Sonic/acoustic monitoring using optical distributed acoustic sensing

Abstract

Methods and apparatus for performing sonic well logging within a wellbore based on optical Distributed Acoustic Sensing (DAS) are provided. A sonic well logging system based on DAS may be capable of producing the functional equivalent of tens, hundreds, or even thousands of acoustic sensors. In this manner, the emplacement of the sonic well logging system based on DAS may not be nearly as complex or expensive as emplacing a sonic well logging system based on traditional methods. Furthermore, multiplexing may be simpler, downhole electronics need not be used, and the sonic well logging system may be used in extreme, high temperature environments.

1 . An apparatus for performing sonic well logging in a wellbore, comprising:
 an acoustic energy source disposed between a casing disposed in the wellbore and a tubing disposed in the casing, wherein the acoustic energy source is configured to generate acoustic signals in the wellbore for interacting with at least one of the wellbore, a wellbore completion, and formations adjacent the wellbore to form transmitted, reflected, refracted, or absorbed acoustic signals; and   an optical waveguide for distributed acoustic sensing (DAS) disposed in the wellbore, wherein the transmitted, reflected, or refracted acoustic signals affect light propagating in the waveguide.   
     
     
         2 . The apparatus of  claim 1 , wherein at least one of the acoustic energy source and the waveguide is permanently emplaced in the wellbore. 
     
     
         3 . The apparatus of  claim 1 , wherein the acoustic energy source and the waveguide are suspended in a cable in the wellbore. 
     
     
         4 . The apparatus of  claim 1 , wherein the acoustic energy source and the waveguide are coupled to the tubing. 
     
     
         5 . The apparatus of  claim 1 , wherein the waveguide is disposed outside the casing disposed in the wellbore. 
     
     
         6 . The apparatus of  claim 1 , wherein the waveguide is disposed outside the casing disposed in the wellbore and wherein the acoustic energy source is coupled to the tubing disposed in the casing. 
     
     
         7 . The apparatus of  claim 1 , wherein the waveguide is coupled to an outer surface of the tubing. 
     
     
         8 . The apparatus of  claim 1 , wherein the waveguide is disposed outside the casing disposed in the wellbore and wherein the acoustic energy source is disposed in an annulus between the casing and the tubing. 
     
     
         9 . The apparatus of  claim 1 , wherein the waveguide is wrapped in a spiral manner around at least a portion of the tubing or the casing disposed in the wellbore. 
     
     
         10 . The apparatus of  claim 1 , wherein the waveguide is circularly wrapped around at least one circumference of the casing or the tubing. 
     
     
         11 . The apparatus of  claim 1 , further comprising an acoustic energy source controller configured to control the acoustic energy source. 
     
     
         12 . The apparatus of  claim 1 , further comprising a DAS instrument configured to introduce optical pulses into the waveguide and/or to sense disturbances in the optical pulses propagating in the waveguide. 
     
     
         13 . A method comprising:
 providing an acoustic energy source disposed between a casing disposed in a wellbore and a tubing disposed in the casing;   providing an optical waveguide in the wellbore; and   performing distributed acoustic sensing (DAS) in the wellbore using the acoustic energy source and the optical waveguide.   
     
     
         14 . The method of  claim 13 , wherein performing DAS comprises generating acoustic signals using the acoustic energy source, wherein the acoustic signals interact with at least one of the wellbore, a wellbore completion, and formations adjacent the wellbore to form transmitted, reflected, refracted, or absorbed acoustic signals and wherein the transmitted, reflected, or refracted acoustic signals affect light propagating in the waveguide. 
     
     
         15 . The method of  claim 13 , wherein performing DAS in the wellbore comprises performing sonic well logging. 
     
     
         16 . The method of  claim 15 , further comprising monitoring properties of downhole formations adjacent the wellbore over time based on the sonic well logging. 
     
     
         17 . The method of  claim 16 , further comprising controlling production or managing reservoirs based on the downhole formation properties. 
     
     
         18 . The method of  claim 13 , wherein at least one of the acoustic energy source and the waveguide is semi-permanently emplaced in the wellbore. 
     
     
         19 . The method of  claim 13 , wherein performing DAS comprises:
 introducing optical pulses into the waveguide; and   sensing disturbances in the optical pulses propagating through the waveguide.   
     
     
         20 . The method of  claim 13 , wherein the acoustic energy source is coupled to the tubing disposed in the casing. 
     
     
         21 . An apparatus for performing sonic well logging in a wellbore, comprising:
 an acoustic energy source disposed between an outer surface of a borehole casing located in the wellbore and an inner surface of the wellbore, wherein the acoustic energy source is configured to generate acoustic signals in the wellbore for interacting with at least one of the wellbore, a wellbore completion, and formations adjacent the wellbore to form transmitted, reflected, refracted, or absorbed acoustic signals; and   an optical waveguide for distributed acoustic sensing (DAS) disposed in the wellbore, wherein the transmitted, reflected, or refracted acoustic signals affect light propagating in the optical waveguide.   
     
     
         22 . A method comprising:
 providing an acoustic energy source disposed between an outer surface of a borehole casing located in a wellbore and an inner surface of the wellbore;   providing an optical waveguide disposed in the wellbore; and   performing distributed acoustic sensing (DAS) in the wellbore using the acoustic energy source and the optical waveguide.