating the optical distributed acoustic sensing system based on the received predetermined acoustic signals.   
     
     
         22 . The method of  claim 21 , further comprising displacing at least one acoustic source adjacent the optical waveguide. 
     
     
         23 . The method of  claim 22 , wherein the displacing further comprises displacing the acoustic source through a wellbore. 
     
     
         24 . The method of  claim 22 , wherein the acoustic source transmits the predetermined acoustic signals at multiple locations along the optical waveguide. 
     
     
         25 . The method of  claim 24 , wherein the acoustic source transmits the predetermined acoustic signals at different amplitudes at each of the multiple locations. 
     
     
         26 . The method of  claim 24 , wherein the acoustic source transmits the predetermined acoustic signals in synchrony with an interrogator. 
     
     
         27 . The method of  claim 26 , wherein the calibrating further comprises measuring a phase of the acoustic signals along the optical waveguide. 
     
     
         28 . The method of  claim 21 , wherein the receiving further comprises determining a power of the acoustic signals as received along the optical waveguide. 
     
     
         29 . The method of  claim 21 , wherein the receiving further comprises determining a power spectral density of the acoustic signals as received along the optical waveguide. 
     
     
         30 . The method of  claim 21 , wherein the receiving further comprises determining an extent of the acoustic signals as received along the optical waveguide. 
     
     
         31 . The method of  claim 21 , wherein the calibrating further comprises measuring an acoustic sensitivity along the optical waveguide. 
     
     
         32 . The method of  claim 21 , further comprising transmitting the acoustic signals from another well. 
     
     
         33 . The method of  claim 21 , further comprising transmitting the acoustic signals from at or near the earth's surface. 
     
     
         34 . The method of  claim 21 , further comprising transmitting Stoneley waves from at or near a wellhead. 
     
     
         35 . The method of  claim 21 , further comprising transmitting Stoneley waves from a downhole location. 
     
     
         36 . The method of  claim 21 , wherein the receiving further comprises receiving the acoustic signals by a three-axis reference sensor positioned proximate the optical waveguide. 
     
     
         37 . The method of  claim 36 , wherein the calibrating further comprises calibrating the optical distributed acoustic sensing system based on the predetermined acoustic signals as detected by the three-axis reference sensor. 
     
     
         38 . The method of  claim 36 , wherein the three-axis reference sensor comprises a geophone. 
     
     
         39 . The method of  claim 21 , wherein the calibrating further comprises computing an acoustic point spread function along the optical waveguide for each of multiple source locations. 
     
     
         40 . The method of  claim 39 , wherein the calibrating further comprises using the point spread function determined by the computing to deblur acoustic emissions along a wellbore as received by the optical waveguide. 
     
     
         41 . A method of calibrating an optical distributed acoustic sensing system, the method comprising:
 displacing at least one acoustic source along an optical waveguide positioned proximate a well;   transmitting predetermined acoustic signals from the acoustic source;   receiving the predetermined acoustic signals with the optical waveguide; and   calibrating the optical distributed acoustic sensing system based on the received predetermined acoustic signals.   
     
     
         42 . The method of  claim 41 , wherein the displacing further comprises displacing the acoustic source through a wellbore. 
     
     
         43 . The method of  claim 41 , wherein the acoustic source transmits the predetermined acoustic signals at multiple locations along the optical waveguide. 
     
     
         44 . The method of  claim 43 , wherein the acoustic source transmits the predetermined acoustic signals at different volumes at each of the multiple locations. 
     
     
         45 . The method of  claim 43 , wherein the acoustic source transmits the predetermined acoustic signals in synchrony with an interrogator. 
     
     
         46 . The method of  claim 45 , wherein the calibrating further comprises measuring a phase of the acoustic signals along the optical waveguide. 
     
     
         47 . The method of  claim 41 , wherein the receiving further comprises determining a power of the acoustic signals as received along the optical waveguide. 
     
     
         48 . The method of  claim 41 , wherein the receiving further comprises determining a power spectral density of the acoustic signals as received along the optical waveguide. 
     
     
         49 . The method of  claim 41 , wherein the receiving further comprises determining an extent of the acoustic signals as received along the optical waveguide. 
     
     
         50 . The method of  claim 41 , wherein the calibrating further comprises measuring an acoustic sensitivity along the optical waveguide. 
     
     
         51 . The method of  claim 41 , wherein the transmitting further comprises transmitting the acoustic signals from another well. 
     
     
         52 . The method of  claim 41 , wherein the transmitting further comprises transmitting the acoustic signals from at or near the earth's surface. 
     
     
         53 . The method of  claim 41 , wherein the transmitting further comprises transmitting Stoneley waves from at or near a wellhead. 
     
     
         54 . The method of  claim 41 , wherein the transmitting further comprises transmitting Stoneley waves from a downhole location. 
     
     
         55 . The method of  claim 41 , wherein the receiving further comprises receiving the acoustic signals by a three-axis reference sensor positioned proximate the optical waveguide. 
     
     
         56 . The method of  claim 55 , wherein the calibrating further comprises calibrating the optical distributed acoustic sensing system based on the predetermined acoustic signals as detected by the three-axis reference sensor. 
     
     
         57 . The method of  claim 55 , wherein the three-axis reference sensor comprises a geophone. 
     
     
         58 . The method of  claim 41 , wherein the calibrating further comprises computing an acoustic point spread function along the acoustic waveguide for each of multiple source locations. 
     
     
         59 . The method of  claim 58 , wherein the calibrating further comprises using the point spread function determined by the computing to deblur acoustic emissions along a wellbore as received by the optical waveguide. 
     
     
         60 . A well system, comprising:
 an optical distributed acoustic sensing system including an optical waveguide installed in a well, and a backscattered light detection and analysis device; and   at least one acoustic source which transmits predetermined acoustic signals at multiple spaced apart locations along the optical waveguide,   wherein the backscattered light detection and analysis device compensates an output of the optical distributed acoustic sensing system based on the predetermined acoustic signals as received at the spaced apart locations along the optical waveguide.   
     
     
         61 . The system of  claim 60 , wherein the acoustic source is displaced adjacent the optical waveguide. 
     
     
         62 . The system of  claim 60 , wherein the acoustic source is displaced through a wellbore. 
     
     
         63 . The system of  claim 60 , wherein the backscattered light detection and analysis device determines a power of the predetermined acoustic signals as received along the optical waveguide. 
     
     
         64 . The system of  claim 60 , wherein the acoustic source transmits the predetermined acoustic signals at different volumes at each of the multiple locations. 
     
     
         65 . The system of  claim 60 , wherein the acoustic source transmits the predetermined acoustic signals in synchrony with an interrogator. 
     
     
         66 . The system of  claim 65 , wherein the backscattered light detection and analysis device measures a phase of the acoustic signals along the optical waveguide. 
     
     
         67 . The system of  claim 60 , wherein the backscattered light detection and analysis device determines a power spectral density of the acoustic signals as received along the optical waveguide. 
     
     
         68 . The system of  claim 60 , wherein the backscattered light detection and analysis device determines an extent of the acoustic signals as received along the optical waveguide. 
     
     
         69 . The system of  claim 60 , wherein the backscattered light detection and analysis device measures an acoustic sensitivity along the optical waveguide. 
     
     
         70 . The system of  claim 60 , wherein the acoustic signals comprise Stoneley waves. 
     
     
         71 . The system of  claim 60 , wherein the acoustic signals are received by a three-axis reference sensor positioned proximate the optical waveguide. 
     
     
         72 . The system of  claim 71 , wherein the backscattered light detection and analysis device compensates the output of the optical distributed acoustic sensing system based on the predetermined acoustic signals as detected by the three-axis reference sensor. 
     
     
         73 . The system of  claim 71 , wherein the three-axis reference sensor comprises a geophone. 
     
     
         74 . A method of calibrating a distributed acoustic sensing system, the method comprising:
 receiving predetermined acoustic signals along multiple acoustic sensors distributed proximate a well; and   computing an acoustic point spread function along the sensors for each of multiple source locations.   
     
     
         75 . The method of  claim 74 , further comprising, using the point spread function determined by the computing to deblur acoustic emissions along a wellbore as received by the distributed acoustic sensors.