In-situ borehole fluid speed and attenuation measurement in an ultrasonic scanning tool
An example casing and cement evaluation tool may include a tool body and a rotating portion coupled to the tool body. A first transducer may be coupled to the rotating portion at a radial offset from a longitudinal axis of the tool. A second transducer may be coupled to the rotating portion at a different radial offset from the longitudinal axis of the tool.
1. A casing and cement evaluation tool, comprising:
a tool body;
a rotating portion coupled to the tool body;
a first transducer coupled to the rotating portion at a radial offset from a longitudinal axis of the tool and at a longitudinal position on the rotating portion of the tool body; and
a second transducer coupled to the rotating portion at a different radial offset from the longitudinal axis of the tool and at the same longitudinal position as the first transducer.
2. The casing and cement evaluation tool of claim 1 , wherein the first transducer and the second transducer are offset 180° with respect to the rotating portion.
3. The casing and cement evaluation tool of claim 1 , wherein the rotating portion comprises a rotating head positioned at a distal end of the tool body and rotated by a drive mechanism located within the tool body.
4. The casing and cement evaluation tool of claim 1 , further comprising a slip ring between the tool body and the rotating portion of the tool body.
5. The casing and cement evaluation tool of claim 1 , further comprising a field programmable gate array that controls, in part, the first transducer and the second transducer.
6. The casing and cement evaluation tool of claim 1 , further comprising an information handling system communicably coupled to the first and second transducers and configured to:
receive from the first transducer a first echo signal corresponding to a first acoustic pulse transmitted by the first transducer;
receive from the second transducer a second echo signal corresponding to a second acoustic pulse transmitted by the second transducer; and
determine a fluid speed of a borehole fluid in which the tool body is positioned based, at least in part, on the received first echo signal and the received second echo signal.
7. The casing and cement evaluation tool of claim 6 , wherein the information handling system is configured to determine the fluid speed of the borehole fluid based, at least in part, on the received first echo signal and the received second echo signal by performing the following steps:
determine a first arrival time associated with the first echo signal;
determine a second arrival time associated with the second echo signal; and
determine the fluid speed based, at least in part, on the first arrival time and the second arrival time.
8. The casing and cement evaluation tool of claim 7 , wherein the information handling system is configured to determine the fluid speed based, at least in part, on the first arrival time and the second arrival time using the following equations:
fluid
speed
=
2
(
ID
-
(
2
r
+
dr
)
)
t
1
+
t
2
(
1
)
fluid
speed
=
2
dr
t
1
+
t
2
(
2
)
wherein ID correspond to an inner diameter of a casing in which the tool body is positioned; t 1 corresponds to the first arrival time; t 2 corresponds to the second arrival time; r corresponds to the radial offset of the first transducer; and dr corresponds to the difference between the radial offset of the first transducer and the radial offset of the second transducer.
9. The casing and cement evaluation tool of claim 6 , wherein the information handling system is further configured to determine a frequency-based attenuation response of the borehole fluid based, at least in part, on the first echo signal and the second echo signal.
10. The casing and cement evaluation tool of claim 9 , wherein the information handling system is configured to determine the frequency-based attenuation response of the borehole fluid based, at least in part, on the first echo signal and the second echo signal by performing the following steps:
transform the first and second echo signals into the frequency domain;
respectively compare the transformed first and second echo signals to the frequency spectra of the first acoustic pulse and the second acoustic pulse.
11. A method, comprising:
transmitting a first acoustic pulse from a first transducer positioned within borehole fluid, wherein the first transducer is coupled to a rotating portion of a downhole tool at a radial offset from a longitudinal axis of the tool;
receiving at the first transducer a first echo signal corresponding to the first acoustic pulse;
transmitting a second acoustic pulse from a second transducer positioned within borehole fluid, wherein the second transducer is coupled to the rotating portion of the downhole tool at a different radial offset from a longitudinal axis of the tool;
receiving at the second transducer a second echo signal corresponding to the second acoustic pulse;
determining a frequency-based attenuation response of the borehole fluid based, at least in part, on the first echo signal and the second echo signal.
12. The method of claim 11 , wherein the first transducer and the second transducer are offset 180° with respect to the rotating portion.
13. The method of claim 11 , wherein the rotating portion comprises a rotating head positioned at a distal end of the tool body and rotated by a drive mechanism located within the tool body.
14. The method of claim 11 , further comprising determining a fluid speed of the borehole fluid based, at least in part, on the first echo signal and the second echo signal.
15. The method of claim 11 , wherein determining the frequency-based attenuation response of the borehole fluid based, at least in part, on the first echo signal and the second echo signal comprises transforming the first and second echo signals into the frequency domain; and respectively comparing the transformed first and second echo signals to the frequency spectra of the first acoustic pulse and the second acoustic pulse.
16. The method of claim 11 , wherein the tool comprises a slip ring between the tool body and the rotating portion of the tool body.
17. The method of claim 11 , wherein the tool comprises a field programmable gate array that controls, in part, the first transducer and the second transducer.
18. The method of claim 11 , further comprising determining a fluid speed based, at least in part, on the first echo signal and the second echo signal, wherein determining the fluid speed of the borehole fluid comprises
determining a first arrival time associated with the first echo signal;
determining a second arrival time associated with the second echo signal; and
determining the fluid speed based, at least in part, on the first arrival time and the second arrival time.
19. The method of claim 18 , wherein determining the fluid speed based, at least in part, on the first arrival time and the second arrival time comprises determining the fluid speed using the following equations:
fluid
speed
=
2
(
ID
-
(
2
r
+
dr
)
)
t
1
+
t
2
(
1
)
fluid
speed
=
2
dr
t
1
+
t
2
(
2
)
wherein ID correspond to an inner diameter of a casing in which the tool body is positioned; t 1 corresponds to the first arrival time; t 2 corresponds to the second arrival time; r corresponds to the radial offset of the first transducer; and dr corresponds to the difference between the radial offset of the first transducer and the radial offset of the second transducer.