Variable throat venturi flow meter having a plurality of section-varying elements

1. An acoustic transceiver assembly comprising:

a housing having at least one inner wall defining a cavity, the cavity having a first end and a second end defining an axis of the acoustic transceiver assembly;

an oscillator provided in the cavity, the oscillator comprising:

a transducer element positioned at the first end of the cavity,

a backing mass positioned adjacent the transducer element, wherein the transducer element is disposed between the backing mass and the first end of the cavity;

a blocking element positioned adjacent the oscillator in the cavity, the blocking element being adapted to restrain a portion of the backing mass from lateral movement relative to the axis of the acoustic transceiver assembly, and to permit oscillations of the backing mass, wherein the blocking element restrains the backing mass at a first pressure and releases the backing mass at a second pressure to permit oscillations of the backing mass;

at least one blocking spring biased against the blocking element; and

an equalizing chamber having a port hole open to receiving the first pressure and/or the second pressure.

2. The acoustic transceiver assembly of claim 1 , further comprising at least one seal for sealing off the equalizing chamber.

3. The acoustic transceiver assembly of claim 1 , wherein the second pressure is higher than the first pressure.

4. The acoustic transceiver assembly of claim 1 , wherein the first pressure is atmospheric pressure, and the second pressure is hydrostatic pressure.

5. The acoustic transceiver assembly of claim 1 , wherein the blocking element is conical.

6. An acoustic transceiver assembly comprising:

a housing having at least one inner wall defining a cavity, the cavity having a first end and a second end defining an axis of the acoustic transceiver assembly;

an oscillator provided in the cavity, the oscillator comprising:

a transducer element positioned at the first end of the cavity,

a backing mass positioned adjacent the transducer element, wherein the transducer element is disposed between the backing mass and the first end of the cavity;

a blocking element positioned adjacent the oscillator in the cavity, the blocking element being adapted to restrain a portion of the backing mass from lateral movement relative to the axis of the acoustic transceiver assembly, and to permit oscillations of the backing mass; and

at least one preloading spring having a first end coupled to the backing mass and a second end coupled to the first end of the cavity.

7. A downhole tool comprising:

a sensor for monitoring a downhole parameter; and

an acoustic transceiver assembly in communication with the sensor, the acoustic transceiver assembly comprising:

a housing having at least one inner wall defining a cavity, the cavity having a first end and a second end defining an axis of the acoustic transceiver assembly;

an oscillator provided in the cavity, the oscillator comprising:

a transducer element positioned at the first end of the cavity,

a backing mass positioned adjacent the transducer element, and

wherein the transducer element is disposed between the backing mass and the first end of the cavity; and

a blocking element positioned adjacent the oscillator in the cavity, the blocking element being adapted to restrain a portion of the backing mass from lateral movement relative to the axis of the acoustic transceiver assembly, and to permit oscillations of the backing mass, wherein the blocking element restrains the backing mass at a first pressure and releases the backing mass at a second pressure to permit oscillations of the backing mass;

at least one blocking spring biased against the blocking element; and

an equalizing chamber having a port hole open to receiving the first pressure and/or the second pressure.

8. The downhole tool of claim 7 , wherein the acoustic transceiver assembly further comprises at least one seal for sealing off the equalizing chamber.

9. The downhole tool of claim 7 , wherein the second pressure is higher than the first pressure.

10. The downhole tool of claim 7 , wherein the first pressure is atmospheric pressure, and the second pressure is hydrostatic pressure.

11. The downhole tool of claim 7 , wherein the blocking element of the acoustic transceiver assembly is conical.

12. A downhole tool comprising:

a sensor for monitoring a downhole parameter; and

an acoustic transceiver assembly in communication with the sensor, the acoustic transceiver assembly comprising:

a housing having at least one inner wall defining a cavity, the cavity having a first end and a second end defining an axis of the acoustic transceiver assembly;

an oscillator provided in the cavity, the oscillator comprising:

a transducer element positioned at the first end of the cavity,

a backing mass positioned adjacent the transducer element, wherein the transducer element is disposed between the backing mass and the first end of the cavity;

a blocking element positioned adjacent the oscillator in the cavity, the blocking element being adapted to restrain a portion of the backing mass from lateral movement relative to the axis of the acoustic transceiver assembly, and to permit oscillations of the backing mass; and

at least one preloading spring having a first end coupled to the backing mass and a second end coupled to the first end of the cavity.

13. An acoustic transceiver assembly comprising:

a housing having at least one inner wall defining a cavity, the cavity having a first end and a second end defining an axis of the acoustic transceiver assembly;

an oscillator provided in the cavity, the oscillator comprising:

a piezoelectric element positioned at the first end of the cavity,

a backing mass positioned adjacent the piezoelectric element, and

wherein the piezoelectric element is disposed between the backing mass and the first end of the cavity;

a blocking element positioned adjacent the oscillator in the cavity, the blocking element being adapted to restrain a portion of the backing mass from lateral movement relative to the axis of the acoustic transceiver assembly, and to permit oscillations of the backing mass, wherein the blocking element restrains the backing mass at a first pressure and releases the backing mass at a second pressure to permit oscillations of the backing mass

at least one blocking spring biased against the blocking element; and

an equalizing chamber having a port hole open to receiving the first pressure and/or the second pressure.

14. The acoustic transceiver assembly of claim 13 , further comprising at least one seal for sealing off the equalizing chamber.

15. The acoustic transceiver assembly of claim 13 , wherein the second pressure is higher than the first pressure.

16. The acoustic transceiver assembly of claim 13 , wherein the first pressure is atmospheric pressure, and the second pressure is hydrostatic pressure.

17. The acoustic transceiver assembly of claim 13 , wherein the blocking element is conical.

18. An acoustic transceiver assembly comprising:

a housing having at least one inner wall defining a cavity, the cavity having a first end and a second end defining an axis of the acoustic transceiver assembly;

an oscillator provided in the cavity, the oscillator comprising:

a piezoelectric element positioned at the first end of the cavity,

a backing mass positioned adjacent the piezoelectric element, and

wherein the piezoelectric element is disposed between the backing mass and the first end of the cavity;

a blocking element positioned adjacent the oscillator in the cavity, the blocking element being adapted to restrain a portion of the backing mass from lateral movement relative to the axis of the acoustic transceiver assembly, and to permit oscillations of the backing mass; and

at least one preloading spring having a first end coupled to the backing mass and a second end coupled to the first end of the cavity.

19. A method for making an acoustic transceiver assembly for introducing acoustic signals into an elastic media positioned in a well bore, comprising the steps of:

forming an oscillator by acoustically coupling a backing mass to a transducer element;

suspending the oscillator in a housing with a blocking element positioned adjacent to the backing mass, wherein the blocking element restrains the backing mass at a first pressure and releases the backing mass at a second pressure;

forming an equalizing chamber between the blocking element and the housing; and

forming at least one port hole in the equalizing chamber and through the housing, wherein the at least one port hole is adapted to receive the first and/or second pressures.

20. The method of claim 19 further including the step of forming at least one seal for sealing off the equalizing chamber.

21. The method of claim 19 wherein the blocking element is conical.