Method and apparatus for acoustically investigating a borehole c

Details Method and apparatus for acoustically investigating a borehole c Method and apparatus for acoustically investigating a borehole c

1985-08-14

1987-11-24

Tarcza, Thomas H.

Communications, electrical: acoustic wave systems and devices

Seismic prospecting

Well logging

367 45, 181105, G01U 100

Patent

active

047093579

ABSTRACT:
A method and apparatus are disclosed for acoustically investigating a borehole casing cement bond. A sonde is provided which is adapted to be lowered into a borehole and which includes a plurality of acoustic transducers arranged in a helical array around the sonde. A short duration acoustic pulse is directed at the borehole casing from each transducer and the reflection signal generated thereby is coupled to an autoregressive adaptive filter which automatically adjusts its filter coefficients to achieve a desired output signal. The adjusted filter coefficients are then utilized to determine the frequency and decay rate of the reflection signal and the frequency and decay rate of the reflection signal may be utilized to determine selected characteristics of the casing and the cement bond. In a preferred embodiment of the present invention, an additional transducer is mounted a selected distance from a fixed reflector to obtain standard transmission characteristics.

REFERENCES:
patent: 2648056 (1953-08-01), Jakosky
patent: 4255798 (1981-03-01), Havira
patent: 4403298 (1983-09-01), May, Jr.
patent: 4587641 (1986-05-01), DiFoggio
Feintuch et al, "Time Delay Estimation Using the LMS Adaptive Filter-Dynamic Behavior", IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. ASSP-29, No. 3, Jun. 1981, pp. 571-576.

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