Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Well logging
Patent
1989-06-15
1990-05-22
Tarcza, Thomas H.
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Well logging
181105, G01V 140
Patent
active
049282697
ABSTRACT:
The present invention is directed to a method of calculating the impedance of a material behind the section of a casing. An acoustic excitation pulse is directed towards a section of the casing, resulting in a return waveform having a reverberation segment and an initial reflection segment. The return waveform is analyzed to choose a resonance frequency indicative of the casing's nominal thickness. The return waveform is bandpass filtered about the chosen frequency. A time window of the reverberation segment is selected, and the energy content in the time window of the filtered reverberation segment is calculated. Both the bandpass filter and time windows are selected based on the chosen resonance frequency, thereby removing variations in the thickness of the casing. The energy content calculation produces a cementation signal indicative of the impedance of the cement behind the section of the casing. The impedance value is indicative of the cement quality. In accordance with another aspect, a time portion of the initial reflection segment is chosen, and the energy content in the time window of the filtered initial reflection segment is calculated. This energy is used to normalize the cementation signal calculated from the reverberation segment. In accordance with another aspect of the present invention, the impedance of the material behind the casing is determined.
REFERENCES:
patent: 3401772 (1968-09-01), Kokesh
patent: 3401773 (1968-09-01), Synnott, III
patent: 4255798 (1981-03-01), Havira
patent: 4703427 (1987-10-01), Catala et al.
patent: 4709357 (1987-11-01), Maki, Jr.
patent: 4733380 (1988-03-01), Havira
patent: 4757479 (1988-07-01), Masson et al.
Hayman Andrew J.
Kimball Christopher V.
Randall Curtis J.
Stanke Fred E.
Lobo Ian J.
Schlumberger Technology Corporation
Tager Clifford L.
Tarcza Thomas H.
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