Flow velocity and acoustic velocity measurement with distributed acoustic sensing

Abstract

A well flow velocity measurement method can include transmitting an acoustic signal through at least one fluid composition in a well, detecting velocities of the acoustic signal in both opposite directions along an optical waveguide in the well, the optical waveguide being included in a distributed acoustic sensing system, and determining an acoustic velocity in the fluid composition based on the velocities of the acoustic signal. Another well flow velocity measurement method can include propagating at least one pressure pulse through at least one fluid composition in a well, detecting a velocity of the pressure pulse along an optical waveguide in the well, the optical waveguide being included in a distributed acoustic sensing system, and determining an acoustic velocity in the fluid composition based on the velocity of the pressure pulse.

What is claimed is: 
     
         1 . A well flow velocity measurement method, comprising:
 transmitting an acoustic signal through at least one fluid composition in a well;   detecting velocities of the acoustic signal in both opposite directions along an optical waveguide in the well, the optical waveguide being included in a distributed acoustic sensing system; and   determining an acoustic velocity in the fluid composition based on the velocities of the acoustic signal.   
     
     
         2 . The method of  claim 1 , wherein the distributed acoustic sensing system detects coherent Rayleigh backscattering along the optical waveguide. 
     
     
         3 . The method of  claim 1 , wherein the transmitting further comprises propagating at least one pressure pulse through the fluid composition. 
     
     
         4 . The method of  claim 3 , wherein the detecting further comprises detecting at least one reflection of the pressure pulse. 
     
     
         5 . The method of  claim 1 , wherein the transmitting further comprises transmitting the acoustic signal through multiple fluid compositions in the well. 
     
     
         6 . The method of  claim 5 , wherein the determining further comprises determining the acoustic velocity in each of the multiple fluid compositions. 
     
     
         7 . The method of  claim 1 , wherein the distributed acoustic sensing system indicates acoustic energy along the optical waveguide. 
     
     
         8 . The method of  claim 1 , wherein the distributed acoustic sensing system includes an interrogator which detects coherent Rayleigh backscattering in the optical waveguide. 
     
     
         9 . The method of  claim 1 , wherein the transmitting further comprises generating the acoustic signal at a location between the earth's surface and a bottom of the well, the acoustic signal propagating in the opposite directions from the location. 
     
     
         10 . The method of  claim 1 , wherein the transmitting further comprises applying an impact to a tubular string. 
     
     
         11 . The method of  claim 1 , wherein determining the acoustic velocity in the fluid composition further comprises compensating for pipe compliance. 
     
     
         12 . A well flow velocity measurement system, comprising:
 a pressure pulse generator which propagates at least one pressure pulse through at least one fluid composition in a well; and   a distributed acoustic sensing system which detects coherent Rayleigh backscattering along an optical waveguide in the well, whereby a velocity of the pressure pulse in the well is determined.   
     
     
         13 . The system of  claim 12 , further comprising a computer which determines an acoustic velocity in the fluid composition based on the velocity of the pressure pulse. 
     
     
         14 . The system of  claim 12 , wherein the velocity of the pressure pulse in both opposite directions along the optical waveguide is determined. 
     
     
         15 . The system of  claim 12 , wherein the distributed acoustic sensing system detects at least one reflection of the pressure pulse. 
     
     
         16 . The system of  claim 12 , wherein the pressure pulse is propagated through multiple fluid compositions in the well. 
     
     
         17 . The system of  claim 16 , wherein an acoustic velocity in each of the multiple fluid compositions is determined. 
     
     
         18 . The system of  claim 12 , wherein the distributed acoustic sensing system indicates acoustic energy along the optical waveguide. 
     
     
         19 . The system of  claim 12 , wherein the pressure pulse generator applies an impact to a tubular string. 
     
     
         20 . The system of  claim 12 , wherein the pressure pulse generator propagates the pressure pulse in opposite directions from a location in the well. 
     
     
         21 . A well flow velocity measurement method, comprising:
 propagating at least one pressure pulse through at least one fluid composition in a well;   detecting a velocity of the pressure pulse along an optical waveguide in the well, the optical waveguide being included in a distributed acoustic sensing system; and   determining an acoustic velocity in the fluid composition based on the velocity of the pressure pulse.   
     
     
         22 . The method of  claim 21 , wherein the detecting further comprises detecting the velocity of the pressure pulse in both opposite directions along the optical waveguide. 
     
     
         23 . The method of  claim 21 , wherein the distributed acoustic sensing system detects coherent Rayleigh backscattering along the optical waveguide. 
     
     
         24 . The method of  claim 21 , wherein the detecting further comprises detecting at least one reflection of the pressure pulse. 
     
     
         25 . The method of  claim 21 , wherein the propagating further comprises propagating the pressure pulse through multiple fluid compositions in the well. 
     
     
         26 . The method of  claim 25 , wherein the determining further comprises determining the acoustic velocity in each of the multiple fluid compositions. 
     
     
         27 . The method of  claim 21 , wherein the distributed acoustic sensing system indicates acoustic energy along the optical waveguide. 
     
     
         28 . The method of  claim 21 , wherein the distributed acoustic sensing system includes an interrogator which detects coherent Rayleigh backscattering in the optical waveguide. 
     
     
         29 . The method of  claim 21 , wherein the propagating further comprises generating the acoustic signal at a location between the earth's surface and a bottom of the well, the acoustic signal propagating in opposite directions from the location. 
     
     
         30 . The method of  claim 21 , wherein the propagating further comprises applying an impact to a tubular string. 
     
     
         31 . The method of  claim 21 , wherein determining the acoustic velocity in the fluid composition further comprises compensating for pipe compliance.