Apparatus and Method for Detecting Fluid Entering a Wellbore

Abstract

The method and apparatus of the present invention provides for detecting a flow of a formation fluid entering into a wellbore. An ultrasonic sensor is placed in a wellbore. The sensor has a resonant member that is exposed to a fluid in the wellbore. At a location in the wellbore, acoustic energy is measured wherein the acoustic energy is related to turbulence from formation fluid entering the wellbore. In another embodiment of the invention a tool is provided for detecting a flow of a formation fluid into a downhole location in a wellbore. The ultrasonic sensor has a resonant member that is adapted to be in contact with a fluid in the wellbore. The sensor generates electrical signals when exposed to ultrasonic turbulences caused by a formation fluid entering into the wellbore. A processor processes the electrical signals to detect the flow of the formation fluid entering into the wellbore.

1 . (canceled) 
   
   
       2 . An acoustic sensor comprising:
 a resonant member having a first side exposed to an outside environment; and   a cavity configured to enclose a second side of the resonant member and to house a liquid therein to provide pressure compensation for the resonant member.   
   
   
       3 . The acoustic sensor of  claim 1 , wherein the resonant member comprises a membrane coupled to a piezoelectric element. 
   
   
       4 . The acoustic sensor of  claim 3 , wherein the first side of the resonant member is a first side of the membrane and the piezoelectric element is coupled to a second side of the membrane. 
   
   
       5 . The acoustic sensor of  claim 4 , wherein the membrane is made at least in part from a metallic element. 
   
   
       6 . The acoustic sensor of  claim 3  further comprising an electrode coupled to the piezoelectric element configured to provide a signal when the membrane is exposed to pressure vibrations. 
   
   
       7 . The acoustic sensor of  claim 1  further comprising a fastener configured to fasten the acoustic sensor into a tool housing. 
   
   
       8 . An apparatus, comprising:
 a housing configured for use in a wellbore;   an acoustic sensor placed in the housing, the acoustic sensor comprising:
 a resonant member having a first side exposed to an outside environment, and 
 a pressure compensating device in fluid communication with a second side of the resonant member configured to provide pressure compensation for the resonant member. 
   
   
   
       9 . The apparatus of  claim 8 , wherein the pressure compensating device comprises:
 a fluid reservoir in fluid communication with a flexible member on a first end thereof and the second side of the resonant member on a second end thereof.   
   
   
       10 . The apparatus of  claim 9 , wherein the fluid reservoir is sealed and filled with a fluid that provides the pressure compensation to the resonant member. 
   
   
       11 . The apparatus of  claim 8 , wherein the resonant member includes a metallic member and a piezoelectric element. 
   
   
       12 . The apparatus of  claim 11  further comprising an electrical connection coupled to the resonant member configured to receive signals therefrom in response to applied pressure on the resonant member. 
   
   
       13 . The apparatus of  claim 12  further comprising a processor configured to process the signals received from the resonant member. 
   
   
       14 . The apparatus of  claim 13  comprising a conveying member configured to convey the housing into the wellbore. 
   
   
       15 . The apparatus of  claim 14 , wherein the processor is located at one of: (i) in the housing; and (ii) at a surface location configured to receive information relating to the signals from the acoustic sensor via a communication associated with the conveying member.